底部采用高性能纤维增强混凝土的RC剪力墙结构抗震性能分析

Seismic performance analysis of RC shear wall structure with fiber-reinforced concrete in plastic hinge region

剪力墙结构底部采用高性能纤维增强混凝土材料(ECC)能够减轻底部剪力墙在地震中的损伤程度,提高结构震后可恢复性。为考察底部采用ECC材料后整体结构的抗震性能,以我国抗震设防烈度为8度、设计基本地震加速度值为0.2g的高烈度抗震设防区RC剪力墙结构为对象,建立了高度、ECC设置高度和剪力墙整体性系数不同的结构模型,并进行有限元动力时程分析,考察底部采用ECC材料的剪力墙结构与普通RC剪力墙结构抗震性能的差别;分析剪力墙结构在罕遇地震作用下发生预期延性破坏模式时的弯矩需求。结果表明,对于位于设防烈度为8度、设计基本地震加速度值为0.2g抗震设防区的剪力墙结构,将剪力墙底部采用ECC材料后,其在罕遇地震作用下能够耗散更多地震能量,剪力墙开裂的程度和概率明显减小;在剪力墙底部加强区第1~2层采用ECC材料后,ECC层及其相邻上层会发生弯曲破坏;底部加强区第1~3层剪力墙都采用ECC时,剪力墙屈服都集中在ECC层,在罕遇地震作用下ECC层以上剪力墙实现预设延性破坏模式的受弯需求不大于其受弯能力;建议25层以下的剪力墙结构在底部第1~3层范围内采用ECC材料。

Employing the engineered cementitious composite(ECC)in the bottom of shear wall can reduce the damage of the bottom shear wall in earthquakes and improve the recoverability of the structure after earthquakes.A serial of RC shear wall structures with different ECC replace heights,structural heights and integrity factors were designed,according to the current Chinese seismic design code for buildings in the regions of SFI 8(seismic fortification intensity),APG=0.2g,to investigate the differences in seismic performance between the shear wall structures with ECC stories at the bottom and the ordinary RC shear wall structures based on the finite element dynamic time-history analysis.Accordingly,analytical models with preset ductile failure modes were developed to investigate the distribution of bending moment demands along structural height under rare earthquake excitations.The results show that when the bottom of the shear wall is replaced with ECC material,the ECC shear wall can dissipate more seismic energy,and the probability and degree of cracking of the shear wall are significantly reduced.The bending failure of the ECC stories and its adjacent upper story will occur when the 1-2 stories of the reinforced zone at the bottom of the shear wall adopt ECC material.When ECC is adopted for the three stories of shear walls in the bottom reinforcement zone,the yield of the shear walls concentrates on the ECC stories,and the flexural resistance demand of shear wall adjacent to the ECC floor for realizing default ductile failure is not greater than its bending capacity.ECC material is recommended for the bottom three stories of shear wall structures up to 25 stories.