Walking

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Walking Working Surfaces

• TM 650 Safety Management
• Carter J. Kerk, PhD, PE, CSP, CPE
• Industrial Engineering Department
• South Dakota School of Mines

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Reading Assignment

• Read Asfahl, Chapter 7

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Introduction

• Concerns standing, walking, climbing, working
  at elevation, falling objects
• Falls represent 20 of accidental deaths
• Slips falls are the leading cause of accidents
  and death in the home

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Tripping vs Slipping

• Trips
• Foot motion is interrupted
• Slips
• Sliding of one or both feet
• Even a trip or slip without a fall can cause
  strain to muscles, joints, low back, neck

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Tripping

• Hazards
• Irregular surfaces, protruding objects, damaged
  floors, change of surface (tile to carpet),
  cords, trash, low lighting, obstructions possibly
  as small as .25 inches
• Normal line of sight is 15 degrees below
  horizontal. You dont normally look at your feet.

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Tripping

• Controls
• Good housekeeping, proper maintenance and upkeep,
  frequent inspections, temporary cord controls or
  appropriate tape, adequate lighting, 5S
• 5S Sort (Seira), Set in Order (Seiton), Shine
  (Seiso), Standardize (Seiketsu), Sustain
  (Shitsuke)
• http//www.isixsigma.com/dictionary/5S-486.htm

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Slipping

• Coefficient of Friction
• The ratio of maximum force acting parallel to a
  contact surface that resists motion of one body
  on the other, divided by the normal force acting
  on the contact surface
• A slip occurs when the lateral force applied at
  the foot-surface interface is greater than the
  frictional resistance available

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Slipping

• Factors
• Combination of shoe and surface materials
• Gait speed walking style
• Interface contamination
• Moisture, oil, debris, wax
• Dynamic vs static differences
• Pushing, pulling, turning, accelerating, ramps

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Slipping

• Slip testers
• Possible guideline
• COF of 0.5 (controversial)
• gt0.5 is considered slip-resistant
• lt0.5 is considered slippery
• Controls
• Housekeeping, maintenance, proper design, proper
  selection of flooring materials, proper selection
  of footwear, replacement of worn surfaces and
  footwear

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Falls

• From slips, trips, stumbling, falling from one
  surface to another, or on the same surface where
  standing or walking, or from falling objects

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Physics of Falls

• Three important aspects of falls
• Displacement and motion of the body
• The impact
• The ability to withstand impact

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Displacement Motion

• How far a body moves vertically during a fall
• V (V02 2gs)1/2
• V0 the initial velocity
• g the acceleration of gravity
• If the weight of a body, W, is known, one can
  compute kinetic energy at the point where the
  body reaches a velocity, V
• KE (mv2)/2 (Wv2)/2g
• Estimate KE at any point in a fall by combining
  the above two equations

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Impact

• When one body strikes another, the two bodies
  absorb much or all of the stored energy, often by
  deformation.
• The injuries resulting from a fall are in part a
  function of the rate of deceleration, a.
• a V2 / 2s
• V the velocity at the point of impact
• s the stopping distance

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The effects of human impacts from falls.
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Preventing Falls Injuries

• Four Objectives
• Prevent people from falling
• Prevent objects from falling
• Reduce energy levels if falls do occur
• Reduce injury at impact

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References

• Brauer RL, Safety and Health for Engineers, John
  Wiley Sons, Hoboken, NJ, 2006

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HW12

• Exercises Study Questions
• 1-32, divisible by 5
• Research Exercises
• 33-34