基于细观本构模型的UHPC梁受弯全过程分析

Flexural analysis of UHPC beams based on a mesoscale constitutive model

为预测超高性能混凝土(UHPC)残余抗拉强度,通过细观力学分析,研究了纤维对UHPC残余抗拉强度贡献机理,提出了考虑纤维埋深、分布和取向的UHPC细观本构模型。基于UHPC细观本构、受力平衡方程和变形协调条件,建立了UHPC梁受弯分析模型和受弯承载力理论计算方法。经与8个UHPC梁试件受弯试验结果对比发现,文中提出的模型可以较好地预测UHPC梁受弯全过程响应和受弯承载力。基于基准试验梁的不同作用机制受弯贡献比例分析发现,纵筋配筋率从0增至2.5%时,受拉区混凝土对受弯承载力贡献从89.6%降至2.4%;纤维率从0增至3%时,受拉区混凝土对受弯承载力贡献从0增至22.1%。计算结果表明,对于低配筋UHPC结构,混凝土抗拉贡献应予以考虑。

In order to predict the residual tensile strength of ultra-high performance concrete(UHPC),the resistance mechanism of fibers on the residual tensile strength was investigated by meso-mechanics analysis,and a mesoscale constitutive model which took into account the distribution,orientation and embedment length of fibers was proposed.Based on the proposed constitutive model,the flexural analysis model and theoretical flexural strength calculation method were established via force equilibrium and deformation compatibility equations.The proposed flexural model was verified by the result of 8 UHPC beams.It is found that the proposed model can accurately predict the structural response during the whole loading process and the flexural strength of the test beams.According to the analysis results of different mechanisms,the contribution of concrete in tension to the flexural strength decreases from 89.6%to 2.4%as the longitudinal reinforcement ratio increases from 0 to 2.5%.The flexural strength increases from 0 to 22.1%as the fiber volume fraction increases from 0 to 3%.The calculation result indicates that concrete tension should be considered for UHPC structures with low reinforcement ratios.