A number of agencies and industry groups publish recommendations for design of deep foundations under lateral loading. The most widely-used of these are summarized as follows:
Driven piles and drilled shafts used in transportation facilities often cite the following reference documents:
“Design and Construction of Driven Pile Foundations” Publication No. FHWA NHI-05-042 (2006).
This manual suggests the use of lateral load tests or analytical methods in the lateral pile capacity analysis. Broms’ (1964a, 1964b) hand calculation method is mentioned as an appropriate alternative “for small projects”. The p-y method is recommended for the analysis of “all design of major pile foundation projects” and it refers to Reese’s solution (1984) and LPILE computer software. Moreover, it indicates the use of p-multipliers (Brown et al. 1988) in case of a pile group.
“Drilled Shafts: Construction Procedures and LRFD Design Methods”, Publication No. FHWA-NHI-10-016, GEC 10.
The FHWA drilled shaft manual identifies the p-y method as “the recommended methodology for computing the response of drilled shafts to lateral and overturning forces”. It indicates the use of p-multipliers (Brown et al. 1988) in case of a pile group. Alternative methods identified include Broms, elastic continuum solutions, and nonlinear finite element models.
The American Petroleum Institute (API) document “Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms-Working Stress Design” Section 6.8 provides recommendations for design of piles under lateral loading. The recommended procedure is the p-y method. In fact, development of the p-y method was largely a result of research initiated in the 1960’s by API aimed at developing analytical tools for design of driven pipe piles for offshore structures. API recommends specific p-y curve models based on load tests on pipe piles in representative geomaterials, including Matlock (1970) for soft clay, Reese and Cox (1975) for stiff clay, and O’Neill and Murchison (1983) for sand. Refer to the P-Y Curves menu on this website for additional information on these p-y curve models.
Lateral/moment loading typically is the governing case for deep foundations used to support electrical transmission line structures. The Electrical Power Research Institute (EPRI) has sponsored development of design methods for transmission line structures, predominately drilled shafts. A set of computer software tools with the acronym FAD (Foundation Analysis and Design) has been developed for single pole (MFAD), H-frame (HFAD), and lattice tower structures (TFAD). Analysis is based on a subgrade modulus model with the soil resistance represented by four types of springs: 1. lateral translational springs, 2. vertical side shear springs, 3. base-moment springs, and 4. base shear translational springs. The nonlinear spring parameters are calibrated to a data-base of load tests on foundations with length to diameter ratios representative of those used in the electrical transmission line industry, which are typically short reinforced concrete drilled shafts with embedment depths in the range of 3 to 8 times the diameter. The shaft is treated as a linearly elastic member with uniform flexural stiffness that undergoes rigid body deformation.
Many building codes require deep foundations supporting buildings to be designed for lateral loading, but are non-prescriptive with regard to analytical methods. The following, from the California Building Code, is typical:
1810.2.4 Lateral loads. The moments, shears and lateral deflections used for design of deep foundation elements shall be established considering the nonlinear interaction of the shaft and soil, as determined by a registered design professional.
In addition to analytical methods, all of the agencies and organizations cited above have provisions for deep foundation design based on site-specific lateral load tests, assuming the test conditions are representative of those encountered on the project, in terms of deep foundation type and geometry, subsurface conditions, and loading.
