Study Of Pushover Test Of Zipper Frames

Based on the conventional chevron braced steel frame system, an innovative structural system, so-called zipper frames, has been quickly developed in recent years, in which a vertical member(zipper strut) is added at the brace-to-beam intersections of chevron braced steel frames. Now, comparatively little research has been performed on the seismic behavior of the zipper frames. In this paper, the seismic responses of zipper frames, including the limit bearing capacity, lateral stiffness, failure mode and force transmission way of members, were studied through the pushover tests. The specific research contents of this paper are as follows:1) Based on the modified suspend zipper frames structure design method, a three-story zipper frame prototype structure had been designed and then, two 1:2.6 scale test models were designed according to the prototype structure. The braces at 1, 2 floors for two models were slightly different. The pushover tests on the test models were carried out by a series of stages. The response of structure, including the test phenomena, the lateral displacement and the stress response of the main members, indicates that the modified suspend zipper frame structural system can meet the requirements of “no damage under frequent earthquake”, “repairable level under occasional earthquake” and “no-collapse under rare earthquake” provided by the GB50011 code. On the whole, the modified suspend zipper frames show good seismic performance under the pushover test.2) Through the finite element analysis software of ABAQUS, a non-linear numerical analysis about the pushover test was conducted, and the simulated results were compared with the test ones. In general, they agreed well with each other. This indicates the numerical model is reasonable and the beam element is suitable for modeling dynamic response of the zipper frames under earthquakes.