Model essay on bridge engineering technology-bridge engineering construction technology
Bridge construction is an important link in engineering project construction, and the key to the development of bridge construction lies in the level of construction technology. With the continuous progress of science and technology, construction machinery, equipment and building materials are also developing, and bridge construction technology is also improving. In order to improve the technical level of bridge construction, this paper briefly discusses the bridge construction methods and several construction technologies.
Keywords: bridge construction technology
China Library Classification Number: TU74 Document Identification Number: A
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In the heyday of ancient bridges in China, there were many innovations in bridge type and structure. Carefully conceived and colorful? . After the Song Dynasty, the number of bridges increased greatly, and the spanning ability, shape and function of bridges were improved, which fully demonstrated the wisdom and artistic level of ancient craftsmen in China in bridge construction and became a valuable asset in the history of bridge construction in China. In the early days of liberation, China's highway and urban construction departments rebuilt and built a considerable number of bridges on highways and urban roads, and the mileage opened to traffic doubled compared with that before liberation. With the progress of science and technology, the development of construction machinery, equipment and building materials, the bridge construction technology is also constantly improving.
I. Cast-in-situ continuous beam
1, general requirements of cast-in-place continuous beam with support method
In the construction of cast-in-place continuous beam support by support method, the stiffness, strength and stability of the support must be calculated before installation, the distance between the vertical bar and the horizontal bar must be determined, and the quality of the bars must be checked one by one. Foundation treatment is the key part of cast-in-place beam support system. The bearing capacity of the foundation within the full length of the bridge must meet the full load of continuous beam construction, and the support must be kept without deformation and settlement, otherwise it should be strengthened. If the road section where the foundation is located is a soft soil subgrade section, and the bearing capacity of the foundation is low, the pseudo-ginseng lime soil is used for replacement and compaction, and the replacement thickness is determined according to the calculated load to improve the bearing capacity of the foundation. After foundation treatment, the scaffold can be erected only after checking the bearing capacity of foundation. The bottom of the bracket is provided with a bottom support.
2. Construction control
The purpose of construction control is to ensure the safety and stability of the structure, make the alignment of the bridge deck system meet the design requirements, and make the internal force distribution of the structure basically meet the ideal state of design. On the premise of ensuring the stability of the structure, double control of deformation and stress is adopted, with deformation control as the main factor and stress development as the consideration. The deformation, construction deflection and elevation of the whole bridge should be controlled.
Control method: give priority to the overall bearing capacity and anti-overturning stability; Strengthen the arrangement of vertical and horizontal diagonal braces, increase horizontal diagonal braces or diagonal braces, and improve the stability against overturning; For independent supports with particularly large aspect ratio (greater than 5), large steel supports should be preferred. The stud connectors are staggered, and each horizontal connector shall not be greater than 50% of the total number of studs. Fasteners of bolt joints shall be fastened or wedged; Strengthen the arrangement of vertical and horizontal diagonal braces to restrain the deformation of vertical poles; Fasteners of horizontal bar joints shall be fastened firmly or wedged firmly to ensure effectiveness; The step distance of horizontal Rachel reinforcement should not be greater than the calculated value; Strengthen the arrangement of vertical and horizontal diagonal braces and restrain the deformation of vertical poles. Targeted safeguard measures:
(1) The foundation is rolled flat and meets the bearing capacity requirements.
(2) The supporting foundation is 20 cm ~ 30 cm higher than the surrounding ground, and intercepting ditches are set around to prevent rainwater from flowing in and water from invading bubbles during construction.
(3) The cross sleeper beam (square timber or section steel) should be set on the gravel foundation to improve the overall stress effect; Especially to strengthen the diagonal bracing in the height difference direction; In the form of height difference along the bridge, a firm rigid connection should be adopted between the bracket and the pier; In the form of height difference across the bridge, diagonal braces should be added on the high side of the support as far as possible, and diagonal braces should be added on the short side; Through the results of preloading detection and checking calculation, accurate parameters are provided for construction adjustment, and the beam at the concentrated load position is strictly accepted.
3. Build a new greenhouse for the beam section to be poured, and hang a thermal insulation curtain to separate the thermal insulation pipeline from the concrete beam section greenhouse;
(1) The constructed shed, external formwork and bottom formwork of cast-in-place beam section will not be removed or moved forward, and will be used for thermal insulation of prestressed pipeline of cast-in-place beam section. A new greenhouse will be built for the beam section to be concreted, and a thermal insulation curtain will be hung between it and the beam section greenhouse where concrete has been concreted. After covering and wrapping heat preservation measures are taken.
(2) Keep the temperature above 0℃ before the strength of the slurry in the prestressed channel reaches 25MPa.
(3) Before grouting, the hole and both ends must be sealed, and the pipe section shall be dried with high-pressure water or high-pressure wind, and there shall be no water in the pipe. Then grouting.
(4) The protection of pre-stressed duct grouting is mainly the problem of bleeding, which requires that the slurry should not bleed, and should be properly strengthened at an early stage to reduce the possibility of freezing and the expansibility of microtubules. When mixing slurry, hot water and cement cannot be directly mixed, and the cement should be kept warm and not stored in the open air. In order to prevent the cement slurry from bleeding, the following methods are adopted to obtain appropriate early strength:
Adopt a high-speed mixing device with 1000 rpm to reduce the water cement ratio to below 0.3;
B) increase water-retaining materials (such as fly ash and silica fume) to reduce bleeding;
Adding superplasticizer to reduce water cement ratio;
The bleeding performance of cement slurry was tested by capillary bleeding test.
Second, cantilever cast-in-place
1, cantilever cast-in-place general requirements
The support is designed with self-supporting system components. During pier construction, the steel truss of support shall be embedded in the corresponding position of pier as required. The structure needs strict stress calculation. Support preload:
(1) Pre-press the bracket before use, test its strength and stability, and measure its inelastic deformation and elastic deformation.
(2) Calculate the preloading load according to the concrete weight borne by the support, and then consider the construction load and the safety factor of construction.
(3) The unloading sequence should be opposite to that of ballast, and observation records should be made. By analyzing the data obtained in the preloading process, the inelastic deformation value and elastic deformation value are found out, and the regression equation is summarized as the basis for adjusting the height of the formwork. Hanging basket design: including the design of main truss, bottom formwork platform, formwork system, anchoring system and walking system to meet the construction load, stability, safety and operability.
2, cantilever beam construction technical measures
Technical measures:
(1) The installation, operation and use of the hanging basket belong to aerial work, and comprehensive safety protection measures should be taken; On-site technicians must check the positions of key stress parts such as hanging basket, front and rear suspenders, hangers and rear anchors, and solve problems in time when found.
(2) Check the accuracy of the reserved hole position and whether the hole is vertical; Before and after pouring concrete, jack the sling tightly, and the stress is even, so as to prevent the bearing from being staggered with the poured beam section.
(3) Strengthen the observation of elevation, axis and deflection during construction, and sort out deflection curves.
3. Precautions for cantilever beam construction
Safety work must be put in the first place in cantilever construction. In the construction, in addition to protective platform, safety net and other measures, it is especially necessary to make disclosure to the construction personnel to improve safety awareness and avoid possible dangerous factors such as falling objects.
Third, strengthen the quality management of bridge construction.
1, pay attention to the durability of the structure.
In the process of construction and use, bridges will be eroded by the environment and harmful chemicals, and bear external effects such as vehicles, wind, earthquake, fatigue, overload and human factors. At the same time, the performance of the materials used in the bridge will continue to deteriorate, resulting in different degrees of damage and deterioration of various parts of the structure, which not only affects the use, but also increases economic losses.
2. Strengthen concrete quality management
First of all, the construction unit should purchase materials in strict accordance with the national building materials standards, and ensure the quality of cement materials is stable and does not deteriorate from beginning to end. For mass concrete, cement with low hydration temperature should be used; Secondly, in the construction process, the constructors must mix the concrete according to the strength grade and impermeability grade, fully control the temperature when the concrete enters the mould, carry out layered pouring and design reasonable maintenance measures, and cover the concrete surface with straw mats, straw curtains and other measures to ensure the reduction of temperature stress and avoid temperature cracks in the concrete; Thirdly, when pouring concrete, it must be fully vibrated, especially where the prestressed pipes in the web are concentrated, to ensure the concrete pouring is dense.
3. Strengthen the quality management of bridge structure.
First of all, the construction unit should do a good job of measurement carefully and accurately, and the setting-out and positioning work should be accurate without any deviation. After the completion of pier construction, the plane position of the bridge should be completely determined; Secondly, due to various bridge structures, complicated construction process and technology, the required construction technology is more accurate. Therefore, the construction unit must carry out the construction in strict accordance with the design drawings, and strictly manage and control the vibrating maintenance of concrete and the tensioning of prestress to ensure the bearing capacity of the bridge structure; Thirdly, we should pay attention to the beautiful and smooth appearance of the bridge, and there should be no appearance quality loss caused by defects in construction methods or uneven vibrating of concrete.
Concluding remarks
In short, in bridge construction, we should choose the appropriate construction methods and technologies according to the actual situation. Modern bridge construction technology is advancing by leaps and bounds, and advanced technology, equipment and high-tech materials are constantly emerging. Of course, we will encounter all kinds of new problems in the construction process, which requires us to constantly explore new methods and technologies.
refer to
[1] Xu. Construction control of long-span bridges [M]. Beijing: People Communications Publishing House, 2000.
Xiang Musheng, open and seal the world. Construction control technology of long-span prestressed concrete bridge [J]. China Journal of Highway and Transportation, 2002, 10.
[3] Hao Zhigang. On Bridge Construction Technology and Management [J]. Science and Technology Information.2012 (08)
[4] Bai Bing, Wang Canbin. On the construction technology and safety management of bridge engineering [J]. Guide to scientific and technological innovation.2012 (11)
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