Experimental Study On The Behavior Of Mortar Joint Of Sawn Stone Walls

With the development of machine cutting technology of stone,the traditional hand-cutting ashlar stone(HCAS)used in the construction of stone masonry structure is gradually replaced by the sawn ashlar stone(MCAS).In compared with HCAS,the surface of MCAS is more smooth,which results in significant difference of the shear performance of mortar joint between MCAS masonry and HCAS masonry.It is necessary to carry out deep research on the shear performance of mortar joints of MCAS masonry,which affords important research basis for the design theory of MCAS masonry structure.In order to investigate the failure process,shear strength,deformation behavior and seismic performance of mortar joint of the MCAS masonry wall,monotonic static loading tests on 20 MCAS masonry walls and quasi-static loading tests on 6 MCAS masonry walls were carried out.The primary parameters included normal compressive stress,groove amount in the interface,and mortar strength.The main results are summarized as follows:(1)Shear-slip failure mode occurred in the mortar joints of all MCAS masonry walls,and the failure process can be divided into three stages,i.e.,elastic stage,cracking stage and frictional slip stage.During the elastic stage,the horizontal load rises sharply with small deformation,and linear relationship existed in the shear stress-displacement curves.In the cracking stage,the horizontal load dropped quickly as soon as the shear cracks occurred in the mortar joint.In the frictional slip stage,the horizontal load was stable,and the residual shear capacity of the mortar joint increased with the increase of normal compressive stress.(2)For the low-cycle loading specimens,in the initial stage,the mortar joint kept elastic,and the hysteretic curves is approximately linear with small residual deformation.With the increase of the displacement amplitude,the strength and stiffness of the mortar joints decreased due to the damage evolution,and the shape of the hysteretic loop was almost fusiform with obvious nonlinear characteristics andincreasing residual deformation.In the frictional slip stage,the load kept stable,and the hysteretic loop was full,which indicated favorable energy-dissipation capacity.(3)The shear strength of the mortar joints increased with the increase of groove amount in the interface,the normal compressive stress and the mortar strength.The effect of normal strength and mortar strength are more significant than that of groove amount.The influence of normal compressive stress on the residual shear strength of the mortar joint with grooved interface was more significant than the mortar joint with smooth interface.(4)Based on the regression analysis of the test results,a formula for calculating the shear strength of mortar joints of MCAS masonry wall is proposed,and the calculated result is in good agreement with the test result,which provides the design basis for practical engineering.