Study On The Mechanical Performance And Calculation Method For Strengthening Brick Masonry Columns And Walls Using Textilereinforced Concrete

Masonry structures have a larger vulnerability in natural disasters such as earthquake actions.Strengthening is one of the effective methods to improve the security of masonry structures.Textile-reinforced concrete(TRC)is a type of continuous fiber reinforced cementitious matrix,and has a good mechanical property and durability.TRC has a better adaptability with the masonry substrate,and as a result,it has extensive application prospects in the field of strengthening masonry structures.In this dissertation,the interfacial bond property between TRC and masonry substrate,the compressive performance of brick masonry columns confined by TRC and the shear performance of brick masonry walls strengthened with TRC were mainly studied and discussed via the method of combining the experimental,theoretical and statistical analyses from the two levels of the interface and member.The main research works and conclusions obtained are as follows.(1)The interfacial bond property between TRC and masonry substrate was developed via the experimental investigation and theoretical analysis.The interfacial failure mechanism was studied,and the influences of the interfacial bond length,the types of textiles and the surficial treatment method of textiles on the interfacial carrying capacity and ductility factor were mainly analyzed.The effective bond length of the interface was confirmed.The experimental results indicated that the interfacial bond property between carbon-TRC and masonry substrate was better than that of basaltTRC for the TRC used in this study.The stress transfer mechanism of interface between carbon textile and matrix was more effective when the carbon textile was treated via the surface coating and as a result,the interfacial bond property between carbon-TRC and masonry substrate was further improved.(2)On the basis of experimental investigation on the interfacial bond property,the relevant statistical analysis was further carried out via combining the collected test results.The interfacial failure modes and distribution were deeply confirmed.The influence analysis on the interfacial carrying capacity between TRC and masonry substrate was developed for the debonding and slippage failure of the interface.The calculation formula of the interfacial carrying capacity was proposed,and for design purposes,the corresponding characteristic value was further obtained based on a probabilistic method.When the slippage failure of the interface between textile and matrix occurred for the interface between TRC and masonry substrate,the interfacial fracture energy was analyzed based on the fracture mechanics method,and the corresponding calculation formula was also proposed.(3)The experimental investigation on the compressive performance of brick masonry columns confined by TRC was developed.The influences of the types and layers of textiles,the additional end confinement by FRP and the matrix strength grades of TRC on the compressive carrying capacity,deformability and energy dissipation of confined brick masonry columns were analyzed.For the different TRC-confined methods,the increased effectiveness of the compressive performance was researched.On the basis of experimental investigation,the calculation method of the compressive strength for TRC-confined masonry columns were further studied via combining the collected test results.The prediction model of the compressive strength was proposed,and for design purposes,the characteristic value of the compressive strength was further obtained based on a probabilistic method.(4)The research results of the compressive performance indicated that the fracture of textiles on the corner region occurred for TRC-confined brick masonry columns.The compressive performance can be improved when increasing the layers of textiles used by TRC,but the improved efficiency was not significant when the textile exceeded two layers.For the TRC used in this study,the brick masonry columns confined by carbonTRC had a better compressive performance compared with that of basalt-TRC.The compressive carrying capacity and energy dissipation were further improved when using the additional FRP end confinement,but the deformability of TRC-confined brick masonry columns reduced to some extent.The matrix strength grades had certain effect on the compressive strength of TRC-confined brick masonry columns,but its influence was not significant on the deformability and energy dissipation.For the compressive strength model proposed in this study,the prediction accuracy was compared with that of two existing models.The result indicated that the prediction model proposed in this study has better adaptability and generality.In addition,the characteristic value obtained can further satisfy the design requirements of compressive strength.(5)The shear performance of TRC-strengthened brick masonry walls was experimentally investigated,and the failure process and the stress transfer mechanism were analyzed via DIC tests.The influences of the types,surficial treatment methods and layers of textiles,the single-sided and double-sided TRC strengthening and the thickness of walls on the shear strength,ductility factor and energy dissipation were researched,and the increased effectiveness of the different TRC-strengthened methods was analyzed.On the basis of the experimental investigation,the study on the calculation and design method of the shear carrying capacity was further developed for TRC-strengthened brick masonry walls.The main reasons of the conservativeness for the design method proposed by ACI 549.4R were analyzed,and on this basis,the optimization of the calculation and design method was further realized.(6)The research results of the shear performance indicated that the integrality of brick masonry walls at failure can be effectively insured after TRC strengthening,and the failure mode had a ductile feature.For the different TRC-strengthened methods,the shear strength,ductility factors and energy dissipation of TRC-strengthened brick masonry walls were significantly improved compared with the walls without strengthening.The increased effectiveness of the double-sided TRC strengthening was better than that of the single-sided.For the TRC used in this study,the brick masonry walls strengthened by basalt-TRC had a poor ability to control cracks,and the increased effectiveness of the shear performance was lower than that of carbon-TRC.For the twoleaves brick masonry walls with the larger thickness,the shear performance after TRC strengthening was also significantly improved.The test results of DIC indicated that the carbon-TRC strengthened brick masonry wall had 2-3 stress transfer paths,whereas that of basalt-TRC had only one path.Compared with the method proposed by ACI549.4R,the conservativeness for the design value of TRC-strengthened brick masonry walls was effectively relieved after optimization.