Comparative Analysis of Mechanical Performance of Flat Slabs with Reverse and Conventional Column Caps

Compared with the conventional column caps, the reverse column caps that are used for slab-column joint of basement roof can improve the clearance of the basement while ensuring structural safety, and they are hidden in the covering soil without affecting the appearance and use of upper surface of flat slabs. In this paper, four finite element models, which are loaded by column-end displacement-control mechanism, are established. These models are used to investigate the mechanical performance of slab-column joint for flat slabs with reverse and conventional column caps. The obtained numerical results were thoroughly analysed, indicating that the load-carrying capacity performances of flat slabs with conventional column caps are much higher than their counterparts with reverse column caps, but flat slabs with conventional column caps possess lower mechanical ductility. Moreover, the reverse column caps were found to exhibit a severe damage at ultimate load; therefore, transverse stirrups were distributed into the reverse and conventional column caps for the purpose of comparison. The comparison results revealed that the ultimate load of the slab-column joints with reverse column cap can be increased by 2.4% by arranging transverse stirrups in column cap, but the ductility is decreased by 13.4%. For the slab-column joints with conventional column cap, the ultimate load is decreased by 10.0% and the ductility is decreased by 1.6% when transverse stirrups are arranged in column cap. Therefore, arrangement of transverse stirrups in column cap should be determined based on the actual situation in the flat slab system with reverse column cap, and it is not recommended to arrange transverse stirrups in column cap in the flat slab system with conventional column cap.

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