强震下螺栓球网格结构超低周疲劳性能与评定方法研究

The modernization of human life and the public buildings of spatial grid structures are inseparable. But according to the survey of earthquake damages and failure modes of their vibration test, spatial grid structures suffered from ultra low-cycle fatigue failure under strong earthquake, directly threatening the safety of tens of thousands of such buildings during earthquake. This project will take bolted jointing grid structures with the most serious earthquake damages in the past strong earthquakes as the research object, and experimentally and analytically investigate on the micro mechanical model of ultra low-cycle fatigue of their bolted node (including bearing node) , the mechanism of rod’s crack after multiply pulled and buckled, their life checking of ultra low-cycle fatigue, and its simulation technique with consideration of material cumulative plastic damage, strengthened effect, and Bauschinger effect and stiffness degradation by rod’s multi buckling. Then the above research results will be applied to the simulation and comparison analysis on two bolted jointing grid structures damaged in Lushan earthquake and other examples by fiber beam and multi size element modeling technique. Life checking method of their ultra low-cycle fatigue and the anti-collapsed performance assessment method under disaster earthquake will be preliminarily established for the realization of seismic performance design of the grid structures, and for building the base of the safety assessment of the large number of existing grid structures.

空间网格结构建筑已与人类现代化生产、生活密不可分。但据震害调查与地震模拟振动台破坏形态试验，空间网格结构存在强震下的超低周疲劳破坏隐患，直接威胁着强震时数以万计的该类建筑的安全性能。本项目将以震害最严重的螺栓球网格结构为对象，针对螺栓球网格结构节点（包括支座节点）强震下超低周疲劳破坏的微观力学模型、杆件拉裂与多次压曲后断裂机理、超低周疲劳寿命验算以及计及节点影响、材料塑性损伤累积、随动强化、Bauschinger效应和单元多次屈曲刚度退化的模拟技术等开展试验与模拟研究，随后将研究成果应用于螺栓球节点空间网格结构体系，通过纤维梁与其它高精度单元的多尺度精细化建模，开展芦山地震损坏的两个大跨网格结构及其它案例的模拟对比分析，建立螺栓球网格结构灾难地震下超低周疲劳验算及抗倒塌性能评定方法，为实现该类结构基于破坏形态的抗震性能化设计与大量既有网格结构的强震下安全性能评定奠定研究基础。

在强震下，螺栓球网架结构中杆件与节点经历了数次塑性应变的过程，其破坏形态具有超低周疲劳破坏的特征。因此为探究螺栓球网架结构在强震下的超低周疲劳性能，课题采用试验研究和模拟分析相结合的方法，从螺栓球网架结构的典型组合构件、常用支座节点以及整体网架结构的层面，系统进行了循环加载下的螺栓球节点超低周疲劳性能试验、循环加载支座节点超低周疲劳性能试验、两端带螺栓球节点的圆钢管试件超低周疲劳性能试验及螺栓球网架结构大位移往复加载试验；并采用SEM扫描电镜进一步研究了钢管、螺栓等关键部件的典型断面，从微观层面揭示了螺栓球结构在强震下的超低周断裂机理，并得到了计及节点影响、材料塑性损伤累积、随动强化、Bauschinger效应和多次屈曲刚度退化的典型杆件的骨架曲线，结果表明强震下螺栓球网格结构的超低周疲劳性能直接关系着结构的安全性能。. 本项目由节点至杆件、自支座到结构，积累了丰富的螺栓球网架超低周疲劳数据，为强震下螺栓球网架的疲劳验算和安全性能评定提供了有力的数据支持和技术保障，具有较大的工程实践意义和学术参考价值。