STRUCTURAL STEPLADDER FAILURE: ANALYSIS OF ROOT CAUSE

It is estimated that over 100,000 people each year are injured as a result of falls from ladders. Stepladders are one of the many different types of portable ladders, and are used frequently both on the job and around the home. Many times a fall from a stepladder is accompanied by a damaged ladder. In particular, one or both front side rails are often bent inward below the lowest step, and the lowest step buckled upward. This paper investigates the root cause of these types of structural failures through multiple analytical methods, including calculations, strain gage analysis, computer modeling, specialized strength and stability testing, and analysis of the user dynamics on the ladder. Results include data collected from various ladder makes (wood, aluminum, or fiberglass), sizes, and duty ratings (200 pounds, 225 pounds, 250 pounds, and 300 pounds). Additionally, the results were compared to the requirements of the existing ladder safety standards. The results demonstrate that the above described damage patterns do not occur when the ladder is upright on all four legs under normal use circumstances. Instead, the analyses conducted herein show that the damage results from the dynamic forces of the user impacting the ladder after the ladder has already substantially tipped over.