混凝土结构设计中常见的稳定问题

Common Stability Problems for Design of Concrete Structures

混凝土结构的稳定问题受重视程度不及钢结构,本文对比中国、欧洲、美国和新西兰的混凝土设计规范中关于结构整体稳定、构件稳定的条文,并结合示例和公式推导,给出相关设计建议。对于整体稳定,刚重比数值受侧向合力位置、建筑重力大小及位置的影响,不应简单地以刚重比的数值来评判不同建筑的整体稳定性。对于构件稳定,分析了几个常见而易被忽视的问题。穿层柱及支撑连桥的框架柱宜考虑二阶效应;对于大跨度梁和长悬臂梁可借鉴外国规范,控制梁的高宽比和侧向无支撑长度;通过数值屈曲分析来反算柱子计算长度时,应正确施加荷载;国内对墙肢的稳定限制较严,对比墙肢的稳定等效荷载与轴压比限值荷载,给出了楼梯间外墙和L形剪力墙的截面由稳定控制的临界高度。

The stability of concrete structure is not considered as vital as that of steel structure.This paper compares the provisions on overall stability of structure and members’stability in concrete design codes of China,Europe,USA and New Zealand,some relevant design suggestions are given by combining examples and formula deduction.For the overall stability,the rigid-gravity ratio value is affected by the resultant position of lateral forces,the magnitude and position of building gravity.The overall stability of different buildings should not be simply judged by the stiffness-weight ratio.For the stability of members,several common but easily ignored problems are analyzed:second-order effect should be considered for columns supporting bridges and cross-story columns;by reference foreign codes,the height-width ratio and lateral unbraced length of beam should be controlled for long-span and long cantilever beams;loads should be applied correctly when solving the effective length of columns by buckling analysis.The stability of shear walls is strictly restricted in China.In this paper,the critical height of outer wall in staircase and L-shaped shear wall limited by stability is given by comparing the equivalent load of stability of wall limbs with the limit load of axial load ratio.