考虑钢管初应力影响的钢管混凝土柱抗火性能研究

由于钢管混凝土结构特殊的施工模式以及管内混凝土的收缩徐变，使得实际结构中钢管和混凝土的应力状态和常规成型后再受力的情况存在显著差异，这种差异在很大程度上可简化为钢管初应力问题。同时根据结构全寿命周期设计的发展要求，考虑施工过程和结构老化影响的抗火设计将很有必要。因此，本项目将采用试验研究、数值计算和理论分析相结合的方法对具有初应力的钢管混凝土柱抗火性能展开系统地研究，研究内容包括：1）进行具有初应力的钢管混凝土柱耐火极限试验研究；2）建立可考虑初应力的钢管混凝土抗火分析的数值模型，研究初应力对构件抗火性能的影响机理和规律；3）建立具有初应力的钢管混凝土抗火计算简化理论模型，并基于试验和数值结果，最终给出考虑初应力的抗火承载力工程计算方法。通过本项目的研究将解决现有防火设计方法尚未考虑而又亟待解决的初应力问题，对钢管混凝土结构全寿命周期设计和安全使用具有重要意义。

Within a cast-in-situ concrete-filled steel tube (CFST) structure, there exist initial stresses developed in the steel tube due to the construction process and shrinkage/creep of concrete. However, the current design method of CFST under fire has not considered the impact of initial stresses on the fire resistance of the composite members. This project will systematically study the influence of initial stresses on the fire resistance performance of CFST columns by undertaking the following tasks: 1) Test the fire resistance of CFST columns with initial stresses; 2) Establish a numerical model to study the mechanism of how initial stresses influence fire resistance performance of CFST columns; and 3) Propose a theoretical model for studying CFST columns under fire, and develop a method to predict the fire resistant capacity of the initially stressed columns on the basis of experimental and numerical analyses. It is expected that this existing and urgent problem, not yet covered in any current design codes, will be solved in this project, the outcomes of which will make significant contributions to the life cycle design and safe application of CFST columns in the construction industry.