| Reinforced concrete frame beam under load, due to the material of inelasticdeformation, the appearance and development of cracks, the stiffness of each sectionchanges at every loading stage. The internal force change caused by the stiffness changewith the load, is commonly known as plastic internal force redistribution of the reinforcedconcrete frame beam. There are many calculation methods on theory of plasticity andbending moment modulation method is the most widely used. In the moment modulationmethod, the value of plastic bending moment is based on the moment obtained by elasticanalysis method, through multiplying the bending moment modulation coefficient toadjust for the moment.Five parameters are chosen to analyse the reasonable value of reinforced concreteframe beam in this article. They are beam section height, concrete strength grade, rebarstrength grade, reinforcement ratio, the ratio of live load and dead load. This paperestablished a series of different beam depth, different strength grade of concrete and rebar,two spans and single layer plane frame model. Firstly, calculating the reinforcement ofbeam section with different bending moment modulation coefficient, using PKPMsoftware. Secondly, carrying on the nonlinear finite element analysis by using ANSYSfinite element software. Finally, determining the reasonable value of bending momentmodulation coefficient, based on the crack width and relative compressive zone height ofthe cross section, middle span deflection.Through the study, it is found that when the reasonable value of the amplitudemodulation coefficient ranges from0.8~0.9. In these five parameters, the beam sectionheight, the strength grade of rebar, reinforcement ratio, live load and dead load ratio havegreat impact on the value of bending moment modulation coefficient, the strength grade ofconcrete has less impact on the value of bending moment modulation coeffcient. |
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