What is the torque coefficient of steel structure bolts?
? Answer: In steel structure bolt connection, the proportional coefficient between the fastening torque applied to the nut and the axial pre-tightening force (fastening axial force) introduced by the bolt is called the torque coefficient of steel structure bolt.
? Torque coefficient is a general concept, and different objects have different torque coefficients. For example, the torque coefficient k of the bolt directly reflects the coefficient between the torque and the axial force in the process of bolt tightening, which depends not only on the friction coefficient of the friction surface, but also on the geometric conditions of the threaded connection pair. For a specific ideal threaded connection pair, when the friction coefficient is determined, the torque coefficient is also determined. However, there are inevitably manufacturing errors in the actual threaded connection, and sometimes there are even defects such as thread scratch and corrosion. At this time, even if the friction coefficient of several bolt connection pairs remains unchanged, the torque coefficient will inevitably have some dispersion. Rather than a constant corresponding to friction. In extreme cases, when interference occurs, although the tightening torque is large enough, the axial force of the bolt may be small. Generally, the value of k varies within the range of 0. 100-0.450 according to the thread connection mode, surface friction condition and thread manufacturing quality.
How to calculate the torque coefficient of high strength bolts in steel structure?
? A: TC =1.05kpcd.
? Tc-construction torque (n m);
? K refers to the average value of torque coefficient of high-strength bolt connection pair;
? PC—— Pre-tightening force (KN) of high-strength bolt structure;
? D— screw diameter of high-strength bolt (mm);
? The torque wrench used before the construction of steel structure high-strength bolts must be calibrated before use, and its torque error shall not be greater than 5%. It can only be used after it is qualified. The torque error of calibration torque wrench should not be greater than 3%.
? Matters needing attention in the construction of steel structure high strength bolts
? Before the construction of high-strength bolts for steel structure, the torque coefficient of high-strength bolt connection pairs for steel structure should be checked according to the factory batch. Each batch of 8 sets, the average value of 8 sets of torque coefficient should be in the range of 0.1/kloc-0 ~ 0.150, and its standard deviation should be less than or equal to 0.0 10. The reinspection method of torque coefficient shall be implemented according to GB50205 Code for Acceptance of Construction Quality of Steel Structure Engineering. After the test, the installation of high-strength bolts of steel structure should be carried out in a short time.
? The above-mentioned torque coefficient of high-strength bolts for steel structures only applies to GB/T 1228- 1230? Steel structure large hexagon-head bolt connection pair, and the technical point of GB/T 3632-2008 steel structure torsion shear bolt is to tighten the axial force, which we put in other chapters of Ning high strength.