Date of Award

Fall 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Committee Chair

Roger Jensen

First Advisor

Daniel Autenrieth

Second Advisor

Beverly Hartline

Third Advisor

David Gilkey

Abstract

The research found on ladder safety indicated broad recognition of the hazards of using ladders, especially in the construction industries. OSHA regulations, as well as general guidance on ladder safety point to training workers on ladder usage techniques as being one of the most useful means of reducing risk of falling. However, no studies could be found directly investigating different techniques for ascending and descending ladders. In order to study and compare techniques, this project was initiated to establish a taxonomy of techniques for climbing and descending ladders Six patterns were hypothesized. A secondary purpose was to compare the patterns in terms of safety. Both purposes were addressed by observing untrained students performing ladder climbing in a laboratory environment.

The project was an observational study in which all participants performed each of four tasks. Tasks 1 and 2 involved ascending and descending an extension ladder set at a 75-degree incline. Task 3 and 4 involved ascending and descending a fixed, straight vertical ladder. The participants were occupational safety and health students and civil engineering students. The rationale was that students majoring in these two field are likely to use and possibly oversee ladder climbing activities by others during their careers.

The participants were videotaped while climbing and descending the ladders. A commercial program called Observer XT 11 was used to process the observations from the videos. The first five seconds of the ascent were included in each video, starting once both feet were off the floor. The last five seconds of the descent were included. The software was programmed to pause every half second. Once the video was paused, the 40 observations of each participant were analyzed to determine (a) how many points of contact the participant had at that moment and (b) how many points of control the participant had at that moment. A pattern was also identified from the order of limb movements used by participants as they ascended or descended the ladder.

The observed data were first analyzed to determine if the data showed a statistical association between the observed pattern and: (a) the number of points of contact, and (b) the number of points of control. For the second analysis, the Kruskal-Wallis Test was used to determine if the different patterns differed in terms of safety using as a measure the percentage of observations showing three and four points of control.

The six-pattern taxonomy developed prior to the study accounted for 68 of the 80 observations. The 12 unaccounted patterns were subjects who slid their hands up or down the rails with no noticeable pattern. This was named Pattern 7. The Chi-square test for independence indicated that the patterns were independent. The second analysis, using the Kruskal-Wallis Test to compare mean ranks, did not provide definitive conclusions that some patterns were associated with better safety performance than others.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Industrial Hygiene.

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