钢管超高性能混凝土柱耐火性能数值模拟与理论分析

Numerical Simulation and Theoretical Analysis on the Fire Resistance of Ultra-high-performance Concrete Filled Steel Tubular Columns

为研究钢管超高性能混凝土在标准火灾下的受力性能和破坏机理,建立了钢管超高性能混凝土柱的耐火有限元模型,并重点对比分析了超高性能混凝土与部分其他类型混凝土的热工参数及高温下本构关系的不同对构件温度和耐火极限等的影响,结果表明:钢管超高性能混凝土构件的核心混凝土温度明显高于相应的普通钢管混凝土或钢管高强混凝土构件的核心混凝土温度,且对于不同配合比的超高性能混凝土构件,其核心混凝土温度场也存在一定差异;高温下钢管对核心超高性能混凝土的约束作用可以忽略不计;对于不同长细比的构件,超高性能混凝土热工参数的取值对构件耐火极限的影响程度几乎不变,但不同荷载比下会有所变化,且荷载比是影响钢管超高性能混凝土耐火极限的主要影响因素。在上述工作的基础上,基于平均温度的耐火计算方法,给出了超高性能混凝土等效强度和等效弹性模量折减系数的计算方法以及考虑不同超高性能混凝土热工参数取值的钢管超高性能混凝土柱平均温度和耐火承载力计算公式,并验证了公式的合理性。该研究将为钢管超高性能混凝土的防火设计提供参考。

In order to investigate the mechanical behavior and failure mechanism of ultra-high-performance concrete filled steel tube(UHPC-FST)exposed to standard fire,a finite element model for fire resistance calculation of UHPC-FST was built.The effects of different thermal properties and constitutive relation at high temperature between UHPC and other types of concrete on the temperature and fire resistance of members were analyzed.The results show that the temperature in core concrete of UHPC-FST is higher than that in CFST or HS-CFST and the temperature field of core concrete of UHPC-FST with different mix proportions is also different.The confinement effect of steel tube on core UHPC can be ignored at high temperature.The value of thermal properties of UHPC will have an impact on the fire resistance of UHPC-FST with different slenderness ratio,but the degree of the impact can vary under different load ratio,and the load ratio is a key influencing factor.According to the unified method for calculating fire resistance of CFST based on average temperature,the formulas for the equivalent strength and elastic modulus reduction coefficient of the UHPC are given.The formulas of average temperature of steel tube and UHPC and axial bearing capacity for UHPC-FST columns at high temperature with different thermal properties of UHPC are deduced and verified.This paper can provide a reference for the fire resistance design of UHPC-FST.