Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

26 Chapter Three
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FIGURE 3-2 Distribution of concrete pressure for Example 3-1.
ww.EasyEngineering.n
From Table 3-1 the value of C w
is 1.0 and from Table 3-2 the value
of C c
is 1.2. The rate of placement is between 7 and 15 ft per hr and the
placement height does not exceed 14 ft. Using Eq. (3-3) to calculate
the lateral pressure.
P m
= C w
C c
[150 + 43,400/T + 2,800R/T]
= (1.0)(1.2)[150 + 43,400/60 + 2,800(10/60)]
= 1,608 lb per sq ft
Checks on limitations on pressures calculated from Eq. (3-3):
Limited to greater than 600C w
= 600(1.0) = 600 lb per sq ft
Limited to less than P m
= wh = 150(8) = 1,200 lb per sq ft
The calculated value from Eq. (3-3) is 1,608 lb per sq ft, which is
above the limit of 600C w
. However, the calculated value 1,608 is
greater than the limit of P m
= wh = 1,200 for an 8-ft-high wall. Therefore,
the maximum design concrete lateral pressure is 1,200 lb per sq ft.
Figure 3-3 shows the lineal distribution of pressure.
Example 3-3
A concrete wall is 9 ft high, 15 in. thick, and 60 ft long. The concrete
will be placed by a pump with a capacity of 18 cu yd per hr at a temperature
of 80°F. The concrete density is 150 lb per cu yd with Type I
cement without additives or blends; therefore, C w
and C c
= 1.0.
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