Analytical moment - rotation curves for rigid foundations based on a Winkler model

Analytical equations for the moment-rotation response of a rigid foundation on a Winkler soil model are presented. An equation is derived for the uplift-yield condition and is combined with equations for uplift- and yield-only conditions to enable the definition of the entire static moment-rotation response. The results obtained from the developed model show that the inverse of the factor of safety, chi, has a significant effect on the moment-rotation curve. The value of chi = 0.5 not only determines whether uplift or yield occurs first but also defines the condition of the maximum moment-rotation response of the footing. A Winkler model is developed based on the derived equations and is used to analyze the TRISEE experiments. The computed moment-rotation response agrees well with the experimental results when the subgrade modulus is estimated using the unload-reload stiffness from static plate load-deformation tests. A comparison with the recommended NEHRP guidelines based on the FEMA 273/274 documents shows that the choice of value of the effective shear modulus significantly affected the comparison. (C) 2003 Elsevier Science Ltd. All rights reserved.