1. Graduate Student, Dept. of Civil Engineering, Univ. of Patras, GR-26500 Patras, Greece (corresponding author).
2. Professor, Dept. of Civil Engineering, Univ. of Patras, GR-26500 Patras, Greece.
3. Associate Professor, Dept. of Civil Engineering, Univ. of Patras, GR-26500 Patras, Greece.