Numerical modeling of low-cycle fatique of stell structures

Low-cycle fatigue is always present in seismic conditions, thus its influence must be minimised as much as possible. Steel structures are designed to resist seismic actions in such a way that plastic behaviour is allowed in some selected parts in order to dissipate the input energy. Dissipation regions, which very often are frame beams near beam-to-column connections, are subjected to cyclic plastification and consequently to low-cycle fatigue. The goal of the project is to develop a method for numerical modelling of low-cycle fatigue of steel structures. The new method will enable accurate prediction of service life of structures subjected to the low-cycle loading and will not be based on a global deformational quantities. Our intention is to use a constitutive model where elasto-plastic response of steel materials under cyclic loading is modelled by coupling non-linear isotropic and kinematical hardening with damage. The model, previously used for the prediction of low-cycle fatigue of metal forming tools, will be modified in order to describe specific response of mild structural steels and to consider non-linear behaviour of steel structures geometrically. The model will be incorporated into general purpuse finite element envirnoment. Symbolic techniques will be applied for automatic generation of finite element code. This reduces code development efforts and enables researchers to concentrate more on fundamental problems.