Experimental Research And Numerical Simulation On New-Style Strengthening Technology Of Reinforced Concrete Member

Largely owing to the changes in their use functions, being out of repair and maintenance for years and occurrence of natural disasters, the engineering structures fail, in general, to cope with a certain demand of function designed previously. Accordingly, these buildings must be strengthened and transformed in order to meet with the requirement of the use functions. In resent years much research and practice work have been done on the strengthening and consolidating of these structures by the scholars both home and abroad, with great achievements obtained, of which the study of behaviors of members subjected to forces, the effect of improvement of bearing capacity and the simplicity of construction technology after the strengthening of building structures have become one of the hot problems in the engineering structure strengthening industry.Based on the existing problems in the normal strengthening methods and the behaviors of concrete structures, the author suggests a kind of method to strengthen the reinforced concrete (RC) members by using steel wire meshes wrapped outside and then sprayed with the high-strength mortar. This method is characterized by the simplicity in construction technology, and chemical organic-free gel materials and overcoming the defects of poor endurance. The testing research on RC column and beam members by means of this method has been conducted so as to obtain the effects of improvement of bearing capacity. The author further discusses the bearing behaviors, and destructive characteristics of the strengthened members and analyses the mechanism of improving bearing capacity as well as points out that the main factors affecting the strengthening effects are that the existing concrete members subjected to the passive constraints can improve the concrete strength.Willam-Warnke five-parameter model simulating concrete and mortar material, ideal elastic plastic model and linear strengthened model simulating thematerials of bar and steel wire mesh are used to establish the rational numerical simulation model.This model can be fully used to carry out the numerical simulation test of strengthened members, to reconstruct the bearing process and properties and to trace the cracking occurrence and propagation of cracks and the final destructive morphology. Accordingly, it is one of the effective methods to recognize the strengthening mechanism and effectiveness of strengthened members.The role of stress history hasn't been considered in the past strengthening testing research. The testing research is made on the bearing capacity of column of wet outside-coated steel with a certain role of stress history. The test result shows that the influence of stress level of existing RC member must be considered when the design is worked out for member strengthening. Therefore, based on the theoretical analysis, the bearing capacity calculation formula was proposed, that is, to use the integrated utilization coefficients of angle bars to reflect the influence upon the bearing capacity due to the historical levels of different stresses.Based on the analysis of main factors affecting bearing capacity of RC member strengthened with steel wire mesh wrapped outside and sprayed with high-strength mortar, the author also presents the bearing capacity calculation formula of strengthening RC members. It is found in contrast with the testing results that the testing results are in good agreement with those calculated by the formula.The research done by the author can promote the application and development of strengthening method of steel wire mesh wrapped outside and sprayed with high-strength mortar.