自复位消能钢桁梁受力机理及其在山地掉层结构抗震设计中的应用研究

It’s one of hot research topics in field of seismic design and analysis for modifying self-centering technology to reduce building residual drift, improve replaceable and repair function after severe earthquake. Due to vertical and torsional irregularity of structure in slope area, it’s also difficult to deal with design problem for upper foundations effectively using conventional design methodology. Thus it’s very important and necessary to design the buildings in slope area using self-centering technique so as to reduce their residual drift, improve replaceable and repair function as well as seismic performance of the structures. With combination of theoretical, experimental and simulation methodology, the self-centering steel truss beams and structures in slope area will be studied from component level to structural level. The mechanical properties of steel truss beam by combination of basic elements, self-centering and energy dissipation component will be discussed, the evolution trends of strength and stiffness under long-term loading will also be analyzed. Compared with cyclic test results, the optimal configure of self-centering truss beams will be determined based on its seismic performance under different earthquakes. Then the self-centering truss beam will be applied to steel moment resisting frames constructing in slope area and its self-centering function, energy dissipation capacity and failure mechanism would be discussed. Finally，the multi-scale analytical model and design strategy of spatial structures in slope area will be obtained to guide forming technical specification of seismic design for the structures in slope area.

自复位抗震技术可有效减轻结构震后残余变形和提高构件的可更换性，对其不断完善和改进，是当前抗震研究热点之一；而山地掉层结构本身有竖向和横坡向的扭转不规则等特性，致使按常规抗震设计思路难以有效地处理上接地楼层部分的受力难题。将新型自复位消能钢桁梁应用于掉层结构，对丰富结构体系和改善结构抗震性能具有重要的理论研究意义。本项目拟采用理论分析、试验和数值模拟相结合的方法，从构件到结构分层次展开研究：研究钢桁架梁中基本杆件、自复位元件和耗能元件对梁抗震性能的耦合受力机制，分析桁架梁在荷载长期效应下的强度和刚度演变机理，结合构件拟静力试验，确定自复位钢桁架梁元件基于构件性能设计的最优匹配关系；并将自复位梁应用于掉层框架中，研究自复位梁的布置方式和上接地柱的不同约束条件等对框架自复位、耗能特性和破坏机制等影响规律；提出空间掉层结构的多尺度分析模型和抗震设计方法，为山地结构的抗震设计规程的编制提供理论依据。

本项目围绕自复位消能钢桁架（工字钢）梁的受力特性及结构抗震设计方法完成了以下研究工作：.1）自复位消能钢桁架梁构件的受力机理。在借鉴自复位消能钢桁架梁试验和理论分析的基础上，将钢桁架梁改进为工字钢梁，从而研制了新型的自复位消能工字钢梁。进行了6组足尺钢梁构件的低周往复抗震试验（根据钢梁设置于中间楼层或顶层分为两类），研究其受力机理和不同参数的阻尼器对构件抗震性能变化规律，试验结果验证了该类构件良好的承载能力和变形能力、其塑性变形和损伤都集中于耗能元件，更换耗能元件后，其抗震性能得以迅速恢复。建立了构件有限元分析模型，研究了构件参数（工字钢梁截面、预应力索的面积和初始应力、消能阻尼器屈服强度和截面面积等）对构件抗震性能、自复位及残余变形的影响规律。.2）自复位平面钢框架结构抗震性能。钢框架由自复位消能工字钢梁和普通型钢柱（柱脚铰接和刚接两类）组成，进行了2榀足尺平面框架的低周往复荷载试验，对比分析了结构的受力过程、耗能能力和卸载后的自复位能力。结果表明结构具有良好的耗能能力。框架的抗震性能主要由自复位SC参数确定，对于柱脚固接的自复位钢框架，其抗侧能力相对较高，但残余变形较大，结构自复位效果较差；而柱脚铰接的自复位钢框架，卸载后残余变形较小，具有良好的自复位和功能可恢复性。.3）自复位钢梁截面及平面钢框架结构的可靠度分析。利用JC法对自复位钢梁梁端截面承载能力的可靠度进行了分析，考虑了在长期荷载效应下预应力索的松弛、消能元件的衰变及更换等因素引起的构件强度受力的时变影响，结果表明自复位钢梁端截面能够可靠地承担地震作用产生的梁端弯矩，满足现行《建筑结构可靠度统一标准》的相关要求；同时表明自复位钢梁两端截面抗弯可靠度在设计周期内略有降低但在可接受的范围内；采用了蒙特卡洛有限元分析法对自复位平面框架结构的可靠度进行了探索。