1. Coastal and Hydraulics Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS 39180-6133; USA and Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093
2. Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093
3. Coastal & Hydraulics Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS 39180-6133