Rigid Frame Bridge Seismic Assessment Of The Capacity Spectrum Method Research And Application

Bridges hold the key positions in the communication and transportation system. Once they are destroyed in earthquakes, there will be great difficulties for the emergency management and bridges restoration. Since the performance based seismic design theory was firstly proposed by an American researcher during the early of 1990's, it has been paid much attention. The performance based seismic design was treated as a momentous applied research project foe improving seismic design theory and perfecting seismic design code. Because of the complexity of this theory, the problem if the performance based seismic design has not been properly resolved by now.Based on the achievement of previous researches, this dissertation focused on the pushover analysis method, the capacity spectrum method and the seismic damage analysis. The paper proposed several improved methods and verified them by simulations. The paper also discussed the application of pushover analysis method on the seismic damage performance design. And an evaluation method of seismic capacity of bridge structures is developed based on push-over analysis.Studies presented in this thesis can be summarized as follows:1. The basic principle and procedure of pushover analysis method were studied. The recent applications and the developments of pushover analysis were concisely remarked. Several applied methods of pushover analysis to the bridge seismic performance evaluation and design were summarized.2. The lateral load patterns to a single pier model for pushover analyses at the transverse direction were emphatically discussed. For some examples and some important conclusions were drawn: by applying the first modal load of the pier, reliable results could be obtained.3. The principles of establishing the inelastic spectrum by means of force reduction factor R and ductility factorμare elaborated. The inelastic demand spectra are established according to the new code for seismic design of railway engineering and specifications of earthquake resistant design for highway engineering, and this lays the groundwork for structural inelastic analysis by applying capacity spectra method on the basis of new seismic design code. The influences on demand spectra by different R-μrelationships are also compared in this paper.4. Seismic damage models are studied from both member level and system level. The principle is discussed for determining the grades of seismic damage of structures, and the relationship is recommended between the damage index and the seismic damage grades of the structure for bridges.5. Two practical bridges are utilized for numerical illustration, one is Highway Bridge, and another is Railway Bridge. Each of them is to prove that the Push-over analysis method is holding true.