Research On Seismic Damage Model Of Reinforced Concrete Structure

It is reasonable to introduce damage variable to describe the structural deterioration of internal mechanical characters quantificationally due to different kinds of external load, because damage growing character caused by micro-crack in concrete is prominent. The irreversible deformation in concrete material is different from that in metal material. The former is caused by the internal micro-crack and the interfacial crack which can not closes when external load is released and the latter is mainly caused by the slip of crystal lattice in metal material. So it is necessary to solve the problem of concrete damage by means of the basic theory of damage mechanics. Today, research of concrete damage is widely carried out in case of tension and compression. Yet it is now impossible to analysis structural behaviors nonlinearly in the level of using the constitutive equations including damage growing, because it is very complicated especially in case of seismic cyclic loading. In the level of structural member's damage analysis, usually the dynamic analysis method including no damage growing is used to get the dynamic result of force and displacement time-history. Then damage expression is built using dynamic results to calculate the damage indices of structural member.In case of damage evaluation of structural members, emphasis is placed on proposing a reasonable damage evaluating expression to actually describe the mechanism of seismic structural damage and the degree of structural damage. Investigators all over the world have proposed different types of damage models according to different purposes and different types of structures. Most of these models are based on the form of Park model which is composed by the maximum displacement and accumulated hysteretic energy. Park's model has been widely accepted because it reflects that damage is caused by large displacement amplitude and low cyclic effect of seismic load to some extent. It should be notified that Park's model is not applicable very wall in all kinds of loading manners and hysteretic energy can not reflect plastic accumulated damage completely.This paper proposes a new type of damage model on the basis of analyzing the existing damage parameters and damage models. The model is expressed in form of combination of degrading stiffness corresponding to maximum displacement and accumulated plastic deformation. This paper gives the combining parameters by means of experiment results carried out on compression-bending testing specimen. Finally, dynamic analysis of two frames designed according to aseismatic code is carried out. Then damage indices of every members and every floor are calculated using the dynamic results mentioned above according to Park's model and the model proposed in this paper. The comparison of damage results according two models and comparison between damage indices of structural responses indicate the feasibility of using the model proposed in this paper to evaluate the aseismatic ability of structure. The damage results also indicate the validity of seismic design code in which capability design method is proposed.