Seismic Design of RC Structures Using UBC_ACI Provisions

Ports, Customs & Free Zone Corporation TRAKHEES ‐ ‐ تــــراخيص مؤسســة الموانــئ و الجمارك والمنطقــة الحــرة

Seismic Design of RC Structures Using

UBC / ACI Provisions

By Dr. S. K. Ghosh

Organised by

TRAKHEES

CIVIL ENGINEERING DEPARTMENT – WHITBY & BIRD

Dubai – November 2008

1. AN OVERVIEW OF CODES AND STANDARDS

2. COMPUTATION OF GRAVITY LOAD EFFECTS AND

DESIGN LOAD COMBINATIONS

3. COMPUTATION OF DESIGN WIND FORCES

4. AN OVERVIEW OF THE DESIGN LOAD COMBINATIONS AND THE SEISMIC DESIGN PROVISIONS OF THE 1997 UBC

5. EASY, STEP-BY-STEP DETERMINATION OF DESIGN BASE

SHEAR

6. 1997 UBC COMPUTATION OF DESIGN SEISMIC FORCES

7. SEISMIC DETAILS FOR REINFORCED CONCRETE BUILDINGS IN MODERATE SEISMIC APPLICATIONS

8. DESIGN OF TYPICAL STRUCTURAL MEMBERS

9. CODE SUPPORT SERVICES, CODE CHANGE PROCESS,

AND PLAN REVIEW

10. OVERVIEW OF THE SEISMIC DESIGN PROVISIONS OF THE 2006 INTERNATIONAL BUILDING CODE

11. DESIGN OF REINFORCED CONCRETE BUILDINGS UNDER

THE 1997 UBC

12. EARTHQUAKE DESIGN - EXAMPLE

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1

S. K. Ghosh Associates, Inc.

www.skghoshassociates.com

AN OVERVIEW OF CODES AND STANDARDS

S. K. Ghosh Associates Inc.Palatine, IL


CONSTRUCTION PERMIT

Plans and Specs approved for code compliance?

Permit issued

Redesign and resubmit

Appeal

No

Yes

Win

Lose

Application for permit for proposed construction

2

2



CERTIFICATE OF OCCUPANCY

Construction inspections approved for code

compliance?

Certificate of occupancy issued

Reconstruct and correct

Appeal

No

YesWin

Lose

BUILDING CODE - AUTHORITY

• State legislature has sole authority to enact and enforce building codes.

• State may choose to delegate a portion of this power to constituent local government units, such as cities.

3

3



BUILDING CODE

• Enacted by a state or local government’s legislative body to regulate construction within its jurisdiction.

• Minimum acceptable requirements necessary to preserve public health, safety, and welfare in the built environment.

• Primary application to new or proposed construction.

APPLICABILITY OF STATEWIDE BUILDING CODE

• Buildings based on construction methods such as factory-manufactured buildings,

• All construction except single-family dwellings,

• A single or narrow aspect of building construction such as fire safety,

• All construction.

4

4



ADMINISTRATION AND ENFORCEMENT

• Local government responsibility, subject to varying degrees of state agency supervision and oversight.

MODEL BUILDING CODES

• State and local governments adopt model building codes, rather than relying on custom-drafted building codes.

5

5



MODEL CODES

• Originally promulgated by:

the National Board of Fire Underwriters, later to become American Insurance Association

• New editions at approximately 10-year intervals.

• Withdrawn in 1984.

MODEL CODES AND THEIR AREAS OF INFLUENCE

LocallyWritten Code

UBC BOCA

StandardUBC &Standard

6

6



MODEL CODES

• A new edition every three years, with annual supplements.

• Annual code change cycle.

A REBIRTH OF THE MODEL BUILDING CODE SYSTEM IN THE UNITED STATES

The International Code Council:

7

7



FORMATION OF ORGANIZATIONS

Model Code Organizations:

• BOCA – 1915

• CABO – 1972

• ICBO – 1923

• ICC – 1994

• SBCCI - 1940

INTERNATIONAL CODE COUNCIL

• The International Code Council (ICC) was formed in December 1994 with the purpose of developing a single set of comprehensive and technical codes.

• The International Codes provide a complete set of construction codes without regional limitations.

8

8



IBC 2006

9

9



NFPA 5000 BUILDING CODE

from

National Fire Protection Association

Quincy, MA

First (2003) Edition Published in 2002

NFPA 5000

10

10




National Standards:

• ACI - 1905

• AFPA - 1993 (NFoPA 1902)

• ASCE - 1892

• ANSI - 1918

• ASHRAE - 1895

• ASTM - 1898


National Standards:

• AWS - 1919

• Factory Mutual - 1835

• Gypsum Asscn. - 1930

• NFPA - 1896

• UL - 1894

11

11



ASCE 7

ACI 318

12

12



STANDARDS

• Standards reference other standards. For instance, ACI 318 references a whole host of ASTM standards.

RESOURCE DOCUMENTS

13

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ICC EVALUATION SERVICE

A nonprofit, public-benefit corporation, ICC-ES does technical evaluations of building products, components, methods, and materials.

The evaluation process culminates with the issuance of reports on code compliance, which are made available free of charge to code officials, contractors, specifiers, architects, engineers, and anyone else with an interest in the building industry and construction.

ICC-ES evaluation reports provide evidence that products and systems meet code requirements.

For more information…


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1

S. K. Ghosh Associates Inc.


Computation of Gravity Load Effects and Design Load

Combinations


Palatine, IL


Dead Loads

• 1997 UBC Section 1606 – Movable

partition loads of 0.96 kN/m2 included

in dead loads for floors in office

buildings

15

2



Live Loads

• 1997 UBC Section 1607Table 16-A: Uniform and Concentrated LoadsTable 16-B: Special LoadsTable 16-C: Minimum Roof Live Loads

UBC 1607.5 Reduction of Live Loads

• Applies to live loads set forth in Table 16-A for floors and Table 16-C, Method 2, for roofs

1. Reduction not permitted in Group A (assembly) occupancies

2. Reduction not permitted when live load exceeds 4.79 kN/m2, except design live load from storage for columns may be reduced by 20%

16

3




• Applies to live loads set forth in Table 16-A for floors and Table 16-C, Method 2, for roofs3. The live load reduction shall not

exceed 40 percent in garages for the storage of private pleasure cars having a capacity of not more than nine passengers per vehicle


For live loads not exceeding 100 psf, design live loads for any member supporting 13.94 m2 or more may be reduced by

R (%) = r (A − 13.64)where r = 0.861 percent for floors, given in Table

16-C for roofs

Such reduction shall not exceed 40% for horizontal members, 60% for vertical members, nor R (%) = 23.1 (1 + D/Lo)

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4



Floor Live Load Reduction

18.6 55.8 74.4 93.037.2

100

60

40

Floor Members

Tributary Area, A, m2

Per

cent

of L

ive

Load

UBC 1607.6 Alternate Floor Live Load Reduction

• ASCE 7For KLL AT > 37.16 m2

L shall not be less than 0.50Lo for members supporting one floor nor than 0.40Lo for members supporting two or more floors

⎟⎟⎠

⎞⎜⎜⎝

⎛+=

TLL0 AK

57.40.25LL

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5



Influence Areas

Interior supporting member

Edge supporting member

Corner supporting member

Influence and Tributary Areas

Limits of Influence Area

Limits of Tributary Area

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6



Live Load Element Factor, KLL

1

All other members not identified above including:

- Edge beams with cantilever slabs

- Cantilever beams

- Two-way slabs

- Members without provisions for continuous shear transfer

normal to their span

2

2

2

Corner columns with cantilever slabs

Edge beams without cantilever slabs

Interior beams

3Edge columns with cantilever slabs

4

4

Interior Columns

Exterior columns without cantilever slabs

KLLElement

Limitations on Live Load Reductions

• ASCE 7-054.8.2 – Live loads that exceed 4.79 kN/m2 shall not

be reduced, except live loads for members supporting two or more floors may be reduced by 20%

4.8.3 – Live loads shall not be reduced in passenger car garages, except live loads for members supporting two or more floors may be reduced by 20%

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7



Limitations on Live Load Reductions

• ASCE 7-05

4.8.4 – Live loads of 4.79 kN/m2 or less shall not be

reduced in public assembly occupancies

4.8.5 – Live loads shall not be reduced for one-way

slabs except as permitted in 4.8.2. Live loads of

4.79 kN/m2 or less shall not be reduced for roof

members except as specified in 4.9

Snow Loads

• UBC left it to local jurisdictions

(sections 1908, 1914)

• ASCE 7 has detailed provisions

• Of little interest in Dubai

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Wind Loads

• 1997 UBC Section 1609. Refers to

Sections 1615 – 1625.

• Simplified version of wind design

provisions from ASCE 7-88

• Wind design in Dubai by ASCE 7-05

Typical Plan of Example Building

A

B

C

D

1 2 3 4 5 6

N

7 87.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m

6.71

m6.

71 m

6.71

m

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9



Typical Elevation of Example Building

11@

3.66

m=

40.2

6 m

10

11

12

7

8

9

4

5

6

1

2

3

4.88

m

Design Data

• Building Location Dubai, UAE

• Material PropertiesConcrete: fc

’ = 30 N/mm2, wc = 23.55 kN/m3

Reinforcement: fy = 415 N/mm2

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Design Data• Service Loads

Live loads: roof = 957.6 N/m2

floor = 2394 N/m2

Superimposed dead loads:

roof = 478.8 N/m2 + 889.64 kN for penthouse

floor = 1436.4 N/m2 (957.6 N/m2 permanent partitions + 478.8 N/m2 ceiling, etc.)

Design Data

• Member Dimensions

Slab: 205 mm

Beams: 560 × 560 mm

Interior columns: 660 × 660 mm

Edge columns: 610 × 610 mm

Wall thickness: 305 mm

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11



Beam C4 – C5

Tributary area = 2 ×(0.5 × 3.35 × 3.35 × 2 + 1.22 × 3.35) = 30.62 m2

C

54

7.92 m

6.71 m

3.35m 1.22 m

3.35m

3.35m

6.71 m

Beam C4 – C5

• Dead load:Beam self weight:

23.55 × 0.560 × 0.355 = 4.68 kN/m

Slab self weight within the tributary area: 23.55 × 0.205 = 4.78 kN/m2

4.78 × 30.62 m2 = 146.39 kN146.39 KN / 7.92 m = 18.48 kN/m

Superimposed dead load:1436.4 N/m2 × 30.62 m2 × 1/1000 = 43.98 kN43.98 KN / 7.92 m = 5.55 kN/m

wD = 4.68 + 18.48 + 5.55 = 28.71 kN/m

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12



Beam C4 – C5Bending moments and shear forces:

From ACI 318 Section 8.3.3:

Negative moment at the supports:

(wD × ln2) / 11 = (28.71 × 7.262) / 11 = 137.63 m-kN

Positive moment at midspan:

(wD × ln2) / 16 = (28.71 × 7.262) / 16 = 94.62 m-kN

Shear force = (wD × ln) / 2 = (28.71 × 7.26) / 2

= 104.27 kN

ln is clear span length (7.92 × 1000– 660 = 7260 mm = 7.26 m)

Beam C4 – C5

• Live load:

Lo = 2.394 kN/m2

kLL = 2, AT = 30.62 m2 kLLAT = 61.24 m2 > 37.16 m2

Therefore, live load reduction is permitted.L = Lo (0.25 + 4.57 / (61.24)0.5 ) = 2.394 × 0.834

= 1.997 kN/m2 > 0.5 Lo

wL = (1.997 × 30.62) / 7.92 = 7.721 kN/m

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13



Beam C4 – C5Bending moments and shear forces:

From ACI 318 Section 8.3.3:

Negative moment at the supports:

(wL × ln2) / 11 = (7.721 × 7.262) / 11 = 37.0 m-kN

Positive moment at midspan:

(wL × ln2) / 16 = (7.721 × 7.262) / 16 = 25.43 m-kN

Shear force = (wL × ln) / 2 = (7.721 × 7.26) / 2

= 28.03 kN

ln is clear span length (7.92 ×1000 – 660 = 7260 mm = 7.26 m)

Beam C4 – C5Summary of Design Bending Moments and Shear Forces for

Beam C4-C5 at the Second Floor Level

Live (L)

Dead (D)

Load Case

25.4Midspan28.0 –37.0Support

94.6Midspan104.3–137.6 Support

Shear Force (kN)

Bending Moment (m-kN)

Location

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1612.2.1 Strength Design or LRFD Load Combinations (1997 UBC)

1.4D (Equation 12-1) 1.2D + 1.6L + 0.5(Lr or S) (Equation 12-2)1.2D +1.6(Lr or S) + (f1L or 0.8W) (Equation 12-3) 1.2D + 1.3W + f1L + 0.5(Lr or S) (Equation 12-4) 1.2D + 1.0E + (f1L + f2S) (Equation 12-5) 0.9D ± (1.0E or 1.3W) (Equation 12-6)

f1 = 0.5 except in special circumstancesf2 = 0.2 except in special situations

Note exceptions for concrete structures

1612.2.2 Other Loads. Where F, H, P or

T are to be considered in design, each

applicable load shall be added to the

above load combinations factored as

follows: 1.3F, 1.6H, 1.2P and 1.2T


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2.3.2 Strength Design or LRFD Load Combinations

(ASCE 7-05)1. 1.4(D + F)

2. 1.2(D + F + T) +1.6(L + H) + 0.5(Lr or S or R)

3. 1.2D +1.6(Lr or S or R) + (L or 0.8W)

4. 1.2D + 1.6W + [1.0]L + 0.5(Lr or S or R)

5. 1.2D + 1.0E + L + 0.2S

6. 0.9D + 1.6W + 1.6H

7. 0.9D + 1.0E + 1.6H

2.3.2 Strength Design or LRFD Load Combinations (ASCE 7-05)

Exceptions:

• Now: Identify directionality effect explicitly in Kd. Round load factor from 1.53 to 1.6.

1. The load factor on L in combinations (3), (4), and (5) is permitted to equal 0.5 for all occupancies in which L0 is less than or equal to 100 psf, with the exception of garages or areas occupied as places of public assembly.

2. The load factor on H shall be set equal to zero in combinations (6) and (7) if the structural action due to H counteracts that due to W or E.

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16



ASCE 7-05 6.5 Analytical Procedure

• Directionality factor Kd introduced in 1998– Added to velocity pressure equation

•qz = 0.613 Kz Kzt Kd V2 I– Separate out effect of wind load factor– Requires adjustment to wind load factor ( 1.3 → 1.6 )– Table 6-4

Reason: Explicitly identify directionality effect in future editions.

ASCE 7-05 2.3.2 Strength Design Load Combinations

Wind load factor:• Old (1995): LF = 1.3 → included

directionality effect

0.85 (directionality) x 1.53 (LF w/o directionality) = 1.3

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Seismic Strength Design Load Combinations (1997 UBC)

• 1.2D + 1.0E + (f1L + f2S) Equation (12-5)

• 0.9D ± 1.0E Equation (12-6)

• E = ρEh + 0.5CaID in Equation (12-5)

• E = ρEh - 0.5CaID in Equation (12-6)

• ρ = 1 in Seismic Zones 1 and 2

Seismic Strength Design Load Combinations (2006 IBC, ASCE 7-05)

• 1.2D + 1.0E + f1L + f2S Equation (16-5)

• 0.9D + 1.0E Equation (16-7)

• E = ρQE + 0.2SDSD in Equation (16-5)

• E = ρQE - 0.2SDSD in Equation (16-7)

• ρ = 1 in Seismic Design Category (SDC) A, B and C

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18



Δs (UBC)

V

Eh (UBC)QE (IBC) δxe (IBC)

Effect of Vertical Earthquake Ground Motion (1997 UBC)

• Gravity and Earthquake Effects Additive

U = 1.2D + 1.0E + 0.5L +0.2S

= 1.2D + (ρEh + 0.5CaID) + 0.5L + 0.2S

= (1.2 + 0.5CaI)D + ρEh + 0.5L + 0.2S

32

19



Effect of Vertical Earthquake Ground Motion (ASCE 7-05)

• Gravity and Earthquake Effects Additive

U = 1.2D + 1.0E + 0.5L +0.2S

= 1.2D + (ρQE + 0.2SDSD) + 0.5L + 0.2S

= (1.2 + 0.2SDS)D + ρQE + 0.5L + 0.2S

Effect of Vertical Earthquake Ground Motion (1997 UBC)

• Gravity and Earthquake Effects Counteractive

U = 0.9D - 1.0E

= 0.9D - (ρEh + 0.5CaID)

= (0.9 - 0.5CaI)D - ρEh

33

20



Effect of Vertical Earthquake Ground Motion (ASCE 7-05)

• Gravity and Earthquake Effects Counteractive

U = 0.9D - 1.0E

= 0.9D - (ρQE + 0.2SDSD)

= (0.9 - 0.2SDS)D - ρQE

Beam C4 – C5Summary of Design Bending Moments and Shear Forces for Beam C4-C5

at the Second Floor Level

Shear Force (KN)

Bending Moment (m –KN)

LocationLoad combination

154.2Midspan167.0-224.3Support1.2D + 1.6L

132.4Midspan146.0-192.6Support1.4D

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Column C4

Tributary area = 7.92 × 6.71 = 53.14 m2

C

43

7.92 m

6.71 m

6.71 m

7.92 m

6.71 m

7.92 m

5

Column C4• Dead load:

Column self weight:0.66 × 0.66 × 11 × (3.66 – 0.560) × 23.55 = 349.92 kN

Slab self weight within the tributary area:4.781 ×53.14 × 11 = 2794.69 kN

Beam self weight within the tributary area:(0.560×0.355 ×7.92+0.560×0.355×(6.71-0.560))×23.55= 65.94 kN11 × 65.94 = 725.34 kN

Superimposed dead load:Roof: 0.479 + 889.64 / (20.73×56.08)* = 1.244 kN/m2

Floor: 1.436 kN/m2

1.244 × 53.14 + 1.436 × 53.14 × 10 = 829.20 kN*Done this way only because location of penthouse is notincluded

D = 349.92 + 2794.69 + 725.34 + 829.20 = 4699.15 kN

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22



Column C4

• Live load:

Story supporting roof:

R1 = 1.2 – 0.011 At = 1.2 – 0.011 × 53.14 = 0.615

R2 = 1.0

957.6 N/m2 × 0.615 × 1.0 = 588.92 N/m2

0.589 × 53.14 = 31.3 kN

Column C4

Story supporting floor 11:

AT = 53.14 + 53.14 = 106.28 m2

kLL = 4kLLAT = 425.12 m2 > 37.16 m2, therefore live load reduction is permitted.

Lo = 2.394 × 53.14 = 127.22 kNL = Lo (0.25 + 4.57 / (4 ×106.28)0.5)

= 127.22 × 0.472 > 0.40 Lo

L = 60.05 kN

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Column C4

Story supporting floor 10:AT = 53.14 × 3 = 159.42 m2

kLL = 4L = Lo (0.25 + 4.57 / (4 ×159.42)0.5)

= 127.22 × 0.431 = 54.83 > 0.40 Lo


kLL = 4L = Lo (0.25 + 4.57 / (4 ×212.56)0.5)

= 127.22 × 0.407 = 51.78 > 0.40 Lo

Column C4


kLL = 4L = Lo (0.25 + 4.57 / (4 ×265.7)0.5)

= 127.22 × 0.39 < 0.40 Lo

= 0.4 × 127.22 = 50.89 kN

Total live load:L = 31.3 + 60.05 + 54.83 + 51.78 + 7 × 50.89

= 554.19 kN

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Column C4Summary of Design Axial Forces, Bending Moments, and Shear Forces on

Column C4 Supporting the Second Floor Level

00554Live (L)004699Dead (D)

Shear Force (KN)

Bending Moment (m-KN)

Axial Force (KN)

Load Case

Column C4Summary of Design Axial Forces, Bending Moments, and Shear

Forces on Column C4 Supporting the Second Floor Level

0065251.2D + 1.6L

0065791.4D

Shear Forces

(KN)

Bending Moment (m-KN)

Axial Force (KN)Load combination

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Shear wall B7 – C7

Tributary Area = 7.92 × 13.42 = 106.29 m2

B

76

7.92 m

6.71 m

6.71 m

7.92 m

8

6.71 m

A

C

D

7.92 m

13.42 m

Shear wall B7 – C7• Dead load:

shear wall self weight (base):(2×0.66×0.66+0.305×6.05)×(45.14-0.560×12)×23.55 = 2458.59 kN

Slab self weight within the tributary area:4.781 × 106.29 × 12 = 6098.07 kN

Beam self weight within the tributary area:(0.560×0.355×13.42+2×0.560×0.355×(7.92-0.560))×23.55 = 131.89 kN12 × 131.89 = 1582.68 kN

Superimposed dead load:Roof: 0.479 + 889.64 / (20.73×56.08)* = 1.244 kN/m2

Floor: 1.436 kN/m2

1.244 × 106.29 + 1.436 × 106.29 × 11 = 1811.18 kN* Done this way only because location of penthouse is notincluded

D = 2458.59 + 6098.07 + 1582.68 + 1811.18 = 11,950.5 kN

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• Live load:

Story supporting roof:

R1 = 0.6 (At > 55.74 m2)

R2 = 1.0

957.6 N/m2 × 0.6 × 1.0 = 574.56 N/m2

0.575 × 106.29 = 61.12 kN


Story supporting floor 11:

AT = 106.29 + 106.29 = 212.58 m2

kLL = 3kLLAT = 637.74 m2 > 37.16 m2, therefore live load reduction is permitted.Lo = 2.394 × 106.29 = 254.46 kNL = Lo (0.25 + 4.57 / (3 ×212.58)0.5)

= 254.46 × 0.431 > 0.40 Lo

L = 109.67 kN

40

27





kLL = 3L = Lo (0.25 + 4.57 / (3 ×318.87)0.5)

= 254.46 × 0.398 < 0.40 Lo

= 0.4 × 254.46 = 101.78 kN

Total live load L = 61.12 + 109.67 + 101.78 ×10 = 1188.59 kN

Shear wall B7 – C7Summary of Design Axial Forces, Bending Moments, and

Shear Forces at Base of Shear Wall on Line 7 (SDC C)

001189Live (L)0011,951Dead (D)

Shear Forces (kN)


Axial Force (kN)

Load Case

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28





0016,2441.2D + 1.6L

0016,7311.4D

Shear Force (kN)


Axial Force (kN)

Load combination



42

1



Computation of Design Wind Forces

S. K. GhoshS. K. Ghosh Associates Inc.

Palatine, IL


Wind Flow Around Building

43

2



External Pressure due to Wind

External Pressure due to Wind

ps = pressure at stagnation point, psf (N/m2)pa = ambient pressure, psf (N/m2)ρ = air density, lb-sec2/ft4 (kg-sec2/m4)V = ambient wind speed, ft/sec (m/sec)

2

2

2

2

Vρppp

Vρpp

as's

as

=−=

+=

44

3



Velocity Pressure (ASCE 7-05)

• ASCE 7 includes two factors:– Topographic Factor - Kzt

• Hills and Escarpments• Complex Equations

– Directionality Factor - Kd

• 0.85 for all building structures

( )m/sec in VN/m inq

IKKKV613.0q

,2 z

dztz2

z =

Fastest-mile WindInstantaneous velocity of wind at a point as a function of time:

45

4



Fastest-mile Wind

• VT = max. wind speed based on averaging time of T sec• VH = max. wind speed based on averaging time of 1 hour

Fastest-mile Wind

• Max. wind speed averaged over one mile of

wind passing through anemometer.

• Averaging time of fastest-mile wind: T(sec)

3600/Vf

Vf – fastest-mile wind speed in mph

For Vf = 60 mph, T = 3600/60 = 60 sec

For Vf = 120 mph, T = 3600/120 = 30 sec

46

5



Return Period

• Also known as mean recurrence interval (MRI). • Used for the statistical determination of the

predicted wind speed. • Most U.S. inland locations, MRI of 50 years is used

for normal use structures. • MRI for critical use facilities such as hospitals is

100 years.• MRI for low risk buildings such as barns is 25

years.

Importance Factor• For MRI of 25, 50 , and 100 years -

• 3 Maps???? - No!

• MRI is adjusted by using importance factor, I.

• Ratio of difference in velocity pressure from one

MRI to another is a fairly consistent ratio for non-

hurricane locations.

• Inclusion of “I” in the wind pressure equation has

the mathematical effect of adjusting the wind

speed up or down.

47

6



Variation of Wind Velocity with Height for a Steady Wind

Gust

• Rapid fluctuation of wind• Ordinary structures sensitive to peak gusts of

about 1 sec duration.• Use of fastest-mile wind in design inadequate

Gust speed, Vg = Gv V• Pressure generated by gust, pg = Gp p

p ∝V 2 ∴ Gp = Gv2

• Flexible structures more sensitive to gust.

48

7



Gust Effect Factor

• Accounts for the loading effects in the along-wind

direction (parallel to the direction of the wind) due to

wind turbulence-structure interaction.

• Also accounts for along-wind loading effects due to

dynamic amplification for flexible structures.

• Does not account for other dynamic effects such as

across-wind Loads.

Dimensionless Pressure or Pressure Coefficient

221

'

221

ap V)(

pV)(ppC

ρρ=

−= p = actual pressure at any

arbitrary point on building, psf

49

8



Internal Pressure

Basic Wind Equation

• For buildings with External and Internal

Pressure:

qi = Velocity pressure calculated for

internal pressure.

piiGCqqGCp p −=

50

9



ASCE 7-056.2 Definitions

• Basic Wind Speed V : 3-second gust speed at 10 m above the ground in Exposure C.

– Removed reference to “50-yr mean recurrence

interval”

– Loads calculated from the wind speed map, when

multiplied by the wind load factor, represent an

“ultimate load” having approximately a 500 year

return period.

– Map contours include hurricane importance factor

51

10



ASCE 7-05Mean Roof Height

ASCE 7-056.5 Method 2: Analytical Procedure

• Design Pressure – MWFRS –Rigid Buildings of All Height (6.5.12.2.1):

p = q GCp - qi (GCpi)Velocity Pressure (6.5.10):

qz = 0.613KzKztKdV2I N/m2, V in m/sec

52

11




• Design Pressure – MWFRS – Rigid Buildings of All Height (6.5.12.2.1):

qi = qh for windward walls, side walls, leeward walls, and roofs of enclosed buildings and for negative pressure evaluation in partially enclosed buildings

qi = qz for positive pressure evaluation in partially enclosed buildings at height z from the ground. Can be conservatively taken as qh

Wind-resistant Design

• Wind Pressures on a Building

53

12




• Design Procedure (6.5.3):1. Wind Speed V (Figure 6-1 map), Wind Directionality Factor Kd (6.5.4.4, Table 6-4)2. Importance Factor I (6.5.5, Table 6-1)3. For each wind direction:

Exposure Category (6.5.6)

Velocity Pressure Exposure Coefficient Kh, Kz (6.5.6.6, Table 6-3)

ASCE 7-05 Fig. 6-1 Basic Wind Speed

54

13



Basic Wind Speed

Dubai

45 m/sec

(100 mph)

ASCE 7-05 Table 6-4 Wind Directionality Factor, Kd

55

14



ASCE 7-05 Table 6-1 Importance Factor, I

100 mph = 45 m/sec

ASCE 7-056.5.6.2 Surface Roughness Categories

• A ground surface roughness within

each 45-degree sector shall be

determined for a distance upwind of

the site as defined ….

56

15




• Surface Roughness B:

Urban and suburban areas, wooded areas

or other terrain with numerous closely

spaced obstructions having the size of

single-family dwellings or larger.


• Surface Roughness C:Open terrain with scattered obstructions having heights generally less than 9.1 m. This category includes flat open country, grasslands, and all water surfaces in hurricane-prone regions

57

16



ASCE 7-056.5.6.2 Roughness Categories

• Surface roughness D:

Flat, unobstructed areas and water

surfaces outside hurricane-prone regions.

This category includes smooth mud flats,

salt flats, and unbroken ice

ASCE 7-056.5.6.3 Exposure Categories

• Exposure B:Shall apply where Surface Roughness B prevails in the upwind direction for at least 792 m or 20 times the building height, whichever is greaterException. For buildings with h ≤ 9.1 m, the upwind distance may be reduced to 457 m.

58

17




• Exposure C:

Shall apply for all cases where

Exposure B or D does not apply


• Exposure D:shall apply where Surface Roughness D prevails in the upwind direction for at least 1524 m or 20 times the building height, whichever is greater. Exposure D shall extend into downwind areas of Surface Roughness B or C for a distance of 200 m or 20 times the building height, whichever is greater.

59

18



ASCE 7-05 Table 6-3Velocity Pressure Exposure

Coefficients, Kh and Kz

ASCE 7-05 Table 6-3 Velocity Pressure Exposure Coefficients, Kh and Kz

Table 6-2 Terrain Exposure ConstantsThe velocity pressure exposure coefficient

may be determined from the following formulas:For 4.6 m ≤ z ≤ zg, Kz = 2.01(z/zg)2/α

For z < 4.6 m, Kz = 2.01(4.6/zg)2/α

Note: z shall not be taken less than 9.1 m for Case 1 in Exp. B

21311.5D

2749.0C

3667.0B

Zg, mαExposure

60

19




(Continued from Slide 23)

• Design Procedure (6.5.3):4. Topographic Factor, Kzt (6.5.7, Figure 6-4)5. Gust Effect Factor G or Gf (6.5.8)6. Enclosure Classification (6.5.9)7. Internal Pressure Coefficient GCpi (6.5.11.1, Figure 6-5)8. External Pressure Coefficients Cp, GCpf (6.5.11.2) or force coefficients Cf (6.5.11.3)

ASCE 7-05 Fig. 6-4 Topographic Factors, Kzt

61

20



ASCE 7-05 Fig. 6-4 Topographic Factors, Kzt

ASCE 7-05 6.5.8 Gust Effect Factor, G or Gf

• For rigid structures as defined in Section 6.2, G shall be taken as 0.85 or calculated by Eqs. 6-4, 6-5, 6-6 and 6-7, using Table 6-2.

• For flexible or dynamically sensitive structures as defined in Section 6.2, Gf shall be calculated by Eqs. 6-8, 6-9, 6-10, 6-11, 6-12, 6-13a, 6-13b and 6-14, using Table 6-2.

62

21



ASCE 7-05 6.2 Definition-Enclosure Classification

• Buildings, Open:A building having each wall at least 80% open.Mathematically, Ao > 0.8Ag where:Ao = Total area of openings in a wall that receives positive external pressure, in m2

Ag= Gross area of that wall in which Ao is identified, in m2

ASCE 7-05 6.2 Definition-Enclosure ClassificationBuildings, Partially Enclosed:If the following two conditions are satisfied:1. Ao > 1.1Aoi

2. Ao > 0.37 m2 or >0.01Ag, whichever is smaller, & Aoi < 0.2Agi

where:Aoi = The sum of the areas of openings in the building envelope (walls & roof) not including Ao, in m2

Agi = The sum of the gross surface areas of the building envelope (walls & roof) not including Ao, in m2

63

22



ASCE 7-05 6.2 Definition-Enclosure Classification

• Buildings, Enclosed:

A building that does not comply with

the requirements for open or partially

enclosed buildings.

ASCE 7-05 6.5.9.3 Wind Borne Debris Regions

– Glazing in lower 18.3 m or within

9.2 m above aggregate surface

roofs located within 458 m of a

Category II, III, IV building requires

impact resistant glazing or

covering

64

23



ASCE 7-05Figure 6-5 Internal Pressure Coefficients,

GCpi

ASCE 7-05External Pressure Coefficients

Cp for main wind force resisting systems –Fig. 6-6

GCpf for low-rise buildings – Fig. 6-10GCp for components & cladding – Fig. 6-11

through 6-17CN for main wind force resisting systems – Fig. 6-18

for components & cladding – Fig. 6-19Cf - Figs. 6-20 through 6-23

65

24



ASCE 7-05 Fig. 6-6External Pressure

Coefficient, Cp for

MWFRS

ASCE 7-05 Fig. 6-6 Cp for MWFRS: Walls

66

25



ASCE 7-05 Fig. 6-6 Cp for MWFRS: Roofs

ASCE 7-05 Fig. 6-6 Cp for MWFRS

67

26




(Continued from Slide 37)

• Design Procedure (6.5.3)

9. Velocity Pressure qz, qh (6.5.10)

qz = 0.613 Kz Kzt Kd V2 I Eq. 6-15


• Design Procedure (6.5.3)10. Design wind pressure p (6.5.12, 6.5.13)

Enclosed or Partially Enclosed Buildings, MWFRS:

Rigid, All heights: p = q GCp - qi(GCpi) Eq. 6-17

Parapets: pp = qp GCpn Eq. 6-20

68

27



ASCE 7-05 6.5 Analytical Procedure• Design Procedure (6.5.3)

10.Enclosed and Partially Enclosed Buildings - C & C

(6.5.12.4):

– Low rise and buildings with h ≤ 18.3 m

p = qh[(GCp) - (GCpi)] Eq. 6-22

– Buildings with h > 18.3 m

p = q(GCp) - qi(GCpi) Eq. 6-23

– Parapets

p = qp(GCp - GCpi) Eq. 6-24


A

B

C

D

1 2 3 4 5 6

N

7 87.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m

6.71

m6.

71 m

6.71

m

69

28




11@

3.66

m=

40.2

6 m

10

11

12

7

8

9

4

5

6

1

2

3

4.88

m

Design Data

• Building LocationDubai, UAE


’ = 30 MPa, wc = 23.55 KN/m3

Reinforcement: fy = 415 MPa

70

29



Design Data

• Service LoadsLive loads: roof = 957.6 N/m2

floor = 2394 N/m2


roof = 478.8 N/m2 + 889.64 KN for penthouse


Design Data

• Wind Design DataBasic wind speed V = 45 m/sec for DubaiExposure B (IBC 1609.4, ASCE 6.5.6.3)For Occupancy Category II, I = 1.0 (IBC Table 1604.5, ASCE Table 6-1)

71

30



Design Data


Slab: 205 mm

Beams: 560 × 560 mm




Wind Load Analysis

1. Basic wind speed, V, and wind directionality factor, Kd

V = 45 m/sec at location of structure per IBC Figure 1609 or ASCE Figure 6-1.

The wind directionality factor, Kd = 0.85 for main wind-force-resisting systems of buildings per ASCE Table 6-4.

72

31



Wind Load Analysis

2. Importance factor, I

I = 1.0 per ASCE Table 6-1 for Occupancy

Category II

Wind Load Analysis3. Exposure category and velocity

pressure exposure coefficient, Kz

Values of Kz are to be determined from ASCE Table 6-3. In lieu of linear interpolation, Kz may be calculated at any height z ft above ground level by the following equations:

m 4.6 for 01.2

m 4.6 for 1501.2

/2

/2

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

≤≤⎟⎟⎠

⎞⎜⎜⎝

⎛

<⎟⎟⎠

⎞⎜⎜⎝

⎛

=

gg

g

z

zzzz

zz

Kα

α4.6

73

32



Wind Load Analysis

α = 3-second gust speed power law exponentfrom ASCE Table 6-2

= 7.0 for Exposure B

Zg = nominal height of the atmosphericboundary layer from ASCE Table 6-2

= 366 m for Exposure B

Wind Load AnalysisVelocity Pressure Exposure Coefficient Kz

0.5864.8810.6878.5420.76112.2030.82015.8640.87019.5250.91423.1860.95326.8470.98930.5081.02134.1691.05137.82101.07941.48111.10645.1412

KzHeight above ground level, z (m)

Level

74

33



Wind Load Analysis

4. Topographic factor, Kzt

Assuming the example building is situated on level ground and not on a hill, ridge, or escarpment, Kzt is equal to 1.

Wind Load Analysis

5. Gust effect factors, G and Gf

Gust effect factor depends on whether a building is rigid or flexible (ASCE 6.5.8). A rigid building has a fundamental natural frequency n1 greater than or equal to 1 Hz, while a flexible building has a fundamental natural frequency less than 1 Hz (ASCE 6.2).

75

34



Wind Load Analysis

N-S direction:

Ta = 1/n1 = 0.0488 (hn)3/4 = 0.0488 (45.14)3/4

= 0.85 sec < 1 sec

So building is rigid and G = 0.85

See ASCE 7-05 Commentary Section C6.5.8

Wind Load Analysis

E-W direction:

Ta = 1/n1 = 0.0466 (hn)0.9 = 1.44 sec > 1 sec

So building is flexible.

Extensive calculation using n1 = 1/1.44 = 0.7Hz yields Gf = 0.93

See ASCE 7-05 Commentary Section C6.5.8

76

35



6. Enclosure classification

It is assumed in this example that the building is enclosed per IBC 1609.2, ASCE 6.5.9.

Wind Load Analysis

Wind Load Analysis

7. Internal pressure coefficient, GCpi

For an enclosed building, GCpi = ± 0.18.

77

36



Wind Load Analysis8. External pressure coefficients, Cp

For wind in the N-S direction (ASCE Figure 6-6) :Windward wall: Cp = 0.8

Leeward wall (L/B = 20.7/56.1 = 0.37): Cp = -0.5

Side wall: Cp = - 0.7

Roof (h/L = 45.1/20.7 = 2.18):

Cp = -1.3 over entire roof (20.7 m < h/2 = 22.6 m).

May be reduced to 0.80 × -1.3 = -1.04 for area

greater than 93 m2 per Figure 6-6.

Wind Load Analysis

For wind in the E-W direction:Windward wall: Cp = 0.8Leeward wall (L/B = 56.1/20.7 = 2.70):

Cp = -0.26Side wall: Cp = -0.7Roof (h/L = 45.1/56.1 = 0.80):

Cp = -1.14 from windward edge to h/2 = 22.6 mCp = -0.78 from 22.6 m to h = 45.1 mCp = -0.62 from 45.1 m to 56.1 m

78

37



Wind Load Analysis

9. Velocity pressure, qz

The velocity pressure at height z is determined by Eq. 6-15 in ASCE 6.5.10:

qz = 0.613 Kz Kzt Kd V2 I N/m2, V in m/sec

where all terms have been defined previously.

Wind Load AnalysisVelocity Pressure qz (V = 45 m/sec)

6180.5864.8817250.6878.5428030.76112.2038650.82015.8649180.87019.5259640.91423.186

10060.95326.84710440.98930.50810771.02134.16911101.05137.821011381.07941.481111671.10645.1412

qz(N/m2)

KzHeight above ground level, z (m)Level

where q = qz for windward walls at height z above groundq = qh for leeward walls, side walls, and roof, evaluated at height hqi = qh for all walls and roofs of enclosed buildings

79

38



Wind Load Analysis

10. Design wind pressure, p

For rigid buildings of all heights, design wind pressures on the main wind-force-resisting system are calculated by Eq. 6-17:

p = q GCp – qi (GCpi)

Wind Load AnalysisDesign Wind Pressure in N-S Direction (V = 45 m/sec)

± 210± 0.181167-1032-1.040.85116745.14---Roof± 210± 0.181167-694-0.70.851167All---Side± 210± 0.181167-496-0.50.851167All---Leeward± 210± 0.1811674200.800.856184.881± 210± 0.1811674930.800.857258.542± 210± 0.1811675460.800.8580312.203± 210± 0.1811675880.800.8586515.864± 210± 0.1811676240.800.8591819.525± 210± 0.1811676560.800.8596423.186± 210± 0.1811676840.800.85100626.847± 210± 0.1811677100.800.85104430.508± 210± 0.1811677320.800.85107734.169± 210± 0.1811677550.800.85111037.8210± 210± 0.1811677740.800.85113841.4811± 210± 0.1811677940.800.85116745.1412

Windward

qiGCpi(N/m2)

GCpiqi(N/m2)

qGCp(N/m2)

CpGq(N/m2)

Internal PressureExternal PressureHeight above ground level,z(m)

LevelLocation

80

39



Wind Load AnalysisDesign Wind Pressure in N-S Direction (V = 45 m/sec)

205.0118.8-49686.24204.274.881203.0101.8-496101.24933.668.542213.9101.8-496112.15463.6612.203222.5101.8-496120.75883.6615.864229.9101.8-496128.16243.6619.525236.5101.8-496134.76563.6623.186242.2101.8-496140.46843.6626.847247.6101.8-496145.87103.6630.508252.1101.8-496150.37323.6634.169256.8101.8-496155.07553.6637.8210260.7101.8-496158.97743.6641.4811132.450.9-49681.57941.8345.1412

Design Wind

Force, P* (kN)

External Design Wind

Pressure, qhGfCp(N/m2)

Design Wind

Force, P* (kN)


Pressure,qzGfCp(N/m2)

Total Design Wind Force (kN)

LeewardWindwardTributary Height

(m)

Height above

ground level, z

(m)Level

*P = qGCp × Tributary height × 56.1 m Σ 2702.6

Wind Load Analysis

For flexible buildings, Eq. 6-19 is to be used:

p = q GfCp – qi (GCpi)

81

40



Wind Load AnalysisDesign Wind Pressure in E-W Direction (V = 110 mph)

± 210± 0.181167-1237-1.140.93116745.14*---± 210± 0.181167-847-0.780.93116745.14†---± 210± 0.181167-673-0.620.93116745.14‡---

Roof± 210± 0.181167-760-0.700.931167All---Side± 210± 0.181167-282-0.260.931167All---Leeward± 210± 0.1811674590.800.936184.881± 210± 0.1811675390.800.937258.542± 210± 0.1811675970.800.9380312.203± 210± 0.1811676430.800.9386515.864± 210± 0.1811676830.800.9391819.525± 210± 0.1811677180.800.9396423.186± 210± 0.1811677480.800.93100626.847± 210± 0.1811677770.800.93104430.508± 210± 0.1811678010.800.93107734.169± 210± 0.1811678260.800.93111037.8210± 210± 0.1811678470.800.93113841.4811± 210± 0.1811678680.800.93116745.1412

Windward

qiGCpi(N/m2)

GCpiqi(N/m2)

qGCp(N/m2)

CpGq(N/m2)

Internal PressureExternal PressureHeight above

ground level,z(m)

LevelLocation

* from windward edge to 22.6 m, † from 22.6 m to 45.1 m, ‡ from 45.1 m to 56.1 m

Wind Load AnalysisDesign Wind Pressure in E-W Direction (V = 110 mph)

65.524.9-28240.64594.274.88162.221.4-28240.85393.668.54266.621.4-28245.25973.6612.20370.121.4-28248.76433.6615.86473.121.4-28251.76833.6619.52575.821.4-28254.47183.6623.18678.121.4-28256.77483.6626.84780.321.4-28258.97773.6630.50882.121.4-28260.78013.6634.16984.021.4-28262.68263.6637.821085.621.4-28264.28473.6641.481143.610.7-28232.98681.8345.1412

Design Wind Force, P* (kN)


Pressure, qhGfCp(N/m2)

Design Wind Force, P* (kN)


Pressure,qzGfCp(N/m2)

Total Design Wind Force (kN)

LeewardWindwardTributary Height

(m)

Height above

ground level, z

(m)Level

Σ 867.0*P = qGCp × Tributary height × 20.7 m

82

41



Wind Load AnalysisDesign Wind Force in N-S and E-W Direction (V = 45 m/sec)

65.5205.04.88162.2203.08.54266.6213.912.20370.1222.515.86473.1229.919.52575.8236.523.18678.1242.226.84780.3247.630.50882.1252.134.16984.0256.837.821085.6260.741.481143.6132.445.1412

Total Design Wind

Force E-W (kN)

Total Design Wind

Force N-S (kN)

Height above ground

Level, z (m)

Level

Σ 2702.6 867.0

Wind Load Analysis

The stiffness properties of the members were input assuming cracked sections. The following cracked section properties were used:

Beam: Ieff = 0.5 IgColumn: Ieff = 0.7 IgShear walls: Ieff = 0.5 Ig

where Ig is the gross moment of inertia of section.

83

42



Wind Load Analysis

According to ASCE 6.5.12.3, the main wind-force-resisting systems of buildings of all heights, whose wind loads have been determined according to ASCE 6.5.12.2.1 and 6.5.12.2.3, must be designed for the full and partial wind load cases of Figure 6-9 (Cases 1 through 4). These four cases were considered in the three-dimensional analyses.

Wind Load AnalysisResults of 3-D Analysis under Wind Force in E-W Direction for

Frame C (V = 45 m/sec)

33-3333-3333-34351

33-3333-3333-33342

31-3131-3131-31313

28-2828-2828-28284

25-2525-2525-24255

22-2222-2221-21216

19-1919-1919-18187

15-1515-1515-14158

12-1212-1212-10119

8-88-88-7710

5-55-55-4411

2-22-22-1112

-2.8-2.8-2.8-2.91

-2.8-2.8-2.8-2.82

-2.6-2.6-2.6-2.63

-2.4-2.4-2.4-2.44

-2.1-2.1-2.1-2.15

-1.9-1.9-1.9-1.86

-1.6-1.6-1.6-1.57

-1.3-1.3-1.3-1.28

-1.0-1.0-1.0-0.99

-0.7-0.7-0.7-0.610

-0.4-0.4-0.4-0.311

-0.2-0.2-0.2-0.112

Bending Moments in Beams (m-kN) Shear Forces in Beams (kN)

84

43



Wind Load AnalysisResults of 3-D Analysis under Wind Force in E-W Direction for Frame C

(V = 45 m/sec)

69695064-27-27-21-17133332614-33-33-26-17227272215-32-32-25-18325252011-30-30-24-17421211810-27-27-21-1551919158-25-25-20-1461515136-21-21-17-1371212104-19-19-15-1189972-16-16-12-1095551-12-12-9-810222-1-9-9-6-611000-2-4-4-3-212

6.46.44.85.41

6.66.65.33.02

5.95.94.83.23

5.55.54.42.74

4.94.93.92.55

4.34.33.42.16

3.73.72.91.97

3.13.12.41.58

2.42.41.91.29

1.81.81.40.810

1.11.10.80.511

0.50.50.3-0.112

0.00.10.219.31

0.00.10.216.42

0.00.10.313.53

0.00.00.310.94

0.00.00.38.55

0.00.00.36.46

0.00.00.24.67

0.00.00.23.18

0.00.00.21.99

0.00.00.11.010

0.00.00.10.411

0.00.00.00.112

Bending Moments in Columns (m-kN)

Shear Forces in Columns (kN)

Axial Forces in Columns (kN)

Wind Load AnalysisResults of 3-D Analysis under Wind Force in N-S Direction for

Frame 4 (V = 45 m/sec)

30-30321

39-38392

44-43443

47-45464

47-45475

47-44466

45-42437

43-39408

39-36379

36-323310

35-303111

25-222312

-3.1-3.11

-3.9-3.92

-4.4-4.43

-4.8-4.74

-4.8-4.75

-4.8-4.66

-4.6-4.37

-4.3-4.08

-4.0-3.79

-3.7-3.310

-3.5-3.111

-2.6-2.312

Bending Moments in Beams (m-kN)

Shear Forces in Beams (kN)

85

44



Wind Load AnalysisResults of 3-D Analysis under Wind Force in N-S Direction for Frame 4

(V = 45 m/sec)

4641-15-614123-28-1124326-35-1634524-41-2044423-43-2254321-44-2364120-43-2373818-41-2283416-39-2193114-36-19102812-30-16113012-45-2312

4.13.21

6.93.32

7.84.23

8.64.44

8.84.55

8.74.46

8.44.27

7.93.98

7.33.69

6.83.210

5.82.811

7.43.512

2.646.21

2.743.12

2.639.23

2.634.74

2.430.15

2.325.46

2.020.77

1.816.68

1.412.59

1.18.810

0.75.511

0.22.312

Bending Moments in Columns (m-kN)



Wind Load AnalysisResults of 3-D Analysis under Wind Forces in N-S Direction for

Wall on Column Line 7 (V = 45 m/sec)

-143820,045-1305501-120613,360-896602-10219376-566003-5876143-302204-7093545-96305-572149958206-442-52166207-318-1153230808-196-1829235909-68-2093253901043-19291772011

285-1383343012BottomTop

Shear Force(kN)

Bending Moment (m-kN)Axial Forces(kN)Level

86

45





87



1

An Overview of the Design Load Combinations and the Seismic Design

Provisions of the 1997 UBC



88



2

Referenced Standards

Design Loads and Load Combinations ASCE 7-95Concrete ACI 318-95Masonry NoneSteel MultipleWood AF&PA NDS - 91

Referenced Steel Standards

None

AISI LRFD 1991AISI ASD 1986 (with 1989 addendum)

AISC Seismic 1992

AISC ASD 1989

AISC LRFD 1993

1997 UBC

89



3

Structural Design Requirements1997 UBC

Chapter 16 – Design Loads Chapter 17 – Inspections / Testing Chapter 18 – FoundationsChapter 19 – ConcreteChapter 20 – AluminumChapter 21 – MasonryChapter 22 – SteelChapter 23 – Wood


E = Design earthquake force (strength-level)

(12-6)0.9D ± (1.0E or 1.3W)U =

(12-5)1.2D + 1.0E + (f1L + f2S)U =

(12-4)1.2D + 1.3W + f1L + 0.5(Lr or S)U =

(12-3)1.2D + 1.6(Lr or S) + (f1L or 0.8W)U =

(12-2)1.2D + 1.6L + 0.5 (Lr or S)U =

(12-1)1.4DU =

90



4


U = 1.2D + 1.0E + (f1L + f2S) (12-5)U = 0.9D ± (1.0E or 1.3W) (12-6)E = ρEh + Ev in (12-5), (12-6)Ev = 0.5CaID• ρ = 1 in Seismic Zones 0,1,2

EhΔs

V

91



5

Effect of Vertical Earthquake Ground Motion

• Gravity and Earthquake Effects AdditiveU = 1.2D + 1.0E + 0.5L +0.2S

= 1.2D + (ρEh + 0.5CaID) + 0.5L + 0.2S= (1.2 + 0.5CaI)D + ρEh + 0.5L + 0.2S

Effect of Vertical Earthquake Ground Motion

• Gravity and Earthquake Effects CounteractiveU = 0.9D - 1.0E

= 0.9D - (ρ Eh + 0.5CaID)= (0.9 - 0.5CaI)D - ρEh

92



6

Strength Design or LRFD Load Combinations - Exceptions

UBC Exceptions for concrete structures

1612.3.1 ASD Load Combinations -Basic (1997 UBC, from ASCE 7-95)

D (12-7)

D + L + (Lr or S) (12-8)

D + (W or E/1.4) (12-9)

0.9D + E/1.4 (12-10)

D + 0.75[L + (Lr or S) + (W or E/1.4)] (12-12)

E = ρEh + 0

93



7

ASD Load Combinations - Basic (ASCE 7-95) – Allowable Stress Increase

• 1/3 stress increase not permitted• Load duration increase permitted

1612.3.2 ASD Load Combinations -Alternate Basic (1997 UBC)

D + L + (Lr or S) (12-12) D + L + (W or E/1.4) (12-13) D + L + W + S/2 (12-14) D + L + S + W/2 (12-15) D + L + S + E/1.4 (12-16) 0.9D + E/1.4 (?)

E = ρEh + 0

94



8

ASD Load Combinations -Alternate Basic (1997 UBC) – Allowable

Stress Increase

• When using these alternate basic load combinations that include wind or seismic loads, allowable stresses are permitted to be increased or load combinations reduced, where permitted by the material chapter of this code or referenced standard.

1612.4 Special Seismic Load Combinations (1997 UBC)

• 1.2D + f1L + 1.0Em (12-17)• 0.9D + 1.0Em (12-18)

Em = Ω0Eh, whileE = ρEh + Ev

95



9

1997 UBC Seismic Design Provisions

Introduction andBasic Principles


Based on 1996 SEAOC Blue Book,

influenced by the1994 NEHRP Provisions

96



10

1626.1 Purpose

The purpose of the earthquake provisions herein is primarily to safeguard against major structural failures and loss of life…not to limit damage or maintain function.

Purpose

SEAOC “Blue Book” Commentary…

• Resist minor ground motion without damage

• Resist moderate ground motion without structural damage but with some nonstructural damage

• Resist major ground motion without collapse but with possible structural / nonstructural damage

• Provisions will not prevent damage from earth faulting, slides or similar movements, nor soil liquefaction

97



11

1997 UBC Design Earthquake Ground Motion

• Approximately 90% probability of non-exceedance in 50 years (approx. 475 yr. return period)

Idealized Force-Displacement

98



12

Idealized Relationship between Base Shear and Drift

Earthquake-Induced Forces

• FM ≈ ΩoFS» FM = Maximum inelastic response force» FS = Code-prescribed force» Ωo = Seismic force amplification factor

Ωo gives a reasonable approximation of actual forces acting in an inelasticallyresponding structure

99



13

EQ Design Considerations• Seismic Zone• Proximity to known Faults• Site Geology and soil characteristics• Building Occupancy• Structural framing system• Structural configuration… regular or

irregular• System redundancy• Building height• Lateral force procedure• Framing system limitations• Special strength and detailing

1626.3 Earthquake vs. Wind

1. Code-Prescribed Forces2. Exposed Area vs. Mass3. Design for Larger Force4. Provide Seismic Detailing

100



14

EQ Design Procedure• Step 1 – Select basic structural system• Step 2 – Identify lateral force-resisting

system• Step 3 – Identify structural

irregularities and any framing system limitations

• Step 4 – Select lateral force procedure• Step 5 – Calculate total design base

shear and distribute over height of structure

EQ Design Procedure

• Step 6 – Elastically analyze building, including torsional effects. Include P-Δeffects, if necessary

• Step 7 – Check story drift limitations• Step 8 – Calculate redundancy (ρ) of lateral

force-resisting system and increase earthquake forces as necessary

• Step 9 – Design elements of lateral force-resisting system for required strength and do special detailing

• Step 10 – Confirm complete load path to resist earthquake forces

101



15

Sec 1702Structural Observation

Required for:

1. Essential facilities, hazardous facilities and special occupancy structures (Table 16-K)

2. “High-rise” office building, hotels and apartments (Section 403)

3. Seismic Zone 4… Near-Source Factor (Na) greater than 1.0

Sec 1702Structural Observation

4. When designated by A/E of record or building official

• Seismic Zones 3 and 4 only• Structural system only• Performed by A/E of record or designated A/E• Periodic site visits• Compliance with plans and specifications• Final report to building official

Note: Structural Observations does not waive inspections by Section 108 and 1701

102



16


Structural Systems

103



17

1997 UBC Fig. 16-3Design Response Spectra

1997 UBC Sec. 1630.2 Static Force Procedure

104



18

Response Modification Factor, R

8.5 > R > 2.2

IBC vs. UBC Response Modification Factor, R• 1997 UBC (Strength-level

earthquake forces)Table 16-N

Bearing wall systemR = 4.5

Special moment resisting frame system

R = 8.5

105



19

Table 16-N – Structural Systems1

Footnote for Table 16-NN.L. – no limit1 See Section 1630.4 for combination of structural systems.2 Basic structural systems are defined in Section 1629.6.3 Prohibited in Seismic Zones 3 and 4.4 Includes precast concrete conforming to Section

1921.2.7.5 Prohibited in Seismic Zones 3 and 4, except as permitted

in Section 1634.2.6 Ordinary moment-resisting frames in Seismic Zone 1

meeting the requirements of Section 2211.6 may use a Rvalue of 8.

7 Total height of the building including cantilevered columns.

8 Prohibited in Seismic Zones 2A, 2B, 3 and 4. See Section 1633.2.7.

106



20

Sec 1630.4.2Vertical Combinations

Sec 1630.4.2Vertical Combinations

1. Design structure for lowest (R) for structural systems used… or

2. Two-stage analysis permitted for structures with flexible upper portion supported by rigid lower portion (Sec 1629.8.3 Item 4)

3. In Seismic Zones 3 & 4, dynamic analysis required for structures > 5 stories or 19.8 m in height with vertical combinations (Sec 1629.8.4 Item 3)

107



21

Sec 1630.4.3Combinations Along Different Axes

• With bearing wall system in only one direction, (R) not greater in orthogonal direction (Zones 3 and 4 only)

Sec 1630.4.3Combinations Along Different Axes

• Structures < 48 m» Bearing wall system» Building frame system» Moment-resisting frame system» Dual system

• Structures > 48 m (Zones 3 and 4 only)» Special moment-resisting frames» Dual systems

108



22

Sec 1630.4.4Combinations Along Same Axes

• With different structural systems in same direction, value of (R) in that direction to be taken as least (R) for structural systems utilized

• Dual systems…and shear wall-frame interactive systems in Seismic Zones 0 & 1…excluded

Sec 1630.4.4Combinations Along Same Axes

109



23


Static Force Procedure


110



24


Terms to Calculate Earthquake Load

111



25

UBC Seismic Zones

Table 16-I Seismic Zone Factor

0.0751

0.152A

0.22B

0.33

0.44

ZSeismic Zone

112



26

Table 16-1 Seismic Zone Factor

• Accounts for geographical variations in expected levels of earthquake ground shaking

• Seismic zone map (Fig 16-2) estimates effective peak horizontal acceleration on rock with a 10 percent probability of being exceeded in a 50-year period

• See Appendix 1A – Seismic Zone Coefficient… in 1996 SEAOC “Blue Book”

Soil Profile Types / Site Classes

FSoil Requiring Site-Specific

EvaluationSF

ESoft Soil ProfileSE

DStiff Soil ProfileSD

CVery Dense Soil and Soft RockSC

BRock (west coast rock)SB

AHard Rock (east coast rock)SA

Site ClassSoil Profile DescriptionSoil Profile Type

113



27

Table 16-J – Soil Profile Types

< 50< 15< 180Soft Soil ProfileSE1

Soil Requiring Site-specific Evaluation. See Section 1629.3.1.SF

50 to 10015 to 50180 to 360Stiff Soil ProfileSD

> 100> 50360 to 760Very Dense Soil and Soft Rock

SC

760 to 1,500

RockSB

> 1,500Hard RockSA

UndrainedShear

Strength (kPa)

Standard Penetration Test, N [or NCH for cohesionless soil

layers] (blows/foot)

Shear Wave velocity (m/sec)

Average Soil Properties for Top 30,480 mm of Soil Profile

Soil Profile Name/

Generic Description

Soil Profile Type

Default Soil Profile Type

• Soil Profile Type SD must be used when the soil properties are not known in sufficient detail, unless the building official determines that Soil Profile Type SE or SF is likely to be present at the site

114



28

Soil-Modification of Short-Period Ground Motion (1997 UBC)

Soil-Modification of Long-Period Ground Motion (1997 UBC)

115



29

SEISMIC GROUND MOTION AMPLIFICATION DUE TO SOIL, Ca / Z (1997 UBC)

*****SF

0.9Na2.21.72.02.5SE

1.1Na1.21.41.51.6SD

1.0Na1.11.21.21.2SC

1.0Na1.01.01.01.0SB

0.8Na0.80.80.80.8SA

Z = 0.40Z = 0.30Z = 0.20Z = 0.15Z = 0.075

SEISMIC ZONE FACTOR - ZSOIL PROFILE

TYPE

* Site specific geotechnical investigation and dynamic site response analysis required

SEISMIC GROUND MOTION AMPLIFICATION DUE TO SOIL, Cv / Z (1997 UBC)

*****SF

2.4Nv2.83.23.33.5SE

1.6Nv1.82.02.12.4SD

1.4Nv1.51.61.71.7SC

1.0Nv1.01.01.01.0SB

0.8Nv0.80.80.80.8SA

Z = 0.40Z = 0.30Z = 0.20Z = 0.15Z = 0.075

SEISMIC ZONE FACTOR - ZSOIL PROFILE

TYPE

* Site specific geotechnical investigation and dynamic site response analysis required

116



30

TABLE 16-S NEAR-SOURCE FACTOR Na(1997 UBC)

1.01.01.0C

1.01.01.3B

1.01.21.5A

≥ 10 km5 km≤ 2 km

Closest Distance to Known Seismic Source

Seismic Source Type

TABLE 16-T NEAR-SOURCE FACTOR Nv(1997 UBC)

1.0

1.0

1.0

≥ 15 km

1.01.01.0C

1.01.21.6B

1.21.62.0A

10 km5 km≤ 2 km

Closest Distance to Known Seismic SourceSeismic Source Type

117



31

Design Spectrum


118



32

63

Table 16-K Occupancy Category

1.001.00Factories; Private Garages; Carports/Sheds

5. Miscellaneous structures

1.001.00Hotels; Apartments; Dwellings; Wholesale/Retail; Office Bldgs

4. Standard occupancy structures

1.001.00Public Assembly; Schools; Day-Care Centers; Nurseries; Nursing Homes; Jails

3. Special occupancy structures

1.501.25Dangerous Toxic or Explosive Substances

2. Hazardous facilities

1.501.25Hospitals; Fire/Police Stations; Emergency Shelters

1. Essential facilities

Seismic Importance

Factor Ip

Seismic Importance

Factor I

Occupancy or Function of Structure

Occupancy Category

Seismic Importance Factor, I

• Used to amplify….design forces as a means of controlling damage and producing “enhanced”performance in Occupancy Categories 1 and 2

119



33

Minimum Design Base Shear• All Seismic Zones

Vmin = 0.11 Ca I W 1997 UBC

Minimum Design Base Shear

• Seismic Zone 4

UBC 1997 R

I0.8ZNV WV

min =

120



34

Structure Period

Calculated by……1) Approximate Formulae

2) Rational Analysis using structural properties and deformational characteristics of resisting elements in a properly substantiated analysis

Approximate Period Formulae

Ta = CT (hn)3/4 1997 UBC (30-8)

0.0853Steel Moment Frames

0.0488All other buildings

0.0731Concrete Moment FramesEccentrically Braced Steel

Frames

CTLateral Force Resisting System

121



35

Approximate Period Formula(Optional – 1997 UBC )

For structures with concrete or masonry shear walls,

Ct = 0.0743/√Ac

Ac = ΣAe[0.2 + (De/hn)2]

Replaced by a different formula in ASCE 7-05

70

Rayleigh Formula

(30-10)

)(2

2

ΔΣ+ΔΔΣ

π=FtFtg

wT)(

22

ΔΣ+ΔΔΣ

π=FtFtg

wT)(

22

ΔΣ+ΔΔΣ

π=FtFtg

wT

)(2

2

ΔΣ+ΔΔΣ

π=FtFtg

wT

122



36

Upper Limit on T by "Rational Analysis"

1997 UBCT ≤ 1.3 Ta, Zone 4≤ 1.4 Ta, Zones 1,2,3

1997 UBC 1630.1.1 Effective Seismic Weight

V = CSWW = total dead load + ……

• Warehouses………………..…………..25% live• Buildings with partitions……………….0.48 kN/m2

• Design snow load > 1.44 kN/m2………… ≥ 25% design snow load **• Permanent equipment…………………100% dead

** UBC leaves this up to local jurisdictions

123



37

IBC vs. UBCVertical Force Distribution

07TV.0sec....F 0.7T0sec....F 0.7T

where

)F-(VwhhwF

t

t

txx

x

=>=≤

=∑

1997 UBC

≤ 0.25V

Vertical Force Distribution1997 UBC

124



38

125



39

1997 UBC 1630.6 Horizontal Distribution of Forces

• Rigid diaphragms» Seismic story shear is to be distributed to

elements of seismic-force-resisting system based on stiffness of vertical-resisting elements

• Flexible diaphragms» Seismic story shear is to be distributed to

elements of seismic-force-resisting system based on tributary areas

Sec 1630.6Diaphragm Flexibility

• Diaphragm considered flexible if… Max.diaphragm deflection Δ > 2 (Averagestory drift)

126



40

Sec 1630.6Diaphragm Flexibility

• Compare midpoint in-plane deflection of diaphragm (Δ) with average story drift of adjoining vertical resisting elements

• Torsion» Torsional moment due to difference in location

of center of mass and center of resistancemust be considered for rigid diaphragms

• Accidental torsion» For rigid diaphragms, must be included in

addition to the torsional moment• Displacement of center of mass = 5% building dimension

perpendicular to direction of applied forces

1997 UBC 1630.6 Horizontal Distribution of Forces

127



41

Sec 1630.1.2Modeling Requirements

“Accuracy of Results”Mathematical model of physical structure to

include…• All elements of lateral-force-resisting system• All stiffness and strength significant to force

distribution…representation of spatial distribution of mass and stiffness of structure

• Effects of “cracked sections” for concrete and masonry

• Contribution of panel zone deformation to story drift for steel moment frames

Even with new guidelines for structure modeling…structure period (T) calculated by “rational analysis” still RESTRICTED

1997 UBC 1630.9 Story Drift Determination (Δ)

Lateral displacement of one level relative to the next level above or below

x

128



42

EhΔS

V

1997 UBC 1630.10 Story Drift Limitation

1997 UBCΔx = ΔM,x - ΔM,x-1 ≤ Δa

where….ΔM,x = 0.7R Δs,x

129



43

Allowable Story Drift (Δa ) 1997 UBC

Δa = 0.020 hsx for T ≥ 0.7 sec.= 0.025 hsx for T < 0.7 sec.

hsx = Story height below level x

REDUNDANCY

130



44

Redundancy

ρ = 1 in Seismic Zones 1 and 2

ANALYSIS PROCEDURES

131



45

Static vs. Dynamic Analysis (1997 UBC)

WhatSeismicZone?

Is No. ofStories ≤ 5 and

Ht. ≤ 19.8 m?

Is Bldg.Irregular

Table 16-L1, 2, 3?

WhatOccupancyTable 16-K

?Is

Bldg. Height< 73 m

Use Dynamic Analysis

Use Static Analysis

1, 2, 3

3 or 4

Yes

No

Yes

4, 5

1

No

Yes

No

2

Building Configuration

• Plan Structural Irregularities (1997 UBC Table 16-M)» Torsional irregularity» Re-entrant corners» Diaphragm discontinuity» Out-of-plane offsets» Nonparallel systems

132



46

Building Configuration• Vertical Structural Irregularities (1997 UBC

Table 16-L)» Stiffness irregularity – soft story» Weight (mass) irregularity» Vertical geometric irregularity» In-plane discontinuity in vertical lateral-force-resisting

elements» Discontinuity in lateral strength – weak story

EXEMPTIONS FROM SEISMIC DESIGN

133



47

1997 UBC Exemption from Seismic Design

1629.1 … One- and two-family dwellings in Seismic Zone 1 need not conform to the provisions of this section.

SIMPLIFIED STATIC LATERAL FORCE PROCEDURE

134



48

1997 UBC Sec. 1629.8.2

• Applicable to following structures in Occupancy Category 4 or 5:» Buildings not more than 3 stories in

height excluding basements, that use light-frame construction

» Other buildings not more than 2 stories in height excluding basements

1997 UBC Sec. 1630.2.3.2

• Seismic Base Shear, V (Eq. 30-11):

V = 3.0 Ca W / R

135



49

1997 UBC Sec. 1630.2.3.3

• Vertical Distribution (Eq. 30-12)

Fx = 3.0 Ca wx / R

1997 UBC Sec. 1630.2.3.4

• Where used, ΔM shall be taken equal to 0.01 times the story height of all stories

136



50



137

1



Easy, Step-by-Step Determination of

Design Base Shear1997 UBC

138

2



1997 UBC Division IV: Earthquake DesignSection Title Page

1626 General 2-91627 Definitions 2-91628 Symbols and Notation 2-101629 Criteria Selection 2-111630 Minimum Design Lateral Forces and Related

Effects2-13

1631 Dynamic Analysis Procedures 2-161632 Lateral Forces on Elements of Structures,

Nonstructural Components and Equipment Supported by Structures

2-18

1633 Detailed Systems Design Requirements 2-191634 Nonbuilding Structures 2-21

What is Design Base Shear?

FR

F2

F1

"Base"

V(Design Base Shear)

139

3



STEP 1:DETERMINE SEISMIC ZONE FACTOR,

Z

Dubai: Seismic Zone 2A

UBC Seismic Zones

140

4



UBC Seismic Zones

Appendix Chapter 16

Division III: Seismic Zone Tabulation

Section 1653 – FOR AREAS OUTSIDE THE

U.S.

United Arab Emirates

Abu Dhabi…..Zone 0

Dubai……..…Zone 07

STEP 1:DETERMINE SEISMIC ZONE FACTOR,

Z

Seismic Zone Z1 0.075

2A 0.152B 0.203 0.304 0.40

141

5



STEP 2:DETERMINE IMPORTANCE

FACTOR, I (Table 16-K)Occupancy Category Seismic Importance

Factor, IEssential Facilities 1.25

Hazardous Facilities 1.25

Special Occupancy Structures 1.00

Standard Occupancy Structures

1.00

Miscellaneous Structures 1.00

STEP 3:DETERMINE IF STATIC FORCE

PROCEDURE is OK

CED – Structural Design Guidelines

VS.

1997 UBC

142

6




PROCEDURE is OK

• CED Section 3.2

All structures and buildings exceeding 12

stories in height shall be analyzed by

employing Response Spectrum Analysis


PROCEDURE is OK (97 UBC Section 1629.8)

What SeismicZone ? Does building have

an irregularity asdescribed in Item 1, 2or 3 of Table 16-L ?

WhatOccupancy ?

Table 16-K

IsBuilding Height

< 73.2 m ?

Is No. ofStories ≤ 5

and Ht ≤ 19.8 m ?USE DYNAMIC ANALYSIS

USE STATIC ANALYSIS



WhatOccupancy ?

Table 16-K

IsBuilding Height

< 73.2 m ?



USE STATIC ANALYSIS

143

7




PROCEDURE is OK1. Stiffness Irregularity

- Soft Story2. Weight (Mass)

Irregularity3. Vertical Geometric

Irregularity

Stiff Resisting Elements

Soft

Heavy Mass

“Soft Story” Stiffness< 70% Story Stiffness

Above or< 80% (Avg. Stiffness

of 3 Stories above)

Story Mass > 150% Adjacent Story Mass

Exception: Lighter Roof is Acceptable

Story Dimension > 130% Adjacent Story Dimension

Exception: One-Story Penthouse Acceptable

Irregularities in Items 1, 2 and 3

STEP 4:DETERMINE SOIL PROFILE TYPE

Section 1636 and Table 16-J

Soil Profile Type Soil Profile DescriptionSA Hard rockSB RockSC Very dense soil and soft rockSD Stiff soil profile SE Soft soil profileSF Soil requiring site-specific evaluation.

See UBC Section 1629.3.1.

144

8



STEP 4:DETERMINE SOIL PROFILE TYPE

Section 1629.3

EXCEPTION: When the soil properties

are not known in sufficient detail to

determine the soil profile type, Type

SD shall be used….

STEP 5:DETERMINE Ca and Cv

Ca• Function of Z and Soil Profile Type

• Represents site-dependent effective

peak acceleration at grade.

• Used in base shear equation

145

9




Spec

tral

Acc

eler

atio

n

Period (T)

Ca

Response Spectrum


Soil ProfileType

Seismic Zone Factor, ZZ = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4

SA 0.06 0.12 0.16 0.24 0.32Na

SB 0.08 0.15 0.20 0.30 0.40Na

SC 0.09 0.18 0.24 0.33 0.40Na

SD 0.12 0.22 0.28 0.36 0.44Na

SE 0.19 0.30 0.34 0.36 0.36Na

SF See Footnote 11 Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients for Soil Profile Type SF.

SEISMIC COEFFICIENT Ca

146

10




Cv• Function of Z and Soil Profile Type

• Represents the value of acceleration

response at a 1.0 second period.

• Cv is significantly > Z for soft soil

sites.


Spec

tral

Acc

eler

atio

n

Period (T)

Cv

T = 1.0 second

RESPONSE SPECTRUM

147

11




SEISMIC COEFFICIENT CV

Soil ProfileType

Seismic Zone Factor, ZZ = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4

SA 0.06 0.12 0.16 0.24 0.32Na

SB 0.08 0.15 0.20 0.30 0.40Na

SC 0.13 0.25 0.32 0.45 0.56Na

SD 0.18 0.32 0.40 0.54 0.64Na

SE 0.26 0.50 0.64 0.84 0.96Na

SF See Footnote 11 Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients for Soil Profile Type SF.

STEP 6:DETERMINE BUILDING PERIOD, T

Section 1630.2.2:

T = Ct (hn) ¾

148

12



STEP 6:DETERMINE BUILDING PERIOD, T

*Ct for structures with concrete or masonry shear walls may alternatively be computed using UBC formula (30-9).

Alternative methods for calculating the period of a structure are found in UBC Section 1630.2.2. Periods may be computed by any rationalprocedure that is in conformance with the principles of mechanics. Rationally computed period may not be taken any larger than 1.3 times the period given by the above formula in Zone 4, or 1.4 times the period obtained from the above formula in Zones 1, 2 and 3.

Structural System CtSteel moment resisting frames 0.0835

Reinforced concrete moment resisting frame and eccentrically braced frames

0.0731

All other systems 0.0488*

STEP 7:DETERMINE SYSTEM RESPONSE

FACTOR, R

Table 16-N: STRUCTURAL SYSTEMS1. Bearing Wall System2. Building Frame System3. Moment-Resisting Frame System4. Dual System5. Cantilevered Column Building System6. Shear Wall-Frame Interaction System7. Undefined System

149

13




FACTOR, RBearing Wall

SystemBuilding Frame

SystemMoment-Resisting

Frame System

LateralForces

Gravity Loads LateralForces

LateralForces

Gravity Loads Gravity Loads

Stiff Resisting Elements…Shearwalls or Braced Frames



FACTOR, RDual System Cantilevered Column

Building SystemShear Wall-FrameInteraction System

LateralForces

LateralForcesGravity Loads

Gravity Loads

Stiff Resisting Elements…Shearwalls or BracedFrames (See Section

1629.6.5 for requirements)

Zero MomentRestraint

FixedBase

Concrete only

150

14



STEP 8:Calculate W

Seismic Dead Load, W, per Section 1630.1.1:

Description LoadWarehouses 25% Live LoadBuildings with Partitions

Min. 0.48 kN/m2

Snow Load > 1.44 kN/m2, includePermanent Equipment 100% Dead Load

STEP 9:Calculate Design Base Shear

Section 1630.2…Description and Equation Equation No.“Long Period” Structures: 30-4

“Short Period” Structures: 30-5

Design Base Shear Minimum: 30-6

WTRIC

V v=

WR

IC.V a52=

WIC.V a110=

151

15



STEP 9:Calculate Design Base Shear

Design Response SpectrumD

esig

n B

ase

shea

r

Period (T)Ts

“Short period”structures

“Long period”structures

WR

IC.V a52=

WTRIC

V v=

minV

a

vs C.

CT

52=

STEP 10:Distribute Design Base Shear

Section 1630.5( )

∑−=

iixx

tx hwhwFVF When T ≤ 0.7 sec, Ft = 0

When T > 0.7 sec, Ft = 0.07TV ≤ 0.25V

Ft = 0.07TV n

hn

hx

Fx x wx

V

i i

152

16



EXAMPLE

SKGA California Office Relocated

to Dubai, “Regular”

Plan Dimension of Example Building

9.14 m

7.62 m

153

17



Elevation of Office

2.74 m

2.74 m

2.74 m

1

2

3

Design Data

• Building Location

Dubai (Seismic Zone: 2A)

154

18



EXAMPLE: Step 1

Step 1: Determine Seismic Zone Factor

Z = 0.15 (Seismic Zone: 2A)

EXAMPLE: Step 2

Step 2: Determine Importance Factor

I = 1.0 (Standard Occupancy Structure in Table 16-K)

155

19



EXAMPLE: Step 3Step 3: Determine If Static Procedure is OK



WhatOccupancy ?

Table 16-K

IsBuilding Height

< 73.2 m ?



USE STATIC ANALYSIS



WhatOccupancy ?

Table 16-K

IsBuilding Height

< 73.2 m ?



USE STATIC ANALYSIS

EXAMPLE: Step 4

Step 4: Determine Soil Profile Type

Assume SD Soil (Stiff Soil Profile)

156

20



EXAMPLE: Step 5

Step 5: Determine Ca and Cv

Soil Profile

Type

Seismic Zone Factor, Z

Z = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4

SA 0.06 0.12 0.16 0.24 0.32Na

SB 0.08 0.15 0.20 0.30 0.40Na

SC 0.09 0.18 0.24 0.33 0.40Na

SD 0.12 0.22 0.28 0.36 0.44Na

SE 0.19 0.30 0.34 0.36 0.36Na

SF See Footnote 1

SEISMIC COEFFICIENT Ca

EXAMPLE: Step 5

Step 5: Determine Ca and Cv

SEISMIC COEFFICIENT CV

Soil Profile

Type

Seismic Zone Factor, Z

Z = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4

SA 0.06 0.12 0.16 0.24 0.32Na

SB 0.08 0.15 0.20 0.30 0.40Na

SC 0.13 0.25 0.32 0.45 0.56Na

SD 0.18 0.32 0.40 0.54 0.64Na

SE 0.26 0.50 0.64 0.84 0.96Na

SF See Footnote 1

157

21



EXAMPLE: Step 6

Step 6: Determine Building Period T

0.2 m

9.14 m

7.62 m 0.2 m

EXAMPLE: Step 6

Direction 1:Direction of lateral seismic load is parallel to the longer

dimension of the shear wall (9.14 m)

ΣAe = 9.14 × 0.2 × 2 + (7.62-0.4) ×0.2 ×2 = 6.54 m2

De = 9.14 (the length of a shear wall in loading direction)

De/hn = 9.14 / 8.22 = 1.11 > 0.9, therefore De/hn = 0.9

Ac = ΣAe [0.2 + (De/hn)2] = 6.54 × [0.2+0.92] = 6.61 m2

Ct = 0.0743 / Ac0.5 = 0.0743 / (6.61)0.5 = 0.0289

T = Ct (hn)0.75 = 0.0289 × (8.22)0.75 = 0.14 sec

158

22



EXAMPLE: Step 6

Direction 2:Direction of lateral seismic load is parallel to the shorter

dimension of the shear wall (7.62 m)

ΣAe = 9.14 × 0.2 × 2 + (7.62-0.4) ×0.2 ×2 = 6.54 m2

De = 7.62 (the length of a shear wall in loading direction)De/hn = 7.62 / 8.22 = 0.927 > 0.9, therefore De/hn = 0.9Ac = ΣAe [0.2 + (De/hn)2] = 6.54 × [0.2+0.92] = 6.61 m2

Ct = 0.0743 / Ac0.5 = 0.0743 / (6.61)0.5 = 0.0289

T = Ct (hn)0.75 = 0.0289 × (8.22)0.75 = 0.14 sec

Therefore, T = 0.14 sec in both directions

EXAMPLE: Step 7

Step 7: Determine System Response FactorBasic Structural

SystemsLateral-Force-Resisting System Description R

1. Bearing Wall System 1. Light-framed walls with shear panels

a. Wood Structural panel walls for structures three stories or less 5.5

b. All other light-framed walls 4.5

2. Shear walls

a. Concrete 4.5

b. Masonry 4.5

3. Light steel-framed bearing walls with tension-only bracing 2.8

4. Braced frames where bracing carries gravity load

a. Steel 4.4

b. Concrete 2.8

c. Heavy timber 2.8

Gravity LoadLateralForces


159

23



EXAMPLE: Step 8

Step 8: Calculate W

Level Story weight, wx (kN)3 (Roof) 510

2 6811 681Σ 1872

EXAMPLE: Step 9

Step 9: Calculate design base shear

Ts = Cv/(2.5 × Ca) = 0.32/(2.5 × 0.22) = 0.582 sec > T (= 0.14 sec)

Vmin = 0.11 ×Ca × I × W = 0.11 × 0.22 ×1.0 × 1872 = 45.3 kN

V = (2.5 × Ca × I)/R × W = (2.5 × 0.22 ×1.0)/4.5 × 1872 = 228.8 kN > Vmin

160

24



Seismic Design Forces

Step 10: Distribute design base shear

Story hx (m) wx (kN) hxwx(m-kN)

Fx (kN)

3 (Roof) 8.22 510.0 4192.2 97.97

2 5.48 681.0 3731.9 87.22

1 2.74 681.0 1865.9 43.61

Σ 1872.0 9790.0 228.8

Fx = (wxhx)/(Σwihi) × V when T ≤ 0.7 sec

EXAMPLE: Step 10

97.97 kN

87.22 kN

43.61 kN 1

2

3

161

1



Computation of Design Seismic Forces




A

B

C

D

1 2 3 4 5 6

N

7 87.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m

6.71

m6.

71 m

6.71

m

162

2




11@

3.66

m=

40.2

6 m

10

11

12

7

8

9

4

5

6

1

2

3

4.88

m

Design Data

• Building LocationDubai (Seismic Zone 2A)


’ = 30 MPa, wc = 23.55 KN/m3


163

3



Design Data


floor = 2394 N/m2




Design Data

• Seismic Design DataZone 2A: Z = 0.15

Soil Profile Type: SD (stiff soil profile; UBC Table 16-J)

For Occupancy Category 4, I = 1.0 (UBC Table 16-K)

164

4



Design Data


Slab: 205 mm

Beams: 560 × 560 mm




Values of Ca as Function of Soil Profile Type and Z (Table 16-Q)

1: Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients for Soil Profile Type SF.

See Footnote 1SF

0.36Na0.360.340.300.19SE

0.44Na0.360.280.220.12SD

0.40Na0.330.240.180.09SC

0.40Na0.300.200.150.08SB

0.32Na0.240.160.120.06SA

Z = 0.4Z = 0.3Z = 0.2Z = 0.15Z = 0.075Seismic Zone Factor, ZSoil

Profile Type

165

5



Values of Cv as Function of Soil Profile Type and Z (Table 16-R)

1: Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients for Soil Profile Type SF.

See Footnote 1SF

0.96Nv0.840.640.500.26SE

0.64Nv0.540.400.320.18SD

0.56Nv0.450.320.250.13SC

0.40Nv0.300.200.150.08SB

0.32Nv0.240.160.120.06SA

Z = 0.4Z = 0.3Z = 0.2Z = 0.15Z = 0.075Seismic Zone Factor, ZSoil

Profile Type

Seismic ForcesThe equivalent lateral force procedure of 1997 UBC Section 1630.2 is used to compute the seismic base shear. In a given direction, V is determined by UBC Eqs. 30-4 – 30-7:

V = Cs W

where Cs is the seismic response coefficient determined in accordance with UBC 1630.2.1 and W is the total dead load of the structure and applicable portions of other loads as indicated in UBC 1630.1.1. For the member sizes and superimposed dead loads, W = 121,107 kN.

166

6



Seismic Forces in N-S Direction

In the N-S direction, a dual system is utilized.

As a minimum, the dual system must have

intermediate reinforced concrete moment

frames and ordinary reinforced concrete shear

walls in a building in Zone 2A. For this system,

the response modification coefficient R = 6.5

(see UBC Table 16-N).

Seismic Forces in N-S Direction• Approximate period (Ta)

The fundamental period of the building T is determined in accordance with UBC 1630.2.2. In lieu of a more exact analysis, an approximate fundamental period Ta is computed by UBC Eq. 30-8 for the dual system:

Building height hn = 45.14 m Approximate period parameter Ct = 0.0488 (1630.2.2 Method A)Period Ta = Cthn

3/4 = 0.0488 × (45.14)3/4 = 0.85 sec

No further refinement of the period is made in this example.

167

7




• Seismic base shear (V)

The seismic response coefficient Cs is determined by UBC Eq. 30-4:

Cs = CvI / RT= 0.32x1 / (6.5x0.85)= 0.058


The value of Cs need not exceed that from UBC Eq. 30-5:

Cs = 2.5CaI / R = 2.5x0.22 / 6.5 = 0.085

Also, Cs shall not be less than the value given by UBC Eq. 30-6:

Cs = 0.11CaI = 0.024

168

8




Thus, the value of Cs from UBC Eq. 30-4 governs and the base shear in the N-S direction is:

V = 0.058 W = 0.058 × 121,107 = 7024 kN

Seismic Forces in N-S Direction• Vertical distribution of seismic forces

The total base shear is distributed over the height of the building in conformance with UBC Eqs. 30-14 and 30-15:

where Fx is the lateral force induced at level x, wx and wi are the portions of W assigned to levels x or i.

∑=

−= n

iii

xxtx

hw

hwFVF

1

)(

sec 0.7 T for 25.007.0 >≤= VTVFt

Concentrated force Ft is applied at the top floor and accounts for

the higher mode effects in tall buildings

169

9




• Vertical distribution of seismic forces

For T = 0.85 sec, Ft = 0.07x0.85x7024.2 = 418 kN

V – Ft = 7024 - 418 = 6606 kN

Seismic Forces in N-S DirectionSeismic Forces and Story Shears in N-S Direction

Story Shear, Vx (kN)

Lateral Force, Fx+Ft (kN)wxhx

Height, hx (m)

Story Weights, wx

(kN)Level

70243,004,357121107Σ

702411150,6314.8810382.151.00691219086,5938.5310146.392.006722272123,70412.1910146.393.006450353160,81615.8510146.394.006096435197,92719.5110146.395.005661516235,03923.1610146.396.005144598272,15026.8210146.397.004546680309,26230.4810146.398.003866761346,37334.1410146.399.003104843383,48537.8010146.3910.002261924420,59641.4510146.3911.0013361336417,77645.149261.2012.00

170

10



In the E-W direction, a moment-resisting frame system is utilized. As a minimum, this must be an intermediate reinforced concrete moment frame in a building in Zone 2A. For this system, the response modification coefficient R = 5.5 (UBC Table 16-N).

Seismic Forces in E-W Direction


• Approximate period (Ta)The fundamental period of the building T is determined in accordance with UBC 1630.2.2. In lieu of a more exact analysis, an approximate fundamental period Ta is computed by UBC Eq. 30-8 for the intermediate RC moment frame:

Building height hn = 45.14 mApproximate period parameter Ct = 0.0731Period Ta = Cthn

3/4 = 0.0731 × (45.14)3/4 = 1.27 sec

No further refinement of the period is made in this example.

171

11




• Seismic base shear (V)

The seismic response coefficient Cs is determined by UBC Eq. 30-4:

Cs = CvI / RT= 0.32x1 / (5.5x1.27) = 0.05


The value of Cs need not exceed that from UBC Eq. 30-5:

Cs = 2.5CaI / R = 2.5x0.22 / 5.5 = 0.10

Also, Cs shall not be less than the value given by UBC Eq. 30-6:

Cs = 0.11CaI = 0.024

172

12




Thus, the value of Cs from UBC Eq. 30-4 governs and the base shear in the E-Wdirection is:

V = 0.05 W = 0.05 × 121107 = 6055 kN

Seismic Forces in E-W Direction• Vertical distribution of seismic forces

The total base shear is distributed over the height of the building in conformance with UBC Eqs. 30-14 and 30-15:

where Fx is the lateral force induced at level x, wx and wi are the portions of W assigned to levels x or i.

∑=

−= n

iii

xxtx

hw

hwFVF

1

)(

sec 0.7 T for 25.007.0 >≤= VTVFt

Concentrated force Ft is applied at the top floor and accounts for

the higher mode effects in tall buildings

173

13




• Vertical distribution of seismic forces

For T = 1.27 sec, Ft = 0.07x1.27x6055.35 = 538 kN

V – Ft = 6055 – 538 = 5517 kN

Seismic Forces in E-W DirectionSeismic Forces and Story Shears in E-W Direction

Story Shear, Vx (kN)

Lateral Force, Fx+Ft (kN)wxhx

Height, hx

(m)

Story Weights, wx (kN)

Level

60553,004,357121107Σ

60559250,6314.8810382.151.00596215986,5938.5310146.392.005803227123,70412.1910146.393.005576295160,81615.8510146.394.005280363197,92719.5110146.395.004917431235,03923.1610146.396.004485499272,15026.8210146.397.003986567309,26230.4810146.398.003418636346,37334.1410146.399.002782704383,48537.8010146.3910.002077772420,59641.4510146.3911.0013051305417,77645.149261.2012.00

174

14



Method of AnalysisA three-dimensional analysis of the building was performed in the N-S and E-W directions for the seismic forces using SAP2000. In the model, rigid diaphragms were assigned at each floor level, and rigid-end offsets were defined at the ends of the horizontal members so that results were automatically obtained at the faces of the supports. The stiffness properties of the members were input assuming cracked sections. The following cracked section properties were used:

Beams: Ieff = 0.5 IgColumns: Ieff = 0.7 IgShear walls: Ieff = 0.5 Ig

where Ig is the gross moment of inertia of the section. P-delta effect were also considered in the analysis.

Method of Analysis

In accordance with UBC 1630.6, the center of mass was displaced each way from its actual location a distance equal to 5 percent of the building dimension perpendicular to the applied forces to account for accidental torsion in seismic design.

175

15



Method of Analysis

In a dual system, an additional safeguard is provided by requiring that moment-resisting frames be capable of resisting at least 25% of the design forces without the benefit of shear walls (UBC 1629.6.5). Thus, the building was also analyzed in the N-S direction using 25% of the design forces without the shear walls present, including torsional effects.

Method of AnalysisResults of 3-D Analysis under Seismic Force in E-W Direction for

Frame C

347-347347-348348-3473551

356-356356-357357-3483532

349-348349-350351-3393453

335-335335-337337-3233284

315-315315-317317-3013065

291-291291-294294-2762806

263-263263-265266-2462507

231-229231-233233-2132178

194-194194-196197-1761799

153-153153-156156-13513710

110-110110-112112-909111

65-6464-6768-485112

959596961

989898962

969697943

929293894

878787835

808081766

727273687

636464598

535354499

4242433710

3030312511

1818191412

Bending Moment in Beams (m-kN) Shear Forces in Beams (kN)

176

16



Method of AnalysisResults of 3-D Analysis under Seismic Force in E-W Direction for Frame C

747747537517-286-286-207-1581351351256157-333-333-246-1592326326243165-340-340-252-1713307308227144-335-336-247-1674285287210134-324-325-238-1625261262192118-308-309-225-1546232233170103-288-289-210-144720020114685-264-265-191-133816416511865-236-237-170-12091241258843-204-205-145-1031078815622-166-167-118-9011383922-6-127-129-84-5112

2252251621471

2212211621022

2152151601093

2072081531004

197197145955

184184135886

168169123807

150150109708

12913093609

106107754710

7980563611

5354341512

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

-7-2117861

-6-1546892

-6-1145933

-6-794994

-5-504105

-5-253276

-4-62507

-391828

-3181249

-2237510

-1223811

0.0-1111312

Bending Moment in Columns (m-kN)



Method of AnalysisResults of 3-D Analysis under Seismic Force in N-S Direction for

Frame 4

84

118

142

159

170

175

176

173

168

161

160

118

122

122

119

114

107

98

88

76

63

48

33

18

-81

-113

-135

-150

-159

-162

-162

-158

-152

-144

-142

-104

120-119841

125-1211152

123-1171383

118-1121534

112-1051625

104-961666

95-861657

84-751618

71-621559

56-4714710

42-3314511

26-1710912

412841271

433941382

424740453

415338504

385636535

365833546

325829547

295726538

245621519

1953164810

1453114711

93963512

Bending Moment in Beams (m-kN) Shear Forces in Beams (kN)

Italic denotes results with 25% of design base shear applied to the frame.

177

17



Method of AnalysisResults of 3-D Analysis under Seismic Force in N-S Direction for

Frame 4

21712014981-91-27-50-911211305470-112-74-53-2921061435477-110-104-55-4731031564981-110-128-54-594951624582-106-144-53-695871644082-100-155-50-756781623579-94-156-47-797671572976-861-61-43-798551502371-76-158-39-779421431667-65-156-34-761027131961-51-132-28-651115147167-42-214-18-10512

693245201

826638322

768038403

749236454

719934495

6610332506

6010429517

5410326508

469922489

3896174610

2785134111

2011795612

24

24

23

21

19

17

15

13

10

7

5

453395551

442985282

432574903

412174454

381793955

341433426

301102887

26802348

21551819

153413110

10178311

2463512

Bending Moment in Columns (m-kN)



360563,925-46,34501315947,057-35,50202287336,538-26,02903257627,309-17,88604228719,335-10,97005199212,523-52360616866841-67207136222862694081016-1103481809617-32735530010277-40475060011632-36111296012

BottomTopShear Force

(kN)Bending Moment (m – kN)Axial Forces

(kips)Level

Results of 3-D Analysis under Seismic Forces in N-S Direction for Wall on Column Line 7

178

18



Story Drift and P-Delta Effects

• Story drift determination

ΔM = 0.7RΔs

Story Drift = ΔM(x) - ΔM(x-1)

Story Drift and P-Delta EffectsLateral Displacements and Interstory Drifts due to Seismic Forces

in N-S and E-W Directions

64.764.716.813.713.73163.1127.833.218.231.97263.6191.449.723.755.512.2361.2252.665.627.382.818.2458.2310.880.729.6112.424.7554.2365.094.831.4143.831.6649.7414.7107.731.9175.638.6744.2458.9119.231.4207.045.5838.2497.1129.130.9238.052.3931.1528.2137.230.0268.058.91023.5551.8143.328.7296.765.21115.4567.2147.326.8323.571.112

Story Drift (mm)

ΔM

(mm)

Δs

(mm)

Story Drift (mm)

ΔM

(mm)

Δs

(mm)

E-W DirectionN-S DirectionStory

179

19




The design story drifts must not exceed the

allowable story drift from 1997 UBC 1630.10.2 -

for Occupancy Category II, Δa = 0.020hsx where

hsx is the story height below level x. Thus, for

the 12-ft story heights, Δa = 0.020 × 3.66 × 1000 =

73.2 mm, and for the 4.88-m story height at the

first level, Δa = 97.5 mm. It is evident the limits

are satisfied in both directions.


• P-delta effects

As noted above, P-delta effects were automatically considered in the analysis using SAP2000. The provisions of P-delta effects are given in 1997 UBC 1630.1.3.

180

20





181

1



Seismic Details for Reinforced Concrete Buildings

in Moderate Seismic Applications



Applicability of Requirements

ACI 318-05 Chapter 21

182

2



Flexural Members

Beams of Intermediate Moment Frames –Longitudinal Reinforcement

(10.3.5, 10.5.1, 21.12.4.1)

M-n,l

M+n,l ≥ M-

n,l/3

M-n,r

M+n,r ≥ M-

n,r/3

M-n or M+

n ≥ (max. Mn at either joint)/5

ρmin = 0.25√f’c/fy, 1.4/fy

εt ≥ 0.004

Sect. 7.13

183

3



Beams of Intermediate Moment Frames–Transverse Reinforcement

(21.12.3, 21.12.4.2, 21.12.4.3)

≤ 50mm Stirrups

Trans. reinf. based on Mnand factored tributary gravity load

s ≤ d/2≥ 2h

h

s ≤

d/48 × smallest long. bar dia.24 × hoop bar dia.300 mm

Hoops

Hoop Reinforcement

(21.3.3.6)

(≥ 75 mm)

184

4



Intermediate Moment Frames –Two-way Slabs

(21.12.6)

c2 c2 + 3h

½ Middle strip

½ Middle strip

Column stripAll reinforcement necessaryto resist Ms to be placed incolumn strip

h = slab thickness

Note: Applies to both top and bottom reinforcement

As ≥Reinforcement necessary to resist γfMs

Reinforcement in column strip/2

185

5



Banded Column Strip Reinforcement

21.10.6.5, 21.10.6.7 -Longitudinal Reinforcement in

Column Strip of Slab

186

6



Longitudinal Reinforcement in Middle Strip of Slab

21.12.6.8 – Shear Strength of Two-Way Slabs without Beams in Intermediate Moment Frames

• Slab-column frames are susceptible to punching-shear failures during earthquakes if the shear stresses due to gravity loads are high

187

7



• At the critical sections for columns defined in 11.12.1.2, two-way shear caused by factored gravity loads shall not exceed 0.4φVc, where Vc shall be calculated as defined in 11.12.2.1 for nonprestressed slabs and 11.12.2.2 for prestressed slabs


• It shall be permitted to waive this requirements if the contribution of the earthquake-induced factored two-way shear stress transferred by eccentricity of shear in accordance with 11.12.6.1 and 11.12.6.2 at the point of maximum stress does not exceed one-half of the stress φVn

permitted by 11.12.6.2


188

8



Members Subjected to Bending and Axial Load

Columns of Intermediate Moment Frames– Transverse Reinforcement

(21.12.3, 21.12.5)

s to conform to 7.10 and 11.5.5.1

h2

h1

≤ so/2Joint reinf.per 11.11.2

Trans. reinf. based on Mn and factored tributary gravity load

so ≤

8 × smallest long. bar dia.24 × hoop bar dia.0.5 × min. (h1 or h2)300 mm

lo

lo ≥

Larger of h1 or h2

Clear span/6450 mm

Hoops

189

9





190

1



Design of Typical Structural Members




A

B

C

D

1 2 3 4 5 6

N

7 87.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m 7.92 m

6.71

m6.

71 m

6.71

m

191

2




11@

3.66

m=

40.2

6 m

10

11

12

7

8

9

4

5

6

1

2

3

4.88

m

Design Data

• Building LocationDubai (Seismic Zone 2A)


’ = 30 MPa, wc = 23.55 KN/m3


192

3



Design Data


floor = 2394 N/m2




Design Data

• Seismic Design DataZone 2A: Z = 0.15

Soil Profile Type: SD (stiff soil profile; UBC Table 16-J)

For Occupancy Category 4, I = 1.0 (UBC Table 16-K)

193

4



Design Data


Slab: 205 mm

Beams: 560 × 560 mm




Load CombinationThe seismic load effect E for use in the basic strength design load combinations is the combined effect of horizontal and vertical earthquake-induced forces. The E for use in Eq. (9-5) is computed by UBC Eq. 30-1:

E = ρEh + Ev

where Eh = effect of horizontal seismic forcesEv = effect of vertical seismic forcesρ = redundancy factor

= 1.0 for structures in Seismic Zones 1 and 2

194

5



Load Combination

where the effects of gravity and seismic ground motion are additive:

E = ρ Eh + 0.5 Ca I D

Load Combination

Similarly, where the effects of gravity and seismic ground motion counteract:

E = Eh - Ev = ρ Eh - 0.5 Ca I D

195

6



Load Combination

Substituting Ca = 0.22 and ρ = 1.0 into the equations for E, and then substituting E into Eqs. (12-5) and (12-6) above results in the following:

U = 1.2D + 0.5L + 1.0Eh + (0.5 × 0.22)D= 1.31D + 0.5L + Eh

U = 0.9D +1.0 Eh - (0.5 × 0.22)D = 0.79D + Eh

Beam C4 – C5

Summary of Design Bending Moments and Shear Forces for Beam C4-C5 at the Second Floor Level (SDC C)

Wind (W)

Seismic (QE)

Live (L)

Dead (D)

Load Case

± 98.0± 356support± 2.8± 33Support

25.4Midspan

28.0-37.0Support

94.6Midspan

104.3-137.6Support

Shear Force (kN)

Bending Moment (m-kN)Location

196

7



Beam C4 – C5Summary of Design Bending Moments and Shear Forces for Beam C4-C5

at the Second Floor Level (SDC C)

Shear Force (KN)

Bending Moment (m –KN)

LocationLoad combination

-16247Support0.79D - QE

249-555Support1.31D + 0.5L + QE

89-71Support0.9D – 1.6W144-236Support1.2D + 0.5L + 1.6W172-251Support1.2D + 1.6L + 0.8W

154.2Midspan167.0-224.3Support1.2D + 1.6L

132.4Midspan146.0-192.6Support1.4D

Beam C4 – C5

1. Flexural designThe factored axial load on the member, which is negligible, is less than Agfc

’/10; thus, the provisions of ACI 21.12.4 for beams must be satisfied. All other applicable provisions in Chapters 1 through 18 of ACI 318-05 are to be satisfied as well.

197

8



Beam C4 – C5

Minimum flexural reinforcement:

(governs) mm935415

4955604.1

f

db4.1

mm914 415

4955603025.0

f

dbf25.0A

2

y

w

2

y

wcmins,

=××

==

=××

=′

=

Beam C4 – C5

Maximum flexural reinforcement:

2

y

c1maxs,

mm 6204

0.0070.003

415495560300.850.85

0.0040.0030.003

f

dwbf0.85βA

=

×××××

=

+

′=

198

9



Beam C4 – C5Required Flexural Reinforcement for Beam C4-C5 at the

Second Floor Level (SDC C)

2073 - No 221161154.2Midspan

2073 - No 221161

5415 – No 293235- 461.4Support

φ Mn(m-kN)

ReinforcementAs (mm2)Mu(m-kN)

Location

Beam C4 – C5

ACI 21.12.4.1: the positive moment

strength at the face of the joint be greater

than or equal to 33% of the negative

moment strength at that location. This is

satisfied, since 207 m-KN > 541/3 = 180.3

m-KN.

199

10



Beam C4 – C5

The negative or positive moment strength at any section along the length of the member must be greater than or equal to 20% of the maximum moment strength provided at the face of either joint.

541/5 = 108.2 m-KNProviding 2- No. 29 bars ( = 230 m-KN) or 2- No. 22 bars ( = 140 m-KN) satisfies this provision.

Minimum of 2 – No. 29 bars (= 1294 mm2) or 3 – No. 22 bars (= 1161 mm2) must be provided to satisfy minimum reinforcement requirement of ACI 10.5

Beam C4 – C5

2. Shear designShear demand from nominal flexural capacity

Vu = (541 + 207) / 7.26 = 103.03 kNShear demand from gravity load

Wu =1.31wD + 0.5wL

= 1.31 × 28.724 + 0.5 × 7.721 = 41.49 kN/mVu = wuln / 2 = (41.49 × 7.26) / 2 = 150.61 kN

Vu = 103.03 + 150.61 = 253.64 kN

200

11



Beam C4 – C5

The nominal shear strength provided by

concrete (Vc)

Vc = 0.17 × (fc’)0.5 × bw × d Eq. (11-3)

= 0.17 × (30)0.5 × 560 × 495 / 1000 = 258.1 kN

Beam C4 – C5Vu (= 253.6 KN) > φVc (0.75 ×258.1 = 193.6 kN)

Provide shear reinforcement in accordance with ACI 11.5.6. Assuming No. 10 hoops, the required spacing s is determined by Eq. (11-15):

s = (Av × fy × d) / Vs

= (142 ×415 ×495) / (253,600/0.75 –258,100)= 364.5 mm

201

12



Beam C4 – C5ACI 21.12.4.2: the maximum spacing of hoops over the length 2h = 2 × 560 = 1120 mm from the face of the support at each end of the member is the smallest of the following:

(1) d / 4 = 495 / 4 = 123.8 mm (governs)(2) 8 (diameter of smallest longitudinal bar)

= 8 × 22.2 = 177.6 mm(3) 24 (diameter of hoop bar) = 24 × 9.5 = 228 mm(4) 305 mm

Beam C4 – C5

Use 10-No. 10 hoops at each end of the beam spaced at 120 mm on center with the first stirrup located 50 mm from the face of the support.

For the remainder of the beam, the maximum stirrup spacing is d / 2 = 247.5 (ACI 21.12.4.3). Use No. 10 stirrups @ 240 mm for the remainder of the beam.

202

13



Beam C4 – C5

660 mm

5-No.29

10-No.10 hoops @ 120mm

1830 mm 5-No.29 5-No.29

660 mm

560 mm

50 mm

7264 mm

3-No.22No.10 hoops @ 240mm

Design of Column C4 at 2nd Floor

-221-35137120.79D – Eh

221 35164331.31D + 0.5L + Eh

-11-664224N-S-11-534229E-W

0.9D – 1.6W

11665921N-S11535916E-W

1.2D + 0.5L + 1.6W

6336528N-S5266525E-W

1.2D + 1.6L + 0.8W

0065251.2D + 1.6L0065791.4D

Load Combination± 221± 351± 0.1E-WSeismic (QE)± 6.9± 41± 3.0N-S± 6.6± 330E-W

Wind (W)

00554Live (L) (reduced)004699Dead (D)

Shear Force(kips)

Bending Moment(ft-kips)

Axial Force(kips)Load Case

203

14



Design of Column C4Design for Axial Force and BendingBased on the governing load combinations in the table, a 660 × 660 mm column with 12-No. 32 bars (ρg = 2.25%) is adequate for column C4 supporting the second floor level. The interaction diagram for this column is given below. Slenderness effects need not be considered, since P-delta effects were included in the analysis. Also, the provided reinforcement ratio is within the allowable range of 1% and 8% (ACI 10.9.1).

Design of Column C4

0

2000

4000

6000

8000

10000

12000

14000

16000

0 250 500 750 1000 1250 1500 1750 2000


Axi

al F

orce

(kN

)

204

15



ACI 7.6.3 requires that the clear distance between longitudinal bars shall not be less than

1.5db = 1.5 × 32.3 = 48.5 mm

nor 40mm. In this case, assuming No. 10 hoops and ties, the clear distance is equal to the following:

Design of Column C4

O.K.mm 5.48mm 9.1433.323

23.325.9402660

>=−⎟⎠⎞

⎜⎝⎛ ++−

Design of Column C4

Design for Shear

Columns in intermediate moment frames must satisfy the shear requirements in ACI 21.12.3. The first of the two options in that section is utilized here to determine the design shear strength:

The sum of the shear associated with development of nominal moment strengths of the member at each restrained end of the clear span and the shear calculated for the factored gravity loads

205

16



Design of Column C4

Design for Shear

Because the column is at the 2nd floor, and the moment at any column end cannot exceed the average of the nominal moment strengths of the beams framing into that end, shear demand from the seismic forces is calculated from the nominal flexural strengths of the beams.

Design of Column C4

Design for Shear

Vu = (541+207)/3.1 + 0 = 241.3 kN > 221 kN

206

17



Design of Column C4

Design for Shear

kN 531.9 1000/5386603066014

3712000117.0

dbfA14

N117.0V

2

wcg

uc

=××⎟⎟⎠

⎞⎜⎜⎝

⎛

×+=

′⎟⎟⎠

⎞⎜⎜⎝

⎛+=

The shear capacity of the column will be checked in accordance with ACI Eq. (11-4) for members subjected to axial compression:

where Nu = 3712 kN is the smallest axial force corresponding to the largest shear force on the section (see Table) and d = 538 mm was obtained from a strain compatibility analysis.

Design of Column C4

Design for Shear

Since Vu > ΦVc/2 = 0.75x531.9/2 = 199.5 kN, by ACI 318-05 Section 11.5.6.1, minimum transverse reinforcement would be required.

yt

wcmin,v f

sbf062.0A

′=

With No. 10 hoops with one cross-tie, Av = 213 mm2

=> s = 394.4 mm > d/2 = 269 mm (ACI 318 11.5.5.1)

Thus, srequired = 269 mm

207

18



Design of Column C4

Design for Shear

For intermediate moment frames, the requirements in ACI 21.12.5.1 aims primarily to confine the concrete within the core and provide lateral support for the longitudinal reinforcement.

For No. 10 rectangular hoops, the vertical spacing s0

must not exceed the smallest of the following :

Design of Column C4

ACI 21.12.5.1:

• 8 (smallest longitudinal bar diameter) = 8 × 32.3 = 258.4 mm• 24 (hoop bar diameter) = 24 × 9.5 = 228 mm (governs)• Least column dimension/2 = 660/2 = 330 mm• 300 mm

208

19



The governing s0 = 228mm must be provided over a length l0 measured from the joint face, where l0 is the largest of the following:

Design of Column C4

ACI 21.12.5.1:

• Clear span/6 = [3657 - 560]/6 = 516.2 mm• Maximum cross-sectional dimension of member = 660 mm (governs)

• 450 mm

Use 4-No. 10 hoops and crossties @ 220 mm with the first hoop located at 100 mm (< s0/2 = 114 mm; ACI 21.12.5.3) from the joint face above the first floor level and below the second floor level.

For the remainder of the column, tie spacing shall conform to ACI 7.10 and 11.5.5.1. In this case, ACI 11.5.5.1 governs. Use a tie spacing of 250 mm in this region of the column.

Design of Column C4

ACI 21.12.5.1:

209

20



ACI 21.12.5.5 requires that joint reinforcement in intermediate moment frames conform to ACI 11.11.2. Since this beam-column joint is part of the primary seismic-force-resisting system, lateral reinforcement in the joint must not be less than that computed by Eq. (11-13). For No. 10 hoops with one crosstie, the required spacing is:

Design of Column C4

Joint Reinforcement:

mm 394.466030062.0

415)713(bf062.0

fAs

wc

ytv =×

××=

′=

For simpler detailing, continue the 220 mm spacing at the column ends through the joint.

Design of Column C4

Joint Reinforcement:

210

21



Design of Column C4



Wind (W)

± 3604± 63,9250

± 1438± 20,0450

Seismic (QE)

001189Live (L)

0011,951Dead (D)

Shear Forces (kN)


Axial Force (kN)Load Case

211

22





-3604-63,92594410.79D - QE

360463,92516,2501.31D + 0.5L + QE

- 2301-32,07210,7560.9D – 1.6W

230132,07214,9361.2D +0.5L + 1.6W

115016,03616,2441.2D + 1.6L + 0.8W

0016,2441.2D + 1.6L

0016,7311.4D

Shear Force (kN)


Axial Force (kN)

Load combination


1. Shear design

The shear strength of the concrete for wall subjected to axial compression (ACI 11.10.5)

Vc = 0.17 (fc’)0.5 h d

= 0.17 × (30)0.5 × 305 × 5892.8 /1000 = 1673.5 kN

where d = 0.8 lw (= 0.8 × 7366 = 5892.8 mm)

212

23



Shear wall B7 – C7Since φVc (0.75 × 1673.5 = 1255.1 kN) < Vu (= 3604 kN), horizontal shear reinforcement shall be provided in accordance with ACI 11.10.9.

Required bar spacing with 2 layers of No. 13:s = (Av fy d) / Vs = (254 × 415 × 5892.8) / (3,604,000 / 0.75-1,673,500) = 198.3 mm

Note: ACI 14.3.4 requires two layers of reinforcement for walls more than 250 mm thick

Shear wall B7 – C7ACI 11.10.9.3: spacing of horizontal reinforcement shall not exceed (1) lw/5 = 7336/5 =1473.2 mm, (2) 3h = 3 × 305 = 915 mm, or (3) 450 mm.

ACI 11.10.9.2: ratio of horizontal shear reinforcement shall not be less than 0.0025

For 2-No.13 horizontal bar spaced at 450 mm:ρt = (2 ×127) / (305 ×200) = 0.0042 > 0.0025 O.K.

Therefore, use 2-No.13 horizontal bar @ 200 mm

213

24




ACI 11.10.3: Shear strength Vn at any horizontal section must be less than or equal to 0.83 (fc

’)0.5 h d (= 8170.7 kN). In this case,

Vn = Vc + Vs

= 1673.5 + (254 × 415 × 5892.8) / 330= 1883.9 kN < 8170.7 kN O.K.


ACI 11.10.9.4: The ratio of vertical shear reinforcement area to gross concrete area of horizontal section shall not be less than 0.0025 not the value obtained by Eq. (11-32).

ρl = 0.0025 + 0.5 (2.5 – hw / lw) (ρt - 0.0025)= 0.0025 + 0.5 (2.5 – 45 / 7.366) (0.0042 – 0.0025)< 0.0025

Thus, ρl = 0.0025

214

25




ACI 11.10.9.5: spacing of vertical shear reinforcement shall not exceed (1) lw/3 (= 7366/3 = 2455.3 mm), (2) 3h (= 3 × 305 = 915 mm), or (3) 450 mm (governs).

For 2 – No. 13 vertical bar spaced at 330 mm,ρl = (2 ×127) / (305 ×330) = 0.00252 > 0.0025 O.K.

Use 2-No.13 vertical bars @ 330 mm


The provided vertical and horizontal

reinforcement satisfy the requirements of

ACI 14.3.2 and 14.3.3 for minimum ratio of

vertical and horizontal reinforcement to gross

concrete area, respectively, and ACI 14.3.5 for

maximum bar spacing.

215

26




2. Axial force and bending designACI 14.4 requires that walls subjected to axial load or combined flexure and axial load shall be designed as compression members in accordance with ACI 10.2, 10.3, 10.10 through 10.14, 10.17, 14.2, and 14.3 unless the empirical design method of ACI 14.5 or the alternative design method of ACI 14.8 can be used. Clearly, both of these methods cannot be applied in this case, and the wall is designed in accordance with ACI 14.4.


0

10000

20000

30000

40000

50000

60000

70000

80000

0 20000 40000 60000 80000 100000 120000


Axi

al F

orce

(kN

)

216

27






217

1



Code Support Services, Code Change Process, and Plan

Review

Code Support Services

Publications

Seminars

Interpretations

Plan Review Services

Evaluation Services

218

2



Code Support Services: Publications


219

3




1999 Recommended Lateral Force Requirements / Commentary (SEAOC Blue Book)

This book reviews recommended provisions for earthquake-resistant design of structures. Highlights include design requirements, structural tests and inspections, foundations, and recommended modifications to the 1997 UBC for reinforced concrete, reinforced masonry, structural steel, and wood.

http://www.iccsafe.org/dyn/prod/9006S99.html


Handbook to the 1997 Uniform Building Code

The handbook is a completely detailed and illustrated commentary on the 1997 Uniform Building Code, tracing historical background and rationale of the codes through the 1997 edition. The book contains numerous drawings and figures to clarify the application and intent of the code provisions. It is an essential reference for every building official, fire marshal, architect and engineer.

http://www.iccsafe.org/dyn/prod/6074S97.html

220

4





221

5




Code Support Services: Seminars

Company/Organization WebsiteS.K. Ghosh Associates Inc www.skghoshassociates.comAmerican Society of Civil Engineers/ Structural Engineering Institute

www.seinstitute.com

International Code Council www.iccsafe.orgNational Council of Structural Engineers Associations

www.ncsea.com

222

6



Code Support Services: Interpretations

ICC Technical Assistance

• Staff Opinions

• Committee Interpretations (not for time-sensitive issues)

www.iccsafe.org/cs/questions/index.html

Code Support Services: Interpretations

223

7



Code Support Services:Plan Review Services

www.iccsafe.org/cs/techservices/#pr

The Code Official’s Technical Source for Approving New

and Innovative Building Products

Code Support Services: Evaluation Services

224

8




Find the Most Current Reports Online: http://www/icc-es.org


• Click on the Evaluation Reports tab

• Search by » Product » Manufacturer » Report » Number

• No cost to access

225

9



Code Change Process

1997 UBC

2000 IBC2001 Supplement2002 Accumulative Supplement

2003 IBC

Code Change Process

2003 IBC (18 month cycle began)2004 Supplement

2006 IBC2007 Supplement

2009 IBC (expected release date: 2/1/09)

226

10



Code ChangesSubmitted

Code Development Hearing

Public Hearing ResultsPrinted & Distributed

Code ChangesPrinted & Distributed

Public CommentsSought on PublicHearing Results

Public CommentsPrinted & Distributed

Final ActionHearing

Supplement Or NewEdition Published

I-CODE DEVELOPMENTCYCLE

ICC Code Change Process

227

11



Code Change Process

• All aspects of the ICC Code Development Process regulated by published procedures

• Council Policy (CP) 28 – Code Development

• Website link: » http://www.iccsafe.org/news/about/bylaws

.html

Code Change ProcessSteps in a Typical 18 month cycle

• Code changes due. Announcement posted on the website and other media. Anyone can submit a code change

• Staff review» Form and format: Legislative format» Proposals must be based on current text

• Publish» Website: Approx. 90 days prior to Code Development

Hearing» Published: Approx. 60 days prior to Code Development

Hearing

228

12



Code Change Process

WEBCASTING:• Debut at 2002 Code Development

Hearings

• Followed up in all subsequent hearings

• Streaming video and audio

• Internet access on your PC

Code Change Process

• Adopted by reference in the IBC.

• Developed through ANSI-accredited consensus process

• Committee balanced and composed of producers, consumers and regulators.

• Committee ballots revisions.

• Public comment period.

229

13



Code Change Process

• Next edition is ASCE 7-10 which will be adopted in 2012 IBC.

• 2009 IBC will adopt ASCE 7-05.

• ASCE 7-05 has two supplements

» Supplement No. 1» Supplement No. 2

• www.seinstitute.org

Structural Plan Review

Chapter 16: Structural Design Requirements

Chapter 17: Structural Tests and Inspections

Chapter 18: Foundations and Retaining Walls

Chapter 19: Concrete

Chapter 20: Lightweight Metals

230

14




Chapter 21: Masonry

Chapter 22: Steel

Chapter 23: Wood

Chapter 24: Glass and Glazing

Chapter 25: Gypsum Board and Plaster


Step 1: Become familiar with project.

Step 2: Complete structural review.

Step 3: Write review.

Step 4: Critique review.

231

15




Step 1: Become familiar with project.

• Specifications

• Calculations

• Soils Report

• Plans

Structural Plan ReviewStep 2: Complete structural review.

• Identify structural systems and load paths

• Determine loads.

• Check structural members for load effects.

• Check plans and details for clarity and conformity with detailed code requirements based on material of construction.

232

16




Step 3: Write review

• Use checklist.

• Organize comments.

• Provide references: code sections, plan details, sections, grid lines, calculations pages, etc.


233

17




Step 4: Critique review.

234

1



Overview of the Seismic Design Provisions of the 2006 International

Building Code



235

2



Seismic Design ProvisionsIBC Section 1613,

ASCE 7 Chapters 11-23excluding Chapter 14 and Appendix

11A

236

3



ASCE 7-05 Chapters 11-23: Seismic Design

• ASCE 7-02 seismic provisions have been completely reformatted and reorganized.

• Much improved document that should be easier to use and result in more correct and uniform application of seismic requirements.

237

4



ASCE 7-05 Figure 11.4-1: Design Response Spectrum

IBC Design Ground Motion• SS = mapped (MCE) spectral response

acceleration at short periods for Site Class B• S1 = mapped (MCE) spectral response acceleration

at 1.0-second period for Site Class B• ASCE 7 Figs. 22-1 through 22-20/ IBC Figs.

1613.5(1) through 1613.5(14) give contour maps for SS and S1, based on the latest version of USGS seismic hazard maps

• SS and S1 also available at http://eqhazmaps.usgs.gov

238

5



Soil Classification

A. Hard RockB. RockC. Very dense soil or soft rockD. Stiff soilE. Soft soilF. Soils requiring site-specific

evaluations

Soil Classification

• Site Class D must be used when the

soil properties are not known in

sufficient detail, unless the building

official determines that Site Class E or

F is likely to be present at the site

239

6



Values of Fa as Function of Site Conditions and Shaking Intensity

aaaaaF

0.90.91.21.72.5E

1.01.11.21.41.6D

1.01.01.11.21.2C

1.01.01.01.01.0B

0.80.80.80.80.8A

SS ≥

1.25

SS =

1.00

SS =

0.75

SS =

0.50

SS ≤

0.25

SHAKING INTENSITYSOIL

PROFILE

TYPE

Values of Fv as Function of Site Conditions and Shaking Intensity

aaaaaF

2.42.42.83.23.5E

1.51.61.82.02.4D

1.31.41.51.61.7C

1.01.01.01.01.0B

0.80.80.80.80.8A

S1 ≥

0.5

S1 =

0.4

S1 =

0.3

S1 =

0.2S1 ≤ 0.1

SHAKING INTENSITYSOIL

PROFILE

TYPE

240

7



IBC Design Ground Motion

• SMS = soil-modified MCE spectral response

acceleration at short periods

= FaSS

• SM1 = soil-modified MCE spectral response

acceleration at 1.0-second period

= FvS1

IBC Ground Motion

• SDS = design spectral response

acceleration at short periods

= (2/3) SMS

• SD1 = design spectral response

acceleration at 1.0-second period

= (2/3) SM1

241

8



IBC Ground Motion

• Maximum Considered Earthquake

(MCE)– Maximum level of earthquake ground

shaking that is considered reasonable to

design buildings to resist

IBC Ground Motion

• Maximum Considered Earthquake (MCE):» Deterministic earthquakes (in coastal

California)- best estimate of ground motion

from maximum magnitude earthquakes on

seismic faults with high probabilities of

occurrence.

242

9



IBC Ground Motion

• Maximum Considered Earthquake (MCE)– 2% probability of exceedance in 50 years

(approximately 2,500 year return period) where

deterministic approach is not used

ASCE 7-05 Figure 11.4-1: Design Response Spectrum

243

10



TL Map of Contiguous USA

Design Basis: IBC vs. UBC

• Design to avoid collapse in the

Maximum Considered Earthquake,

rather than to provide life safety in

the 500-year return period

earthquake

244

11




Correspondence between Ground Motion Parameters of the UBC and the IBC

Ca/Z of 1997 UBC = Fa of NEHRP/IBC

Cv/Z of 1997 UBC = Fv of NEHRP/IBC

245

12



Correlation of Ground Motion Parameters

SDS = 2.5Ca

(2/3)FaSS = 2.5ZNaFa

SS = (1.5)ZNa(2.5)

Z ≥ 0.4gSDS = 1.00NaFa

(1.00Na for Site Class B)SS = 1.50Nag

SD1 = Cv

(2/3)FvS1 = ZNvFv

S1 = (1.5)ZNv

Z ≥ 0.4gSD1 = 0.4NvFv

(0.4Nv for Site Class B)S1 = 0.6Nvg

Design Spectrum

246

13



UBC Seismic Zones

SDC Based on Short Period Response Acceleration – IBC

DCC0.33g < SDS < 0.50g

DaDaDa0.50g < SDS

CBB0.167g < SDS < 0.33g

AAASDS < 0.167 g

IVIIII or II

OCCUPANCY CATEGORYValues of SDS

247

14



SDC Based on 1 sec. Period Response Acceleration – IBC

DaDaDa0.20g < SD1

DCC0.133g < SD1 < 0.20g

CBB0.067g < SD1 < 0.133g

AAASD1 < 0.067g

IVIIII or II

OCCUPANCY CATEGORYValues of SD1

SDC of IBC (Note a)

FEES1 ≥ 0.75g

IVIIII or II

OCCUPANCY

CATEGORYValue of S1

248

15



ASCE 7-05 Section 11.6 Determination of Seismic Design Category

Can be based on SDS alone, provided• S1 < 0.75• Ta < 0.8Ts• T used to calculate story drift < Ts • Upper-bound design base shear is used in

design• Diaphragms are rigid, or for diaphragms

that are flexible, vertical elements of seismic-force-resisting system spaced at < 40 ft

Areas with S1 > 0.75g

249

16



Ts = SD1/SDSTs = SD1/SDS

SDC of 2006 IBC vs. Seismic Zone of 1997 UBC

C (B)C (B)B (A)AA1Indianapolis, INBB (A)AAA1Wichita, KS

2006 IBC97 UBC

C (B)B (A)AAA2AKansas City, MO

DDCC (C)B2AHonolulu, HIDDD (C)CB3Sacramento, CADD (C)D (C)CB3Fresno, CADDD (C)CB3Chico, CADD (C)CC (C)B1Little Rock, AKCBBB (B)A2BTucson, AZEDCBA

ZoneLOCATION SITE CLASS

250

17



SS ≤ 0.15g and S1 ≤ 0.04g

ASCE 7-05 11.7 Design Requirements for SDC A

11.7.2 Minimum Lateral Force

Fx = 0.01wx

w1

w2

w3

wr

0.01w1

0.01w2

0.01w3

0.01wr

V = 0.01(w1 + w2 + w3 + wr)

251

18



ASCE 7-05 11.7 Design Requirements for SDC A

11.7.3 Load Path Connections

11.7.4 Connection to Supports

11.7.5 Anchorage of Concrete or

Masonry Walls

ASCE 7-05 12.8.1 Design Base Shear

0.6gSwhere(R/I)0.5S

0.01

TTfor(R/I)T

TS

TTfor(R/I)S

(R/I)TSC

WCV

11

L2LD1

LDSD1

S

S

≥≥

≥

>=

≤≤=

=

252

19



ASCE 7-05 12.8 Equivalent Lateral Force Procedure

I/RWSV DS=

T)I/R(WSV D1=

g0.6Swhere,I/RWS0.5V ≥= 1

1

21

T)I/R(WTSV LD=

W0.01V =

LTDSD1s /SST = T,Period

253

20



Concrete Structural Systems in ASCE 7-05 - SDC D, E, F

NLNLNL5 ½38MOMENT RESISTING FRAME SYSTEM using

Special Moment Frames of RC (SMF)

16016016052 ½5 BEARING WALL SYSTEM using

Special RC Shear Walls

10016016052 ½6BUILDING FRAME SYSTEM WITH OMF OF RC using

Special RC Shear walls

NL100

NL100

NL160

5 ½5

2 ½2 ½

76 ½

DUAL SYSTEM usingSpecial RC Shear Walls w/ SMFSpecial RC Shear Walls w/ IMF

FED

Height limitCdΩ0RCONCRETE STRUCTURAL

SYSTEMS - SDC D, E, and F

254

21



Structure Period

Calculated by……1) Approximate Formulae

2) Rational Analysis using structural properties and deformational characteristics of resisting elements in a properly substantiated analysis

ASCE 7-05 12.8.2.1 Approximate Fundamental Period

Ta = Cr hnx

255

22



ASCE 7-05 Table 12.8-2 Values of Approximate Period

Parameters Ct and x

0.90.016

(For SI: 0.044)

Moment resisting frame systems of reinforced concrete in which the frames resist 100 percent of the required seismic force and are not enclosed or adjoined by more rigid components that will prevent the frames from deflecting when subjected to seismic forces

0.80.028

(For SI: 0.068)

Moment resisting frame systems of steel in which the frames resist 100 percent of the required seismic force and are not enclosed or adjoined by more rigid components that will prevent the frames from deflecting when subjected to seismic forces

xCtStructure Type

ASCE 7-05 Table 12.8-2 Values of Approximate Period Parameters Ct and x (cont’d)

0.750.02

(For SI: 0.055)

All other structural systems

0.750.03

(For SI: 0.07)

Eccentrically braced steel frames

xCtStructure Type

256

23



Upper Limit on T by "Rational Analysis"

Note: For drift analysis, upper limit on calculated T does

not apply (Section 12.8.6.2)

1.4

1.4

1.5

1.6

1.7

1.7

≥ 0.4

0.3

0.2

0.15

0.1

≤ 0.05

Coefficient Cu

Design Spectral Response

Acceleration (SD1)

Table 12.8-1 (ASCE 7-05)

Coefficient for Upper Limit on Calculated Period

ASCE 7-05 12.8.3 Vertical Distribution of Seismic Forces

wxhxk

Fx =Σ wihi

kV

k = 1 for T ≤ 0.5 sec

k = 2 for T ≥ 2.5 sec

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Horizontal Shear Distribution

For rigid diaphragms, the seismic design story shear shall be distributed to the various vertical elements of the seismic-force-resisting system in the story under consideration based on the relative lateral stiffnesses of the vertical resisting elements and the diaphragm.

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Accidental Torsion

Where diaphragms are not flexible, in addition to the torsional moment, the design also shall include accidental torsional moments caused by assumed displacement of the center of mass each way from the actual location by a distance equal to 5 percent of the dimension in the direction of applied forces.

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Story Drift

• Δ = δx − δx-1 < Δa

δx = Cd δxe / I

Cd = deflection amplification factor

Allowable Story Drift (Δa ) ASCE 7-05 Table 12.12-1

0.010hsx0.015hsx

0.007hsx0.007hsx

0.010hsx0.010hsx

0.015hsx0.020hsx

IVIII

Occupancy CategoryBuilding

I or II

0.025hsx

Buildings ≤ 4 stories in

height;other than masonry;

Non-structural elements

designed to accommodate

story drift

0.010hsxMasonry cantilever shear wall

buildings

0.007hsxOther masonry shear walls

buildings

0.020hsxAll other buildingshsx = Story height below level x

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Load Combinations

• Basic Load

E = ρQE + 0.2SDSD• Special Load

Em = Ω0QE +

0.2SDSD

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Load Combinations

• Basic LRFD

1.2D + 1.0E + f1L + f2S

0.9D + 1.0E

• Special

1.2D + f1L + Em

0.9D + Em

• Basic ASD

0.6D + 0.7E

D + 0.7E + L + (Lr or S or

R)

• Alternate Basic ASD

D + L + S + E/1.4

0.9D + E/1.4

Section 12.3.4.2Redundancy Factor, ρ, for Seismic

Design Categories D through F

• New redundancy provisions adopted into ASCE 7-05.

• Lack of redundancy is….. when failure of a component is failure of entire system.

• Logical way to determine lack of redundancy is to check whether a component’s failure results in an unacceptable amount of story strength loss or in the development of extreme torsional irregularity.

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In ASCE 7-05, ρ = 1.0 or 1.3, depending on whether or not an individual element can be removed from the lateral-force-resisting-system without:

• Causing the remaining structure to suffer a reduction of story strength of more than 33%, or

• Creating an extreme torsional irregularity.



2nd condition for which ρ = 1.0:

If structure is regular in plan and there are at least 2 bays of seismic force-resisting perimeter framing on each side of the structure in each orthogonal direction at each story resisting > 35% of the base shear.

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ρ = 1.0 for the following:

1. Structures assigned to SDC B and C.

2. Drift calculation and P-delta effects.

3. Design of nonstructural components.

4. Design of nonbuilding structures, not similar to buildings.


Design Categories D through F(cont.)ρ = 1.0 for the following:

5. Design of collector elements, splices and their connections for which load combinations with overstrength are used.

6. Design of members or connections where load combinations with overstrength are required for design.

7. Diaphragm loads determined using Eq. 12.10-1.

8. Structures with damping systems designed in accordance with Chapter 18.

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Seismic Design of RC Structures Using UBC_ACI Provisions

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