FEATURED PROJECT: Transbay Transit Center Support Structure

Transbay Transit Center Support Structure
PROJECT OVERVEW

The Transbay Transit Center Project’s below grade support structure portion consisted of fabricating a series of built up girders and columns to hold the main structure above.

The built up girder columns and transfer girders hold up massive precast steel nodes that act as the base of the structural tubing of the entire above structure.

The built up transfer girders were fabricated entirely using full pen welds and a large portion welded in partially restrained positions on two or three sides. Because of the heavy welding involved, we had to manage constant temperature control to avoid warping and tearing caused by the inherent shrinkage involved with heavy welding.

When welding the precast nodes to the top flange of the transfer girders, we applied constant heating and continuous 24-hour welding and inspection to maintain “completion of weld” and avoid cracking.

Additionally, Thompson fabricated numerous Train Columns to support the heavy Transfer Girders, Nodes, and the rest of the above structure.

PROJECT HIGHLIGHTS

• Fabricated a series of built up girders and columns to hold the main structure
• Some of the full pen welds on the transfer girders were on material up to four inches thick
• Constant, precise temperature control was critical on this project
• The precast nodes weighed up to 47,000 lbs each