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Title: Dynamic response of rectangular footings in clay and sand
Authors: Taylor, Hugh M.
Keywords: Clays
Dynamic response
Concrete footings
United States. Defense Nuclear Agency.
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: The static and dynamic behavior of small-scale rectangular footings supported on the surface and buried in sand and clay specimens was determined experimentally, and the results are compared herein with dimensionless load-displacement relations previously developed for square footings. The effect of shallow depth of burial for rectangular footings in clay was found to be small for the range of parameters investigated, i.e., the nondimensional loading required to produce a given nondimensional displacement is approximately 10 percent greater for buried footings than for surface footings. When the nondimensional load terms in the static and dynamic load-displacement relations developed for square footings on clay were divided by 𝓁/b (ratio of footing length to footing width), at equal nondimensional displacements, the ratio of rectangular to square footing nondimensional loadings varied from 0.70 to 0.85. When the nondimensional static and dynamic load-displacement relations developed for square footings on dry sand were divided by 𝓁/b, the nondimensional static and dynamic footing loads required to produce given values of nondimensional displacements of rectangular footings on the surface of a sand were found to be 55 percent and 35 percent greater, respectively, than those previously developed for surface square footings. At a d/b (ratio of depth of burial to footing width) of one, the nondimensional static footing loads for the rectangular footing tests were approximately 30 percent greater than those reported previously for square footings at equal nondimensional displacements. However, also at given nondimensional displacements, the nondimensional dynamic footing loads for rectangular footings at d/b = 1 were, on the average, slightly less than the comparable dimensionless loads observed during the earlier tests on square footings. For purposes of design of impulsively loaded footings, the nondimensional load-displacement curves previously developed for square footings in clay can be used for rectangular footings in clay if the nondimensional load term is divided by 𝓁/b and if the value obtained for a given dimensionless settlement is reduced by about 20 percent. No similar recommendation can be made for rectangular footings in sand since the relationship of the load-displacement curves in the region short of failure is dependent upon footing width and since the footings tested were much smaller than the practical range of footing size. Additional research is recommended to explore the effect of size on rectangular to square footing load-displacement relations. Presently, the most reasonable approach to design appears to be to use available empirical techniques to estimate the static load-displacement relation for the prototype rectangular footing and then use the data presented herein on the relation between dynamic and static small-scale load-displacement curves for guidance in defining a dynamic load-displacement function for the prototype rectangular footing. NOTE: This file is large. Allow your browser several minutes to download the file.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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