Burgoyne Bridge Erection, ST. Catherines, ON

 

Noteworthy Project Experience

Complex global phasing, difficult geotechnical conditions, innovative girder launching, coordination/temporary support of existing services.

Project Description

The replacement bridge contains seven continuous spans with a total length of 333 meters including a 125 meter long signature arch span that spans over Twelve Mile Creek and Highway 406 in St. Catherine’s Ontario. The bridge replaces the existing 100 year old steel box truss / concrete deck structure located on the same footprint as the west deck of the new structure. The arch span consists of a single space-truss arch carrying twin trapezoidal steel box girders that flank each side of the arch and cantilever to PSS steel cable hangers through transverse steel box girder floor beams located below each arch panel point. The six approach spans, ranging from 20 meters to 44 meters in length, consist of twin steel trapezoidal box girders and divided composite concrete decks. The superstructure is supported by tall reinforced concrete piers and abutments containing deep reinforced concrete caisson foundations. The arch contains internal thrust support in the form of bow string assemblies consisting of high strength, low-relaxation multi-strand post-tensioning assemblies.

Difficult geotechnical conditions results in the need for lightweight approach fills and strict construction conditions / phasing / loads to maintain stability of the slopes during all phases of construction. At the instruction of our client (Pomerleau), HEC has developed a cost-effective alternate lightweight South Approach design consisting of cellular concrete (γ=4.66 kN/m3) infill and tied reinforced concrete retaining walls with shallow foundations. HEC has also developed cost-effective temporary retaining walls along the Stage 1 / Stage 2 line to maintain traffic first across the existing bridge, followed by the east deck of the new structure. The temporary retaining walls are designed to be temporarily tied to the east permanent retaining walls to maintain stability of the wall during cellular concrete casting and, subsequently, under traffic surcharge loading when traffic is diverted onto the east deck.

Due to geometric constraints and the close proximity of private lands on the North Approach, HEC’s scope or work is limited to the design of temporary Stage 1 / Stage 2 retaining / shoring structures and an alternate cost-effective design of the permanent retaining walls along each side of the bridge along the South Approach.

Working for Pomerleau and Structal on the project, Harbourside Engineering Consultants (HEC) current scope of work consists of the following:

  • Development of the global phasing and erection method for the structure;
  • Project construction engineering specialists;
  • Project erection engineering specialists;
  • Project demolition engineering specialists;
  • Project PSS cable specialists;
  • Detailed phasing drawings and detailed design of all temporary works, including temporary girder and arch support towers, girder launch design strengthening and temporary works, the analysis of the new structure during all phases of construction, including the placement of 175 ton cranes on the west deck to erect the arch segments;
  • Detailed design of temporary retaining and shoring structures along each approach to facilitate the phased construction procedure / to maintain two lanes of traffic throughout construction;
  • Detailed design of all cofferdam structures required to construct the new piers and abutments;
  • Advice to create an alternate floor beam to girder connection in the arch span to improve constructability and mitigate risks associated with fit-up;
  • Alternate lightweight south approach design to mitigate costs, improve schedule and minimize risk associated with the need for multiple trades being required to complete the work; and
  • Alternate cost-effective permanent retaining walls along both the north and south approaches.

As outlined in the HEC scope of work list, traffic conditions dictate that two lanes of traffic must essentially remain open during all phases of construction. To accommodate this, HEC have developed an innovative and cost-effective construction methodology for the project. In general terms, the construction methodology is as follows:

  • Complete approaches, piers and abutments for the Stage 1 / east half of bridge;
  • Construct three temporary deck support towers in the arch span, complete with deep foundations, steel towers and transfer girder assemblies to facilitate erection of the girders, casting of the decks and the transfer of two lanes of alternating traffic onto the east deck;
  • Launch the east box girders into position from the south approach to the north abutment. Special approach lifting frames were developed and designed by HEC to allow erection of the girders to take place without the need for cranes;
  • Cast the east deck and curbs, mount the barriers and waterproof and asphalt the east deck;
  • Divert traffic from the existing bridge onto the east deck and demolish the existing bridge;
  • Complete approaches, piers and abutments for the Stage 2 / west half of bridge coupling the foundation to the Stage 1 sections previously constructed;
  • Repeat girder launch and deck installation for the west deck;
  • Erect the arch support towers on top of the temporary deck support transfer girders in addition to the two intermediate towers supported from the permanent deck transverse floorbeams;
  • Using two 170 ton cranes strategically positioned on the west deck, install the arch segments on top of the arch support towers;
  • Align and weld arch segment field splices based on the best-fit as-built coordinates developed by the three dimensional HEC geometric model, taking into account thermal corrections as required;
  • Remove the temporary arch support towers
  • With the arch erection completed, install anchor assemblies and string the PSS hanger cables and permanent arch bow string assemblies. The PSS cable assemblies are fabricated to the correct as-built length based on the comprehensive HEC arch calibration model and surveys of the as-built structure;
  • Complete the transverse deck post-tensioning in the arch span in preparation for load transfer operations;
  • Undertake the first phase of load transfer operations by stressing the permanent bow string assembly, then relieving the arch tower support, followed by lowering the deck at the deck support tower locations. Repeat successive load transfer phases until the deck loads are completely supported by the free spanning arch. Total load transfer to the arches is anticipated to be completed in three cycles of the above operation;
  • Complete any final cable adjustments;
  • Remove all temporary works, dress slopes and de-mobilize.

Construction started in early 2014 with construction anticipated to be completed by the end of 2016.

Client: Pomerleau / Structal

Value: $75 M (Approximate)

Year:             2014 (Ongoing - Currently Under

Construction)

Role: Bridge and Construction Engineer, PSS

Cable Specialist