SERVICE LOAD BEHAVIOR OF LOW RISE COMPOSITE FRAMES CONSIDERING CREEP, SHRINKAGE AND CRACKING

Abstract

COMPOSITE BEAMS WITH PRECAST DECKS HAVE AN ADVANTAGE IN THE SPEED OF CONSTRUCTION. SYSTEMATIC STUDIES ARE REPORTED FOR THE SERVICE LOAD BEHAVIOR OF COMPOSITE FRAMES CONSISTING OF THIS TYPE OF COMPOSITE BEAMS AND STEEL COLUMNS. A HYBRID PROCEDURE RECENTLY DEVELOPED BY THE AUTHORS, FOR THE ANALYSIS OF SUCH COMPOSITE FRAMES SUBJECTED TO SERVICE LOAD, HAS BEEN USED FOR CARRYING OUT THE STUDIES. THE APPLICABILITY OF THE PROCEDURE HAS BEEN DEMONSTRATED FOR COMPOSITE CONSTRUCTION WITH PRECAST SLABS AND THEN DETAILED STUDIES HAVE BEEN CARRIED OUT FOR A SINGLE STORY FRAME. THE AGE OF CONCRETE AT THE TIME OF LOADING, MAGNITUDE OF LOAD, GRADE OF CONCRETE, RELATIVE HUMIDITY AND TENSION STIFFENING ARE THE PARAMETERS WHOSE EFFECTS HAVE BEEN STUDIED ON THE BENDING MOMENTS AT THE BEAM ENDS AND MIDSPAN DEFLECTIONS. THE RELATIVE HUMIDITY IS FOUND TO BE THE MORE SIGNIFICANT PARAMETER AFFECTING THE TIME-DEPENDENT CHANGES IN BENDING MOMENTS AND MIDSPAN DEREECTIONS. FORM THE STUDIES CARRIED OUT FOR A FIVE STORY AND A EIGHT STORY FRAME, IT IS SHOWN THAT THE USE OF SIMPLIFIED MODELS (SUBSTITUTEFRAMES) CAN LEAD TO ERRORS.