Structural Evaluation Based On Elastic Deformation Energy Released Due To Damage

The seismic performance of HRB400 reinforced high-strength concrete (High-strength RC)columns was studied by testing four high-strength RC columns under low cyclic reversed loading .The main failure patterns, hysteretic curves and skeleton curves of columns were studied. The strength and longitudinal reinforcement ratio of high-strength concrete were taken into consideration, which influence on the hysteretic characteristics, regularization of skeleton curve, stiffness and strength degradation, ductile behavior, and ability of energy dissipation were analyzed.The result of previous test of HRB400 high-strength reinforcement concrete columns was analyzed, parameters of the damage model was fixed. Considering the failure phenomena in the experiment, failure parameters matching to different damage grades were given.Unloading rigidity coefficientξand energy correlation coefficientγto describe unloading rigidity of concrete structure were presented and proved by analyzing experimental data. Based on analyzing RC hysteretic model,methods of linear-type and cured-type unloading restoring force model of concrete structure and the current studies of unloading rigidity equal to secant rigidity on yielding, it established the expression of elastic deformation energy due to damage during unloading process. The steel RC columns experiment proved that while introducing new coefficientsξandγ, it can be better describesd and evaluatesd the dynamic unloading phenomenon of concrete structure, and improve the deficiency of no considered the interacting effects between unloading rigidity and motion state in elasto-plastic time-history analysis of concrete structure, better describe the whole process of elasto-plastic analysis of concrete structure.By analyzing the data of the hysteretic curve and ductility coefficient gained from four SRC columns, structural damage and ductility evaluating model were proved. The method to determine elastic deformation energy release value due to damage base on degrading trillinear model, the functions and related indexes of energy relesae value correspond to hysteretic damage model were established to estimate the system's damage and deformability. were proved by analyzing experimental data. The view that energy release value is the key factor in charactering the concrete strength was suggested. Energy release value, damage indexes and ductility coefficients were determined by calculating experimental data. Combined with the observed phenomenon of failure mode in the test, the results of calculating damage index were in good agreement with the experimental data of failure model; meanwhile the numerical simulation results of four SRC columns had good consistency with the practical ductility coefficients. The new models based on energy relesae value due to damage were preferable for elasto-plastic time-history analysis of concrete structure.Finally, as an example, a six-story HRB400 high-strength RC moment- -resisting frame structure was studied. Dynamic analysis and structure damage according to aseismatic code was carrried out by IDARC2D program. Damage indices of every members and every floor were calculated using the dynamic results according modified Park's model propsed above and IDARC2D.The comparison of damage results according two models and comparison between damage indices of structural response indicate the feasibility of using the model suggested to evaluate the aseismatic ability of High strength structure. This model can better describe high-strength reinforcement structure.