Load Testing of Historic Cast Iron Stairs at Cape Hatteras Lighthouse

Abstract

The Cape Hatteras Lighthouse is the tallest brick structure of its kind in the United States. The national icon was closed to visitors after several pieces of the cast iron stairs, original to the structure, dislodged and fell inside the lighthouse. This finding led to the investigative efforts outlined in this paper, on the load carrying capacity of the stairs. This article summarizes the engineering effort in the condition assessment of the stairs, the review of visitor statistical data for likely load exposures during peak times, and the development of a unique load test program for the stairs of the historic structure. The load testing program was unique because of the physical constraints of the lighthouse shaft as well as the dimensions of the stair treads. In addition, the engineering team had the added objective of protecting the integrity of the national icon and performing the load test without exposing the historic stairs to an unnecessary risk of failure.