Manual bar bending - An occupational hazard for construction workers in developing nations

Bar bending is the process of bending reinforcement bars to required angles in civil and construction engineering. Manual bar bending involves strenuous physical activity, which is usually performed in a poor ergonomic environment at a construction worksite. This could lead to chronic musculoskeletal disorders such as low back pain among bar benders. The aim of this study is to assess the ergonomics of manual bar bending and thereby develop a customized optimal workplace for bar bending. Biomechanical analysis was done using a three-dimensional Schultz-Andersson model to determine the influence of the diameter of the bar on the compressive force (F-c) at L-5/S-1. The effect of table height, grip arm distance, and back bend angle on F-c were also evaluated. F-c decreased up to 53%, with an increase of table height by 400 mm, and up to 41%, with an increase of grip arm distance by 500 mm; however it increased with back bend angle. F-c was higher than the NIOSH safety limit of (3.4 kN) in all cases except when bending 8 mm bars. A quick field reference for optimal table height and grip arm distance was prepared based on subjects' anthropometry and diameter, using Nash bargaining principles.