1. Department of Civil and Structural Engineering, University of Sheffield, Mappin Blg., Mappin St., Sheffield, S1 3JD, UK, Tel.: +44 114 2225760, Fax: +44 114 2225760, J.B.Boxall@Sheffield.ac.uk
2. Faculty of Engineering and Industrial Science, Swinburne University of Technology, Hawthorn, Melbourne, Vic 3122, Australia, Tel.: +61 3 958 732 06, Fax: +61 3 958 732 06, rach@mad.biz