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Repair of pier cylindrical rubber fender fixing bolts
- 2019-04-23-

The fender is anchored in the iron card nostril on the ship's bank wall, and the card nose is consolidated by four Q235 steel M30 bolts. The card nose was caused by the collision of the ship due to the sudden collapse of the ship's wall, which caused the bolt to break and be destroyed. This article introduces a simple and easy way to repair bolts.


First, the repair plan

The general rule of repairing broken bolts: two bolts of butt weld fracture or buried from the head. Obviously the site can only adopt the latter to stop repairing.


Bolt

The bolt specification model adopts this plan, that is, the M235 bolt made of Q235 steel, and the buried length is the same as the hole depth. In order to bond and secure the filler in the bolt hole, the appearance is processed into fine rib.

2. The aperture is long.

(1) Aperture

Aperture credential bolt diameter and packing thinness are certain. When the packing thinness t is 5 mm, the pore diameter D=D screw 2t=30 5 2=40 mm. The aperture is as small as possible and is round and round.

(2) Hole depth

Calculation formula of hole depth L

The external tension of the N-bolt outside the model, according to the specifications and models of the bolts of the plan, and the degree of the hanging of the fender, etc. to estimate the external force received by the fender bolt (the ship's crushing force takes the impact force) and lost; The filler takes the concrete hole wall, and the packing strength between the bolts is taken from the packing.

3. filler

The filler adopts a sulfur mortar which is fastened by agglomeration and softened at a bond strength. Its component ratio is sulfur: cement: yellow sand: white wax = 1:0.4:1.2:0.003. The example delineates the bond strength between the concrete wall and the bolt of the sulfur mortar. The difference between the bolts and the bolts is not less than 4 MPa and 11 MPa. The former is smaller than the latter, and the sulphur mortar is taken from the concrete wall and the bolts are loosened before the bolts are taken. Thus, take (= 4MPa:

4. External force

The bolt force diagram is shown in the drawing.

The force diagram is used to calculate the disintegration force caused by the external force and the fair force without each bolt, and then stop the shear and tensile strength calculation, and use the shear strength as the premise of restraint, and calculate the external force. Consider the safety factor of 1.5. The ship is squeezed without an average factor L 3. Calculate N: ax, substitute (11 type, lose L > 302mm take the hole depth L = 320mm



Two, true

1. Wild hole

The wild hole is made by hammering steel, and after the hole is formed, it is necessary to clean the hole. Holes should avoid the main ribs.

2. Buried section

After the hole is formed, the anchor bolt should be buried in time to avoid the trend and pay attention to the low bond strength in the infusion hole. The sulphur sand is added - it must be full, and the sulphur mortar must be used up within 5 minutes after mixing.



Third, repair motivation repair

If the maintenance method is buried according to the site premise, it will be set as three sets of M30 bolts with a depth of 200mm. With the oil pump, the jack is connected to the top of the jack, and the bolt is loosened to pull out the instantaneous oil pump pressure gauge reading to calculate the bond strength. After the maintenance test:

   

Tensile strength N = 6 sticky DL = 297571.7 (N) > N: ax, both meet the plan and sample requests. In addition, when the bolt is not dialed, the bolt is sulphur-slurry and wrapped tightly without any looseness, which proves the bond strength between the concrete hole and the sulfur mortar under the bond strength.

The practice proves that adopting the repair plan of bolting from the beginning, the craft is reliable, the old one is expensive, the operation is simple and simple, and it is simple and feasible.