Charlestown, MA
Bunker Hill Monument Temporary Flagpole Installation
Scope/Solutions
The Bunker Hill Monument, dedicated in 1843, marks the site of the pivotal 1775 Revolutionary War battle. Throughout its history, flagpoles have been temporarily installed near the top of the 221 ft tall obelisk to commemorate significant military anniversary events. To prepare for the 250th anniversary of the battle, the United States Department of the Interior on behalf of the National Park Service sought an evaluation of the existing flagpole mounts and wanted to install new secondary supports. SGH provided structural engineering and load testing services for project.
SGH performed nondestructive proof load testing of the existing historic flagpole eyebolts, developed structural engineering calculations to determine design loads on the eyebolts, and designed secondary flagpole supports in the event one of the original eyebolts fails. Highlights of our work include:
- Documenting the existing configuration of the flagpole eyebolts and window opening geometry
- Developing an apparatus for proof load testing the four existing flagpole eye, including shear testing all eyebolts, tension testing the inner bolts, and compression testing the outer bolts
- Applying load at a slow rate with displacement monitoring devices to reach either the anticipated design wind load or a load that creates initial movement in the eyebolt
- Calculating the wind loads on the flag and the flagpole to determine the demand on the eyebolts considering a 22 ft long pole with a 10 ft by 15 ft flag
- Designing and detailing a secondary fail-safe flagpole support device
Project Summary
2025
Key team members
