REINFORCED CONCRETE BEAM-COLUMN INVERTED KNEE JOINT BEHAVIOUR AFTER GROUND CORNER COLUMN LOSS-NUMERICAL ANALYSIS

  • BASEM SALAH ABDELWAHED Department of Mechanics of Materials and Constructions (MEMC), Faculty of Applied Sciences and Engineering. Free University of Brussels, Brussels, Belgium
  • BACHIR BELKASSEM Department of Construction Engineering and Materials, Royal Military Academy Brussels. Brussels. Belgium
  • JOHN VANTOMME Department of Mechanics of Materials and Constructions (MEMC), Faculty of Applied Sciences and Engineering. Free University of Brussels, Brussels, Belgium / Department of Construction Engineering and Materials, Royal Military Academy Brussels. Brussels. Belgium

Abstract

BEAM-COLUMN JOINTS ARE CRITICAL AND IMPORTANT COMPONENT IN THE LOAD PATH OF REINFORCED CONCRETE (RC) FRAMES, DUE TO THEIR FUNDA-MENTAL ROLE IN CONNECTING AND TRANSFERRING LOADS AMONG DIFFERENT RC FRAME COMPONENTS. AS A RESULTS OF INADEQUATE BEAM-COLUMN JOINTS EFFICIENCY, PREVIOUS STUDIES RECORDED DIFFERENT TYPES OF JOINTS DAMAGE. DEFICIENCY IN JOINTS PERFORMANCE IS REFERRED TO USING OLD NON-SEISMIC CODES GUIDELINES OR EVEN FOLLOWING RECENT ONES BUT FOR EXAMPLE, DUE TO THE LOSS OF A GROUND CORNER COLUMN IN RC FRAME, EXTERIOR JOINT TURNED INTO INVERTED KNEE JOINT. CODES PROVISIONS FOR EXTERIOR JOINTS ARE NOT SUFFICIENT TO KNEES ONE. THESE INVERTED KNEE JOINTS WITH RESULTED REINFORCEMENT DEFECTS IN TERMS OF JOINT VERTICAL STIRRUPS ABSENCE AND IMPROPER COLUMNS BAR ANCHORAGE ARE NOT FULLY KNOWN AND NOT DISCUSSED. THIS PAPER INVESTIGATES NUMERICALLY THE BEHAVIOUR OF THESE JOINTS UNDER A CLOSING MOMENT USING NONLINEAR FINITE ELEMENT (FE) ANALYSIS WITH LS-DYNA SOFTWARE. BEAM’S BAR ANCHORAGE TYPE AND JOINT VERTICAL STIRRUPS ARE THE MAIN PARAMETERS CONSIDERED; THREE-DIMENSIONAL FE MODELS OF A BEAM-COLUMN KNEE JOINT ARE DESCRIBED AND VERIFIED WITH EXPERIMENTAL RESULTS AVAILABLE IN LITERATURE. ALSO CONCRETE COMPRESSIVE STRENGTH, LONGITUDINAL REINFORCEMENT RATIO AND LATERAL BEAM EFFECT ON JOINT RESISTANCE ARE CONSIDERED. THIS STUDY INDICATES THAT, DIFFERENT TYPES OF BEAM’S BAR ANCHORAGE HAVE SIGNIFICANT EFFECTS ON JOINT CAPACITY, LOAD-DEFLECTION CHARACTERISTICS AND FAILURE MODES. ANCHORAGE BEAM’S BAR WITH U SHAPED PRODUCES BETTER BEHAVIOUR THAN 90° STANDARD HOOKS OR HEADED END. CONTRIBUTION OF JOINT VERTICAL STIRRUPS IS MORE INFLUEN-TIAL WITH HEADED BARS ANCHORAGE THAN WITH THE OTHER TWO ANCHOR-AGE TYPES. INCREASING CONCRETE COMPRESSIVE STRENGTH HAS A SIGNIFICANT EFFECT ON JOINT CAPACITY TO A CERTAIN LIMIT. INCREASING BEAM REINFORCEMENT RATIO IMPROVES FLEXURAL RESISTANCE OF THE ANCHORED BEAM BARS AND INCREASES THE JOINT RESISTANCE CAPACITY. THE PRESENCE OF LATERAL BEAMS INCREASES THE JOINT CONFINEMENT AND REDUCES THE RATE OF CONCRETE DEGRADATION IN THE JOINT AFTER REACHING ULTIMATE CAPACITY, ADDED TO THAT AN INCREASE IN THE MAXIMUM LOAD RESISTANCE.

Published
2018-08-21
Section
Articles