芦山地震单开间砌体结构房屋震害特征

Analysis on Damage Characteristics of Single-bay Street Farmhouses in Lushan Earthquake

4.20芦山地震灾区临街自建单开间砌体结构房屋震害特别严重,本文基于现场调查研究该类特殊房屋的建造习惯、震害特征与损伤机理,研究表明:单开间砌体房屋是芦山地震灾区等四川小城镇比较常见的临街建筑模式,其平面狭长,建造随意,结构体系不合理,构造措施不到位,抗震能力弱;芦山地震地震烈度8、9度灾区单开间砌体房屋底层纵墙剪切破坏,普遍出现严重的贯通整片墙体的斜裂缝或X形裂缝。底层前部房间横墙无纵向支撑,独立墙段过长,横墙压弯破坏出现贯通整片墙体的水平裂缝,并且墙体外鼓;结构刚度中心与质量中心严重偏离,房屋扭转震动加剧墙体裂缝开展,相邻建筑反复碰撞作用是上部楼层震害的主要原因;鞭梢效应加重突变楼层结构损伤,引起出屋面附属建筑严重破坏甚至倒塌,横墙端部剪切断裂乃至溃散。据此,提出了既有单开间砌体房屋加固工作的建议。

The damage of single-bay street farmhouses built with masonry is especially heavy during Lushan earthquake disaster.Based on field investigation,this paper studies the construction habit and earthquake damage characteristics of this type of special buildings.The research shows that the construction of single-bay masonry houses is relatively common in Lushan earthquake-stricken area and other small cities in Sichuan.The unreasonable house length,arbitrary construction,chaotic structural system and the absence of constructional measures should be responsible for the weakness of earthquake-resistant capacity of the house.The shear failure at the bottom of the longitudinal wall of singlebay houses results in oblique cracks or X-shaped cracks that cut through the entire wall in the areas with earthquake intensity between 8 and 9.The cross wall of the ground floor is relatively long without longitudinal support,which leads to the cross wall cracks and protrudes outward due to press-bend failure.Structural stiffness center and mass center deviate seriously,hence the effect of torsion and vibration aggravates the development of wall cracks.The repeated collision of adjacent buildings is the main cause for the damage of the upper floor.The whiplash effect aggravates the damage of the floor structure,causing the upper accessory structure severe damage or even collapse.Besides,the end of the cross wall suffers fracture or collapse for the shear failure.Accordingly,suggestions for strengthening existing single story masonry buildings are put forward.