Laminated Rubber Bearing construction scheme

Laminated Rubber Bearing preparation for installation
1. Laminated rubber beam mobilization inspection
(1) Upon mobilization of the Laminated rubber beam, the bearing shall be checked for the presence of the manufacturer’s trademark or permanent mark; Check whether the specification, size, model, appearance and other indicators of the bearing meet the design and specification requirements. The steel plate under the bearing shall be notched with 5mm deep grooves at the position where the bearing is placed, and the bearing shall be placed at the notch to increase the anti-sliding bearing capacity of the bearing. In order to prevent the PTFE sliding plate support from sliding out of the stainless steel plate, groove shall be made at the steel plate on the support, and the stainless steel plate shall be anchored in the groove to increase the seismic performance. The surface of the stainless steel plate contacting with the PTFE plate shall be free of damage and galling, so as to avoid increasing the friction coefficient and damaging the PTFE plate.
(2) The samples shall be sent to the qualified testing unit for inspection according to the mobilization batch, quantity and model.
2. Technical preparation
(1) Carefully review the installation drawings of the lagged rubber beam, prepare the construction scheme, and organize technical personnel and construction and installation workers for technical disclosure and pre-job training after approval.
(2) The bearing pad stone shall be inspected and accepted according to the requirements. The allowable error requirements for the bearing pad stone are: axis offset 5mm, top surface elevation 2mm, height difference of four corners of the top surface 1mm. Those not meeting the requirements shall be handled until they are qualified.
(3) Substructure and upper beam and slab of the bridge shall be accepted in three stages, and relevant acceptance preparations shall be made in advance.
(4) Surveying and setting out: mark the center lines of the bearing positions on the bearing pad stone and the bearing according to the requirements of the design drawings, so as to ensure the accurate positioning of the bearing.
(5) Carry out sampling test of various raw materials and design the mix proportion of epoxy mortar.
3. Material preparation
（1）Laminated rubber bearing： Packing list, product certificate and detailed rules for bearing installation and maintenance shall be provided for mobilization. Specifications, quality and relevant technical performance indexes shall comply with the provisions of the current highway bridge bearing standards and meet the design requirements.
(2) Preparation of epoxy mortar materials: dibutyl ester, ethylene diamine, epoxy resin, xylene, fine sand. Except fine sand, other materials shall be provided with certificates and operation instructions. Variety and quality of fine sand shall comply with relevant standards.
(3) Welding electrode: the welding electrode shall be provided with certificate of quality when entering the site. The type of welding electrode selected shall be compatible with the metal strength of the base metal. The type, specification and quality shall comply with the provisions of the current national standards and meet the design requirements.
(4) Other materials: acetone or alcohol, silicone, etc.
4. Preparation of machines, tools and equipment
(1) Main machinery: transport truck, generator, electric welding machine, truck crane, water truck, water pump, etc.
(2) Tools: wrench, spirit level, iron chisel, small spade, iron pot, spade, iron trowel, wood float, rubber hammer, wire brush, steel wedge, fine screen, broom, small line, plumb bob, etc.
(3) Measuring equipment: total station, level, steel ruler, etc.
(4) Test equipment: universal testing machine and press machine.
5. Site preparation
(1) The concrete surface on the pier and abutment where the bearing is placed shall be flat, clean, dry and free of floating sand, so as to ensure uniform pressure over the whole area.
(2) Carefully check all pad stone surfaces, top surface elevation of pad stone, pier and abutment (including pad stone) axis, elevation, etc. and ensure they meet the design requirements.
(3) Ladders for upper and lower piers and abutments have been erected in place.
Installation and construction of aminated rubber beam
1. Construction process flow
Check the bearing → measure and set out → place the bearing → install the beam and slab → comprehensively check the bearing
2. Installation of ordinarylagged rubber beam
Transport the rubber bearing to the pier top and place it on the pad stone on the pier top according to the lofted cross center line. It is only required to overlap the bearing center with the pad stone center line. Repeatedly measure whether the cross center of the bearing coincides with the pad stone cross center and whether the elevation of four corners meets the specification requirements. Install the C steel plate at the main beam position of the middle cross beam bottom on the support after passing the inspection. The door reinforcement on the C steel plate shall be welded in advance. The installation position of C steel plate shall be accurate and can be measured with a straight steel ruler for adjustment. Each support of the same beam shall be placed on the same plane to avoid eccentric compression, uneven support and individual separation.
3. Installation of Ptfe Rubber BEARING Pad
First, mix epoxy resin mortar. The preparation of epoxy resin mortar shall be carried out strictly according to the mix proportion issued by the site laboratory. After drying the fine sand, put the fine sand, epoxy resin, dibutyl ester and xylene into the iron pot for heating and mixing evenly; Before bonding the steel plate, put the ethylenediamine into the mortar and mix it evenly. The ethylenediamine is a curing agent and shall not be placed too early or too much, so as not to affect the bonding quality due to early solidification of the mortar. Because the ethylenediamine is solidified too fast in summer, it is recommended to use triethylenetetramine in summer and ethylene diamine in spring and winter. Transport the epoxy resin mortar and Ptfe rubber beam pad to the pier and abutment top. First smear a layer of epoxy resin mortar on the treated pad stone top. The thickness of epoxy resin mortar shall be uniform. Then, place the lower steel plate of the support on the Ptfe rubber bearing pad stone. The lower steel plate is bonded with epoxy resin mortar. The cross center line of the lower steel plate overlaps with the pier and abutment top pad stone according to the cross center extension line that has been set out. Then, install the Ptfe rubber bearing pad. Before installation, carefully scrub the relative sliding surfaces with acetone or alcohol. Other parts of the support shall also be cleaned. After cleaning, fill the oil storage tank of the PTFE plate with silicone lubricant and keep it clean to reduce the friction coefficient. The Ptfe rubber bearing pad must be carefully installed. Place the support in the notch and put it in place on the lower steel plate according to the cross center line that has been set out. Only overlap the cross center of the support with the cross center line of the lower steel plate. Repeatedly measure whether the center of the support coincides with the center of the pad stone and whether the elevation of the four corners meets the specification requirements. Install the upper steel plate on the support after passing the inspection. Note that the installation position of the upper steel plate shall be accurate, and use a straight steel ruler to measure and adjust it in place. The exposed steel plates of Ptfe rubber bearing pad shall be coated with anti-rust paint.
4. Installation of beam and slab
For the installation of precast beam slabs, the design bearing centerline at the discontinuous end of the beam slab shall coincide with the lateral centerline of the bearing, and the longitudinal axis of the beam slab shall be parallel to the bearing centerline. When the beam body is transported to the site, first check whether there is cement paste on the embedded steel plate at the bottom of the beam, and then check whether the edge of the steel plate at the bottom of the beam body is flat and timely treated. During beam falling, in order to prevent longitudinal and transverse sliding between the beam and Ptfe rubber beam pad, wooden triangle cushion blocks shall be used for positioning on both sides of the beam body, and the beam shall be removed after the completion of beam falling. In order to accurately lower the beam, when erecting the first span beam plate, mark the longitudinal position center lines of the two supports at the bottom of the end beam with an ink marker, and mark the straight lines along the longitudinal position center lines of the two supports on the elevation of the beam end; The beam shall be placed in line with the centerline of pier and abutment. For the following several spans, the beam can be dropped based on the first span beam. The beam shall be dropped stably to prevent eccentric compression or initial shear deformation of the support. When the precast beam slab is not in place accurately or the beam slab is not closely contacted with the support, the beam slab must be hoisted and re-positioned to eliminate the gap, and the beam slab shall not be moved with crowbars. Generally, the top surface of the rubber bearing shall be kept horizontal after the beam is installed. In order to ensure convenient replacement of Ptfe rubber beam pad, the embedded steel plate at the beam bottom and the steel plate on the support shall be welded in sections, with a thickness of 8mm and a length of 5cm for each weld. During welding, the debris around the support shall be cleaned, and the rubber block shall be covered with flame retardant materials to prevent the support from being burned, and the steel body from being heated to burn the concrete. When the beam body has a longitudinal slope, the steel plate can be processed into a wedge shape with corresponding slope for adjustment, so that the contact surface between the Ptfe rubber beam pad and the stainless steel plate is kept horizontal. The leveling wedge steel plate shall be installed in the beam plant. The wedge steel plate and the embedded steel plate at the beam bottom shall be bonded with epoxy resin. After 24 hours, the surrounding shall be welded with the embedded steel plate at the beam bottom in sections. The weld joint shall be 8mm thick and each weld joint shall be 5cm long. When welding the connecting steel plate, pay attention not to burn the concrete. The cross slope of hollow slab shall be adjusted by wedge-shaped steel plate with the same method).
5. Installation of dust cover
Install the dust cover. Ptfe rubber bearing pad must be provided with a dust cover. The dust cover is made of 5mm thick rubber sheet or nylon fiber cloth, and the four sides are pasted on the upper steel plate with epoxy resin.
6. Completely check the bearing
The Ptfe rubber beaming pad shall be comprehensively inspected after the conversion of the beam-slab system is completed. If some supports are found to be partially disengaged, subject to large initial shear deformation, serious eccentric pressure, partial compression, abnormal lateral bulge, etc., the causes shall be found out and timely adjusted. Generally, jack can be used to jack up the beam end, and a layer of epoxy resin mortar shall be paved on the upper and lower surfaces of the bearing, and the beam shall be dropped again. Under the action of gravity, the upper and lower surfaces of the bearing shall be parallel and closely contacted with the beam bottom and the top surface of the pier; At the same time, the supports at both ends of a beam shall be in the same plane, and the longitudinal inclination of the beam shall be controlled so that the support does not produce obvious initial shear deformation.
Quality Control and Inspection
1. Ptfe rubber bearing pad stone shall be free of exposed rebar, cavity, honeycomb, pitted surface and any crack.
2. Check the raw materials before construction, and keep the certificate records.
3. When the bearing is delivered to the site, it must be carefully checked, the specification and quality shall meet the design requirements, the product qualification certificate shall be complete, and the bearing shall be checked for any damage during transportation. The bearing shall not be used if it is unqualified.
4. Check whether the Ptfe rubber bearing pad is filled with silicone oil. It is forbidden to replace silicone oil with lubricating oil.
5. Check whether the bearing has excessive compression deformation, and whether the rubber plates between the stiffening steel plates of the bearing are uniformly convex and normal.
6. The warehouse for storing Ptfe rubber bearing pad shall be dry and ventilated. The supports shall be stacked in order and kept clean. It is forbidden to be mixed with acid, alkali and oil. Organic solvent shall be in contact with the ground and shall be at least 1m away from the heat source.