1. Lecturer, Dept. of Civil Engineering, Kasetsart Univ., 50 Phaholyothin Rd., Bangkok 10900, Thailand (corresponding author).
2. Associate Professor, School of Engineering and Technology, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathum Thani 12120, Thailand.
3. Lecturer, Dept. of Civil Engineering, Srinakharinwirot Univ., Rangsit-Nakhonnayok Rd., Nakhonnayok 26120, Thailand.