纤维预拉杆式自定心屈曲约束支撑的力学性能与设计方法研究

The buckling-restrained brace (BRB) based on disaster-reduction and energy-dissipation concept is an effective measure to reduce structural seismic damage. For the relatively low post-yield stiffness of the brace, BRB structures are prone to large residual lateral deformations, leading to the increasing difficulty and cost for structural renovation after earthquake. Therefore, the self-centering system with pretensioned fiber-reinforced-plastic bars (FRP-SC) is introduced to solve this problem. Through the incorporation of theoretical method, numerical simulation and performance experiment, the mechanic performance and design method of FRP-SC-BRB are investigated from three levels: construction, member, and structure. In the construction level, the mechanic performance and anchorage method of appropriate FRP bar for self-centering system is determined through experiments, the working mechanism of FRP-SC-BRB is studied, and the construction design principle is established for brace system. In the member level, through quasi-static loading experiments and numerical simulations, the influence of key construction parameters on the hysteretic performance of FRP-SC-BRB is investigated, and the mechanic model reflecting the energy-dissipation and self-centering characteristics of brace systems is constructed. In the structure level, through the nonlinear dynamic analysis and shaking-table experiment, the influence of key hysteretic parameters of brace system on the structural seismic performance is investigated, and the direct design method for FRP-SC-BRB structures considering the performance constraint of residual deformations as well as maximum displacements is presented.

基于分灾-耗能理念的屈曲约束支撑(BRB)是减轻结构震害的有效手段。但由于支撑屈服后刚度较低，使得BRB结构在强震后易于产生较大残余变形，增加了结构震后修复的难度和成本。为此，提出在BRB中引入纤维预拉杆式自定心体系(FRP-SC)以解决这一问题。拟通过理论方法-数值模拟-性能试验相结合，从构造、构件和结构层次开展FRP-SC-BRB的力学性能与设计方法研究。构造层次：通过试验研究确定适用于自定心体系的纤维筋材力学性能与锚固系统，解明FRP-SC的工作机制，建立支撑体系的构造设计原则；构件层次：通过拟静力试验与数值模拟，研究关键构造参数对FRP-SC-BRB滞回性能的影响规律，构建反映支撑滞回耗能与自定心特征的力学模型；结构层次：通过FRP-SC-BRB减震结构的非线性动力分析与振动台试验，研究支撑滞回性能参数对结构抗震性能的影响规律，提出同时考虑结构位移与残余变形性能约束的直接设计方法。

针对传统屈曲约束支撑(BRB)结构由于屈服后刚度较低易于在在强震后产生较大残余变形的瓶颈问题，本项目提出一种纤维预拉杆式自定心体系，并将其引入至BRB，形成纤维预拉杆式自定心屈曲约束支撑(FRP-SC-BRB)，从构造、构件和结构三个层次开展FRP-SC-BRB的力学性能与设计方法研究。本课题重点完成了以下工作：(1) SC-BRB构件的构造设计与性能试验。开展了6根BFRP预拉杆及其锚固系统的循环加载试验，测定了BFRP预拉杆的循环弹性模量、极限强度和极限弹性延伸率等关键力学性能指标及其锚固性能，设计并完成了4根SC-BRB构件的拟静力试验，研究了SC-BRB的滞回耗能、自定心机制、残余变形、极限荷载、破坏形态等关键性能，提出了减小加工误差对构件第一刚度影响的端部构造措施，建立了兼具良好耗能能力与自恢复能力的SC-BRB支撑构造系统；(2) SC-BRB构件滞回性能的力学模型和非线性有限元参数化分析。基于流变分析理论和预拉杆的材料特性，建立可系统研究SC-BRB滞回性能的精细流变力学模型和分析方法，并与不同预拉杆材料的SC-BRB试验结果进行对比验证；采用ABAQUS有限元分析软件，建立了考虑构件多重非线性因素的SC-BRB精细有限元模型，研究了耗能系统和自定心系统的关键构造参数对SC-BRB滞回性能的影响规律；(3) SC-BRB框架结构的抗震性能参数化分析。建立了可用于整体结构分析的等效杆系模型，研究了套管长度误差对结构抗震性能的影响机理，引入了防止预拉杆断裂导致框架结构破坏甚至倒塌的摩擦保护装置，系统分析了地震作用折减系数、支撑强度比、刚度比、摩擦启动位移角等关键设计参数对SC-BRB框架结构最大层间位移角、残余位移角、最大加速度、结构损伤集中系数等关键指标的影响规律，确定了关键设计参数的合理取值范围；(4) SC-BRB框架直接基于位移的设计方法。基于参数化抗震性能分析结果建立了残余位移角与最大位移角的统计关系，推导了SC-BRB框架等效阻尼比与关键结构参数的关系公式，采用直接基于位移的设计方法(DDBD)理念，针对SC-BRB框架的特点，建立了基于最大位移角和残余位移角双重控制目标的直接设计方法和流程，实现了对结构损伤和可修复性的控制，可为SC-BRB结构的推广应用提供理论方法和技术支撑。