支撑节点板对铰接框架梁柱附加弯矩的影响

Influence of gusset plate connections on the secondary moments in beams and columns of braced frames

摘要:

为研究产生层间变形时支撑的节点板对钢框架梁柱铰接节点产生的转动约束能力及在梁柱中产生的附加弯矩,并揭示这种附加弯矩对梁柱设计的不利影响,利用ANSYS通用有限元程序中的壳单元建立了单斜支撑框架结构的单层单跨模型,分析了附加弯矩与层间侧移的关系．按支撑受压和受拉时两种状态,分别研究了节点板厚度、边长和柱轴压比、钢材强度等关键因素对铰接框架梁柱附加弯矩的影响规律．分析表明:梁柱附加弯矩随层间侧移的增大而增大,若节点板尺寸较大,甚至会迫使节点板边缘处的铰接梁柱形成塑性铰;弹性阶段支撑受压时的附加弯矩小于支撑受拉的情况;梁柱附加弯矩随柱轴压比增大有减小的趋势．依据统计参数分析的量化结果,给出了附加弯矩在梁柱设计中的建议取值．

Abstract:

To explore the secondary moments on the columns and beams in steel braced frame arising from the reaction introduced by the gusset plates of bracing members with the developing story drift, and to obtain this unwanted effects on the frame members, a series of diagonally braced frames (one-story and one-span) where the braces are connected with gusset plates are simulated by using shell elements in ANSYS program. By considering two conditions in which the brace is compressed or tensioned respectively under story drift, the secondary moments in the columns and beams influenced by the key factors such as gusset plate thickness, length of gusset plate, axial compression ratio of columns, and yield strength of steel used in the frames are investigated. It is shown that the secondary moment increases with the increase of story drift, and can even form plastic hinges in both the beam and the column if a stronger gusset plate is employed. At elastic limit state of the braced frames, the tensioned brace can cause smaller secondary moment than the compressed one. The axial compression ratio of columns can slightly decrease the secondary moment. Based on the statistic results of the parameter analysis, reasonable values of the secondary moments are suggested for the engineering design of the columns and beams.