HWY 400NB Over HWY 407
The Highway 400NB structure is a third level, post tensioned, 210m long concrete bridge carrying traffic over the mainline Hwy 407 and associated ramps. The disc bearings at the piers of the existing structure were failing and required replacement. Brown & Company Engineering Ltd. was retained to develop a jacking procedure which would allow the replacement of these bearings. The existing pier columns were approximately 13m tall and their footings were founded at an elevation significantly below grade. Jacking the structure conventionally from the top of the footings was not a practical solution at this site because of the large quantities of excavation required and the proximity to adjacent roadways. Bent plate steel collars designed to be clamped onto the existing concrete pier columns using post-tensioning were used to develop the friction required to support the loads from the superstructure above. 36-250 ton jacks placed on heavy steel jacking frames supported from the collars were used to lift the existing structure at each pier. The existing structure was lifted approximately 25mm at each pier and new bearings were successfully installed.