Presented at 6th Asia Conference on Earthquake Engineering , Cebu Philippines (23 Sep 2016)

1. CASE STUDY: PERFORMANCE-BASED SEISMIC
DESIGN OF REINFORCED CONCRETE
DUAL SYSTEM BUILDING
Naveed Anwar, Thaung Htut Aung, Pramin Norachan, Ahmad Muneeb Badar
1
23 September 2016 | Cebu, Philippines

2. 2
PERFORMANCE-BASED SEISMIC DESIGN

3. Performance-based Seismic Design
• Provides an alternative, as well a progression to more explicit evaluation of
the safety and reliability of structures for different levels of earthquakes
• Provides opportunity to clearly define the levels of hazards to be designed
against, with the corresponding performance to be achieved
• Assessing the performance capability of a building, system or component,
considering the uncertainties in the post-yielding response and behavior of
the building
• Detailed local acceptance criteria indicates element-by-element
checking, rather than application of seismic response modification factor,
R for entire system and structural overstrength factor, Ω0, in the
conventional design of new buildings

4. Explicit Performance Objective in PBD
• Whereas traditional code procedures attempt to satisfy implicitly all three
objectives by designing to prescriptive rules for a single (design) level of
seismic hazard, performance based design of high-rise buildings
investigates at least two performance objectives explicitly
• 1) Service-level Assessment
• Negligible damage in once-in-a-lifetime earthquake having a return period of 43
years (50% of probability exceedance in 30 years)
• 2) Collapse-level Assessment
• Collapse prevention under the largest earthquake with a return period of 2475
years (2% of probability exceedance in 50 years)

5. Seismic Performance Objectives
Level of Earthquake Seismic Performance Objective
Frequent/Service Level Earthquake (SLE):
50% probability of exceedance in 30
years (43-year return period)
Serviceability: Limited structural
damage, should not affect the ability of
the structure to survive future Maximum
Considered Earthquake shaking even if
not repaired.
Maximum Considered Earthquake
(MCE): 2% probability of exceedance in
50 years (2475-year return period)
Collapse Prevention: Building may be on
the verge of partial or total collapse,
extensive structural damage; repairs are
required and may not be economically
feasible.

6. Overall Design Procedure
6
PreliminaryDesign
(Code based designapproach)
Service Level Evaluation
(43-year return period)
CollapsePreventionLevel
Evaluation
(2475-year return period)

7. 7
CASE STUDY BUILDING

8. Building Configuration
• 56-story residential building
• 186-meter tall
• 7-level podium with 3
basements for amenity
area and car park
• Dual system (Reinforced
concrete special moment
resisting fame with special
reinforced concrete shear
walls)
• Mat foundation and
isolated footings
8

9. 9
MODELING AND ANALYSIS
PROCEDURES

10. Modeling and Analysis Procedures
Elastic models (ETABS)
• Analyze
• Wind (Linear static analysis)
• SLE (Response spectrum analysis)
• DBE (Response spectrum analysis)
• Includes shear walls, columns,
coupling beams, girders, beams,
slabs, and foundation
• Shell elements were used to model
the floor slabs, considering the
diaphragm flexibility
Nonlinear model (Perform 3D)
• Nonlinear response verification for
MCE (Nonlinear time history
analysis)
• Includes inelastic member
properties for elements that were
anticipated to be loaded beyond
their elastic limits (flexural response
of shear walls, coupling beams,
girders, and slab-outrigger beams)
• Elements that were assumed to
remain elastic were modeled with
elastic member properties.
10

11. Response Spectrum Curves
11
0
0.5
1
1.5
2
2.5
0 1 2 3 4 5 6 7 8 9 10
Spectral Acceleration (g)
Natural Period (sec)
Response Spectra
SLE MCE

12. 12
ACCEPTANCE CRITERIA

13. Service Level Earthquake
Item Limit
Story drift 0.5%
Coupling beam Remain elastic
Shear wall Remain elastic
Girder Remain elastic
Column 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.

14. Acceptance Criteria (MCE)
Item Limit
Peak transient drift
Mean value shall not exceed3%.
Maximum drift shall not exceed 4.5%.
Residual drift
Mean value shall not exceed1%.
Maximum drift shall not exceed 1.5%.
Column Remain elastic
Coupling beam rotation ≤ 0.05 radians
Girder rotation ≤ASCE 41limits
Shear wall reinforcement strain
≤ 0.05 in tension
≤ 0.02 in compression
Shear wall concrete strain
Intermediately confined concrete ≤ 0.004 + 0.1 ρ (fy / f'c)
Fully confinedconcrete ≤ 0.015
Force-controlled action demand shall be 1.5 times the mean if it is not limited by well defined yield
mechanism. If it is limited by well-defined yield mechanism, use the mean plus 1.3 times standard
deviation but not less than 1.2 times the mean. The capacity is determined based on expected
material properties with corresponding strength reduction factor.

15. 15
OVERALL RESPONSE

16. Modal Analysis
16
Mode Period (sec)
Modal Participating Mass Ratio
X (%) Y (%)
1 8.81 0.1 54.3
2 8.08 53.1 0.1
3 6.96 1.3 0
Mode 1
Mode 2
Mode 3

17. Base Shear
17
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
X Y
Base Shear (%)
Along Direction
Base Shear in terms of Percentage of Weight of Building
at Ground Level
SLE (Elastic) DBE (Elastic) MCE (Elastic) MCE (Inelastic)
Weight of the building = 2,255,500 kN

18. Transient Drift
18
-10
0
10
20
30
40
50
60
-0.04 -0.02 0.00 0.02 0.04
Story
Transient drift
Transient drift (X-direction)
Drift-A
Drift-B
Drift-C
-10
0
10
20
30
40
50
60
-0.04 -0.02 0.00 0.02 0.04
Story
Transient drift
Transient drift (Y-direction)
Drift-A
Drift-B
Drift-C
Avg Limit

19. Residual Drift
19
-10
0
10
20
30
40
50
60
0.000 0.005 0.010 0.015
Story
Residual drift
Residual drift (X-direction)
Drift-A
Drift-B
Drift-C
Avg Limit
-10
0
10
20
30
40
50
60
0.000 0.005 0.010 0.015
Story
Residual drift
Residual drift (Y-direction)
Drift-A
Drift-B
Drift-C
Avg Limit

20. 20
Evaluation of Components at
MCE Level

21. Shear Wall
21

22. Columns and Girders
• Columns
• Axial
• Axial-flexural interaction capacity
• Shear capacity
• Girders
• Flexural rotation
• Immediate Occupancy – 70% of total girders
• Life Safety – 30% of total girders
• Shear capacity
• Probable shear demand based on moment capacity of the girders
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23. Diaphragms
• Designed to transfer in-plane forces, comprising of inertial
forces and transfer forces to vertical members of seismic
forces-resisting system.
• Diaphragm design forces were checked from ETABS model
• Response spectrum analysis was conducted in ETABS, using
MCE level response spectrum
• Scale factors for response spectrum analysis was determined,
based on demand forces from nonlinear time history analysis
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24. Diaphragms
• Designed according to stress fields determined by finite
element analysis
• Reinforcement
• Chord
• Collector
• Distributor
• Shear reinforcement
24

25. Diaphragms
25
4-DB28 4-DB254-DB25
4-DB28 4-DB28
Diaphragm chord reinforcement In-plane forces

26. 26
Conclusion

27. Conclusion
• Global and component responses of reinforced concrete
dual system building were checked against the
acceptance criteria for multiple seismic events explicitly
rather than application of modification factors under
single code specified seismic demand level.
• Floor diaphragms were designed to resist the in-plane
forces developed due to irregular T-shaped floor plan of
the building.
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28. 28
Thank You!