The Twelfth Joint Meeting of the U.S. -Japan Panel on Wind and Seismic Effects was held in Gaithersburg , Maryland on May 19-23, 1980. The proceedings of the Joint Meeting include the program, the formal resolutions, the Task Committee Reports, and the technical papers. The subjects covered in the papers include:(1) the characterization of seismic ground motion, (2) the characterization of natural wind and extreme wind records, (3) structural response to earthquake loading, (4) storm surge and tsunamis, (5) recent developments in seismic design criteria, ( 6) technical cooperation with developing countries, (7) earthquake hazard mitigation, and ( 8) structural response to wind loading.

Torsional resonant column tests were performed on Monterey No. 0 sand of 60% relative density under confining pressures ranging from 10 to 300 kPa to evaluate the dynamic properties of the sand. Both solid and hollow cylindrical specimens were used in testing, and shear moduli and damping ratios were determined for cyclic shear strain amplitudes from 10−4 to 5 × 10−2%. The test results indicated that the type of specimen, that is, solid or hollow cylinder, had no significant effect on the calculated shear moduli and damping ratios, except that at very low strain amplitudes (γ ≤ 10−3%) where the shear moduli of the hollow specimens tended to be slightly lower and the damping ratios slightly higher. Multistage testing had no significant effect on the shear moduli when the values were compared with those from the single-stage testing; however, multistage testing had a significant effect on the damping ratios under a confining pressure 100 kPa. Both shear moduli and damping ratios obtained in this program correlate well with other available data.

The prediction of pore-water pressure buildup in sands caused by undrained cyclic loading is one of the key items in evaluating the potential for liquefaction of sandy sites during earthquakes. Presented herein are data indicating that, in strain-controlled tests, there is a predictable correlation between cyclic shear strain, number of cycles, and pore-water pressure buildup; this correlation is much less sensitive to factors, such as relative density and fabric than comparable results obtained from stress-controlled tests. Also, there is a threshold cyclic shear strain below which there is no sliding at the contacts between sand particles, and essentially no pore-water pressure buildup occurs. The data indicate that, for clean sands, this threshold shear strain, as well as the pore-water pressure buildup for strains slightly above the threshold, are basically independent of relative density, grain size distribution, fabric, and method of testing (triaxial and direct simple shear). However, both threshold shear strain and pore-water pressure buildup do depend on the overconsolidation ratio.

Prediction of pore-water pressure buildup of a saturated sand deposit subjected to dynamic load is important for dynamic stability analysis of the deposit. Empirical equations, proposed by Drnevich to correlate the predicted pore-water pressure buildup with that measured during undrained resonant column tests on saturated Ottawa silica sand, were used to predict the results of tests on virgin Monterey No. 0 sand specimens. It was found that, with a modification of the coefficient in the empirical equation, there is good correlation between predicted and measured excess pore-water pressures when a high degree of saturation (B ≥ 0.96) was achieved in the specimen preparation. The correlation is poor for specimens with a lower degree of saturation (B < 0.96).