Method for midspan closure of river-crossing variable cross-section continuous steel truss girder

Abstract

The invention relates to a midspan closure method for a river-crossing variable cross-section continuous steel truss girder. The midspan closure method comprises the following steps: (1) determining the final data measurement time to be 16-20 DEG C during closure; (2) measuring positions are arranged at the positions of polar side hole groups of webs of upper and lower chord members; (3) high-temperature closure is adopted; (4) according to closure data, the final axial compression amount is determined as follows: the upper chord is 15 mm, the lower chord is-5 mm, and the temperature expansion and contraction amount is 0.9 mm / DEG C; (5) pasting small prisms at the measurement points, measuring the absolute elevation, mileage and axis of the measurement points by using a Lycra TCA1201 high-precision total station, and measuring the distance between the two measurement points by using a Great Wall fine work 30m steel tape as the verification of the measurement data of the total station; and (6) calculating the distance between the measuring points by using the actually measured data, subtracting the axial compression amount to obtain the final size, obtaining the specific size of the closure section rod piece through simulation, feeding back the specific size to a base for secondary matching cutting and drilling, and then delivering the closure section rod piece to a bridge site for installation.

Description

Technical Field

[0001] The present invention relates to a method for realizing stress-free first-span closure by using a variable cross-section continuous steel truss beam and a method for installing the mid-span closure of a variable cross-section continuous steel truss beam across a river, belonging to the field of manufacturing of variable cross-section continuous steel truss beam bridge installation technology. Background Art

[0002] CN111472285A, with the name "A method for installing a variable cross-section continuous steel of the main bridge by using a cable crane", the steps are as follows: Firstly, construct the steel truss beam at the pier top; then carry out the cantilever assembly construction of the main beam: symmetrically cantilever hoist the steel truss beam segments on both sides of each main pier with a cable crane and install the steel truss beam segments; and set a lower horizontal bracing concrete slab at the steel truss beam segment, and carry out the construction of the second steel truss beam segment of each main pier; after the connection of the third steel truss beam segments of each main pier is completed, pour concrete into the steel truss beam members at this segment; after the concrete in the members reaches the requirements, carry out the construction of the next steel truss beam segment of each main pier, and stop when the mid-span construction reaches the segment before the closure segment; finally, close the side span and the mid-span. Using this scheme, not only is the acting force of the deck crane on the steel truss beam eliminated, the stress at the pier-beam joint is reduced, but also symmetric cantilever assembly can be realized for each bridge main pier, increasing the construction operation surface and accelerating the construction progress. For the four-span continuous curve bridge in this application, firstly, the adopted process is to erect a platform under the main bridge, which is mainly used for the assembly and welding of the prefabricated members in the factory, and the members are assembled and welded into an integral segment, and the single-segment cable hoisting is carried out by using the temporary cable cranes erected in advance on both banks; secondly, concrete needs to be poured into the steel truss beam members after the installation of the third truss beam segment; thirdly, the side span closure is completed first, and then the mid-span closure is completed. Summary of the Invention

[0003] Design Purpose: To design a technical method for the mid-span closure of a variable cross-section continuous steel truss beam across a river that not only successfully solves the problem of mid-span closure of variable cross-section continuous steel truss beam by cantilever lifting of loose parts, but also has strong on-site practicability.

[0004] Design Scheme: In order to achieve the above design purpose. In the design of the technical scheme of the present invention: The technical method for the mid-span closure of a variable cross-section continuous steel truss beam is based on a bridge with a span of 1330 meters, and is designed and studied to ensure the smooth installation of the mid-span closure segment. Due to space reasons, the hoisting process of the members of the mid-span closure segment is different from that of the members of the other segments, and due to factors such as manufacturing, installation, measurement, and axial elastic compression of the members of the mid-span closure segment, the errors accumulate here. Therefore, a margin needs to be added at one end when manufacturing the members of the mid-span closure segment in the factory, and the members of the closure segment are re-cut and drilled according to the on-site measured data in the factory.

[0005] 1. Key points for successful mid-span closure: ① The space is narrow, and the reasonable hoisting process of the members is the key, as well as the key and difficult points for closure; ② Determining the appropriate and reasonable measurement point positions on the members before closure and the actual measurement data are the key and difficult points for closure; ③ Ensuring the accuracy of secondary cutting and drilling based on the on-site measurement data is the key and difficult points for closure.

[0006] 2. Through on-site analysis of the actual measurement data, the following conclusions are obtained in the present invention: ① Through data analysis and calculation of the actual measurement, when the temperature rises, the elevation decreases, and when the temperature decreases, the elevation increases. ② Regarding the influence of temperature change on the elevation, the elevation changes of the upper and lower chord members are basically the same. Through data analysis and calculation of the actual measurement: for every 1°C increase in temperature, the elevation decreases by 3.4 mm. ③ Through data analysis and calculation of the actual measurement, the influence of temperature change on the mileage is different at different time periods. For every 1°C increase in temperature, the upper chord member elongates by 1.3 mm, and the lower chord member elongates by 0.7 mm. ④ Through analysis of the actual measurement data, the temperature change has no influence on the axis. ⑤ Through analysis and calculation, the actual length of the closure section members is finally obtained, and the drawing is drawn and fed back to the factory for secondary cutting and drilling.

[0007] 3. Working principle of the present invention: (1) Through multiple measurements, analysis, and discussions, the data measurement time is finally determined to be from 16°C to 20°C. (2) Determine the measurement positions: The measurement positions are set at the web extreme edge hole groups of the upper and lower chord members (as shown in Figure 2 ). (3) High-temperature closure is adopted for this closure. (4) In order to ensure stress-free rationality, the axial compression of the stay cables needs to be considered in the closure data to reduce the axial pressure generated by the temporary stay cables on the steel truss girder. Through modeling simulation and on-site actual measurement, the final axial compression is determined to be: 15 mm for the upper chord member, -5 mm for the lower chord member, and the temperature expansion and contraction amount: 0.9 mm / °C. (5) Stick small prisms at the measurement points, and use the Leica TCA1201 high-precision total station to measure the absolute elevation, mileage, and axis of the measurement point positions. Use a Great Wall Precision 30 m steel tape to measure the distance between the two measurement points as a verification of the total station measurement data to ensure the accuracy of the data. Measured data of the closure section (partial screenshot, see Figure 3 ). (6) Calculate the distance between the measurement points using the measured data, subtract the axial compression as the final dimension, and obtain the specific dimensions of the closure section members through simulation, and feed back to the base for secondary cutting and drilling (the closure section members have been pre-increased with cutting allowance and the hole groups have not been drilled during the previous manufacturing and production). Then it is shipped to the bridge site for installation.

[0008] Compared with the background art, the present invention has the following advantages: First, there is no similar case for reference, so it has creativity and novelty. Second, the present invention details the installation method for the mid-span closure of a variable cross-section continuous steel truss beam across a river in mountainous areas, which has reliable practicability and operability. Third, the installation method of the present invention belongs to piecemeal hoisting, which suits the characteristics of the western mountainous areas, is convenient for transportation and has low requirements for lifting equipment. Fourth, the closure method of the present invention fully considers factors such as temperature and the axial compression of temporary stay cables, achieving stress-free closure. Description of the Drawings

[0009] Figure 1 It is a schematic diagram of the hoisting of the closure section.

[0010] Figure 2 It is a schematic diagram of the measurement position set at the web extreme hole groups of the upper and lower chord members.

[0011] Figure 3 It is a schematic table of the measured data of the closure section (partial screenshot).

[0012] Figure 4 It is a schematic diagram of the hoisting of the closure section. Detailed Embodiment

[0013] Embodiment 1: Refer to the attached Figures 1-4 A method for the mid-span closure of a variable cross-section continuous steel truss beam across a river. The first step: Use a 100-ton truck crane to stand on the trestle to hoist 2 lower chord members. The standard joints are fixed and connected with ordinary bolts and drift pins. The lower chord member of the closure joint on the closure side is fixed with ordinary bolts and drift pins, and a connecting plate is used to transfer the force to the adjacent segment.

[0014] The second step: Use a 100-ton truck crane to stand on the trestle to hoist the vertical web members and diagonal web members on both sides. The connecting plate on the closure side of the diagonal web member is not fixed.

[0015] The third step: Use a 100-ton truck crane to stand on the trestle to hoist the drain trough.

[0016] The fourth step: Use a 100-ton truck crane to stand on the trestle to hoist 2 upper chord members. The standard joints are fixed and connected with ordinary bolts and drift pins. The lower chord member of the closure joint on the closure side is fixed with ordinary bolts and drift pins, and a connecting plate is used to transfer the force to the adjacent segment.

[0017] The fifth step: After the hoisting of the two main trusses is completed, immediately use drift pins to fix them after aligning the bolt holes of the closure joint using temperature, and then tighten the high-strength bolts. After the tightening of the high-strength bolts is completed, the installation of the main trusses at the closure joint is completed.

[0018] The sixth step: Use a 100-ton truck crane to stand on the trestle to hoist the bridge deck and upper crossbeam to the bridge deck of the adjacent segment that has been installed and temporarily store them.

[0019] Step 7: Use a 100-ton truck crane to stand on the trestle to hoist the boom and sidewalk.

[0020] Step 8: Use a 100-ton truck crane to stand on the trestle and install the lower horizontal joint, lower crossbeam, inspection road, and cross joint.

[0021] Step 9: Use a 100-ton truck crane to stand on the trestle and hoist the upper beam previously stored on the S9 segment bridge deck.

[0022] Step 10: Use the previously prepared 16-ton truck crane to stand on the adjacent segment bridge deck to hoist the longitudinal beams and the bridge deck panels previously stored on the adjacent segment bridge deck. At this point, the installation of the joint section is completed.

[0023] It should be understood that although the above embodiments provide a relatively detailed textual description of the design ideas of the present invention, these textual descriptions are only simple textual descriptions of the design ideas of the present invention, rather than limitations on the design ideas of the present invention. Any combination, addition or modification that does not exceed the design ideas of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for closing the mid-span of a variable-section continuous steel truss beam across a river, characterized by: (1) The final data measurement time of the mid-span closure of the variable-section continuous steel truss beam across the river is determined to be 16℃ to 20℃; (2) The measurement position is set at the extreme edge hole group of the web of the upper and lower chords; (3) High temperature closure is used for closure; (4) The closure data needs to take into account the axial compression of the cable to reduce the axial pressure of the steel truss caused by the temporary cable. Through modeling simulation and actual on-site measurement, the final axial compression is determined as: 15mm for the upper chord, -5mm for the lower chord, and temperature expansion: 0.9mm / ℃; (5) A small prism is attached to the measuring point, and the absolute elevation, mileage and axis of the measuring point are measured using the Leica TCA1201 high-precision total station. The distance between the two measuring points is measured using a Great Wall Seiko 30m steel tape measure as a verification of the total station measurement data; (6) The distance between the measuring points is calculated using the measured data, and the axial compression is subtracted to obtain the final size. The specific size of the joint section members is obtained through simulation, and the data is fed back to the base for secondary cutting and drilling. The members are then shipped to the bridge site for installation.

2. The method for mid-span closure of a variable-section continuous steel truss beam across a river according to claim 1, wherein the steps are: Step 1: Use a truck crane with a capacity of 100 tons or more to hoist two lower chords on the trestle. The standard opening is fixed with bolts and rivets. The lower chord of the closure part on the closure opening side is fixed with bolts and rivets. Use a connecting plate to transfer the force to the adjacent segments. Step 2: Use a truck crane with a capacity of 100 tons or more to stand on the trestle to hoist the vertical and diagonal braces on both sides, and the connecting plate on the side of the diagonal brace joint is not fixed; Step 3: Use a truck crane with a capacity of 100 tons or more to hoist the drainage trough on the trestle; Step 4: Use a truck crane with a capacity of 100 tons or more to hoist two upper chords on the trestle. The standard openings are fixed with bolts and rivets. The lower chords of the closure parts are fixed with bolts and rivets. The connecting plates are used to transfer the force to the adjacent segments. Step 5: After the two main girders are hoisted, the bolt holes of the joint are aligned by temperature, and then they are fixed with punches, and then the high bolts are tightened. After the high bolts are tightened, the main girders of the joint are installed; Step 6: Use a truck crane with a capacity of 100 tons or more to stand on the trestle and hoist the bridge deck and upper crossbeam to the adjacent segment bridge deck that has been installed for temporary storage; Step 7: Use a truck crane with a capacity of 100 tons or more to stand on the trestle and install the boom and sidewalk; Step 8: Use a truck crane with a capacity of 100 tons or more to stand on the trestle and install the lower horizontal joint, lower crossbeam, inspection road, and cross joint; Step 9: Use a truck crane with a capacity of 100 tons or more to stand on the trestle and hoist the upper beam previously stored on the bridge deck of the S9 segment; Step 10: Use the previously prepared mobile crane with a capacity of equal to or greater than 16 tons to stand on the adjacent segment bridge deck to lift the longitudinal beams and the bridge deck previously stored on the adjacent segment bridge deck. At this point, the installation of the joint section is completed.

Images