Comparison Between Punching Shear Capacity of PT and RC Slabs According to Different Design Codes

Abstract

The use of Post-tensioned (PT) concrete flat slabs has experienced consistent growth in recent years following a need for thinner slabs and longer span in multi-story structures. The use of PT provides many clear advantages in comparison to a regular reinforced concrete (RC) section, specifically when designed under Serviceability Limit States (SLS). The implementation of PT allows for a thinner slab profile. The reduction in slab thickness results in lighter structures with savings experienced to both sub and superstructure. Of the current 180 towers which have planning permission in London, it is expected that 70–80% will be executed in PT as opposed to the conventional RC slabs. Given the increased capacity at SLS as result of prestressing the Ultimate Limit State (ULS) requirement specifically relating to punching shear is becoming a critical factor in the determination of slab thickness. Previous investigations on punching of PT slabs have shown a number of phenomena significantly influencing their strength and behaviour. The influence of bonded PT on the punching shear resistance of a flat slab section with and without shear reinforcement will be investigated in this paper. The theoretical parameters that occur in the design punching shear resistance across EC2 (2004) and AS3600 (2009), and the reinforcement positioning in aspect of providing an increase in the monolithic slab punching shear capacity are to be reviewed. An analytical cross code investigation of the impact of bonded post-tensioning on the punching shear capacity of a PT section will be conducted.