A senior design presentation in Structural Engineering

1. Structural Design of Office Building with Design
Variations for Natural Hazardous Environments
Nkonyeasua G. Adaikpoh
Tennessee State University,
Department of Architectural
Engineering
April 15, 2009

2. Introduction
Mr. Moneybags International
has decided to expand his
company’s offices to 3 new
markets. In a bid to move
quickly he hires a Structural
Engineer to perform a feasibility
design per his requirements and
thereafter report the results
and cost.
Structural Analysis and Design - Nkonyeasua G. Adaikpoh

3. Design Evolution
Architectural Components
Governing Texts:
1. International Building Code (IBC 2006)
2. Architectural Graphics Standards
3. The Architect’s Studio Companion
Structural Analysis and Design - Nkonyeasua G. Adaikpoh

4. Locations Characteristics
All in the downtown areas of the cities.
Stiff soils – well compacted
Disaster prone – added lateral forces
San Francisco New Orleans Oklahoma City
In San Andreas Caused damage Gently rolling
fault zone. of $1 Billion+ in hills & shrubs
Pleasant 2005 Temperate, sub-
weather Hurricanes humid climate
Earthquakes Tornadoes
Structural Analysis and Design - Nkonyeasua G. Adaikpoh

5. Disaster Definitions
Earthquakes Hurricanes Tornadoes
Ground shaking Severe cyclones Violent storms
caused by originating over characterized by
tectonic equatorial whirling funnels
processes. regions, of wind moving
Measured on the accompanied by at great speeds.
Richter torrential rain, Measured on an
magnitude scale, lightning, & enhanced Fujita
in magnitudes. winds with scale, in
speeds >74mph categories.
Measured on a
Saffir-Simpson
scale, in
categories.
USGS NOAA NOAA

6. Effects on Buildings
Earthquakes Hurricanes Tornadoes
Photo courtesy USGS and NGDC Stan Honda/AFP/Getty Images © How Stuff Works

7. Requirements Translation

8. Preliminary Design
Occupancy classification – B - Business
3-Hour Noncombustible construction
Type I-A
Sprinklered building
Unlimited height and area
Site cast concrete system
Two-way post-tensioned flat plate
slab with 30’ x 30’ bays
300’ maximum travel distance
Open plan

9. Planning
Maximum travel
distance – 300ft

10. Shear Wall Stiffness Distribution – Code compliant
b h Area, Ai xi dx (xi- dy (yi- Ix =bh3/12 + Iy =bh3/12 + % %
Tower Shape (in) (in) (in2) (in) Aixi (in3) yi (in) Aiyi (in3) xbar) ybar) Adx2 (in4) Ix TOWER Ady2(in4) Iy TOWER stiffness x stiffness y
Tower 2 - Tower 1 -
Top right Top left
252130 32760 480 15724800 1381 45241560 -421.05 360.40 5854056115 4301279897
stair
-
228106 -24168 480 -11600640 1381 33376008 -421.05 360.40-4262040695 1592015420 -3116512746 1184767152 42.22% 22.82%
132
252130 32760 0 43243200 1381 45241560 418.94 360.40 5796018744 4301279897
stair
132 -
228106 -24168 0 -31901760 1381 33376008 418.94 360.40-4219224847 1576793897 -3116512746 1184767152 41.82% 22.82%
Tower 4 - Bottom Tower 3 - Bottom
left elevator
110232 25520 805 20543600 640 16332800 -96.054 -380.59349925238.7 3811194440
- -
86208 -17888 805 -14399840 640 11448320 -96.054 -380.59 100550905.1 249374333.6 -2526694458 1284499982 6.61% 24.74%
right stair
128256 32768 988 32374784 640 20971520 86.945 -380.59426667210.7 4925603018
- -
104232 -24128 988 -23838464 640 15441920 86.945 -380.59 74173893.91 352493316.8 -3386866861 1538736157 9.35% 29.63%
SUM = 33456 30145680 34145184 3770676967 5192770442 100.00% 100.00%
Center of stiffness for the building
xbar = 901.1in = 75.1ft
ybar = 1020.6in = 85.0ft
Ix = 3770676967in4
Iy = 5192770442in4

11. Shear Wall Stiffness Distribution – Code compliant
Column stiffness check
Largest column size = 36 x 36 in
Area, Ai Aiyi Ix =bh3/12
Shape b (in) h (in) (in2) xi (in) Aixi (in3) yi (in) (in3) (in4) 6IX (in4) Iy =bh3/12 (in4) 6Iy (in4)
Column
36 36 1296 18 23328 18 23328 139968 839808 139968 839808
Check: IWALL ≥ 6ICOLUMNS
Smallest IX WALL = 249374333.6 > 839808in4
Smallest IY WALL = 1184767152 > 839808in4
ACI 318 Code discussion on slenderness
and stiffness

12. Architectural Programming
Shape from McCormac & Nelson
Open plan - 30ft x 30ft grid
Dimensions - 150ft x 120ft
Floor Area - 17,100sf
Building Area - 17,100sf x 20 floors
Occupant load- 100sf/occupant
Egress requirement- 0.2”/occupant
Min. egress width/floor = 0.2” x 171 occupants
= 34.2”
Exit stairway - 30” clear

13. Architectural Plans
South elevation
Typical Floor Plan

14. Architectural Plans
Section and partial 3-D
view

15. Design Evolution Summary
Mixed use structure with
parking for all occupants
in same building.
Single use structure, 20
Mid-rise building floors, regular floor plan
in 3 locations
in 3 locations.

16. Design Evolution
Structural Components
Governing Texts:
1. International Building Code (IBC 2006)
2. ASCE/SEI 7-05 Minimum Design Loads for
Buildings and Other Structures
3. ACI 318-05 Building Code Requirements for
Structural Concrete
4. Building Codes Illustrated
5. Building Structures Illustrated
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

17. Structural Effects/Requirements
Produce lateral forces
which the building
must resist via a LFRS
– Lateral Force
Resisting system.
Aims:
Durability
Ductility
Reliability

18. Structural Requirements
LFRS – Shear Walls
Diaphragm – 2-way flat slabs
Aims:
Durability
Ductility
Reliability

19. Loading
Dead Load:
8” slab - 100psf
Partition - 10psf
MEP - 8psf
Ceiling - 2psf
Misc. - 5psf
Total - 125psf

20. Loading
Live Load:
80 psf – considering
light storage, and
partition locations

21. Loading: Wind Loads
V = 150mph, New Orleans
MWFRS is ex = 2.75 In
designed to resist ey = 300.625 In
Case 1
high hurricane and PE-W PN-S ForceN-S
tornado force Heights (ft)
15
PWx
7.0
PLx
-37.3
(psf)
44.4
ForceE-W (kips)
39.9
PWy
7.0
PLy
-37.3
(psf)
44.4
(kips)
49.9
winds. 30
45
11.4
14.2
-37.3
-37.3
48.7
51.5
43.8
46.4
11.4
14.2
-37.3
-37.3
48.7
51.5
54.8
58.0
60 16.3 -37.3 53.7 48.3 16.3 -37.3 53.7 60.4
75 19.0 -37.3 56.4 50.7 19.0 -37.3 56.4 63.4
90 20.0 -37.3 57.4 51.6 20.0 -37.3 57.4 64.5
105 21.0 -37.3 58.4 52.5 21.0 -37.3 58.4 65.6
120 21.0 -37.3 58.4 52.5 21.0 -37.3 58.4 65.6
135 23.5 -37.3 60.9 54.8 23.5 -37.3 60.9 68.5
150 25.0 -37.3 62.3 56.1 25.0 -37.3 62.3 70.1
165 26.0 -37.3 63.3 57.0 26.0 -37.3 63.3 71.3
180 27.0 -37.3 64.3 57.9 27.0 -37.3 64.3 72.4
195 27.8 -37.3 65.1 58.6 27.8 -37.3 65.1 73.2
210 28.5 -37.3 65.9 59.3 28.5 -37.3 65.9 74.1
225 29.3 -37.3 66.7 60.0 29.3 -37.3 66.7 75.0
240 30.1 -37.3 67.5 60.7 30.1 -37.3 67.5 75.9
255 30.9 -37.3 68.2 61.4 30.9 -37.3 68.2 76.8
270 31.6 -37.3 68.9 62.0 31.6 -37.3 68.9 77.6
285 32.3 -37.3 69.6 62.7 32.3 -37.3 69.6 78.3
300 33.0 -37.3 70.3 63.3 33.0 -37.3 70.3 79.1
305 33.2 -37.3 70.5 63.5 33.2 -37.3 70.5 79.4

22. Loading: Wind Loads
Designed to withstand
Code-required wind loads
Includes torsional moments
due to eccentricity of the
shear walls and quartering
winds.

23. Loading: Wind Loads
Wind loading
animation – 100%
amplification

24. Loading: Seismic Loads
Seismic Loads Development
Chapter 11, 12, and 14 in
ASCE/SEI 7-05 code

25. Loading: Seismic Load Development
Steps to Seismic Design
1. Determine the mapped 6. Determine Seismic Importance Factor, I
maximum considered 7. Determine seismic base shear, V
earthquake (MCE) spectral 8. Distribute V over the height of the
response SS and S1. building
2. Determine if the structure is 9. Determine redundancy coefficient, ρ
exempt from seismic 10. Determine seismic load effects, E and EM
requirements
11. Check drift control requirements
3. Determine seismic design
Base shear distribution over the height of the building - San Francisco
requirements (SDC) Story MTx MTy
Height Height Weight Force F (kip- (kip-
4. Determine Analysis Level (ft) (ft) (kips) W i Hi k Cvx (kips) ft) ft)
1 15 15 3240 571320 0.003 8 48 60
procedures 2 15 30 3240 2147072 0.012 30 180 225
3 15 45 3240 4657801 0.025 65 391 489
5. Determine R, Response 4
5
15
15
60
75
3240
3240
8068892
12356971
0.044
0.067
113
173
678
1038
847
1298
Modification Coefficient 6
7
15
15
90
105
3240
3240
17504439
23497225
0.095
0.128
245
329
1471
1974
1838
2468
8 15 120 3240 30323630 0.165 425 2548 3185
9 15 135 3240 37973664 0.207 532 3190 3988
10 15 150 3240 46438621 0.253 650 3902 4877
Total 150 32400 183539635 1.000 2570

26. Loading: Seismic Loads
Designed to withstand
Code required seismic loads
OTM shown

27. Loading: Seismic Loads
Seismic loading
animation – 100%
amplification

28. Loading: Seismic Loads
Seismic loading
animation – 50%
amplification

29. Design: pca Column – Shear Wall Design

30. Design: pca Column – Column Design

31. Construction Comparison
San Francisco New Orleans Oklahoma City
Less building – More building – Same building as
10 floors 20 floors for New Orleans
Special R.C. Ordinary R.C. Wind speed is
Shear Walls Shear Walls less in Oklahoma
Column Column than for New
dimensions – 28” dimensions– 30” Orleans, but the
x 28” x 30” disasters exact
Rough concrete Rough concrete - similar forces
– 6730yd3 11000 yd3 Rough concrete -
Reinforcing – Reinforcing - 11000 yd3
375 tons 700 tons Reinforcing -
700 tons
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

32. Concluding summary
San Francisco New Orleans Oklahoma City
More building – 20 More building – 20
Less building – 10 floors floors
floors About twice as 54% more rebar
46% less much rebar
More than twice
reinforcing bars 61% more concrete the amount of SF’s
39% less concrete than SF
concrete.
Cost - $161.85/sf, Cost - $139.90/sf,
$45, 328,000 total Cost - $ 139.90/sf,
$27,677,000 total $45,328,000 total
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

33. F.A.Q.
• Isn’t the building a tall building? The Council of tall buildings states
that “A tall building is not defined by its height or number of stories.
The important criterion is whether or not the design is influenced
by some aspect of “tallness.” It is a building in which “tallness”
strongly influences planning, design and use. It is a building whose
height creates different conditions in the design, construction and
operation from those that exist in “common” buildings of a certain
region and period.
• Did you consider the soils in designing? Yes, e.g. the seismic design
category is based on a mixture of the location on the earth, the soil
type, and the surrounding environment.
• Why didn’t you consider flood loads in your design since the areas
you mentioned frequently have flooding? Flood loads are
inconsequential to commercial construction once the building is
above a certain height, and the wave crest won’t have a significant
effect on the building.
• How about the cost of land and building in these places? Well the
client would have already sourced the amounts for land in the 3
locations and the building costs differ but I used a national average.
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

34. F.A.Q. Contd.
• What are rigid diaphragms? Rigid diaphragms according to the ASCE
7-05 code are diaphragms of concrete slabs or concrete filled metal
deck with span-to-depth ratios of 3 or less in structures that have
no horizontal irregularities.
• Did you consider P-delta effects in your design considering the
height of the building? Yes, in the analysis and design software,
RISA-3D and pca-Column I specified the program to calculate P-Δ
effects.
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

35. Acknowledgements
• Russell Skrabut, PE, LEED AP
• C.W. Yong, PE, LEED AP
• Professor Michael Samuchin, PE, LEED AP
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT

36. THE END
San Francisco New Orleans Oklahoma City
QUESTIONS?
More building – 20 More building – 20
Less building – 10 floors floors
floors About twice as 54% more rebar
46% less much rebar
More than twice
reinforcing bars 61% more concrete the amount of SF’s
39% less concrete than SF
concrete.
Cost - $161.85/sf, Cost - $139.90/sf,
$45, 328,000 total Cost - $ 139.90/sf,
$27,677,000 total $45,328,000 total
Structural Analysis and Design - Nkonyeasua G. Adaikpoh, EIT