Progressive collapse performances of outrigger-braced reinforced concrete buildings with transfer floor

This paper is mainly composed of a comprehensive evaluation and discussion on the progressive collapse performances of outrigger braced reinforced concrete structures with transfer floor. The effects of transfer floor existence, combined use of transfer floor and outriggers, outrigger locations on load redistribution, plasticity development and robustness of structural systems under the sudden failure of the element(s) are the fundamental issues that shape the content of this study. Within this scope, six reinforced concrete systems with transfer floor and differently located outriggers are modelled in SAP2000 finite element program. The pushdown curves are compared through the nonlinear static analysis. For external and corner column cases, the maximum load factors versus vertical drift ratios are obtained in systems with outriggers located at the midheight (0.5H) and top level (H), especially. The differences in deformation characteristics of transfer floor-element interface can be properly limited by modifying outrigger locations and combinations. The hinging development can be much more effectively controlled with outriggers close to the transfer floor. The same tendency is also observed while the vertical spacing between outriggers is decreased, particularly until 0.65H. The results support that the optimized outrigger use develops an efficient alternate load paths under the abrupt element failure.