CEMP-E
TI 809-02
1 September 1999
CHAPTER 3
FOUNDATIONS
3-1. GENERAL. This chapter prescribes criteria for the design of building foundations
including spread footings, pile supported foundations, pier supported foundations, and
machinery foundations.
3-2. DESIGN. Allowable bearing pressures and allowable stresses where required in the
design of pile and pier foundations will be used with the allowable stress design load
combinations of ASCE 7. Where foundations are designed for seismic overturning using the
strength design load combinations of ASCE 7, the seismic overturning moment need not
exceed 75% of the value determined by either the equivalent lateral force method, or the
modal analysis method of TI 809-04, "Seismic Design for Buildings".
3-3. FOUNDATION AND SOILS INVESTIGATIONS. Foundation and soils investigations
when required will be in accordance with EM 1110-1-1804, " Geotechnical Investigations".
Additional information on foundation investigations can be found in the Navy Design Manual
(DM) 7.1, "Soil Mechanics", and Military Handbook (MIL-HDBK) 1007/3, "Soil Dynamics and
Special Design Aspects". The latter document describes the requirements for site specific
studies for seismically active areas. Pile and pier foundations will be designed and installed on
the basis of a foundations investigation and pile load test when required.
3-4. ALLOWABLE LOAD BEARING VALUES AND LATERAL SLIDING RESISTANCE OF
SOILS.
a. Allowable Bearing Pressures. Maximum allowable bearing pressures will be determined
for soil foundations in accordance with EM 1110-2-1905, "Bearing Capacity of Soils", and for
rock foundations in accordance with EM 1110-1-1908, "Rock Foundations". The presumptive
allowable bearing pressures for spread footing as provided in Table 4-8 of EM 1110-1-1905
can be used with caution for spread footings supporting small or temporary structures. Design
guidance for foundations can be found in TM 5-818-1 / AFM 88-3, Chapter 7, "Soils and
Geology Procedures for Foundation Design of Buildings and Other Structures (Except
Hydraulic Structures)", and in Navy Design Manual (DM) 7.02, " Foundations and Earth
Structures".
b. Lateral Sliding Resistance. The resistance of footings to lateral sliding will be
calculated by combining shear frictional resistance (V tan φ) and lateral soil resistance,
where:
V = vertical load
φ = Angle of internal friction
The lateral soil resistance will not exceed one-half the computed passive resistance.
c. Increases in Allowable Bearing Values. Allowable bearing pressures may be increased
by 1/3 for load combinations involving wind or earthquake.
3-1
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