Selection of optimum joint gap size in bridges with seat-type abutments based on life-cycle-cost criteria

Abstract

Traditional seismic design of highway bridges does not include the gap size of the joint between the deck and the abutment (in either direction of the bridge) as a design parameter. Modern seismic codes, such as Eurocode 8 – Part 2, simply provide recommendations for the end joint gap size related to the degree of seismic damage accepted for the abutment backwall under the design seismic action. Also, in line with other codes, the Eurocode does not include any optimization criteria; all verifications aim at not exceeding the adopted limit states, primarily related to the safety of the bridge. A new methodology is proposed herein, which allows for the optimum selection of end-joint gap sizes in the longitudinal and the transverse direction based on the minimization of the anticipated life-cycle cost of the bridge. The proposed methodology is applied to a typical overpass, and the results show that the optimum gap size may significantly reduce the expected life-cycle cost. Finally, results from the proposed methodology are briefly compared with those from a simpler, safety-factor based, methodology previously developed by the authors for the selection of optimum joint gap sizes.