混凝土板带平裂段曲母线冲切锥组合模型

针对受冲切混凝土板中常存在水平受拉劈裂段情况，基于二次抛物线屈服准则，考虑冲切斜锥面混凝土受压和纵筋平面内混凝土受拉极限并存的临界状态，建立了带有沿纵筋平面水平劈裂段（简称平裂段）的曲母线冲切破坏斜锥面组合错动模型，求得了冲切承载力上限解，并进一步推广导出了任意次（含二次）抛物线准则下的冲切抗力统一解；基于理论解，对二次抛物线准则冲切模型进行了简化和可靠度计算，结果表明，简化公式计算值与试验值（231块板）之比的变异系数为0.201，离散性较直母线破坏斜锥面带平裂段组合模型（0.250）更小，且略优于规范公式（0.202），均值为0.940，明显优于现行规范（0.799），可供工程设计应用。

A Refined Punching Model for Concrete Slabs with Horizontal Cracking Zone

Based on the yield criteria of second-order parabola, a refined translational model for punching failure has been developed, assuming that the critical ultimate state is characterized by cracking of the compression concrete on the punching cone and simultaneous splitting of the tension concrete at longitudinal-rebar level. An upper-bound solution was obtained and a general one was developed under arbitrary-order parabola yield criteria. Moreover, the deduced complex model was simplified for better practice. The statistical results, with a collection of 231 specimens, show that for the proposed curved-generatrix model, the coefficient of variation for the prediction-to-observation ratios（i.e.,0.201） is much less than that for the straight-generatrix model previously proposed（i.e.,0.250）. In addition, it is slightly lower than that for the current GB code（i.e.,0.202）, and its mean（i.e.,0.940） is obviously superior over the latter（0.799）.