Gartner Steel and Glass GmbH
Josef Gartner USA
Diamond and Schmitt Architects Inc.
Carruthers & Wallace Ltd.
St. Michael's Hospital
Since March 2011, a glass pedestrian bridge with a length of 30 m connects the St. Michael hospital with the new research center Li Ka Shing Knowledge Institute. The supporting structure consists of several oval steel rings which are twisted together. The bridge with a section height of 4.60 m and a width of 3.80 m was designed by Diamond and Schmitt Architects Inc. from Toronto.
As people in Toronto are mainly using the PATH system, an underground system of pedestrian paths, extending over a length of 28 km, the town could be persuaded to grant the permit only by architectural originality. Lightness of the bridge is reached by curved and thermally prestressed panes of insulated glass as well as curved pipes crossing each other, all together forming the supporting structure. Thus, the construction appears differently each time you see it from another perspective.
The bridge was designed as a statically determinate framework because of different building movements and the requirement that introducing major forces into the building structure is not allowed. The fixed point, and thus the transfer of horizontal forces, was put to the side of the old building.
The cross‑section of the bridge is elliptic. The supporting tube is formed by a large number of circular, parallel lying pipes intersecting circular pipes which are lying parallel in the opposite direction.
Engineers were able to design the bridge according to DIN 18800 as it was agreed with the local test engineer. Loading, however, was determined and taken into account in accordance with local standards.
The bridge was calculated non-linearly as a 3D model in RSTAB. As the complete construction is welded, an equivalent model was used to determine the effective stiffnesses of nodes for the analysis of deformations. Then, nodal stiffnesses were built as releases into the RSTAB model.
Furthermore, the deformation and stress design ratio of the total structure were determined. Finally, the most critical welding nodes were designed in RFEM using the analyzed internal forces.