the heat transfer that occurs between a fluid (e.g., air

)

or water) and a concrete surface. The following

2* o*

equations are from the ASHRAE (American Society

of Heating, Refrigerating and Air Conditioning Engi-

neers) Handbook and Product Directory-1977 Funda-

mentals (1977). These equations may be used for

computing the film coefficients to be included in

)

ABAQUS for modeling convection. For surfaces

without forms, the coefficients should be computed

based on the following:

)

0.1132*V * 0.8

(A-2)

)

and

0.0513(*V*)

0.165

(4) Foundation model. The foundation should be

(A-3)

included in the heat transfer model to determine a

realistic temperature distribution within the structure.

The foundation should be no less than 10 ft in depth

where,

based on previous parametric studies (Truman,

Petruska, and Ferhi 1992). Prior to performing the

)

2* o*

heat transfer analysis of the structure and foundation,

a heat transfer analysis should be performed on the

foundation for a time period of 1 year to determine

the temperature distribution in the foundation for the

The wind velocity may be selected based on monthly

start of concrete placement. The vertical size of

average wind velocities at the project site. Data can

elements in the foundation model should be deter-

be obtained from the National Climatic Data Center

mined using the equation A-1, but the horizontal size

for a given location and can be generalized over a

will be dictated by the size of the elements in the

period of several months for input into the analysis.

structure. The heat transfer analysis of the structure

If forms and insulation are in place, then the values

and foundation may include an interface element at

for h computed in the equations above should be

the foundation-concrete interface. If an interface

modified as follows:

element is used, a gap conductance of 200 Btu-

in./in.2-day-F should be specified.

1

1

( )formwork ( )insulation ( )

(5) Time increments. The maximum time incre-

ments to be used in the heat transfer analysis are

1

given in Table A-2. These same limits on increments

(A-4)

are used in the stress analysis. The small increments

1

( )

at the early times are necessary to capture the large

amounts of heat that are generated in very young

concrete. The time increments specified in Table A-2

where

are for days after a lift of concrete has been placed.

Exceeding the maximum time increments specified in

Table A-2 is permissible, provided a parametric study

is performed which demonstrates that results for both

A-19