Effect of Variation of the Stay Prestressing Forces on the Seismic Response of Cable-Stayed Bridges

Abstract eng:
Due to severe damage to bridges caused by the recent strong earthquakes around the world, very high ground motion is now required in the new bridge design specifications, in addition to the relative frequent earthquake motion specifications by which old structures were designed and constructed. For that reason, in order to investigate if variation of the stay prestressing forces are important regarding the seismic response of cable-stayed bridges, two concrete bridge models were analyzed, with a very similar main span length, but with differences in their stay cable layout, deck type, deck level and stay spacing. For the variation of the cable forces, two load conditions were considered: an original load condition where the stay prestressing forces were the obtained from the static analysis under service loads, and an optimal load condition, where the stay prestressing forces were modified to an optimal value minimizing the structural displacements. Results of this investigation show that the seismic response of the bridges is not very sensitive with regard to the influence of low-to-moderate variations of the stay prestressing forces. The main differences come from the maximum vertical deflections and axial forces of the decks, as long as differences with regard to the seismic response of the towers are less sensitive.

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