双阶屈服屈曲约束支撑框架小震参数分析

为了弥补常规屈曲约束支撑在多遇地震作用下处于弹性状态,不能发挥消能减震作用的不足,提出了一种将金属套管阻尼器与屈曲约束支撑组合形成的双阶屈服屈曲约束支撑,经试验验证其具有良好、稳定的小震及中大震下的滞回特性。在小震作用下,金属套管阻尼器屈服消能,屈曲约束芯板保持弹性承载。借助有限元软件ETABS建立了一系列双阶屈服屈曲约束支撑框架模型,通过改变支撑与框架刚度比、阻尼器与芯板的轴向刚度关系以及套管阻尼器的屈服比例,对各模型进行小震作用下的动力弹塑性分析,将各模型基底剪力和最大层间位移角与相应的常规屈曲约束支撑框架的分析结果进行对比。结果表明:双阶屈服屈曲约束支撑与支撑芯板的轴向弹性刚度比取2左右,阻尼器屈服比例取0.3左右时,可取得较好的减震效果; 双阶屈服屈曲约束支撑的参数取值改变,对降低结构地震响应的影响趋势不因支撑与框架刚度比不同而改变; 当支撑刚度贡献较大时,相较常规屈曲约束支撑,双阶屈服屈曲约束支撑的设置能降低结构的层间位移角,若要同时降低基底剪力,阻尼器屈服比例不宜高于0.3。

Parametric Analysis of Frames with Two-level-yielding Buckling Restrained Braces Under Frequent Earthquake

In order to overcome the deficiency that the conventional buckling restrained braces(BRBs)were in elastic state under frequent earthquakes, and cannot dissipate energy, a novel two-level-yielding buckling restrained brace composed of conventional BRB and metal tube damper was developed, and its reliably and stable hysteretic characteristics under both frequent and large earthquakes were verified by experiments. Under frequent earthquakes, the metal tube damper yields to dissipate energy and the buckling restrained core plate keeps elastic. A series of braced frame models with the novel braces were established by means of the finite element software ETABS. By changing the stiffness ratios of braces and frames, the axial stiffness relationship of tube dampers and core plates, and the yield ratios of tube dampers, the dynamic elastoplastic analysis under frequent earthquakes of each model was carried out, while the base shear forces and the maximum inter-story drift angles were compared with the analysis results of corresponding BRB frames. The results show that when the axial elastic stiffness ratio of the novel two-level-yielding buckling restrained brace and core plate is about 2, and the yield ratio of tube damper is about 0.3, the structure can achieve better seismic reduction effect. The parameter change of the two-level-yielding buckling restrained brace for the influence tendency of reducing structural seismic response does not vary with the different stiffness ratios of braces and frames. For braced frames with large brace stiffness, compared with the conventional BRB, the inter-story drift angles of the structure can be reduced by setting the two-level-yielding buckling restrained brace. If the base shear force is to be reduced at the same time, the yield ratio of damper should not be higher than 0.3.