Study On Seismic Behavior Of Structure Constructed Of Autoclaved Sand-lime Bricks

The use of sand-lime bricks is increasingly extensive,but the author investigated several earthquakes since the 2008 Wenchuan earthquake,the seismic performance of sand-lime brick masonry structure is significantly lower than that of clay brick masonry.In view of the old county seat of Hanyuan County to multi-layer sand-lime brick masonry.After the 2008 Wenchuan earthquake,its intensity was 3 degrees higher than the background area.In order to explain the high intensity anomaly,the shear strength of the sand-lime brick masonry and fired clay brick masonry are discussed by seismic behavior comparison,simulation test and theoretical analysis.Main results are as follows:1.The survey of seismic behavior of sand-lime brick masonry in different earthquakes are carried out such as Wenchuan earthquake,Lushan earthquake,Changning earthquake,Gongxian earthquake.In the same earthquake,when fired clay brick masonry have not been changed,sand brick masonry have been damaged,manifested as the wall “X” type through cracks and even collapse.2.A special test device had been designed,and shear strength tests on the specimens of nearly 100 groups were carried out.And the influence of mortar strength,vertical positive stress and other parameters on the shear strength were discussed.3.Two groups of sand-lime brick masonry wall pieces that are like real situation and two groups of clay brick masonry wall pieces were tested.In order to solve the problem of the positive stress at the bottom of the wall sheet in the test,the innovative shear test was proposed.In the wall shear test,the shear strength along the through joint of sand lime brick masonry is 70% of that of clay brick masonry,which is consistent with the proportion of the shear strength in the Code for seismic design of buildings.4.Through the shear strength test along the through joint under the constrained state,the motion coefficient of friction between the clay brick surface and mortar layer surface increases in the sliding process,while the motion coefficient of friction between the sand-lime brick surface and mortar layer surface remains unchanged in the sliding process.In the practical use of sand-lime brick masonry,it is difficult to produce capillary action,so the bonding effect of mortar and brick surface is poor.As a result,the mortar layer surface and the surface of sand-lime brick are extremely smooth.It is difficult to engage the two contact surfaces,resulting in the loss of integrity of the wall sheets and collapse in the earthquake.5.Considering the low shear strength and high density of mortar and sand brick masonry（126% of clay brick）,its critical seismic shear force is also 0.55 times that of clay brick masonry.In another words,when the sand-lime brick masonry is damaged,the clay brick masonry has nearly 80% itself safe reserve.Such an obvious difference in seismic resistance can explain the high intensity abnormality in Hanyuan County.