Kittery, ME

Portsmouth Navy Yard, Modular Submarine Enclosure


The Portsmouth Naval Shipyard owns and maintains a temporary steel modular-enclosure system to protect submarines during overhaul, repair, and modernization operations. While a contractor was repairing the modules in a nearby staging area, strong winds knocked over two wall stacks, damaging and distorting a stair stack and five wall modules. The contractor engaged SGH to assess the damage and design repairs to restore the damaged modules to their original condition.

The enclosure system comprises a total of nineteen wall stacks, approximately 49 ft tall, 8 ft wide, and 48 ft long, installed around the perimeter of the submarine. Each stack comprises up to five bolted modules. The enclosure system also includes six monolithic stair stacks and additional roof modules supported by wall and stair stacks.

Highlights of our work include the following:

  • Developed acceptance criteria for the module structures, considering member straightness, overall module straightness, and alignment of stacked modules
  • Performed a visual and hands-on condition assessment to document and quantify damage
  • Developed a sampling program for inspecting welded structural joints in each damaged module
  • Coordinated a precision survey of damaged modules
  • Created three-dimensional models of each damaged module using survey data and identified members requiring repair
  • Prepared repair drawings, addressing localized damage to members and global distortion of the modules
  • Prepared a Structural Tests and Inspections Plan and assisted the contractor during repair operations

Project Summary



Completion Date
Repair & Rehabilitation
Structures | Advanced Analysis | Applied Science & Research
Science & Defense
Specialized Capabilities
Repair & Strengthening | Failure Analysis | Materials Science

Key team members

Aaron Lewis
Aaron Lewis
Structural Engineering Region Head, East