Probability Analyses For Strong Column-Weak Beam Design Of Reinforced Concrete Frames

Strong column-weak beam design,mainly based on engineering experience,is one of important ductility assurance measures of reinforced concrete frame beam.Although some scholars try to evaluate the present-day design method by probability analysis,it is obviously defective in method and concept.Based on probability and structural reliability theory, Strong column-weak beam design of reinforced concrete frame beam following the current seismic design code GB 50011-2001 is researched primarily,It aims to know the implicit probability of current strong column-weak beam design method,and give some amendment advice on strong column-weak beam design method according to analysis results.The major contents are summarized as follows:(1) Reinforced concrete frame structure reliability analysis and ductility seismic design method are stated in general.The difference of ductility design method of reinforced concrete frame structure between GBJ11 -89 and GB50011 -2001 code is compared and analyzed.(2) The probability analysis method for strong column-weak beam design of reinforced concrete frame structure is putted forward.According to the expression of bending breaking in the strong column-weak beam,the performance function,exactly reflecting strong column-weak structure of reinforced concrete frame structure,is established.the probability distribution and statistical parameters of basic variables are discussed by probabilistic computation.The probability of strong column-weak beam design is described by reliability index.(3) For residence and office building,influences of ratio of variable load nominal value to permanent load nominal valueρ₁,ratio of representative values of gravity load to earthquake action nominal valueρ₂,ratio of real bending capacity to calculated bending capacityαand bend-enlarged coefficientη_c on reliability index of reinforced concrete frame structure are systematically analyzed.(4) On the basis of calibration method,this paper evaluates the reliability level of strong column-weak beam design of reinforced concrete structure,and provides target reliability index for the first,second and third class structure respectively.Target reliability index can be control index adopts,in the process of probability analysis on strong column-weak beam design of reinforced concrete frame structure.(5) The application scope of strong column-weak beam design method is limited,by analyzing reliability index.Finally,the amendment of bend-enlarged coefficient of the first, second and third class frame structure.Based on firm theories,the probability analysis method on strong column-weak beam design of reinforced concrete frame structure is presented.lt overcomes the theory defect of current analysis method.Presented target reliability index can be defined as probability control criterion on strong column-weak beam design of frame structure.And the amendment of bend-enlarged coefficient will provide reference to revision of relevant state standard.