Civil Engineering Reference
In-Depth Information
TABLE 11.4
Frequency Multiplier Table (FM)
Work Duration
1h
.
1 but
2h
.
2 but
8h
Frequency
Lifts
/
min(F)
b
V
,
30
a
V 30
V
,
30
V 30
V
,
30
V 30
0.2
1.00
1.00
0.95
0.95
0.85
0.85
0.5
0.97
0.97
0.92
0.92
0.81
0.81
1
0.94
0.94
0.88
0.88
0.75
0.75
2
0.91
0.91
0.84
0.84
0.65
0.65
3
0.88
0.88
0.79
0.79
0.55
0.55
4
0.84
0.84
0.72
0.72
0.45
0.45
5
0.80
0.80
0.60
0.60
0.35
0.35
6
0.75
0.75
0.50
0.50
0.27
0.27
7
0.70
0.70
0.42
0.42
0.22
0.22
8
0.60
0.60
0.35
0.35
0.18
0.18
9
0.52
0.52
0.30
0.30
0.00
0.15
10
0.45
0.45
0.26
0.26
0.00
0.13
11
0.41
0.41
0.00
0.23
0.00
0.00
12
0.37
0.37
0.00
0.21
0.00
0.00
13
0.00
0.34
0.00
0.00
0.00
0.00
14
0.00
0.31
0.00
0.00
0.00
0.00
15
0.00
0.28
0.00
0.00
0.00
0.00
.
15
0.00
0.00
0.00
0.00
0.00
0.00
a
Values of V are in inches.
b
For lifting less frequently than once per 5 min, set F
ΒΌ
0.2 lifts
/
min.
Source: Reprinted fromNIOSH, Applications Manual for the Revised NIOSH Lifting Equation, Cincinnati, OH, Publication
No. 94-122, 1994. With permission.
assess the risk of injury during manual materials handling activities. In both models the moments
imposed upon the various joints of the body due to the object lifted are evaluated assuming that a
static posture is representative of the instantaneous loading of the body. These models then compare
the imposed moments about each joint with the static strength capacity derived from a working popu-
lation. The static strength capacity of the major articulations (assessed by this model) have been docu-
mented in a database of over 3000 workers. In this manner the proportion of the population capable of
performing a particular static exertion is predicted. In addition, the joint that limits the capacity to
perform the task can be identified via this method. These models assume that a single equivalent
muscle (internal force) supports the external moment about each joint. By considering the contribution
of the externally applied load and the internally generated single muscle equivalent, spine compression
acting on the lumbar discs is predicted. The predicted compression can then be compared to the toler-
ance limits of the vertebral endplate (Figure 11.10). An important assumption of these models is that no
significant motion occurs during the exertion since it is a static model. The implications of these assump-
tions are discussed further in Chapter 28. Figure 11.30 shows the output screen for this computer model
where the lifting posture, lifting distances, strength predictions, and spine compression are shown.
TABLE 11.5 Coupling Multiplier
Coupling Multiplier
Coupling Type
V
,
30 inches (75 cm)
V 30 inches (75 cm)
Good
1.00
1.00
Fair
0.95
1.00
Poor
0.90
0.90
Source: Reprinted from NIOSH, Application Manual for Revised NIOSH Equation,
Cincinnati, OH, Publication No. 94-122, 1994. With permission.
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