EG-1903 Vertical Vessel Foundation_Rev1!06!29-09

EG-1903

Document No.

Vertical Vessel Foundations

Civil/Structural Engineering Guideline Rev. 1

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REVISION and APPROVALS

Rev. Date Description By Approved

0 Original Version

1 JUN 09 General Revision KG,IM,SJ,JI, D.Mueller

This document is the sole and exclusive property of Mustang, including all patented and patentable features and/or confidential information contained herein. Its use is conditioned upon the user's agreement not to: (i) reproduce the document, in whole or in part, nor the material described thereon; (ii) use the document for any purpose other than as specifically permitted in writing by Mustang; or (iii) disclose or otherwise disseminate or allow any such disclosure or dissemination of this document or its contents to others except as specifically permitted in writing by Mustang. "Mustang" as used herein refers to Mustang Engineering Holdings, Inc. and its affiliates.

EG-1903

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MUSTANG Vertical Vessel Foundations

Rev. 1


TABLE OF CONTENTS

1.0 SCOPE AND OVERVIEW.......................................................................................................... 4 2.0 DEFINITIONS............................................................................................................................. 4

2.1 Clarification of Terms ...................................................................................................... 4 2.2 Abbreviations and Acronyms .......................................................................................... 4

3.0 ROLES AND RESPONSIBILITIES ............................................................................................ 4 3.1 Lead Technical Professional ........................................................................................... 4 3.2 Design Technical Professional ........................................................................................ 4 3.3 Vessel Technical Professional ........................................................................................ 4

4.0 CODES, STANDARDS AND REFERENCE DOCUMENTS ....................................................... 4 5.0 DESIGN DATA........................................................................................................................... 5

5.1 From the Design Criteria ................................................................................................. 5 5.2 From Vessel Drawings.................................................................................................... 5 5.3 From Plot Plan and Equipment Layout Drawings ............................................................ 5 5.4 From Project Team ......................................................................................................... 5 5.5 From Construction Department ....................................................................................... 5

6.0 DESIGN CONDITIONS .............................................................................................................. 6 6.1 Vertical Loads ................................................................................................................. 6 6.2 Wind Loads..................................................................................................................... 6 6.3 Seismic Loads ................................................................................................................ 9 6.4 Piping Loads................................................................................................................. 11

7.0 LOAD COMBINATIONS .......................................................................................................... 11 7.1 ASD Load Combinations............................................................................................... 11 7.2 LRFD Load Combinations............................................................................................. 11

8.0 ANCHOR BOLTS..................................................................................................................... 12 8.1 General......................................................................................................................... 12 8.2 Steel Strength of Anchor Bolts in Tension..................................................................... 13 8.3 Steel Strength of Anchor Bolts in Shear ........................................................................ 13 8.4 Anchorage in Concrete ................................................................................................. 14 8.5 Interaction of Tensile and Shear Forces........................................................................ 16 8.6 Seismic Requirements .................................................................................................. 17

9.0 PEDESTAL DESIGN................................................................................................................ 17 9.1 General......................................................................................................................... 17 9.2 Sizing............................................................................................................................ 17

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9.3 Reinforcing.................................................................................................................... 18 10.0 FOOTING DESIGN .................................................................................................................. 19

10.1 Sizing............................................................................................................................ 19 10.2 Stability Ratio................................................................................................................ 19 10.3 Soil Bearing .................................................................................................................. 20 10.4 Loads on piles............................................................................................................... 21 10.5 Reinforcing and Stresses .............................................................................................. 22

11.0 AVAILABLE SOFTWARE........................................................................................................ 23 APPENDICES...................................................................................................................................... 24

Appendix 1: Foundation Charts ............................................................................................... 24 Appendix 2: Design Example.................................................................................................... 38

LIST OF FIGURES

Figure 1 Typical anchor bolt layout when forces are transferred to additional reinforcement ................ 16 Figure 2 Typical reinforcement layout to tie pedestal to the footing. ..................................................... 19 Figure 3 Soil pressure Octagonal footings.......................................................................................... 24 Figure 4 Soil pressure Square diagonal ............................................................................................ 25 Figure 5 Soil pressure Square flats ................................................................................................... 26 Figure 6 Biaxial soil bearing pressure Rectangular footings .............................................................. 27 Figure 7 Biaxial soil bearing pressure Rectangular footings (CONT)................................................. 28 Figure 8 Footing thickness required with no top steel, fc=3000 psi...................................................... 29 Figure 9 Footing thickness required with no top steel, fc=4000 psi...................................................... 30 Figure 10 Elements of octagons (even side dimensions) ..................................................................... 31 Figure 11 Elements of octagons (even side dimensions) ..................................................................... 32 Figure 12 Elements of octagons (even side dimensions) ..................................................................... 33 Figure 13 Elements of octagons (even side dimensions) ..................................................................... 34 Figure 14 Vertical vessel anchor and base ring details......................................................................... 35 Figure 15 Vertical vessel anchor and base ring details......................................................................... 36 Figure 16 Vertical vessel anchor and base ring details......................................................................... 37

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1.0 SCOPE AND OVERVIEW This guideline is for use in the analysis and design of foundations for vertical vessels. It shall be used in conjunction with engineering guidelines EG-1010, C/S Process Plant Design Philosophy and EG-1900, Civil Structural Engineering. When there is a discrepancy between this document and Project Design Criteria or job specifications, the latter shall govern.

2.0 DEFINITIONS 2.1 Clarification of Terms

This section is not applicable to this document

2.2 Abbreviations and Acronyms ACI American Concrete Institute

ASCE American Society of Civil Engineers

IBC International Building Code

3.0 ROLES AND RESPONSIBILITIES 3.1 Lead Technical Professional

Lead Technical Professional is responsible for the interpretation of all the project documents (geotechnical report, client design criteria, codes and design guideline). The Lead is also responsible for the definition of the type of foundation, elevations, and general criteria. The Lead assigns work to Design Technical Professional to meet the project schedule.

3.2 Design Technical Professional The Design Technical Professional is accountable for the quality of deliverables in accordance with applicable standards, specifications, project design criteria and equipment drawings. Deliverables including calculations and sketches shall be completed as directed by the Lead Technical Professional.

3.3 Vessel Technical Professional The Vessel Technical Professional is responsible to provide the vessel drawings, complete with base reactions; general dimensions; and anchor bolt diameter, type and layout.

4.0 CODES, STANDARDS AND REFERENCE DOCUMENTS

American Concrete Institute (ACI). Building Code Requirements for Structural Concrete and Commentary, ACI 318-08. 2008.

American Society of Civil Engineers (ASCE), Minimum Design Loads for Buildings and Other Structures, ASCE 7-05. 2005.

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5.0 DESIGN DATA The Design Technical Professional shall review and obtain the following information prior to analyzing and designing the footings:

5.1 From the Design Criteria Concrete and reinforcing strength Allowable soil bearing pressure, friction factor and coefficient of passive pressure Allowable pile capacities Ground water table elevation for buoyancy Bottom of foundation elevation Frost depth Wind and seismic design parameters

5.2 From Vessel Drawings Basic vessel dimensions Empty and operating weights Ladder and platform locations Wind and seismic shear and moment at base of vessel (for comparison) Number, size, location and tensile strength (grade) of anchor bolts Bolt circle diameter Base plate or anchor chair detail

5.3 From Plot Plan and Equipment Layout Drawings Orientation of vessel Location of vessel (centerline coordinates) Top of grout elevation

5.4 From Project Team Existing or new foundations around the vessel Existing or new underground piping Existing or new electrical and instrument underground duct banks Existing or new above ground drainage including trenches, ditches, catch basins and

manholes Other interferences such as extent of adjacent new structures and ribs for weather

barrier, not otherwise shown on the vessel drawing

5.5 From Construction Department Additional loading on foundation due to erection method, such as gin poles

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6.0 DESIGN CONDITIONS 6.1 Vertical Loads

6.1.1 Erected Weight The erected weight is the fabricated weight of the vessel plus all of the removable internals, ladders, platforms and pipe supports and all the items that are intended to be erected with the vessel.

6.1.2 Empty Weight The empty weight is the weight of the vessel plus all of the removable internals, ladders, platforms, insulation and fireproofing. The weight does not include any liquid contents, catalyst contents, or platform live loads.

6.1.3 Operating Weight The operating weight is the weight of the vessel plus all of the removable internals, ladders, platforms, insulation, fireproofing, design liquid level, catalyst contents and attached piping weight and pipe supports. Normally 3% of the fabricated weight is added by Mustangs Vessel Group to account for the attached piping. An additional 10-20% allowance may be included for attached piping where the weight is provided by vendor and not by the Vessel Group. When preliminary vessel information is being used, an additional 5-15% contingency, based on engineering judgment, may also be added to account for changes in the vessel weight. The operating weight does not include live or snow load.

6.1.4 Field Test Weight The field test weight is the operating weight of the vessel including the water required for hydrostatic test in lieu of the design liquid level and catalyst contents.

6.1.5 Foundation Weight The foundation weight is the weight of the foundation and weight of the soil above the foundation

6.1.6 Others Any eccentric loads, such as reboiler or other equipment supported on the

side of the vessel, shall also be evaluated. All of the above loads shall be considered as dead load for application of

concrete design load factors. Live loads or snow loads will typically not control any part of foundation

design and may be ignored.

6.2 Wind Loads 6.2.1 General

The results from this section shall be compared to the Vessel Group calculations to insure consistency within the company. Vertical vessels with a total height to diameter (H/D) ratio equal to or greater than 10 may vibrate due to vortex shedding effect. In this case, forces should be obtained from the Vessel Group.

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Contact the Vessel Group to verify banding thickness around insulation. This is normally ignored in calculations, but it should be checked when clearances are required.

6.2.2 Gust Effect Factor This factor can be calculated based on the following table. The vessel shall be classified first as flexible or rigid depending on the period of vibration Table 6-1 Classification of vertical vessel

Criteria Period 1.0 sec Period < 1.0 sec

Classification Flexible Rigid

Gf

Calculate per ASCE 7, Section 6.5.8.2 (use a critical damping ratio = 0.01) or obtain from

Vessel Group

0.85

For uniform vertical vessels, the natural period of vibration may be calculated using the ASCE Guidelines for Seismic Evaluation and Design of Petrochemical Facilities in accordance with the following formula:

tDW

DHT t

1210

78.7 26

= Equation 6-1

Where, T Period, s Wt Operating or Empty Weight, lb/ft H Total Height, ft D Outside diameter of vessel, ft t Skirt thickness, in

For more precise calculations and for non-uniform vertical vessels, STAAD Pro may be used for generation of natural period and seismic force. If available, the period may be obtained from the Vessel Group.

6.2.3 Simplified Procedure Calculate wind loads in accordance with ASCE 7 (or project design criteria), as follows

fzz Gqp = Equation 6-2

Where, p Design wind pressure, psf qz Velocity pressure, equal to IVKKKq dztzz

200256.0= V Basic wind speed, from design criteria, mph Kd Wind directional factor, generally 0.95 I Importance factor, generally 1.15 unless Client Specifications or Lead

Technical Professional dictate a different value.

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Kz Velocity pressure exposure coefficient. Based on the Exposure Category, Kz shall be determined from table or equations on ASCE 7, table 6-3.

Kzt Topographic factor, from Design Criteria. Gf Gust effect factor (See Section 6.2.2)

Compute wind loads using an effective vessel diameter (De) which approximates the effect of all projections such as piping, ladders and platforms.

pLpfe CCDDCD +++= 8.00 Equation 6-3

Where, De Effective vessel diameter, ft Cf Force coefficient (shape factor) see ASCE 7, Figure 6-21.

(use Cf = 0.8) Do Outside diameter of vessel insulation, ft. Dp Diameter of largest vertical pipe with insulation, ft. CL Ladder projected area (1.5-ft. w/cage, 1.0-w/o cage) Cp Additional width for platform areas, ft. (see Table 6-2) B Platform width, ft. S Average vertical platform spacing, ft.

Table 6-2 Factor Cp

Cp (ft) B = 3' B = 4

S = 30 0.55 0.8 S = 15 1.10 1.6

Wind shear forces and moments may be calculated using this effective diameter. If these calculations compare favorably with the Vessel Groups computer results, the shears and moments can then be used for the foundation design.

6.2.4 Detailed Procedure When more accurate loads are required or the previous method is deemed to be unacceptable, wind loads may be calculated using vessel orientation, platform drawings, and the following criteria: Wind pressure on projected area of insulated vessel times a cylindrical shape

factor. Flat surface wind pressure on platform plan area times 0.5-factor applied at

each platform. (This will account for all framing and hand railing.) To approximate the effect of shielding, the degree of platform used in determining platform plan area shall not exceed 180 for any platform except the platform at the top of the vessel.

Wind pressure on ladder with cage (assume tributary width of 1.5-feet) with a 1.0-shape factor.

Wind pressure on largest vertical pipe (including insulation) with a shape factor of 0.8.

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When vessel orientation drawings are not available, the following criteria shall be used for estimating platforms: A minimum of one 3-0 wide platform, 2'-6" below each man-way, 15-feet or

greater above grade shall be considered. One square platform at the top of the vessel when job requirements dictate

(size depends on vessel diameter). A minimum of one platform every 30-feet shall be taken into consideration. Platforms are sized based on the following table:

Table 6-3 Typical size of platforms for vertical vessels

Vessel Diameter (D) Degree of Platform

D 48" 48" < D 96 96" < D 144" 144" < D

180 135 90 60

6.2.5 Forces at the Base of the Vessel Shear and moment due to wind may be calculated as follows

= zzw ApV Equation 6-4

= zzw hVM Equation 6-5 Where, Vw Wind shear force at the base of the vessel, lb Mw Wind overturning moment at the base of the vessel, lb-ft pz Design wind pressure at elevation z, psf Az Projected area of vessel at elevation z, ft2

ezz DhA = hz Distance from the bottom of vessel to elevation z, ft hz Length of stack section under consideration, ft Vz Horizontal force at elevation z, lb De Effective diameter at elevation z, ft (See Section 6.2.3)

6.3 Seismic Loads The results from this section shall be compared to the Vessel Group calculations to insure consistency within the company. Calculate seismic base shear using the equivalent lateral force procedure of ASCE 7, Section 12.8, as follows:

tss WCV = Equation 6-6

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IRSC DSs = Equation 6-7

Cs need not exceed:

=

IRT

SC Ds 1

for LTT < Equation 6-8

=

IRT

TSC LDs2

1

for LTT

Equation 6-9

Cs shall not be less than 0.01 In addition, where S1 is greater than or equal to 0.6, Cs shall not be less than

01.05.0 1

=

IRSCs

Equation 6-10

Where, Wt Weight of vessel (empty and operating condition should be checked) Cs Seismic response coefficient SDS Design spectral response acceleration parameter in the short period range R Response modification factor (Design Criteria or ASCE 7, Table 15.4-2; generally taken

as 3.0) I Importance factor (Design Criteria or ASCE 7, Table 11.5-1) SD1 Design spectral response acceleration parameter at a period of 1.0 second S1 Mapped maximum considered earthquake spectral response acceleration parameter at

a period of 1.0 second T Fundamental period of the structure (See Section 6.2.2) TL Long-period transition period (See ASCE 7 Figure 22-15 to 22-20)

The overturning moment for vessels with uniformly distributed weight may be taken as

= HVM ss 3

2

Equation 6-11

Where, Ms Seismic overturning moment at the base of the vessel, lb-ft Vs Seismic shear force at the base of the vessel, lb H Total height of vessel, ft

The computed seismic force using the above procedure is based on the strength level (LRFD). The shear and moment results presented on the vessels drawing are normally based on working stress level (ASD). When working with the strength level, the Vessel

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Groups seismic shear and moment shall be multiplied by a factor of 1.4 in order to convert from allowable stress level to strength level. The results shall be compared to the Vessel Group calculations to insure consistency within the company.

6.4 Piping Loads Forces due to thermal expansion of piping shall be included in load combinations when judged significant. For concrete design, piping thermal loads shall be considered as dead load. Thermal loads will not normally be added to wind loads. Overturning need not be checked for thermal loading.

7.0 LOAD COMBINATIONS 7.1 ASD Load Combinations

The following allowable stress design (ASD) load combinations shall apply for soil bearing and pile capacities, unless job specifications dictate otherwise. Factors shown are per ASCE 7, modified per industry practice, and are given as an example. Specific job criteria may result in different load combinations. Table 7-1: ASD Combination loads

Description Load Combination

Operating weight 1.0DO

Operating weight + wind or seismic (operating)

1.0DO+1.0W or (0.7EO +0.14SDSDo) 0.9DO + 0.7EO

Empty weight + wind or seismic (empty) 1.0DE + 1.0W 0.9DE + 0.7EE

Test or erection weight + partial wind

1.0DTEST + 0.33W 1.0DEREC + 0.33W

Note that the 0.6 dead load factor does not apply for vertical vessel foundation uplift combinations since the dead loads for non-building structures are known to a higher degree of accuracy than dead loads for buildings.

7.2 LRFD Load Combinations The following strength design (LRFD) load combinations shall apply for reinforced concrete design unless job specifications dictate otherwise. Factors shown are per ASCE 7, modified per industry practice, and are given as an example. Specific job criteria may result in different load combinations.

Table 7-2: LRFD Load combinations

Description Load Combination

Operating weight 1.4DO

Operating weight + wind or seismic (operating)

1.2DO + 1.6W or(1.0EO + 0.2SDSDO) 0.9DO + 1.0EO 0.2SDSDO

Empty weight + wind or seismic (empty) 0.9DE + 1.6W

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0.9DE + 1.0EE 0.2SDSDE

Test weight 1.4DTEST

Test or erection weight + partial wind

1.2DTEST + 0.53W 0.9DERECT + 0.53W

Where, DE Vessel empty weight and foundation weight DEREC Vessel erection weight DO Vessel operating weight DTEST Vessel test weight W Wind Load EO Horizontal Earthquake Load during normal operation EE Horizontal Earthquake Load during an empty condition. SDS Design Earthquake Spectral Response Acceleration for short periods.

If spectral short period acceleration, SDS, is less than 0.125, the vertical component of seismic effects (+/- 0.2 SDS) can be taken as zero. When applicable, all of the above combinations shall also be evaluated for a buoyant condition (high groundwater table).

8.0 ANCHOR BOLTS 8.1 General

Anchor bolt diameters selected by the Vessel Group shall be checked by the Structural Technical Professional for tensile and shear strength on the steel and concrete. It is desirable to select an appropriate anchorage system to keep bolts out of the mat. The Vessel Group often figures anchor bolt tension using the Brownell-Young method (ASD), which commonly produces smaller tension forces. This method may be utilized to avoid discrepancies. The Mustang MathCAD template Brownell_Young1.mcd available on myMustang can be used to quickly calculate the anchor bolt tension of a skirted vertical vessel. The calculated factored anchor bolt tension shall be converted to ASD prior to comparing with the Brownell-Young. For non-galvanized anchor bolts, a corrosion allowance of 3/16-in shall be subtracted from the bolt diameter. The corroded diameter shall be used for calculating stress in the bolt material. Bolt pullout and shear on concrete will not be affected by corrosion. Neither an anchor bolt template nor anchor bolt sleeves are required for vertical vessels unless specifically requested by Client. Normal Mustang procedure is to utilize galvanized A36 anchor bolts. All pre-tensioned anchor bolts shall be high strength and all high strength anchor bolts shall be pre-tensioned. Use Anchor Bolt Type PA (Mustang A.B. Schedule) for all pretensioned bolts. For high strength anchor bolts, initial bolt tension shall be 0.375Fu times the gross area of the bolt as indicated by a required angle of nut rotation from a snug tight condition, torque, or pretension value. A Mustang MathCAD template A.B.Pre-tension V1.2.xmct, available on myMustang, can be used to quickly calculate these values.

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All pre-tensioned anchor bolts shall be installed with a bond breaker (tape) that will prevent the grout or concrete from bonding to the bolt throughout its stretched length (bottom of chair/base plate to 1-in above the nut). Tape shall be of a non-water absorbing material. Vessels over 150-ft in height or with a height to diameter ratio (H/D) greater than 10 should have high strength anchor bolts regardless of the stress in the bolts. Anchor bolts shall project 2.5 times the bolt diameter above the vessel chair or plate. Note that often a plate is provided above the chair, which shall also be cleared.

8.2 Steel Strength of Anchor Bolts in Tension Anchor bolt tension may be checked using the following procedure and limited to the LRFD capacity Tn > TAB Steel capacity

bun AFLRFDT = 56.0)(

Equation 8-1

For wind load:

NW

BCNMLRFDT EwAB

9.046.1)(

=

Equation 8-2

For seismic load:

=N

WSWBCN

MLRFDT DSsAB2.09.040.1)(

Equation 8-3

` Where, TAB Anchor bolt tension due to seismic or wind, lb Tn Steel design strength Mw Wind moment at base of vessel, lb-ft Ms Seismic moment at base of vessel (empty or operating), lb-ft N Number of anchor bolts BC Bolt circle diameter, ft. WE Empty weight of vessel, lb W Empty or operating weight of vessel, lb Ab Nominal (gross) area of the anchor bolt, in2 Fu Ultimate tensile strength of the anchor bolt, psi

8.3 Steel Strength of Anchor Bolts in Shear Shear on anchor bolts need not be designed unless applied factored shear force exceeds the design friction capacity, in which case the anchor bolts shall carry the full load. To have no shear force on the anchor bolts:

boltsanchoronshearNoVV uf

Equation 8-4

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Friction capacity, Vf

uf PV = 75.0

Equation 8-5

Factored compression force Pu, for wind load:

ow

u WBCMP +

= 9.0

67.06.1

Equation 8-6

Factored compression force Pu, for seismic load:

WSWBC

MP DSsu +

= 2.09.067.00.1

Equation 8-7

The total shear force per anchor bolt is:

NVLRFDV uAB =)(

Equation 8-8

If shear forces are transferred to the anchor bolts, all base shear shall be resisted by the anchor bolts. Assuming threads are included in the shear plane, the steel shear strength of anchor bolt is:

bun AFLRFDV = 40.065.0)(

Equation 8-9

Where, Vu Factored wind shear force at base of vessel, lb

Factored seismic (empty or operating) shear force at base of vessel, lb Fu Ultimate tensile strength of the anchor bolt, psi Vf Nominal frictional force capacity, lb Vn Nominal steel strength capacity, lb Pu Factored compression force at top of pedestal Mw Wind moment at base of vessel, lb-ft Ms Seismic moment at base of vessel (empty or operating), lb-ft Coefficient of friction. For the typical case of grout against steel, = 0.55. BC Bolt circle diameter, ft. WE Empty weight of vessel, lb W Empty or operating weight of vessel, lb VAB Bolt shear force, lb Ab Nominal (gross) area of the anchor bolt, in2 N Number of anchor bolts

8.4 Anchorage in Concrete 8.4.1 Forces Transferred to Concrete

Embedment length, edge distance and distance between anchor bolts may be defined based on the concrete strength per ACI 318 Appendix D. All following conditions shall be checked:

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Concrete breakout strength of anchor in tension and shear Pullout strength of anchor in tension Concrete side-face blowout strength of anchor in tension Edge distance, spacing, and thicknesses to preclude splitting failure

8.4.2 Forces Transferred to Additional Reinforcing If the anchor bolt tension force is transferred to the reinforcement, vertical dowels shall be fully developed for the applied tensile forces. Only dowels closer than half the embedment length can be used for this purpose. The selected bolt shall have adequate length to provide enough development length for the vertical dowels above the bottom of the bolt (see Figure 1) in accordance with ACI 318 Chapter 12. In some cases, it may be necessary to hook the dowels at the top of the pedestal to effectively transfer the anchor bolt tension load into the reinforcement. When using high strength anchor bolts, hairpins or a second ring of dowels may be required within a horizontal distance of one-half of the embedment depth of the anchor bolt to transfer tensile forces. Required dowel area:

FyNBTA ABdowel

=75.0

Equation 8-10

The required development length may be calculated as:

"12)()()( =

providedArequiredALrequiredL

dowel

doweldd

Equation 8-11

If a hook is used:

bdowel

doweldhdh dorprovidedA

requiredALrequiredL 8"6)()()( =

Equation 8-12

The reduction Adowel(req) / Adowel(prov) can not be applied in seismic design categories D, E and F. Where, TAB Anchor bolt tension due to seismic or wind (see Section 8.2), lb

NB Number of vertical dowels (rebars) within 0.5hef

Fy Rebar yield strength, psi Ld Development length in tension of dowel per ACI 318 Chapter 12 Ldh Development length in tension of dowel with a standard hook per ACI 318

Chapter 12

Adowel Required area of dowels close to the anchor bolt, in2

When forces are transferred to additional reinforcing, following conditions shall be checked per ACI 318, Appendix D. Concrete breakout strength of anchor in shear

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Pullout strength of anchor in tension Concrete side-face blowout strength of anchor in tension Edge distance, spacing, and thicknesses to preclude splitting failure

Figure 1 Typical anchor bolt layout when forces are transferred to additional reinforcement

8.5 Interaction of Tensile and Shear Forces If shear needs to be included, combined shear and tension shall be checked in accordance with ACI 318 Section D.7 or Project Design Criteria.

If nu VV 2.0

then full strength in tension shall be permitted: un TN

Equation 8-13

If nu NT 2.0

then full strength in shear shall be permitted: un VV

Equation 8-14

If nu VV 2.0> and nu NT 2.0> , then:

2.1

+

n

u

n

u

VV

NT

Equation 8-15

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Where, Tu Factored tensile force applied to a single anchor or group of anchors, lb Nn Lowest design strength in tension of anchor governed by steel or concrete, (see

ACI 318, D.4.1), lb Vu Factored shear force applied to a single anchor or group of anchors, lb Vn Lowest design strength in shear of anchor governed by steel or concrete, (see ACI

318, D.4.1), lb

8.6 Seismic Requirements In Seismic Design Category C, D, E or F the following requirements shall apply (Refer to ACI 318 Appendix D for additional information): The anchor design strength associated with concrete failure modes shall be taken as

0.75Nn and 0.75Vn where is given in ACI 318 Chapter D.4.4 or D.4.5 and Nn and Vn are determined in accordance with D.5.2, D.5.3, D.5.4, D.6.2 and D.6.3

Anchors shall be designed to be governed by the steel strength of a ductile steel element (in tension and shear). Ductile performance during a seismic event may be accomplished if either of the following criteria is met.

- The capacity of concrete is greater than the capacity of the steel, if Section 8.4.1 of this document is used.

- Actual tension forces from the anchor bolts are transferred to the vertical reinforcement (dowels) properly anchored in the foundation and seismic splices and development lengths are used per ACI-318 Chapter 22, if Section 8.4.2 of this document is used

- Utilize only 40% of the design strength capacity using 0.75Nn and 0.75Vn where is given in ACI 318 Chapter D.4.4 or D.4.5.

9.0 PEDESTAL DESIGN 9.1 General

Orient drain towards the nearest catch basin Check between pedestal and vessel ladder interference

9.2 Sizing Concrete pedestals supporting vertical vessels shall be sized using the minimum dimension required to provide concrete coverage for anchor bolts as follows: Bolt circle + 8 inches Bolt circle + 8 bolt diameters (GR 36 bolts) Bolt circle + 12 bolt diameters (High strength bolts) Bolt circle + sleeve diameter + 7 bolt diameters (GR 36 bolts) Bolt circle + sleeve diameter + 11 bolt diameters (High strength GR 105 bolts) Clearance to fit anchor bolts within vertical pedestal reinforcing O.D. base + 2 times grout thickness Pedestals 6'-0" and over shall be octagonal in shape; under 6-0 may use a square shape. To facilitate standard forms, octagons may be sized in even 2-in increments for the flat dimension and squares in even 2-in increments out-to-out.

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9.3 Reinforcing The pedestal shall be tied to the footing with sufficient dowels around the pedestal perimeter to prevent separation of the pedestal and footing. If pedestal height is greater than 8-0, then consider splicing the dowels. Dowels may be conservatively sized by computing the maximum tension at the pedestal perimeter due to overturning moment at the pedestal base using a modified anchor bolt formula. For wind load:

Ewind

dowel WRCMLRFDT = 9.046.1)(

Equation 9-1

For seismic load:

WSWRC

MLRFDT DSseismicdowel 2.09.040.1)( +=

Equation 9-2

Required dowel area:

FyNBT

A doweldowel =

9.0

Equation 9-3

The required development length may be calculated per Section 8.4.2 above The reduction Adowel(req) / Adowel(prov) can not be applied in seismic design categories C, D, E and F. Where, Mw Wind moment at base of vessel, lb-ft Ms Seismic moment at base of vessel (empty or operating), lb-ft Tdowel Dowel tension due to seismic or wind, lb NB Number of vertical dowels (rebars) RC Reinforcing circle diameter, ft (assume pedestal dimension minus 6-in) WE Empty weight of vessel plus pedestal, lb W Empty or operating weight of vessel plus pedestal, lb Fy Rebar yield strength, psi Adowel Required area of dowel, in2 heff Embedment length, in Ld Development length in tension of dowel per ACI 318 Chapter 12 Ldh Development length in tension of dowel with a standard hook per ACI 318 Chapter 12

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Figure 2 Typical reinforcement layout to tie pedestal to the footing.

Recommended minimum pedestal reinforcement should be as follows:

Squares up to 6-0 #4 vertical rebars with #3 Ties each at 12-in maximum spacing

Octagons 6-0 3/8 to 8-5 3/8: 24 - #5 vertical rebars with #4 ties at 12-in maximum spacing

Octagons 8'-10 1/4" to 11'-8": 32 - #6 vertical rebars with #4 ties at 12-in maximum spacing

Octagons larger than 11'-8": #6 vertical rebars with #4 ties each at 12-in maximum spacing

Pedestals for vertical vessel foundations need not be designed as columns. Splice lengths for ties shall be class "B". The reduction factors from ACI Section 12.2 are not normally applied. The minimum splice length shall be 16-in. A double set of ties shall be placed at top of pedestal to protect anchor bolts. Provide minimum temperature top reinforcing steel #4 @ 12 C/C in orthogonal directions for pedestals over 8-0.

10.0 FOOTING DESIGN 10.1 Sizing

Square footings are preferable to octagonal footings. Flat dimension on octagons and overall dimension on squares shall be sized in even 2-inch increments to facilitate the use of metal forms. Rectangular or combined footings may be required in confined areas, but should be avoided where possible. Adjusting the plot plan coordinates in conjunction with piping layout may be an acceptable solution in confined areas. The minimum footing thickness for soil supported foundations shall be 15-in and the minimum thickness for pile supported foundations shall be 18-in, with 3-in incremental increases. The thickness selected shall be checked for shear and tension in the concrete.

10.2 Stability Ratio Stability provisions outlined herein apply to shallow foundations. Footings supported on piles should utilize the tension capacity of piles. The minimum Stability Ratio for service

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loads other than earthquake shall be 1.5 or in accordance with job specifications. For earthquake service loads, the minimum Stability Ratio shall be 1.2 or in accordance with Job Specifications. For a foundation with symmetrical and concentric pedestal and footing, the overturning stability ratio may be calculated as:

ebSR

=2

Equation 10-1

Where, b Dimension of the footing in the direction of overturning moment, ft

e Eccentricity equal to the overturning moment at the base of the footing divided by the total vertical load, ft

The stability ratio for sliding is defined as the passive soil resistance plus the frictional resistance to sliding divided by the maximum horizontal force applied to the foundation, for any given loading condition. For estimating purposes, the following values may be used if they are not provided in the Design Criteria or Geotechnical Report. For cohesive soils: Cohesion: 500-psf (may be taken as zero) Adhesion: 250-psf For cohesionless soils: Passive Pressure Coefficient, Kp: 3.0 (may be taken as zero) Soil to Concrete Friction: 0.5

10.3 Soil Bearing Soil bearing values shall be calculated using allowable stress combinations specified in Section 7.1, The maximum soil bearing pressure shall be checked on the diagonal axis. Soil bearing pressure used for reinforcing design shall be computed on the normal axis (on the flat). When applicable, all load combinations shall be evaluated for a buoyant condition when a high groundwater table is encountered. The minimum factor of safety for buoyancy shall be 1.2 under unfactored service loads. Any increase in allowable soil bearing pressure for wind, seismic, or thermal load combinations shall be based on Project Design Criteria and recommendation by the Geotechnical Consultant. The soil bearing pressure may be computed using Figure 3, when the entire octagonal footing area is not in compression (e/D > 0.122 on the diagonal and e/D > 0.132 on the flat). When the entire square footing area is not in compression (e/D > 0.118 on the diagonal and e/D > 0.167 on the flat), the soil bearing pressure may be computed using Figure 4 or Mustangs MathCAD template (Fdnstd Version 2.1.xmcd). When the entire footing area is in compression, the soil bearing pressure shall be computed using the combined stress formula: S.B. = P/A M/S.

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Table 10-1: Bearing pressure equations

Octagon Square

for e/D 0.132 :

( )DeAPBS 57.71. =

for e/D 0.167:

( )DeAPBS 61. =

FLA

T

for e/C 0.319:

( )CeAPBS 134.31. =

for e/D 0.122 :

( )DeAPBS 19.81. =

for e/D 0.118:

( )DeAPBS 49.81. =

DIA

GO

NA

L

for e/D 0.295 :

( )CeAPBS 39.31. =

Where, P Total vertical load, lb e Eccentricity (M/P), ft. D Overall size, ft C Octagon flat side length, ft SB Soil bearing pressure, psf M Overturning moment at base of footing, lb-ft A Footing area, ft2

10.4 Loads on piles The maximum pile load shall be calculated using the following formula.

= 22 xxM

yyM

nPQ yx

Equation 10-2

Where, P Total vertical load, lb n Total number of piles Mx, My Overturning moment at the base of pile cap about x-axis and y-axis

respectively, lb-ft x Distance measured from the centroid of the pile group about the y-axis to

any pile, ft. y Distance measured from the centroid of the pile group about the x-axis to

any pile, ft.

2x , 2y Total amount of inertia of the pile group about y-axis and x-axis respectively.

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10.5 Reinforcing and Stresses 10.5.1 General

Footing reinforcing shall be checked for both minimum shrinkage and temperature requirements and for minimum flexural reinforcing requirements of ACI 318 chapter 15. The minimum bottom (and top, if required) footing reinforcing shall be #5 at 12-in. Top reinforcing shall be provided for combined foundations. When supporting two or more vertical vessels on a common mat in a seismic zone, the footing shall be checked for a possible loading case where the vessels are vibrating out of phase.

10.5.2 Moment and Shear in Footing Shear and bending moments shall be computed based on the actual soil bearing pressure as specified in Section 10.3 of this guideline, then factored by the appropriate design load factors. For square pedestals, the critical section for moment and rebar development shall be at the face of the pedestal and for octagonal pedestals, the critical section for moment and rebar development shall be at the face of a square of equivalent area. Moment and rebar development shall be checked at the face of the equivalent square. Beam shear shall be checked at a distance d from the face of the pedestal (use an equivalent square for octagonal shapes) in accordance with ACI 318, section 11 and 15. Two-way (punching) shear shall be checked at a distance d/2 from the face of the pedestal (use an equivalent square for octagonal shape) as applicable per ACI 318, Section 11.11. For shear and moment calculations, a unit width strip designed as a simple cantilever from the equivalent square shall be used. The resulting reinforcing steel shall be placed continuously across the entire footing width in a grid pattern with orthogonal rebars for loads along the other axis.

10.5.3 Top reinforcement Top reinforcement in the footing is not necessary if the factored flexural moment of the footing does not exceed the nominal flexural strength of the structural plain concrete as follows:

un MM Equation 10-3

6'5'52tbfSfM cmcn ==

Equation 10-4

MM u *4.1= Equation 10-5

c

u

fMt

'56

min required for no top reinforcement

Equation 10-6

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Where, Mn Nominal flexural strength, lb-in Mu Factored moment, lb-in (caused by weight of soil and concrete acting

on a 1-foot strip in the footing at the face of the equivalent squared pedestal. Use a load factor of 1.4).

fc Compressive strength of concrete, psi Strength reduction factor for structural plain concrete = 0.60

Modification factor for lightweight concrete, =1.0 for normal weight concrete

t Design thickness, in b Width of section = 12-in

The design thickness (t) shall be taken as 2-in less than actual thickness for concrete cast against soil (no reduction is required for concrete cast against a seal slab). See Figure 8 and Figure 9. Footings shall either be thickened or reinforcing placed at the top of the footing if required. Footings greater than 24-in thick and pile caps shall have top reinforcing. Where seismic effects create tensile stresses, provide top reinforcement.

11.0 AVAILABLE SOFTWARE MathCAD templates, Foundation 3D, Mat 3D and other software may be used for analysis and design of vertical vessel foundations.

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APPENDICES Appendix 1: Foundation Charts

Figure 3 Soil pressure Octagonal footings

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Figure 4 Soil pressure Square diagonal

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Figure 5 Soil pressure Square flats

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Figure 6 Biaxial soil bearing pressure Rectangular footings

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Figure 7 Biaxial soil bearing pressure Rectangular footings (CONT)

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The curves below are for determining the thickness of the footing with no top steel. Based on weight of concrete and soil acting on a one-foot strip. The thickness selected shall be reduced by 2-in for concrete placed against seal slab.

MM u *4.1=

( )6

"2'52= tbfM cn

60.0= 1= (normal weight)

soilonassumedf

Mtc

u "2'5

6 +=

1

2

3

4

5

6

7

8

9

10

11

12

3 4 5 6 7 8 9 10 11 12Depth of bottom of footing , H

(in)

Leng

th o

f Can

tilev

er, L

(ft

)

Notes: f'c=3000 psisoil=100 lb/ft3

concrete=150 lb/ft3

t=33"

t=30"

t=27"

t=24"

t=21"

t=18"

t=15"

t=12"

t=36"

t=40"

Figure 8 Footing thickness required with no top steel, fc=3000 psi

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1

2

3

4

5

6

7

8

9

10

11

12

3 4 5 6 7 8 9 10 11 12Depth of bottom of footing , H

(in)

Leng

th o

f Can

tilev

er, L

(ft

)

Notes: f'c=4000 psisoil=100 lb/ft3

concrete=150 lb/ft3

t=33"

t=30"

t=27"

t=24"

t=21"

t=18"

t=15"

t=12"

t=36"

t=40"

Figure 9 Footing thickness required with no top steel, fc=4000 psi

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Figure 10 Elements of octagons (even side dimensions)

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Figure 14 Vertical vessel anchor and base ring details

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Appendix 2: Design Example This example is used to illustrate the use of the Design Guideline EG-1903. Programs such as Foundation-3D is normally utilized for foundationdesign of vertical vessel.Mustang assumes no responsibility for the accuracy of this spreadsheet. It is the sole responsibility of the "User" as to the accuracy of all informationincluded within and derived from use of this spreadsheet_________________________________________________________________________________________________

VERTICAL VESSEL ENGINEERING GUIDELINE - EXAMPLE

1.0 DESIGN CRITERIA AND CONSIDERATIONS

1.1 From Design Criteria

- Concrete compressive strength fc 4000psi:=

- Yield strength of steel fy 60000psi:=

- Net allowable soil bearing pressure qa 3600psf:=- Soil weight 110pcf:=

- Internal friction angle 30deg:=

- Passive pressure coefficient Kp 3.0:=

- Coefficient of horizontal friction tan ( ):= 0.58=

- Min. footing depth below grade due to frost Frost_depth 3ft:=

- Ground water table elevation El 90ft:= (10 feet below grade)

- Wind speed V 90mph:= (based on ASCE 7-05)

- Grout thickness Grout 1.5in:=

- Seismic parameters SDS 0.35:= SD1 0.133:=

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Figure 1. Vessel Foundation -general dimensions plan view - Diameter of pedestal Dped 16.09375ft:=

- Height of pedestal Hped 3ft:=

- Footing thickness tftg 1.5ft:=

- Overal height of foundation OL Hped tftg+ 4.5ft=:=

- Bearing depth Df OL 1ft 3.5ft=:=

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1.2 From Vessel Drawings

- Empty weight, De 170kip:=

- Operating weight, Do 350kip:=

- Test weight, Dt 625kip:=

- Design forces for wind or seismic (these forces shall be verified)

- Anchor bolts, 24-1 1/2" ASTM F1554 GR 36Bolt circle = 14'-10 1/2"No sleeve

- Outside diameter of base ring, ODbase 184in:= (assumed, detailed vessel drawingnot available)

- Bolt diameter, db 1.5in:=

- Number of anchor bolts, N 24:=

- Bolt circle BC 14.88ft:=

- Internal diameter, D 14ft:=

- Skirt thickness, t9in16

:=

- Height of vessel, Hv 70ft:= 2.0 WIND LOAD VERIFICATION

The vessel must be classified as rigid or flexible in order to calculate the correct gust factor. Also, thevessel can be checked for dynamic effects (vortex shedding and ovaling) based on ASME-STS-1-05. (Thisis normally done by Vessel Group rather than Civil Group)

2.1 Period Calculation

- For uniform vessels, use the following analytical equation:

Operating mass,

Tuniform7.78 s ft0.5

106 kip0.5

HvD

2

1000 Do

HvD

t:=

Tuniform 0.24s=

- Using a mathematical model in STAAD:

Six nodesMass/node of 58.3 kipsEigen solution

TSTAAD 0.27sec:=

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2.2 Wind responses - Vortex Shedding

A rule of thumb to address this problem is provided in the design guideline to classify a verticalvessel as sensitive to this dymanic effect. If H/D > 10, the vessel needs to be analyzed for vortexshedding effects in accordance with the procedure on ASME-STS-1.Using this rule of thumb for this example, H/D=70/14=5 and therefore vortex shedding may need notbe analyzed. This is normally addressed by Vessel Group in an accurate approach.

2.3 Wind Load Calculation (ASCE 7-05)

- Vessel period T = 0.27 seconds < 1.0 seconds, therefore the vessel is rigid. - For rigid vessels, the gust factor can be 0.85 and ASCE 7-05 procedure can be used. - See attached MathCAD template for calculations.

Wind overturning moment, Mwind 624kip ft:=

Wind base shear, Vwind 16.7kip:= 3.0 SEISMIC LOAD VERIFICATION

See attached MathCAD template for calculations.

Seismic overturning moment, Mseismic 1779kip ft:=

Seismic base shear, Vseismic 38.1kip:= 4.0 ANCHOR BOLTS DESIGN

4.1 Basic information

Diameter of anchor bolt db 1.5 in=

Nominal area of anchor bolt, Ab db2

4:=

Nominal tensile stress of anchor bolt Fnt 43.5ksi:= ASTM F1554 gr36

Nominal tensile strength of dowel Fu_d 90ksi:= ASTM A615 table 2, Grade 60

Nominal tensile stress of dowel Fnt_d 0.75 Fu_d:=

Anchor bolt type H12A (per Standard Mustang Anchor Bolt Schedule)

Note: This chapter is based on the nomenclature of AISC Design Guide #1.

Anchor chair type 2 Hchair 10in:= see ED-1102 Vertical Vessel Ring

Minimum projection required hproj.min Hchair 2.5 db+ 13.75 in=:=

Anchor bolt design is an iterative process. In this example, a standard anchor bolt is selected andchecked.

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Figure 2. Anchor bolt general dimensions 4.2 Maximum Tension on Anchor Bolts

- For wind load (LRFD):

TAB_wind4 1.6 Mwind

N BC

0.9 De

N:=

TAB_wind 4.81kip=

- For seismic load (LRFD):

TAB_seismic4 1.0 Mseismic

N BC

0.9 Do 0.2 SDS Do

N:=

TAB_seismic 7.82kip=

NOTE: Tension forces should be calculated for empty condition too (not shown in thisexample).

- Maximum ultimate tension force on anchor bolt

TAB max TAB_seismic TAB_wind, ( ) 7.82kip=:=

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4.3 Maximum Shear on Anchor Bolts

This needs to be checked for wind and seismic condition. In this example, shear is checked forseismic only

For seismic load:

Vu 1.0 Vseismic:=

Vu 38.1kip=

Calculate friction shear resistance between vessel base plate and grout to see if it is greater than Vu.

v 0.75:=

v 0.55:= (between steel and grout)

PuMseismic0.67 BC

0.9 Do+ 0.2 SDS Do:=

Pu 469kip=

Note: 0.67*BC is an approximation of the arm in compression. A detailed calculation can be done.

V f v Pu:=

V f 203kip= > Vu 38kip= OK

Therefore, bolts do not need to be designed for shear 4.4 Steel strength of anchor bolts in tension:

Using AISC-LRFD 13th edition, Chapter J:

N T 0.75 Ab Fnt:=

N T 57.65kip= > max TAB_seismic TAB_wind, ( ) 7.82 kip= OK

Note: A b is the nominal area of anchor bolt (not "tensile area"). See table below from AISC Design Guide #1. This result for thetensile strength should be very similar to ACI-318 App.D, using A se with the net tensile area and the tensile strenght F uta (butminimum 1.9Fy or 125 ksi). See commentary on ACI 318, section D.5.1.2 for further information

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4.5 Steel Strength of Anchor in Shear:

This check is not required in this example because shear is resisted entirely by friction 4.6 Anchorage in Concrete

On pedestals, it is usually better to transfer the forces to the vertical dowels (development length) - see ACI318 D.5.2.9 - instead of providing enough edge distance and using the effective depth as per ACI 318D.5.2.3. See EG-1903 Design Guideline for additional information.

- Basic information

Diameter of nut Cnut 2.75in:=

Dowel diameter ddowel68

in:=

Ahex 33

2

Cnut2

2

:= Ahex 4.91 in2

=

Abolt db

2

4:= Abolt 1.77 in

2=

Abrg Ahex Abolt:= Abrg 3.14 in2

=

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- Required Area of vertical rebars (dowels)

All tension force will be transfer to the vertical dowels,

Reinforcing circle diameter RC Dped 6in:= Assume pedestal dimension minus 6"

RC 15.59ft=

Number of dowels closer thanhef/2 from anchor bolt

ND 1:= For initial design, a conservativeassumption is used

Rebar yield strength Fy 60ksi:=

Anchor bolt force TAB 7.82 kip=

Required dowel area AdowelTAB

ND 0.75 Fy:=

Adowel 0.17 in2

= Use min #6 at 12" verticaldowels

Provided dowel area Adowel_prov

4ddowel

2 0.44 in2=:=

Use 56 #6 Bars, 7 @ each face - Required development length of dowel and effective depth (above the anchor bolt)

This is the splice length required to transfer the force from the anchor bolt tothe vertical dowels

1:= Reinforcement location factor

1:= Coating factor

1:= Lightweight aggregate factor

0.8:= Reinforcement size factor

Ldt340

fy

2.5

ddowel

fc psi:= Development length of dowel, [in],

(REF 12-1 of ACI 318)

Ldt 17.08 in=

Ld_required max Ldt 12in, ( ) 17.08 in=:= (Required)

Ld 23.6in:= (Provided) OK

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As(req)/As(prov) factor is not normally applied if the design is govern by seismic and ductility is required.

A minimum effective depth of the anchor bolt is checked. Normally 12 times the diameter of the bolt isrequired.

hef_min 12 db 18 in=:= (this is minimum) (Required)

hef 29in:= (Provided) OK

See following table for direct values for development length (for 2" cover)

- Required development length of standard hook in tension (below the anchor bolt)

Ldhb 0.02 fyddowel

1.0 fc psi 14.23 in=:=

Ldh_required max Ldhb 6in, ( ) 14.23 in=:= (Required)

Ldh 21.375in:= (provided) OK

As(req)/As(prov) factor is not normally applied if the design is governed by seismic and ductility isrequired.

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- Concrete side face blowout strength

Assuming the length of the pedestal to be greater than hef

Height of pedestal, Hped 3ft=

Edge distance, ca1 1.03Dped

2

BC2

:=

ca1 10.18 in= > camin 4 db:=

N sb 0.75 160 ca1 Abrg 1.0 fc psi( ):=

N sb 137kip= > max TAB_seismic TAB_wind, ( ) 7.82 kip= OK - Minimun spacing and edge distance for anchor bolts

Based on ACI-318 Appendix D.8:

Diameter of bolt, db 1.5 in=

Spacing: smin 4 db:= (6*BoltDia for torqued)

smin 6 in= OK

Edge distance: edgemin 4 db:=

edgemin 6 in= OK 4.7 Dimensions checkings

It is preferred to have the anchor bolts above the footing for constructability purposes

Minimum projection is equal to height of chair plus 2.5 times the diameter of the bolt

Length of the anchorbolt

Lab 45in:=

Actual projection hproj 14in:=

Embedment of anchor bolt hem Lab hproj:=

hem 31 in=

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Minimum clearance from bottom of bolt to top of footing, Clear 1in:=

Minimum height of pedestal required, Hpedmin hem Clear+:=

Hpedmin 2.67 ft=

Height of pedestalprovided

Hped 3ft= OK

Minimum Overall height required, OL_frost Frost_depth 1ft+ 4ft=:=

Overal heightprovided

OL 4.5ft= OK

Pedestal height and dowels layoutare enough to keep the anchorbolts above the footing level.

Figure 4. Dimensions checkings

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5.0 PEDESTAL DESIGN

5.1 Pedestal Sizing

Based on the design guideline, the pedestal shall be the maximum of:

BC 8in+ 186.56in=

BC 8 db+ 190.56in= (controls)

ODbase 2 Grout+ 187 in=

190.5" ~ 15'-10 1/2" (using standard drawing EG-4304-1 thru EG-4304-4)

Use Dped = 16'-1 1/8"

Cped 6.667ft:= 5.2 Reinforcing

Minimum vertical reinforcement for pedestals with height to diameter ratio less than 3 do not to have tocomply with column requirements per ACI 318.

The pedestal shall be tied to the footing with sufficient dowels around the pedestal perimeter to preventseparation, following EG-1903,

- Required rebar area

Rebar yield strength Fy 60 ksi=

Reinforcing circle diameter RC 15.59ft=

Total number of rebars NB 56:=

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Pedestal weight Dp 0.828 Dped2

Hped 150lbf

ft3:=

Dp 96.51kip=

Tension on the dowel

Ttiedowel_wind1.6 4 Mwind

RC0.9 De 0.9Dp:=

Ttiedowel_seismic1 4 Mseismic

RC0.9 Do Dp+( ) 0.2 SDS Do Dp+( ) :=

Note: This is a conservative method to calculate the tension on the dowels, TheBrownell-Young method may be used if required

Ttiedowel max Ttiedowel_wind Ttiedowel_seismic, ( ) 85.74 kip=:=

Required dowel area AtiedowelTtiedowelNB 0.9 Fy

:=

Atiedowel 0.03 in2

= Use min #6 at 12 in. maximumspacing

Provided dowel area Atiedowel_prov ddowel

2

40.44 in2=:= OK

- Required development length of standard hook in tension (to tie the pedestal to the footing)

Ldh_tiedowel 0.7 0.02 1ddowel fy

1.0 fc psi 9.96 in=:=

Ldhtiedowel_req max Ldh_tiedowel 6in, ( ) 9.96 in=:= (Required)

Ldh_tiedowel_prov tftg 6in:=

Ldh_tiedowel_prov 12 in= (Provided) OK

Ldh is multiplied by 0.7 if the side cover is more than 2.5 in and the cover beyond the 90-degree hook ismore than 2 in.

As(req)/As(prov) factor is not normally applied if the design is governed by seismic and ductility isrequired.

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6.0 FOOTING DESIGN

6.1 Stability Ratio

Size of footing is often governed by the stability ratio:

Mseismic 1779 kip ft= (or wind)

Assuming 20'-0" square, 1'-6" thick footing,

B 20ft:= tftg 1.5ft=

Wfooting B B tftg 150lbf

ft3:= Wfooting 90 kip=

Asoil B B 0.828 Dped2

:=

Wsoil Asoil Df tftg( ) 110lbf

ft3:= Wsoil 40.82kip=

Wped 0.828 Dped2

Hped 150 pcf:= Wped 96.51 kip=

Ptotal Do Wfooting+ Wped+ Wsoil+:=

ecc0.7Mseismic0.9 Ptotal( )

:= ecc 2.4ft=

SRB

2ecc4.17=:= > 1.2 OK

The stability ratio for sliding (SRs), SRS = V n/Vseismic

Vn Ptotal:=

Vn 333.32kip=

SRsVn

0.7Vseismic:=

SRs 12.498= > 1.5 OK

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6.2 Soil bearing

Soil bearing needs to be checked for all load combinations. For this example, onlyone case will be checked:

Operating + Seismic (0.9Do + 0.7Eo)

The eccentricity is:

ecc 2.4ft= (B-D ped )/4.

tftg1B Dped( )

40.98ft=:= < t ftg OK

Where,B is the footing width on the flat or diagonalDped is the pedestal width,

- Beam shear check (D~diagonal)

Diagonal Length Dia B2 B2+ 28.28ft=:=

ForeccDia

0.08= < 0.118

qdiag 2911.73psf= < qa_gross 3985 psf= OK

Because the previous assumption (linear distribution of pressure at the bottom) is conservative, use afactor of 1.5 to convert the pressure from working stress to LRFD, or calculate the pressure using factoredforces (Pu = 1.2*P, M u = 1.6Mwind, for example). Using a factor of 1.5 for this example, we have....

qf 1.5 qflat:= qf 3.72kip

ft2=

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- Pressure "q" at a distance "d" from the face of an equivalent square:

mAB2

ecc+:= mA 12.4ft=

L 0.828 Dped2

:= L 14.64ft=

d tftg 3in 1.25ft=:=

qd qfmA 0.5 B L( ) d+

mA:=

qd 3.29kip

ft2=

- Shear at a distance "d":

Vd qdB L( )

2d

qf qd( )B L( ) d[ ]

2+:=

Vd 5.58kipft

=

V c 0.85 2 fc psi d:=

V c 19.35kipft

= OK

- Flexure analysis

For the same combination and forces, pressure at the face of the equivalent square:

qface qfmA 0.5 B L( )

mA:=

qface 2.92kip

ft2=

Mu 0.5 B L( ) qface 0.5 0.5 B L( )[ ] 0.5 B L( ) 0.5 qf qface( )23

0.5 B L( )+:=

Mu 12.38 kipftft

=

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- Minimum reinforcement per ACI 318

Minimum reinforcement shall the greater of 0.0018*b*h or, the minumum of 0.0033*b*d and 1.33As(req) butnot less than required by design, A s(req)

a. As_min 0.001812 intftg2

0.19 in2=:= Mu 12.38kip=

b.req

fc2fy

1.7 2.897.556Mu

12inft

d2 fc

:=

As_req req 12inft

d:= 1.33As_req 0.25in2

ft=

c. 0.003312 inft

d 0.591ft

in2=

Use the minimum between 'b' and 'c' and then the maximum betwwen MIN(b,c). and 'a'.but not less than #5@12"

Therefore, provide As(min) = 0.257 in2/ft #5 @ 12" each way (0.31 sq. in per foot) at the bottom

- Requirement of reinforcing at the top

Reinforced is required at the top due to seismic provisions for this example. The use of Figure 8 and 9 onEG 1903 is shown here for information only

Using Figure 9 in the EG-1903, for the following variables, we have

Depth of foundation Depth_H Df 3.5ft=:=

tftg.design tftg 2in 16 in=:= (assuming directly onsoil, 2-in substracted)Thickness of foundation

Lengh of cantilever LcantDia Dped( )

26.1ft=:=

Maximum lenght of cantileverwith no top reinf.

Lmax.notop 5.5ft:= (From Figure 9)

Therefore, top reinforcement is required (match bottom reinforcement)

EG-1903 Vertical Vessel Foundation_Rev1!06!29-09

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