钢框束筒结构剪力滞后分析与楼层损伤评估

Analysis of shear lag and floor damage degree assessment in steel bundled-tube structure

为研究钢框束筒结构中的剪力滞后现象及其对结构设计的影响,分析结构在罕遇地震作用下耗能及楼层损伤情况,建立了有限元分析模型,对结构进行风荷载和多遇地震作用下的弹性分析以及罕遇地震作用下弹塑性时程反应分析。对剪力滞后沿楼层的分布特点以及窗裙梁截面高度变化对束筒结构剪力滞后的影响进行了分析,研究了剪力滞后与楼层损伤之间的关系。通过对楼层的最大有害层间位移角和塑性耗能分析,研究了楼层损伤因子的计算方法,并对楼层的损伤程度进行了定量评估。分析结果表明：钢框束筒结构下部高度1/3范围内为剪力传递敏感区域,仅在该区域加大窗裙梁截面可以得到与全高加大窗裙梁截面接近的空间作用效果。结构剪力滞改善后,应避免局部区域出现应力突变,产生新的更为严重剪力滞后现象。楼层柱应力不均匀系数代表值与楼层塑性耗能在竖向收进局部区段具有相似的分布规律。采用基于归一化的位移和塑性耗能双参数模型算式得到的楼层损伤因子与通过损伤现象确定的楼层损伤因子吻合较好,可用于钢框束筒结构楼层损伤程度的定量评估。

A series of calculation models were designed and made to analyze the energy dissipation of structure and floor damage under rare earthquake,in order to investigate the shear lag phenomenon of steel bundled-tube and its effects on structure design. Based on the finite elements analysis models,elastic analysis under wind load and frequent earthquake and elasto-plastic time history analysis under rare earthquake were used. The calculating data were used to analyze distribution of plastic energy dissipation along story and influence of shear lag with different depth of beams.Relationship between shear lag and floor damage was also studied. The calculation method of floor damage degree was proposed by analysis of harmful displacement angle and plastic energy dissipation of floors. The floor damage degree was quantitatively evaluated. The results show that the 1/3 height range of the lower part of steel bundled-tube structure is shear sensitive region. Increasing depth of spandrel beams in this region can get the same space working effect as increasing depth of all spandrel beams. It is important to avoid stress mutation and severe shear lag in one region during improving the shear lag in another region. Representative value of columns non-uniform stress coefficient which can reflect shear lag of floor has similar distribution patterns to plastic energy dissipation in the section of vertical set back. The calculated floor damage factors agree with the damage phenomena. The proposed formula based on the normalized two parameter model of displacement and plastic energy dissipation can be used to evaluate the floor damage degree of steel bundled-tube structure quantitatively.