Performance Based Seismic Research And Damage Assessment Of Reinforced Concrete Structures

The damage caused by earthquakes at home and abroad indicates that engineering structures will go through enormous nonlinear deformations and even collapse under medium or strong earthquakes. Huge economic loss and personnel injuries or deaths have been created. Because reinforced concrete (R.C.) structures are widely used in our country, the study of this kind of structure from cracking and yielding to collapse will be of great importance in theory and of practical values. In recent years, performance-based seismic design theory is recognized step by step. The study of this has now become the present hot spot of earthquake engineering. Combining the theory with experiments, this text deals with the study of performance based seismic theory and method as well as damage assessment to R.C structures by the means of nonlinear seismic response of structures. The main content is as follows.Based on the existing nonlinear dynamic analysis of R.C. structures at home and abroad, a kind of element model with the distributed flexibility is put forward, the flexibility coefficients and the stiffness coefficients of element are derived and the stiffness matrix of element with the rigid zones is established. The skeleton curve of bending moment-curvature of R.C. sections can be determined by means of the fiber model method. The stiffness degradation and strength degradation as well as pinching owing to the opening and closing of cracks and steel slipping of hysteretic curve are reflected through three parameters. Following the different level from section to member and from member to structure, the theory of nonlinear seismic response analysis of R.C. structures is established with pseudo three dimensional mechanical model.Based on the tentative study of hysteretic performance and computer simulation of R.C. columns with non rectangular sections, pseudo dynamic test of a model structure for the frame-shear wall structure of main factory building in a big heat-power plants is carried out under El-Centro earthquake wave. The cracking process, yielding sequence, energy consuming capacity, stiffness degradation, bearing capacity and the hysteresis etc. of the model structure is studied. Damage mechanism and weak points of structure under earthquakes are dealt with.The nonlinear seismic response analysis of the model structures and a R.C. frame-shear wall prototype structure of the main factory building in a big heat-power plant are made on the basis oftentative research. The results of test confirm the nonlinear seismic response analysis method put forward in the text. The seismic performance of this kind of structures will lay the foundation for the seismic design of this kind of structures and further research.With performance-based seismic design, nonlinear static push over analysis of structures is made for the horizontal distributed force influenced by high modes in the text. The internal force, deformation and position of plastic hinge in every phase for R.C. structures are analyzed. The weak points and damage pattern of structures can be easily found by using this method. Base shear and top displacement curve is also derived. By using capacity spectrum method and improved capacity spectrum method, the top displacement of structures is calculated and then the displacement-based seismic assessment of R.C. model structure and frame structure is made by push over analysis.The damage assessment of structures is based on the earthquake damage criteria and damage model. The author in the text, through the existing description of earthquake damage criteria and damage model, believes that the actual earthquake damage can be showed by the dual damage criteria on the basis of deformation and energy. The author also puts forward improved Park&Ang. damage model according to collapse limit state equation. Based on nonlinear seismic analysis of structures, the damage indice of elements, story level and whole structure are calculated separately according to Park & Ang. damage model. Finally seismic damage assessment of R.C...