4. Concrete STRUCTURES
are CHEAPER AND HEAVIER than others
but SELECTING AN ECONOMICAL
Lateral-Force-Resisting System
is difficult!
5. & not with
STRUCTURAL SYSTEMS
GOOD ENGINEERING = SAFE/SOUND
+ Design
6. To develop Models
Of an
Advantages:
Reduces Design Time & Iterations
Direct Cost Savings
7. Importance Factors (P ORTLAND CEMENT ASSOCIATION)
Importance
Cost Effectiveness 4.53
Construction Time 4.13
Material Availability 3.95
Design Flexibility 3.89
Material Delivery Time 3.83
Fire Resistance 3.78
Seismic Loads 3.66
Wind Loads 3.65
Contractor Availability 3.46
Design Tie 3.36
Appearance 3.31
Ease of Design 3.17
Return on Design Fees 2.87
Available Design Software 2.53
Publications 2.48
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Mean Rating (1 = not important at all, 5 = very important)
11. HAZARD MAP OF PAKISTAN
GSHAP Hazard map (1999) Revised Hazard map (2006)
KARACHI IS ASSIGNED ZONE 2B
12. LOAD PATH
Horizontal
Diaphragm (Floor and Roof slabs ) Elements
Vertical
Shear Walls / Frames Elements
Foundation
Soil
13. LATERAL-FORCE-RESISTING SYSTEMS
Moment Resisting
Frames
Frame System
Resistance to Building Frame
Shear Wall
Lateral Loads System
Frames
(25% Lateral
Load)
Dual System
Shear Wall
19. Typical Beam Size Shear Wall Thickness
18” (Story 1 to 8)
24” 15” (Story 9 to 14)
12” (Story 15 to Roof)
10”
Concrete Compressive Strength (f„c )
Story
Beam/Slab Column/Shear Wall
Story 1 to 6 5 ksi 7 ksi
Story 7 to 11 4.5 ksi 6 ksi
Story 12 to 16 4 ksi 5 ksi
Story 17 to Roof 3 ksi 4 ksi
20. RAFT FOUNDATION (f’c = 5 ksi)
Dual System Building Frame
without Beams System with Beams
Thickness Area offset Thickness Area offset
72” 18” 72” 24”
22. ETABS modelling of
Dual System without Beams
1st Model
Shear Walls and Columns take lateral loads
USED TO DESIGN SHEAR WALL
2nd Model
Shear Walls are replaced by Columns
& 25% Earthquake Load is induced
COLUMNS ARE DESIGNED USING BOTH MODELS
23. ETABS modelling of
Building Frame System with Beams
1st Model
We use compatibility combos
USED TO DESIGN COLUMNS
2nd Model
Frames are assigned moment of inertia = 0.01
Shear walls resist all the lateral load
USED TO DESIGN SHEAR WALLS
24. LIVE LOADS (UBC 97)
Retail 50psf
Parking 50psf
Lobby 40psf
Indoor Games 40psf
Residential 40psf
Roof 20psf
25. Seismic Factors (from UBC 97)
Ct (Concrete Structure) 0.03
Overstrength Factor “R” (Dual system) 6.5
Overstrength Factor “R” (Building Frame system) 5.5
Soil Profile Type (Very Dense Soil and Soft Rock) Sc
Seismic Zone Factor “Z” (2B) 0.20
Importance Factor “I” 1
Omega Factor (System Overstrength Factor) “ΩO” 2.8
Seismic Coefficient “Ca” 0.24
Seismic Coefficient “Cv” 0.32
Dead load Multiplier (0.5 x Ca x I) 0.12
27. Cost Percentage of Dual System without Beams
Shear wall
14.1%
Column
15.6%
Slabs
55.4%
Foundation
10.5%
Beams
4.4%
28. Cost Percentage of Building Frame System with Beams
Slabs
Shear wall 12.7%
25.9%
Beams
24.5%
Column
11.8%
Foundation
25.1%
29. Cost Comparison of Different Elements
70
60
Cost (Rupees in millions)
50
40
30
20
10
0
Slabs & Beams Foundation Columns Shear walls
Dual System without beams Building Frame System with beams
30. Cost Comparison of Systems
120
100
Cost (Rupees in millions)
80
60
109
40 80
20
0
Dual System without Beams Building Frame System with Beams
31.
32. Cost Comparison of all six Systems
140
120
Moment Resisting System
with Beams
Cost (Rupees in millions)
100 Building Frame System
with Beams
80 Dual System with Beams
Moment Resisting System
60 without Beams
Dual System without
40 Beams
Building Frame System
without Beams
20
0
33. Comparison in Ratio of all six Systems
1.79
1.69
Moment Resisting System
with Beams
1.37 Building Frame System
1.32
1.24 with Beams
Dual System with Beams
1
Ratios
Moment Resisting System
without Beams
Dual System without
Beams
Building Frame System
without Beams