自复位支撑钢框架抗震性能评估与损伤演化分析

SEISMIC PERFORMANCE EVALUATION AND DAMAGE EVOLUTION ANALYSIS OF SELF-CENTERING BRACED STEEL FRAME

为研究自复位耗能(SCED)支撑失效前后支撑钢框架结构的抗震韧性及损伤演化规律,设计了一单榀三层自复位支撑钢框架(SCBSF)并对其进行精细化有限元模拟,探究了支撑第二刚度和摩擦力在考虑支撑失效时对结构宏观响应和关键构件损伤状态的影响规律。结果表明,在地震作用下,SCED支撑作为SCBSF第一道抗震防线,激活工作后为结构提供了稳定的耗能与卓越的复位能力,相比屈曲约束支撑(BRB)框架残余变形角最大减小了84.9%,显著降低结构震后修复成本;支撑达到最大行程破坏失效后,结构层间变形加剧,框架梁和柱塑性耗能占比增加了92.33%,主体结构损伤值增加了48.45%,结构的抗震性能与韧性水平明显降低。参数分析结果表明,提升支撑的第二刚度和摩擦力能有效降低结构响应,但具有较大第二刚度和摩擦力的支撑框架仍抵抗不了强震作用时,可能导致更多的支撑失效破坏,结构损伤加剧。因此,设计SCED支撑时,需要适当提高支撑第二刚度和摩擦力,建议第二刚度取值为第一刚度的7/50~4/25,支撑摩擦力与预压力比值取为1~1.2;提升支撑第二刚度相比提升摩擦力对结构损伤值控制效果更好,随着地震动强度增大,摩擦力与第二刚度对结构抗震性能的影响逐渐减小。

To study the seismic resilience and damage evolution law of braced steel frames before and after the failure of self-centering energy dissipation braces(SCED),a single-span three-storey self-centering braced steel frame(SCBSF)was designed.The refined finite element model was established to investigate the influence of the second stiffness and friction force of braces on macroscopic responses of structures and the damage state of key components,considering the failure of braces.The results indicate that the SCED brace as the first seismic line of SCBSF provides stable energy dissipation and excellent self-centering behavior after activation.Compared with the buckling restrained braced(BRB)frame,the residual interstorey drift ratio of the SCBSF is reduced by 84.9%,significantly reducing the repair costs of structures after earthquakes.When the brace begins to fail after reaching its maximum stroke,the interstorey drift of the frame aggravates,and the plastic energy dissipation ratio of frame beam to column increases by 92.33%;the damage value of the main frame increases by 48.45%;and the seismic performance and resilience level of the structure decrease obviously.The results of parameter analysis show that increasing the stiffness and the friction force of the brace can effectively reduce the structural response.However,when the braced frame with large second stiffness and friction force is still unable to resist strong earthquakes,the number of brace failure may increase,causing structural damage aggravation.Thus,it is necessary to appropriately improve the second stiffness and friction force when designing SCED braces.It is suggested that:the second stiffness should be 7/50-4/25 of the first stiffness;the ratio of friction to pre-pressed force should be 1-1.2.The damage control effect of increasing the second stiffness of the brace is better than that of increasing the friction force.With the increase of ground motion intensity,the influence of friction force and the second stiffness on the seismic performance of braced frames decreases gradually.