Study On The New Technique Of Repairing And Strengthening Masonry Walls With Continuous Carbon Fiber Sheet

Masonry building system, in which the solid clay bricks or the concrete blockunits are used for the main construction materials of the walls, is one of the commonlyused types of structures in the world, especially in some developing countries. As thestructural performance of masonry wall is comparatively brittle, some walls in thebuildings need to be repaired and strengthened due to excessive external loads orunevenly distributed deformation. And a lot of existing old masonry buildings need tobe rehabilitated before an earthquake or retrofitted after the earthquake in the seismicareas.Firstly, an experimental investigation is presented on evaluating the effectivenessof the retrofitting system on masonry walls with continuous carbon fiber sheet (CFS).Twelve specimens, six walls made of solid clay bricks and six walls made of concreteblock units, were designed and tested under combined uniformly distributed constantvertical load and cyclic lateral load. The test data indicate that the cracking load andthe ultimate load of the strengthened wall are increased remarkably, compared withthe unreinforced masonry wall. The displacement capacity and energy dissipationcapacity of masonry wall are improved when strengthened with strips of CFS, and thecracking displacement of the strengthened wall also has a large increase. The action ofcomposite strips is similar to that of the diagonal braces in the truss analytical model.And the shear force contributed by CFS strips is mainly coming from the action oftension bars in the analytical model. On the other hand, the use of CFS can also delaythe appearance of the cracks and restrict their development in the masonry walls.Secondly, a FEM software was used to conduct an analytical study on the shearbehavior of unreinforced masonry walls and retrofitted walls with CFS strips. It isfound from the analytical results that the vertical load has little effect on the style ofthe retrofitting system, but with the increase of vertical load, the strengtheneffectiveness will be better. It is also found that for the low aspect ratio (height/width)of the wall, the Λ–strengthening system using strips of CFRP sheet is likely to be aneffective method.Lastly, based on experimental and theoretical study, a simplified analyticalmodel and computing method is provided. The computing method concerned may betentatively used in the retrofitting design of masonry walls, made of solid clay bricksor made of concrete block units, using X–strengthening system with continuouscarbon fiber sheet.