Experimental Performance of Three Story SCBF Systems

Eric J. LumpkinGraduate Student – University of Washington

Charles W. Roeder Professor – Principal Investigator (PI)

University of Washington

Dawn E. Lehman Assistant Professor – Co-PI

University of Washington

2009 NEES Conference

June 25, 2009

Po-Chien Hsiao Graduate Student

University of Washington

K.C. Tsai International Collaborator

Professor, Director of NCREE

NEES-SG Project Overview

Objective

To improve the seismic design of

SCBF systems and connections through

advanced models and full scale system

testing

University of California, Berkeley

July, 2009

NCREE University of Washington

MAST, University of Minnesota

Fall, 2009

NEES-SG Project Overview

• University of Washington – Develop improved design methods for SCBF’s– Establish a performance based design technique– Identifying and classifying yield and failure mechanisms

Brace Buckling Brace Yielding Gusset Plate Yielding

Column/Beam Yielding Brace Fracture

– In design, how do we ensure this yielding hierarchy occurs?

• Balanced design procedure (β)• Ensures ductility instead of resistance • Validated through 28, single bay, single story tests at UW

NCREE Test Setup

• More accurate boundary conditions than UW test setup– Tested vertically– Additional demands from

concrete slab– Fully restrained column bases

• Reused frame between tests– Simply removed and replaced

gusset plates and braces– Allowed for rapid testing

• Loaded applied to frame through top story slab

• Use of blue out-of-plane frame

Two Story Testing at NCREE (TCBF 1)

• Tomorrows Concentrically Braced Frame 1 (TCBF 1)– Two story, X-Brace configuration– 8t elliptical clearance on corner and middle gussets

8t

8t

Edge Stiffeners

Extension to Three Story Testing

• Investigation of unique gusset plate configurations– Chevron configuration – Gussets on either side of a beam

• Modification of middle gusset plate clearances• Eliminate middle gusset edge stiffeners

8t

6t

TCBF 2

TCBF 2-1

(HSS)

TCBF 2-2

(WF)

TCBF 2-3

(2t, IP)

Construction Drawings

Completed Specimen

TCBF 2-1 (HSS) Performance

Frame Drift: -1.74% to 2.08%

1st Story: -2.20% to 2.18%

2nd Story: -2.15% to 2.17%

3rd Story: -1.06% to 1.07%

TCBF 2 Test Series PerformanceTCBF 2-2 (WF)

Frame Drift: -2.43% to 2.43% Frame Drift: -1.74% to 1.74%

TCBF 2-3 (IP)

3.48%

4.86%

3.82%

Frame3rd Story

2nd Story1st Story

2.13%4.32%4.38%TCBF 2-1 (8t,HSS)

1.99%4.61%3.99%TCBF 2-3 (2t, IP)

2.99%5.74%5.21%TCBF 2-2 (8t, WF)

Drift Ranges

TCBF 2-2 (WF) 1st Story Video

Brace Buckling and Yielding

NS

TCBF 2-1 (HSS) TCBF 2-2 (WF)NS

TCBF 2-1 Middle vs. Corner Gusset PlateNS

NS Middle Gussets Corner Gussets

TCBF 2-2 Middle vs. Corner Gusset Plate

NS NS

3.05% SD

Middle Gussets Corner Gussets

Brace Fracture

NS NS

TCBF 2-1 (8t, HSS) TCBF 2-2 (8t, WF)

TCBF 2-3 Connection

• In-plane buckling detail– Achieved via rotation of a “knife plate”– Gusset plate to remain elastic– Majority of inelastic action in knife plate– 20 mm knife plate– 18 mm gusset plate– 2t hinge region on knife plate

2t

TCBF2-3 In-Plane Buckling Video

TCBF 2-3 Brace In-Plane Buckling

NS

1.06% SD 1.86% SD 2.32% SD

TCBF 2-3 Knife Plate Yielding and Rotation

NS NS

Preliminary Conclusions

• TCBF2-1 (HSS) and TCBF 2-2 (WF)– The type of brace has a large effect on system performance– WF braces more ductile than HSS braces however loose

strength rapidly post buckling – WF braces place a greater demand on the connections than

HSS braces– Elliptical clearance only valid for corner gusset plates– 6t horizontal offset allows for significant inelastic action while

limiting the occurrence of buckling

• TCBF 2-3 (In-Plane)– In-plane buckling SCBF’s similar to the performance of OOP

buckling SCBF’s– Knife plate connection allows for greater connection rotation– Increased serviceability

Acknowledgements

• K.C. Tsai and NCREE Staff– Chih-Yu Wei, An-Chien Wu, Ching-Yi Tsai

• My advisors – Dr. Charles Roeder and Dr. Dawn Lehman• Po-Chien Hsiao • NEES and NSF• Our advisory committee

Questions, Comments?