3

Preliminary Design

(Code based design approach)

Service Level Evaluation

(43-year return period)

Collapse Prevention Level Evaluation

(2475-year return period)

4

Level of Earthquake Seismic Performance Objective

Frequent/Service Level Earthquake(SLE): 50% probability of exceedancein 30 years (43-year return period)

Serviceability: Limited structuraldamage, should not affect the abilityof the structure to survive futureMaximum Considered Earthquakeshaking even if not repaired.

Maximum Considered Earthquake(MCE): 2% probability of exceedancein 50 years (2475-year return period)

Collapse Prevention: Building may beon the verge of partial or totalcollapse, extensive structural damage;repairs are required and may not beeconomically feasible.

6

Item Limit

Story drift 0.5%

Link beam Remain elastic

Shear wall Remain elastic

Column Remain elastic

Girder Remain elastic

• Demand to capacity of the primary structural members shall not exceed 1.5, in which the capacity is computed by nominal strength multiplied by the corresponding strength reduction factor in accordance with ACI 318.

• It is anticipated that the demand to capacity ratio of 1.5 based on design strengths can be expected to result in only minor inelastic response.

7

Item Limit

Peak transient drift Mean value ≤ 3%, Maximum value ≤ 4.5%

Residual drift Mean value ≤ 1%, Maximum value ≤ 1.5%

Column Remain elastic

Girder rotation ≤ ASCE 41 limits

Link beam rotationConventional Reinf. ≤ 0.04 radiansDiagonal Reinf. ≤ 0.05 radians

Shear wall reinforcement strain≤ 0.05 in tension≤ 0.02 in compression

Shear wall concrete strainIntermediately confined concrete ≤ 0.004 + 0.1 ρ (fy / f'c)Fully confined concrete ≤ 0.015

Force-controlled action demand shall be 1.5 times the mean if it is not limited by welldefined yield mechanism. If it is limited by well-defined yield mechanism, use the meanplus 1.3 times standard deviation but not less than 1.2 times the mean. The capacity isdetermined based on expected material properties with corresponding strengthreduction factor.

8

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7 8 9 10

Spe

ctra

l Acc

ele

rati

on

(g)

Natural Period (sec)

Response Spectra

SLE DBE MCE

Elastic Model

• Used for DBE, SLE and wind analysis

• All components were modeled as elastic.

• Response spectrum analysis was conducted for DBE and SLE earthquakes.

• Used for MCE analysis

• Inelastic member properties

• Elements that are assumed to remain elastic were modeled with elastic member properties.

• Nonlinear time history analysis was conducted for seven sets of ground motions.

Nonlinear Model

9

11

Modeling

• An analysis model must capture the important aspects of behavior of the real structure. A useful model does this with sufficient accuracy, economy and detail for practical purpose.

• A model does not have to be exact, and never will be.

Computation

• Complex process, involving finite element theory, complex logic, and extremely large numerical computations.

• The numerical computations (given the analysis model, get the analysis results) will almost be done by computer.

Interpretation

• Challenge is to use the results to make design decisions for the actual structures.

• Develop a “feel” for structural behavior.

12

Model building geometry

Material properties

Member section definitions(Linear/Nonlinear)

Member section assignment

Gravity load pattern/assignment

Mass source definition

Analysis cases

Section cuts, Generalized displacements definitions

Analyze model

ETABS/SAP2000

• Geometry of an object can be drawn graphical user interface easily.

• Pre-defined nodes are not required.

• Frame objects are meshed automatically while area objects are meshed manually.

• Generally, soil springs are modeled for both vertical and lateral restraining effect of soil.

• Draw the nodes first.

• Members are added based on pre-defined nodes.

• Geometry of an object can be drawn according to specified rules and limitations.

• Define “Element Group” at the beginning.

• Suggest to import the model geometry from ETABS/SAP2000.

• Elements cannot be meshed automatically.

• Generally, fixed support for columns and pinned support for shear walls.

• Lateral soil springs are modeled.

PERFORM 3D

13

ETABS/SAP2000

• Nonlinear stress-strain curves

• Back-bone curve can be defined with many points.

• Hysteresis– Elastic

– Kinematic

– Takeda

• Nonlinear stress-strain curves

• Two shapes available for back-bone curve.– Bilinear

– Trilinear

• Hysteresis loops can be adjusted by energy factor.

PERFORM 3D

14

ETABS/SAP2000

• Cross-sections are defined and can be assigned to the elements directly.

• Section stiffness can be modified by stiffness modifiers.

• Equivalent slab-beams for flat slabs.

• Cross-sections are defined and can not be assigned to the elements directly.

• Sectional properties are modified directly, without stiffness modifiers.

• Compound components need to be defined before assign to the elements.

• Compound component is combination of rigid zone, cross-section and hinges.

• Equivalent slab-beams for flat slabs.

PERFORM 3D

15

ETABS/SAP2000

• Auto hinge assignment is available using provided reinforcement.

• Bilinear back-bone curve is used.

• Hysteresis– Isotropic

– Kinematic

– Takeda

– Pivot

• Auto hinge assignment is not available.

• Capacity of the members needs to be calculated first.

• Two shapes available for back-bone curve.– Bilinear

– Trilinear

• Hysteresis loops can be adjusted by energy factor.

PERFORM 3D

16

ETABS/SAP2000

• Layered shell element

• More complex model, nonlinear behavior can be considered in all response

• Material behavior is monitored at a number of integration points.

• Element can be arbitrary shape with several layers and any orientation.

• A number of elements are needed across the wall width to provide enough total fibers.

• Shear behavior is usually modeled as linear.

• Inelastic shear wall element

• In-plane flexural response can be considered as nonlinear, out-of-plane response is linear.

• Single element with several fibers can be used in planner walls.

• Shear behavior is modeled as linear.

PERFORM 3D

17

ETABS/SAP2000

• Section properties and hinges can be assigned directly to selected members.

• Local axis of the elements are defined when the element is drawn.

• Rigid zones can be assigned to selected frame elements automatically.

• For beams, shear wall end or column end does not need to be considered explicitly.

• Compound components are assigned to selected members.

• Local axis of the elements are assigned explicitly.

• Rigid zone has to be defined for each frame compound component.

PERFORM 3D

18

ETABS/SAP2000

• One load pattern can be assigned as nodal loads, frame loads, and area loads.

• Self-weight of the elements are calculated automatically.

• Loads are assigned to selected elements directly.

• For frame point loads, four point loads can be assigned as maximum.

• Load patterns have to be defined separately for nodal loads and frame loads.

• Area loads cannot be assigned.

• Weight per unit length of compound component has to be defined manually.

• Sub-groups need to be defined for components with different load values.

• For frame point loads, two point loads can be assigned as maximum.

PERFORM 3D

19

ETABS/SAP2000

• Generally, area loads (SDL, LL) are assigned to slab elements for gravity loading.

• Self-weight (DL) of all elements are calculated automatically.

• Self-weight of slabs, beams and girders, live load and superimposed dead load are calculated manually and assigned to frame components.

• Self-weight of shear walls and columns are calculated automatically.

PERFORM 3D

20

ETABS/SAP2000

• Specified load patterns can be used as mass source.

• Generally, mass is not assigned to the elements explicitly.

• Load patterns cannot be used as mass source.

• Mass is assigned as nodal mass explicitly.

• Floor mass is assigned at CM of floor using rigid diaphragm constraint or distributed mass is assigned at each column node.

PERFORM 3D

21

ETABS/SAP2000

• Generalized displacements– Story drift

– Shear wall axial strain

• Section cuts– Story shear, story moment

– Shear wall shear

• Definitions can be added or modified after the analysis.

• Drift definitions– Story drift

– Distortion drift

• Strain gauge– Shear wall axial strain

• Section cuts– Story shear, story moment

– Shear wall shear

• Definitions cannot be added or modified after the analysis.

PERFORM 3D

22

ETABS/SAP2000

• Run gravity load analysis (Nonlinear static) first.

• Continue NLTHA after gravity load analysis.

• Generally, construction sequence analysis is conducted in gravity load analysis.

• Run gravity load analysis (Nonlinear static) first.

• Continue NLTHA after gravity load analysis.

• Construction sequence analysis is not available.

PERFORM 3D

23

ETABS/SAP2000

• Extracting of results takes time.

• Export directly to Excel.

• Member IDs can be checked easily in the model.

• Fast in extracting of results.

• Export to text files.

• Needs to import and format in Excel.

• Separate program is needed to locate the members with corresponding nodal coordinates and nodal connectivity.

PERFORM 3D

25

• Base shear

• Story drift (Transient drift, residual drift)

• Lateral displacement

• Section cut forces

– Story shear

– Story moment

– Shear wall shear

– Basement wall in-plane shear

• Shear wall axial strains

• Girder and link beam rotations

• Slab-beam rotation

• Girder shear

• Column forces (Axial, moment and shear)

26

27

Strain Gauge (C04)

SW 1-1

-5

5

15

25

35

45

55

-0.006 -0.001 0.004

Sto

ry

Axial Strain (mm/mm)

Wall Axial Strain (C04)

ARC

CHY

DAY

ERZ

LCN

ROS

TAB

Average

Steel YieldingStrainMax. Comp.Strain LimitStrain gauge locations in shear walls

28

Shear wall leg IDs -5

5

15

25

35

45

55

-200000 -100000 0 100000 200000St

ory

Shear Force (KN)

Shear Wall Shear Demand vs. Capacity (SW1-1)

ARC

CHY

DAY

ERZ

LCN

ROS

TAB

AVERAGE

Capacity

Maximum LimitCapacity

SW1-1

29

-10

0

10

20

30

40

50

60

-0.08 -0.06 -0.04 -0.02 0 0.02 0.04

Sto

ry

Rotation (radians)

Link Beam Rotation (LB-1)

ARC

CHY

DAY

ERZ

LCN

ROS

TAB

Average

Coupling beam IDs

• Post-tensioned slab was designed as “nonparticipating” system (not part of the lateral load resisting system) to resist the gravity loads under the expected lateral displacements.

• Checked by two methods to reduce the likelihood of punching shear failure under seismic loading. 1) Inelastic rotation of the slab outrigger beams was checked in

accordance with ASCE 41.

2) Story drift with respect to gravity load punching shear D/C ratio was checked in accordance with ACI 318-08 Sect. 21.13.6.

30

31

0

10

20

30

40

50

-0.04 -0.02 0 0.02 0.04 0.06 0.08

Sto

ry

Slab Beam Rotation (radians)

Moment Hinge Rotation due to Positive and Negative Moment(SB2-1)

ARC

CHY

DAY

ERZ

LCN

ROS

TAB

Average

Limit

Slab outrigger beam IDs

32

Response spectrum analysis in ETABS (scale

base moment of NLTHA)

Export to SAFE

Allowable soil pressure, Flexure, Shear

33

Response spectrum analysis in ETABS (scale base shear of NLTHA)

Define section cuts

Collector, Chord, Shear friction, Distributor, Shear,

Axial Reinforcement

34

Scenario for in-phase

and out-phase

Diaphragm reinforcement

• Out-of plane flexure and shear (Lateral pressure from soil)– Inertia component

– Kinematic component

• In-plane shear (force transferred from ground and basement level diaphragms)

35