基于平面框架拟静力试验的RC框架柱的破坏模式研究

Failure mode of RC frame columns based on the plane frame quasi-static test

摘要:

以2008年汶川地震中漩口中学倒塌的教学楼中的钢筋混凝土柱为原型,按照1∶4的比例进行缩尺,通过平面框架拟静力试验对不同剪跨比下 RC 框架柱的破坏模式进行研究.设计3组不同剪跨比(λ=3、λ=4．25及λ=6)的 RC框架柱模型.采用拟静力试验对 RC框架柱进行加载,得到 RC框架柱的滞回曲线、骨架曲线以及不同的破坏模式,定义 RC框架柱抗剪承载力与轴力之比为抗震性能系数α.利用3组试验数据,总结基于抗震性能系数α 的 RC框架柱破坏规律:当抗震性能系数α＜0．16时,RC框架柱发生弯曲破坏,而当α≥0．16时,其发生剪切破坏.因此,在 RC框架柱的抗震设计中应重视抗震性能系数α 的取值,避免柱发生剪切脆性破坏.文章对应变计算剪力的3种方法进行比较,得出线性情况下有效的剪力计算方法,即在试验中通过实测的应变信息反演出 RC框架柱端真实受力状态.

Abstract:

To study the failure mode of reinforced concrete (RC) frame columns under different shear-span ratios, on the basis of the RC columns in Xuankou middle school that collapsed during the Wenchuan earthquake in 2008, a 1:4 RC column model was designed and constructed, and the plane frame quasi-static test was conducted. Three sets of RC frame column models with different shear-span ratios (λ=3, λ=4.25, andλ=6) were designed. The hysteresis curves, skeleton curves, and different failure modes of the RC frame column were obtained through a quasi-static test, and the ratio of shear bearing capacity to axial force of the RC frame column was defined as the seismic performance coefficient α. With the use of three sets of test data, the failure rule of the RC frame column based on the seismic performance coefficient α was summarized: When α ＜ 0.16, flexure failure happens on the RC frame column; when α≥0.16, shear failure happens on the RC frame column. If the value of α is well grasped in the seismic design of the RC frame column, then the shear and brittle damage of the column can be avoided. In addition, three methods for calculating the shear force from strain were compared, and an effective shear force calculation method in the linear case was obtained; that is, the actual stress state at the end of the RC frame column was retrieved by the measured strain information.