Xu, Fan, Li 2020
A new self-centering and energy dissipative steel braced system in this study consisting of a prepressed spring was investigated for its seismic performance. The system was tested under low reversed cyclic loading and on four- and eight-story buildings using a proposed nonlinear mechanical model. The results were compared with conventional steel braced frames (CSBFs) for further analyses. It was observed that the proposed innovative prepressed spring self-centering energy dissipation (PS-SCED) brace system had significantly less maximum interstory drift than that of CSBFs at different hazard levels and exhibited low absolute peak accelerations. An increase in floor acceleration, however, was observed due to an increase in contact friction among the springs and should be avoided in further studies by ensuring contact friction is minimized.
System Concept
The proposed brace is made of two tube members and comprises a combination of a friction energy dissipation mechanism (FEDM) and a self-centering mechanism (SCM). The FEDM consists of inner and outer plates, nonasbestos organic friction pads, and two high-strength bolts where it dissipates energy once it experiences motion between inner and outer tubes. The SCM is composed of two sets of prepressed combination disc springs, and an array of free-floating spring plates. The mechanism ensures only compression is experienced by the disc springs between free-bloating spring plates regardless of whether the entire brace is compressed or stretched. The restoring force that contributes to the SCM is provided by this deformation.
Experimental Study, Results, and Discussion
The seismic performance of the proposed braced system was evaluated by experimentation of two prototype structures equipped with PS-SCEDs in comparison with two other prototype structures constructed with CSB. Both four-story and eight-story structure design of the braces were tested. LS-DYNA program was used to evaluate the self-centering and energy dissipation performance of the proposed system by confirming its hysteretic behavior. For further nonlinear dynamic analyses, the braced frames were subjected to different types of ground motion at three
hazard levels where each peak interstory drift ratio, peak residual deformation ratio and normalized response parameter of acceleration were analyzed.
The results demonstrated similar initial stiffness for both designs. As anticipated, the PS-SCED braces largely reduced the maximum interstory drift of structures and improved interstory drift-ratios at every hazard level, which was due to the effective energy dissipation by the FEDM. Both peak absolute acceleration and residual deformations were also reduced by the SCM of the brace members in the system.
According to the results of the experimentation, it can be concluded that the proposed PS-SCED braces would be an effective solution to improve seismic performance of buildings due to its high self-centering ability and energy dissipation capacity compared to the performance of conventional steel braced frames.
Reference
Xu, Longhe, et al. “Seismic Assessment of Buildings with Prepressed Spring Self-Centering Energy Dissipation Braces.” Journal of Structural Engineering, vol. 146, no. 2, Feb. 2020, p. 04019190. DOI.org (Crossref), https://doi.org/10.1061/(ASCE)ST.1943-541X.0002493.