RELAXATION ANALYSIS OF STEEL WIRE FOR PRESSTRESSED CONCRETE

Abstract

This research focuses on analyzing the relaxation value of steel wire for prestressed concrete from the testing method according to the Thai Industrial Standards TIS 95-2540 and proving the significance of the wire strain rate. The test results showed that When the initial pulling force is 70% of the maximum pull force Wires with larger diameters have a higher initial pulling force. The rate of pulling force is inversely proportional to the duration. For the first 10 hours, The rate of pulling force has the highest value. The testing of 4, 5 mm diameter chevron wires and 7 mm stress mark types provides an average relaxation of 1,000 hours, which is 2.63%, 2.06% and 2.03% respectively, which is in line with the criteria.  For the first 10 hours, Strain rate of all 3 sizes of wire are as high as 0.8x10^-4 - 3.7x10^-4% per hour which is higher than the range of 100 hours and 1000 hours which is 0.8x10^-5 - 3.2x10^-5% per hour and 1x10^-9 - 1.6x10^-9% per hour, respectively Details on the methodology and results of the trial will be used as a reference for the standard improvement