Dynamic Analysis Introduction Static vs. Dynamic Analysis • Characteristics of Earthquake Ground Motions • Dynamic Analysis Methods for Seismic Bridge Design 35 Single-Degree-of-Freedom System Equation of Motion • Characteristics of Free Vibration • Response to Earthquake Ground Motion • Response Spectra • Example of an SDOF system Multi-Degree-of-Freedom System Equation of Motion • Free Vibration and Vibration Modes • Modal Analysis and Modal Participation factor • Example of an MDOF system • MultipleSupport Excitation • Time History Analysis Rambabu Bavirisetty California Department of Transportation. | Bavirisetty R. Vinayagamoorthy M. Duan L. Dynamic Analysis. Bridge Engineering Handbook. Ed. Wai-Fah Chen and Lian Duan Boca Raton CRC Press 2000 35 Rambabu Bavirisetty California Department of Transportation Murugesu Vinayagamoorthy California Department of Transportation Lian Duan California Department of Transportation Dynamic Analysis Introduction Static vs. Dynamic Analysis Characteristics of Earthquake Ground Motions Dynamic Analysis Methods for Seismic Bridge Design Single-Degree-of-Freedom System Equation of Motion Characteristics of Free Vibration Response to Earthquake Ground Motion Response Spectra Example of an SDOF system Multi-Degree-of-Freedom System Equation of Motion Free Vibration and Vibration Modes Modal Analysis and Modal Participation factor Example of an MDOF system Multiple- Support Excitation Time History Analysis Response Spectrum Analysis Single-Mode Spectral Analysis Uniform-Load Method Multimode Spectral Analysis Multiple- Support Response Spectrum Method Inelastic Dynamic Analysis Equations of Motion Modeling Considerations Summary Introduction The primary purpose of this chapter is to present dynamic methods for analyzing bridge structures when subjected to earthquake loads. Basic concepts and assumptions used in typical dynamic analysis are presented first. Various approaches to bridge dynamics are then discussed. A few examples are presented to illustrate their practical applications. Static vs. Dynamic Analysis The main objectives of a structural analysis are to evaluate structural behavior under various loads and to provide the information necessary for design such as forces moments and deformations. Structural analysis can be classified as static or dynamic while statics deals with time-independent loading dynamics considers any load where the magnitude direction and position vary with time. Typical dynamic loads for a bridge structure include vehicular motions and wave actions such as .
