混凝土双参数断裂模型和尺寸效应模型R阻力曲线比较

对混凝土的两类基本断裂模型(双参数断裂模型和尺寸效应模型)求解得到的第Ⅰ类几何形式下的R阻力曲线进行了详细的分析比较.首先对有效裂纹长度和裂纹尖端张口位移进行了修正,在此基础上由双参数断裂模型和尺寸效应模型得到了R阻力曲线的解析表达式.通过两类R阻力曲线计算得到的荷载-位移曲线与试验结果的对比,发现尺寸效应模型得到的临界有效裂纹长度稍大于双参数断裂模型的结果,而根据双参数断裂模型R阻力曲线得到的最大荷载大于尺寸效应模型的结果,且当相对初始裂纹长度较大时,双参数断裂模型R阻力曲线得到的最大荷载远大于试验值.双参数断裂模型的R阻力曲线适合于初始裂纹长度相对试件高度较小的情况.

Comparison of R-curves for concrete's two parameter fracture model and size effect model

A detailed comparison of two R -curves for geometry type I is made between two basic concrete fracture models, i.e., two parameter fracture model (TPFM) and size effect model (SEM). After modifications to the effective crack length and crack tip opening displacement, expressions of R -curve are proposed from TPFM and SEM. Comparisons of the load-displacement curves from these two R -curves with experimental results reveal that critical effective crack length from SEM is a little larger than that from TPFM, while the maximum load from the TPFM-based R -curve is bigger than that from SEM. Especially for a specimen with a larger relative initial crack length, the maximum load from the TPFM-based R -curve is considerably larger than the experimental load. R -curve from TPFM is suitable for the situation when the initial crack length is small relative to the specimen height.