矩形钢管混凝土受弯构件材料本构关系与失效判据研究

为了正确评估矩形钢管混凝土(CFST)受弯构件的承载力，提出钢管和核心混凝土材料本构关系的修正模型，建立CFST受弯构件的承载力失效判据。首先，考虑受拉区钢管双轴受拉有利应力状态及受压区钢管双轴拉压不利应力状态，并基于矩形CFST轴压短柱试验数据库，通过回归分析建立约束混凝土峰值应力表达式，在此基础上建立矩形钢管混凝土材料本构关系的修正模型。其次，基于构件承载能力极限状态，并合理考虑受拉区钢管的应变强化段，提出矩形CFST受弯构件的承载力失效判据。最后依据纤维模型法和试验数据库对比分析CFST受弯构件的不同材料本构关系和失效判据的精度及适用性。结果表明，所建立的CFST构件材料本构关系和承载力失效判据能够更加准确地反映矩形CFST构件的抗弯能力，具有更高的计算精度和广泛的适用性。

Constitutive relations and failure criterion for rectangular concrete-filled steel tube members under pure bending

In order to evaluate the ultimate bearing capacity of rectangular concrete-filled steel tube (CFST) members under pure bending, the modified constitutive relations were proposed for steel tube and core concrete, and the bearing capacity failure criterion was developed. Firstly, by taking into account the favorable biaxial tensile state of the steel tube in tension zone and the unfavorable biaxial compressive-tensile state of the steel tube in compression zone, the modified constitutive relations were developed for steel tube. Then, the test database of short rectangular CFST members under axial compression was adopted to obtain the peak stress expression by means of regression analysis, and the modified constitutive relation of core concrete was presented. Moreover, taking into consideration the strain hardening of steel in tension zone, the bearing capacity failure criterion was defined based on the limit state of ultimate loading capacity. Finally, the accuracy and applicability of different constitutive relations and failure criterions were verified by means of the test database and the fiber model method. Results show that the proposed constitutive relations and failure criterion can lead to higher accuracy with wide range of application for the bending capacity of rectangular CFST members under pure bending.