ガス圧接継手の引張試験に関する調査研究 : 経歴の明確な試験片についての調査(2)

抄録

This report presents the results of tensile tests carried out by two specific construction firms on gas-pressure-welded joints in reinforcement bars. The tests were conducted in accordance with NAK specification and JIS Z 3120 (method for testing gas - pressure - welded joints in bars for reinforced concrete). The data obtained from construction field were used to determine the percentage of the joints that failed in connection and the distribution of strength at failure. The following results were obtained from tensile tests conducted from July, 1987 to December 1988 by two specific construction firms on the total 19117 test pieces. The type of pieces was grade SD 35, and the diameters of the pieces ranged from D 19 to D 29. In this investigation, the factors related to execution enviroment, such as member location in columns and beams, and story numbers in the building were examined. 1. 55 pieces, or 0.29 % of the total number tested failed in connection. The connection failure rate increased with increasing diameter. 2. No piece failed below the long-time alowable tensile stress (2 200 kgf/cm2). 3. 0.016 % failed below the yield point specified in JIS (3 500 kgf/cm2). 4. 0.073 % failed below the tensil strength specified in JIS (5 000 kgf/cm2). 5. The average stress at failure of 55 pieces was 5 160 kgf/cm2, and was well above the yield point specified in JIS. 6. Out of the 55 pieces that failed, 3 or 0. 016 % of the total number tested, failed before the yield. 7. Out of the 55 pieces that failed, 52 failed after the yied. The average ratio of failure strength to yield strength was 1.38. 8. 0.25 % of the column pieces and 0.32 % of the beam pieces failed in connection. The connection failure rate of the beam pieces was bigger than that of the column pieces. 9. The stress at failure of the beam pieces was between 4 400 kgf/cm2 and 5 900kgf/cm2, and that of the column pieces was between 2 300 kgf/cm2 and 6 100 kgf/cm2. The stress at failure of the beam pieces is distributed in wider range than that of the column pieces. 10. The connection failure rate of basement pieces was bigger than that of the aboveground floor pieces. 11. The minimum stress at failure of the beam pieces was smaller than that of the column piece in each floor.