ROTATABILITY OF PLASTIC HINGES IN REINFORCED CONCRETE STRUCTURES SUBJECTED TO BENDING

DREHFAEHIGKEIT PLASTISCHER GELENKE IN BIEGEBEANSPRUCHTEN STAHLBETONKONSTRUKTIONEN

FOR REINFORCED CONCRETE STRUCTURES, ADEQUATE ROTATION CAPACITY ASSUMED IN THE BEARING CAPACITY METHOD FOR PLASTIC HINGES CANNOT YET BE TAKEN AS CERTAIN. IN ORDER TO DETERMINE THE ROTATABILITY, 28 STRIP SLABS REINFORCED WITH DIFFERENT TYPES OF STEEL WERE SUBJECTED TO PRELIMINARY TESTS. THE MOST IMPORTANT RESULT FROM THESE TESTS WAS THAT THE DEFORMATION BEHAVIOUR OF REINFORCED CONCRETE IN THE PLASTIC AREA CAN ONLY BE DESCRIBED IF, TOGETHER WITH THE STRESS-DEFORMATION DIAGRAMS OF THE MATERIALS CONCRETE AND STEEL, THEIR BOND BEHAVIOUR IS ALSO KNOWN. FOR THIS REASON, IN ORDER TO FACILITATE THE DETERMINATION OF THE ROTATABILITY, PULL-OUT TESTS WERE CONDUCTED FOR DETERMINING THE BOND LAW UNDER PRACTICAL CONDITIONS, WHICH INCLUDED DETERMINATION OF THE INFLUENCE OF PLASTIC DEFORMATION OF THE STEEL IN THE REGION OF THE BOND. THE FINITE ELEMENT METHOD IS USED FOR DETERMINING ROTATABILITY THEORETICALLY. THIS METHOD ALLOWS GOOD ADAPTATION TO THE CONDITIONS EXISTING IN A PLASTIC ZONE, WHICH CAN ONLY BE ASCERTAINED INADEQUATELY WITH THE USUAL SIMPLIFICATIONS, SUCH AS KEEPING THE CROSS SECTION LEVEL, IGNORING THE CONCRETE STRESSES IN THE TENSION ZONE AND MAKING ASSUMPTIONS OF THE LENGTH OF THE PLASTIC AREA. TO VERIFY THE CALCULATION REINFORCED CONCRETE BEAMS HAVING VARIOUS GRADES OF REINFORCEMENT AND M/Q VALUES ARE BEING TESTED.