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SEISMIC DAMAGE AND EARTHQUAKE RESISTANT DESIGN IN MONGOLIA

SEISMIC DAMAGE AND EARTHQUAKE RESISTANT DESIGN IN MONGOLIA

E.Ganzorig, Dr.National Center for Construction, Construction, Urban Development and Public UtilitiesUrban Development and Public Utilities

07 March 2007, Ulaanbaatar07 March 2007, Ulaanbaatar07 March 2007, Ulaanbaatar

Asian Science and Technology Seminar in MongoliaSeismic Disaster Mitigation Seismic Disaster Mitigation

Research and Practice in MongoliaResearch and Practice in Mongolia

Scope of the CodeScope of the Code

In region • with MSK-64 intensity 7,8,9

For:• Building structures

• Not very important• For RC frame structure <16 story or 51m high• Not installed seismic isolators, dampers or control

systems• Highway & Bridge structures• Dams, Retaining Walls & Tunnels• Hydraulic Structures such us water tank, hydro

power station etc.

Basic philosophy of the CodeBasic philosophy of the Code

• To prevent loss of human life and personal injury

• To minimize damage to property • To ensure vital services in the event of

earthquakes.• Structures should withstand without

structural damage, moderate earthquakes and withstand without total collapse, severe

earthquakes

Soil type classificationSoil type classificationChanges in earthquake intensity on the basis of seismic intensity map

Seismic

category

of soil

Soil type

７ ８ ９

I

All types of rock not weathered to slightly weathered soil (permafrost and melted permafrost); low moisture content, dense large-debris magma rock soil with sand and clay filling up to 30%; stiff frost (permafrost) non-rock and weathered to strongly weathered rock soils with temperature -2°C and less, which are designed by the 1st principle (preservation of frost soil as a foundation);

６ ７ ８

II

Weathered to strongly weathered rock soil as well as permafrost soil not mentioned in the category I; large-debris soil not mentioned in the category I; moist to low moisture content, dense to low dense, medium to large size sand with gravel; fine to dusty, low moisture content sand; clay soil with the consistency index IL ≤ 0.5 and void ratio e < 0.9 for clay and loam, and e < 0.7 for sandy loam; plastic or friable permafrost non-rock soil, hard frost soil with temperature –2°C and higher to be built and maintained by 1st principle

７ ８ ９

III

Loose sand regardless of moisture content and fineness; large to middle size, dense to medium dense, saturated sand with gravel; fine to dusty, dense to medium dense, moist to saturated sand; clay soil with the consistency index IL > 0.5; clay soil with the consistency index IL ≤ 0.5 and void ratio e ≥ 0.9 for clay and loam, and e ≥ 0.7 for sandy loam; permafrost non-rock soil to be built and maintained by 2nd principle (allow melting of soil).

８ ９ >9

Table 1.

Methods of the Structural Calculation

Methods of the Structural Calculation

• Equivalent Static Force Method (mandatory for all type of structures)

• Dynamic Methods• Modal Analysis (additionally recommended)• Time History Analysis (for important or tall

structures)

Design Model for Structural Calculation andDesign Model for Structural Calculation and

oikik SKS ×= 1

X(x k)

Qi

Qj

Qk

Qn

X k

X k kikioik QAKS ××××= ηβψ

Design Seismic ForceDesign Seismic Force

When:

Design Limit StatesDesign Limit States

• Strength Limit State (for all calculation, also for stability e.g. slide or overturn)

• Serviceability Limit State (with necessity due to specific requirements)

Load Combination FactorLoad Combination Factor

Load cases Combination Factor

•Dead loads•Long-term Live loads•Short-term Live loads (on the

floors and roofs)

0.90.80.5

Table 2.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Design Response SpectrumDesign Response Spectrum

Type 3 soil

Type 1,2 soil

Ti

βi

Design Seismic Intensity changes due to importance of the buildings

Design Seismic Intensity changes due to importance of the buildings

Design seismic intensity on the basis of seismic intensity of the site

Descriptions of the buildings

7 8 9

1. Residential, public and industrial buildings and structures, with the exception of listed under 2-4 below

7 8 9

2. Key buildings and structures of nationwide significance*

8 9 9**

3. Significantly vulnerable buildings (Airport and railway station buildings, stadium with roof and etc.).

7** 8** 9***

4. Buildings which function is important for preventing possible damage and for removing the consequences after earthquake (Power plant, lifelines, firehouse, communications and etc.)

7*** 8*** 9***

Table 4.

Structural coefficient KΨStructural coefficient KΨ

Description of structure KΨ

1.Tall, slender structures and buildings with soft first story (towers, matches, chimneys etc. also whose slenderness ratio between upper and first story is ≤ 0.25)

1.5

2. Frame structure, in which response, an unfilled wall is not influenced

1.3

3. Buildings and structures, except hydro technical, which are not indicated in categories of 1-2

1

Table 5.

Allowed damage of structure K1.Allowed damage of structure K1.

¹Structure type Value

1. Structures in which allowed no residual deformation and local damage after the earthquake

1.02

2. Structures allowed a certain amount of residual deformation and local damage without human vulnerability

0.22-0.35

3. Structures allowed an excessive amount of residual deformation and local damage without human vulnerability

0.12

Table 3.

Modal combination(SRSS method)

Modal combination(SRSS method)

∑=

=n

iip NN

1

2

Where:

-modal components (forces, stresses, displacements, strains etc. of the mode)iN

Seismic zoning coefficient ASeismic zoning coefficient A

Design seismic activity factor

Seismic coefficient A

7 0.1

8 0.2

9 0.4

Table 3.

Seismic force distribution factorSeismic force distribution factor

∑

∑

=

==n

jijj

ij

n

jjik

ik

XQ

XQX

1

2

1η

Where:

Xij - the displacements of the structure oscillating at its natural vibrations

Length (width) limit, m

Height (story number) limit, m

For the following seismic intensity7 8 9 7 8 9

1 Steel frame structure 150 150 150 non-seismic region design procedure

2 RC frame structure:a. with in filled shear walls or rigid core walls

80 80 60 51(16) 39(12) 30(9)

b. reinforced concrete confinement along with anti-seismic tie beam form frame system

80 80 60 30(9) 23(7) 17(5)

c. reinforced concrete confinement along with anti-seismic tie beam does not form frame system

80 80 60 30(6) 24(5) 14(4)

3 RC cast in site shear wall structure

80 80 60 75(24) 63(20) 51(16)

4 RC large panel precast structure 80 80 60 45(14) 39(12) 30(9)

No Load bearing structure

Size and height limitation of the StructureSize and height limitation of the Structure Table 7.

Distances between lateral structural walls for the following seismic intensities

Masonry clad type (according

to 3.39)7 8 9

I 18 15 12

II 15 12 9

Limitation of distances between lateral walls in brick masonry

buildings

Limitation of distances between lateral walls in brick masonry

buildings

Seismic jointsSeismic joints

• Structure with irregular or complex shape in plan

• Structure with setbacks• Structure with size, exceeding code

specified limitation (table 7)

Relative Values of the Zone Factor in Current Codes

Relative Values of the Zone Factor in Current Codes

Name of Codes I II III

BNbD (2001), Mongolia 1.0 0.5 0.25

BSL (2000), Japan 1.0 0.9 0.8

UBC (1997), USA 1.0 0.75 0.375

NZS (1992), New Zealand 1.0 0.75 0.5

Comparison of Dynamic Amplification Factors

Comparison of Dynamic Amplification Factors

Figure 2. Comparison of Dynamic Amplification Factors Corresponding to Soil Condition

0

0.2

0.4

0.6

0.8

1

1.20

0.2

0.4

0.6

0.8 1

1.2

1.4

1.6

1.8 2

Fundamental Natural Period T sec.

β/3 or Rt

SNIP Cat.I

BSLJ Type 1.

SNIP Cat.II

SNIP Cat. III

BSLJ Type 2.

BSLJ Type 3.

Shortages of the CodeShortages of the Code• Not clear to understand and not properly

integrated. • Not harmonized with internationally recognized

codes • Site soil classification is not sufficient.

(not specified are the soil profile thickness, shear wave velocity, critical period of soil etc.)

• Changes of the seismic intensity of the site• Not specified formula for determine the

fundamental period of structure• Not existing a provision about inter-story drift

limitation • Not clear that, how the structure be behave as

“Strong column + Weak beam” system• Seismic force is significantly under estimated, if

comparing with other codes

1957 Govi-Altai earthquake. Damage of the brick masonry buildings

1957 Govi-Altai earthquake. Damage of the brick masonry buildings

Shortages of the Earthquake Resistant Design in Mongolia

Shortages of the Earthquake Resistant Design in Mongolia

• Inadequate knowledge and skill of the architects and structural engineers

• Not adequately reflect the damage experience with large destructive earthquakes (1988 Armenia, 1995 Sakhalin)

• Lack of facility to estimate appropriate structural performance for most common type of structural systems

• Input a site specific design response spectrum or ground motion

• Design of independent RC footings under column without tie• Design of foundation using big concrete separate blocks• Design of precast RC hollow slab floor system• Low quality of the concrete of RC structure• Building alteration design (underground and first floors,

additions)• Detailing of the interactions between structural and

non structural parts of the buildings etc.

Collapse of the brick masonry chimneys(in Byan-Olgii)

Collapse of the brick masonry chimneys(in Byan-Olgii)

Damage of brick wall with opening(in Bayan-Olgii)

Damage of brick wall with opening(in Bayan-Olgii)

Damage of brick wall between windows(in Bayan-Olgii)

Damage of brick wall between windows(in Bayan-Olgii)

1988 Armenia Earthquake1988 Armenia Earthquake

Narantuul building in Ulaanbaatar

Narantuul building in Ulaanbaatar

1995 Sakhalin, Neftegorsk Earthquake1995 Sakhalin, Neftegorsk Earthquake

“Earthquake effects on structures systematically bring out the

mistakes made in design and construction, even the minutest

mistakes”

M.Newmark and E.Rosenblueth assert:

M.Newmark and E.Rosenblueth assert:

Thank you for the attention !!!Thank you for the attention !!!