Structural Efficiency Improvement by Topology Optimization and Performance Based Design

1. OBJECTIVE
To decrease the amount of
Structural Material Used in Buildings.
“Structural Efficiency improvement by
Optimization and Performance Based
Techniques for Tall Buildings”.

2. Floor = 80
Height = 414m
GFA = 220 000 m2
Floor = 163
Height = 828m
GFA = 309 473 m2
SIGNIFICANCE OF STUDY
Structural Material Quantities

3. Structural Efficiency
Both buildings have
same heights but one
uses 7 times more steel.
SIGNIFICANCE OF STUDY

4. Hochhaus Uptown München
Skyscraper in Munich, Germany
PRESCRIPTIVE DESIGN
Aspect Ratio : 4
Building Width: 120’
Number of Stories: 38
Story Height: 12.6’
Building Height: 478.8’

5. Chamfered Slab
Shear wall
24’’ Thick
Concrete
Column
Bottom= 25x25
Top= 20x20
Concrete Beam
24x36
Slab Section
7.2’’ Thick
SET UP THE MODEL

6. CHOOSING THE ASPECT RATIO
829.8 m
1000 m
Burj Khalifa was tested for
four different Aspect Ratios
and the selected scheme was
829.8 m tall.
Even the smaller schemes
were rejected because they
were uneconomical
Aspect Ratio = ---------------------
Building Height
Building Width
Two Considerations -1) Material Quantity -2) GFA

7. Calculation Of Wind Force
MAKE 3D Model Import into Hypermesh Mesh it with
Triangular Elements
Import into VWT and
Run Analysis for 100 Mph
Stress on SurfaceImport into Acu Field viewObtain Pressure Magnitude

8. Three Steps of a deign process
What is Connected to What
Position of Nodes
Structural Member Areas
IMPORTANCE

9. OPTIMIZATION THEORY
Consider This Design Domain
F = Force
L = Length of Member
P = External Force
r = Distance between external
force and Support.
Load path is directly proportional to volume

10. Minimum
Material
Maximum
Material
Moment Diagram
Truss
Pratt Truss Warren Truss Optimized Truss
IMPLEMENTATION OF THEOREM

11. WHERE TO PLACE THE LATERAL LOAD RESISTING
SYSTEM
Model 1
Gives maximum
performance

12. 3D Model in Evolve Import into
SolidThinking Inspire
Apply Supports
Apply Wind Pressure
And
Static Seismic Force
Apply symmetry
Results Obtained
Interpretation
Consideration
Interpretation
In GeoGebra
Interpretation
Result

13. OBTAINED RESULTS

14. Results Obtained from Wind Tunnel
Testing and Optimization Operation
-Aspect Ratio
-Optimized Structural System
Building Height is Changed
Structural System is Changed

15. FINAL MODEL

16. 111 South Main, Salt Lake City, Utah
INDUSTRIAL APPLICATION OF
OPTIMIZATION

17. OPTIMIZATION OF A BUILDING IN CHINA

18. Why Performance based design?
For Building Heights more than 240 feet ASCE 7 Code requires the use of hybrid structural system
We put more
weight to resist
the lateral loads
Self weight of
the system also
increases
This makes
building
Uneconomical
Not following
code requires
the use of PBD
Tall Building Initiative Design Guideline

19. ACCEPTANCE CRITERIA FOR BEAMS

20. No hysteresis indicated linear behavior
Earthquake 3Earthquake 2Earthquake 1

21. Hysteresis Observed
Non-Linear Hinge response for Maximum Considered Earthquake
Blue dot indicates that the hinge
response is between IO and LS
Beam
Shear Wall

22. HOW PBD HELPS SAVE COST?
To save economy
PBD allows certain
elements to cross
certain acceptance
Criteria for MCC.
ACI Code
Designs
for ultimate
State
If we design for
MCC according to
ACI Code it
becomes
uneconomical
If we do not design
for MCC the
design is unsafe
Cost of repairing
cracks is less than
design the building for
Ultimate Limit State
according to ACI Code

23. STRUCTURAL STEEL WEIGHT INCREASES NONLINEARLY WITH INCREASING
HEIGHT DUE TO LATERAL LOADS
Premium For Height