The Earthquake Engineering Online Archive

Interaction effects of simultaneous torsional and compressional cyclic loading of sand

Griffin, Patrick M.; Houston, William N.

UCB/EERC-79/34, Earthquake Engineering Research Center, University of California, Berkeley, 1979-12, 338 pages (495/G75/1979)

An experimental program based on laboratory test studies and scaled slope model tests was conducted with specimens of Monterey No. 0 sand to study the effects of interactive coupling during combined compression (normal) and shear loading on the response of sands to dynamic loading. The research program included the following experimental studies: (1) resonant column tests on cylindrically shaped specimens using longitudinal and torsional excitation, both separately and in combination; (2) thin-walled hollow cylinder tests using longitudinal and torsional cyclic excitation, both separately and in combination; (3) large-scale shaking table tests on slope models, using horizontal and vertical cyclic excitation, both separately and in combination. Two methods were developed for calculating the degradation of compression modulus with strain under combined dynamic loading conditions. The first of these, the strain ratio method, requires the computation of either the instantaneous or an overall average ratio of shear strain amplitude to compression (normal) strain amplitude. The second method, the octahedral shearing strain method, requires computation of either the instantaneous or overall average value of the octahedral shearing strain amplitude. Although both methods lose accuracy as the straining progresses from elastic to plastic and as specimens approach failure, the use of either method under conditions of combined shear and compression loading represents a significant improvement over the practice of neglecting interactive effects. An analysis method was developed and presented for predicting yield accelerations in granular slopes under combined vertical and horizontal loading conditions. The shaking table test results were compared with the predicted values of yield acceleration.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-79-34.pdf (28 MB)