Development of Analysis and Design Procedures for Spread Footings

Keywords: Foundation.  Spread footings.  Dynamic loading.  Dynamic analysis.  Seismic loading.  Seismic response.  Bridges.  Bridge piers.  Bents.  Radiation damping.  Rocking motion.  Soil structure interaction.  Impedance functions.  Footing bearing capacity failure.  Pore water pressure.  Seismic condition uplift.

Abstract: This report describes a series of numerical analyses that address spread footings under dynamic and seismic loading. These analyses were conducted for a typical idealized pier with a single-column bent founded on a footing on the surface of, or embedded in, a layered soil profile. The report includes charts and tables for computing footing impedances for a variety of soil conditions and vibration modes. The decomposition of seismic response into kinematic and inertial parts is discussed, as are the effects of soil material nonlinearity on the response. A parameter study of the response of bridge piers (without uplift) showed the effect of increased period due to soil-structure interaction on seismic response and the influence of radiation damping. Finally, footing bearing capacity failure, development of pore water pressure, and uplift under seismic conditions are discussed. A bibliography and appendices are included.