基于混凝土循环剥落的隧道火灾损伤数值模型研究

为研究混凝土高温剥落对隧道衬砌火灾损伤的影响，在现有隧道结构非线性瞬态热—力耦合有限元模型基础上，提出1种在火灾高温条件下混凝土发生剥落的循环算法，以模拟火灾下衬砌结构截面面积的损失，并引入混凝土临界剥落温度的概念，得出基于混凝土循环剥落的隧道衬砌火灾损伤数值模型建立流程。利用该模型对某隧道衬砌结构进行火灾损伤模拟，并与试验结果进行对比验证。结果表明:火灾下隧道混凝土衬砌结构内逐渐增大的热应力是导致普通混凝土高温剥落的主要原因；可将衬砌受火面是否达到临界剥落温度作为隧道发生高温剥落的充分条件进行火灾损伤分析；模型求解所得的数值模拟结果与现场火灾试验数据基本吻合，验证了其可行性；混凝土高温剥落与否对衬砌结构等效温度应力有较大影响，在隧道衬砌结构抗火性能分析过程中应尽量考虑混凝土高温剥落造成的影响。

Study on numerical model of tunnel fire damage based on concrete cyclic spalling

In order to study the influence of high-temperature concrete spalling on the fire damage of tunnel lining,a cyclic algorithm of concrete spalling under the high-temperature conditions of fire was proposed based on the existing non-linear transient thermo-mechanical coupled finite element model of tunnel structure to simulate the reduction of cross-sectional area of lining structure.Moreover,the concept about the critical spalling temperature of concrete was introduced,and the establishment process of the fire damage numerical model of tunnel lining based on the cyclic concrete spalling was given.The model was used to simulate the fire damage of a tunnel lining structure,and the comparison and verification was conducted with the testing data.The results showed that the gradually increasing thermal stress in the concrete lining structure of tunnel under fire was the main reason for the high-temperature spalling of normal concrete,and whether the temperature of the heated lining surface reached the critical spalling temperature could be taken as the sufficient condition for the high-temperature concrete spalling of tunnel to carry out the fire damage analysis.The results obtained from the numerical model were basically in agreement with the field fire testing data,which verified the feasibility of the proposed model.The high-temperature concrete spalling had great influence on the equivalent temperature stress of lining structure,therefore the influence of high-temperature concrete spalling should be considered as far as possible in the process of the fire resistance analysis of tunnel lining structure.