When using the detachable expansion bolt, first place the screw into the concrete pillow hole, and then insert the expansion sleeve along the screw in turn, so that the lower end of the boss at the top of the expansion sleeve contacts the upper plane of the hole, and the nut is screwed and the expansion sleeve After the top surface contacts, continue to screw the nut to move the screw up and the expansion sleeve to open. Due to the friction between the expansion sleeve and the concrete pillow wall, the screw is fixed on the concrete pillow. After a certain torque is reached, the nut is unscrewed, the fastener is fastened, and then the nut is tightened, thus achieving the purpose of securing the fastener. . When it is necessary to remove the detachable expansion bolt, simply remove the nut and the fastener, hit the head of the screw, and drive it into the concrete bolster hole, and take out the expansion sleeve and the screw respectively.
The force calculation of the detachable expansion bolt is taken as an example of the <24mm spiral spike used in the sleeper. The force of the screw is analyzed: (1) The axial force of the screw is calculated according to the force of the bolt: M=KNd: M torque, take 150Nm (refer to 5 railway line maintenance rules 6); K torque coefficient, take 0119; N bolt axial force; d bolt without thread diameter, take <24mm.
N=M/(Kd)=150/(0.19@24@10-3)=3219kN According to the basic knowledge of 5 railway track, the maximum axial force of the spiral spike is N=100kN. Calculated below In the above, we study the stress state of the screw, expansion sleeve and concrete hole wall based on N=100kN.
(2) Take the middle section of the screw, expansion sleeve and hole wall as the research object, and analyze the force condition: the force of the detachable expansion bolt is indicated by the force of the 1 screw cone. (b) The following simultaneous equation can be obtained: 2P1sinA1+2P2cosA1-N=0P2=fP1 where: N-bolt axial concentrated tension, take 100kN; P1 expansion sleeve acts on the screw; P2 expansion sleeve acts on the screw; A1 lower half of the screw Taper, take 4153b; f friction coefficient between steel, take 0115.
Substituting the parameters: 2P1sin4.53b+1cos4153b-100=0 solution: P1=21818kN; P2=3218kNo expansion sleeve force (c) can be obtained as follows: P1cosA1+P2sinA1-P3cosA2+P4sinA2=0P1sinA1+P2cosA1 -P3sinA2-P4cosA2-N/2=0 In the formula: P3 concrete hole wall acts on the expansion sleeve; P4 concrete hole wall acts on the expansion sleeve; the outer taper of the A2 expansion sleeve is 1167b.
Solution: P3=215.4kN; P4=-6.3kN Calculate the side area of ​​the expansion sleeve acting on the concrete hole wall and the upper arc length of the compressive stress expansion sleeve is 65mm, the lower arc length is 50mm, and the height is 120mm. The area of ​​force (approximating isosceles trapezoid) is: S=0.5@(50+65)@120=6.9@10-3m2 The compressive stress R of the expansion sleeve on the concrete wall is: R=13/S=31.2MPa concrete The strength of the pillow is generally not less than 60 MPa, and the reserved hole in the reserved hole of the concrete ó, ó type concrete pillow contains the annular force rib, so the force of the expansion bolt on the concrete bolster wall does not cause damage to the concrete bolster.
The test position of the detachable expansion bolt is on the southern end of the K425+543 bridge on the Jinpu line. The section uses 60m/m 25m standard rail, J-2 concrete pillow and elastic strip fastener. Test the position where the representative positive rail has a joint. Three sets of 24mm normal rail expansion bolts were installed at the joints, and the installation torque was 180Nm. After three times of disassembly and inspection, no cracks were found on the concrete pillow wall, and the bolt torque values ​​did not change.
The detachable expansion bolt is a good fastener that can stabilize the railway line concrete bolster. It can completely replace the sulfur anchoring spiral spike and can be used for a long time. It has many advantages over sulfur anchored spiral spikes.
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