预应力超高性能混凝土工字形梁抗剪性能试验

为了研究预应力超高性能混凝土(UHPC)工字形梁的抗剪性能和抗剪承载力计算方法,本文设计并完成了3片预应力UHPC工字形梁的单点加载试验,获得了试验梁的荷载-位移曲线、破坏模式和裂缝分布特征等关键结果；基于试验结果、瑞士和法国UHPC规范、我国公路桥梁规范及公路桥涵超高性能混凝土应用规范意见稿计算了试验梁的抗剪承载力,分析了各个规范的适用性。此外,基于修正压力场理论(MCFT),分别采用Mohr-Coulomb准则和Rankine准则的计算了试验梁的抗剪承载力,并进行了分析讨论。研究表明：预应力UHPC工字梁的抗剪承载力随着剪跨比的增加而减小,箍筋对于抗剪承载力影响较大；各国规范对UHPC梁的抗剪承载能力的计算较为保守。采用Mohr-Coulomb准则的计算结果较Rankine准则的计算结果与试验值更为接近；特别是小剪跨比的试验梁,处于弯剪复合状态,Mohr-Coulomb准则考虑了受压区UHPC法向和切向应力的影响,更为接近实际状况。

Experimental on shear behavior of prestressed UHPC I-shaped beams

To investigate the shear performance and the calculation methods for shear capacity of prestressed ultra-high performance concrete (UHPC) I-shaped beams, a total of three prestressed UHPC I-shaped UHPC beam specimens were designed and tested under one-point loading. Critical experimental results including the load-deflection relationship curves, failure modes, and crack patterns were obtained. Based on the test results, French UHPC code, Swiss UHPC code, Chinese codes, and Chinese UHPC code, the shear capacity of the test specimens were calculated and their feasibility were discussed. Additionally, the modified compression filed theory (MCFT) was adopted to calculate the shear capacity of the test beams based on Mohr-Coulomb and Rankine criterions. It was found that the shear capacity of UHPC beams decreases with the shear span-to-depth increases and the stirrups have a great impact on the shear capacity. The results show that the calculation of various specifications is relatively conservative. The calculation results of the Mohr-Coulomb criterion are closer to the experimental values than those of the Rankine criterion. Because the test beam with a small shear-span ratio is in a bending and shearing state, the Mohr-Coulomb criterion can consider the influence of normal and tangential stresses on the compression zone, where the simulation results are closer to the actual condition.