**1. Introduction**

The assessment of seismic vulnerability in regions where the risk from earthquake shaking is considered moderate poses special problems in terms of establishing critical conditions for failure and the importance and urgency for taking action. Research studies sponsored at the University of Mississippi (UM) over a period of about 10 years by the Mississippi Emergency Management Agency (MEMA) and Mississippi Department of Transportation (MDOT), respectively, have been aimed at identifying the vulnerability of select critical highway bridges subject to significant ground shaking from the New Madrid Seismic Zone (NMSZ).

The historical occurrence of multiple but infrequent major seismic events in the NMSZ exceeding seismic moment of *M* 7 has been established by geophysicists and seismologists through numerous surveys of surface rupture features and paleoseismological excavations conducted throughout the region (for example, see [10, 18]). Planners in both state and federal agencies are concerned about the consequences of both physical and economic damage posed by the next major recurrence of a potentially catastrophic earthquake along the fault. The United States (US) Federal Emergency Management Agency (FEMA) sponsored a major research study [3] to investigate the multi-state regional consequences of a hypothetical event of *M* 7.7 on both buildings and bridges. The bridges in Mississippi discussed in this chapter represent critical lifelines exposed to the earthquake threat that are located along the evacua‐ tion routes and economic supply chains for communities in the northern part of the state as well as the tri-state metropolitan area of the city of Memphis, Tennessee, having population of about 1.3 million.

A myriad of uncertainties exist for both the rare but potentially catastrophic seismic events and the multiple factors affecting the response of these soil-foundation-structure systems. In the absence of ground motion records for the severe historical events in the seismic zone under

© 2013 Mullen; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Mullen; licensee InTech. This is a chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Mullen; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

consideration, a simulation based approach is adopted to highlight the salient features of both the input and response at the site. The vulnerability assessment requires that reasonable behavioral response and multiple failure limit states be examined under a range of possible ground motion intensities. While a probabilistic approach is desirable overall, a deterministic approach enables the examination of the key response characteristics and the detailed information needed to establish relative importance of different limit states including soil capacity, pile/column axial and flexural strength, and member/system instability.

The bridge seismic vulnerability studies in this chapter highlight the challenges posed by the need to balance the level of sophistication of the finite element (FE) simulation with the:


Lessons learned and discussed herein are the result of over a decade of research at UM sponsored at the multidisciplinary Center for Community Earthquake Preparedness (CCEP) and graduate level studies by a number of students supported by the Department of Civil Engineering.

**Figure 1.** Recent seismicity in NMSZ and surrounding multi-state region exposed to risk of a repeat of historic cata‐ strophic events (M7-M8); red circles give epicenters for events > M2.5 during the period, 1974-2002 [from 19]; the

FE Based Vulnerability Assessment of Highway Bridges Exposed to Moderate Seismic Hazard

http://dx.doi.org/10.5772/55334

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**Figure 2.** NBI bridge inventory in study region shown by open circles; green circles show bridges located in north Mis‐ sissippi on the major access routes for the Memphis metropolitan area, those investigated using FE based seismic vul‐ nerability analysis lie within shaded areas; red lines indicate highways on federal and state system; blue lines represent

study region is represented by the blue shaded area

major rivers to show critical water crossings
