大跨钢桥疲劳试验模型整体设计及控制方法研究

Holistic design and control of fatigue experiments for long-span steel bridges

为设计合理、可行和低成本的大跨钢桥疲劳细节试验模型,在总结众多疲劳试验模型设计和试验控制基础上,提出以模型设计为目标,综合考虑边界条件、加载和测试方案的整体设计和控制方法。首先模型设计应基于应力等效,并宜采用足尺模型,试件数量宜按科学试验设计方法安排。模型主要受力效应和次要受力效应的分析和监测同等重要。其次,边界条件疲劳强度须满足模型设计要求,且试验中需分析理论计算模型和实际模型边界条件差异,并对边界条件进行监测。再次,加载方案应关注整个加载系统的静动力性能,避免失稳或共振;作动器宜在受压状态来施荷,多向多点加载对加载系统协调性要求较高。最后,测试设计中应按规范进行应力测量,还须监测应力随疲劳加载循环次数变化情况,以保证试验情况一致性;位移测量应关注试件整体和局部变形行为;裂纹尺寸测量需综合利用各种检测方法;粘贴质量良好的应变片疲劳性能可满足试验测量需要。

To design reasonable, practical and low-cost fatigue test models for long-span steel bridges, a holistic design and control method is presented, which is model-design-focused with considering boundary conditions, loadings and testing designs, based on a study on former fatigue experiments. Firstly, full-scale fatigue test models should meet an equivalent stress principle. The number of specimens should be determined with scientific test design methods. Analysis and monitoring should be done for both primary load-carrying effect and secondary load-carrying effect of the test model. Secondly, fatigue strengths of boundary conditions shall meet the demands of the model design. Difference in boundary conditions between the numerical and experimental models need to be monitored and adjusted during the tests. Thirdly, the static and dynamic performance of the overall loading system should be analyzed to avoid buckling failure and resonance of the test model. Actuator should load in a compressive loading state. Multi-point and multi-axis loading requires high coordination level of the loading system. In the end, a stress measurement should be conducted to related standards. The stress variation during the fatigue loading is to be recorded to confirm the consistency of fatigue test. Deformation measurements should include both global and local behavior of the specimen. Crack size measurements need combined detective methods. The fatigue performance of well-installed strain gauges can meet the design requirements of a fatigue test.