车致火灾作用下预应力混凝土T梁易损性计算方法
Vulnerability calculation method of prestressed concrete T？？shaped girder exposed to vehicles？？related fires

为了对车致火灾下预应力混凝土T形截面梁桥进行抗火性能评估，利用响应面分析法建立响应面函数（RSM）来模拟结构的非线性有限元分析，用蒙特卡洛抽样（MCS）来模拟参数的随机性，然后建立了基于响应面函数以及蒙特卡洛模拟（RSM？？MCS）的车致火灾易损性分析方法。该方法中将桥梁构件的损伤等级划分为轻微损伤、中等损伤、严重损伤、完全损伤4个等级，用构件的剩余承载力定义其损伤度，并根据已有的试验和理论成果定义不同损伤状态的界定标准；研究火灾和结构自身参数的随机性问题，并基于中心复合试验设计对参数进行抽样，形成试验样本和检验样本，建立基于RSM？？MCS的易损性分析方法，并以此开展预应力混凝土T形截面梁的易损性分析。研究结果表明：基于构件剩余承载力的易损性指标满足了不同破坏模式的需求，其界定标准反映了不同构件的损伤状态；火焰温度、火灾燃烧时间及火焰距受火面的距离3个参数能够很好描述火灾对结构作用的随机性；中心复合试验设计显著减少了复杂的有限元计算；在充分考虑火灾和结构不确定因素的情况下，易损性曲线能较好地反映T形截面梁在不同温度及不同损伤状态下的失效概率；车致火灾作用下预应力混凝土T梁易损性计算方法研究可为其灾前风险评估及灾后性能评估提供依据。
To assess the fire？？resistance performance of prestressed concrete T？？shaped girders exposed to fires caused by vehicles, the response surface method (RSM) was used to establish the response surface function instead of finite element analysis. Furthermore, the randomness of parameters was simulated by the Monte Carlo sampling (MCS), and the vulnerability analysis method based on RSM？？MCS was established. In this method, the damage level of bridge members was divided into four types: slight damage, moderate damage, extensive damage, and complete damage. The residual loading capacity was defined as the degree of damage of bridge members, and the partitioned criterion of damage status was specified on the basis of existing experiments and theoretical considerations. The problem of randomness in the parameters of fire hazard and structures was examined, and the central composite design method was used to generate test samples and verification samples. After the vulnerability analysis method based on RSM？？MCS was established, the vulnerability analysis of prestressed concrete T？？shaped girder was performed. The results show that the vulnerability index based on the residual loading capacity of members can be applied to various failure modes. The partitioned criterion reflects the damage status of different bridge members. The randomness of fire hazard can be simulated by fire temperature, burning time, and distance between the fire and structures. The number of finite element calculations is significantly reduced because of the use of the central composite design method. Under consideration the uncertainties in the simulation of fire and structural response, the failure probability of different temperatures, and the different damage levels that can be estimated from the vulnerability curves. This study is very useful for risk assessment before fire hazards and provide reference of performance assessment after fire hazards