Nonlinear Finite Element Analysis Of Reinforced Concrete Structures

Structura analysis plays a key role in the engineering design, especially to thoseimportant structures of high social and economic value. With the continuous developmentof engineering technology the linear strUctural analysis based on elastic theory graduallycannot reflect strucfore's real working state well, thus the new sttuctural analysis,non-linear analysis, which can reflect sttucture's working situation more realisticallydevelops. Especially, due to the recent raPid renewal in the mathematics and comPuter, thefinite element method of structUral analysis grows very quickly There is not too muchresearch on the non-linear analysis of reinfOrced concrete (RC) structure. Owning tocomplicated non-linear characteristic of concrete, there're many questionable spots in RCstructural analysis, such as constructive relationships of reinfOrcemefit and concrete,bonding of concrete and the bap and the analysis model of the combined RC structure.This paPer studies the non-linear properties of concrete, based on material non-linearity,sets uP a non-linear constructive model of RC, following the pre-researches. The programof finite element analysis (FEA) is worked out, by Which a high-rising RC frame understatic and dynamic loading is ana1yzed. The program is proved to be correct and feasible,as can be referred in the practical design. The following are primary contents and results ofthe paPer:1. Having studied strength and defOrmation of concrete, kinds of constructive modelspresellted by former scholaxs, a non-linear consttuctive model of concrete isestablished, based on three aspects of strength failure criterion, non-linear index ofstress and equivaleflt axial stress-strain relationship. Mechanic properties andnon-linear characteristic of reinforcement are also studied, and the paPer suggests theideal elasto-plastic constructive relationship.2. Applying integral finite element model of RC, stiffness matrix is derived, and thenon-linear finite element analysis prograxn of plain RC frame is worked out, by whicha high-rising RC frame is analyZed linearly and non-linearly, making a deep study onits displacemeni and intemal forces.3. The same frame is analyzed as two different spatial models (one suppose stiff floor,the other elastic fioor) under static and dynamic loading. From the results, thedifference between the response of the frame with stiff floor and elastic floor can befOund. The stiff floor structure has bigger displacement and smaller internal forces.Under seismic forces, frame with eIastic fioor has bigger vibration period, and takeson complicated modes of vibration. Due to the big vertical rotation, structure withelastic floor shows more prominently coupling vibration of bending rotating andtwisting.TherefOre, it is safer to take elastic deformation of floors into account in thepractical spatial analysis and design.