1. Department of Civil Engineering, Kobe University, Rokkodai 1, Nada, Kobe 657-8501, Japan
2. Faculty of Civil Engineering, Engineering College, University of Tehran, Keshavarz Blvd, No. 268, Tehran 1417633861, Iran
3. Engineering Division, Osaka City Waterworks Bureau, Nanko-Kita, Suminoe, Osaka 559-8558, Japan