and 22.6 m from upstream face. As shown in this figure, the maximum RCC
upstream surface, the temperature will be very high at the beginning due to large heat
12
generated from heat of hydration of the CVC at the facing, which then decreases
rapidly due to effect of ambient condition. The results demonstrate that the
temperature at the surface is affected by the environmental conditions and the
temperature in the center of the dam is essentially unaffected by the ambient air
temperature. Figure 13 shows the evolution of cross valley stress (z-direction) for the
same points in Figure 12 with constant modulus of elasticity. The point near the
upstream face shows a more rapid return to a lower level stress condition. Moreover,
the zero stress point does not appear in this figure, it would appears with time when
the temperature of node decreases to the placement temperature (20
o
C). Figure 14
presents the vertical stress distribution (in the x-direction) at the center of the dam at
different period of the dam construction. It can be seen that after two years the
temperature of RCC inside the dam body decreased causing an increase in the tensile
stresses and decrease in the compressive stresses. The tensile stresses at the top
surface of the dam body are due to exposing the outer surface to the ambient
condition. Also, the tensile stresses were developed near the foundation at the end of
construction of the dam, due to the difference in stiffness between the foundation and
the young RCC and the heat transfer between the RCC face and the foundation.
Figures 15 and 16 show 2D temperature contours within the dam body at the
end of casting and after 2 years, respectively. The maximum temperature is about 31.7
o
C at the core of the dam at end of casting and 28
o
C after 2 years which is higher than
the ambient temperature after 2 years.
A comparison between the temperature distribution for a point at 25.25 m
from the upstream, 1.5 m from foundation in two and the three dimensional analysis
(conventional approach) is depicted in Figure 17. As shown in this figure, the results
of the two analysis (2D and 3D) are very close, and there may be no difference
between them, implementing that the 2D analysis could be convenient for this type of
problems.
Figure 18 shows the temperature distribution with the variation of cross valley
stress (z-direction) with time at points 2.6 m from upstream and 1.5 m from
foundation with constant and time dependent modulus of elasticity. Compression
stresses develop inside the dam body at early stage (high temperature of RCC) due to
RCC tendency to expand and the presence of restraint boundary conditions. The
analysis conducted using a constant modulus of elasticity overestimated the
compressive stress calculated with 3.7 MPa against 1.5 MPa estimated by the
13
nonlinear time dependent modulus of elasticity model. Moreover, the zero stress state
developed in 110 and 165 days after placement for constant and nonlinear time
dependent modulus of elasticity models, respectively. (if nonlinear Modulus is
considered, zero-stress-temperature should arise earlier and should be higher than
with constant Modulus?)
Figure 19 shows the temperature distribution and the variation of cross valley
stress (z-direction) with time at 2.0 m away from upstream and 15 m from foundation
with constant and nonlinear time dependent modulus of elasticity. The results and
findings are similar to those in Figure 18.
Figure 20 also represents the temperature distribution and the variation of
cross valley stress with time at center of dam, 15 m from foundation. As shown in this
figure, this point is under adiabatic conditions, where the temperature change is very
slow, and the change in stresses is small (what is the reason for the change in
stresses?). In fact, this point is mainly compression and there is no threat that the
crack will take place.
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