自复位钢筋混凝土框架结构及其拟静力试验

Tri-axial Self-centering Reinforced Concrete Frame and Its Quasi-static Test

自复位钢筋混凝土框架结构是一种新型可恢复功能结构。相比于普通混凝土框架,该结构在地震作用下结构损伤轻微残余变形小,在地震后不需修复或稍加修复即可重新投入使用。因此,该结构是一种适用于高烈度地震频发地区中低层框架的低成本新型防震结构。自复位混凝土框架结构体系使用无粘结预应力筋连接结构中的各个构件,在结构的节点位置形成可以互相分离的界面。在较大的地震作用下,构件间允许发生界面分离,表现为梁端节点张开与柱脚节点提离等现象,从而减轻了结构的损伤。震后在预应力的作用下,构件间的界面重新闭合,实现自复位。首先总结了已有自复位节点的研究成果,阐明了自复位结构的组成与关键构造。为了进一步研究自复位钢筋混凝土框架在地震作用下的变形模式与受力特征,进行了三向自复位框架结构的1:2.5缩尺模型拟静力试验。本文给出了试验模型的基本信息,包括模型的设计参数,材料性能,具体构造等内容;给出了主要的静力试验结果,包括试验的主要现象与损伤特征、模型的变形模式、滞回曲线、骨架曲线、刚度退化与残余变形等信息。试验结果表明:模型的变形能力强,在1/38顶层位移比(顶层位移/结构高度)下模型除少数细微裂缝外没有损伤,在更大的变形下模型损伤逐渐在梁端节点位置开展;在1/19顶层位移比下模型的承载力仍然没有出现下降;模型的残余变形很小,在模型加载的全过程中,其残余位移角都处在可以接受的范围内。

Self-centering reinforced concrete frame is a new type of earthquake resilient structure.Comparing to conventional RC structures,self- centering structure is known for its minimal damage under earthquakes and little residual deformation after earthquakes.Considering the fact that there is none or very little repair needed to restore its functionality after rare earthquakes,self-centering RC frame system is a low cost seismic structure that is very suitable for low-rise frame buildings in high seismic zones.In self-centering structure,beams and columns are connected by clamping force provided by unbonded post-tensioning tendon.By this means,when subjected to severe earthquakes,the gaps at self-centering joints are allowed to open and the columns are allowed to uplift at the base.The opening and uplifting behavior significantly mitigates the damage.After unloading all the gaps between components will close under clamping force,and thus the components restore their original position with negli- gible residual deformation.The existing researches on self-centering joints were summarized,and the key configuration of self-centering joint was illustrated.Based on this research,a tri-axial self-centering RC frame was proposed.In order to investigate the deformation capacity and mechanic- al characteristics of the tri-axial self-centering RC frame,a 1 ： 2.5 scaled model frame was designed and tested under quasi-static load.The config- uration of the test model and main test results,including deformation pattem,hysteretic curve,skeleton curve,stiffness degradation and residual de- formation were otained.The experimental results showed that：the test model has excellent deformation capacity,and no damage is observed expect some minor cracks under 1/38 roof drifi ratio.The damage gradually develops in beam end joint area when the structural deformation continues toincrease.Until 1/19 roof drift ratio,base shear is still increasing which implies that there is still reserved capacity in the structure.The residual de- formation of the model is minimal,and the residual interstory drift ratio is still permissible after the final cycle of the loading process.