A method for closing a mid-span of a long-span composite girder cable-stayed bridge

Abstract

The application discloses a method for closing a mid-span of a large-span combined beam cable-stayed bridge, which comprises the following steps: manufacturing a mid-span closure section steel beam and connecting pieces thereof; moving a crane to the position of hoisting the side-span closure section and the mid-span closure section; determining a cutting amount and an adjustment parameter; cutting and drilling according to the cutting amount and the adjustment parameter; temporarily restraining the conversion into a pushing device; placing all steel components of the mid-span closure section in advance on the cantilever end of the erected beam section; welding a beam support component on the side box girder; evaluating and adjusting the geometric posture of the mid-span closure gap; locking the pushing device after pushing to the position; installing the side box girder; adjusting the posture of the mid-span closure gap again; locking the pushing device after pushing back to the position; carrying out splicing construction; installing cross beams and small longitudinal beams; and carrying out bridge deck slab construction, so that the mid-span closure operation is completed. The application comprehensively considers the construction precision problem, eliminates the adverse effects as much as possible, and improves the closure speed and precision.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bridge engineering, and particularly relates to a method for closing a mid-span of a large-span composite beam cable-stayed bridge. BACKGROUND

[0002] Compared with a pure steel beam cable-stayed bridge, a steel-concrete composite beam cable-stayed bridge has less steel consumption, better economy, greater main beam rigidity, higher stability, and can effectively improve the durability of the road surface pavement layer. In recent years, in the construction of bridges with a span of 500-700 meters, composite beam cable-stayed bridges are used in large quantities, and the maximum span has reached 720 meters, and the number and span will continue to develop.

[0003] The composite beam cable-stayed bridge adopts a steel main beam with a small cross-sectional area to improve the crack resistance of the bridge deck, so generally a double-web I-section and a double-web box section are used. When the span of the composite beam cable-stayed bridge reaches more than 700 meters, the lower flange plate of the I-section steel main beam is difficult to meet the force requirement, and a double-web box form steel main beam needs to be used.

[0004] Regardless of the double-web I-section or the double-web box section, the connection between the segments of the steel main beam of the composite beam cable-stayed bridge generally adopts a bolted connection. The diameter of the high-strength bolt is generally only 2-3 mm smaller than the diameter of the bolt hole, and there are hundreds of bolt holes on one splicing surface. Due to manufacturing errors, it is already very difficult to completely install the high-strength bolts into the bolt holes, and if the angle is to be adjusted through the joint between the segments, the amount of adjustment is extremely small. The double-web box steel main beam has more splicing surfaces and greater overall rigidity than the double-web I-section steel main beam, and the angle adjustment during the closure of the mid-span is less operable, requires higher construction precision, and is more difficult to close. As the span of the composite beam cable-stayed bridge increases, the required matching closure technology precision requirement will also be higher. SUMMARY

[0005] The purpose of the present application is to provide a method for closing a mid-span of a large-span composite beam cable-stayed bridge to solve the problem of extremely high precision requirement for the bolted connection of the closure segment of the double-web box steel main beam form composite beam cable-stayed bridge. The present application fully considers and optimizes the manufacturing of the closure segment steel main beam and the splicing plate, the adjustment of the geometric posture of the closure opening, the hoisting and splicing of the closure segment, and the arrangement of the closure process, and eliminates the adverse effects as much as possible to improve the closure speed and precision.

[0006] The present application solves the above technical problems through the following technical solution: a method for closing a mid-span of a large-span composite beam cable-stayed bridge, comprising the following steps:

[0007] Step 1: manufacturing a mid-span closure segment steel beam and its connecting piece, and reserving a cutting amount on both sides of the edge box beam top plate and bottom plate in the bridge direction;

[0008] Step 2: Move the midspan to the position of hoisting the midspan closure segment by two cranes respectively;

[0009] Step 3: Continuously monitor the temperature effect of the erected beam segments on both sides of the midspan closure during the construction of the side span closure, obtain the measured geometric posture data of the midspan closure, analyze the geometric posture data of the midspan closure to obtain the cutting amount of the midspan closure segment and the adjustment parameters of the drilling of the splicing plate;

[0010] Step 4: Cut the steel beam of the midspan closure segment according to the cutting amount, and drill the splicing plate according to the adjustment parameters;

[0011] Step 5: Convert the temporary constraints in the tower area into the main beam jacking device for the midspan closure, and perform the jacking test;

[0012] Step 6: Hoist all steel components of the midspan closure segment, place them on the cantilever end of the erected beam segments on both sides of the midspan closure, and weld the beam supporting components on the top plate of the side box girder;

[0013] Step 7: Based on the state of step 6, evaluate and adjust the geometric posture of the midspan closure;

[0014] Step 8: When the side span closure construction is completed and the conditions for the midspan closure are met, jacking is performed towards the side span direction, and the jacking device is locked after jacking is completed;

[0015] Step 9: The cranes on both sides of the midspan closure simultaneously hoist one side box girder respectively, slowly lower the side box girder after moving it directly above the midspan closure, and embed the two side box girders in the midspan closure and rest them on the erected beam segments on both sides through the beam supporting components in step 6;

[0016] Step 10: Adjust the posture of the midspan closure and optimize the relative geometric position;

[0017] Step 11: Unlock the jacking device and perform back jacking towards the midspan direction, and lock the jacking device after back jacking is completed;

[0018] Step 12: Perform splicing construction on the steel beam of the midspan closure segment and the erected beam segments on both sides thereof;

[0019] Step 13: Remove all temporary constraints between the tower and the beam;

[0020] Step 14: Install the cross beam and small longitudinal beam of the midspan closure segment, and perform bridge deck slab construction, i.e., the midspan closure operation is completed.

[0021] Further, in step 3, the specific operation of continuous temperature effect monitoring is as follows:

[0022] The 24-hour continuous temperature effect monitoring is performed on the erected beam segments on both sides of the mid-span closure gap during the side span closure construction, the erected beam segments on both sides of the mid-span closure gap are monitored every two hours, and the monitoring contents include the temperature field, tower deviation, elevation of the first three segments of the cantilever end on both sides of the mid-span closure gap, mileage, axis deviation, mileage and tension of the cable-stayed cable;

[0023] The inclination of the erected beam segments on both sides of the mid-span closure gap, the length of the mid-span closure gap and the change value of the mid-span closure gap after the temperature influence are obtained by analyzing the monitoring data;

[0024] The temperature rising and temperature falling simulation is performed by using the calculation model to review the accuracy of the monitoring data.

[0025] Further, in the step 5, the specific implementation process of converting the temporary constraint of the tower area into the main beam jacking device is as follows:

[0026] First, the jacking device is installed, and the pre-jacking force calculated by the calculation model is applied, and then the longitudinal temporary constraint is removed;

[0027] The transverse temporary constraint between the tower and the beam is removed;

[0028] The closure jacking device test is performed according to the jacking stroke and jacking force required by the predicted closure temperature.

[0029] Further, in the step 6, the beam support member is a steel upright plate or a steel bracket.

[0030] Further, in the step 7, the specific implementation process of evaluating and adjusting the geometric posture of the mid-span closure gap is as follows:

[0031] The elevation of the measuring points of the first segment B and the second segment A of the cantilever end of the erected beam segments on both sides of the mid-span closure gap is measured;

[0032] If the elevations of the measuring points of the first segment B and the second segment A are equal, or the elevation of the measuring points of the first segment B is slightly higher than that of the second segment A and the elevations of the upstream and downstream are consistent, the geometric posture of the mid-span closure gap is not adjusted;

[0033] If the elevation of the measuring points of the first segment B is lower than that of the second segment A, the cable force of the cable-stayed cable is fine-tuned to lift the cantilever end beam segment.

[0034] Further, in the step 8, after jacking, D=L+d+S+Δd, wherein D is the width of the mid-span closure gap, L is the actual length of the side box beam of the mid-span closure section, d is the joint width on both sides of the mid-span closure gap, S is the operation space at the two joint surfaces, and Δd is the change value of the width of the mid-span closure gap caused by the temperature change.

[0035] Further, the specific implementation process of adjusting the geometric posture of the mid-span closure gap in step 10 is as follows: first, the relative elevation and inclination of the erected beam segments on both sides of the mid-span closure gap are fine-tuned through the cable force of the cable-stayed cable, and then the erected beam segments are diagonally stayed through the tensioning device to fine-tune the axis.

[0036] Further, the specific implementation process of splicing construction in step 12 is as follows: first, small chasers are punched into the positioning bolt holes, and then the alignment accuracy of the bolt holes of the steel beam and the splicing plate is determined through the evaluation hole, if the alignment accuracy meets the hole group bolting requirement, small chasers and tool bolts are punched into the other bolt holes, the temporary code plate is welded to lock the joint surfaces on both sides of the mid-span closure gap at the same time, and then the high-strength bolts are screwed; if the alignment accuracy does not meet the hole group bolting requirement, small chasers and tool bolts cannot be punched, and then the geometric posture of the erected beam segments on both sides of the mid-span closure gap is adjusted again.

[0037] Further, the specific implementation process of punching small chasers into the positioning bolt holes is as follows: when the main beams on both sides of the splicing surface are inclined upward, small chasers are first punched into the middle two bolt holes of the lowermost row of bolt holes, and then small chasers are punched into one of the outermost bolt holes of the uppermost row of bolt holes;

[0038] When the main beams on both sides of the splicing surface are inclined downward, small chasers are first punched into the middle two bolt holes of the uppermost row of bolt holes, and then small chasers are punched into one of the outermost bolt holes of the lowermost row of bolt holes.

[0039] Further, between step 9 and step 10, there is also a step of swinging back the crane boom and centering it horizontally across the bridge.

[0040] Advantages

[0041] Compared with the prior art, the advantages of the present application are as follows:

[0042] The mid-span closure method of the large-span composite beam cable-stayed bridge provided by the present application fully considers and optimizes the manufacturing of the closure section steel main beam and the splicing plate, the geometric posture adjustment of the closure gap, the hoisting and splicing of the closure section, and the closure procedure arrangement, comprehensively considers the construction precision problem, eliminates the adverse effects as much as possible, and improves the closure speed and precision; the present application has less resource input in the whole closure operation project, does not need to perform balance weight, does not need to weld the stiff skeleton, has low construction cost, has short closure operation duration, has low risk, has high operability, meets the splicing precision of the closure section steel beam bolt hole group, further meets the high-precision requirement of the mid-span closure bolting of the composite beam cable-stayed bridge with the side box girder form, and is suitable for the mid-span closure construction of various composite beam cable-stayed bridges. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings described below are only part of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor based on these drawings.

[0044] Figure 1 is the midspan arrangement elevation view of the temperature monitoring before closure in the embodiment of the present application;

[0045] Figure 2 is the midspan elevation view of the closure segment stored on the beam surface before closure in the embodiment of the present application;

[0046] Figure 3 is the elevation view of the closure segment in the simply supported state after hoisting in the embodiment of the present application;

[0047] Figure 4 is the closure mouth detail view of the closure segment in the simply supported state in the embodiment of the present application;

[0048] Figure 5 is the plan view of the crane boom pointing upstream and downstream in the embodiment of the present application;

[0049] Figure 6 is the plan view of the crane boom in the middle and the diagonal cable-stayed in the embodiment of the present application;

[0050] Figure 7 is the bolt evaluation hole position view of the erected main beam with the upward inclination angle during web splicing in the embodiment of the present application;

[0051] Figure 8 is the bolt evaluation hole position view of the erected main beam with the downward inclination angle during web splicing in the embodiment of the present application.

[0052] Among them, 1 is the erected beam segment on both sides of the midspan closure mouth, 2 is the cable-stayed cable, 3 is the side box girder, 4 is the cross beam, 5 is the component for the joist, 6 is the side span direction, 7 is the crane, 8 is the boom, 9 is the pulling device, 10 is the positioning bolt hole, 11 is the evaluation hole. DETAILED DESCRIPTION

[0053] The technical solutions in the present application will be described clearly and completely below in combination with the drawings in the embodiment of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0054] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0055] This embodiment provides a method for closing the mid-span of a large-span composite beam cable-stayed bridge, comprising the following steps:

[0056] Step 1: Manufacture the steel beams and their connectors for the middle span joint section, and reserve a 10cm cutting margin on both sides of the top and bottom plates of the side box beams along the bridge direction. Do not drill holes in the splicing plates for the time being.

[0057] The temperature effect monitoring of the erected beam section 1 (i.e. the main beam) on both sides of the middle span joint is carried out multiple times and continuously. The size of the steel beam of the middle span joint section can be determined by analyzing the temperature effect monitoring data. The steel beam of the middle span joint section can be manufactured according to the size and a margin is reserved.

[0058] Step 2: Move the two cranes 7 of the middle span to the positions for lifting the middle span joint section.

[0059] Figure 1 The elevation view of the middle span layout is shown, and each crane 7 is moved forward to the position of lifting the side span closure section and the middle span closure section respectively. From the beginning of the side span closure to the completion of the middle span closure, the crane 7 is not moved as much as possible. This can avoid the load ambiguity caused by the movement of the crane 7 during the whole closure process, reduce the neglected factors, and ensure the accuracy and efficiency of the closure construction.

[0060] Step 3: During the side span closure construction, the temperature effect of the beam section 1 erected on both sides of the middle span closure is continuously monitored to obtain the measured geometric posture data of the middle span closure. The geometric posture data of the middle span closure is analyzed to obtain the cutting amount of the middle span closure section and the adjustment parameters of the assembly plate drilling.

[0061] After the middle span crane 7 is moved forward to its position and the temporary load is cleared, during the side span closure construction and Figure 1 Under the shown state, the temperature effect of the beam segments 1 erected on both sides of the middle span closure is continuously monitored for 24 hours before closure, and the beam segments 1 erected on both sides of the middle span closure are jointly monitored every two hours. The monitoring contents include the temperature field (temperature of the inclined cable 2, temperature of the steel main beam, temperature of the bridge deck, temperature of the main tower), tower deviation, elevation, mileage, axial deviation, mileage of the first three segments of the cantilever end on both sides of the middle span closure, and tension of the inclined cable 2; the monitoring data (i.e., geometric posture data) are analyzed to obtain the inclination angle of the beam segments 1 erected on both sides of the middle span closure, the length of the middle span closure, and the change in the length after the temperature influence; the calculation model is used to perform heating and cooling simulations to verify the accuracy of the monitoring data; the final manufacturing adjustment parameters of the steel components of the middle span closure section are determined based on the data analysis results (if the error is within the adjustable range, it will be manufactured according to the original size).

[0062] Continuous temperature effect monitoring is the prior art, and the patent document with the publication number CN113106872A and the name of a cable-stayed bridge steel box girder midspan closure method can be referred to.

[0063] Step 4: Cut the midspan closure section steel beam according to the cutting amount obtained in step 3, drill holes in the splice plate according to the adjustment parameters obtained in step 3, and optimize the manufacturing of the midspan closure section steel beam and the splice plate to improve the closure precision.

[0064] Step 5: Convert the temporary constraints in the tower area to the main girder pushing device for midspan closure, and conduct a pushing test.

[0065] According to the pushing stroke, determine whether the top pushing device needs to be installed on both sides of the midspan closure opening. In order to prevent the main girder from moving when the temporary constraints are removed, first install the top pushing device, apply the pre-pushing force calculated by the model, lock the top pushing device, then remove the longitudinal temporary constraints, and then remove the transverse temporary constraints that prevent the main girder from rotating in the horizontal plane between the tower and the beam; After the conversion is completed, the closure pushing device test is conducted according to the predicted closure temperature required for the pushing stroke and the pushing force.

[0066] Step 6: Hoist all steel components of the midspan closure section and place them on the cantilever end of the already erected girder section 1 on both sides of the midspan closure opening, and weld the girder component 5 on the top plate of the side box girder 3.

[0067] Referring to Figure 2 Fig. 6, hoist all steel components of the midspan closure section and place them on the cantilever end of the already erected girder section 1 on both sides of the midspan closure opening, and store all the midspan closure section steel girder loads (such as the side box girder 3, the cross beam 4 and the small longitudinal beam) in advance on the bridge deck at this time. The load at this time is consistent with the load at the time of closure, only the position is different; At the same time, the influence of the load of the midspan closure section side box girder 3 located at the current cantilever end and located in the middle of the midspan closure opening on the inclination angle of the main girder is simulated and analyzed by the calculation model, and is considered when adjusting the attitude of the midspan closure opening. In this state, the attitude of the midspan closure opening is evaluated and adjusted. The load arrangement in this state is closer to the final closure splicing state, which is more conducive to the pre-control of the geometric attitude of the midspan closure opening, and can ensure the rapidity and accuracy of the subsequent formal midspan closure construction.

[0068] In this embodiment, the girder component 5 is a steel upright plate or a steel corbel.

[0069] Step 7: Based on the state of step 6, evaluate and adjust the geometric attitude (mainly the inclination angle) of the midspan closure opening.

[0070] Based on Figure 2In the shown state, the geometric posture of the mid-span closure gap is evaluated, mainly measuring the elevations of the measuring points of the first segment B and the second segment A at the cantilever end of the erected beam segment 1 on both sides of the mid-span closure gap; if the elevations of the measuring points of the first segment B and the second segment A are equal, no adjustment of the geometric posture of the mid-span closure gap is performed; if the elevation of the measuring point of the first segment B is slightly higher than that of the second segment A (inclination upward, and the elevation difference of the measuring points of the first segment B and the second segment A is not more than 15 mm), and the elevations of the upstream and downstream are consistent, no adjustment of the geometric posture of the mid-span closure gap is performed, and the cantilever end of the main beam is in a horizontal or slightly upward inclination, which is more conducive to the bolting of the mid-span closure segment; if the elevation of the measuring point of the first segment B is lower than that of the second segment A, the elevations of the cantilever end beam segment are raised through the fine adjustment of the cable force of 2-3 groups of the cable-stayed cable 2.

[0071] Step 8: When the side-span closure construction is completed and the mid-span closure conditions are met, the pushing is performed towards the side-span direction 6, and the pushing device is locked after the pushing is in place.

[0072] When the side-span closure construction is completed and the mid-span closure conditions are met, the mid-span closure operation begins, first pushing is performed towards the side-span direction 6, and the pushing device is locked after the pushing is in place. After the pushing is in place, D = L + d + S + Δd, wherein D is the width of the mid-span closure gap, L is the actual length of the side box girder of the mid-span closure segment, d is the joint width on both sides of the mid-span closure gap, S is the operation space at the two joint surfaces, and Δd is the change value of the width of the mid-span closure gap caused by temperature change.

[0073] Step 9: The cranes 7 on both sides of the mid-span closure gap simultaneously lift one side box girder 3 respectively, and slowly lower the side box girder 3 after moving it to the position directly above the mid-span closure gap, and embed the two side box girders 3 in the mid-span closure gap and rest them on the two already erected beam segments 1 through the beam rest member 5 in step 6, as shown in Figures 3-5 .

[0074] Step 10: The crane 7 hoisting arm 8 is swung back and centered horizontally across the bridge.

[0075] As shown in Figure 5 , when the two cranes 7 lower the side box girders 3 they respectively lifted to the upstream and downstream of the mid-span closure gap, the hoisting arm 8 of one crane 7 points downstream, and the hoisting arm 8 of the other crane 7 points upstream, which may cause the torsion of the main beam. Swinging back the hoisting arm 8 and centering it horizontally across the bridge can eliminate this effect. The upstream and downstream of the bridge are the horizontal direction across the bridge, and the south and north sides are the longitudinal direction of the bridge, i.e. the longitudinal direction of the bridge, and the sides of the mid-span closure gap are the longitudinal direction of the bridge.

[0076] As shown in Figure 6 , the hoisting arm 8 is swung back and centered horizontally across the bridge. At this time, the hook has been disengaged from the steel beam of the closure segment, thereby reducing one safety measure for the closure segment, which also means that the steel uprights or steel corbels for simply supporting the closure segment must be sufficiently firm and have a large safety factor, and a device for preventing the closure segment from sliding horizontally must also be provided.

[0077] The girder torsion can be measured in advance with the crane 7 unloaded, both when the boom 8 is centered and when it is deflected upstream and downstream. If the boom 8 exerts no torsion on the girder or minimal torsion when positioned upstream or downstream, the boom 8 can be centered without swinging back across the bridge. At this point, the crane 7 is unhooked, providing a safety measure for the closure section. However, the load must be completely unloaded.

[0078] Step 11: Adjust the posture of the middle span joint and optimize the relative geometric position.

[0079] The specific implementation process of adjusting the posture of the middle span closure is as follows: first, the relative elevation and inclination of the erected beam sections 1 on both sides of the middle span closure are fine-tuned by the cable force of the inclined cable 2, and then the erected beam sections 1 are diagonally pulled by the steel strand tensioning device 9 to fine-tune the axis. Figure 6 shown.

[0080] In step 7, the relative elevation and inclination have been adjusted to the right position, so the relative elevation and inclination errors in step 11 will not be very large, which can be achieved by fine-tuning the cable tension of the inclined cable 2.

[0081] Step 12: Unlock the jacking device and push it back toward the mid-span. Lock the jacking device after it is back in place.

[0082] Step 13: Splice the steel beams of the middle span joint section and the erected beam sections 1 on both sides.

[0083] The steel beams of the middle span closure section are connected to the existing steel beams on both sides through splicing plates and high-strength bolts, and the two joint surfaces are operated simultaneously. Figure 7 and Figure 8 , respectively indicating the upward and downward inclination of the erected beam segments 1 on both sides of the mid-span joint. First, a small punch is driven into the positioning bolt hole 10, and then the alignment accuracy of the bolt holes of the steel beam and the splicing plate is evaluated and determined through the evaluation hole 11; if the alignment accuracy meets the requirements of the hole group bolting, small punches and tool bolts are immediately driven into the other bolt holes, and then a temporary code plate is welded to simultaneously lock the joint surfaces on both sides of the mid-span joint, and then the high-strength bolts are tightened (the initial tightening of the high-strength bolts of the splicing plate is a sign that the main beam structure is force-closed). If the alignment accuracy does not meet the requirements of the hole group bolting and the small punches and tool bolts cannot be driven in, the geometric posture of the erected beam segments 1 on both sides of the mid-span joint is adjusted again. Other bolt holes refer to all bolt holes except the three positioning bolt holes 10. When the alignment accuracy meets the requirements of the hole group bolting, the bolt holes between the main beam and the splicing plate have been aligned one by one, and the other bolt holes are all qualified for driving small punches or tool bolts.

[0084] The positions of the positioning bolt hole 10 and the evaluation hole 11 are as follows Figure 7 and 8As shown, when the main beams on both sides of the splicing surface are inclined upward, two small dowels are first punched into the middle positions of the bolt holes in the lowermost row (i.e. Figure 7 two positioning bolt holes 10 represented by the lowermost row of numbers 10) in the middle, and then one small dowel is punched into the outside of the bolt holes in the uppermost row (i.e. Figure 7 one positioning bolt hole 10 represented by the uppermost row of numbers 10); when the main beams on both sides of the splicing surface are inclined downward, two small dowels are first punched into the middle positions of the bolt holes in the uppermost row (i.e. Figure 8 two positioning bolt holes 10 represented by the uppermost row of numbers 10), and then one small dowel is punched into the outside of the bolt holes in the lowermost row (i.e. Figure 8 one positioning bolt hole 10 represented by the lowermost row of numbers 10). Whether inclined upward or downward, there are three positioning bolt holes 10.

[0085] Step 14: remove all temporary constraints between the tower beams;

[0086] Step 15: install the midspan closure segment cross beam 4 and small longitudinal beams, and construct the bridge deck (including prefabricated bridge deck, wet joint and cast-in-place belt), that is, the midspan closure operation is completed.

[0087] The present application comprehensively considers the construction precision problem, can meet the high-precision requirement of the midspan closure splicing of the combined beam cable-stayed bridge in the form of the side box girder 3, has less engineering resource input, does not need to be balanced, does not need to weld the stiff skeleton, has short closure operation duration, is low in risk, is high in operability, can be suitable for the midspan closure construction of various combined beam cable-stayed bridges.

[0088] The above only discloses specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or modifications within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A mid-span closure method for a long-span composite beam cable-stayed bridge, characterized in that: The following steps are involved: Step 1: Manufacture the steel beams and their connectors for the middle span closure section, and reserve cutting allowances on both sides of the top and bottom plates of the side box beams along the bridge direction; Step 2: Move the two cranes on the middle span to the positions for lifting the middle span closure section; Step 3: During the side span closure construction, continuously monitor the temperature effects of the beam segments erected on both sides of the middle span closure to obtain measured geometric posture data of the middle span closure. Analyze the geometric posture data of the middle span closure to obtain the cutting amount of the middle span closure segment and the adjustment parameters of the assembly plate drilling. Step 4: cutting the steel beam of the middle span joint section according to the matching amount, and drilling the splicing plate according to the adjustment parameters; Step 5: Convert the temporary restraints in the tower area into main beam jacking devices to close the mid-span and conduct jacking tests; Step 6: Lift all the steel components of the middle span closure section and place them on the cantilever ends of the erected beam sections on both sides of the middle span closure, and weld the beam support components on the top plates of the side box beams; Step 7: Based on the status of step 6, evaluate and adjust the geometric posture of the mid-span closure; Step 8: When the side span closure construction is completed and the conditions for the middle span closure are met, push in the direction of the side span. When the push is in place, lock the push device; Step 9: The cranes on both sides of the middle span closure simultaneously lift one box girder each, move the box girder to the top of the middle span closure, and then slowly lower it. The box girders on both sides are inserted into the middle span closure and placed on the erected beam sections on both sides using the beam resting members in step 6. Step 10: Adjust the posture of the middle span closure and optimize the relative geometric position; Step 11: Unlock the jacking device and push it back toward the mid-span. Lock the jacking device after it is in place. Step 12: Splice the steel beams of the middle span closure section and the erected beam sections on both sides; Step 13: Remove all temporary restraints between tower and beam; Step 14: Install the cross beams and small longitudinal beams of the middle span closure section and construct the bridge deck, which means the middle span closure operation is completed; In step 5, the specific implementation process of converting the temporary constraint of the tower area into the main beam pushing device is as follows: First, install the jacking device and apply the pre-jacking force calculated by the calculation model, and then remove the longitudinal temporary restraint; Remove temporary transverse restraints between tower beams; The closure jacking device test is carried out according to the jacking stroke and jacking force required for the expected closure temperature.

2. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: In step 3, the specific operation of continuous temperature effect monitoring is: During the side span closure construction, the temperature effect of the beam sections erected on both sides of the middle span closure will be monitored continuously for 24 hours. The beam sections erected on both sides of the middle span closure will be jointly monitored every two hours. The monitoring content includes the temperature field, tower deflection, the elevation, mileage, axial deflection, mileage of the first three sections of the cantilever end on both sides of the middle span closure, and the tension of the inclined cables. The monitoring data were analyzed to obtain the inclination angle of the erected beam sections on both sides of the mid-span closure, the length of the mid-span closure and its changes under the influence of temperature. The calculation model is used to simulate heating and cooling to verify the accuracy of the monitoring data.

3. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: In step 6, the components used for the shelf beams are steel vertical plates or steel corbels.

4. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: In step 7, the specific implementation process of evaluating and adjusting the geometric posture of the mid-span closure is as follows: Measure the elevations of the first segment B and the second segment A before the cantilever end of the erected beam segments on both sides of the middle span closure; If the measuring point elevations of the front first section B and the front second section A are equal, or the measuring point elevation of the front first section B is slightly higher than that of the front second section A and the upstream and downstream elevations are consistent, the geometric posture of the mid-span closure will not be adjusted; If the elevation of the measuring point of the first section B is lower than that of the measuring point of the second section A, the tension of the inclined cable should be fine-tuned to raise the cantilever end beam section.

5. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: In step 8, after pushing into place, D=L+ d +S+∆ d , where D is the width of the middle span joint, L is the actual length of the box girder at the middle span joint section, d is the width of the joints on both sides of the middle span closure, S is the operating space at the two joint surfaces, ∆ d The change in the width of the mid-span closure caused by temperature change.

6. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: In step 10, the specific implementation process of adjusting the posture of the middle span joint is: first, fine-tune the relative elevation and inclination of the erected beam sections on both sides of the middle span joint by the cable force of the inclined cable, and then use the pulling device to diagonally pull the erected beam sections to fine-tune the axis.

7. The mid-span closure method for a long-span composite beam cable-stayed bridge according to any one of claims 1 to 6, characterized in that: In step 12, the specific implementation process of the splicing construction is: first, small punches are driven into the positioning bolt holes, and then the alignment accuracy of the bolt holes of the steel beam and the splicing plate is determined by evaluating the holes. If the alignment accuracy meets the requirements of the hole group bolting, small punches and tool bolts are driven into the other bolt holes, and then temporary code plates are welded to lock the joint surfaces on both sides of the mid-span joint at the same time, and then high-strength bolts are tightened; if the alignment accuracy does not meet the requirements of the hole group bolting and the small punches and tool bolts cannot be driven in, the geometric posture of the erected beam sections on both sides of the mid-span joint is adjusted again.

8. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 7, characterized in that: The specific implementation process of driving the small rivets into the positioning bolt holes is as follows: when the main beams on both sides of the splicing surface are tilted upward, first drive the small rivets into the two middle bolt holes in the bottom row of bolt holes, and then drive the small rivets into one of the outermost bolt holes in the top row of bolt holes; When the main beams on both sides of the splicing surface tilt downward, first drive small rivets into the two middle bolt holes in the uppermost row of bolt holes, and then drive small rivets into one of the outermost bolt holes in the lowermost row of bolt holes.

9. The mid-span closure method for a long-span composite beam cable-stayed bridge according to claim 1, characterized in that: Between step 9 and step 10, the method further includes the step of swinging the crane boom back and centering it in the transverse direction of the bridge.

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