Anchor bolts are classified into fixed anchor bolts, mo […]
Anchor bolts are classified into fixed anchor bolts, movable anchor bolts, expansion anchor anchor bolts and adhesive anchor bolts according to their purpose. In addition, it is divided into L-shaped embedded bolts, 9-shaped embedded bolts, U-shaped embedded bolts, welded embedded bolts, and bottom plate embedded bolts according to different shapes. However, no matter how various types of anchor bolts are, the final construction is to be completed. For anchor bolts that do not require strict determination of the tightening force, the tightening method generally uses ordinary wrenches or pneumatic wrenches, electric wrenches and hammer impact tables. Head wrench etc. The anchor bolts that require determination of the tightening force can generally be tightened by the following methods.
Method of fixing anchor bolts
1. Constant torque method: Convert the specified tightening force into tightening torque. The conversion formula is as follows: M= KDP/1000, M-bolt tightening torque, in Nm; K- tightening torque coefficient, thread contact surface , When the friction factor of the contact surface between the nut and the connected part is both 0.15, K takes 0.2; D-the nominal diameter of the bolt, in mm; P-the specified bolt tightening force, in N. According to the calculated tightening torque, a fixed torque wrench can be used for tightening. This method is widely used, but due to the existence of friction torque, the error is large, and it cannot be used for the fastening of larger bolts.
Second, the nut is screwed into the angle method: after tightening the nut to eliminate the gap, mark the end surface of the nut and the anchor bolt. Then heat the bolt to extend it, and then screw the nut into a certain angle. After the bolt cools down, the required tightening force is obtained. The heating temperature of the bolt and the multi-threading angle of the nut can be calculated according to the following formula: t= P/AαE + t0, θ= PL/ASE*360 where t-bolt heating temperature, in ℃: P-bolt tightening force , The unit is N; A-the cross-sectional area of the stretched part of the bolt, the unit is m㎡.