The Second-order Effect And Effective Length Of Reinforced Concrete Column In Single-story Mill Bent

Second-order effect is referred to the additional internal force of the structural members and bars that have interbedded displacement and deflection. In the design of frame structure,frame-shearwall structure,frame-corewall structure,shearwall structure and so on, second-order effect should be considered. Second-order effect may commonly classified as this, the additional effect of members and bars in structures aroused by vertical load of sway structures, commonly called P-Δ effect, and additional effect aroused by axial force of axial forced bar of deflection, commonly called P-δ effect.By experiment and theory analysis, we have comprehensive understand and practical calculate methods for frame structures. In this paper, we first system expatiate the second-order effect law and practical calculate method of standard column,sway frame column,nonsway frame column and complex structure. And then, combined with the code for design of concrete structures, particular explain the three methods of consider second-order effect in the code. The three method is eccebtricity magnifier method,elastic second analysis with stiffness reduction method and floor magnifier method. And point out the advancements and problems of considering second-order effect in the code.Then, the paper discusses the second-order effect of bent column. We first introduce the background of the effective length of bent column of the code, and point out the exist problems. In this paper, through general second-order analysis of reinforced concrete column in single-story mill bent by nonlinear finite element program, we can validate the effective length of bent column in the code is reasonable or not. By further improve and correct of static finite element technique of bars and members of structures, in purpose of employing this analysis method in the computer simulation of second-order effect. In this paper, we take the single-story and single-span bent as analysis object, do elastic analysis by using ADINA program, and find the most disadvantage load combination, and do nonlinear second analysis by using nonlinear finite element program, and calculate a serial of model examples. Through these examples, we can conclude the second-order effect law of bent column, and deduce the eccebtricity magnifier of bent column, and then ascertain reasonable effective length of bent column.Through the study of this paper, we hope to have general acquaintanceship of the second-order effect law of bent column, and check the effective length of bent column in the code for design of concrete structures.