1. Lecturer, Laboratory of Reinforced Concrete, Dept. of Civil Engineering, Democritus Univ. of Thrace (DUTh), Vas. Sofias 12, 67100 Xanthi, Greece (corresponding author).
2. Civil Engineer, Dept. of Civil Engineering, Democritus Univ. of Thrace, Greece.
3. Professor, Laboratory of Reinforced Concrete, Dept. of Civil Engineering, Democritus Univ. of Thrace (DUTh), 67100 Xanthi, Greece.