The Effects of Scaffolding Equipment Interventions on Muscle Activation and Task Performance in

GANGAKHEDKAR, SHRUTI BHARAT. The Effects of Scaffolding Equipment Interventions on Muscle Activation and Task Performance in Frame Assembly and Disassembly Tasks. (Under the direct of Dr. David B. Kaber.) A local power utility’s injury database was analyzed to identify jobs with high injury rates for maintenance personnel. These jobs were analyzed for ergonomics-related hazards, first, using a subjective screening tool and then via a detailed quantitative analysis on the high risk jobs. This analysis revealed scaffold frame assembly tasks, including walk-board tie-down and frame tube coupling to pose high-risks. The purpose of this study was to (1) conceptualize ergonomic interventions with potential to reduce exposure to hazards for the two high-risk tasks; and (2) conduct experiments to assess the impact of the proposed interventions on muscle activation levels and task performance. The standard procedure adopted at the local utility for walk-board tie-down tasks involves use of a #9 gauge metal wire to secure boards to a scaffold frame. Pre-cut wires are looped around the walk-boards and frame, and then tightened with pliers. An evaluation of this task revealed risk factors of high force, extreme postures and repetitious movements during plier use in tightening the metal wire. To reduce the effect of these problems, plastic zip-ties were proposed. For the scaffolding coupling task, standard ratchet couplers are used to secure two tubes at an angle to each other. These couplers have a standard nut and bolt mechanism which requires high torquing through a ratcheting activity. A unique lever coupler using a “ski-boot” clamping mechanism was developed to eliminate the torque requirement and repetitious movements associated with the current technology. Two experiments were conducted, one on walk-board tie-down and the other on scaffold frame coupling with nine male scaffolders. Electromyography (EMG) was used to measure muscle activation in four forearm muscles (FCR, FCU, ECR and ECU). Average time-to-task completion (TTC) was also recorded as an indicator of risk exposure. Multivariate and univariate Analyses of Variance were conducted on each response to assess the impact of the interventions. It was expected that the muscle activity and TTC would be significantly reduced with the zip-ties and lever couplers. In the walk-board tie-down experiment, results revealed muscle activation and performance times to be positively affected when metal wire was replaced by zip-ties. Mean normalized muscle response was reduced by 33.7% for FCR, 25.5% for FCU, 14.5% for ECR and 34.7% for ECU. Related to the second hypothesis on performance time, TTC was reduced by 8.49 seconds when using the plastic zip-ties (a 33.4% reduction). In the coupling experiment, mean normalized muscle response was significantly reduced by 48.7% in FCR, 48.0% in FCU, 34.1% in ECR and 49.3% in ECU when lever couplers were used in place of conventional ratchet couplers. In conclusion, the empirical data supported the hypothesis that lever couplers were quicker than the existing ratchet couplers revealing an overall improvement of 2.5 seconds (8.3%) for securing two tubes. Results were in conformance with the initial hypothesis of reduced EMG for forearm muscles and task performance times, when the proposed interventions were compared to existing scaffolding equipment. Hence, the plastic zip-ties and lever couplers were proposed as alternate equipment to the local power utility. Future research may examine the proposed interventions in an actual field setting under a range of scaffolding work conditions to identify potential benefits. The Effects of Scaffolding Equipment Interventions on Muscle Activation and Task Performance in Frame Assembly and Disassembly Tasks by Shruti Bharat Gangakhedkar A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirement for the Degree of Master of Science Industrial Engineering Raleigh, North Carolina 2011