考虑剪力滞和剪切变形效应的UHPC箱梁长期挠度分析

Analysis of Long-term Deflection of UHPC Box Girders Considering Shear-lag and Shear Deformation Effect

为准确计算UHPC箱梁在长期荷载作用下的挠度,基于剪切变形规律的截面翘曲位移函数,运用能量变分法建立考虑剪力滞、剪切变形效应以及UHPC收缩徐变效应的UHPC箱梁挠度计算控制微分方程,推导均布荷载和集中荷载作用下UHPC简支箱梁挠度计算公式,并利用有限元模型计算结果对其正确性进行验证。通过数值算例分析不同效应、截面配筋以及材料特性对UHPC箱梁挠度计算的影响。结果表明:考虑剪切变形效应产生的挠度明显大于剪力滞效应;均布荷载和集中荷载作用下,仅考虑剪力滞和剪切效应后产生的简支梁跨中挠度相对于按初等梁理论计算的瞬时挠度分别增大了9.4%和10.9%,而同时考虑UHPC收缩徐变效应后分别增大了约1.5倍左右;截面配筋对箱梁挠度计算有一定的影响,两种荷载作用下,考虑配筋后计算得到的简支梁跨中瞬时和长期挠度分别是不考虑配筋时挠度的0.96倍和0.89倍;用UHPC材料代替普通混凝土材料可显著降低结构的短、长期挠度以及收缩徐变引起的挠度变化。提出的公式可为长期荷载作用下UHPC箱梁的挠度计算提供理论依据。

To accurately calculate the deflection of ultra-high performance concrete(UHPC)box girder under long-term load,a controlled differential equation for deflection calculation of UHPC box girder considering shear lag,shear deformation effect and UHPC shrinkage creep effect was established by using energy variational method based on the cross-sectional warpage displacement function considering shear deformation law.Then,the formulae for calculating the deflection of UHPC simply-supported box girders under uniform and concentrated loads were derived,and their correctness was verified by using the calculation results of finite element model.In addition,numerical examples were used to analyze the influence of different effects,cross-sectional reinforcement and material properties on the deflection calculation of UHPC box girders.The results show that the deflection considering the shear deformation effect is significantly greater than that of the shear lag effect.Under uniform and concentrated loads,the mid-span deflection of a simply supported girder considering only shear lag and shear effect increases by 9.4%and 10.9%when compared with the results of elementary beam theory respectively,and increases by about 1.5 times after considering the shrinkage and creep effect of UHPC respectively.The cross-sectional reinforcement has a certain impact on the calculation of box girder deflections.The instantaneous and long-term deflections calculated considering reinforcement are 0.96 and 0.89 times those calculated without considering reinforcement under uniform and concentrated loads.Replacing the normal concrete with UHPC can significantly reduce the instantaneous and long-term deflections of the structure and the change of deflection caused by shrinkage and creeps.The suggested formula can provide a theoretical basis for the deflection calculation of UHPC box girder under long-term load.