钢筋强度对钢筋混凝土框架柱破坏模式的影响

The Influence of Steel Strength on Failure Mode of Reinforce Concrete Frame Columns

弯曲破坏、剪切破坏是钢筋混凝土柱的一种典型震害形式,为研究不同强度钢筋的钢筋混凝土(reinforce concrete,RC)框架柱抗震性能,进行了两组剪跨比为3,共12根柱的1/4缩尺平面框架拟静力试验。对其破坏形态,延性以及应变,抗剪、抗弯承载能力进行对比分析。结果表明:钢筋强度对柱的破坏模式有影响,配置高强度钢筋的框架柱以剪切破坏为主,延性较差,滞回曲线“捏拢现象”明显,呈纺锤形,属于脆性破坏;配置低强度钢筋的框架柱以弯曲破坏为主,表现出较好的延性特征和耗能性能,破坏前有明显的变形,且柱应变为另一试验的1/2。另外根据两组试验相关参数进行不同钢筋屈服强度、不同混凝土等级的抗弯及斜截面抗剪承载能力计算;引入钢筋与混凝土的匹配度系数α作为衡量柱破坏模式的参数:α<0.46时,柱会发生弯曲破坏;α>0.48时,柱发生剪切破坏。因此在RC框架柱的抗震设计中,所配置钢筋强度与混凝土强度的匹配度问题应引起重视。

Bending failure and shear failure are typical forms of earthquake damage of reinforced concrete columns.In order to study the seismic performance of reinforce concrete(RC)frame columns with different steel strengths,two quasi-static tests on the 1/4 scale plane frame for 12 columns with the aspect ratio 3 were conducted to study the seismic performance of RC columns.The failure patterns,ductility,strain,shear and bending strength were studied.The test results show that the strength of steel bar has influences on the failure mode of column.The columns with high strength steel bars are dominated by shear failure,with bad poor ductility and clearly“pinching effect”in the shape of a spindle,thus leading to a non-ductile behavior.The columns with low strength steel bars are dominated by flexural failure,with good ductility and energy dissipation and obvious deformation before failure,and the strain of the column is 1/2 of another test.In addition,the flexural and shear strength of columns by different yield strength of reinforcing steel and concrete grades are calculated by the tests parameters,and the reinforcing steels and concrete matching coefficientαis referred as the parameter to measure the failure mode of columns.Whenα<0.46,it is flexural failure,andα>0.48,the shear failure occurs.Therefore,the matching degree between the strength of the reinforcing steel and concrete should be paid attention to seismic design of RC frame columns.