源于纵筋面混凝土劈裂的无腹筋板冲切模型

Modeling of Punching Failure Initiated by Concrete Splitting at Longitudinal Bar Level for Slabs without shear reinforcement

以工程中常见的配筋率较大(>0.85)、厚度较小(≤120 mm)的板为对象,通过对冲切破坏特征的观察分析,假定沿纵向钢筋平面,混凝土劈裂所致的纵筋销栓失效为连锁破坏源,建立了新的错动冲切模型并推导了上限解。研究发现,与按搜集到的构件样本总体分析结果相比(均值为1.072,变异系数为0.250),符合上述特征的试件组,其冲切承载力理论计算值和试验观测值之比的均值变化不大(为1.017),而变异系数有显著降低(为0.184),说明所作假定及所建模型用于描述该类板的受力行为是合适的。

A new punching failure model has been developed for thinner slabs（≤120 mm thick） yet with a larger reinforcement ratio（0.85）.On the assumption that the trigger of ultimate failure is the loss of dowel action caused by concrete splitting along the horizontal surface at longitudinal bar level,an equilibrium equation was established and an upper-bound solution was obtained.The computation of punching shear capacity shows that for a total of 194 specimens collected,the mean and the coefficient of variation are 1.072 and 0.250 respectively.As for the 116 members（out of all 194 ones） with the above character,it is found that there is little change of the mean（equal to 1.017） yet an apparent decrease in the coefficient of variation（equal to 0.184）,which justifies the proposed hypothesis and refined mode in estimating punching resistance of such members.