Research On Several Problems Of Structure Reliability Of Reinforced Concrete Structure

The reinforced concrete structure is widespread in the field of civil engineering, because it has so many advantages. But it is not to say that the reinforced concrete structure is perfect structure. It has been one century from beginning of application for reinforced concrete. Many structures failed for various reasons, so that the function can not be completed. In recent years, the reliability of reinforced concrete structre has becomed a hot issue. The reinforced concrete structure reliability consists of three parts:durability, safety and serviceability. Formerly, the safety of the RC structure has been paid more attention. But the study on the serviceability and durability of RC structure have lagged behind the requirements of engieering practice. It needs much attention.Most of the models treat structure analysis from a deterministic point of view. In these models, the load and material parameters are deterministic. However, the geometric size, the working load, the material property and model of calculation are effected by several factors. In order to have a more accurate prediction of the reliability of the reinforced concrete structure, the geometric size, the working load, the material property and model of calculation should be treated as random variables.The reliability of serviceability limit states of RC structre and the strong beam weak column relaibility of RC structre and reliability of CFRP strengthened reinforced concrete beams were discussed in this paper by methodology of reliability and analysis of probability. The main creative contents includes as following:1. To overcome shortcomings of large amount of computational efforts and long computation time existing in Monte Carlo simulaiton for system reliability analysis, an improved method was proposed in the light of curve fitting. Reliability problem was reformed by depending on a optimal parameter, the failure probability was treated as a function of this paramter by exploiting the regularity of it and fitting the relaibility function by Levenberg-Marquardt method. A ten-bar truss structure numerical example was given to proved the feasibility of the proposed method. Result indicates that the proposed method has high computational accuracy with less computational efforts and computation time, providing an effective way to analyze reliability of large complex structures. 2. Uncertainty of calculation, geometric size and concrete strength were considered as random variables, seismic concept design issued by the national Code for Seismic Design of Buildings (GB50011—2010) were discussed. The strong beam weak column relaibility of RC structre was analysed by enhanced Monte Carlo simulation in the light of curve fitting. Influence of moment augment factor of column issued by the national Code for Seismic Design of Buildings on strong beam weak column relaibility were discussed. Result indicates that new moment augment factor of column improve the strong beam weak column relaibility of reinforced concrete structure. Influence of moment augment factor column on building cost were discussed by computer design software Guang Sha CAD. Result indicates that the increase of cost is very small.3. According to the national standard "Code for Design of Concrete Structure", the reliability index for the structural members of reinforced concrete have not been given, which are controlled by serviceability limit states. A methodological framework was proposed, which made use of fuzzy invalidation rule for reliability analysis of reinforced concrete members. Firstly, A membership function was chosen. Secondly, A equivalent function was established to deal with the fuzzy reliability of concrete structure by traditional JC method. Finally, the fuzzy reliability index of transverse crack of reinforced concrete structure was obtained.4. In recent years, study on the reliability analysis of strengthened structure have lagged behind the design and construction of structures. The fuzzy reliability analysis model was derived based on structural reliability theory. Geometric size, material property and uncertainty of calculation were considered as random variables, mean value and normal deviation of each random variable in performance function were determined. The reliability of CFRP strengthened RC beams were discussed by fuzzy mathematics and fuzzy reliability thorey. Result indicates that the fuzzy reliability index of CFRP strengthened RC beams were obtained, which decreases compare with the traditional reliability analysis method. Numerical results show that the fuzzy reliability analysis of CFRP strengthened RC beams provide more safety than traditional analysis does.