Research on Bearing Mechanism of Strut-and-Tie Model for Punching Failure of Independent Foundation Under Column

Through three-dimensional nonlinear finite element analysis, the punching failure’s bearing mechanism of the independent foundation under column whose slab is the size of 0.8m×0.8m×0.3m is obtained. The transfer mechanism of the foundation is spatial strut-and-tie model, where the reinforcements located in the link ranges between each adjacent corner of the slab are represented by ties, and the concrete distributed in the link ranges from the column bottom to four corners of the slab bottom are represented by struts. The indication of punching failure is that the concrete at the two ends of the struts reaches the shear-compression failure strength, and the punching cone is punched out relative to the slab, which has distinct punching failure features. A new spatial strut-and-tie model composed of four ties and four struts is proposed on the basis of clear bearing mechanism, which provides a new idea for the calculation of the punching bearing capacity of the independent foundation under column.

Shear Strengthening of Deep T-Section RC Beams with CFRP Bars

Deep T-section beams have been widely used in engineering structures due to their high bearing capacity, high construction efficiency and economic benefits, while the current beam design theory can hardly interpret reasonably the mechanical behaviors of deep beams. The performance features of the deep T-beam were investigated, involving in strain distribution and principal stress trace using experimental tests. Different near surface mounted (NSM) reinforcement schemes were proposed for deep T-beams aiming at improving the shear capacity. The results show that the behaviors of deep T-beams dissatisfy the assumption of plane cross-section, and the ‘strut-and-tie’ model is applicable in such structures. The reinforcement systems can significantly relieve the strain concentration, mid-span deflection and crack width in deep T-beams, consequently improving the shear capacity range from 45 to 65%. The scheme is preferential for the reinforcement of deep T-beams when the applied angles, positions and lengths of CFRP bars are optimized based on the ‘strut-and-tie’ model.