Numerical investigation of concrete filled buckling restrained braces

Abstract

Conventional concentric bracing experiences buckling when subjected to loading in compression. To overcome this limitation, the Buckling-Restrained Braces were devised in Japan in the middle of 70 s. These braces contain a steel core enclosed with a restrainer. Frames equipped with buckling restrained braces have been extensively used in current years for wind and earthquake load resistant structures. Such frames offer almost similar behavior in tension and compression and therefore yield without significant buckling. This is how it offers a better alternative to conventional frames. In other words, a buckling restrained braced frame is a type of conventional braced frame which prevents the buckling of brace under compression. This paper presents the development of a numerical model for the tested BRBs in ANSYS WORKBENCH 16.0 by using the Finite Element Method. Five models of different outer tube configuration and same core size cross-section shapes were modelled and analyzed, thereafter their behavior was studied from the hysteresis curves obtained. The material and geometrical nonlinearities of the models based on experimental data are considered. This paper explores the design parameters that influence BRB and the common failure modes in the brace are witnessed. The FE models are precisely verified for experimental results described in the literature and satisfactory connection is detected. The confirmation of the validity of these models was established after comparing the results of numerical analysis with the experimental. In this study, hysteresis curves for all the five specimens were made and a fair agreement was observed of these curves with the stable hysteretic behavior of BRBs as expected. It can be observed from the study that unless the yielding load of the core member exceeds the Euler buckling load of the restrainer member, the brace will not buckle. It can be concluded that buckling restrained braces provide an economical and effective way of improving the seismic protection of structures such as tall and special buildings.