Ergonomic Job Analysis
Masonry Crew
Construction Occupational Health Project
Department of Work Environment
University of MassachusettsLowell
One University Ave.
Lowell, MA01854
prepared by:
Ted M. DesMarais
Sean McDonald
Contact Sheet
ContractorWalsh O’Connell
Contract #C15A3 Vent # 4 and Parking Garage
Office Location21 Union St. 2nd floor (617) 523-7743
Proj. ManagerBernie Doherty
Site Contacts
Steward(s)Steve Cecca
Health and SafetySteveLake and Chris Zeigler
Ergonomic Exposure Assessment
This assessment consisted of informal interviews with construction workers on site, as well as, five hours of observation by two Construction Occupational Health Project research assistants. Weight measurements were done using a 100 lb. force gauge and dimensions were determined by field measurement and extrapolation using the Drillis and Contini anthropometry model.
Description of Work Schedule
The standard 7:30 to 3:30 shift is worked. Breaks are allowed at 9:30 and at 2:30 for 15 minutes with a half-hour lunch break at noon.
Workers
The operation analyzed consisted of two masons, one apprentice, and one laborer. The two masons actually laid the block while the apprentice performed specific cuts made on a table saw. The laborer in this operation brought mortar and blocks to the work area of the masons when they were needed.
Qualitative/Quantitative Description of Work Pace
Construction work in general varies every day. On the two day analysis performed it was estimated that these masons laid between 100-200 blocks per day. They explained that on most normal operations they would lay between 200-300 blocks per day. The main cause of difference was because of the short duration of the immediate work area, the necessity for special cuts of block, and the fact that materials such as mortar had to be delivered from the floor below.
Ergonomic Job Analysis: Masons
Purpose of Operation
This operation was performed in order to enclose sections of the perimeter walls between supporting structures in a parking garage.
General Description of Process
A wall is constructed using 10-inch masonry block (15”l x 10”w x 8”h). The block is laid in layers (courses) from one end of the opening in the perimeter to the end of the opening which abuts the supporting structure of the garage. The first layer of block is set on a sill that is 29 inches from the floor. The next 4 courses progress in 8 inch increments (to a height of 37, 45, 53, etc.). These are the heights that each block must be lifted to from the floor. Mortar is placed between each layer (courses) of block in order to adhere the blocks to each other and create a seal. Mortar is also placed inside the hollow blocks in order to adhere the rebar to the block that supports the wall structure as a whole vertically. Every two layers metal wiring is inserted horizontally between the courses for added stability. I-hooks are also inserted between courses, approximately every other layer, in order to tie into the outside brick that will make up the face of the structure. The mortar is allowed to set and then a mason returns with a concave jointer and smooths the mortar between the blocks.
The mason’s materials were supplied by a laborer. The laborer used a powered walking fork lift to carry masonry trays and wheelbarrows full of cement to the masons. The cement was mixed at a mixing station by laborers on the floor below and brought up the garage ramp by forklift. The same laborer also used the powered forklift to bring pallets of 10-inch block to the work area. If the masons were not working on staging at this point, the laborers would pick up the work area or move on to another activity somewhere else on the construction site. However, if the masons were working on staging, the laborer would then load the staging with masonry blocks. This required the laborer to lift the 45 lb. block from the pallet to a height of approximately 60 inches. This task was performed until a dozen or more blocks were within reach of the working masons, at which time the laborers took a break until more materials were needed.
The apprentice mason performed several special cuts, on location at the other end of the garage, using a Clipper Supermatic electric table saw with a diamond tipped blade. The typical work required cutting a 10 inch block into halves. The apprentice then brought the altered blocks back to the masons by wheelbarrow.
An activity that was not observed was the switching of the masons’ workstation around the perimeter of the building. When the masonry blocks were built 4 courses high on the sill, reaching a height of 61 inches, the work site was left until staging could be erected. At this time the masonry crew moved to another location in the garage that had been previously equipped with staging. From this point the masons finished laying courses to the ceiling above.
Breakdown of Operation into Tasks, Activities, and Hazards
This section looks at the specific tasks and their associated activities that are involved in the process, as well as, the hazards and potential anatomical target areas.
Work Methods and Potential Hazards
Task / Activity / Hazard / Body AreaCement manipulation (masons) / Scoop cement / Awkward Posture / Back, wrist, shoulders
Apply cement / Awkward Posture / Wrist, shoulders, back
Smooth cement / Awkward Posture / Wrist
Block manipulation (masons) / Lift block / Awk.Posture/Cont. Stress / Back, wrist, shld, hands
Set block / Awk.Posture/Cont. Stress / Back, shld, wrist, hands
Level block
Adjust block
Touching Up (mason) / Sweep joints with
brush
Mold joints with / Awkward Posture / Wrist
jointer
Reinforcements (masons) / Insert rebar / Awkward Posture / Shoulders
Lay wire between
courses
Insert "I" hooks
Prepare Block
(mason apprentice) / Measures and draws
Place block under blade / Contact Stress / Hands
Material Movement / Delivers pallet of block / Posture from jerking / Feet, back, shoulders
with walking / movements of lift
powered fork lift
(laborer)
Delivers mortar / Awk.Posture from unstable load / Low back, shoulders
List of Tools and Equipment
Tool/Equipment Name / USE / User / Weightmasonry hammer / level and chip block / mason, appr. / 2 lbs.
trowel / lift, place, smooth cement / mason, appr. / 1 lb.
level / ensure no unwanted pitch / mason, appr. / 4 lbs.
wheelbarrow / transport cement / mason, laborer / xxxxx
masonry bucket / transport tools / mason, appr. / xxxxx
brush / remove loose cement / mason, appr. / 1 lb.
clippers / cut wire mesh / mason, appr. / 2.5 lbs.
measuring ruler / check proper dimensions / mason, appr. / 1 lb.
concave jointer and / press excess betw. blocks / mason, appr. / 8 oz
rats tail jointer / and smooth cement / mason, appr. / 1 lb.
walking powered forklift / transport materials / laborer / xxxxx
masonry tray / hold cement / mason, appr. / xxxxx
Personal Protective Equipment
gloves / protect hands / mason, laborer / 6 oz
eye glasses / protect eyes / mason, laborer / 6 oz
hard hat / protect head / mason, laborer / 2 lbs.
xxxxx undetermined or varied weight
Summary of Ergonomic Exposures and Causes
Body Area / Worker / Ergon. Exp. / Caused byhands and wrists / mason, laborer
mason, apprentice
mason, apprentice
laborer
mason, apprentice
laborer / ulnar deviation
frequent pron/supin, flex/ext of wrists
pinch grips with high force requirements
contact stress / block placement and mmh with pinch grip
loading trowel with mortar, placing mortar on blocks, smoothing joints with jointer
mmh of masonry blocks
mmh of masonry blocks
shoulders / mason
mason, apprentice laborer
laborer
mason, apprentice / high force requirements
high force requirements
high force requirement with arm above shoulder level
repetitive arm motions above shoulder level / precision placement of masonry blocks
mmh of masonry blocks
loading scaffolding with masonry blocks
filling masonry blocks with mortar
trunk / mason
mason, apprentice laborer
mason / high force requirement
high force requirements with considerable flexion
severe flexion / precision placement of masonry blocks
mmh of masonry blocks
loading trowel with mortar
Controls
- Construct a simple stand that the mason tray can sit on, raising it to waist height approximately 3 feet.
- Construct a ramp that will reduce the vertical distance between the floor and the point of destination of the block.
- Palletize blocks in smaller amounts. This will allow the powered forklift to place the blocks directly on the mason’s scaffolding, reducing the mmh required.
- Increase the handle span of the concave jointer and rat tail to relieve contact stress and reduce grip force requirements.
- Introduce the use of a lifting aid to reduce ulnar deviation and pinch gripping to aid the workers during mmh of the blocks.
- It was suggested that one possible aid, called a Tri Cam Chock, could be modified by placing two on the ends of a light weight steel shaft. This may facilitate its insertion and removal from the masonry block.
- This control was suggested to a small population of workers and was not received favorably. One worker responded that there are two men lifting every block and that such a control would not work. Though this statement may reflect current work policies, this procedure was rarely observed.
Send written comments to:
Construction Occupational Health Project
Department of Work Environment
University of MassachusettsLowell
College of Engineering
1 University Avenue
Lowell, MA
01854
Attn: Susan Moir, Director
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