FATIGUE STRENGTH OF 1/2-INCH DIAMETER STUD SHEAR CONNECTORS

COMPOSITE STEEL AND CONCRETE BEAMS WERE TESTED IN FATIGUE AT VARIOUS STRESS LEVELS. ALL TWELVE BEAMS TESTED HAD 1/2-IN . DIAMETER WELDED STUDS AS SHEAR CONNECTORS. THE BEAMS WERE DESIGNED SO THAT NORMAL WORKING STRESSES WOULD BE ACHIEVED AT PEAK LOADS DURING REPEATED LOADING WHILE THE SHEAR STRESS ON CONNECTORS WAS SUFFICIENTLY HIGH TO PRODUCE FATIGUE FAILURE. FATIGUE FAILURE OF CONNECTORS ACTUALLY OCCURRED IN ELEVEN OF THE BEAMS. ELECTRICAL RESISTANCE STRAIN GAGES WERE USED IN EIGHT OF THE TEST BEAMS TO DETECT WHEN FATIGUE CRACKS WERE INITIATED IN CONNECTORS. THE USE OF SUCH STRAIN GAGES ENABLED THE INVESTIGATORS TO DETERMINE THE EXTENT OF FATIGUE FAILURE AT ANY TIME DURING THE TESTING. THIS INFORMATION WAS COMPARED WITH END SLIP AND DEFLECTION DATA TAKEN DURING THE TESTS. THE CRITERION OF FAILURE WAS TAKEN AS THE INITIAL CRACKING OF A PAIR OF SHEAR CONNECTORS. ON THIS BASIS AN S-N CURVE WAS OBTAINED FROM THE RESULTS OF SEVEN OF THE BEAM TESTS. A STATISTICAL ANALYSIS OF THESE DATA WAS MADE AND THE 95 PERCENT CONFIDENCE LIMITS OF THE DATA WERE OBTAINED. THE DATA ON FATIGUE OF STUD CONNECTORS OBTAINED BY OTHER INVESTIGATORS FALL GENERALLY WITHIN THESE 95 PERCENT CONFIDENCE LIMITS. /AUTHOR/