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为研究钢构件的火灾性能及火灾条件对结构可靠性的影响,采用非线性有限元法,基于蒙特卡洛原理建立了约束钢梁的可靠性模型;采用参数化方法研究自然火灾模型的随机变量以及防火保护层厚度对钢构件可靠性及灵敏度的影响.结果表明：火灾随机变量对钢梁可靠性的灵敏度不同,火灾最高温度Tm影响最大,形状参数sc影响最小;可靠性随最高温度Tm和形状参数sc的增大而降低,随达到最高温度所需时间tm的增大而增高;随火灾随机变量标准差的增大而降低.在一定范围内,适当增加防火保护层厚度可明显降低构件的失效概率.因此降低火灾最高温度、延长达到最高温度所用时间,减小形状参数,可以增加结构的耐火时间,提高结构的可靠度.应根据工程要求,确定最佳防火保护层厚度.所采用的模型为定量分析钢构件在随机火灾下的可靠性以及评估构件在火灾中的失效风险提供了研究基础.“,”In order to study fire behaviors of steel member and the effect of fire conditions on its reliability,the reliability model of restrained steel beam is established by nonlinear finite element method based on Monte Carlo principle.The effect of stochastic variables in natural fire model and thickness of fire retarding coating on the reliability and sensitivity is discussed by parametric method.The results show that the fire stochastic variables have different effects on sensitivity of beam reliability.The impact of maximum temperature Tm is the most obvious,that of shape constant sc is minimal.With increasing Tm and sc,or decreasing the time tm at which Tm occurs,and increasing the variance of stochastic variables,the reliability of steel beam will descend.The failure probability of steel beam is obviously decreased with increasing thickness of fire retarding coating to a certain range.So when maximum temperature and shape constant are decreased;and the time at which maximum temperature occurs is increased,the fire-resistant duration of the beam will be prolonged,which is benefit to improve the fire reliability.The optimum thickness of fire retarding coating should be confirmed by the engineering requirements.The model proposed provides a research basis for quantitative analysis of reliability in stochastic fire and evaluating fire risk.