基于修正压力场理论的超高性能混凝土梁抗剪承载力计算方法

ANALYSIS OF SHEAR CAPACITY OF UHPC GIRDERS BASED ON THE MCFT THEORY

为研究超高性能混凝土梁的抗剪性能,基于修正压力场理论(MCFT),叠加弯矩效应并对该部分的超高性能混凝土(UHPC)的本构关系进行修正,同时考虑了UHPC开裂后的抗拉强度对抗剪的贡献,建立了预应力UHPC梁在弯剪复合作用下的截面分析模型并编制了计算程序。为验证该模型的正确性,以剪跨比为主要因素,设计3片预应力UHPC梁的抗剪试验,获得了梁的破坏形态、裂缝分布特征及承载能力大小等试验结果;并结合其他文献试验结果用此模型进行对比,结果吻合较好,且变异系数小。结合MCFT模型和大量已有文献的试验结果,综合考虑了剪跨比、配箍率、预应力以及UHPC强度等因素的影响提出了UHPC梁的抗剪计算式,计算值与试验值吻合良好。

In order to study the shear behavior of ultra-high performance concrete beams,based on the MCFT theory,the bending moment effect was superimposed and the UHPC(ultra-high performance concrete)constitutive relation of this part was modified.The contribution of tensile strength of UHPC to its shear performance after cracking was considered.The cross-section analysis model of prestressed UHPC beam under the conmbined action of bending and shearing was established,and the calculation program was compiled.In order to verify the correctness of the model,the shear test of three prestressed UHPC beams with the shear-span ratio as the main factor was conducted.The failure mode,crack distribution characteristics and bearing capacity of the beams were obtained.After using this model to validate the experiment results of other literatures,the results showed that the contrast results were in good agreement and the coefficient of variation was small.Combined with the MCFT model and the test results of a large number of existing literatures,the shearing empirical formula of UHPC beam was proposed considering the influence of shear-span ratio,hooping ratio,prestress and UHPC strength.The calculated value well coincided with the test.