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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
MULTIFACETED SEISMIC EVALUATION AND RETROFIT
STUDIES OF A MAJOR VIADUCT
M. Saiidi 1 , A. Itani 1 , Q. Yang 2 , and S. Ladkany 3
'Civil Engineering Department, University of Nevada,
Reno, USA
2 Civil Engineering Department, Northern Jiaotong University,
Beijing, China
3 Civil Engineering Department, University of Nevada,
Las Vegas, USA
ABSTRACT
A major viaduct in downtown Las Vegas is slated for seismic retrofit. The structure has 22 spans and
110 columns of various shapes. The performance and seismic vulnerability of the bridge and its
adjacent rarnps are being evaluated. The focus of this article is on the effect of incoherent ground
motion on the viaduct and an explanation of a pilot study on the use of superelastic shape memory
alloy (SMA) to upgrade the seismic performance of the bridge elements. It is shown that combination
geometric incoherency, wave passage, and site characteristics effects can increase the base shears
considerably. The improvement in the capacity and ductility of concrete cubes confined by SMA rods
has pointed out the potential of this new material for application in seismic retrofit.
INTRODUCTION
Several new concepts and issues have emerged in the past few years in seismic evaluation and retrofit
of structures. The underlying principle in utilizing new concepts is to ensure a reliable, economical,
and intelligent design that makes optimal use of innovative materials and information technology tools.
Some of the new tools, while may be well developed in the arena of their origin require further
research and development before they can be adopted in civil engineering projects. It may be hard to
justify the development work for specific projects of relatively small magnitude. However, the
potential benefit of such research can be significant for large projects and hence undertaking the socalled
"high risk" studies may be warranted.
In planning the seismic retrofit of major bridges, it is inevitable that the solution will involve both
conventional and non-conventional strategies. This article presents some of the results of an on-going
study to develop retrofit plans for a major freeway viaduct in Las Vegas, Nevada. Several aspects of