Comparative Response Evaluation of two Design Options for Tresfjordbru : Subjected to Seismic Loading

Abstract

Abstract Out of two alternative bridge designs, a cantilever bridge is chosen as a highway bridge by the owner in collaboration with a consulting company. The design decision is based on initial cost estimates and regular maintenance costs without much regard to the potential damage the bridge can sustain due to earthquakes during its economical lifespan and the repair costs. The main purpose of this thesis is a response evaluation of the two bridge designs subjected to earthquake induced ground motion. As a result of this study, advantages and dis advantages of one of the designs compared to the other from the seismic behavior and seismic point of view will be identified and documented. The concept of structural dynamics has been the main pillar of this study where principle elements are used to derive the basis of two central methods of analysis and their area of application. The practical elastic response spectrum analysis and its adequate approximate solution is the first main analysis method. The second method of analysis is the time history analysis with its exact solution. Based on the solutions by both methods of analysis and a demand capacity ratio assessment it can be concluded that none of the designs will enter ductile behavior. However, with regard to comparison of the designs it can be documented that design two is more susceptible to damage during an earthquake.