波形钢腹板PC组合箱梁纯扭全过程分析模型

为准确预测波形钢腹板PC组合箱梁（PCCBGCSWs）在纯扭作用下的全过程受力行为，基于软化薄膜元理论提出了改进软化薄膜元模型（ISMMT）. 首先，对ISMMT的平衡、变形协调和材料本构方程以及通用求解程序进行了简要介绍；在此基础上，提出了当波形钢腹板、预应力及普通钢筋均处于弹性阶段时的简化求解程序框图，该简化程序仅有一层迭代循环；最后，完成了一根PCCBGCSWs试件的纯扭模型试验，通过试验得到了试件的扭矩-扭率曲线、波形钢腹板和混凝土翼缘板剪应变、预应力和普通钢筋应变等结果，将试验结果与ISMMT预测的理论结果进行了对比，同时将简化求解程序和通用求解程序的求解效率进行了比较. 结果表明: ISMMT不仅能准确预测PCCBGCSWs在纯扭作用下的全过程扭矩-扭率曲线，还能模拟各构件的应变发展历程，包括混凝土翼缘板、波形钢腹板、预应力和普通钢筋等；运用ISMMT预测本文模型梁的纯扭全过程受力行为时，若采用通用求解程序进行计算，所需的总迭代次数可高达7.9 × 106次，采用简化求解程序最少为5次，最多也仅为193次，可极大提高求解效率；本文ISMMT为PCCBGCSWs的纯扭全过程分析提供了一种有效途径. 

Full-Range Analytical Model for Prestressed Concrete Composite Box Girders with Corrugated Steel Webs Under Pure Torsion

To accurately predict the full-range mechanical behavior of prestressed concrete composite box girders with corrugated steel webs (PCCBGCSWs) subjected to pure torsion, a theoretical model called “the improved softened membrane model for torsion (ISMMT)” was proposed based on the softened membrane theory. First, the equilibrium equations, compatibility equations, constitutive laws of materials and general solution algorithm of the ISMMT were briefly introduced. On this basis, a simplified solution algorithm was additionally presented for the stage when both steel bars, the prestressing steel and the corrugated steel webs (CSWs) are in the elastic state, which contains only one iteration loop. To validate the feasibility and accuracy of the ISMMT, a PCCBGCSW specimen was tested under pure torsion. The results, including the overall torque-twist curve, shear strains in the CSWs and concrete flanges, and strains in the prestressing steels and steel bars, were obtained from the test. Then, the experimental results were compared with the theoretical results calculated by the ISMMT. The comparison of solving efficiency between the general computer program and the simplified one was also conducted. Results show that the ISMMT not only can provide accurate prediction for the full-range torque-twist curve of PCCBGCSWs under pure torsion, but also can make precise predictions for the entire stress evolution in components of the PCCBGCSWs during loading, including the concrete flanges, CSWs, prestressing steels, and steel bars. When using the ISMMT to predict the full-range behavior of the PCCBGCSW specimen under pure torsion in this study, the number of iterations could be as high as 7.9 × 106 if the general computer program was used. However, if the simplified computer program was employed, the number of iterations could be significantly reduced (5 times at least and 193 times at most), which is a great improvement in solving efficiency in comparison with the general computer program. Therefore, the ISMMT provides an effective way to analyse the full torsional behaviour of PCCBGCSWs under pure torsion.