NDLI: Stepladder Spreader Bar Structural Integrity and the Impact on Accidents

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Michael, P. Van Bree Erick, H. Knox Kenneth, M. Smith Joseph, T. Eganhouse
Copyright Year	2009
Abstract	Ladder accidents involving stepladders usually reveal damage to the spreader bars. This paper addresses the sufficiency of the present stepladder safety standards, design and testing requirements related to spreader bars. Spreader bars are the hinge members affixed to the sides of the stepladder that facilitate folding. Post-accident observation of buckled spreader bars or detachment from the side rails is frequently suggested as the cause of a user’s fall and injury. In addition to complete detachment at an end of one or both spreaders, several different bending configurations to varying degrees have been observed during accident investigations. These include bars bent into an “S” shape, bars bowed out/in, and bars with compound bending. In order to study these various post accident spreader conditions, stepladders of different size, weight ratings (i.e. types III (200 lb.), II (225 lb.), I (250 lb.), etc.) and material (wood, aluminum and fiberglass) were instrumented with strain gages in relevant locations to monitor stresses during normal use and misuse, as well as during various load tests and during live user falls from ladders. This extensive measurement experience of multiple loading configurations empirically demonstrated that spreader bar forces were minimal both in normal use, and even some circumstances of misuse. The resulting stress does not result in disconnection or deformation. Conversely, the loading of the stepladder structure that occurs in a tip over accident was observed to be more than sufficient to cause the frequently-identified post accident spreader bar damage patterns. On ladders that meet the applicable safety standards, all post accident spreader bar damage was found to be the result of the accident and not the cause.
Starting Page	425
Ending Page	432
Page Count	8
File Format	PDF
ISBN	9780791843864
DOI	10.1115/IMECE2009-11487
e-ISBN	9780791838631
Volume Number	Volume 13: New Developments in Simulation Methods and Software for Engineering Applications; Safety Engineering, Risk Analysis and Reliability Methods; Transportation Systems
Conference Proceedings	ASME 2009 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2009-11-13
Publisher Place	Lake Buena Vista, Florida, USA
Access Restriction	Subscribed
Subject Keyword	Deformation Aluminum Wounds Strain gages Glass reinforced plastics Stress Design Hinges Rails Weight (mass) Wood products Safety Shapes Damage Accidents Testing
Content Type	Text
Resource Type	Article

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