Outrigger-Belt and Frame Interaction in Composite Tall Buildings under Differential Axial Shortening

Abstract

This paper treats the interaction of outrigger-belt systems (OBS) with structural frames in high-rise buildings with composite columns caused by differential axial shortening (DAS). The presence of OBS significantly reduces DAS in composite buildings, but when used without belts, the DAS problem is aggravated. Current methods using results from elastic single-step or staged construction reduce the accuracy of DAS predictions and result in either unsafe or overconservative designs of OBS. For modern complex buildings, the comprehensive method used in this paper, which incorporates all the influencing factors including the outrigger-belt and frame interactions, provide more accurate results. Findings from the present study show that locations of OBS influence DAS considerably and can be used for minimizing DAS. Delayed connection of outrigger walls to perimeter columns can mitigate the adverse effects of DAS, with a delay of 1–2 weeks resulting in significant reductions in stresses developed because of DAS. Information generated in this paper will be useful for planning suitable methods for OBS analysis and to minimize adverse effects of DAS in composite high-rise buildings.