Introduction to Seismic Analysis and Design - AIT Consulting - Asian

41 Pages·2014·5.56 MB·English

Engr. Thaung Htut Aung
M. Eng. Asian Institute of Technology
Deputy Project Director, AIT Consulting

• Selection of Structural systems
– Load paths
– Materials
– Approximate sizing of members
– Primary mechanisms of inelastic behavior
• Review in terms of
– Dynamic response parameters
• Mode shapes, natural periods, modal participating mass ratios
– Lateral load response parameters
• Base shear, base moment, lateral displacement, story drift, shear
distribution between frame and shear walls
3

• The Gravity Load Resisting System
– The structural system (beams, slab, girders, columns, etc) that act
primarily to support the gravity or vertical loads
• The Lateral Load Resisting System
– The structural system (columns, shear walls, bracing, etc) that primarily
acts to resist the lateral loads
• The Floor Diaphragm
– The structural system that transfers lateral loads to the lateral load
resisting system and provides in-plane floor stiffness
Source: NEHRP Seismic Design Technical Brief No. 3
6
Purpose
“To transfer lateral loads applied at any location in
the structure down to the foundation level”
• Primary Lateral Loads
– Load generated by Wind Pressure
– Load generated due to Seismic Excitation
• In low seismic zones, expected ground motion will not produce
the same large inelastic response demands that would occur in
high seismic zones.
• When the seismic force is small compared to the gravity load
and wind load requirements, there is more reserve strength to
resist seismic forces.
• Permit to use systems and configurations with lower energy
dissipation capabilities in low seismic zones such as concrete
intermediate and ordinary moment-resisting frames, and
concrete braced frames.
• In high seismic zones, usually systems with high energy
dissipation capacities are allowed.
8

Parameter Value
Spectral acceleration (5% damped) at short periods (0.2 s) of horizontal ground motion
0.77 g
(2500-yr. return period), S
S
Spectral acceleration (5% damped) at long periods (1 s) of horizontal ground motion
0.31 g
(2500-yr. return period), S
1
Spectral acceleration (5% damped) at short periods (0.2 s) of horizontal ground motion
0.91 g
(2500-yr. return period) adjusted for site class effects, S
MS
Spectral acceleration (5% damped) at long periods (1 s) of horizontal ground motion
0.88 g
(2500-yr. return period) adjusted for site class effects, S
M1
Design spectral acceleration (5% damped) at short periods (0.2 s) of horizontal ground
0.60 g
motion, S
DS
Design spectral acceleration (5% damped) at short periods (1 s) of horizontal ground
0.58 g
motio, S
D1
Site class E
Short period site coefficient, F 1.176
a
Long period site coefficient, F 2.76
v
Response modification coefficient, R (Dual system, Shear wall + IMRF) 6.5
10