Construction method for mounting mid-span closure section of double-layer steel truss girder

Abstract

The invention discloses a construction method for mounting a mid-span closure section of a double-layer steel truss girder, which is characterized in that the position and the angle of a closure section splicing port are finely adjusted through the combination of a longitudinal limiting bracket and a 800t jack, so that the steel truss girder of the closure section is convenient to mount, the stability of the steel truss girder is enhanced, and the mounting precision of the steel truss girder of the closure section is ensured; the construction risk of overturning of the steel truss girder is reduced; and then through construction devices such as a temporary matching piece, a transverse opposite-pulling lug seat obliquely penetrating opposite-pulling steel strand, a longitudinal jack, a vertical jack, a transverse counter-force jack and an axial opposite-jacking jack, and with the assistance of stay cable force adjustment and weight measures, rapid and accurate butt joint of the closure section steel truss girder is completed, transverse, vertical and longitudinal deviation is reduced, and the construction efficiency is improved. And the structural deformation is controllable in the installation process of the closure section steel truss girder. Adjusting devices adopted in the method are all of temporary detachable structures and can be rapidly mounted and dismounted; according to the method, linear adjustment is faster, the adjustment precision is higher, and the method is safer and more reliable.

Description

Technical Field

[0001] The invention relates to the technical field of installation of a mid-span closure section of a double-layer steel truss girder, and in particular to a construction method for installation of a mid-span closure section of a double-layer steel truss girder. Background Art

[0002] In the field of bridge construction, especially the construction of large-span double-deck steel truss bridges, mid-span closure is a critical and complex process. Mid-span closure not only involves the overall stability and safety of the bridge structure, but also the closure accuracy has a great impact on the line shape and structural internal force of the bridge after completion. The traditional mid-span closure method often uses the method of dragging and adjusting the guide chain and welding temporary fixation. Although this method can achieve closure, there are many shortcomings in the construction process, including the following problems: 1. The linear accuracy after the chain guide dragging adjustment is low, the linear adjustment is difficult, and the adjustment work is cumbersome; 2. The workload of temporary welding and fixing is large, and rapid alignment cannot be achieved; 3. When installing the steel trusses at the joint section, they will expand and deform due to temperature changes, making it difficult to accurately dock them; 4. The traditional method of installing steel trusses in the joint section does not set protective measures for the steel trusses in other sections, and there is a safety risk that the steel trusses in other sections may overturn during the adjustment process. Summary of the invention

[0003] The purpose of the present invention is to provide a construction method for installing a mid-span closure section of a double-layer steel truss beam.

[0004] The object of the present invention is achieved in that: A construction method for installing a mid-span closure section of a double-layer steel truss beam is characterized by the following specific steps: Step 1: After the construction of the No. 1 main tower side steel truss and the No. 2 main tower side steel truss is completed, the length of the upper chord and the lower chord, the length of the diagonal rod and the angle of the diagonal rod of the joint section steel truss are predicted according to the actual compression amount and calculation, and the cutting is carried out in the factory; on the top surface of the upper segment of the No. 1 main tower side steel truss and the No. 2 main tower side steel truss adjacent to the joint section steel truss, two triangular brackets are symmetrically arranged with the center line of the steel truss, and a flexible head is welded on each triangular bracket on the top surface of the upper segment of the No. 2 main tower side steel truss, and the supporting steel is connected to each flexible head, and the supporting steel is welded to the triangular bracket corresponding to the top surface of the upper segment of the No. 1 main tower side steel truss and along the bridge direction, and each two triangular brackets perpendicular to the bridge direction are welded and connected with the supporting steel to form a stable frame; the flexible head is pre-extended by 10cm and locked; Step 2: After the first beam crane has completed the erection of the first segment of the steel truss on the side of the No. 1 main tower, it will retreat 2.6m toward the side span; the second beam crane will move 16m toward the mid-span to the top of the vertical bar node of the steel truss on the side of the No. 2 main tower; the second beam crane will be used to connect the steel truss of the joint section below the joint section joint interface as a whole; Step 3: longitudinal limit brackets are set at the bottom of the side span and middle span of the steel trusses on the top of the No. 1 main tower and the No. 2 main tower, and an 800t jack is installed between the longitudinal limit bracket and the cushion stone on each side span, and a cushion block support is set between the longitudinal limit bracket and the cushion stone on the middle span; the second beam crane lifts the steel trusses of the joint section to the bottom of the joint section joint interface; since the steel truss support type on the top of the No. 1 main tower or the No. 2 main tower is a multi-directional movable support, the steel trusses are still in a movable state. At this time, the 800t jacks at the longitudinal limit brackets of the No. 1 main tower and the No. 2 main tower apply horizontal thrust to make the steel trusses on both sides move 10cm toward the side span respectively. After the movable head is unlocked, it extends 20cm as the steel trusses move, and the joint section joint interface expands to both sides, thereby meeting the lifting space requirements of the steel trusses of the joint section, which is convenient for the installation of the steel trusses of the joint section; Step 4: Under the temperature conditions required by the design, the second beam crane lifts the steel truss of the joint section to the designed position of the joint section joint interface, and adjusts the elevation of the steel truss of the joint section; the longitudinal and vertical alignment deviations of the steel truss of the joint section and the steel truss of the side of the No. 2 main tower are adjusted to within 5mm through the guide chain. After successful alignment, the 800t jack at the longitudinal limit bracket is stopped for pressurization, and the 800t jack is self-locked with the active head to connect the steel truss of the joint section with the steel truss of the side of the No. 2 main tower into a whole; Step 5: Release the lock of the active head, and the 800t jacks of the longitudinal limit brackets on the No. 1 and No. 2 main towers begin to return oil, so that the steel trusses on the side of the No. 1 main tower and the No. 2 main tower move toward the middle span as a whole, and after the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower is reduced to 10cm, the active head is locked. At this time, the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower is locked by the supporting steel, and then the 800t jack is released; Step 6: Since the steel trusses will be greatly deformed due to temperature changes, the steel trusses of the joint section cannot be accurately aligned during the docking process; after completing step 5, wait for the weather to warm up, release the lock of the active head, and allow the steel trusses on the side of the No. 1 main tower and the steel trusses of the joint section to expand vertically, longitudinally and horizontally as the weather temperature rises, so as to gradually move closer, further reducing the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower. At this time, the active head of the steel trusses on the side of the No. 2 main tower also shrinks with the expansion of the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower; after the temperature stabilizes, the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower meets the docking conditions, and the steel trusses will not be greatly deformed before the temperature drops at night; temporary matching parts are set at the joints between the lower segments of the steel trusses on the side of the No. 1 main tower and the lower segments of the steel trusses of the joint section; Step 7: The first beam crane retreats to the side span of the No. 1 main tower to the vicinity of the No. 1 main tower; transverse tie lugs are set on the top of the lower segments of the No. 1 main tower side steel truss and the joint section steel truss, and the tie steel strands are obliquely inserted between the two transverse tie lugs. By tensioning the tie steel strands, the deviation of the horizontal and vertical axes of the No. 1 main tower side steel truss and the joint section steel truss plane is adjusted to no more than 10mm; at the same time, water bags can be set above the nodes of the vertical bars of the steel truss of the previous segment of the No. 1 main tower side steel truss for weighting according to the calculation requirements, and the oblique The cable force is used to initially ensure that the vertical and longitudinal deviations of the joint section steel truss and the lower segment of the No. 1 main tower side steel truss are no more than 5mm; after the joint section steel truss and the lower segment of the No. 1 main tower side steel truss meet the temporary connection accuracy requirements, the vertical and transverse positions of the joint are temporarily locked to make the joint section steel truss parallel to the lower chord of the No. 1 main tower side steel truss. After the joint section steel truss and the lower segment of the No. 1 main tower side steel truss are basically overlapped, 50% of the number of nails and 30% of the number of high-strength bolts are driven in; Step 8: Set longitudinal jacks and vertical jacks at the joints between the No. 1 main tower side steel truss and the upper segment top surface of the joint section steel truss, further fine-tune the vertical deviation and longitudinal deviation at the joints of the upper segment top surface, and drive in 50% of the number of nails and 30% of the number of high-strength bolts after meeting the temporary connection accuracy requirements, to complete the temporary connection between the No. 1 main tower side steel truss and the upper segment of the joint section steel truss; Step 9: Set up transverse reaction jacks and axial top jacks at the diagonal bar splicing of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section. Both the transverse reaction jacks and the axial top jacks are welded and fixed to the diagonal bars of the steel truss; adjust the transverse, vertical and longitudinal accuracy of the diagonal bar splicing of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section by using the transverse reaction jacks and the axial top jacks; when the transverse, vertical and longitudinal deviations of the diagonal bar splicing are not greater than 5mm, drive 50% of the number of nails and 30% of the number of high-strength bolts into the splicing of the diagonal bars to lock the splicing parts, and then gradually replace all the nails at the splicing parts of the diagonal bars with high-strength bolts and complete them, completing the diagonal bar connection between the steel truss on the side of the No. 1 main tower and the steel truss of the joint section; Step 10: gradually replace the punch pins in all the joints with high-strength bolts, and complete the high-strength bolts, and tighten the high-strength bolts in the order of initial tightening and final tightening; remove the temporary matching parts; weld the upper and lower segments of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section to complete the joint of the double-layer steel truss.

[0005] Furthermore, in step three, before the overall longitudinal displacement of the steel truss by the 800t jack at the longitudinal limit corbel, the joint section joint interface should be continuously observed to determine the optimal construction temperature of the steel truss of the joint section; and the changes in the elevation and mileage of the joint section joint interface before and after the longitudinal displacement should be recorded at night to provide a reference for subsequent adjustments.

[0006] Furthermore, in step 4, when the steel trusses of the joint section are spliced ​​with the steel trusses on the sides of the No. 1 main tower and the No. 2 main tower, the Y direction (lateral) deviation should be adjusted first, so that the plane deviation of the centerline of the steel trusses before and after the joint section is within 5mm; then the Z direction (vertical) height difference should be adjusted, so that the relative deviation value of the joint section joint in the Z direction is reduced to within 5mm; then the X direction (longitudinal) distance should be adjusted, so that the rivets and high-strength bolts at various parts can be driven in smoothly.

[0007] Furthermore, in step 4, when the steel truss of the joint section is connected with the steel truss on the side of the No. 2 main tower, the docking sequence of the lower chord → the diagonal rod → the upper chord is followed, and the spikes and high-strength bolts are evenly driven in. The number of spikes should meet the 50% quantity requirement, and the high-strength bolts should meet the 30% quantity requirement and are generally tightened. If the guide chain adjustment accuracy cannot meet the full alignment of the spikes, the alignment accuracy should be further improved by adjusting the cable force or weight. When the steel truss of the joint section is connected with the steel truss on the side of the No. 1 main tower, the construction is carried out in the docking sequence of the lower chord → the upper chord → the diagonal rod. The steel truss is finely adjusted and aligned by setting the lateral reaction jack, axial top jack, longitudinal jack, vertical jack and lateral pulling ear seat device in combination with the cable force adjustment and weighting measures.

[0008] Furthermore, in step six, the temporary matching parts are composed of two matching corbels, and the two matching corbels are respectively located on both sides of the joint between the steel truss of the joint section and the steel truss of the side of the No. 1 main tower. A pad steel block is arranged between the two matching corbels, and the pad steel block is spot welded and fixed to the matching corbels on both sides to avoid damage caused by the counter-impact force.

[0009] Furthermore, in step seven, the transverse tie ear seats are welded from steel, and a total of four are provided; two transverse tie ear seats of the first group are welded near the top surface of the upper segment of the steel truss beam on the side of the No. 1 main tower near the splicing of the steel truss beam of the joint section, and the center lines of the two transverse tie ear seats of the first group should be located 4.6m to the right of the central axis of the steel truss beam; the second group of transverse tie ear seats are also provided at the splicing of the steel truss beam on the side of the No. 1 main tower on the bridge deck of the upper segment of the steel truss beam of the joint section Two transverse tensioning ear seats, the center lines of the two transverse tensioning ear seats of the second group are located 4.6m to the left of the central axis of the steel truss, and the four transverse tensioning ear seats on the side steel truss of No. 1 main tower and on the steel truss of the joint section are arranged in a "parallelogram" as a whole; the four transverse tensioning ear seats use the center line of the steel truss as the dividing line, and the transverse tensioning ear seats on the left and right sides of the center line of the steel truss are connected in pairs by oblique tensioning steel strands, and the transverse deviation correction of the steel truss is achieved by tensioning the tensioning steel strands at one end.

[0010] Furthermore, in steps eight and nine, the longitudinal jack, vertical jack, transverse reaction jack and axial top jack are all detachable structures, and the longitudinal jack and vertical jack are welded and fixed to the top surface of the upper segment of the steel truss; the transverse reaction jack and axial top jack are welded and fixed to the diagonal rod of the steel truss; the vertical jack and transverse reaction jack are L-shaped structures, and the longitudinal jack and axial top jack are I-shaped structures. The lateral reaction jack is arranged on the lateral side of each diagonal rod, and can cause the diagonal rod to be displaced laterally; the axial top jack is arranged on the upper surface or the lower surface of each diagonal rod, and the axis of the axial top jack is always parallel to the axis of the diagonal rod, and the diagonal rod can be displaced in the axial direction through axial telescopic expansion; a plurality of longitudinal jacks and vertical jacks are symmetrically arranged on the top surface of the upper segments of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower with the central axis of the steel truss; the longitudinal jack and the vertical jack connect the two steel trusses to be spliced, and the vertical and longitudinal accuracy of the splicing parts of the upper segments of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower or the steel truss on the side of the No. 2 main tower are further improved by jacking and returning the oil.

[0011] Furthermore, the movable head is extended 10cm in advance, and when the 800t jack of the longitudinal limiting corbel is lifted, the joint section joint is stretched 20cm in total, and the movable head is extended 30cm at this time; when the 800t jack returns the oil, the steel trusses on the side of the No. 1 main tower and the steel trusses on the side of the No. 2 main tower are returned to their original positions, and the movable head is extended 10cm at this time; after the steel trusses on the side of the No. 1 main tower and the steel trusses in the joint section expand and displace with the increase of temperature, they continue to approach each other and drive the movable head to retract until the steel trusses on the side of the No. 1 main tower and the steel trusses in the joint section are stably fitted; the movable head is extended 10cm in advance to ensure that the steel trusses in the joint section and the steel trusses on the side of the No. 1 main tower have a spatial distance to adapt to temperature deformation.

[0012] The present invention arranges two transverse tensioning ear seats on the top surface of the steel truss and obliquely passes the tensioning steel strands through them, so that the transverse deviation between the steel truss of the joint section and the steel truss on the side of the No. 1 main tower is reduced, and the alignment axis deviation of the steel truss is adjusted to reduce the relative transverse deviation of the steel truss of the joint section to within 5 mm, thereby realizing transverse fine adjustment; by adjusting the cable force of the inclined cable and supplemented by the weighting measures of the steel truss on the side of the No. 1 main tower, the vertical and longitudinal relative deviations of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower are reduced to within 5 mm, thereby realizing vertical and longitudinal fine adjustment, and completing the temporary connection of the lower chord of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower; when the joint temperature required by the design is reached, the steel truss of the joint section and the steel truss on the side of the No. 1 main tower are connected by the The longitudinal jacks and vertical jacks of the upper segment bridge deck reduce the vertical and longitudinal relative deviation values ​​at the joint of the upper chord, so that the upper chord can be accurately aligned and connected; the transverse reaction jacks and axial top jacks are then used to reduce the transverse, vertical and longitudinal relative deviation values ​​at the joint of the steel truss of the joint section and the diagonal bars of the steel truss on the side of the No. 1 main tower, so as to complete the accurate alignment connection of the joint of the diagonal bars, complete the accurate positioning of the temporary connection of the steel truss of the entire joint section, and improve the joint accuracy of the steel truss of the joint section; the transverse pulling ear seat, longitudinal jack, vertical jack, transverse reaction jack and axial top jack of the present invention can be quickly installed and disassembled, and at the same time, the workload of linear adjustment is reduced, the adjustment is more convenient, and the adjustment accuracy is higher.

[0013] At the same time, the combination of longitudinal limit brackets and 800t jacks at the pad stones of the No. 1 and No. 2 main towers is used to adaptively adjust the spacing of the joint section joints to ensure the installation space of the joint section steel trusses and the spacing adjustment between the joint section steel trusses and the side steel trusses of the No. 1 main tower; at the same time, the combination of longitudinal limit brackets and 800t jacks can clamp the sides of the supporting pad stones, further enhancing the stability of other steel trusses during the installation of the joint section steel trusses, and indirectly ensuring the installation accuracy of the joint section steel trusses. The support steel and the flexible joint can replace the 800t jack to support and adjust the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower, and maintain the stability of the overall posture of all the steel trusses. At the same time, the flexible joint can be used to make the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower to expand and displace adaptively due to temperature changes in advance, so as to avoid the expansion of the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower due to temperature during docking, which makes it impossible to accurately align them.

[0014] In addition, temporary matching parts can quickly fix the joints between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower or the steel trusses on the side of the No. 2 main tower, ensuring the stability of the steel trusses during the adjustment process and facilitating subsequent fine-tuning and welding operations.

[0015] Therefore, the present invention has the following advantages: 1. Through the combination of longitudinal limit brackets and 800t jacks, the position and angle of the joint section joint interface are fine-tuned to facilitate the installation of the steel truss beam in the joint section, enhance the stability of the steel truss beam, ensure the installation accuracy of the steel truss beam in the joint section, and reduce the construction risk of steel truss beam overturning; 2. Through temporary matching parts, transverse tie-up lugs, oblique tie-up steel strands, longitudinal jacks, vertical jacks, transverse reaction jacks, axial top jacks and other construction devices, supplemented by the cable force adjustment and weighting measures of the inclined cables, the steel trusses of the joint section can be quickly and accurately docked, reducing the transverse, vertical and longitudinal deviations, so that the structural deformation of the steel trusses of the joint section can be controlled during the installation process; 3. The adjustment devices used are all temporary detachable structures and can be quickly installed and disassembled; 4. Linear adjustment is faster, more accurate, safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the bridge-forming state of the present invention; Figure 2 This is a state diagram of the joint connection when the closure section steel truss girder of the present invention is not hoisted; Figure 3 It is a side schematic diagram of the steel truss girder of the lifting and closing section of the present invention; Figure 4 It is a structural diagram of the steel truss girder in the closing section; Figure 5 It is a schematic diagram of the adjustment plan of the top surface of the lower segment of the closure section steel truss and the side steel truss of the No. 1 main tower; Figure 6 It is a schematic diagram of the adjustment plan of the top surface of the upper segment of the closing section steel truss and the side steel truss of the No. 1 main tower; Figure 7 It is a structural schematic diagram of the temporary matching part of the present invention; Figure 8 It is a structural schematic diagram of the vertical jack of the present invention; Fig. 9 It is a structural schematic diagram of the longitudinal jack of the present invention; Fig.10 It is a schematic diagram of the adjustment of the diagonal rod of the present invention; Fig.11 It is a structural schematic diagram of the transverse reaction jack of the diagonal rod joint of the present invention; Fig.12 It is a structural schematic diagram of the axial top jack of the diagonal rod joint of the present invention; Fig.13 It is a schematic diagram of the front structure of the transverse pulling ear seat; Fig.14 for Fig.13 Schematic side view of Fig.15 This is the cross-sectional view of the longitudinal limit bracket of No. 1 main tower or No. 2 main tower and the 800t jack along the bridge direction; Numbers in the figure: 1, main tower No. 1; 2, main tower No. 2; 3, cable stay; 4, pad stone; 5, steel truss; 51, steel truss on the side of main tower No. 1; 52, steel truss on the side of main tower No. 2; 53, steel truss on the closing section; 54, upper chord; 55, lower chord; 56, diagonal rod; 561, vertical rod; 57, closing section joint; 58, upper segment; 59, lower segment; 6, first beam crane; 7, second beam Crane; 8. 800t jack; 9. Longitudinal limit corbel; 91. Pad; 10. Triangular corbel; 11. Active head; 12. Support steel; 13. Temporary matching parts; 131. Matching corbel; 132. Pad steel block; 14. Horizontal tensioning ear seat; 141. Tensioning steel strand; 15; Longitudinal jack; 16. Vertical jack; 17. Horizontal reaction jack; 18. Axial top jack. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] See also Figure 1-15 A construction method for installing the mid-span closure section of a double-layer steel truss beam, the specific steps are as follows Step 1: After the construction of the No. 1 main tower side steel truss 51 and the No. 2 main tower side steel truss 52 is completed, the length of the upper chord 54 and the lower chord 55 of the joint section steel truss 53, the length of the diagonal bar 56 and the angle of the diagonal bar 56 are predicted according to the actual compression amount and calculation, and the cutting is carried out in the factory; on the top surface of the upper segment 58 of the No. 1 main tower side steel truss 51 and the No. 2 main tower side steel truss 52 adjacent to the joint section steel truss 53, two triangular brackets are symmetrically arranged with the center line of the steel truss 5 10, and weld a flexible head 11 on each triangular bracket 10 on the top surface of the upper segment 58 of the steel truss beam 52 on the side of the second main tower, and connect the supporting steel 12 on each flexible head 11, weld the supporting steel 12 to the triangular bracket 10 along the bridge direction corresponding to the top surface of the upper segment 58 of the steel truss beam 51 on the side of the first main tower, and weld two triangular brackets 10 in each perpendicular bridge direction with the supporting steel 12 to form a stable frame; the flexible head 11 is extended in advance by 10 cm and locked; Step 2: After the first beam crane 6 has completed the erection of the previous segment of the steel truss beam 51 on the side of the No. 1 main tower, it retreats 2.6m in the side span direction; the second beam crane 7 moves 16m in the mid-span direction to the top of the vertical rod 561 node of the steel truss beam 52 on the side of the No. 2 main tower; the second beam crane 7 is used to integrally connect the joint section steel truss beam 53 below the joint section joint 57; Step 3: longitudinal limit brackets 9 are set at the bottom of the side span and middle span of the steel truss beam 5 on the top of the No. 1 main tower 1 and the No. 2 main tower 2, and an 800t jack 8 is installed between the longitudinal limit bracket 9 and the cushion stone 4 on each side span, and a cushion block 91 is set between the longitudinal limit bracket 9 and the cushion stone 4 on the middle span side; the second beam crane 7 lifts the joint section steel truss beam 53 to the bottom of the joint section joint 57; since the support type of the steel truss beam 5 on the top of the No. 1 main tower 1 or the No. 2 main tower 2 is multi- To the movable support, so the steel truss 5 is still in a movable state, at this time, the 800t jack 8 at the longitudinal limit bracket 9 of the No. 1 main tower 1 and the No. 2 main tower 2 applies a horizontal thrust to make the steel trusses 5 on both sides move 10cm to the side span respectively, and the movable head 11 is unlocked and extends 20cm with the displacement of the steel truss 5, and the joint section joint 57 is expanded to both sides, thereby meeting the lifting space requirements of the joint section steel truss 53, which is convenient for the installation of the joint section steel truss 53; Step 4: Under the temperature conditions required by the design, the second beam crane 7 lifts the joint section steel truss 53 to the designed position of the joint section joint interface 57, and adjusts the elevation of the joint section steel truss 53; the longitudinal and vertical alignment deviations of the joint section steel truss 53 and the No. 2 main tower side steel truss 52 are controlled within 5 mm by the guide chain, and after successful alignment, the 800t jack 8 at the longitudinal limit bracket 9 is stopped for pressurization, and the 800t jack 8 is self-locked with the active head 11 to connect the joint section steel truss 53 and the No. 2 main tower side steel truss 52 into a whole; Step 5: Release the lock of the active head 11, and the 800t jack 8 of the longitudinal limit bracket 9 on the No. 1 main tower 1 and the No. 2 main tower 2 starts to return oil, so that the No. 1 main tower side steel truss 51 and the No. 2 main tower side steel truss 52 are moved to the middle span side as a whole, and the spacing between the joint section steel truss 53 and the No. 1 main tower side steel truss 51 is reduced to 10cm, and then the active head 11 is locked. At this time, the spacing between the joint section steel truss 53 and the No. 1 main tower side steel truss 51 is locked by the supporting steel 12, and then the 800t jack 8 is released; Step 6: Since the steel truss 5 will be greatly deformed due to temperature changes, the joint section steel truss 53 cannot be accurately aligned during the docking process; after completing step 5, wait for the weather to warm up, release the lock of the active head 11, and allow the No. 1 main tower side steel truss 51 and the joint section steel truss 53 to expand vertically, longitudinally, and transversely as the weather temperature rises, so as to gradually move closer, further reducing the distance between the joint section steel truss 53 and the No. 1 main tower side steel truss 51. At this time The movable head 11 of the No. 2 main tower side steel truss 52 also shrinks with the expansion of the joint section steel truss 53 and the No. 1 main tower side steel truss 51; after the temperature stabilizes, the distance between the joint section steel truss 53 and the No. 1 main tower side steel truss 51 meets the docking condition, and before the temperature drops at night, the steel truss 5 will not be greatly deformed; a temporary matching piece 13 is set at the joint of the lower segment 59 of the No. 1 main tower side steel truss 51 and the lower segment 59 of the joint section steel truss 53; Step 7: The first beam crane 6 retreats to the side span side of the No. 1 main tower 1 to the vicinity of the No. 1 main tower 1; transverse pull-in ears 14 are set on the top of the lower segment 59 of the No. 1 main tower side steel truss 51 and the joint section steel truss 53, and the pull-in steel strands 141 are obliquely passed between the two transverse pull-in ears 14. The deviation of the horizontal and vertical axes of the No. 1 main tower side steel truss 51 and the joint section steel truss 53 is adjusted to be no more than 10mm by tensioning the pull-in steel strands 141; at the same time, a water bag can be set above the node of the vertical rod 561 of the steel truss 5 of the previous segment of the No. 1 main tower side steel truss 51 according to the calculation requirements for weighting, and adjusting The cable force of the inclined cable 3 is adjusted to preliminarily ensure that the vertical and longitudinal deviations of the joint of the joint section steel truss 53 and the lower segment 59 of the No. 1 main tower side steel truss 51 are not greater than 5mm; after the joint of the joint section steel truss 53 and the lower segment 59 of the No. 1 main tower side steel truss 51 meets the temporary connection accuracy requirements, the vertical and transverse positions of the joint are temporarily locked, so that the joint section steel truss 53 and the lower chord 55 of the No. 1 main tower side steel truss 51 are parallel and aligned, and after the joint of the joint section steel truss 53 and the lower segment 59 of the No. 1 main tower side steel truss 51 are basically overlapped, 50% of the number of nails and 30% of the number of high-strength bolts are driven in; Step 8: longitudinal jacks 15 and vertical jacks 16 are set at the joints between the No. 1 main tower side steel truss 51 and the upper segment 58 of the joint section steel truss 53, and the vertical deviation and longitudinal deviation of the joints at the upper segment 58 are further fine-tuned. After the temporary connection accuracy requirements are met, 50% of the number of nails and 30% of the number of high-strength bolts are driven in to complete the temporary connection between the No. 1 main tower side steel truss 51 and the upper segment 58 of the joint section steel truss 53; Step nine: a transverse reaction jack 17 and an axial top jack 18 are set at the splicing place of the diagonal rod 56 of the steel truss 51 on the side of the No. 1 main tower and the joint section steel truss 53, and the transverse reaction jack 17 and the axial top jack 18 are welded and fixed to the diagonal rod 56 of the steel truss 5; the transverse reaction jack 17 and the axial top jack 18 are used to adjust the transverse, vertical and longitudinal accuracy of the splicing place of the diagonal rod 56 of the steel truss 51 on the side of the No. 1 main tower and the joint section steel truss 53; when the transverse, vertical and longitudinal deviations of the splicing place of the diagonal rod 56 are not more than 5mm, 50% of the number of rivets and 30% of the number of high-strength bolts are driven into the splicing place of the diagonal rod 56 to lock the splicing part, and then gradually replace all the rivets at the splicing part of the diagonal rod 56 with high-strength bolts and complete them, and complete the connection of the diagonal rod 56 of the steel truss 51 on the side of the No. 1 main tower and the joint section steel truss 53; Step 10: gradually replace the rivets at all joints with high-strength bolts, complete the high-strength bolts, and tighten the high-strength bolts in the order of initial tightening and final tightening; remove the temporary matching parts 13; weld the upper segment 58 and the lower segment 59 of the No. 1 main tower side steel truss 51 and the joint section steel truss 53 to complete the joint of the double-layer steel truss 5.

[0019] Furthermore, in step three, before the steel truss 5 is longitudinally moved as a whole by the 800t jack 8 at the longitudinal limit corbel 9, the joint section joint 57 should be continuously observed to determine the optimal construction temperature of the steel truss 53 of the joint section; and the changes in the elevation and mileage of the joint section joint 57 before and after the longitudinal movement should be recorded at night to provide a reference for subsequent adjustments.

[0020] Furthermore, in step 4, when the joint section steel truss 53 is spliced ​​with the No. 1 main tower side steel truss 51 and the No. 2 main tower side steel truss 52 respectively, the Y direction (transverse) deviation should be adjusted first, so that the plane deviation of the truss centerline of the steel truss 5 before and after the joint section splicing interface 57 is within 5 mm; then the Z direction (vertical) height difference is adjusted, so that the relative deviation value of the joint section splicing interface 57 in the Z direction is reduced to within 5 mm; then the X direction (longitudinal) distance is adjusted, so that the rivets and high-strength bolts at various parts can be driven in smoothly.

[0021] Furthermore, in step 4, when the joint section steel truss 53 is connected to the side steel truss 52 of the No. 2 main tower, the docking sequence of the lower chord 55 → the diagonal rod 56 → the upper chord 54 is followed, and the spikes and high-strength bolts are evenly driven in. The number of spikes should meet the 50% quantity requirement, and the high-strength bolts should meet the 30% quantity requirement and are generally tightened. If the guide chain adjustment accuracy cannot meet the full alignment of the spikes, the alignment accuracy should be further improved by adjusting the cable force or pressing weight; when the joint section steel truss 53 is connected to the side steel truss 51 of the No. 1 main tower, the construction is carried out in the docking sequence of the lower chord 55 → the upper chord 54 → the diagonal rod 56, and the steel truss 5 is finely adjusted and aligned by the transverse reaction jack 17, the axial top jack 18, the longitudinal jack 15, the vertical jack 16 and the transverse pulling ear seat 14 device, in combination with the cable force adjustment and pressing weight measures.

[0022] Furthermore, in step six, the temporary matching part 13 is composed of two matching corbels 131, and the two matching corbels 131 are respectively provided on both sides of the joint between the joint section steel truss 53 and the No. 1 main tower side steel truss 51, and a pad steel block 132 is provided between the two matching corbels 131, and the pad steel block 132 is spot welded and fixed to the matching corbels 131 on both sides to avoid damage caused by the counter-impact force.

[0023] Furthermore, in step seven, the transverse pulling ear seats 14 are welded from steel materials, and a total of four are provided; two transverse pulling ear seats 14 of the first group are welded near the top surface of the upper segment 58 of the No. 1 main tower side steel truss 51 near the splicing of the joint section steel truss 53, and the center line of the two transverse pulling ear seats 14 of the first group should be located 4.6m to the right of the central axis of the steel truss 5; two transverse pulling ear seats of the second group are also provided at the splicing of the upper segment 58 of the joint section steel truss 53 near the No. 1 main tower side steel truss 51. The center lines of the two transverse pulling ear seats 14 of the second group are located 4.6m to the left of the central axis of the steel truss 5, and the four transverse pulling ear seats 14 on the side steel truss 51 of the No. 1 main tower and on the steel truss 53 of the joint section are arranged in a "parallelogram" as a whole; the four transverse pulling ear seats 14 use the center line of the steel truss 5 as the dividing line, and the transverse pulling ear seats 14 on the left and right sides of the center line of the steel truss 5 are connected in pairs through oblique pulling steel strands 141, and the transverse deviation correction of the steel truss 5 is achieved by tensioning the pulling steel strands 141 at one end.

[0024] Furthermore, in steps eight and nine, the longitudinal jack 15, the vertical jack 16, the transverse reaction jack 17 and the axial top jack 18 are all detachable structures, and the longitudinal jack 15 and the vertical jack 16 are welded and fixed to the top surface of the upper segment 58 of the steel truss 5; the transverse reaction jack 17 and the axial top jack 18 are welded and fixed to the diagonal rod 56 of the steel truss 5; the vertical jack 16 and the transverse reaction jack 17 are L-shaped structures, and the longitudinal jack 15 and the axial top jack 18 are I-shaped structures. The lateral reaction jack 17 is arranged on the lateral side of each diagonal rod 56, and can cause the diagonal rod 56 to be displaced laterally; the axial top jack 18 is arranged on the upper surface or the lower surface of each diagonal rod 56, and the axis of the axial top jack 18 is always parallel to the axis of the diagonal rod 56, and the diagonal rod 56 can be displaced in the axial direction through axial telescoping; a plurality of longitudinal jacks 15 and vertical jacks 16 are symmetrically arranged on the top surface of the upper segment 58 of the steel truss 53 of the joint section and the steel truss 51 on the side of the No. 1 main tower with the central axis of the steel truss 5; the longitudinal jacks 15 and the vertical jacks 16 connect the two steel trusses 5 to be spliced, and further improve the vertical and longitudinal accuracy of the splicing part of the upper segment 58 of the steel truss 53 of the joint section and the steel truss 51 on the side of the No. 1 main tower or the steel truss 52 on the side of the No. 2 main tower by jacking and returning the oil.

[0025] Furthermore, the movable head 11 is extended 10 cm in advance. When the 800t jack 8 of the longitudinal limiting corbel 9 is lifted, the joint section joint 57 is stretched out by 20 cm in total, and the movable head 11 is extended 30 cm at this time. When the 800t jack 8 returns the oil, the No. 1 main tower side steel truss 51 and the No. 2 main tower side steel truss 52 return to their original positions, and the movable head 11 is extended 10 cm at this time. After the No. 1 main tower side steel truss 51 and the joint section steel truss 53 expand and displace as the temperature rises, they continue to approach each other and drive the movable head 11 to retract until the No. 1 main tower side steel truss 51 and the joint section steel truss 53 are stably fitted. The movable head 11 is extended 10 cm in advance to ensure that the joint section steel truss 53 and the No. 1 main tower side steel truss 51 have a spatial distance to adapt to temperature deformation.

[0026] The present invention arranges two transverse pulling ear seats 14 on the top surface of the steel truss 5 to obliquely penetrate the pulling steel strands 141, so as to reduce the transverse deviation between the joint section steel truss 53 and the No. 1 main tower side steel truss 51, adjust the alignment axis deviation of the steel truss 5, reduce the transverse relative deviation of the joint section steel truss 53 to within 5 mm, and realize transverse fine adjustment; by adjusting the cable force of the inclined cable 3 and supplementing the weighting measure of the No. 1 main tower side steel truss 51, the vertical and longitudinal relative deviation between the joint section steel truss 53 and the No. 1 main tower side steel truss 51 is reduced to within 5 mm, realize vertical and longitudinal fine adjustment, and complete the temporary connection between the joint section steel truss 53 and the No. 1 main tower side steel truss 51; when the joint temperature required by the design is reached, the upper node of the joint section steel truss 53 and the No. 1 main tower side steel truss 51 is used. The longitudinal jacks 15 and the vertical jacks 16 of the bridge deck of section 58 reduce the vertical and longitudinal relative deviation values ​​at the joint of the upper chord 54, so that the upper chord 54 is accurately aligned and connected; the transverse reaction jacks 17 and the axial top jacks 18 are then used to reduce the transverse, vertical and longitudinal relative deviation values ​​at the joint of the steel truss 53 of the joint section and the diagonal rods 56 of the side steel truss 51 of the No. 1 main tower, complete the accurate alignment connection at the joint of the diagonal rods 56, complete the accurate positioning of the temporary connection of the steel truss 53 of the entire joint section, and improve the joint accuracy of the steel truss 53 of the joint section; the transverse pulling ear seat 14, the longitudinal jack 15, the vertical jack 16, the transverse reaction jack 17 and the axial top jack 18 of the present invention can be quickly installed and disassembled, and at the same time, the workload of linear adjustment is reduced, the adjustment is more convenient, and the adjustment accuracy is higher.

[0027] At the same time, the combination of the longitudinal limit bracket 9 and the 800t jack 8 at the cushion stone 4 of the No. 1 main tower 1 and the No. 2 main tower 2 is used to adaptively adjust the spacing of the joint section joint interface 57 to ensure the installation space of the joint section steel truss 53 and the spacing adjustment between the joint section steel truss 53 and the No. 1 main tower side steel truss 51; at the same time, the combination of the longitudinal limit bracket 9 and the 800t jack 8 can clamp the side of the support cushion stone 4, further enhance the stability of other steel trusses 5 during the installation of the joint section steel truss 53, and ensure the installation accuracy of the joint section steel truss 53 from the side. The construction risk of the steel truss 5 overturning is reduced; the supporting steel 12 and the active head 11 can replace the 800t jack 8 to support and adjust the distance between the joint section steel truss 53 and the No. 1 main tower side steel truss 51, and maintain the stability of the overall posture of all the steel trusses 5. At the same time, the telescopic and adjustable characteristics of the active head 11 are used to make the joint section steel truss 53 and the No. 1 main tower side steel truss 51 adaptively expand and displace due to temperature changes in advance, so as to avoid the joint section steel truss 53 and the No. 1 main tower side steel truss 51 expanding due to temperature during docking and being unable to accurately align.

[0028] In addition, the temporary matching parts 13 can quickly fix the joints between the steel truss 53 of the joint section and the steel truss 51 on the side of the No. 1 main tower or the steel truss 52 on the side of the No. 2 main tower, ensuring the stability of the steel truss 5 during the adjustment process and facilitating subsequent fine-tuning and welding operations.

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A construction method for installing a mid-span closure section of a double-layer steel truss beam, characterized in that: The specific steps are as follows: Step 1: After the construction of the No. 1 main tower side steel truss and the No. 2 main tower side steel truss is completed, the length of the upper chord and the lower chord, the length of the diagonal rod and the angle of the diagonal rod of the joint section steel truss are predicted according to the actual compression amount and calculation, and the cutting is carried out in the factory; on the top surface of the upper segment of the No. 1 main tower side steel truss and the No. 2 main tower side steel truss adjacent to the joint section steel truss, two triangular brackets are symmetrically arranged with the center line of the steel truss, and a flexible head is welded on each triangular bracket on the top surface of the upper segment of the No. 2 main tower side steel truss, and the supporting steel is connected to each flexible head, and the supporting steel is welded to the triangular bracket corresponding to the top surface of the upper segment of the No. 1 main tower side steel truss and along the bridge direction, and each two triangular brackets perpendicular to the bridge direction are welded and connected with the supporting steel to form a stable frame; the flexible head is pre-extended by 10cm and locked; Step 2: After the first beam crane has completed the erection of the first segment of the steel truss beam on the side of the No. 1 main tower, it will retreat 2.6m in the direction of the side span; The second beam crane moves 16m towards the mid-span direction to the top of the vertical bar node of the steel truss on the side of the No. 2 main tower; the second beam crane is used to integrally connect the steel truss of the joint section below the joint section joint; Step 3: longitudinal limit brackets are set at the bottom of the side span and middle span of the steel trusses on the top of the No. 1 main tower and the No. 2 main tower, and an 800t jack is installed between the longitudinal limit bracket and the cushion stone on each side span, and a cushion block support is set between the longitudinal limit bracket and the cushion stone on the middle span; the second beam crane lifts the steel trusses of the joint section to the bottom of the joint section joint interface; since the steel truss support type on the top of the No. 1 main tower or the No. 2 main tower is a multi-directional movable support, the steel trusses are still in a movable state. At this time, the 800t jacks at the longitudinal limit brackets of the No. 1 main tower and the No. 2 main tower apply horizontal thrust to make the steel trusses on both sides move 10cm toward the side span respectively. After the movable head is unlocked, it extends 20cm as the steel trusses move, and the joint section joint interface expands to both sides, thereby meeting the lifting space requirements of the steel trusses of the joint section, which is convenient for the installation of the steel trusses of the joint section; Step 4: Under the temperature conditions required by the design, the second beam crane lifts the steel truss of the joint section to the designed position of the joint section joint interface, and adjusts the elevation of the steel truss of the joint section; the longitudinal and vertical alignment deviations of the steel truss of the joint section and the steel truss of the side of the No. 2 main tower are adjusted to within 5mm through the guide chain. After successful alignment, the 800t jack at the longitudinal limit bracket is stopped for pressurization, and the 800t jack is self-locked with the active head to connect the steel truss of the joint section with the steel truss of the side of the No. 2 main tower into a whole; Step 5: Release the lock of the active head, and the 800t jacks of the longitudinal limit brackets on the No. 1 and No. 2 main towers begin to return oil, so that the steel trusses on the side of the No. 1 main tower and the No. 2 main tower move toward the middle span as a whole, and after the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower is reduced to 10cm, the active head is locked. At this time, the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower is locked by the supporting steel, and then the 800t jack is released; Step 6: Since the steel trusses will be greatly deformed due to temperature changes, the steel trusses of the joint section cannot be accurately aligned during the docking process; after completing step 5, wait for the weather to warm up, release the lock of the active head, and allow the steel trusses on the side of the No. 1 main tower and the steel trusses of the joint section to expand vertically, longitudinally and horizontally as the weather temperature rises, so as to gradually move closer, further reducing the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower. At this time, the active head of the steel trusses on the side of the No. 2 main tower also shrinks with the expansion of the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower; after the temperature stabilizes, the distance between the steel trusses of the joint section and the steel trusses on the side of the No. 1 main tower meets the docking conditions, and the steel trusses will not be greatly deformed before the temperature drops at night; temporary matching parts are set at the joints between the lower segments of the steel trusses on the side of the No. 1 main tower and the lower segments of the steel trusses of the joint section; Step 7: The first beam crane retreats to the side span of the No. 1 main tower to the vicinity of the No. 1 main tower; transverse tie lugs are set on the top of the lower segments of the No. 1 main tower side steel truss and the joint section steel truss, and the tie steel strands are obliquely inserted between the two transverse tie lugs. By tensioning the tie steel strands, the deviation of the horizontal and vertical axes of the No. 1 main tower side steel truss and the joint section steel truss plane is adjusted to no more than 10mm; at the same time, water bags can be set above the nodes of the vertical bars of the steel truss of the previous segment of the No. 1 main tower side steel truss for weighting according to the calculation requirements, and the oblique The cable force is used to initially ensure that the vertical and longitudinal deviations of the joint section steel truss and the lower segment of the No. 1 main tower side steel truss are no more than 5mm; after the joint section steel truss and the lower segment of the No. 1 main tower side steel truss meet the temporary connection accuracy requirements, the vertical and transverse positions of the joint are temporarily locked to make the joint section steel truss parallel to the lower chord of the No. 1 main tower side steel truss. After the joint section steel truss and the lower segment of the No. 1 main tower side steel truss are basically overlapped, 50% of the number of nails and 30% of the number of high-strength bolts are driven in; Step 8: Set longitudinal jacks and vertical jacks at the joints between the No. 1 main tower side steel truss and the upper segment top surface of the joint section steel truss, further fine-tune the vertical deviation and longitudinal deviation at the joints of the upper segment top surface, and drive in 50% of the number of nails and 30% of the number of high-strength bolts after meeting the temporary connection accuracy requirements, to complete the temporary connection between the No. 1 main tower side steel truss and the upper segment of the joint section steel truss; Step 9: Set up transverse reaction jacks and axial top jacks at the diagonal bar splicing of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section. Both the transverse reaction jacks and the axial top jacks are welded and fixed to the diagonal bars of the steel truss; adjust the transverse, vertical and longitudinal accuracy of the diagonal bar splicing of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section by using the transverse reaction jacks and the axial top jacks; when the transverse, vertical and longitudinal deviations of the diagonal bar splicing are not greater than 5mm, drive 50% of the number of nails and 30% of the number of high-strength bolts into the splicing of the diagonal bars to lock the splicing parts, and then gradually replace all the nails at the splicing parts of the diagonal bars with high-strength bolts and complete them, completing the diagonal bar connection between the steel truss on the side of the No. 1 main tower and the steel truss of the joint section; Step 10: gradually replace the punch pins in all the joints with high-strength bolts, and complete the high-strength bolts, and tighten the high-strength bolts in the order of initial tightening and final tightening; remove the temporary matching parts; weld the upper and lower segments of the steel truss on the side of the No. 1 main tower and the steel truss of the joint section to complete the joint of the double-layer steel truss.

2. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: In step three, before the overall longitudinal displacement of the steel truss by the 800t jack at the longitudinal limit corbel, the joint section joint interface should be continuously observed to determine the optimal construction temperature of the steel truss of the joint section; and the changes in the elevation and mileage of the joint section joint interface before and after the longitudinal displacement should be recorded at night to provide a reference for subsequent adjustments.

3. The construction method for installing the mid-span closure section of a double-layer steel truss according to claim 1 is characterized in that: In step 4, when the joint section steel trusses are spliced ​​with the No. 1 main tower side steel trusses and the No. 2 main tower side steel trusses respectively, the Y direction (lateral) deviation should be adjusted first, so that the plane deviation of the truss centerline of the steel trusses before and after the joint section joint interface is within 5mm; then adjust the Z direction (vertical) height difference, so that the relative deviation value of the joint section joint interface in the Z direction is reduced to within 5mm; then adjust the X direction (longitudinal) distance, so that the rivets and high-strength bolts in various parts can be driven in smoothly.

4. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: In step 4, when the steel truss of the joint section is connected with the steel truss on the side of the No. 2 main tower, the docking sequence of lower chord → diagonal rod → upper chord is followed, and the nails and high-strength bolts are evenly driven in. The number of nails should meet the 50% quantity requirement, and the high-strength bolts should meet the 30% quantity requirement and are generally tightened. If the guide chain adjustment accuracy cannot meet the full alignment of the nails, the alignment accuracy should be further improved by adjusting the cable force or pressing weight; when the steel truss of the joint section is connected with the steel truss on the side of the No. 1 main tower, the construction is carried out in the docking sequence of lower chord → upper chord → diagonal rod. The steel truss is finely adjusted and aligned by setting up transverse reaction jacks, axial top jacks, longitudinal jacks, vertical jacks and transverse pulling ear seat devices, in combination with cable force adjustment and pressing weight measures.

5. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: In step six, the temporary matching parts are composed of two matching corbels, which are respectively located on both sides of the joint between the steel truss of the joint section and the steel truss on the side of the No. 1 main tower. A pad steel block is set between the two matching corbels, and the pad steel block is spot welded to the matching corbels on both sides to avoid damage caused by the counter-impact force.

6. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: In step seven, the transverse tie lugs are welded from steel, and a total of four are provided; two transverse tie lugs of the first group are welded near the top surface of the upper segment of the steel truss on the side of the No. 1 main tower near the splicing of the steel truss of the joint section, and the center line of the two transverse tie lugs of the first group should be located 4.6m to the right of the central axis of the steel truss; two transverse tie lugs of the second group are also provided at the splicing of the steel truss on the side of the No. 1 main tower on the bridge deck of the upper segment of the steel truss of the joint section near the steel truss of the No. 1 main tower, and the center line of the two transverse tie lugs of the second group is located 4.6m to the left of the central axis of the steel truss, and the four transverse tie lugs on the steel truss on the side of the No. 1 main tower and on the steel truss of the joint section are arranged in a "parallelogram" as a whole; the four transverse tie lugs use the center line of the steel truss as the dividing line, and the transverse tie lugs on the left and right sides of the center line of the steel truss are connected in pairs by oblique tie steel strands, and the lateral deviation correction of the steel truss is achieved by tensioning the tie steel strands at one end.

7. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: In steps eight and nine, the longitudinal jack, vertical jack, transverse reaction jack and axial top jack are all detachable structures. The longitudinal jack and vertical jack are welded and fixed to the top surface of the upper segment of the steel truss; the transverse reaction jack and axial top jack are welded and fixed to the diagonal rod of the steel truss; the vertical jack and transverse reaction jack are L-shaped structures, and the longitudinal jack and axial top jack are I-shaped structures. The lateral reaction jack is arranged on the lateral side of each diagonal rod, and can cause the diagonal rod to be displaced laterally; the axial top jack is arranged on the upper surface or the lower surface of each diagonal rod, and the axis of the axial top jack is always parallel to the axis of the diagonal rod, and the diagonal rod can be displaced in the axial direction through axial telescopic expansion; a plurality of longitudinal jacks and vertical jacks are symmetrically arranged on the top surface of the upper segments of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower with the central axis of the steel truss; the longitudinal jack and the vertical jack connect the two steel trusses to be spliced, and the vertical and longitudinal accuracy of the splicing parts of the upper segments of the steel truss of the joint section and the steel truss on the side of the No. 1 main tower or the steel truss on the side of the No. 2 main tower are further improved by jacking and returning the oil.

8. The construction method for installing the mid-span closure section of a double-layer steel truss beam according to claim 1 is characterized in that: The movable head is extended 10cm in advance. When the 800t jack of the longitudinal limiting corbel is lifted, the joint section joint is stretched 20cm in total, and the movable head is extended 30cm at this time. When the 800t jack returns the oil, the steel trusses on the side of the No. 1 main tower and the steel trusses on the side of the No. 2 main tower are returned to their original positions, and the movable head is extended 10cm at this time. After the steel trusses on the side of the No. 1 main tower and the steel trusses in the joint section expand and displace as the temperature rises, they continue to approach each other and drive the movable head to retract until the steel trusses on the side of the No. 1 main tower and the steel trusses in the joint section are stably fitted. The purpose of extending the movable head 10cm in advance is to ensure that the steel trusses in the joint section and the steel trusses on the side of the No. 1 main tower have a spatial distance to adapt to temperature deformation.

Images