Bearing replace

bearing replace

time:2018-12-06 source:维特编辑部browse:158

桥梁支座更换

In recent years, China's bridge construction has made universally recognized achievements. However, with the rapid growth of the national economy and the development of the transportation industry, a large number of Bridges are in use with the growth of the service life, and even some newly put into operation bridge span structure damage problems have become increasingly prominent, the bridge reinforcement task is very heavy.
Due to the different forms of bridge structure, bearing replacement has certain technical difficulties, making the construction of a certain risk, the need for professional teams, in order to prevent damage to the bridge structure.
Bridge support is an important component connecting bridge superstructure and substructure. It can be said that the throat of a bridge is where the disease occurs, which will affect the service life and traffic safety of the upper and lower parts of the structure.
At present, almost all newly-built highway Bridges are supported by rubber bearings.
Especially highway bridge, rubber support, the amount of large, many diseases, frequent accidents, support disease treatment and replacement is urgent.
The following is a brief introduction of bearing replacement technology combined with engineering examples
Bridge support replacement
I. analysis of disease symptoms and causes of bearing

Rubber support under pressure is not uniform, some of the support partially empty, some even completely empty, do not participate in the structure of the force, resulting in other support pressure increase, large deformation.
The rubber support cracked.
There are many reasons for rubber bearing cracking, which can be divided into two categories: one is the quality problem of rubber bearing itself.
Second, the construction and installation of the problem.
Rubber support shear deformation, rubber support shear deformation is too large, or even cracks, the main reason for this phenomenon is that the initial shear cut shape of the support installation is too large.
Support cushion stone height is not enough, with ordinary mortar leveling, resulting in mortar crushing, the upper support basically does not bear the upper load, some of the upper support empty, but with mortar seal coating gap
There are sundries on pier platform cushion stone, such as concrete template, soil, cause the cause of this phenomenon has: pouring wet joint leakage slurry, telescoptic joint before installation into the sundries not cleaned, temporary fixed facilities have not been dismantled, some sundries on pier platform will pollute the rubber support, some surrounded the support, affect the support play a normal role.
The elevation of the pier top surface that installs support exceeds bid, in order to maintain beam bottom elevation and leave groove of support place make do with.
The rubber support of teflon slide plate is shearing deformation and cracking.
The main cause of this phenomenon is in the process of installation method is not correct, such as: no clean bearing parts, four fluorine board with stainless steel plate between the contact surface into the sediment, stainless steel plate surface protective film is not clear, four fluorine board did not inject silicon fat or oil instead of silicone fat, bearing installation deviation is too big, even some four fluorine board bearing installed upside down, the set of stainless steel plate in pad on the stone.

Bridge support replacement
Ii. Main replacement plan

1. Flat jack method
The ultra-thin hydraulic jack is placed in the narrow space between the main beam and the cover beam, and the beam body is directly jacked up. The rate of rise of the beam body is observed by the dial meter, so as to ensure the uniform and synchronous lifting of the beam body across the bridge.
This method is the most widely used jacking method at present.
2. Saddle bracket method
The bridge pier itself is used as a support to set up a bracket on the cover beam, which is designed as a "saddle type bracket", and jacks are placed to lift the beam body.
3. Pillow full support method
Set sleepers on the ground. On the basis of the sleepers, set full or partial wooden supports to the bridge beam body, and place the jacking beam body of the jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking jacking.
4. Saddle bracket method
The bridge pier itself is used as a support to set up a bracket on the cover beam, which is designed as a "saddle type bracket", and jacks are placed to lift the beam body.

Iii. Implementation of the plan

1. Stowage calculation and stowage vehicle layout
In order to ensure the overall force of a hole bridge and synchronous jacking, the weight of the superstructure such as bridge deck, middle beam, side beam and guardrail should be calculated in accordance with the design file first, and then the load distribution should be carried out according to the principle of overall weight balance. Usually, vehicles are selected to evenly arrange the load distribution to ensure the force balance in the jacking process.
2. Main construction materials and equipment
Machine name: generator set, welding machine, hydraulic station, one-way ultra-thin jack, dial indicator, manual jack, loading truck, lifting basket rack, gas cutting equipment, hydraulic distribution equalizer, high-pressure distribution pipe.



Q: what is the correct position to replace the bridge support?

Answer: the correct position of the bridge support makes the bridge support and supporting stone be in place accurately according to the design requirements.
When the girder falls, the longitudinal axis of the t-beam should coincide with the center line of the support;
The longitudinal axis of plate girder and box girder is parallel to the center line of support.
To fall beam accurate, when crossing plank beam or box girder the first, can delimit the cross position center of two supports in beam bottom, mark the lead straight line of the position center line of two supports on beam end elevation, when falling beam make it coincide with the position center line on pier.
Subsequent spans may be carried out in accordance with the first span beam as a reference.
In the beam fall beam to be stable, to prevent pressure deviation or the initial shear deformation, you can refer to the railway bridge plate rubber support specifications table.
When installing t-type bridge, if the rubber support is wider than the beam bar bottom, the reinforced concrete pad or thick steel plate which is larger than the support should be added between the support and the beam bar bottom to make the transition layer, so as to avoid the local part of the support under pressure and form a stress concentration.
Reinforced concrete pad or thick steel plate shall be bonded with epoxy resin mortar and the bottom of the beam reinforcement.
After falling the beam, the top surface of the support and the beam generally remain horizontal.
Prestressed simply supported beam whose support top surface can be tilted later;
The support top surface of a non-prestressed beam may lean forward slightly, but the inclination Angle shall not exceed 5".
The piers, platforms and beams with plate-type rubber supports shall be made on the construction site by using metal wires instead of wooden models with pull rods, and the surfaces in contact with concrete shall be smooth and smooth.


Q: how to maintain bridge supports after replacement?

Answer: keep the support clean, check every quarter, clean every six months, remove snow and ice in winter, ensure beam span expansion.
The rolling surface of the rolling support should be regularly coated with a layer of lubricating oil (generally once a year), before applying oil, the rolling surface should be wiped clean.
In order to prevent rust, all parts of the support except the steel roller and rolling surface, the rest should be coated with paint protection.
Check the firmness of bolts for the fixed support, the support plate should be flat and tight, and tighten the joint bolts in time.


Q: what is the basis of bridge support replacement?

Answer: the bridge support is by the multilayer rubber and the steel plate vulcanization adhesive becomes, it has the enough vertical steel degree, can transmit the superstructure the counterforce reliably to the pier;
It has good elasticity to adapt to the rotation of the beam end and large shear deformation capacity to meet the horizontal displacement of the superstructure.
In plate rubber bearing surface sticky after a 1.5 mm - 3 mm thick layer of teflon plate, can be made into ptfe sliding plate rubber support it in addition to the vertical stiffness and elastic deformation, can withstand the vertical load and to adapt to the beam end rotation, due to the low friction coefficient of ptfe plate, can make the beam end in four fluorine board free sliding surface, the horizontal displacement is not restricted, especially suitable for medium, xiao-he load, the displacement of the large bridge.


Q: what are the recommendations for bridge support replacement?

The arrangement of bridge supports is mainly related to the structural form of the bridge.
Generally, the following basic principles need to be taken into account in the layout of support:

When the superstructure is a spatial structure, the support should be able to adapt to the deformation of the bridge both in the direction of the bridge (X direction) and the direction of the transverse bridge (Y direction).
Support must be able to reliably transfer vertical and horizontal counterforces;
The support should make the longitudinal displacement, transverse displacement and longitudinal and constant rotation Angle caused by the deformation of beam body as free as possible.
Railway Bridges must usually have a fixed support on each beam body;
When the bridge is located on the ramp, the fixed support should be generally located on the abutment in the downhill direction.
When the bridge is on a flat slope, the fixed support should be placed on the front abutment of the main driving direction.
Fixed support should be set in a place with a large support reaction;
Several supports on the same pier should have similar rotational stiffness;
The possibility of height adjustment of continuous beam should be considered when bearing subsidence may occur.

In a word, the principle of arrangement of bridge supports is to facilitate the transfer of the reaction force of the supports and to make the supports fully adapt to the free deformation of the beam body.

Q: what is the reference standard for replacement of bridge bearing with basin bearing?

A: the following standards contain provisions which, by reference in this standard, constitute provisions of this standard.
At the time of publication of the standard, all the editions shown are valid.
All standards will be revised and the parties using this standard should explore the possibility of using the latest version of the following standards.

GB 527-83 general requirements for physical test methods for vulcanized rubber

GB/T 528-92 determination of tensile properties of vulcanized and thermoplastic rubber

Gb700-88 carbon structural steel

GB 1033-86 methods of test for plastic density and relative density

GB/T l039-92 general principles for testing mechanical properties of plastics

GB/T 1o40-92 methods of test for tensile properties of plastics

Shape and position tolerances are not specified

GB/T 1682-94 determination of low temperature brittleness of vulcanized rubber -- single specimen method

GB/T 18o4-92 general tolerances linear dimensions with unmarked tolerances

GB 2041-89 brass sheet GB/T 3280-92 stainless steel cold-rolled sheet

GB 3512-83 rubber - hot air ageing test method

GB 6031-85 international determination of hardness of vulcanized rubber (conventional test method 30-85irhd)

GB 7233-87 ultrasonic flaw detection and quality grading methods for steel castings

GB 7759-87 determination of the permanent deformation of vulcanized rubber under constant deformation compression at room temperature and high temperature

GB 7762-37 static tensile test method for ozone resistance of vulcanized rubber

GB/T 8923-88 steel surface corrosion grade and rust removal grade before coating

GB/ 11352-89 carbon steel castings for general engineering use

JB/T 5943-91 general technical conditions for welding parts of construction machinery

HG/T 2502-93 5201 reference standard for basin-type bearing for replacement of bridge bearing with silicone grease.


Q: how to test the performance of the support before replacing it?

Answer: the exterior dimension that basin type supports asks, the compressive stress that the tetrafluorine board of basin type supports allows is 30mpa.
The minimum thickness shall be 7mm, the maximum thickness shall not exceed 8mm, the thickness of the teflon plate embedded in the middle plate shall not be less than 4mm, and the height of the protruding middle plate shall not be less than 3mm.
Detection of vertical bearing capacity of basin bearing, vertical compression deformation, deformation degree of basin outer diameter and variation of bearing height;
Horizontal bearing capacity detection, detection of upper and lower support plate deformation;
Corner, the change of the four fluorine board and just a damage, rubber extrusion, trial design on rubber bearing the vertical load first, then applying horizontal force with a jack and recorded by dedicated pressure sensor horizontal force size, rubber bearing a sliding occurred namely stop applying horizontal force, thus calculate the initial friction coefficient of rubber bearing.
Basin type rubber support is mainly composed of pressure rubber plate and steel components, the basin type rubber support test items include the test of rubber plate, and the test of steel components, pressure rubber plate test items have: rubber physical and mechanical properties and appearance size.
There are mainly hardness, brittle temperature, tensile strength, tensile elongation at break, constant compression and permanent deformation, ozone aging resistance test and hot air aging test (rubber strength, elongation and reduction rate and hardness change), as well as the determination of adhesive peel strength of rubber and steel plate.
Rubber board appearance size, rubber board appearance must not have bubbles, magazines, uneven, four side cracks, steel plate exposed, dropped pieces, crack, mechanical damage, steel plate and rubber board bonding cracking or peeling phenomenon.


Key words: bridge bearing replacement plate bearing replacement replacement bridge bearing replacement
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