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Buckling Restrained Steel Shear Walls for Seismic Protection

X. Qian and A. Astaneh-Asl University of California, Berkeley

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Earthquakes create horizontal inertia forces in buildings

Horizontal inertia forces need to be resisted by lateral load resisting system

Lateral load resisting systems also resist lateral loads due to wind

Seismic Protection of Tall Buildings

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Lateral Load Resisting Systems:

Shear Walls Braced Frames Moment Frames

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Lateral Load Resisting Systems:

Braced Frames

http://www.aviewoncities.com/

Moment Frames

www.toptenepic.com/

Shear Walls

www.timgriffith.com

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What is a Steel Shear Wall?

The main role of a steel shear wall is to collect the lateral forces of earthquakes or winds in a building and transfer those forces, in shear, to the foundations and the ground.

• Steel shear walls studied here are steel plates welded to beams and columns in a building.

www.timgriffith.com

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Stiffened Steel Plate

Used in Japan Unstiffened Steel Plate

Used in U.S.A Steel plate shear walls are either “unstiffened” or “stiffened” . Stiffened steel shear walls have horizontal and vertical stiffeners to divide the plate to smaller panels that will not buckle until the entire plate has yielded in shear.

Types of Steel Shear Wall Panels:

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30-story Steel Shear Wall Building in Kobe Japan

After the 1995 Kobe Earthquake

1996

After the 1996 retrofit

Steel Shear Wall Building

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Seismic Studies of an Innovative Steel Shear Wall System

Objective: To develop an innovative steel plate shear wall system for wind and seismic lateral force resisting

Performance objective: limit the failure to first buckling under frequent earthquakes and design wind load, while allowing yielding of the shear wall system under maximum considered earthquake.

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RESEARCH METHODOLOGY

First Stage Current Focus

Conduct literature survey

Validate computational tools (ANSYS)

Establish seismic demand on the innovative system (ANSYS)

Optimize the system (ANSYS)

Develop tentative seismic design recommendations based on analysis

Apply the design guidelines to design steel shear walls for low-, mid- and high-rise buildings and possibly bridge applications

Conduct time history analysis of structures subjected to ground motions as well as wind effects using ANSYS and refine the design procedure

Design two specimens representing traditional and innovative shear walls and perform pre-test analysis of behavior under cyclic loading up to fracture failure using ANSYS

Fabricate and conduct cyclic tests of two 1/2 scale specimens that are designed using the proposed design procedures and based on their behavior further refine and finalize the design procedures.

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ANSYS ANALYSIS PLANS

• Validate FEA simulation – Use ANSYS to model existing test specimens and loading and compare its prediction of behavior of specimens to actual test results. (this presentation)

• Case Study Model: Jinta Tower in Tianjing, China • Designed by S.O.M.

• Test by Tsinghua University

• Generic Low-, mid-, and high-rise structures using proposed innovative “buckling restrained” steel shear walls

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VERIFICATION OF ANALYSIS SOFTWARE AND MODELING ISSUES

Tested specimen used in simulation:

from: Lubell, 1997)

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VERIFICATION OF ANALYSIS SOFTWARE AND MODELING ISSUES

Simulation of actual behavior of tested steel shear wall specimens using ANSYS:

(Photo: Curtsey of C. Ventura)) (Curves from: Lubell, 1997)

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CASE STUDY 1: 10 Scale Test Specimen

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Mesh The ANSYS

shell181 element

is used for infill

plates and

boundary

elements. Mapped

mesh is used .

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Boundary Conditions

Top Beams

and

Loading

Actuators

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Boundary Conditions

Bottom

Beam

Support

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Results Comparison between ANSYS Simulation and Test Results

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Results

Comparison between ANSYS Simulation and Test Results

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Results

The Problem with Plate Buckling and Column Bending

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Buckling of Plate and Bending of Columns

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Innovative Buckling Restraining Stiffeners

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ANSYS ANALYSIS PLANS

• Validate FEA simulation – Use ANSYS to model existing test specimens and loading and compare its prediction of behavior of specimens to actual test results. (this presentation)

• Case Study Model: Jinta Tower in Tianjing, China • Designed by S.O.M.

• Test by Tsinghua University

• Generic Low-, mid-, and high-rise structures using proposed innovative “buckling restrained” steel shear walls

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ANSYS ANALYSIS PLANS • Case Study Model: Jinta Tower in Tianjing, China

• Designed by S.O.M.

• Test by Tsinghua University

www.timgriffith.com

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Test details

Reference: Nie et al(2013)

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Test details cont.

SPSW1 (Not Buckling Restrained)

Total lateral load vs overall drift

Inter-story lateral load vs inter-story drift

SPSW2 (Buckling Restrained)

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• Using ANSYS we were able to simulate buckling behavior of two test specimens of steel shear walls.

• Also, using ANSYS, we simulated behavior of steel shear walls with vertical stiffeners acting as buckling restraining elements.

• This was our use of ANSYS and now we are embarking on simulating fracture crack initiation and propagation as well as cyclic yielding and buckling behavior simulation using ANSYS.

• The goal is to use ANSYS in developing an innovative buckling restrained steel shear wall for buildings to resist wind and seismic lateral forces.

Concluding Remarks

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We acknowledge and appreciate very valuable support and technical assistance received from Casey Heydari, Chris Cowan, and Cassandra Casteel , all of Ozen Engineering Inc.

Also, we appreciate the time and professional care that Ian Lockley and Ming Yao Ding, both of ANSYS Inc. spent with us in guiding us in our preparation of this presentation.

Acknowledgements