内框架加固典型砌体结构的抗倒塌机制试验

Experimental study on collapse resistance mechanism of typical masonry structures strengthened with inner frames

为解决既有老旧农宅的修补与加固问题,以两开间的北京某单层砌体结构为原型,根据内框架加固思路提出了一种以内嵌式轻型钢框架加固为主,钢板带加固为辅的加固方法,并设计了1/4的砌体结构振动台模型进行振动台试验。试验结果表明:模型结构在小震作用下即出现明显损伤,在中震与大震作用下结构横墙出现明显的外倾,但由于钢框架与钢板带的加固约束作用,并未发生倒塌,外闪程度控制在安全范围内,加固后的结构达到了“大震不倒”的设防目标;随着地震荷载的逐次加载,结构自振频率逐渐衰减;试验模型的加速度放大系数随着地震强度的增加,在整体上呈现减小的趋势,当采用内钢框架与钢板带进行加固后,结构加速度放大系数有微小的增大趋势;结构的位移随着震级的增大而增大,且前檐口的位移大于后檐口的位移,出现了扭转效应;内钢框架在大震后仍保持未损坏的状态,避免了结构发生整体倒塌,保证了结构的安全性。

To solve the problems of repair and reinforcement of existing old rural houses,taking a single-layer masonry structure with two bays in Beijing as the prototype,according to the idea of inner frame reinforcement,a reinforcement method based on embedded light steel frame reinforcement and supplemented by steel plate reinforcement was proposed,and a 1/4-scale masonry structure shaking table model was designed for shaking table test.Test results show that the model structure had obvious damage under the action of small earthquake,and the transverse wall of the structure had obvious extraversion under the action of moderate earthquake and large earthquake.However,due to the reinforcement and restraint effect of steel frame and steel strip,the structure did not collapse,the degree of the external flashover was controlled within the safe range,and the strengthened structure achieved the goal of“no collapse in large earthquakes”.With the successive loading of seismic loads,the natural frequency of the structure decreased gradually.With the increase in seismic intensity,the acceleration amplification coefficient of the test model decreased on the whole.When the inner steel frame and steel strip were used for reinforcement,the acceleration amplification coefficient of the structure had a slight increase.The displacement of the structure increased with the increase in the earthquake magnitude,and the displacement of the front cornice was greater than that of the rear cornice,leading to the torsion effect.The inner steel frame remained undamaged after the earthquake,which avoids the overall collapse of the structure and ensures the safety of the structure.