There are many factors affecting the construction of expansion joints, such as shrinkage of concrete, changes in construction temperature, changes in bridge deflection due to load, etc. In order to ensure the quality of construction, pre-construction preparation work must be carried out to determine the size of the expansion gap and slotting construction in strict accordance with the requirements. In addition, seam cutting construction, pre-buried steel technology and installation of expansion joint devices and welding construction are also the focus of construction quality control.
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Factors affecting the expansion volume
- The effect of shrinkage of concrete on the expansion volume
When carrying out road and bridge construction, there are many types of expansion joints to choose from. Combined with the construction characteristics of current expansion devices and force transmission methods, China mostly uses modulus-supported expansion joint devices, as well as steel-supported expansion joint devices, but in construction, if the concrete shrinks or has problems such as creep, it directly affects the size of the expansion volume. After careful analysis, it is found that due to the role of pre-stressing, the shrinkage amount of temperature reduction, etc., directly lead to the occurrence of creep and shrinkage of concrete.
- The influence of temperature on the expansion volume
As the temperature changes, the construction of the bridge internal temperature distribution is not uniform, resulting in a large local temperature difference, for example, in the end of large span bridges will appear corner displacement problem, for this situation, in the design and planning process, it should be given sufficient attention. If the bridge span is limited, these problems will not occur, or the degree of impact will be minimal, so this aspect does not need to be considered.
- Changes in bridge deflection due to loads
The bridge will be put into use after the construction is completed, and the influence of crowds, incoming and outgoing traffic, especially heavy truck loads, combined with the influence of the bridge pavement and self-weight, lead to various expansion joints, such as angular displacements and other problems. Therefore, in the construction of road and bridge construction, these problems should be analyzed scientifically, and strict requirements should be made for the load situation borne by the bridge to avoid excessive loads that can affect the service life of the bridge.
The use of expansion joint technology in road and bridge construction
- Construction preparation
Safety and stability are the main considerations in bridge construction, so it is important to ensure that the construction process of expansion joints meets the design requirements. In order to improve the construction quality of the bridge, necessary preparations must be made before construction. Materials are the basis to ensure the construction quality, so to control the quality of materials for expansion joints, the procurement department of the enterprise should choose the business backbone for material procurement. First of all, choose the supplier with high cost performance for cooperation, when the materials are stationed at the site, verify the quantity and quality of the materials in time, check whether they have quality inspection reports, and resolutely eliminate unqualified materials from entering the site. For each batch of materials that arrive, they should be randomly checked according to the requirements, and the quality should be fine before they are applied to the construction. The use of equipment in the early stage should also be a comprehensive overhaul, and problems found in a timely manner to repair, to avoid construction failures, affecting the progress of the project.
- Determine the expansion gap size
Construction quality depends on the size of the expansion joint, if the gap is too large, the road and bridge in use will occur after the jumping problem, directly affecting the safety of vehicle operation, if the expansion gap is too small to meet the design requirements, when the alternation of winter and summer, due to temperature changes lead to thermal expansion and contraction of the road surface can not be carried out normally, to carry out the road surface will appear broken and other problems, the road not only can not work properly, but also increase maintenance cost. For this series of problems, in addition to improving the use of concrete pressure resistance, but also must ensure that the size of the construction gap in line with the design requirements. For example, in the construction of plate rubber expansion joints, the bridge deck is first paved, then the bridge deck is cut, and finally the size of the expansion joint is determined. In addition, attention is paid to the processing of the joint position, which is generally set between the beam end and the bridge deck, as well as the two beam ends.
Road And Bridge Construction Expansion Joint Application Points
3.Construction technology about slotting
After laying asphalt concrete on the bridge pavement, the construction of slotting width should be carried out according to the process sequence. After measuring and sampling, the technician uses a cutting machine to do the necessary processing of the cut joints, and then sets the width of the slotting according to the design requirements, which mainly ensures the verticality and neatness of the cut joints. Bridge deck will deposit some debris due to construction, you can use the blower to deal with it, and generally use foam to fill the gap. After completing the slotting operation, in order to effectively reduce the damage to the concrete, it is necessary to adjust the pre-built reinforcement in the slotting, and at the same time implant the reinforcement at the top surface of the beam, about 1cm, and if the reinforcement breaks, it must be repaired effectively. The scrap generated during construction is cleaned up in time to ensure the neatness of the site.
- Slitting construction technology
After the completion of road and bridge paving work, combined with the width of the reserved slot, timely construction of cutting joints. Usually use cutting machine for operation, not only low cost, but also high operation efficiency. Cutting joints should be carried out according to the center line of the expansion joint, and the straightness should be ensured when the line is projected, and then the seam cutter should be arranged according to the projection line, and the seam cutter should be carried out after the preparation work is ready, firstly, the position of the seam cutter must be accurate, because the operation is complicated, it is not very realistic to finish relying on the seam cutter to handle, so it needs to cooperate with manual operation. Pavement brick layer for cutting seam construction will produce a lot of debris, need to manually remove in time to avoid affecting the overall construction effect. A certain amount of construction should also be carried out on the pavement outside of the cut joints to ensure the overall construction effect, otherwise the concrete will produce loosening.
- Technical analysis of pre-buried reinforcement
When carrying out the construction of pre-buried reinforcement, it is crucial to ensure the quality of reinforcement. When the purchased materials enter the site, random inspection must be carried out, and the supplier should be fully inspected for the first cooperation to avoid using unqualified products.
As the use of steel bars in road and bridge construction is very large, so to centralize the management and transportation, in the construction process, in both sides of the steel bars welded steel column, to ensure that there is no problem in the length, if there is an error, its range should also be within the allowable value, and then the need for the steel bars buried to the design location, in the above first draw the exact location, in the filling for sand reinforcement deep location , to ensure that it will not contaminate the steel bars , if inadvertently lead to rebar pollution, to send someone to clean up, and finally according to the relevant design requirements, carefully calculate the thickness and length of the rebar weld. In the construction found that the bending or deformation of the reinforcement, the technical staff should make timely adjustment, and do not let the fixed position of the reinforcement move in the pre-burial. Local location of the reinforcement if damage occurs, generally use the way of reinforcement implantation to solve. When carrying out the reinforcement implantation operation, the construction of the anchoring direction of the expansion joint must be carried out in conjunction with it, so as to ensure that the position between the two is qualified.
In addition, if the position of the two deviates, it directly affects its force capacity, deviation to a certain extent, it does not meet the design requirements, even after the construction is completed in use, the bearing capacity of roads and bridges will not meet the requirements, so there will be a lot of safety problems in use, but also increase the maintenance and maintenance costs later. Due to the long storage time of steel bars and the harsh environment of the construction site, a large amount of rust will be generated, usually using iron brushes for construction. If there is a misalignment problem in the construction, that is, in the location of the anchor ring of the expansion joint, as well as the location of the pre-buried reinforcement, the adjustment of the anchor ring of the expansion joint shall be carried out to avoid local problems affecting the overall construction quality and progress.