Experimental Study On Mechanics Of Historic Masonry Walls Strengthened With Mortar Replacement

The reinforcement of historical buildings has always been a problem.For the masonry structure included in the scope of cultural relics protection,on the one hand,we must adhere to the principle of minimum intervention,maintain the appearance and cultural characteristics of the building itself,and on the other hand,ensure the safety and seismic performance of the structure,while the existing approaches have too many changes to the buildings that would not be recognized by experts of cultural relic protection.Based on this contradiction,this paper proposes a new method of masonry reinforcement.By replacing the gray seam with a certain depth with high-performance mortar,the mechanical properties of the masonry structure can be improved without changing the facade.Moreover,this method can also be combined with the joints on the building repair to achieve the effect of the two-in-one construction and structure repair and reinforcement.In this paper,the effects of displacement mortar reinforcement on the basic mechanical properties of masonry are investigated by axial compression test and pure shear test.The compression test consisted of two batches,taking into account factors such as displacement mortar depth,single-sided displacement and replacement of vertical joints.It has been found through experiments that the compressive strength is reduced after replacing the higher strength cement mortar,and the double-sided replacement is more than the single-sided strength.As the depth of the motar change increases,the compressive strength continues to increase,too.In the case of single-sided displacement,the replacement of the vertical joint is not conducive to compression;in the case of double-sided replacement,the replacement of the vertical joint can increase the compressive strength.In the pure shear test,single-sided displacement was used,and only the influence of the displacement of the gray seam was considered.The results shovw that the increase in shear strength is significant.When the displacement depth is 6 cm,the shear strength is almost doubled.There are differences of failure characteristics between members unreinforced and reinforced ones.The cracks of the compressive members are evenly distributed when unreinforced.After the reinforcement on one side,the vertical or oblique split cracks are generated in the reinforcement area,and the through cracks are formed in the middle of the side.After double-sided reinforcement,a through crack occurs mainly in the middle of the side face.According to the test data,the stress-strain curve and elastic modulus of the masonry members are calculated and analyzed.In the pure shear test,the components are damaged at the mortar layer and the interface.When the reinforcement depth reaches 6 cm,local damage will occur to the brick body.The ANSYS finite element was used for nonlinear simulation of the members before and after reinforcement.It was found that after reinforcement,the stress concentration at the intersection of new and old mortar was very large,and the compressive stress in the reinforcement area was significantly larger than that in the unreinforced area.In this paper,the existing calculation methods of masonry compressive strength are summarized.The suitable calculation formulas are proposed for the unreinforced members based on the elastic analysis theory.For the reinforced masonry,the simplified compressive strength formulas is proposed according to the stress distribution of the mortar layer.