High-rise reinforced concrete (RC) flat plate slabs are highly vulnerable to punching shear failure, mainly when temporary shoring/reshoring systems support immature slabs during construction. Despite their widespread use, limited research examined the punching shear behavior of these slabs without shear reinforcement at early concrete ages, and existing building codes provide inconsistent results. This inconsistency and a lack of framework for predicting safety during construction using shoring/reshoring increase the risk of failure since applied loads typically exceed designed ones, and young concrete may not ultimately sustain them. This study proposes a time-dependent factor of safety (FoS) that accounts for punching shear capacity and fluctuating load distribution between slabs and shores/reshores during construction. Six interior slab-column elements without shear reinforcement were tested at various concrete ages. Unlike many building codes, flexural reinforcement increased punching shear capacity but less at lower concrete ages, highlighting the necessity for precise safety predictions in the preconstruction phase. Also, an empirical formula was proposed to predict the punching shear capacity of RC flat plate slabs without shear reinforcement. Based on a vast set of experimental data from previous studies, the formula presented superior accuracy compared to building codes, with a mean load capacity ratio (μ) of 1.04, a coefficient of variation (CoV) of 14.2%, and a coefficient of determination (R2) of 0.93. Finally, a recent method was used to analyze slab-shore/reshore load distribution to evaluate the FoS for two examples. The risk of structural failure was predicted for one of the examples in some construction steps. Then, for such predicted structural failure, increasing any of the cycle times, numbers of shoring levels, grades of concrete, thicknesses of the slab at the critical sections, or reinforcement percentages was emphasized. This study enhances safety standards and optimizes construction procedures, reducing failures and improving building integrity during critical construction.
Shaikhjan et al. (Fri,) studied this question.