Nonlinear Analysis Of Temperature Effect To Over-long RC Frame Structures

Over the years,the plane size of the over-long,over-large buildings mushroomed in order to satisfy the functional requirements of the buildings.There are a large number of over-long RC structures which are beyond the current requirements(Maximum spacing requirements for expansion joints in RC structures).In addition,the climate is greatly affected by global warming,extreme climate occurs frequently in recent years and the effect of complex temperature variation on the structure is becoming more and more serious.So the usual anti-crack structural measures can no longer meet the design requirements.At present,there exists the phenomenon that engineering practice is ahead of design theory in China,and there is no systematic theoretical calculation method.In the past,the calculation and analysis of the structural temperature effect usually assumed that the structure was elastic,so it was impossible to accurately consider the situation that the structural stiffness degradation caused by cracking and plastic development due to temperature during the use of the structure resulted in the release of part of the constraint.At the same time,the elastic calculation method is often equivalent to the steel bar without considering its part action in the structural calculation unit,which is different from the actual situation of the project.This paper conducts a nonlinear analysis study on the temperature effect of super-long RC frame structure for this reason,mainly as follows:(1)Based on the results of many researches,the research methods of temperature effect at home and abroad are analyzed.According to the nonlinear analysis of temperature effect of over long RC frame structure,the calculation method of temperature difference between steel bar and concrete is given.Meantime,it should not only consider the temperature effect but also the nonlinear effect between the temperature effect and other load combinations such as constant load and live load when the temperature effect is proposed,so as to make the evaluation of temperature effect of the structure more reasonable and accurate.(2)The temperature effect finite element method based on the theory of 3d degenerate virtual laminated element is proposed.This method can be used to set the temperature gradient by layering or block(concrete and steel)in the model solid unit to deal with the temperature gradient caused by the action of internal and external temperature difference,and the temperature gradient effect analysis does not need to introduce the assumption of flat cross section.The method can consider both material nonlinearity and geometric nonlinearity,and can simulate the steel bar according to the actual situation.The nonlinear effects of temperature cracking and plastic development on the structure will be well analysed in the application.The feasibility and reliability of the analysis method are verified by a comparative study of the temperature effect analysis of the frame structure in this paper.(3)Using 3D entity degradation virtual laminated element finite element program,based on the engineering practice,Inhomogeneous expansion(shrinkage)caused by the difference of linear expansion coefficient between rebar and concrete is considered in the calculation unit,the effects of different degrees of internal constraints caused by different reinforcement ratios on the temperature effect of beam and plate members are investigated.This can be used as a reference for the research on the influence mechanism of reinforced concrete structure when calculating the temperature effect.(4)In combination with the study,in southern China engineering example of a super-long concrete frame structure plant as the research object,the structure of the overall difference in temperature are calculated respectively and the combination of internal and external temperature difference effect(including the constant load and live load,etc.).The influence degree of temperature effect on the structure is reflected by the overall deformation and crack development distribution of the structure.The research results of this paper provide reference for the theoretical study of temperature effect and crack control of ultra-long concrete frame structures.