Shubenacadie River Bridge Overload Analysis, NS


Project Description

Harbourside Engineering Consultants (HEC) was hired by Nova Scotia Transportation Infrastructure Renewal (NSTIR) to complete an inspection and overload analysis of the Shubenacadie River Bridge, located on Highway 102, near the village of Shubenacadie, NS. The purpose of the study was to assess the capacity of the structure to support Nacelle generator units carried by truck and trailer (126 Tonnes total) transported from Halifax, NS to the New Brunswick border. The Shubenacadie River Bridge consisted of two structures (north & southbound), each comprised of a 5-span twin steel box girder superstructure with a cast-in-place reinforced concrete deck supported by piled cast-in-place concrete abutments (2) and piers (3). Previous inspections completed indicated that the Truro (north) bound structure was in the better condition of the two structures and for this reason was chosen to support the transporter vehicle.

The following three requests were put forward by NSTIR to complete the assessment of the northbound structure:

  • NSTIR Request #1: Determine if the proposed truck loading provided (transporter vehicle – see figure 1), can cross the northbound structure in its condition at the time of transport.
  • NSTIR Request #2: Determine the allowable spread between the front section (front 6 - 96.5 kN loadings) of the transport trailer and the rear section (rear 6 - 96.5 kN loadings) of the transporter vehicle provided.
  • NSTIR Request #3: Determine the maximum acceptable scale factor for the axel weights of the transporter vehicle in the geometry provided.

The visual review of the structure was conducted by HEC in Nov 2012 to confirm the condition and overall geometry of the structure. Utilizing the original structural drawings, the structural analysis was completed in accordance with CHBDC CAN/CSA S6-06 (S6) Section 14 Evaluation. Design live loadings considered were as provided by NSTIR.

The results of the analysis indicated that the capacity of the existing southbound super-structure was sufficient for the proposed Nacelle Truck and for the following modifications to the Nacelle truck requested by NSTIR:

  • Request #1: The structure was deemed to have sufficient capacity to support the transporter vehicle loads indicated by NSTIR providing a number of conditions were followed including low, constant speeds and a specific transverse positioning of the transporter during the crossing;
  • Request #2: The minimum allowable spread between the “front” and “rear” sections of the transporter vehicle was 8.0m;
  • Request #3: The maximum allowable increase to the service axel loads was an additional 25\\% (factored increase of 1.25), 98.1kN for the steer (front) wheels and 120.6kN for all remaining axels.

Permits for shipments of generators were open from June of 2012 until the installation of the replacement structure which began in the summer of 2014.

Client: Nova Scotia Transportation Infrastructure Renewal

Year: 2012

Role: Overload Transport Inspection and Analysis