This study examined the effect of the unit weight and compressive strength of concrete on the punching shear capacity of flat slabs without shear reinforcements. The slabs were prepared using all-lightweight aggregate concrete (ALWAC), sand-lightweight aggregate concrete (SLWAC) and normal-weight concrete (NWC) at the different compressive strengths of concrete of 24 and 45 MPa. Based on the upper-bound theorem of concrete plasticity, the failure surface generatrix is generalised to account for the increased horizontal extension with a decrease in the unit weight of concrete. Thus, the punching shear capacity of concrete flat slabs is mathematically driven considering the reduced effective strengths of lightweight aggregate concrete under tension and compression. Test results showed that the radius of the punching shear tended to increase with a decrease in the unit weight of concrete. This yielded a lower normalised punching shear capacity observed for ALWAC and SLWAC flat slabs than NWC flat slabs. The proposed model accurately estimated the punching shear capacity, indicating that the mean and standard deviation of the ratios between the experiments and predictions were 1.10 and 0.05, respectively. This indicated that the proposed model reasonably reflects the reduced aggregate interlock action of lightweight aggregates.

中文翻译：

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无抗剪钢筋轻骨料混凝土平板的冲剪承载力

本研究检验了混凝土的单位重量和抗压强度对无抗剪钢筋平板的抗冲切承载力的影响。使用全轻骨料混凝土 (ALWAC)、砂轻骨料混凝土 (SLWAC) 和普通重量混凝土 (NWC) 在 24 和 45 MPa 的不同抗压强度下制备板。基于混凝土塑性上限定理，破坏面母线被推广以解释随着混凝土单位重量的减少而增加的水平延伸。因此，考虑到轻骨料混凝土在拉伸和压缩作用下的有效强度降低，混凝土平板的冲剪承载力是数学驱动的。试验结果表明，随着混凝土单位重量的减小，冲剪半径有增大的趋势。对于 ALWAC 和 SLWAC 平板，这产生了比 NWC 平板更低的归一化冲压剪切能力。所提出的模型准确地估计了冲压剪切能力，表明实验与预测之间的比率的平均值和标准偏差分别为 1.10 和 0.05。这表明所提出的模型合理地反映了轻骨料减少的骨料连锁作用。表明实验和预测之间比率的平均值和标准偏差分别为 1.10 和 0.05。这表明所提出的模型合理地反映了轻骨料减少的骨料连锁作用。表明实验和预测之间比率的平均值和标准偏差分别为 1.10 和 0.05。这表明所提出的模型合理地反映了轻骨料减少的骨料连锁作用。