T形钢管混凝土柱框架节点抗震性能研究

Special-shaped column frame structures can overcome shortage of column convex corner exposed to the indoor space which is prevalent in traditional square and rectangular column frame structures. Accordingly, special-shaped column frame structures improve residential indoor architectural environment and boost indoor serviceable space efficiency. However, the prevalently applied special-shaped reinforced concrete column has thin section components, which leads negative effects on joint shear resistance and hampers its further generalization and application in high seismic fortification zones and decreases its maximum applicable building height. Special-shaped concrete-filled steel tubular column frame joint has good seismic behavior by providing combination effect of concrete and steel. However, the joint is still in its infancy and needs further comprehensive research. This project plan includes experimental research in seismic behavior of T-shaped concrete-filled steel tubular column frame joints. Load transmission mechanism, failure mode and mechanical property index are studied. Parameters of axial compressive load ratio, web cross sectional height, steel ratio of T-shaped tube, and concrete strength grade are considered to investigate their influencing rule in joints' seismic behavior. Advantages and disadvantages in joints' seismic behavior are evaluated. Based on the experimental results, finite element model of joints is established to carry out parametric analysis. Simplified shear resistance calculating formula and shear force-displacement restoring model are proposed and design methods for engineering application are put forward.

异形柱框架结构能够有效解决普通方矩形柱框架结构室内柱角外露的不足，改善室内环境观瞻，提高室内空间使用效率。普遍应用的异形钢筋混凝土柱由于柱肢较薄，对节点抗剪承载力不利，限制了其在高设防烈度地区的应用，相同设防烈度下房屋最大高度也远远小于普通框架结构。异形钢管混凝土柱框架节点凭借钢和混凝土的组合效应能够有效改善节点抗震性能，目前研究尚处于起步阶段。本项目将进行T形钢管混凝土柱框架节点的抗震性能试验，研究节点的受力机理、破坏模式和力学性能指标，考察轴压比、腹板肢长、钢管含钢率、混凝土强度等级等参数对节点抗震性能的影响规律，评价节点抗震性能的优势和不足。在试验研究基础上，进行节点有限元建模计算，并进行相关参数影响分析，提出节点抗剪承载力简化计算公式和节点低周往复加载恢复力模型，并给出工程应用设计方法。

本项目进行了异形钢管混凝土柱框架节点抗震性能试验和数值分析研究。异形柱截面包括十字形和T形两种，均内置对拉钢筋加劲肋以延缓钢管的局部屈曲，增强对核心混凝土的约束效应。节点传力构造包括外环板和竖向肋板两种，外环板将钢梁翼缘拉力传递给柱钢管腹板，虽然对建筑室内空间略有干扰，但继承了圆形和方形钢管混凝土柱框架节点构造可靠的优势；竖向肋板虽然传力效果略低于外环板，但其对建筑室内空间无干扰，符合异形柱结构的建筑功能初衷。节点抗震试验在MTS协调加载系统下进行，梁、柱均取反弯点之间部分，端部边界条件均为铰接，在柱顶施加恒定竖向荷载和水平往复荷载。试验中得到柱端水平荷载-位移滞回曲线、梁弯矩-转角滞回曲线、节点核心区剪力-剪切变形曲线、梁柱弯曲变形曲线以及节点翼缘、腹板、外环板、竖向肋板应变曲线。结果显示两种形式异形钢管混凝土柱框架节点均能较为充分发挥钢梁的抗弯性能，刚度、承载力、变形能力和耗能性能均能满足抗震要求，其中外环板节点的承载力、延性、耗能等力学性能均略好于竖向肋板节点。各节点破坏模式均依次表现为钢梁翼缘屈服-柱钢管被拉脱开-外环板或竖向肋板与钢梁翼缘或柱钢管连接焊缝开裂。结合试验研究结果，本课题还深入进行了异形钢管混凝土柱框架节点抗震性能数值分析。应用数值程序分析了外环板和竖向肋板形状参数、柱轴压比、梁剪跨比等因素对节点抗震性能的影响规律，并提出了异形钢管混凝土柱框架节点简化设计方法和构造措施。本课题研究的外环板异形钢管混凝土柱框架节点和竖向肋板异形钢管混凝土柱框架节点具有优良的抗震性能，能够在高层建筑结构和较高抗震设防烈度地区的建筑结构中得到推广和应用。