Hybrid Tests of Steel Concentrically Braced Frame using In-Plane Buckling Braces Keh-Chyuan Tsai, Wai-Hang Ao, Ching-Yi Tsai Kung-Juin Wang and An-Chien Wu Department of Civil Engineering, National Taiwan Uninversity (NTU) National Center for Research on Earthquake Engineerng (NCREE) Taipei, Taiwan The 4 th Kwang Hua Forum and Opening Symposium of Tongi Shaking Table Array December 11-12, 211 Shanghai
Introduction Knife Plate Out-of-plane buckling Gusset Plate In-plane buckling
Energy Dissipation: Brace yielding, buckling and gusset plate deformation
Outline Research on Steel Braced Frames Hybrid Test Results FEM Simulations Conclusions
FULL-SCALE MULTI-STORY STEEL BRACED FRAME TESTS Collaboration among NCREE, University of Washington, University of California Berkeley University of Minnesota 27 (NEES-SG). Different brace types and the design criteria adopted for the gusset plates Testing under cyclically increasing displacements
Tests of the 3-story Braced Frame 1 st TCBF-HSS-8t (1DOF) (29/1/17) 2 nd TCBF-WF-8t (1DOF) (29/3/28) 3 rd TCBF-IB-HSS (1DOF) (29/5/16) 4 th Hybrid Test of the BRBF 53-gal LA3 Phase I (3DOF) (21/6/3) 5 th Hybrid Test of the BRBF 53-gal LA3 Phase II (3DOF) (21/8/29) 6 th Cyclic Test of the BRBF (3DOF) (21/8/29) 7 th Hybrid Test of the SCBF (3DOF) (21/1/16)
Knife Plate Design Knife plate connects to the gusset plate. Must sustain the maximum brace axial force and rotation from the brace buckling. Failure modes include (1) block shear failure (2) welding fracture
Test program Component test system. Connector Reaction block
CH22 Test result CH22 Knife Plate(mm) Gusset Plate(mm) kl/r Pcr(kN) 2 2 68 1585 D buckle =487mm Strain (%) 2-1 1 2
-2-8 -4 4 8 Axial Disp (mm) TH162 Test result TH162 Knife Plate(mm) Gusset Plate(mm) kl/r Pcr(kN) 16 2 69 1439.7 D buckle =474mm Axial Force (kn) 2 1-1 Strain (%) -2-1 1 2 Component test TH162
CH22 Local behavior +2.% Brace strain +1.5% Brace strain +2.5% Brace strain
Summary of Brace Component Tests In-plane buckling deformation of the braces can be greater than 4 mm when the brace strain reached.2. Comparing the fabrication cost and the constructability, TH connection detail is recommended for the construction of the brace end-to-gusset joint for SCBF hybrid tests. TH
3-story SCBF Hybrid Simulation Objectives Study the connection design of the in-plane buckling braces. (A36, H15x15x7x1mm) Validate the analytical model. Hybrid simulation software development.
11m 3-story SCBF hybrid simulation test specimen design Floor Framing Plan CBF CBF 6m 9m 9m 9m 9m 9m Floor area: 765 m 2 Mass: 178.98 T / each floor 1 st vibration period:.429 sec Design base shear: 97 T
Brace Section and Lengths SCBF specimen Location Type Section (mm) Length of Brace (mm) 3 rd story TH H15x15x7x1 297 2 nd story TH H15x15x7x1 2962 1 st story TH H15x15x7x1 2899 Area A g = 396 mm 2 Yield strength P y = 117 T (1152 kn) 1 st story brace buckle strength P cr = 82T (84 kn)
Gusset plate design Using UFM to design the gusset of the 3- story frame The brace section is H15x15x7x1 (A36) 19 6 11 2 mm Knife Plate. Gusset plate= 2mm 23 Knife plate = 2mm
Gusset Plate Details Gusset Plates: 2mm Knife Plates: 2mm
OpenSees 2D Model.1% imperfection of brace length Each brace is subdivided into 8 fiber BC elements.
OpenSees Cyclic Static Analysis 2 Axial Force (kn) 1-1 OpenSees 1F -2 -.4 -.2.2.4 Inter-story Drift(rad.)
OpenSees Cyclic Static Analysis Calibrate OpenSees analytical model by using 3E to simulate the behavior of gusset plates. 3E OpenSees ABAQUS
OpenSees Cyclic Static Analysis Calibrate OpenSees analytical model by using 3E to simulate the behavior of gusset plates. 3E 3 2 Base Shear(kN) 1-1 -2 OpenSees ABAQUS OpenSees -3 ABAQUS -.3 -.2 -.1.1.2.3 Roof Drift(rad)
OpenSees 2D Model 1.3*E Damping ratio:.3 % Specified according to the free vibration test and the 5-gal LA3 test results 1 st Mode Period:.456 second
Analytical predictions for the 3-story BRBF 2 ground motions: SAC LA1~LA2 475 years return period These 2 ground motions are scaled to the same spectral acceleration (1.7g) with T=.6 sec in the response spectra. Max. roof drift Max. actuator demands Max. base shear
Accleration(g) Accleraction(g).8.6.4.2 -.2 -.4 -.6 2.5 2 1.5 1.5 Ground motions used in 3-story SCBF hybrid simulation Ground LA3 time history Response spectrum 1.7 g 5% Damping.429 sec.2.4.6.8 1 1.2 1.4 1.6 1.8 2 Period(sec) Time duration of EQ LA3: 2 sec PGA: 597 gal 5 1 15 2 Time(sec)
Predictions Made Before the Test 3rd Floor Disp. (mm) 4 2-2 -4 S N OpenSees Test 4 8 12 16 2 Time (sec.) Roof Floor Disp. (mm) 2nd Floor Disp. (mm) 4 2-2 OpenSees Test -4 4 8 12 16 2 Time (sec.) 2 1-1 -2 OpenSees Test 4 8 12 16 2 Time (sec.)
S Story Shear vs. Story Drift N Base Shear (kn) 2nd Story Shear (kn) 3 2 1-1 -2 OpenSees Test -3-6 -3 3 6 3 2 1-1 -2-3 Roof Drift (% rad.) OpenSees Test -6-3 3 6 2nd Story Drift (% rad.) 3rd Story Shear (kn) 1st Story Shear (kn) 3 2 1-1 -2 OpenSees Test -3-6 -3 3 6 3 2 1-1 -2-3 3rd Story Drift (% rad.) OpenSees Test -6-3 3 6 1st Story Drift (% rad.)
1 st Story
1 st Story Gusset
In-plane Buckling Deformation Buckling Disp. (mm) 6 4 2 North South -6-4 -2 2 4 6 1st Story Drift (% rad.)
Floor Disp. and Inter-story Drift Inter-story Drift (% radian) 3 rd Story 2 nd Story 1 st Story North (+).54 3.4 4.76 South (-).52 4. 4.94
Maximum Lateral Displacemets Story 3 2 1 OpenSees Test -4-2 2 4 Floor Disp. (mm)
Maximum Drifts and Shears 3 3 2 2 Story 1 OpenSees Test -4-2 2 4 Story Drift (% rad.) Story 1 OpenSees Test -2 2 Story Shear (kn)
Test Summary Roof Disp. (mm) 4 2-2 1 2 3 4 Pause 1 for photograph -4-4 4 8 12 16 2 Pause 1: Column fractured 1NB Local Buckled 4: 2SB Buckled 1: 1SB Buckled Pause 2 for photograph Time (sec.) Pause 2: 1SB Local Buckled 4 2-2 3: 2NB Buckled 2: 1NB Buckled Roof Drift (% rad.)
Column Flange Fractured at 5.67 sec. EQ Time Roof Disp. (mm) Base Shear (kn) 4 2-2 232mm -4 4 8 12 16 2 4 2-2 -4 Time (sec.) 4 8 12 16 2 Time (sec.)
At 6.45 sec. EQ time Roof Disp. (mm) Base Shear (kn) 4 2-2 -4 4 8 12 16 2 4 2-2 -4-263 mm Time (sec.) 4 8 12 16 2 Time (sec.)
After 597-gal Hybrid Test
Conclusions A ductile knife-plate to gusset connection detail is developed and verified in the hybrid tests. Peak inter-story drift reached 5% rad. without brace or connection fracture. Column flange fractured after reused in 7 different cyclic or hybrid tests. Max. in-plane buckling displacement is 58 mm in the 1SB in 1 st story. Fundamental period of the specimen changed from.46s to 1.15s after the LA3 hybrid test
Tests of the 3-story Braced Frame 1 st TCBF-HSS-8t (1DOF) (29/1/17) 2 nd TCBF-WF-8t (1DOF) (29/3/28) 3 rd TCBF-IB-HSS (1DOF) (29/5/16) 4 th Hybrid Test of the BRBF 53-gal LA3 Phase I (3DOF) (21/6/3) 5 th Hybrid Test of the BRBF 53-gal LA3 Phase II (3DOF) (21/8/29) 6 th Cyclic Test of the BRBF (3DOF) (21/8/29) 7 th Hybrid Test of the SCBF (3DOF) (21/1/16)
Displacement (mm) 3 2 1-1 -2 BRBF Test1 BRBF Test1 Results 1st Floor 2nd Floor 3rd Floor -3 4 8 12 16 2 Time (sec) Story Shear (kn) 3 2 1-1 -2 LA3 PGA 53 gal BRBF Test1-3 -6-3 3 6 3 rd Story Drift (% rad) LA3 PGA 53 gal BRBF Test1-6 -3 3 6 2 nd Story Drift (% rad) LA3 PGA 53 gal BRBF Test1-6 -3 3 6 1 st Story Drift (% rad)
Displacement (mm) 3 2 1-1 -2 BRBF Test2 BRBF Test2 Results 1st Floor 2nd Floor 3rd Floor -3 4 8 12 16 2 Time (sec) Story Shear (kn) 3 2 1-1 -2 LA3 PGA 53 gal BRBF Test2-3 -6-3 3 6 3 rd Story Drift (% rad) LA3 PGA 53 gal BRBF Test2-6 -3 3 6 2 nd Story Drift (% rad) LA3 PGA 53 gal BRBF Test2-6 -3 3 6 1 st Story Drift (% rad)
Displacement (mm) 3 2 1-1 -2 SCBF SCBF Test Results 1st Floor 2nd Floor 3rd Floor -3 4 8 12 16 2 Time (sec) Story Shear (kn) 3 2 1-1 -2 LA3 PGA 597 gal SCBF -3-6 -3 3 6 3 rd Story Drift (% rad) LA3 PGA 597 gal SCBF -6-3 3 6 2 nd Story Drift (% rad) LA3 PGA 597 gal SCBF -6-3 3 6 1 st Story Drift (% rad)
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