Joint Movement Models for Angus L. Macdonald Suspension Bridge

Abstract

The Angus L. Macdonald (ALM) Suspension Bridge spans the Halifax Harbour linking the Halifax Peninsula with Dartmouth, Nova Scotia. The ALM was first opened in 1955 and currently accommodates approximately 50,000 crossings on a typical workday. As with any aging infrastructure the need for maintenance and rehabilitation exists, which requires adequate engineering knowledge of the structure. This study will investigate the expansion joint movement at the main tower locations of the bridge. Halifax Harbour Bridges (HHB) wishes to understand the range of the expansion joint movement and thereby minimize the cost of future joints. There is uncertainty as to whether the Canadian Highway Bridge Design Code (CHBDC CAN/CSA S6-06) over estimates the required range of movement of the expansion joints for long span structures. In late June of 2012, a field-monitoring program was developed to monitor the joint movement. The deck at each tower of the ALM was instrumented with displacement sensors to measure and record longitudinal movement of the main and side spans with respect to the main towers. Weather conditions were also recorded by a weather station located at the midpoint of the bridge. In order to better understand the actual in-service movement ranges, numerical models were developed to characterize movements at the expansion joint locations for variations in thermal, wind, and traffic loads. Analysis of the collected monitoring data was completed to identify correlations between movement and different loading variations. Thermal variations were found to have the largest effect on expansion joint movement. Wind was also found to have a significant effect on expansion joint movement while traffic loads were found to have the least impact on movement. Extreme environmental conditions were fed into the numerical models to determine extreme movement ranges for thermal, wind, and traffic loads.