Fatigue performance of modular expansion joints for bridges

Abstract

This paper presents results of an experimental investigation on the fatigue performance of the welded multiple support bar modular bridge expansion joint (MBEJ) used for the recent Jacques Cartier Bridge rehabilitation in Montreal. Three identical subassemblies of the modular joint system were tested in fatigue. Both vertical and horizontal load ranges were applied to the test specimen simultaneously in the following proportions: (i) vertical load range = ΔPv and (ii) horizontal load range = 0.2ΔPv. Different loading ranges were applied to each specimen giving a sufficient number of points to define the experimental fatigue stress range versus the number of cycles (S–N) curve. The number of cycles varied between 567 900 and 3 600 000, while the calculated stress range within the welded connection details varied between 81.4 and 166.7 MPa. Static calibration tests were performed prior to the fatigue testing of each specimen. These calibration tests confirmed the validity of the structural three-dimensional analytical models and also established the repeatability of the experimental data, in conformity with the requirements of the NCHRP-402 report. Fatigue cracks of the same type as those reported by the NCHRP-402 report were observed within the welded connection detail. No fatigue cracks were observed elsewhere. The experimental fatigue curve of the welded connection showed that the fatigue resistance of the welded MBEJ is compatible with category C and C' details, as defined by the AASHTO LRFD 1998 bridge design code. This paper is very useful, as it demonstrates the applicability of the complex requirements of the NCHRP-402 report. These requirements are increasingly gaining wide acceptance among bridge engineers and bridge owners.Key words: modular expansion joint, bridge, deck, test, fatigue, stress range, cycles.