Torque control method and turn of nut method are defined as clamping method of high strength bolts in the steel construction specifications. These clamping methods are based on torque coefficient and nut rotation angle respectively, but the clamping force introduced into bolts is affected by the var...
Torque control method and turn of nut method are defined as clamping method of high strength bolts in the steel construction specifications. These clamping methods are based on torque coefficient and nut rotation angle respectively, but the clamping force introduced into bolts is affected by the variation of torque coefficient. Particularly quality control of torque coefficient is essential activity because torque control method, which is presently adopted as clamping method in domestic construction sites, is affected by variation of torque coefficient This study was focused on evaluating the effect of environmental factors and errors of installing bolts during tightening high strength bolts on clamping force. Test parameters were designed for simulating environmental factors and the failure of quality control activity in the field of construction sites. Test parameters are as follow; the variation of temperature, 'wet' condition, 'rust' condition, 'only exposure to air' condition. Additionally the errors of workability such as installation of 2 washers, upsetted washer are selected. On the way of these tests, torque, torque coefficient, tension and angle of nut rotation were obtained by bolt testing machine. Test specimens of 4 types of bolts -High Strength Hexagon bolt on KS B 1010 and ASTM A490, Torque Shear Bolt on KS B 2819, High Strength Hexagon bolt coated with zinc were recommended. Based on test results, the tightening characteristics subjected to environmental parameters were investigated and compared with the results of normal condition. To sum up the test result, as temperature is lower, torque coefficient is higher but clamping force is lower contrary. At the condition of low temperature below 0℃, torque coefficient exceeded the range of standard provision. In case of clamping high strength bolts by torque control method regarding torque coefficient as the value written on the product specification, required strength may be not ensured at a low temperature. At 'wet' and 'rust' condition, torque coefficient is higher than that of normal condition. This is why lubricant was eliminated from the surface of the thread of high strength bolt. Tensile test was conducted to evaluate the effect of the environmental factor on bolted joints. As a result of tensile tests, decrease of clamping force subjected to increase of torque coefficient brings about the early slip which affects the life safe performance of steel structure.
Torque control method and turn of nut method are defined as clamping method of high strength bolts in the steel construction specifications. These clamping methods are based on torque coefficient and nut rotation angle respectively, but the clamping force introduced into bolts is affected by the variation of torque coefficient. Particularly quality control of torque coefficient is essential activity because torque control method, which is presently adopted as clamping method in domestic construction sites, is affected by variation of torque coefficient This study was focused on evaluating the effect of environmental factors and errors of installing bolts during tightening high strength bolts on clamping force. Test parameters were designed for simulating environmental factors and the failure of quality control activity in the field of construction sites. Test parameters are as follow; the variation of temperature, 'wet' condition, 'rust' condition, 'only exposure to air' condition. Additionally the errors of workability such as installation of 2 washers, upsetted washer are selected. On the way of these tests, torque, torque coefficient, tension and angle of nut rotation were obtained by bolt testing machine. Test specimens of 4 types of bolts -High Strength Hexagon bolt on KS B 1010 and ASTM A490, Torque Shear Bolt on KS B 2819, High Strength Hexagon bolt coated with zinc were recommended. Based on test results, the tightening characteristics subjected to environmental parameters were investigated and compared with the results of normal condition. To sum up the test result, as temperature is lower, torque coefficient is higher but clamping force is lower contrary. At the condition of low temperature below 0℃, torque coefficient exceeded the range of standard provision. In case of clamping high strength bolts by torque control method regarding torque coefficient as the value written on the product specification, required strength may be not ensured at a low temperature. At 'wet' and 'rust' condition, torque coefficient is higher than that of normal condition. This is why lubricant was eliminated from the surface of the thread of high strength bolt. Tensile test was conducted to evaluate the effect of the environmental factor on bolted joints. As a result of tensile tests, decrease of clamping force subjected to increase of torque coefficient brings about the early slip which affects the life safe performance of steel structure.
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