1. Civil Engineering Department, Purdue University, West Lafayette, IN 47907, USA
2. Civil Engineering Department, New Mexico State University, Las Cruces, NM 88003-8001, USA
3. Centre for Offshore Foundation Systems M053, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
4. Civil and Environmental Engineering, University of California Berkeley, Berkeley, CA 94720, USA