A Simplified Design Approach - Simplified Design of Reinforced Concrete Buildings - page 20

1.8.4 Footings

The required footing sizes can usually be obtained in a straightforward manner. In general, the base area is
determined by dividing the total service (unfactored) loads from the column by the allowable (safe) soil
pressure. In buildings without shearwalls, the maximum pressure due to the combination of gravity and wind
loads must also be checked. The required thickness may be obtained for either a reinforced or a plain footing
by using the appropriate simplified equation given in Chapter 7.

1.8.5 Fire Resistance

To insure adequate resistance to fire, minimum thickness and cover requirements are specified in building
codes as a function of the required fire resistance rating. Two hours is a typical rating for most members;
however, the local building code should be consulted for the ratings which apply to a specific project or
special portions of projects.

Member sizes that are necessary for structural requirements will usually satisfy the minimum requirements
for fire resistance as well (see Tables 10-1 and 10-2). Also, the cover requirements specified in ACI 7.7 will
provide at least a three-hour fire resistance rating for restrained floor members and columns (see Tables 10-3,
10-4, and 10-6).

It is important to check the fire resistance of a member immediately after a preliminary size has been obtained
based on structural requirements. Checking the fire resistance during the preliminary design stage eliminates
the possibility of having to completely redesign the member (or members) later on.

In the examples that appear in the subsequent chapters, the applicable fire resistance requirements tabulated in
Chapter 10 are checked for all members immediately after the preliminary sizes are obtained. The required fire
resistance ratings for both example buildings are listed in Section 1.7.

References

1.1 Building Code Requirements for Structural Concrete ACI 318-11 and Commentary— American Concrete
Institute, Famington Hills, Michigan, 2011.

1.2 Building Movements and Joints , EB086, Portland Cement Association, Skokie, Illinois 1982, 64 pp.

1.3 Concrete Floor Systems-Guide to Estimating and Economizing , SP041, Portland Cement Association,
Skokie, Illinois, 2000, 41 pp.

1.4 Long-Span Concrete Floor Systems , SP339, Portland Cement Association, Skokie, Illinois, 2000, 97 pp.

1.5 American Society of Civil Engineers Minimum Design Loads for Buildings and Other Structures ,
ASCE/SEI 7-05, American Society of Civil Engineers, New York, N.Y., 2006.