Gajanan Sabnis

Reinforcement For Small Scale Direct Models of Concrete Structures

THE PROBLEM OF PROVIDING SUITABLE REINFORCEMENT IN SMALL SCALE DIRECT MODELS OF REINFORCED CONCRETE STRUCTURES IS EXAMINED IN DETAIL. MAXIMUM ATTENTION IS GIVEN TO BEHAVIOR IN BOND OF SEVERAL DIFFERENT TYPES OF REINFORCING WIRE. BASIC STRENGTH PROPERTIES OF THE WIRES ARE ALSO PRESENTED, ALONG WITH RECOMMENDATIONS ON ANNEALING PROCESSES REQUIRED IN PRODUCING REINFORCEMENT OF PROPER STRENGTH. THE STUDY IS RESTRICTED TO WIRE SIZES NOT EXCEEDING ABOUT 1/6 IN. DIAMETER. SURFACE DEFORMATIONS ON MODEL WIRES ARE EXAMINED IN RELATION TO THE ACTUAL SIZES AND PATTERNS OF DEFORMATION ON MODERN DEFORMED PROTOTYPE BARS. COMMERCIALLY AVAILABLE THREADED WIRES AND DEFORMED WIRES WERE INVESTIGATED, AS WELL AS A SPECIALLY DEFORMED WIRE PRODUCED IN THE CORNELL STRUCTURAL MODELS LABORATORY. BOND PULLOUT TESTS WERE MADE WITH EACH OF THE VARIOUS DEFORMED WIRES AND WITH PLAIN WIRES, USING SCALED DOWN CYLINDRICAL CONCRETE SPECIMENS OF 1 IN. DIAMETER. VARIABLES INCLUDED WIRE DIAMETER, EMBEDMENT LENGTH RATIO L/D, AND TYPE OF MODEL CONCRETE (BOTH CEMENT AND GYPSUM MORTARS). TEST RESULTS ARE COMPARED WITH SIMILAR TESTS ON PROTOTYPE DEFORMED BARS. IT IS CONCLUDED THAT PLAIN WIRES DO NOT ADEQUATELY MODEL THE BOND CHARACTERISTICS OF PROTOTYPE DEFORMED BARS, BUT THAT ULTIMATE BOND STRENGTHS MAY BE MODELED SUCCESSFULLY WITH PROPERLY DEFORMED MODEL WIRES. TENSILE CRACKING STUDIES WERE MADE TO INVESTIGATE CRACKING SIMILITUDE. WIRES EMBEDDED IN RECTANGULAR MODEL CONCRETE SECTIONS (MODELED AFTER PROTOTYPE TESTS BY BROMS) OF DIFFERENT SCALES WERE SUBJECTED TO TENSION; THE RESULTING CRACK PATTERNS WERE COMPARED TO PROTOTYPE RESULTS. WHEN APPROPRIATELY DEFORMED WIRES WERE USED, THE NUMBER OF PRIMARY CRACKS AT SIMILIAR STRESS LEVELS COMPARED CLOSELY WITH THE PROTOTYPE RESULTS. SPECIMENS CONTAINING PLAIN, UNDEFORMED WIRES DEVELOPED ONLY A SMALL PERCENTAGE OF THE TOTAL NUMBER OF CRACKS. DUPLICATE SPECIMENS OF EACH TEST GAVE CLOSE RESULTS, INDICATING ADEQUATE REPRODUCIBILITY OF THE MODEL TESTS. /ACI/