基于振动测试的混凝土连续梁火灾损伤识别方法研究

Engineering structures exposed to intense heat will be destroyed seriously, even collapse, which causes enormous life and property loss. This project chose two-span concrete continuous beams heated on their three surfaces as breakthrough point. Finite element model updating, the modal parameter change rule, fire damage identification and assessment system will be studied with the method of theoretical analysis, numerical simulation, fire experiment and dynamic testing. The main research contents are as follows: (1) A finite element model updating method will be proposed based on incomplete modal and boundary conditions as a key consideration; (2) The dynamic test of concrete continuous beams burned on their three surfaces will be carried out, and then the change rule of natural frequency and vibration mode over time will be summarized; (3) A nonlinear model of relationship between modal parameters and stiffness deduction coefficients will be established based on modified finite element model. And then, a fire damage identification method and an assessment method of post-disaster residual mechanical properties taking the stiffness reduction coefficient as the index will be established. The assessment results consist with that of “Standard for building structural assessment after fire”. This project will improve the fire detection theory and method of concrete beams, provide sufficient theoretical support for residual mechanical performance assessment after fire and offer the important reference for bearing capacity evaluation of other type concrete members.

高温下建筑结构损坏甚至倒塌是造成人员伤亡及经济损失的主要因素。本项目拟以两跨混凝土连续梁为切入点，通过理论分析、数值模拟、火灾试验及现场动力实测相结合的方式对有限元模型修正技术、模态参数变化规律、灾后损伤识别及评估方法进行系统研究。具体内容包括三个方面：(1) 提出基于不完备模态并重点考虑边界条件影响的有限元模型修正方法；(2) 进行混凝土连续梁在三面受火下的动力性能测试，研究结构自振频率、振型与受火时间的变化规律；(3) 以修正后的有限元模型为基准，建立模态参数与刚度折减系数之间的非线性模型，提出火灾后损伤识别方法及以刚度折减系数为指标的灾后残余力学性能评估方法，且评估结果与现行规范《火灾后建筑结构鉴定标准》中的有关规定相衔接。本项目将完善混凝土梁的抗火检测理论与方法，为其在火灾后残余力学性能评估提供充分的试验与理论支持，为其他类型混凝土构件的灾后承载力评估提供重要参考。

高温下建筑结构损坏甚至倒塌是造成人员伤亡及经济损失的主要因素。本项目拟以混凝土梁为切入点，通过理论分析、数值模拟、火灾试验及现场动力实测相结合的方式对有限元模型修正技术、模态参数变化规律、灾后损伤识别及评估方法进行系统研究。提出了基于不完备模态并重点考虑边界条件影响的有限元模型修正方法，建立了可用于损伤识别及评估的可靠模型；进行了混凝土简支梁在三面受火下的动力性能测试，研究结构频率、振型等与受火时间的变化规律；以修正后的有限元模型为基准，建立模态参数与等效爆火时间之间的非线性模型，提出火灾后损伤识别及评估方法，且评估结果与现行规范《火灾后建筑结构鉴定标准》(CECS 252-2009)中的有关规定相衔接，弥补了其主观性较强，误差较大的缺点，可作为CECS 252-2009的有效补充。本项目将完善混凝土梁的抗火检测理论与方法，为其在火灾后残余力学性能评估提供充分的试验与理论支持，为其他类型混凝土构件的灾后承载力评估提供重要参考。