Analysis of Long-term Deflection of UHPC Box Girders Considering Shear-lag and Shear Deformation Effect
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 de-formation 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 deflec-tion 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 ana-lyze 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 ele-mentary 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 calculat-ed 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.
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维普
