Part II : Lifelines. Chapter 7 : Highways and railroads

ABSTRACT

Transportation systems such as highways and railroads are a diverse collection of structural, mechanical and electrical components which individually play a vital role in modern society. Until recently, their seismic vulnerability was largely ignored. But damage sustained by highways and bridges in the Loma Prieta, Costa Rica and Philippine earthquakes over the last three years has heightened awareness concerning their fragility and the potential for major economic losses should they fail. Although the state-of-the-art is generally immature, seismic bridge specifications are well developed and a set of performance criteria (based on acceptable damage) are available for highway bridges. Other components such as tunnels, retaining structures, slopes and pavements are not however covered by these specifications and except for some major projects, are not designed for seismic loads, even in high risk zones. Further, there are no accepted methods for making a vulnerability assessment of an entire, or even a partial, highway or railroad system. Thus the issues of redundancy and consequences of closure are not rationally considered when establishing design criteria for new systems or evaluating existing networks. Much can be done to implement existing knowledge in order to improve the state of practice and some recommendations are made in this monograph in this regard. Recommendations are also made for advancing the state-of-the-art, for developing new knowledge, and for ensuring that this knowledge addresses national needs.(AU)