Some 35 years ago the St. Patrick Street Bridge over the Rideau River in the City of Ottawa
was replaced. It was proposed that the new bridge be an arch bridge, replacing the existing
functionally obsolete multi-span concrete arch which had been at the site since the 1920s, but
respectful of the heritage of the site and the crossing. However, in the then-prevailing climate of
bridge design, a more conventional post-tensioned concrete multi-span slab bridge was
selected for design, and it was constructed in 1975. It might be described as functional but
perhaps uninspiring.
Since then the steel box girder Hunt Club Bridge has been constructed over the Rideau River,
and the Cummings Bridge has been rehabilitated, amongst other bridge works over the river.
Similarly the Bank Street Arch Bridge and the Plaza Bridge over the Rideau Canal have been
restored. As well, in the intervening years the Rideau Canal has now been designated as a
UNESCO World Heritage Site, and is on the National Register of Historic Sites in Canada.
It is now proposed that another new bridge over the Rideau River and Rideau Canal be
constructed near the south limit of the City. The development of this project to include a
beautiful new Rideau Arch Bridge spanning the river (and the canal which at this location joins
the river) offers the opportunity of examining the significant changes which the bridge design
and engineering process has undergone since 1975. The new bridge is considered to have the
potential to be a gateway to Ottawa, and a landmark in the National Capital Region. In addition,
the new bridge design respects the fact that this is a UNESCO World Heritage Site on a
beautiful reach of the river and the canal.
Beyond that however, it is our goal to so design the bridge so that it has a strong net positive
environmental effect on the site. This can arise if the engineering design of the bridge itself can
create a bridge which offers a strong positive social and cultural benefit, not only from the
perspective of several modes of transportation but also from the intrinsic artistic character of the
bridge.
This paper follows the evolution of the changes in bridge engineering exemplified by the St.
Patrick Street Bridge of 1975, to the current artistic and environmentally-positive approach to
bridge engineering built into the proposed new Rideau Arch Bridge, which is intended to inspire
the passers-by and contribute in a beneficial way to the City of Ottawa.
