带部分约束和无焊核心的高性能屈曲约束支撑研究

The buckling restrained brace (BRB) is one of the effective means of energy dissipation to improve the seismic capacity of the structures. High-performance BRB demands high capacity of energy dissipation and yield strength, stable hysteretic behavior under large plastic deformation, similar characteristics under tension as well as under compression, and convenience in fabrication and installation. However, most of the existing BRBs were unable to fully meet the above performance requirements. The energy dissipation capacity of steel was not completely utilized, the restraint components were too heavy, and the manufacture technique of the BRBs required precise control of the gap. Based on the results of previous research funded by the NFSC, this project introduces the concept of partial constraints and welding-free core component into the detail of the BRB. Considering core component with H-shaped section, the conception of core with large radius of gyration is used to increase the geometric tolerances in fabrication of the BRB, leading to the simplification in manufacture. The concept of partial constraints, which employs the stiffness of fibers perpendicular to the loading direction to prevent the un-restrained core strips from large buckling deformation, is used to simplify the restraint detailing, resulting in reduction of the weight of the BRB, and leading to the facilitation in manufactory and installation. The concept of welding-free core component which eliminate welding residual stress effects and other imperfections to the core component, especially to the transition section of it, is supposed to prevent BRB steel from low-cycle fatigue failure when it experiences large plastic strain, thus to increase the energy dissipation capacity significantly. Among them, the concept of partial restraint has been preliminarily experimentally verified.

屈曲约束支撑（BRB）是消能减震、提高结构抗震能力的有效手段。高性能BRB要求其具有较高的耗能能力和屈服承载能力、在大变形下表现出稳定的滞回性能、拉压荷载特性相近，并易于加工和安装。但目前大多数BRB尚无法全面满足上述性能要求，主要表现为耗能能力未充分发挥、约束部件重量过大、制作需要精确控制间隙等方面。本项目在已结题基金项目的研究基础上，提出带部分约束和无焊核心的BRB概念。结合H型核心截面，通过采用大回转半径的核心部件截面，提高BRB制作时的尺寸容差，使其易于加工制作；采取对核心部件实现部分约束的措施，利用核心部件板块垂直于受力方向的刚度，防止未约束板带的大幅屈曲变形，实现简化BRB的约束构造、减轻BRB的重量、方便施工安装的目的；通过在BRB的核心部件特别是其过渡段采用无焊构造，防止残余应力等缺陷引发大应变下的低周疲劳破坏，从而大幅提高其耗能能力。其中，部分约束的概念已被试验初步验证。

根据各向异性板理论，推导了弹塑性部分约束板的屈曲临界计算公式，结合非线性有限元分析，提炼出影响部分约束板块屈曲形态的主要因素，并得到了防止其大幅值屈曲变形的临界刚度条件，采用试验研究验证了所提出的临界刚度条件的合理性。进而，开展了部分约束屈曲约束支撑的试验研究，研究表明，在反复循环下，部分约束BRB的核心部件更易出现面外屈曲变形，其低周疲劳能力低于相应的全面约束BRB，但在合理构造下仍可保证优良的耗能能力。基于试验研究，提出了保证部分约束BRB耗能性能和耗能能力的构造措施。.针对屈曲约束支撑核心部件上端部加劲肋和中间定位栓焊接引入残余应变导致屈曲约束支撑低周疲劳能力大幅降低的现象，提出了无焊核心BRB的概念，基于概念分析和数值模拟提出了相应的构造措施。针对一字型和十字型截面无焊核心BRB的试验研究表明，该措施有效地提高了屈曲约束支撑的低周疲劳能力，累积塑性变形能力接近材料本身的性能，实现了屈曲约束支撑的高耗能特性。.依据钢筋混凝土构件中钢筋的受力原理，提出了一种以钢筋为核心受力部件的屈曲约束支撑，通过分析钢筋混凝土构件与屈曲约束支撑的异同，简化了钢筋的受力环境，提出了粘结、约束、屈服诱导和压缩变形量留设等设计方法，从而明确了各部分构造原则。开展的试验研究表明，这种屈曲约束支撑具有可靠的锚固能力、优良的耗能能力和低廉的制作成本。.本项目的研究，通过部分约束的构造达到了屈曲约束支撑的轻量化，通过核心部件的无焊构造提升了屈曲约束支撑的耗能能力，提出以钢筋为核心受力部件的屈曲约束支撑降低了屈曲约束支撑的制作成本。基于本项目的研究成果，可以从不同的方面实现屈曲约束支撑的高性能化。