Damage Evaluation Of Reinforced Concrete Beams

The internal micro-crack and hole of concrete are gradually damaged caused by loads, support translation, temperature change etc.,which results in damage and stiffness decline of concrete. Then members and structures are damaged and destroyed by all above reasons. Based on these , the damage index system on materials , cross-section, members and structures is established.On the basis of the static elastic-plastic analysis on simply supported beams and continuous beams by FEM, The damage of RC beams is evaluated by using the damage index system. Some quantitative suggestions are offered for seismic designing, structural repairing and reinforcing etc. Four parts on RC beams damage are mainly studied as follow.(1) A damage index of concrete based on the decline of stiffness is established. The general relation between the damage and strain of the beam cross-section is set up and the stress-strain curves of cross-section are made, through the analysis on cross-section balance. Then the cross-section damage index is defined, including ordinary concrete cross-section, prestressed concrete cross-section and unloading concrete cross-section. The concrete damage of simply supported beams can be effectively assessed by these two defining damage methods. The results show that both methods are feasible and close to reality by analyzing the whole damage process of simply supported prestressed RC beams and RC beams which have different reinforced ratios and loads.(2) The general finite element method's equations on the static elastic-plastic damage evaluation of structures are deduced by using the virtual work principle. Then a damage index system suitable to all level damage evaluation is built based on the decline of the resistant stiffness of cross-section, the member's stiffness and the whole stiffness of structures. And the system can be expressed with damage matrixes, which forms a clear and intact dendriform damage evaluated method, offering a practical basis of quantization for seismic design, seismic reinforcement and repair of buildings after earthquakes.(3) In order to solve the negative stiffness problem in structural numerical analysis, the multi-spring method is set forth and its general iterative equations are deduced. Several loading...