Event
CEE Faculty Candidate Seminar - Dr. Yunfeng Zhang
Friday, March 16, 2007
2:00 p.m.-3:00 p.m.
1173 Glenn L. Margin Hall - CEE Conference Rm.
Oscar Velasco
301 405 7768
ovelasco@umd.edu
Research Seminar: Seismic Behavior of Damage-Free Steel Braced Frame Systems with Self-centering Friction Damping Braces
Abstract
Recently, self-centering structural systems with flag-shaped hysteresis have attracted considerable interests due to their ability to control damage and to reduce (or even eliminate) residual structural deformation, after strong earthquakes. This talks will present the seismic behavior of a novel type of self-centering steel concentrically braced frame (CBF) systems with a special type bracing element termed self-centering friction damping brace (SDB). SDB serves as a passive energy dissipation device with its core self-centering component made of superelastic Nitinol stranded wires). Unlike conventional passive damping devices, SDB has the potential to minimize the residual drifts of CBFs after strong earthquakes and withstand several design basis earthquakes in seismic active regions such as California without the need for repair or replacement. Because friction provides energy dissipation in SDB (and thus reduced material consumption of Nitinol wires), SDB has a significantly reduced cost compared with other Nitinol-based damping devices. Experimental results from scaled SDB specimens will be presented in this seminar. A new strain-rate dependent thermomechanical constitutive model that was used in seismic simulation study of SDB frames will be described. A comparative study of SDB frame and buckling-retrained brace (BRB) frame was carried out, which is based on nonlinear dynamic analysis of 3-story and 6-story steel CBF buildings. The results of the nonlinear time history analysis show that the SDB frame can achieve a seismic response level comparable to that of the BRB frame while having significantly reduced residual drifts. Future research includes real-time pseudo-dynamic testing of large scale SDB frames.
About the speaker:
Dr. Yunfeng Zhang is an assistant professor in the Department of Civil and Environmental Engineering at Lehigh University. His primary research interest is in an integrated engineering field of smart structures technology and he has over 12-years experience in structural testing work including large scale testing of RC shear walls, shake table test, real-time pseudo-dynamic testing of structures with velocity sensitive damping elements, and field vibration test for finite element model updating. Dr. Zhang has also done work in fatigue assessment using advanced sensor technology. Dr. Zhang is a recipient of an NSF CAREER award in 2006. He holds a M.S. degree and B.S. degree in Civil Engineering from Tsinghua University and Tongji University, China, respectively. He earned his PhD degree in Applied Mechanics from Caltech in 2001.
