Damage Evolution Analysis Of RC Beam Strenghened With Near Surface Mounted Aluminum Alloy Bar Based On DIC Technology

With the continuous advancement of the new round of urbanization in China,the existing buildings in cities are faced with the problem of renovation and repair,among which the toughening and strengthening of concrete structures and the monitoring of damage degree are very important.Near surface mounted reinforcement technology is a new and efficient reinforcement technology,which is to cut grooves on the surface of concrete structures to be reinforced,and fix reinforcement materials in the grooves with binder.Based on the static loading process of embedded reinforced concrete beams,this paper combined with non-contact Digital Image Correlation(DIC)technology to realize the full-field measurement of concrete beam deformation during the whole process of static loading.On this basis,the damage evolution law of reinforced concrete beams was studied.In this paper,high strength aluminum alloy steel 7075 were used as reinforcing material,and five high strengthed aluminum alloy reinforced concrete beams are designed and made,three test parameters of reinforcement amount,anchorage or not and anchorage form were set,the damage evolution process of reinforced beams was studied by using two-point symmetric loading method and DIC technology.The research work mainly involves the following aspects:1.DIC technology was used to collect the images of the surface damage and cracking process of the test beam during the whole loading process.Ncorr software was used to obtain the main strain cloud map of the surface of the concrete beam,the evolution of the red region in the strain nephogram is consistent with the development process of the cracks on the specimen surface Combined with the deformation and displacement field data of the beam specimen,according to the position and amplitude of the abrupt change of the horizontal displacement curve,the calculation method of the surface crack characteristics(width,quantity and position)of the reinforced concrete test beam was proposed,and the fracture development process analysis of the reinforced concrete beam with aluminum alloy bars embedded based on the strain field data was completed.2.To carry out the test result analysis,focus on the study of the characteristics of reinforced concrete test beam load,crack width and span deflection,7075 high strength aluminum alloy were analyzed embedded flexural performance of reinforced concrete beam,increase the dosage of aluminum alloy strengthening muscle can obviously improve the bearing capacity of the reinforced concrete beam,and to a certain extent,inhibit beam specimen fracture development;The deformation performance of reinforced concrete beams and ultimate bearing capacity of reinforced concrete beams can be effectively improved by using aluminum alloy reinforcement reinforced with carbon fiber cloth at the end of reinforced concrete beams.3.Based on the statistical analysis of the main strain field data of the reinforced concrete beam specimen,the two-factor curve with the change of load was obtained by introducing the two-factor curve based on the horizontal strain value,which can be used to characterize the damage evolution process of the reinforced concrete beam.After the load was further normalized,the eye results showed that with the change of the two-factor curve,P/Pmax in different numerical ranges could correspond to the damage state of the reinforced concrete beam specimen at different stages,and a characterization method for quantitative analysis of the damage accumulation of the reinforced concrete beam was proposed.