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P. G. Kossakowski
Kielce University of Technology, Faculty of Civil Engineering and Architecture, Department of Strength of Materials and Concrete Structures, Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland.
W. Raczkiewicz
Kielce University of Technology, Faculty of Civil Engineering and Architecture, Department of Strength of Materials and Concrete Structures, Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland