不同抗震等级RC梁抗震性能试验研究

Experimental study on seismic behavior of RC beams with different seismic grades

通过9根钢筋混凝土梁的低周往复试验,对比研究不同抗震等级RC梁的破坏形态、延性、滞回性能、耗能能力及刚度退化等。结果表明:剪跨比为2.0的试件发生弯曲滑移破坏,剪跨比为3.0的试件和剪跨比为4.2的试件发生弯曲破坏;剪跨比为2.0的试件抗震等级分别为二级和四级,表明满足规范抗震等级要求的RC梁试件无法避免发生弯曲滑移破坏;同组试件中,抗震等级越高(配箍率越大),试件的极限位移角越大。除去发生弯曲滑移破坏的试件,试件的极限位移角随抗震等级的提高呈线性增长趋势;抗震等级相同时,弯曲滑移破坏的试件刚度退化比弯曲和弯剪破坏试件严重;弯曲滑移破坏与弯曲破坏的RC梁试件其耗能分别集中在塑性阶段的前期和中后期。

To compare and study the failure modes,ductility,hysteretic behavior,energy dissipation capacity and degradation of stiffness of RC beams that were designed with requirements of different seismic grades,9 RC beam specimens were tested under low frequency cyclic loading. The result shows: the beams with a shear span ratio of 2. 0fail in flexure-sliding while the beams with shear span ratios of 3. 0 and 4. 2 fail in flexure; the beams with a shear span ratio of 2. 0 meeting the requirements of grade 2 and grade 4 can develop a flexure-sliding failure which means that fulfilling the seismic grade requirements of the code can't prevent the flexure-sliding failure in RC beams; In the same group,the beams with a higher seismic grade( the ratio of stirrup is higher) have larger ultimate drift ratios.When the beams fail in flexure-sliding are excluded,the ultimate drift ratio of the remaining RC beams shows a linear positive correlation with the corresponding seismic grade. With the same design seismic grade,the beams failed in flexure-sliding degrade more severely in stiffness than those failed in flexure or flexure-shear. The concentrated part of energy dissipation occurs at early stage of loading for the beams failed in flexure-sliding and at later stage for those failed in flexure.