Vulnerability of Transportation Networks to Earthquakes

Abstract

Lifelines and Transportation Networks, which convey food, water, fuel, energy, information, and other materials necessary for human existence and functioning, are among the most crucial development indicators for any nation. Roadways, being element of such systems, are often fundamental infrastructures to reach places struck by strong earthquakes. During earthquakes, there are a number of ways in which these systems can be affected. Besides the ground shaking hazard that causes major damage typologies, there are other earthquake related hazards that can affect the vulnerability of the system such as landslides. Vulnerability assessment is essential to the understanding of potential impacts of seismic hazards on lifelines, infrastructures and other key components of the system. The scope of the thesis is to study the vulnerability of transportation network elements with varying geometrical characteristics and configurations during earthquakes. In the present study road on embankments, cut slopes (Trenches) and retaining walls subject to different earthquake sizes each placed under three typical soil profiles corresponding to ground types C, D and E in the Eurocode 8 are considered. Unlike the many common practices which are based on either the Pseudo-static analyses approach or the Newmark’s sliding block procedures, in the current study vulnerability in terms of fragility functions are evaluated using 2D dynamic analyses implemented in FEM-PLAXIS program. The effects from ground conditions and geometric features of the system components are evaluated and finally a relationship between the input ground motion (as PGA) and the resulting damages (as PGD) from the dynamic analyses results are formulated. Fragility curves, which the express the probability of reaching or exceeding different levels of damages for a given level of ground motion, are developed as a function of PGA unlike the standard fragility curves which are based on PGD values. The initiation is that the PGA is more commonly known parameters for earthquake than the PGD.