Project Description

The Bonnie Road Underpass Bridge is a three-span continuous six (6) steel plate girder with composite concrete deck bridge with a total length of 42.07m (12.78m-18.5m-10.78m) that spans over Highway 101 in Meteghan, NS. The four (4) southernmost girders in the center span were struck and significantly damaged by an excavator bucket on the flatbed of a truck travelling northbound at highway speeds. The damage on the girders beyond repair extended beyond the east pier and into the east side span. In addition, several of the intermediate steel diaphragms were also damaged beyond repair.

Harbourside Engineering Consultants (HEC) were sole sourced by NSTIR to provide emergency services with respect to the repair of the bridge. HEC’s scope of work included the determination of the extents of repair, demolition design and phasing, detailed design of new bridge components as well as erection phasing. The project manager/lead designer for the project was Robbie Fraser, P.Eng, while Wade Pottie, P.Eng., completed the demolition and erection phasing.

Methodology

HEC developed a superstructure replacement scheme that minimized the amount of construction time and costs. The center span girders along with tributary deck were removed one by one (the girders and deck were cut short of the piers to maintain support for the side spans). A transverse distributor beam (designed by HEC) was then installed on the east side span to transversely distribute loads as a 2m section of each girder adjacent to the east pier was removed and replaced one at a time with new girder segments via new bolted field splices.
HEC developed an innovative step by step, from the time the bridge was originally constructed to the final condition after all repairs, stiffness analysis of all of the existing superstructure components to determine the final condition bridge vertical profile and to properly camber the new girder segments ensuring proper field fit-up.