超高性能混凝土牛腿受剪性能试验与承载力模型研究

Experimental and theoretical model study on shear performance of ultra-high performance concrete corbels

通过对12个超高性能混凝土(UHPC)牛腿的静力加载试验,研究了剪跨比、钢纤维体积率以及箍筋配筋率等主要变化参数对牛腿受剪性能的影响。结果表明:相比于高性能混凝土中未加入钢纤维的牛腿,UHPC牛腿的开裂荷载显著提高,同时破坏模式也从剪切破坏转变为弯曲破坏;通过减小剪跨比和增加箍筋配筋率可以提高牛腿受剪承载力。收集了UHPC牛腿试验数据,对GB 50010—2010《混凝土结构设计规范》和JGJ/T 465—2019《钢纤维混凝土结构设计标准》和理论模型中牛腿受剪承载力计算公式的适用性进行评估,发现已有的计算模型偏于保守,导致对UHPC牛腿的承载力的预测结果偏低。在此基础上,提出了一种适用于UHPC牛腿受剪承载力的改进拉压杆模型,该模型计算结果与收集的试验结果比值的平均值为1.15,变异系数为0.07。改进模型的准确性和离散性优于已有的计算模型,可供UHPC牛腿设计参考。

Through static tests on 12 ultra-high performance concrete(UHPC)corbels,this study investigates the influence of key parameters,such as shear span-to-depth ratio,steel fiber volume ratio,and stirrup reinforcement ratio,on the shear behavior of corbels.The results indicate that,compared to high performance concrete corbels without steel fibers,UHPC corbels exhibit a significant increase in cracking load,accompanied by a transition in failure mode from shear failure to flexural failure.Reducing the shear span-to-depth ratio and increasing the stirrup reinforcement ratio enhance the shear carrying capacity of the corbels.Collected experimental data of UHPC corbels were used to evaluate the applicability of shear capacity calculation formulas for corbels in the specifications GB 50010—2010‘Code for design of concrete structures’and JGJ/T 465—2019‘Standard for design of steel fiber reinforced concrete structures’,as well as the theoretical models.It is observed that the existing models tend to be conservative,resulting in underestimated predictions of UHPC corbel capacity.Based on this assessment,an improved strut-and-tie model suitable for predicting the shear capacity of UHPC corbels was proposed.The model’s average ratio of computed results to the experimental results collected in this study is 1.15,with a coefficient of variation of 0.07.The improved model demonstrates better accuracy and consistency compared to existing computational models,serving as a reference for UHPC corbel design.