1. Doctoral Candidate, Dept. of Civil Engineering, Aristotle Univ. of Thessaloniki, Thessaloniki GR 54124, Greece.
2. Professor, Dept. of Civil Engineering, Univ. of Patras, Patras GR 26500, Greece (corresponding author).
3. Professor, Dept. of Civil Engineering, Aristotle Univ. of Thessaloniki, Thessaloniki GR 54124, Greece.