Analysis Based On Secondary Development Of Ansys Pc Box Girder Creep Effect

For prestressed concrete (PC) box girder, creep will cause stress redistribution between concrete and steel in section and increase the deflection of girder. Shear lag can not only cause uneven distribution of stress in section along the flanges, but also cause additional deflection of girder. At present, most of the PC box girders are designed and analyzed by finite element method (FEM) base on theory of beam system, thus shear lag effects can not be taken into account. For this reason, the secondary development of the FEM software ANSYS has been carried out so that the program can be used to analyze the time-dependent effects in PC box girder, which bears important meaning in practical engineering.Based of conclusion of methods illustrating the creep characteristics and approches to analyze shear lag, this paper performed to analyze the time-dependent effects in PC box girder in ANSYS by secondary development, considering the effect of creep, relaxation of prestressed steel, ratio of steel, stress loss due to friction and shear lag.Firstly, ANSYS user creep subroutine USERCR.F has been developed secondary with UPFs language and FORTRAN language by introducing the concrete creep equations in foreign and native design codes, which is the foundation of time-dependent analysis. Secondly, the stress losses by friction and reverse friction during tension and anchorage along with the relaxation in prestressed steel are taken into account, meaning the effect of all kinds of stress losses is considered in time-dependent analysis of PC box girder by ANSYS. Lastly, the calculation module of time-dependent analysis of PC box girder is developed secondary with UIDL language, which can be used for time-dependent analysis of PC box girder considering the effect of creep, stress losses, shear lag and ratio of steel, and the deflection of beam and stresses of concrete and steel at any location at anytime can be calculated.Time-dependent analysis for simply supported PC box girder and continuous PC box girder are achieved based on the developed ANSYS, and the comparison of results between ANSYS and FEM software with beam elements is completed which shows that the secondary developed ANSYS can be used to analyze the time-dependent effect in PC box girders which holds reasonable precision, meaning that the secondary developed ANSYS can be applied in practical engineering.