1. Colorado State University
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

2. Overview Introduction Structure Design Hybrid Simulation Approach
Experimental module
Analytical module
Experimental Results and Observations
Conclusion
Questions

3. 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

4. Subassembly FEM Analysis Frame with rotational springs
Current Limitations
Subassembly FEM Analysis
Experimental Testing
Realistic M-q
Frame with rotational springs
Idealized M-q
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

5. Experimental Component
Specimen Design
The structure is 2-story, 4-bay longitudinal and 2-bay transverse
The lateral load resisting system is SMRF designed using IBC 2006
Load combination of 1.0 DL + 10 psf (partitions) LL + EQ
SMRF, Typ.
13.5 ft
15 ft
30 ft
W 18 x 40
W 14 x 159
Experimental Component
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

6. 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
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

7. Hybrid Simulation Approach
Calc. forces
Target Disp.
Computational: FEA
Simulation
Coordinator
{u}
{F}
Measured
forces
Experimental: LBCB
Measure forces
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

8. Small-Scale Validation
Small-Scale Setup
Rubber
Small-Scale Setup
Steel
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions 8

9. Small-Scale Validation
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions 9

10. Control Development x2,y2,dq2 (x2+dx2, y2+dy2, dq2)
LBCB1 X
x3,y3,dq3
[T]
LBCB2
(x1+dx1, y1+dy1, dq1)
x1,y1,dq1
Fixed B.C.
[T]-1 Y q X
SIMCOR Space
(3 control points)
LBCBs Space
(2 control points)
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

11. Control Development Elastic deformation Problem Definition Solution
LBCB platform movement controlled internally
LBCB frame, reaction wall/floor have finite stiffness
Internal actuator displacements include both specimen and external deformations
Solution
An external measurement and feedback system was developed
3 DOF (x,y, rz) for each LBCB for a total of 6 DOFs
System of 6 high tension string pots with low friction connections
Precisely monitors and accounts for the movement of the LBCB platform in space
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

12. Full-Scale Setup 12 Introduction Structure Design Exp. Module
Ana. Module
Results
Conclusions 12

13. Control Development Instrumentation Control 13 Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions 13

14. Instrumentation Global Local Still images and videos Global drift
Global strain
M-q
Local
Bolt slip
Localized strain
Angle deformation relative to the beam and column
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

15. Cyclic Loading of the Model
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions 15

16. 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

17. Hybrid Results Introduction Structure Design Exp. Module Ana. Module
Conclusions

18. Hybrid Simulation Results (local)
43.6% Mpbeam
82% Mpbeam
65.2% Mpbeam
Hybrid 30% Mpbeam
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

19. Hybrid Simulation Results (global)
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions

20. Hybrid Simulation Results (global)
IDR limit of 5%
IDR limit of 2.5%
Introduction
Structure Design
Exp. Module
Ana. Module
Results
Conclusions 20

21. 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 21

22. Conclusions (cont.)
The corresponding rotations are rad, rad, and 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 22

23. 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

24. Questions