MEMBRANE ACTION IN SLABS

THIS PAPER IS CONCERNED WITH THE INCREASE IN LOAD CAPACITY AND CHANGES IN BEHAVIOR WHICH OCCUR WHEN TRANSVERSELY LOADED REINFORCED AND UNREINFORCED CONCRETE SLABS ARE RESTRAINED AGAINST LATERAL DISPLACEMENT AT THE EDGES. THE EXPERIMENTAL PHASE OF THE STUDY IS RESTRICTED TO SQUARE SLABS, UNREINFORCED OR REINFORCED NEAR THE BOTTOM WITH STEEL WIRES UNIFORMLY AND EQUALLY DISTRIBUTED IN EACH DIRECTION. THE FORM PARAMETERS WHICH WERE VARIED ARE SPAN-TO-DEPTH RATIO AND REINFORCEMENT RATIO. THREE MAIN CONDITIONS OF EDGE RESTRAINT ARE CONSIDERED: RESTRAINT TO ELONGATION AT THE BOTTOM ONLY, CLAMPED AND SIMPLY SUPPORTED. THE RESTRAINING FORCE REQUIRED TO PREVENT ELONGATION IS MEASURED AND RECORDED THROUGHOUT THE LOADING RANGE. THE TESTS ARE PRIMARILY CONCERNED WITH COMPRESSIVE MEMBRANE ACTION RESULTING FROM RESTRAINT TO ELONGATION, BUT TENSILE ACTION CAUSED BY RESTRAINT TO INWARDS MOVEMENT OF THE EDGE IS ALSO STUDIED. IN THE THEORETICAL PHASE, SIMPLIFIED EXPRESSIONS FOR PREDICTING THE BEHAVIOR ABOVE ARE DEVELOPED, AND ARE COMPARED WITH THE TEST RESULTS. /ACI/