Casey Arborway Project, Demolition of Bridge No. B-16-367
The elevated section of Route 203, known as the Casey Overpass or Bridge No. B-16-367, carried the Arborway over Washington and South Streets in Boston’s Jamaica Plain neighborhood. The Casey Arborway Project involved removing structurally deficient Bridge No. B-16-367 and replacing it with an on-grade roadway network. SGH assisted the demolition contractor by evaluating the effects of proposed construction loading and sequencing on the overall structural stability during demolition.
SGH worked closely with the contractor to understand their proposed demolition approach. We evaluated the following and prepared demolition plans for review by the Massachusetts Department of Transportation.
- Superstructure. To avoid supporting demolition equipment on the MBTA tunnel below, SGH calculated the capacity of the existing bridge deck and stringers and determined they could support the necessary equipment. We developed a demolition plan to stage equipment on the bridge and designed mat foundations to distribute those loads to multiple stringers, as necessary. The contractor effectively operated dismantling equipment from the existing bridge.
- Post-tensioned pier caps. The contractor hoped to demolish concrete pier caps without extensive detensioning. We evaluated the feasibility of relieving stress in the post-tensioning bars by selectively demolishing concrete after removing the superstructure. SGH designed temporary shoring and prepared a demolition sequence and details, allowing the contractor to successfully accomplish this work.
- Underground pipes. SGH performed soil-structure interaction analyses to determine the overburden forces on pipes passing under and near the viaduct. We designed mat foundations to spread loads over the pipes to prevent damage.