【作者】 陈泉；

【导师】 孟少平； 王春林；

【作者基本信息】 东南大学 ， 结构工程， 2016， 博士

【摘要】 屈曲约束支撑是一种金属屈服耗能装置,同时也是一种不发生整体屈曲的钢支撑抗侧力构件,由核心部件、约束部件、无粘结材料或间隙三部分组成。小震时,屈曲约束支撑保持弹性,为结构提供抗侧刚度;中震或大震时,屈曲约束支撑通过约束部件有效抑制核心部件的整体屈曲或大幅局部屈曲,从而充分利用金属屈服后的滞回性能耗散地震能量,减小结构响应,避免主体结构发生严重损伤。屈曲约束支撑根据外围约束部件的不同,可分为钢管混凝土屈曲约束支撑和全钢屈曲约束支撑。其中,全钢屈曲约束支撑加工制作方便,但其细部构造有待优化,经济有效的支撑截面形式仍需拓展,其在结构抗震加固中的应用仍可深入探究。针对上述问题,本文通过理论解析、试验研究和数值模拟等方法,分别从支撑共性构造、新型支撑约束机制及其在框架抗震能力加固中的应用等方面对全钢屈曲约束支撑及结构进行了系统研究。主要研究内容和结论如下:在第2章中,深入研究了屈曲约束支撑核心部件共性构造对低周疲劳性能的影响,为新型全钢屈曲约束支撑的研发提供了设计建议:通过试验评估了核心部件过渡段的截面过渡方式、弹性段和过渡段伸入约束部件长度等构造尺寸对一字形核心全钢屈曲约束支撑累积塑性变形和失效模式的影响;结合有限元分析,对比了核心部件不同构造所引起的应力应变集中现象,揭示了改进设计后试件低周疲劳性能提高的原因。结果表明,采用圆弧形过渡方式以及增加弹性段和过渡段伸入约束部件长度,可改善核心部件的应力应变集中现象,显著提高其低周疲劳性能。在第3章中,首次研究了无粘结材料对全钢屈曲约束支撑滞回性能的影响,为新型全钢屈曲约束支撑的设计提供了理论基础.:通过试验对比了采用和未采用无粘结材料的一字形核心全钢屈曲约束支撑的滞回曲线、失效模式和累积塑性变形能力;对核心部件的多波屈曲行为进行了理论推导,给出了支撑受压承载力调整系数的估算公式;通过有限元分析了核心板和约束部件之间接触力以及核心板沿纵向的应变集中现象;结合试验和有限元参数分析,提出了无约束宽厚比、平面外间隙等相关设计建议。研究结果表明,采用无粘结材料的试件滞回性能优于未采用无粘结材料的试件。实际应用时,全钢屈曲约束支撑的核心板和约束部件之间可不采用无粘结材料,但对于屈服段长度较长、厚度较小的高性能屈曲约束支撑,应采用无粘结材料。在第4章中,提出了屈曲约束支撑新型部分约束机制,其核心部件只有部分区域被约束部件包裹,使支撑约束部件利用效率提高且震后损伤情况可测:结合第2章和第3章中支撑构造的设计建议,开发了新型一字形核心全钢屈曲约束支撑,通过试验对比了新型屈曲约束支撑和普通屈曲约束支撑的滞回性能和核心部件的多波屈曲行为;通过有限元分析研究了新型屈曲约束支撑核心板表面接触应力、波长以及纵向应变分布等参数。结果表明,新型屈曲约束支撑的无约束宽厚比bu/t不超过5时,其各方面性能与相应普通屈曲约束支撑接近。在第5章中,提出了新型一字形核心屈曲约束支撑的设计建议,并为部分约束新机制的应用和新型H形核心屈曲约束支撑的研发提供了理论基础:将核心板无约束段等效为单向均匀受压四边简支板,推导了弹性和弹塑性屈曲荷载,并得出弹塑性临界宽厚比(bu/t)cr;研究平面外间隙d、核心板厚度t、约束段总宽度b-bu、无约束段宽度bu以及无约束宽厚比bu/t等参数对支撑性能的影响规律;提出两个性能水准下新型屈曲约束支撑的相关设计建议。在第6章中,拓展了部分约束机制在H形核心屈曲约束支撑中的应用,研究了不同边界条件的部分约束核心部件的变形规律,为新型H形核心屈曲约束支撑的研发及其在支撑框架中的加固应用提供了设计原则:提出了端部加强和中部削弱H形核心屈曲约束支撑;试验评估了两种新型H形核心屈曲约束支撑的滞回性能和核心部件的屈曲形态;结合有限元分析了约束部件螺栓的失效以及核心部件翼缘单侧的接触力;提出了两种支撑核心部件翼缘无约束宽厚比的设计建议。在第7章中,提出了将支撑框架体系中H形普通支撑转化为屈曲约束支撑的加固新思路,分析了屈曲约束支撑框架抗震能力:设计了 8度(0.20g)区的3层和9层既有中心支撑框架,并根据第6章端部加强和中部削弱两种思路,提出两种构件层次的抗震加固方案,给出支撑翼缘每侧约束宽度设计值;通过OpenSees对结构进行推覆分析和非线性时程分析,评估加固后屈曲约束支撑框架的抗震能力;首次研究了受压承载力调整系数和等效粘滞阻尼比对屈曲约束支撑框架抗震能力的影响规律。更多还原

【Abstract】 Buckling-restrained brace is not only a type of metal damper,but also a lateral force resisting member without buckling,consisting of the core member,the restraining member,and the unbonding materials or air gap.Under small earthquakes,buckling-restrained braces will maintain elastic and provide the lateral stiffness for the structure.Under severe earthquakes,buckling-restrained braces will dissipate seismic energy after yielding,with the overall or severe local buckling of core member inhibited by the restraining member,which will reduce the seismic response of the structures and avoid heavy damage to the main structure.Buckling-restrained braces can be divided into two categories by the material of the restraining member,which are the concrete-filled steel tube buckling-restrained braces and all-steel buckling-restrained braces.Though all-steel buckling-restrained braces are easy to be fabricated,the configuration details have yet to be optimized and the cost-effective restraining system is to be developed.Moreover,the application in seismic rehabilitation is to be further investigated.To solve these problems,this paper studied all-steel buckling-restrained braces in terms of the common brace configuration details,new restraining systems and the application of buckling-restrained braces in seismic rehabilitation,through theoretical analysis,experimental research and numerical simulation methods.The main contents and conclusions are as follows:In Chapter 2,the effects of the configurations of the core member on the hysteretic properties of buckling-restrained braces were investigated,so as to provide design recommondations for the novel all-steel buckling-restrained braces.Through experiments,the influence of the configurations of the core member,including the transition mode in the transition segment and the length of the core projection and transition segment into the restraining members,on the cumulative plastic deformation and failure modes of all-steel buckling-restrained braces was evaluated.Moreover,strain concentration induced by the configurations of the core member was compared through finite element methods,which revealed the reason for higher low-cycle fatigue property of the improved specimens.The results show that the arc-shaped transition mode and the increase of the length of the core projections and transition segment into the restraining members can alleviate the strain concentration and stress concentration of the core member,which will significantly improve the low-cycle fatigue properties.In Chapter 3,the influence of the unbonding materials on the hysteretic properties of all-steel buckling-restrained braces was firstly studied,to provide theoretical foundation for the novel all-steel buckling-restrained braces.The hysteretic curves,failure modes and cumulative deformation capacity of all-steel buckling restraining braces with and without the unbonding materials were compared through experiments.Further,the multi-wave buckling behavior of the core member was predicted by theoretical derivation,and the formula of the compression strength adjustment factor was proposed.Moreover,the contact force between the core member and restraining member and the strain concentration through the longitudinal direction were investigated by finite element analysis.Finally,the design recommendations,including the out-of-plane gap width and the unrestrained width to thickness ratio,were proposed based on the test and finite element analysis.The results show that the hysteretic properties of the specimens with the unbonding materials are better than those without the undonding materials.In engineering practice,the unbonding materials are not necessary for all-steel buckling-restrained braces,but for high-performance buckling-restrained braces with long yielding segment and thin core member,the unbonding materials should be employed.In Chapter 4,a novel partly restraining mechanism was proposed,where only part of the core member was wrapped by the restraining member,improving the use efficiency of the restraining member and making the damage measurable after earthquake.A novel all-steel buckling-restrained brace was proposed based on the restraining mechanism and the design reccommations of the configurations in Chapters 2 and 3.Its hysteretic performance and the buckling behavior of the core member were compared with those of the conventional all-steel buckling-restrained braces.Further,the contact pressure,the wave length and the strain distribution of the core plate of the novel all-steel buckling-restrained brace were investigated through finite element analysis.The results show that,when the unrestrained width to thickness ratio bu/t is less than 5,the performance of the novel all-steel buckling-restrained braces is close to the conventional all-steel buckling-restrained braces.In Chapter 5,design recommendations of the novel all-steel buckling-restrained braces were proposed,which provide theoretical foundation for the novel H-shaped all-steel buckling-restrained braces and the application of the partly restrained mechanism.The unrestrained section of the core plate was equivalent to a one-direction uniform compressed simply-supported plate.Then,elastic buckling load,inelastic buckling load,and plastic critical thickness ratio(bu/t)cr was derived.Moreover,parametric studies was performed to study the influence of the key parameters,including the out-of-plane gap width d,the core thickness t,the width of the restrained section b-bu,the width of the unrestrained section bu and the unrestrained width to thickness ratio bu/t.Finally,the design recommendations of the novel buckling-restrained brace under two performance levels were proposed.In Chapter 6,the partly restrained system was applied to the H-shaped core member,and the deformation pattern of the partly restrained core member under different boundary conditions was studied,which provide design principle for the H-shaped buckling restrained brace and its application on the rehabilitation of the braced frames.End-strengthened and middle-weakened H-shaped buckling-restrained braces were proposed.The hysteretic properties and buckling behavior of the two types of H-shaped buckling-restrained braces were evaluated by tests.Further,the failure of the bolts and the contact force on the flange were analyzed through finite element analysis.Finally,the design recommendations on the unrestrained width to thickness ratio of the flange were proposed for the two types of braces by numerical analysis.In Chapter 7,two novel rehabilitation methods were proposed,which turn conventional H-shaped braces to buckling-restrained braces in braced frames,and the seismic performance of the buckling-restrained braced frames was investigated.3-storey and 9-storey existing concentrically braced frames in 8 degrees(0.20g)region were firstly designed,and then two member-level seismic rehabilitation schemes were proposed according to the ideas of end-strengthened and middle-weakened H-shaped buckling-restrained braces in Chapter 6.Besides,the design value of the restraining width of each side of the flange was recommended.Through pushover analysis and nonlinear time history analysis in OpenSees,the seismic performance of the rehabilitated buckling-restrained braced frames was assessed.Finally,the effect of the compression strength adjustment factor and the equivalent viscous damping on the seismic performance of the buckling-restrained braced frames was investigated.更多还原