Precautions for bridge bearing replacement and jac

2022-07-22
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Precautions for bearing replacement construction

(1) different jacking methods should be adopted for different forms of bridges. For the section form composed of T-beam or I-beam, the base plate can be placed under the beam body and lifted directly by Jack; However, when jacking up hollow slabs and box girders, attention must be paid to the jacking parts to avoid directly jacking up the bottom of the beam body, and it is easy to choose the two ribs and the web of the box girder to prevent damage to the beam body

(2) due to the influence of the self weight of the side beam itself and the ancillary facilities of the bridge deck (such as guardrails and connectors at the split joint), there is a large difference in the jacking force between the side beam and the middle beam. During the jacking, it must be controlled by both pressure and stroke, and the stroke is the final control. Avoid shear failure of bridge deck due to uneven jacking

(3) strictly control the jacking height of the beam body to avoid damage to the bridge deck and ancillary facilities caused by too high jacking height

introduction to the jacking construction steps for bearing replacement

(1) before jacking, the bridge width under construction should be temporarily closed to avoid accidents in the construction process

(2) after the preparation work is completed, under the unified command of the project leader, fourteen jacks are lifted at the same time. Press the jack, hold the beam bottom, observe the change of the dial gauge reading, the dial gauge starts to rotate regularly, and record the initial reading. The lifting speed of the control beam is controlled according to the 2 # beam. Every 2mm of lifting is a procedure. After each lifting procedure is completed, the monitoring personnel will uniformly complete the reading. If the displacement change between the two adjacent main beams is more than 0.1mm due to uneven lifting, local jacking pressure adjustment will be carried out. After the adjustment, the next process of lifting will be carried out until all the lifting is in place, and the support can be taken out smoothly. During the whole jacking process, the main beam, bridge deck and auxiliary facilities must be carefully observed, and the jacking shall be stopped immediately in case of any abnormality

(3) after jacking in place, place pre prepared wedge sleepers and prefabricated steel plates at the bottom of the beam for temporary support pads. The support pads are required to be firm and reliable, and the jack cannot be loosened during the support pad process

(4) after taking out the old support after the support pad is completed, carefully remove the rust and dirt on the stainless steel plate at the bottom of the original beam, apply a layer of lubricating grease, and then use a level gauge to check whether the surface of the pad stone under the support is flat and can meet the installation requirements. Polish and remove the greasy dirt and laitance on the surface of the pad stone. Before placing the new bearing, cross positioning shall be carried out at the original bearing position and the surface of the new bearing to ensure the accurate position of the bearing after replacement

(5) for the bearing bias caused by the improper installation of the beam body or the uneven bottom surface of the beam, the structural glue can be used to partially fill the void part to ensure the full section compression of the bearing

(6) before installation, fill the silicone grease in the oil storage tank on the surface of the tetrafluoro plate in the tetrafluoro plate support to ensure that the surface of the tetrafluoro plate and the stainless steel surface are clean without damage and galling; At the same time, install the dust cover of the support as required

(7) when the support is replaced and the main beam is in place, it should also be distributed. First remove the temporary support at the bottom of the beam, and then drop the beam in order to put it in place. Pay attention to loosen the jacks crosswise, not at the same time, so as to prevent damage to the bridge deck or crushing individual jacks

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