ST. THOMAS, ON
Dalewood Road Bridge Replacement
The City of St. Thomas commissioned a replacement for the Dalewood Road Bridge, which carries Dalewood Road across the Dalewood Reservoir and Kettle Creek.
The new bridge provides a vehicular crossing and an active transportation link for the walkway around the reservoir and creek.
The new bridge structure is a two-span, continuous extradosed bridge with integral abutments, carrying two lanes of traffic and a multi-use path. Special attention was given to structural aesthetics, including the provision of a decorative pedestrian railing, the design of a light slender structure, and the painting of the superstructure.
The substructure comprises cast-in-place concrete integral abutments founded on driven steel H-piles and two concrete-filled steel columns, each founded on a piled footing. The steel columns were designed for the effects of stream flow and ice forces. The use of integral abutments and an integral pier floor beam eliminated the need for structural bearings, which will decrease the lifetime rehabilitation costs of the bridge.
The bridge’s superstructure comprises two very slender 500-mm-deep, closed steel box girders, a series of transverse steel floor beams, and a composite cast-in-place concrete deck. The box girders are supported by steel pipe stays and pylons, which enabled the slender box girder design, thus allowing the structure to meet flood requirements without a significant grade raise of the existing road.
Each box girder was designed with a full-width top flange to improve its torsional stiffness, which allowed for erection in the absence of temporary supports. The pier floor beam was made integral with the box girders to further ease erection procedures.
PROJECT HIGHLIGHTS
CLIENT
City of St. Thomas
ARCHITECT
-
OUR ROLE(S)
Bridge Engineering Consultant
SIZE
Span: 50 m
BUDGET
$4 M
MARKET (OFFICE)
TORONTO
KEY CONSIDERATIONS
Challenge One
The anticipated flood water level was high enough that the use of a traditional below-deck girder bridge would have required a significant grade to the existing Dalewood Road. In addition, there were no drawings available for the existing structure.
During construction, the below-water geometry of the existing north abutment was found to be much larger than anticipated, such that it interfered with installation of the new H-pile foundation. It was also found to be prohibitively expensive to demolish.
Solution One
The use of steel pipe stays to support the girders allowed for the girders to be very slender, precluding a significant grade raise to the existing roadway. The new north integral abutment was used as a deep beam to span across the remaining portions of the existing north abutment, allowing the new H-piles to be shifted away from the interference with the existing abutment.
GALLERY
