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

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

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

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) + 0.25 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

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

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

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

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

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

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

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

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

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

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

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 Conclusions

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

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

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

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

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 22

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

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