The expansion joint of the bridge deck does not run through
- Phenomenon: the bridge abutment and beam end and the expansion joints between the joints (the bridge deck continuous holes called – joint). It often occurs on the side wall of the bridge abutment, the ground burden, and the anti-collision guardrail. Railing handrails at the expansion joints continue to open the common disease.
- Hazards: due to expansion joints are not fully penetrated. Caused by unbroken bridge abutment side wall, ground burden, guardrail, railing handrail cracks.
- Reason analysis: the main superstructure of the bridge is completed. When working on ancillary facilities. The technical briefing did not provide the requirements for leaving joints, or the construction operator did not understand the role of expansion joints, resulting in the above problems.
- Preventive measures.
(1). When constructing accessory structures, the technical briefing should emphasize that the expansion joints should be completely disconnected at the bridge deck. Make expansion joints in the bridge transverse completely through.
(2). Improve the technical quality of the operator.
(3). Construction of accessory structures, pay attention to the expansion joints are through inspection.
- Governance: in the part of the bridge abutment side wing walls and ground burden, railing for local rework. Leave through joints.
Expansion joint installation and use quality defects
- Phenomena.
(1). The water channel under the expansion joint falls off.
(2). Toothed plate expansion joints and rubber expansion joints with embedment elevations not in accordance with design requirements.
(3). The weld of the embedded steel reinforcement of the main beam with the joint angle and the underlying steel plate is not secure and distorted.
(4). The concrete of the concrete protection zone of the expansion joint is broken, causing the expansion joint to drop anchor. 2.
- Hazards: the water channel falls off and causes water leakage at the expansion joint; the installation elevation does not meet the weld deformation and distortion. This causes the expansion joint and the bridge deck to be uneven, resulting in jumping; the weld is not secure, and the concrete protection belt on both sides of the joint is broken causing premature damage to the expansion device.
- Cause analysis.
(1). Water guide U-channel anchor, not firmly glued, resulting in water guide fall off.
(2). Anchor plate of toothed plate expansion joints. The elevation of the joint angles of the skateboard expansion joint, the joint beam of the rubber expansion joint and the embedded parts of the main beam are not checked before welding.
(3). The surface of the welded parts of the expansion joint is not rusted, and the length and height of the welded joints are not enough when welding. Caused by welding is not strong; welding without skip welding, resulting in large deformation of weldments.
(4). Concrete protection zone is not poured with expanded concrete, and vibrating is not dense.
- 4. Prevention and control methods.
(1). Take effective measures to anchor or paste the water-conducting U-shaped channel.
(2). Thoroughly remove rust from the surface of the welded parts, spot weld spacing not more than 50cm, control the welding temperature between +5℃ and +30℃, double-sided welding, skip welding, and finally plug welding to ensure small welding deformation and high welding strength.
(3). Weld the anchor plate on the main beam embedment, link angle steel, articulated beam steel parts, to keep the same height on both sides of the seam. and the top elevation conforms to the elevation of the point from the longitudinal and transverse slope of the bridge deck.
Rubber expansion joints, TS joints for rainwater runoff
- Phenomena and hazards: rubber expansion joints and Ts joints, the joints are blocked with leaves and other debris. After the inflow of rainwater on the bridge deck. There is no proper drainage pathway, resulting in rainwater along the burden of diffuse flow. 2.
- cause analysis: design is not perfect, the water in the seam does not drainage pathway. Had to flow from the lowest end of the expansion joint and the burden of the joints.
- Precautions: Before the start of construction, at the drawing meeting. To the design, request the addition of expansion joint drainage design samples to be resolved.
- Governance methods: can be in the water confluence of the low place. Set up a similar housing construction of the water funnel and drop pipe to eliminate water in the joints.
Requirements for bridge bearing installation
Bridge bearings must be designed to be installed in a predetermined position very accurately, the height of the support, tilt and direction, should be very good to meet the design requirements.
In the curve, slope, sloping bridge. Should also pay great attention to the thickness of the support stone. to ensure that after the beam is installed, there are no problems with the pier edge supporting the beam bottom.
The support arrangement also needs to be replaced for the support, leaving enough area and space for the jack, and all steel members on the support must be painted with anti-rust paint to protect them.
Plate beam traverse
- Phenomenon: the span diameter of 6m or less of reinforced concrete plate girder transverse movement.
- Hazards: cause the longitudinal axis of the bridge offset the road axes at both ends. 3.
- Cause analysis: through the bridge caused by the impact vibration of vehicle driving. 4) Precautionary measures: Both sides of the plate girder end set to limit the transverse movement.
- Preventive measures: plate girder end on both sides to limit the transverse movement of the embedded bolt.
Steel support up and down, anchor bolt breakage
- Phenomenon: bridge steel bearing on the hem of the anchor fracture.
- Hazards: Anchor bolt fracture endanger the safety of the steel bearing. 3.
- Cause analysis.
(1). Arc bearing arc surface production rough. Can not ensure normal displacement or arc surface rust, bridge beam expansion when the anchor bolts are sheared.
(2). Bearing construction. Failure to calculate the displacement of the movable support, and failure to set the position of the support swing according to the temperature during construction, resulting in the highest or lowest temperature. Displacement blocking anchor bolt shearing.
(3). The position of the upper pendulum anchor bolt and the bearing bolt hole is wrong, it cannot be installed, and the bolt is injured by hammer.
(4). Precautionary measures.
Ensure that the arc bearing arc surface is smooth to avoid arc surface rusting.
When installing movable bearing. According to the highest and lowest temperature and construction temperature of the maximum difference. To calculate the displacement of the support to determine the installation location.
To ensure that the upper pendulum anchor and bearing bolt hole position is accurate. Make the error reduction, installation smoothly.
- governance methods: support on the pendulum and beam bottom panel angle plate welding to strengthen. Can also be chiseled in pier concrete for replacement.
Uneven installation of steel support, water accumulation
- Phenomenon: bearing installation positioning and poor fastening.
- Hazards: due to positioning, poor fastening, in the vertical load, bearing uneven force on all parts. 2. Extremely easy to produce damage.
- Cause analysis: construction of the pier top surface is not carefully leveled, so that the support pad three bolts under stress.
- governance methods.
(1). Before installation of the support. Carefully check the design drawings marked bearing position and direction, and then after accurate plane and level measurement, marked on the pier face bearing center.
(2). According to the bearing diagram, do the bearing under the pad and anchor bolts of the reserved hole, this time to consider the relationship with the lower structural steel, easy to adjust the installation position. To the hole filled with mortar construction to determine the size of the reserved hole.
(3). installation of steel support, more than the use of pads to adjust the support position, height and tilt, etc.. The liner must be located even after filling mortar can also be removed position, to mortar hardening after quickly removed and set up a reservation hole, temporarily set up a good support, and then from the reservation hole will mortar to the support pad inside.
(4). support bedding stone should be higher than the top surface of the pier 3 ~ 5cm, and will support the platform outside the top surface of the pier made of two-way cross slope, so as to exclude the flow of water in its.
Slab rubber bearing quality defects
- Phenomena.
(1). Plate type rubber bearing rubber or rubber and reinforced steel plate cementation. Shear damage.
(2). beam on the two rubber support compression varies, even individual bearing gap.
(3). The bearing is installed in the bearing groove, after lifting the beam support is compressed, the beam bottom and bridge abutment or pier cover beam top surface contact, known as bearing “pit”.
(4). The bearing top sliding plate when the beam contraction exceeds the bearing shear deformation does not occur when sliding.
- Hazards
(1). when the plate rubber bearing shear failure, will limit the free expansion and contraction of the upper structure, will make the upper and lower structure to produce additional stress.
(2). beam under the two bearings compression is not equal, or even a gap, will make the bearing uneven force and shorten the bearing life.
(3). bearing “pit”, so that the beam pivot point dislocation, not only will make the bridge or pier on the top, the concrete due to low-temperature beam shrinkage occurs when local splitting, but also change the bridge, pier stress state, increase its eccentric bending moment.
(4). The top surface of the bearing should be sliding can not be sliding, inevitably increase the shear deformation of the bearing, serious will squeeze crack bridge abutment surface of the concrete.
- Cause analysis.
(1). plate rubber bearing bonded to the epoxy mortar of the bearing bedding stone has not yet solidified, the upper structure is lifted, so that the bearing displacement; or bearing installation position is wrong, after the beam is lifted, to correct the cross-roof beam, so that the bearing lateral shear deformation, the formation of the bearing in the beam expansion, contraction, shear deformation and excessive shear bad.
(2). There is some warping at the bottom of the beam, or the embedded steel plate at the bottom of the beam is dislocated, which causes the difference between the beam and the design requirement value to be too big after the beam is placed, resulting in unequal bearing force. This phenomenon is most likely to happen on the ladder beam of pedestrian bridge.
(3). The actual elevation of bridge abutment, pier or cover beam top is greater than the design value, in order to keep the beam bottom elevation, will be left into a groove at the support to make up, the formation of beam bottom and pier, abutment top clearance is too small; or pier, abutment top is not left according to the bridge cross slope requirements of the slope, resulting in part of the beam under the pier, abutment top elevation exceeds the standard.
(4). between the support and the skateboard and the skateboard. Failure to apply lubricating substances as required by the operating process (the operator does not know this requirement, or although he knows this requirement, he subtracts this process).
- Treatment methods.
(1). epoxy mortar consolidation is a certain time, after installation of the support, must be set aside enough time, until the epoxy mortar is completely solidified. Only then can the superstructure lifting to ensure the accuracy of the bearing position.
(2). beam bottom bearing parts, required level, level, bearing parts of the relative height error should not be greater than 0.5mm; pier bearing pad top elevation should be accurate, and on the surface to be smooth; each pier, the same piece of beam bearing pad top relative height error is not greater than 1mm, adjacent two piers under the same piece of beam, bearing pad top relative height error is not greater than 3mm.
(3). When not up to (2) standards have to leave the bearing pits, should make the bearing with epoxy mortar after consolidation, there is enough deformation between the bearing and the pits to allow for. At the same time, pay attention to the beam bottom surface and pier, top surface clearances should be greater than the bearing compression plus 20mm of value.
(4). rubber support placement, should be according to the design requirements, in the pier top marked out the longitudinal and transverse line, after placement, displacement deviation shall not be greater than 5mm; do not allow rubber support and beam bottom or bearing stone, the relative movement of any direction.
(5). support and beam bottom, or bearing pad stone top surface, should be all close contact, local gap, shall not exceed 0.5mm wide; a skateboard, must be required in the support and skateboard, skateboard on the application of lubricants.
- . Installation of bearings, preferably in the average annual temperature. Otherwise, the support can produce pre-displacement (i.e., one end of the beam in place to press the support, and then the beam to apply longitudinal thrust, resulting in the calculated displacement value, and then let the other end of the beam to fall on the support).
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