Pedelta has been retained by Allnorth to provide engineering services for the erection of the deck and hangers installation of the new Walterdale Bridge over the Saskatchewan River in Edmonton, Alberta.
The bridge has a 230 m deck and a single span with two 206 m thrust-arches, 54 m tall. The arches rest on massive thrust blocks supported by micro piles. The traffic deck has three lanes of northbound traffic with a separate shared-use path (SUP) on the east side and a walkway on the west side. The traffic deck is 22.4 m wide and accommodates three lanes, two lateral shoulders, barriers and a lateral sidewalk. The SUP deck consists of a tube box steel of variable width. This traffic deck is suspended by two planes of 16 hangers each spaced at 10 m at centers and the SUP girder by one plane of 16 hangers.
Pedelta was assigned to develop complete erection procedures, including drawings and structural calculations, for the traffic and pedestrian decks and hanger installation. The project includes two distinct options: preassembly of 88 m of the mid span and lifting it into final position, and stick build of the mid span in cantilever.
Two distinct options for the deck steel members’ installation procedure were analyzed. Both of them were fully engineered. The first option consists of stick build for the mid span deck. For the second option, the deck will be preassembled at final elevation, then moved, and at the end, the deck will only be hanged and the transfer of load to the hangers will be done using ballasting on the barges once the connection between mid-span bays and lateral bays is completed.
The analysis of the structure has been conducted with a three-dimensional model with RMBridge v8i Software from Bentley Systems that incorporates all the construction stages. Due to the complexity and relevance of the bridge geometry, all the structure elements were incorporated into the model in their exact three-dimensional position. RM Bridge allows for the definition of the evolution of the structure, i.e., the definition of all construction stages and associated loads (during construction and service). It also determines the effects of time-dependent variables, such as creep & shrinkage and the permanent loads. The hangers were defined with special hanger non-linear cable-elements.
The main project challenge has been to meet the very tight project tolerances: Target final geometry (tolerance specification ± 25 mm) for the arch, main deck and SUP. Target hanger forces (tolerance specification 5%), after all dead loads are applied.