1. Faculty of Engineering and Science, Univ. Tunku Abdul Rahman, 53300 Kuala Lumpur, Malaysia (corresponding author).
2. Faculty of Civil Engineering, Univ. Teknologi Malaysia, 81310 Skudai, Johor, Malaysia.
3. Chancellery Division, Linton Univ. College, Persiaran UTL, Bandar Univ. Teknologi Legenda (BUTL), Batu 12, 71700 Mantin, Negeri Sembilan, Malaysia.