CE 496 B

Urban and Civil

Nov 16, 2013 (3 years and 7 months ago)

76 views

CE
496 B

Structural Design III

Spring 2011

Howard
Lum

Seismic Design Criteria

California Building Code (CBC) 2010

ASCE 7
-
Buildings and Other Structures

AISC 341
-
05 Seismic Design for Steel Buildings

American Concrete Institute (ACI 318
-
08)
Building Code Requirements for Structural
Concrete (Chapter 21)

Site Specific Geotechnical Report

Seismic Design

Seismic Accelerations
-

S
DS

and S
D1

Occupancy Category (OC) per CBC Table
1604.5 (our project
-

OC II)

Importance Factor I (our project, I=1.0)

OC and S
DS

and S
D1

-

determine Seismic Design
Category (SDC) per CBC Sect. 1613.5.6

SDC is used in:

Allowable seismic drifts

Seismic structural detailing

Seismic Design Category (SDC)

Reference: CBC Tables 1613.5.6

Dynamics of Structure

Single Degree of Freedom System:

Lumped mass
-

m

Single damping
-

c (5% typical)

Linear Stiffness
-

k

Period
-

T = 2
π

√m/k

Site Specific Response Spectrum

Earthquake Response Spectrum (ASCE 11.4
-
1)

Short)

S
DS

S
D1

T
L

T
S

T
0

Seismicity

Ss in g

S
1
in g

0.52 g

LB Response Spectrum (2005)

Use USGS data for current project

PGA

Tohoku Earthquake March 2011

PGA=2.70 g

Steel Properties

Fy

Fu

Seismic Design Methods

ASCE Table 12.6
-
1 provides 3 methods

Equivalent Lateral Force (ASCE 12.8)

Base shear static analysis

Lumped Mass at each level

Orthogonal directions of analysis

(transverse & longitudinal)

Modal Response Spectrum Analysis (ASCE 12.9)

Linear elastic dynamic analysis

Seismic Response History Analysis (ASCE Ch.16)

Non
-
linear dynamic analysis using time histories

Vertical distribution of Forces

Reference: ASCE 12.8.3

F
x

= C
vx

* V

where C
vx

= w
x
h
x
k
/∑w
i
h
i
k

w
1

V=F
1
+F
2

F
1 (upper deck)

F
2 (pipe support deck)

h
i

w
2

Horizontal Truss as Diaphragm

Strength Design (12.4.2.3) to ensure adequate
capacity

(1.2 + 0.2 S
DS
)D +

*Q
E
+ 0.5L

(0.9

0.2 S
DS
)D +

*Q
E

Drift Control (12.8.6) to limit content damage and
maintain building separation

Steel Structural Systems

Moment Frame

Concentric Braced Frame

Eccentric Braced Frame

Design of beam
-
column in a moment
frame

Combined Axial & Bending:

Moment resisting frames

Axial Force:

seismic overturning forces

Moment and Shear:

AISC Equations H1
-
1a & H1
-
1b

REQUIRED CAPACITY

P
r

P
c =

Pn

M
rx

M
cx =

Mn
x

M
ry

M
cy =

Mn
y

2
.
0

0
.
1
9
8

c
r
cy
ry
cx
rx
c
r
P
P
for
M
M
M
M
P
P
2
.
0

0
.
1
2

c
r
cy
ry
cx
rx
c
r
P
P
for
M
M
M
M
P
P
Large Axial Compression (>= 20%):

Small Axial Compression (< 20%):

Dynamic Analysis

Modal analysis

linear elastic response spectrum

Dynamic Analysis

Time History

Non
-
linear system

Seismic Retrofit Example

Base Isolators

24

Example

Landslide Protection

Before

After

Example

Pumping Plant
Seismic

Hinds Pumping Plant

Eagle Mountain
Pumping Plant

Example

Discharge