中美欧日规范独立基础冲剪计算对比研究

The Comparative Study on the Calculations of Punching and Shearing of Independent Foundation Based on Chinese American European and Japanese codes

为研究中国、美国、欧洲、日本规范对柱下独立基础冲剪验算的异同,从验算条件、控制截面位置、承载力公式以及冲切锥底面的形状等方面进行了对比分析。并选取了8个轴心受压独立基础试验,将各国规范计算得到的轴力设计值与试验值进行对比,结果表明:我国规范的计算破坏模式与试验吻合最好;当基础配筋率小于1.65%时,ACI318-19的计算结果较ACI318-11更小;当配筋率较大时,各国设计结果更加保守,说明美、欧、日规范虽考虑了配筋率的影响,但考虑得不够充分;对于同一基础,按不同规范计算得到的破坏模式不尽相同。最后,鉴于各国规范均未充分考虑纵筋的有利作用,在已有试验的基础上采用MSC.Marc有限元软件对纵筋配筋率对基础冲、剪承载力的影响进行了参数分析,结果表明当配筋率不大于0.6%时,配筋率每增加0.2%剪切承载力提高0.334倍、冲切承载力提高0.4倍。

In order to study on the differences of punching and shearing calculations of independent foundation based on Chinese,American,European and Japanese codes,the comparative study was made in terms of the checking conditions,the control section position,the bearing capacity formula and the shape of the bottom surface of the punching cone.Eight independent foundation tests of axial compression were selected,and the design value of axial force calculated by every code was compared with the test value,the results show that the calculation failure mode is the best agreement with the test based on Chinese code;When the reinforcement ratio is less than 1.65%,the results of ACI 318-19 are smaller than those of ACI318-11;When the reinforcement ratio is greater,the design results of each code are more conservative,which show that the American,European and Japanese codes have considered the influence of reinforcement ratio,but not enough;For the same foundation,the failure modes calculated according to different codes are not the same.Finally,in view of the fact these codes do not fully consider the beneficial influence of longitudinal reinforcement,based on the existing tests,the influence of reinforcement ratio on the punching and shearing capacity of foundations were analyzed by MSC.Marc software.The results show that when the reinforcement ratio is not greater than 0.6%,the shear capacity increased by 0.334 times and the punching capacity increased by 0.4 times for every 0.2%increase in reinforcement ratio.