Mid-America Earthquake Center
Hybrid Simulation for the Assessment of
Semi-Rigid Partial-Strength Steel Frames in
Seismic Regions
Quake Summit 2012
July 11, 2012
Boston, Massachusetts
Hussam N. Mahmoud, Ph.D.
Colorado State University
Overview
• Introduction
• Structure Design
• Hybrid Simulation Approach
- Experimental module
- Analytical module
• Experimental Results and Observations
• Conclusion
• Questions
Damage to Welded Connections
• Numerous examples
of brittle fracture of
welded moment
connections,
Northridge (1994),
Kobe (1995)
• Fracture initiation at
the connection
(backing bar detail)
-
Poor design practice
Poor toughness
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Current Limitations
Subassembly FEM Analysis
Experimental Testing
kq2
Moment
Rotational
spring
Realistic M-q
kq1
Rotation
Frame with rotational springs
Idealized M-q
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Specimen Design
• The structure is 2-
Introduction
Structure Design
Exp. Module
30 ft
30 ft
30 ft
30 ft
W 14 x 159
13.5 ft
30 ft
15 ft
story, 4-bay
longitudinal and 2bay transverse
• The lateral load
resisting system is
SMRF designed
using IBC 2006
• Load combination
of 1.0 DL + 10 psf
(partitions) + 0.25
LL + EQ
SMRF, Typ.
W 18 x 40
Experimental Component
Ana. Module
Results
Conclusions
30 ft
Specimen Design
• Connection is
designed as top-and
seat-angles with
double web-angles
• According to EC 3
with capacity of 70%,
50%, and 30% of the
beam plastic moment
Connection Capacity
70% Mpbeam
50% Mpbeam
30% Mpbeam
Introduction
d
(in)
17.9
17.9
17.9
Structure Design
lt = l
tt = t
T
(in)
1-3/16
1-3/16
1-3/16
k
(in)
3
3
3
Exp. Module
f(Fastener Dia.) = W
Flange Angle
ga
Top Angle
Kt
Web Angle
la
Ks
p
Seat Angle
ts (thickness of seat angle) and ta (thickness of web angle)
ls
La
(in)
8
8
8
ts
(in)
1
3/4
1/2
Ana. Module
ta
(in)
5/8
1/2
3/8
l
(in)
16
14
14
Results
ga
(in)
2-3/4
2-3/4
2-3/4
p
(in)
5-1/2
5-1/2
5-1/2
Conclusions
G
(in)
3
3
3
W
(in)
1-1/4
1
1
Hybrid Simulation Approach
Calc. forces
Target Disp.
Simulation
Coordinator
Computational: FEA
{u}
{F}
Measured
forces
Experimental: LBCB
Measure forces
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Small-Scale Validation
Introduction
Small-Scale Setup
Small-Scale Setup
Rubber
Steel
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Small-Scale Validation
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Control Development
x2,y2,dq2
(x2+dx2, y2+dy2, dq2)
Y
(x3+dx3, y3+dy3, dq3)
LBCB1
q
X
LBCB2
x3,y3,dq3
[T]
(x1+dx1, y1+dy1, dq1)
x1,y1,dq1
Fixed B.C.
[T]-1
Y
q
X
Introduction
SIMCOR Space
LBCBs Space
(3 control points)
(2 control points)
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Control Development
•
Elastic deformation
- Solution
Problem Definition
-
An
external
measurement
feedback
system was developed
LBCB
platform
movement and
controlled
internally
3
DOFframe,
(x,y, rz)reaction
for each
LBCB for
a total
of stiffness
6 DOFs
LBCB
wall/floor
have
finite
System
6 high displacements
tension string pots
withboth
low specimen
friction connections
Internal of
actuator
include
and external
deformations
Precisely
monitors and accounts for the movement of the LBCB platform in
space
Elastic
box
K2
F = f2(u2)
u2
F
Rigid
actuator
F
F = f1(u1)
Inelastic
specimen
u1
K1
x
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Full-Scale Setup
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Control Development
Instrumentation
Introduction
Structure Design
Control
Exp. Module
Ana. Module
Results
Conclusions
Instrumentation
• Global
- Still images and videos
- Global drift
- Global strain
- M-q
• Local
- Still images and videos
- Bolt slip
- Localized strain
- Angle deformation relative
to the beam and column
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Cyclic Loading of the Model
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Record Selection
• The Loma Prieta, PGA
= 0.26 g
• USGS 1662 Emeryville,
77 km from the
epicenter
• Soft soil (Vs = 199 m/s)
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Hybrid Results
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Hybrid Simulation Results (local)
43.6% Mpbeam
82% Mpbeam
65.2% Mpbeam
Hybrid 30% Mpbeam
70% Mpbeam
50% Mpbeam
30% Mpbeam
Introduction
ki
(kips.in/rad)
510,683
494,314
306,521
Structure Design
ku
(kips.in/rad)
390,827
266,718
203,565
Exp. Module
kdeg
(%)
23.47
46.04
33.59
| M |Max
(kips.in)
3,222
2,556
1,708
Ana. Module
%Mpbeam
82.0
65.2
43.6
Results
qMax  Energy Dissipated
(kips.in.rad)
(rad)
0.0196
195.18
0.0271
177.45
0.034
109.56
Conclusions
Hybrid Simulation Results (global)
70% Mpbeam
50% Mpbeam
30% Mpbeam
Introduction
Structure Design
| 2nd |Max
(in)
6.48
7.17
7.13
Exp. Module
| 1st |Max
(in)
2.89
3.35
2.84
Ana. Module
| Base Shear |Max
(kips)
281.6
253.6
202.8
Results
Conclusions
Hybrid Simulation Results (global)
IDR limit of 5%
IDR limit of 2.5%
1 st
ID R M ax
(% )
70% Mpbeam
50% Mpbeam
30% Mpbeam
Introduction
1.61
1.86
1.58
Structure Design
1 st
2 nd
1 st
ID R M a x
ID R M ax
ID R M ax
ID R
DBE
ASC E 41
0.322
0.372
0.316
Exp. Module
ID R
MCE
ASC E 41
0.644
0.744
0.632
Ana. Module
2 nd
ID R M ax
ID R
(% )
2.32
2.42
2.70
2 nd
ID R M ax
0.464
0.484
0.540
Results
D BE
ASC E 41
MCE
ID R ASC E 41
0.928
0.968
1.080
Conclusions
Conclusions
A new Hybrid simulation approach for the seismic
evaluation of semi-rigid steel frames is executed
• Three simulations were conducted
• Large hysteretic loops characterize the connection
behavior
• No failure in any of the connection components
• The maximum moment sustained by the 70%
Mpbeam, 50% Mpbeam, and 30% Mpbeam connections is
3,222 kips.in (82% Mpbeam), 2,556 kips.in (65%
Mpbeam), and 1,708 kips.in (43% Mpbeam),
respectively
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Conclusions (cont.)
• The corresponding rotations are 0.0196 rad, 0.0271
rad, and 0.3400 rad, respectively
• The procedure used to scale the records does not
allow for direct comparison with the interstory drift
limits in ASCE 41-10
• The 50%Mpbeam and 70% Mpbeam frame are deemed
acceptable for LS limit state (DBE) while the
30%Mpbeam violates the requirements as its roof
drift ratio is calculated to be 2.70%, which is
slightly higher than the limit of 2.5% for DBE
• For the expected maximum period elongation, the
demand is always higher than the DBE and in
some cases even higher than the MCE
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions
Acknowledgements
•
•
•
•
Dr. Elnashai, Dr. Spencer, and Dr. Kuchma
Fellow former graduate students at UIUC
NEES staff at UIUC (MUST-SIM)
The analytical and experimental investigations
on the steel frames were supported by the
MAE Center
• The experimental investigation was supported
by NEES (shared-use)
Mid-America Earthquake Center
Questions