Rapid erecting and dismantling method for large-span portal cast-in-place bent cap truss

Abstract

The invention discloses a rapid erecting and dismantling method for a large-span door type cast-in-place bent cap truss. The rapid erecting and dismantling method comprises the following steps that A, a plurality of vertical supports are erected, and two main trusses are installed, wherein A1, the vertical supports are installed, A2, the two main trusses are installed, and A3, a lower distribution beam and a bottom die are installed; b, dismantling the two main trusses and the vertical supports: B1) fixedly connecting the bottom die and the cast-in-place cover beam into a whole, B2) descending the vertical supports, B3) temporarily hanging the two main trusses, and B4) sequentially dismantling the main trusses and the vertical supports. According to the invention, the dismounting efficiency of the vertical bracket and the main truss is obviously improved, the construction cost is reduced, and the time of occupying public transportation is reduced. In the dismantling process, potential safety hazards of overhead high-voltage lines at the two ends of the main truss and traffic after opening are eliminated, and meanwhile, the construction method is also beneficial to construction in rainy seasons and on soft foundations.

Description

Technical Field

[0001] This invention relates to the field of urban bridge construction technology, and more specifically, to a method for the rapid erection and dismantling of a large-span portal cast-in-place cap beam truss with a span greater than 20m, constructed on existing urban roads, and which minimizes the impact on existing traffic flow. Background Technology

[0002] The cast-in-place cap beam truss of a city bridge project spans a four-lane, two-way, 12-lane urban main road. This main road experiences heavy traffic day and night. To maintain smooth traffic flow, construction is only permitted during the midnight to dawn closure of the middle two lanes (6 lanes in total), resulting in a short construction window. The cast-in-place cap beam truss, with its U-beams, is located adjacent to overhead high-voltage power lines at both ends, posing significant safety hazards and risks during its erection and dismantling. To minimize the impact on traffic flow on the main road and avoid endangering traffic safety, the cast-in-place cap beam truss must be dismantled within two nighttime construction periods. The various screw jacks, used for extended periods in harsh environments, bear the uneven and enormous loads transmitted from the cast-in-place cap beam, formwork, and truss, making unloading difficult. Furthermore, the two cantilevered ends of the cap beam's bottom formwork are close to overhead high-voltage power lines, lacking sufficient space for dismantling and removing the bottom formwork and distribution channel steel. Dismantling the cast-in-place cap beam truss in sections would extend the construction period. It not only affects traffic on the city's main roads, but also increases construction costs. Summary of the Invention

[0003] The purpose of this invention is to provide a safe and efficient method for the rapid erection and dismantling of large-span portal cast-in-place cap beam trusses.

[0004] This invention is achieved through the following technical solution: A method for rapid erection and dismantling of a large-span portal cast-in-place cap beam truss, wherein the large-span portal cast-in-place cap beam truss consists of two parallel main trusses. Each main truss includes a half-truss fixedly connected by a butt joint. The half-truss includes two sub-trusses fixedly connected end to end. The lower side of the main truss is supported by an upper support beam made of 400×400H-section steel and multiple spiral jacks, which are respectively supported on the top of the central pier assembly vertical support, several side pier assembly vertical supports, and the top of the side pier welded vertical support. The central pier assembly vertical support and the side pier assembly vertical support are respectively assembled into a cuboid frame by rectangular frame plates welded from 300×300H-section steel using multiple sets of high-strength bolts and nuts. On both sides of the side pier, there are also side pier welded vertical supports with cuboid frame structures made of 300×300H-section steel. The rapid erection and dismantling method includes: A) erecting several vertical supports and installing two main trusses, and B) dismantling the two main trusses and several vertical supports. The plurality of vertical supports include a central pier assembled vertical support and two side pier assembled vertical supports, as well as side pier welded vertical supports on both sides of each side pier assembled vertical support. A. Constructing several vertical supports and installing two main trusses includes the following steps: A1) The support foundation for the vertical support of the pier assembly, the vertical support of the side pier assembly, and the vertical support of the side pier welding is processed. The support foundation includes the original asphalt pavement and the excavated pier construction area. Dry soil containing 5% cement is replaced in the pier excavation area and compacted with a vibratory roller. A2) Install the bottom support components of the central pier assembly vertical support, the side pier assembly vertical support, and the side pier welded vertical support. On the upper side of the bottom support foundation, install several parallel concrete beams along the road direction. The positions of the concrete beams match the bottom positions of the central pier assembly vertical support, the side pier assembly vertical support, and the side pier welded vertical support, respectively. The bottom beams made of 700×700 H-shaped steel, which are perpendicular to the road direction and arranged side by side, are located on the lower side of the bottom of the central pier assembly vertical support, the side pier assembly vertical support, and the side pier welded vertical support, respectively, and correspond to the positions of the bottom plates of the central pier assembly vertical support, the side pier assembly vertical support, and the side pier welded vertical support. Multiple adjustable height sandboxes are respectively set between the bottom beams and the concrete beams. A3) Assemble the vertical support frame for the central pier surrounding the outer perimeter of the central pier and the vertical support frame for the side piers surrounding the outer perimeter of the side piers. Use a truck crane to lift each rectangular frame plate to the outer perimeter of the central pier and the outer perimeter of the side piers respectively. Then, fix each rectangular frame plate from bottom to top with multiple sets of high-strength bolts and nuts to form the vertical support frame for the central pier surrounding the outer perimeter of the central pier and the vertical support frame for the side piers surrounding the outer perimeter of the side piers. The bottom plates of the vertical support frame for the central pier and the vertical support frame for the side piers are respectively supported on the corresponding bottom beams. Then, use a truck crane to lift the vertical support frame for the side piers to the two sides of the corresponding side piers respectively, and support the bottom plates of the vertical support frame for the side piers on the corresponding bottom beams respectively. A4) Anchor screw jacks on the top plates of the vertical support assembled on the middle pier, the vertical support assembled on the side pier, and the vertical support welded on the side pier respectively. The top of the screw jacks respectively supports the upper support beam made of 400×400H steel parallel to the longitudinal direction of the road. A5) Install two main trusses. First, assemble four half-truss sections on the ground. Each half-truss section is formed by splicing and fixing two sub-truss sections end to end. Then, use a crawler crane to hoist two half-truss sections in sequence. Weld and anchor the lower sides of the two parallel half-truss sections to the top surface of the corresponding upper support beams. Next, use multiple diagonal bracing channel steels to temporarily fix the two ends of the upper support beams and the upper longitudinal beams of the corresponding half-trusses in sequence. Then, use the same method to hoist and weld the other two half-truss sections in sequence. On the corresponding upper support beam, multiple diagonal bracing channel steels are used to temporarily fix the upper longitudinal beams and upper support beams of the other two half-width trusses to improve the support stability of the main truss; the two parallel half-width trusses are fixed to each other on the upper and lower sides by arrays of high-strength bolts and nuts to form two parallel main trusses. Several portal beams made of 250×250 H-shaped steels arranged at intervals and perpendicular to the main trusses are welded and fixed to the upper longitudinal beams of the two main trusses to improve the stability of the cast-in-place cap beam truss; A6) Install the lower distribution beams and bottom formwork. On the ground, arrange multiple double-section 25# I-beams horizontally in parallel as lower distribution beams. Then, hoist the bottom formwork pieces onto the lower distribution beams and intermittently weld the bottom formwork pieces and the lower distribution beams together to form a whole. Next, hoist the bottom formwork pieces and the lower distribution beams together between the two main trusses and intermittently weld and anchor the ends of the lower distribution beams to the bottom longitudinal beams of the main trusses. The bottom formwork pieces connected end to end are then fixed together to form a whole bottom formwork. Then, install multiple stepped side formwork pieces that are fixed end to end. The two ends of the side formwork pieces that are fixed together are closed by end formwork. Then, carry out the reinforcement binding and installation before the cap beam is poured, as well as the installation of embedded pipes. Then, carry out the concrete pouring, graded prestressing tensioning of steel strands and grouting of prestressed pipes to complete all construction operations of the cast-in-place cap beam. B. Dismantle the two main trusses and each vertical support separately, including the following steps: B1) The bottom formwork is fixedly connected to the cast-in-place cap beam. After the prestressing tensioning is completed and the curing period of the cast-in-place cap beam is over, multiple parallel upper distribution beams are horizontally placed on the top surface of the cast-in-place cap beam. The upper distribution beams are made of double-jointed 20# channel steel welded together, and the distance between two upper distribution beams matches the distance between the two ends of the bottom formwork piece. Before removing the main truss, the welded anchorages between each lower distribution beam and the lower longitudinal beam of the main truss are removed. Then, the two ends of the upper distribution beams are connected to the bottom formwork through steel tie rods and steel nuts. The lower distribution beams under both ends of the slab are fixedly connected and tightened with steel nuts; the remaining lower distribution beams are fixedly connected to the cast-in-place cap beam by high-strength braided strips, that is, the two ends of the high-strength braided strips are fixedly connected to the two ends of the corresponding lower distribution beams respectively, and the middle of the high-strength braided strips in the taut state is pressed against the top surface of the cast-in-place cap beam, so that the bottom formwork and the lower distribution beams are fixedly connected to the cast-in-place cap beam as a whole; thereby avoiding the bottom formwork and the lower distribution beams from falling and pressing against the lower longitudinal beams of the two main trusses when the vertical support is lowered as a whole, which would make it difficult to disassemble the main trusses; B2) Lower each vertical support, remove the baffles on both sides of each sandbox, and simultaneously remove the sand from each sandbox. The top cover of each sandbox is lowered at the same time. The bottom beam and the middle pier assembled with vertical supports, the side pier assembled with vertical supports, and the side pier welded with vertical supports are all lowered by 5-7cm at the same time. The two main trusses are also lowered by 5-7cm. This allows the two ends of the lower distribution beam to detach from the lower longitudinal beams of the two main trusses, thus facilitating the disassembly of the two main trusses. B3) Hang hand-operated hoists at the reserved steel bars in the middle pier. The other end of the hand-operated hoist hooks onto the upper longitudinal beams of the main truss through steel wire ropes to temporarily suspend the two main trusses to prevent slippage caused by the center of gravity of the main truss deviating from the lifting point during lifting, which would endanger the overhead high-voltage lines outside the two ends of the main truss. Then, remove several portal beams on the upper side of the two main trusses, and then remove multiple sets of high-strength bolt and nut groups connecting the two half-span trusses. B4) Complete the dismantling of the main truss and each vertical support in sequence, close the single lane, use two truck cranes to lift two half-sections of the truss in sequence, and then remove each screw jack first, and then remove the multiple sets of high-strength bolt and nut groups of the middle pier assembly vertical support and the side pier assembly vertical support fixed to the upper and lower sections respectively from top to bottom; then lift each rectangular frame plate in sequence; then lift the four side pier welded vertical supports in sequence, then lift the bottom beam, remove all sand boxes, and complete the dismantling of the main truss and each vertical support; then carry out the dismantling of the side formwork, bottom formwork and end formwork.

[0005] The objective of this invention can also be achieved in one step through the following technical measures.

[0006] Furthermore, the adjustable height sandbox includes a top cover, a lower box body, and two baffles. The lower box body is a welded steel plate box body with an open top surface. The horizontal projection of the lower box body is square. A pair of sides of the lower box body have recessed rectangular sand-filling notches. The baffles fixed to the pair of sides at both ends block the rectangular sand-filling notches. The lower box body is filled with dried sand, and the top surface of the sand is flush with the upper side of the lower box body. The top cover presses on the top surface of the sand, and the perimeter of the top cover is sealed with the adjacent side of the upper side of the lower box body using sealant. The lower side of the bottom beam abuts against the top surface of the top cover.

[0007] Furthermore, the single-sided gap A between the periphery of the top cover and the corresponding inner side of the rectangular sand-release notch of the lower box body is 4 to 6 mm; the difference between the width D1 of the rectangular sand-release notch and the width D2 of the steel bottom beam made of H700 type is D1 - D2 = 5 to 7 mm, and the depth H1 of the rectangular sand-release notch is 50 mm.

[0008] Furthermore, the concrete beam slab is 7m long and 50mm thick.

[0009] Furthermore, the adjustment stroke of the spiral jack is 550-650 mm.

[0010] Furthermore, the breaking force of the high-strength braided tape is greater than 15kN.

[0011] Furthermore, along the length of the main truss, the vertical support brackets of the middle pier assembly are respectively provided on both sides of the vertical support brackets of the middle pier assembly, which are made of 300×300H steel; and the vertical support brackets of the side pier assembly are respectively provided in the direction of the vertical support brackets of the side pier assembly facing the end of the main truss, which are respectively made of 300×300H steel.

[0012] This invention incorporates sandboxes at the bottom of both the vertical supports for the side pier assembly and the welded vertical supports for the side pier assembly. Simultaneously removing the dry sand from each sandbox lowers both supports by 5-7 cm, allowing for the separation of the high-altitude formwork and lower distribution beams from the main truss. This replaces the high-risk and difficult-to-operate method of adjusting the height of the jacks at the top of the vertical supports with a safer and more convenient method of removing sand from the ground-based sandboxes, significantly improving the efficiency of dismantling the vertical supports and main truss, reducing construction costs, and minimizing the time spent on public transportation. The dismantling process also eliminates safety hazards to overhead high-voltage lines at both ends of the main truss and to traffic after the truss is opened. Furthermore, this construction method is advantageous during the rainy season and on soft foundations.

[0013] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0014] Figure 1 This is a front view of the large-span portal cast-in-place cap beam truss and its vertical supports; Figure 2 for Figure 1 A magnified partial view in direction A; Figure 3 This is a schematic diagram showing that the two ends of the upper distribution beam in step B1) are fixedly connected to the two ends of the lower distribution beam by steel tie rods respectively; Figure 4 This is a schematic diagram showing the connection between the lower distribution beam and the cast-in-place cap beam in step B1) via high-strength braided straps. Figure 5 yes Figure 1 Enlarged view of Part I; Figure 6 This is a side view of the sandbox; Figure 7 yes Figure 6 Top view after the bottom beam has been removed. Detailed Implementation

[0015] The invention will be further explained below with reference to the accompanying drawings and an embodiment of a method for the rapid erection and dismantling of a cast-in-place cap beam truss and vertical supports for a municipal bridge spanning a main urban traffic artery.

[0016] like Figures 1-5 As shown, this embodiment illustrates a rapid erection and dismantling method for a large-span portal-type cast-in-place cap beam truss. The large-span portal-type cast-in-place cap beam truss consists of two parallel main trusses 1. Each main truss 1 includes a half-truss 11 fixedly connected by a butt joint. The half-truss 11 includes two sub-trusses 111 fixedly connected end-to-end. The main trusses 1 are supported by upper support beams 2 made of 400×400 H-beams and multiple spiral jacks 8 on the top of the central pier assembly vertical support 3, the top of the two side pier assembly vertical supports 4, and the top of the side pier welded vertical supports 5 located on both sides of the side pier 20, respectively. The single-section central pier assembly vertical support 3 and side pier assembly vertical support 4 are assembled into a cuboid frame by rectangular frame plates 31 welded from 300×300 H-beams using multiple sets of high-strength bolt and nut sets 32. On both sides of the side pier 20, cuboid frame structures of side pier welded vertical supports 5 are also provided.

[0017] The rapid erection and dismantling method includes: A) erecting 7 vertical supports and two main trusses 1, B) dismantling the two main trusses 1 and the 7 vertical supports; A1) The support foundations for the vertical support 1 of the middle pier assembly, the vertical support 4 of the side pier assembly, and the vertical support 5 of the side pier welding assembly are processed. The support foundations include the original asphalt pavement and the excavated pier construction area. Dry soil containing 5% cement is filled in the pier excavation area and compacted using a vibratory roller.

[0018] A2) Install the bottom supports for the central pier assembly vertical support 1, the side pier assembly vertical support 4, and the side pier welded vertical support 5. On the upper side of the bottom support foundation, install several parallel concrete beams 6, each 7m long and 50mm thick, arranged along the road direction. The positions of the concrete beams 6 match the bottom positions of the central pier assembly vertical support 3, the side pier assembly vertical support 4, and the side pier welded vertical support 5. 700×700 H-shaped steel bottom beams 7, perpendicular to the road direction and arranged side-by-side, are located below the bottom of the side pier assembly vertical support 4 and the side pier welded vertical support 5, corresponding to the positions of the bottom plates 41 of the side pier assembly vertical support 4 and the side pier welded vertical support 5. Multiple adjustable-height sandboxes 9 are respectively installed between the bottom beams 7 and the concrete beams 6.

[0019] (A3) Assemble the vertical support 3 for the central pier 10 and the vertical support 4 for the side piers 20, which are respectively enclosed on the outer perimeter of the central pier 10. Use a truck crane to lift each rectangular frame plate 31 to the outer perimeter of the central pier 10 and the side pier 20, respectively. Then, fix each rectangular frame plate 31 from bottom to top with multiple sets of high-strength bolts and nuts 32 to form the vertical support 3 for the central pier 10 and the vertical support 4 for the side piers 10. The base plate 41 of the vertical support 3 and the base plate 41 of the vertical support 4 are respectively supported on the corresponding bottom beams 7. Then, use a truck crane to lift the vertical support 5 for the side piers to the two sides of the corresponding side piers 20, and support the base plate 41 of the vertical support 5 for the side piers 20 on the corresponding bottom beams 7.

[0020] A4) Anchor screw jacks 8 with an adjustment stroke of 600mm to the top plates 42 of the vertical support 3 assembled on the middle pier, the vertical support 4 assembled on the side pier, and the vertical support 5 welded on the side pier. The top of the screw jacks 8 respectively supports the upper support beam 2 made of 400×400H steel parallel to the longitudinal direction of the road.

[0021] A5) Install the cast-in-place cap beam truss. First, assemble four half-truss sections 11 on the ground. Each half-truss section 11 is formed by splicing and fixing two sub-truss sections 111 end to end. Then, use a crawler crane to hoist two half-truss sections 11 in sequence. The lower sides of the two parallel half-truss sections 11 are welded and anchored to the top surface of the corresponding upper support beam 2. Then proceed as follows... Figure 2As shown, multiple diagonal bracing channel steels 21 are used to temporarily fix the two ends of the upper support beam 2 and the upper longitudinal beam 112 of the corresponding half-width truss 11 in sequence. Then, the other two half-width truss sections 11 are hoisted and welded to the corresponding upper support beam 2 in the same way. Similarly, multiple diagonal bracing channel steels 21 are used to temporarily fix the upper longitudinal beam 112 of the other two half-width truss sections 11 to the upper support beam 2, thereby improving the support stability of the main truss 1. The upper and lower sides of the joint end faces of the two parallel half-width truss sections 11 are fixed to two parallel main truss sections 1 by arrays of high-strength bolt and nut groups 32. The bottoms of several portal beams 12, which are welded from 250×250 H-shaped steels and arranged at intervals and perpendicular to the main truss sections 1, are welded and fixed to the upper longitudinal beams 112 of the two main truss sections 1, thereby improving the stability of the cast-in-place cap beam truss.

[0022] A6) Install the lower distribution beam 22 and the bottom formwork 40. On the ground, arrange multiple double-section 25# I-beams horizontally in parallel as the lower distribution beam 22. Then, hoist the bottom formwork pieces 401 onto the multiple lower distribution beams 22. (Example:) Figure 1 and Figure 3 As shown, the bottom formwork 401 and multiple lower distribution beams 22 are intermittently welded together to form a whole. Then, the bottom formwork 401, along with the multiple lower distribution beams 22, are hoisted onto the lower longitudinal beams 113 of the two main trusses 1. The ends of the multiple lower distribution beams 22 are intermittently welded and anchored to the bottom longitudinal beams 113 of the main trusses. The four bottom formwork pieces 401, connected end-to-end, are then fixed together to form a bottom formwork 40. Next, multiple stepped side forms 50, fixed end-to-end, are installed, and the two ends of the fixed side forms 50 are closed by end forms 60. Then, the reinforcement binding and installation before the cap beam is poured, as well as the installation of embedded pipes, are carried out sequentially. Finally, concrete is poured, and the prestressing of the steel strands and the grouting of the prestressed pipes are performed in stages, completing all construction operations for the cast-in-place cap beam.

[0023] B. Dismantle the two main truss sections 1 and each vertical support separately, including the following steps: B1) The bottom formwork 40 is fixedly connected to the cast-in-place cap beam 100 as one unit. When the prestressing tensioning is completed and the curing period of the cast-in-place cap beam 100 is over, if... Figure 3 As shown, multiple parallel upper distribution beams 23 are horizontally placed on the top surface of the cast-in-place cap beam 100. The upper distribution beams 23 are constructed by welding double-layered 20# channel steel, with the distance between two upper distribution beams 23 matching the distance between the two ends of the bottom formwork plate 401. Before dismantling the main truss 1, the welded anchorages between each lower distribution beam 22 and the lower longitudinal beam 113 of the main truss 1 are removed. Then, the two ends of the upper distribution beams 23 are fixed to the two ends of the lower distribution beams 22 below the bottom formwork plate 401 via steel tie rods 231 and steel nuts 232, and the steel nuts 232 are tightened. Figure 4As shown, the remaining lower distribution beams 22 are fixedly connected to the cast-in-place cap beam 100 by high-strength braided straps 24 with a breaking force greater than 15kN. That is, both ends of the high-strength braided straps 24 are fixedly connected to the two ends of the corresponding lower distribution beams 22. The middle of the high-strength braided straps 24 in the taut state is pressed against the top surface of the cast-in-place cap beam 100, so that the bottom formwork 40 and the lower distribution beams 22 are fixedly connected to the cast-in-place cap beam 100 as a whole. This avoids the bottom formwork 40 and the lower distribution beams 22 from falling and pressing against the lower longitudinal beams 113 of the two main trusses 1 when the vertical support is lowered as a whole, which would make it difficult to disassemble the main trusses 1.

[0024] (B2) Lower each vertical support, remove the baffles 93 on both sides of each sandbox 9, and simultaneously remove the sand from each sandbox 9. The top cover 91 of each sandbox is lowered simultaneously. The bottom beam 7 and the vertical support 3 assembled on the middle pier, the vertical support 4 assembled on the side pier, and the vertical support 5 welded on the side pier are all lowered by 7cm simultaneously. The two main trusses 1 are also lowered by 5-7cm. This allows the lower distribution beam 22 to detach from the lower longitudinal beams 113 of the two main trusses 1 at both ends, thus facilitating the disassembly of the two main trusses 1.

[0025] B3) such as Figure 5 As shown, hand-operated hoists 70 are suspended at the reserved steel bars 101 on the central pier. The other end of the hand-operated hoists 70 is hooked to the upper longitudinal beams 112 of the main truss 1 via steel wire ropes 701, temporarily suspending the two main truss sections 1 to prevent slippage due to the center of gravity of the main truss 1 deviating from the lifting point during lifting, which could endanger the overhead high-voltage lines at both ends of the main truss 1. Then, several portal beams 12 on the upper side of the two main truss sections 1 are removed, and then multiple sets of high-strength bolt and nut groups 32 connecting the two half-section trusses 11 are removed.

[0026] (B4) Complete the dismantling of the main truss 1 and each vertical support in sequence, close the single lane, and use two truck cranes to lift two half-span truss sections 11 in sequence. Then, first remove all the screw jacks 8, and then dismantle the multiple sets of high-strength bolt and nut groups 32 of the central pier assembly vertical support 3 and the side pier assembly vertical support 4 from top to bottom. Next, lift off each rectangular frame plate 31 in sequence. Then, lift off the four side pier welded vertical supports 5 in sequence, then lift off the bottom beam 7, and remove all sandboxes 9, completing the dismantling of the main truss 1 and each vertical support. Immediately proceed with the dismantling of the side formwork 50, bottom formwork 40, and end formwork 60.

[0027] like Figure 6 and Figure 7As shown, the height-adjustable sandbox 9 includes a top cover 91, a lower box body 92, and two baffles 93. The lower box body 92 is a welded steel plate box with an open top. The horizontal projection of the lower box body 92 is square. A pair of sides 921 of the lower box body 92 have recessed rectangular sand-filling notches 922. The two ends are fixed to the sides 921 by fastening screws 94, which cover the rectangular sand-filling notches 922. The lower box body 92 is filled with dried sand, and the top surface of the sand is flush with the upper side of the lower box body 92. The top cover 91 presses on the top surface of the sand, and the perimeter of the top cover 91 is sealed with sealant between the adjacent upper side of the lower box body 92 to prevent the sand from getting damp. The lower side of the bottom beam 7 abuts against the top surface of the top cover 91.

[0028] The single-sided gap A between the perimeter of the top cover 91 and the corresponding inner side of the top opening of the lower box 91 is 5mm. The difference between the width D1 of the rectangular sand release notch of the top cover 91 and the width D2 of the bottom beam is D1-D2=6mm. This structure allows the top cover 91 to descend as the sand inside the lower box 91 is continuously excavated. The bottom beam 7 can descend with the top cover 91 until the bottom surface of the bottom beam 7 abuts against the bottom edge of the rectangular sand release notch 922 with a depth H1=50mm. At this time, the side pier assembled vertical support 4, the side pier assembled vertical support 5, and the two main trusses 1 descend synchronously by the depth of the rectangular sand release notch 922 (50mm + the thickness of the top plate 91, 20mm) = 70mm. This allows the two ends of the lower distribution beam 22 to detach from the lower longitudinal beams 113 of the two main trusses 1, and the two main trusses 1 can be disassembled.

[0029] like Figure 1 As shown, along the length of the main truss 1, the vertical support brackets 3 of the middle pier assembly are respectively provided on both sides of the vertical support bracket 3 of the middle pier assembly, which are made of 300×300H steel. The vertical support brackets 5 of the side pier assembly are respectively provided in the direction of the end of the main truss, which are made of 300×300H steel. This significantly improves the support stability of the main truss 1.

[0030] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution and equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for quickly erecting and dismantling a large-span portal cast-in-situ cap beam truss, the large-span portal cast-in-situ cap beam truss being two parallel arranged main trusses, each main truss comprising two half trusses fixed by butt joint end faces, each half truss comprising two end-to-end fixed sub-trusses, the lower side of the main truss being supported by an upper support beam made of 400*400 H-shaped steel and a plurality of screw jacks on the top end of a middle pier assembly vertical support, a plurality of edge pier assembly vertical supports and edge pier welding vertical supports, respectively; the middle pier assembly vertical support and the edge pier assembly vertical support are respectively welded into a rectangular frame plate by 300*300 H-shaped steel, and are assembled into a cuboid frame by a plurality of high-strength bolt and nut groups, and a 300*300 H-shaped steel welded cuboid frame structure edge pier welding vertical support is further arranged on both sides of the edge pier; characterized in that The method for quickly erecting and dismantling comprises the steps of A erecting a plurality of vertical supports and installing two main trusses, and B dismantling the two main trusses and the plurality of vertical supports; The step A of erecting a plurality of vertical supports and installing two main trusses comprises the following steps: A1) processing the support bases of the middle pier assembly vertical support, the edge pier assembly vertical support and the edge pier welding vertical support, the support bases comprising original asphalt pavement and excavated pile cap construction area, dry soil containing 5% cement by weight is filled in the excavated pile cap area and is compacted by a vibrating road roller; A2) installing the bottom support of the middle pier assembly vertical support, the edge pier assembly vertical support and the edge pier welding vertical support, a plurality of parallel arranged concrete beam plates are installed on the bottom support base on the side of the road, respectively, the positions of the concrete beam plates are matched with the positions of the bottom of the middle pier assembly vertical support, the bottom of the edge pier assembly vertical support and the bottom of the edge pier welding vertical support, respectively; a bottom beam made of 700*700 H-shaped steel is arranged on the lower side of the bottom of the middle pier assembly vertical support, the bottom of the edge pier assembly vertical support and the bottom of the edge pier welding vertical support, respectively, and corresponds to the positions of the bottom plate of the middle pier assembly vertical support, the bottom plate of the edge pier assembly vertical support and the bottom plate of the edge pier welding vertical support, respectively, and a plurality of height-adjustable sandboxes are arranged between the bottom beam and the concrete beam plate; A3) assembling the middle pier assembly vertical support enclosed on the outer circumferential surface of the middle pier and the edge pier assembly vertical support enclosed on the outer circumferential surface of the edge pier, respectively, using a car crane to hoist each rectangular frame plate to the outer circumferential surface of the middle pier and the outer circumferential surface of the edge pier, respectively, and then sequentially fixing each rectangular frame plate by a plurality of high-strength bolt and nut groups from bottom to top to form the middle pier assembly vertical support enclosed on the outer circumferential surface of the middle pier and the edge pier assembly vertical support enclosed on the outer circumferential surface of the edge pier, respectively, the bottom plate of the middle pier assembly vertical support and the bottom plate of the edge pier assembly vertical support are supported on the corresponding bottom beam, respectively; then the edge pier welding vertical support is hoisted by the car crane to the two sides of the corresponding edge pier, respectively, and the bottom plate of the edge pier welding vertical support is supported on the corresponding bottom beam, respectively. A4) Anchoring a screw jack on each top plate of the middle pier assembly vertical support, the side pier assembly vertical support and the side pier assembly welded vertical support, respectively, and supporting an upper support beam made of 400x400 H-shaped steel parallel to the longitudinal direction of the road at the top of the screw jack; A5) Installing the cast-in-place bent cap truss, first completing the assembly of four half-width trusses on the ground, each half-width truss being formed by splicing and connecting two truss segments end to end, then sequentially hoisting two half-width trusses by a crawler crane, and welding and anchoring the lower sides of the two parallel half-width trusses to the top surfaces of the corresponding upper support beams; then temporarily connecting the upper longitudinal beams of the half-width trusses at both ends of the upper support beams with multiple diagonal bracing channel steels, and sequentially hoisting and welding the other two half-width trusses to the corresponding upper support beams in the same way, and temporarily connecting the upper longitudinal beams of the other two half-width trusses to the upper support beams with multiple diagonal bracing channel steels to improve the stability of the main truss; the abutting end faces of the two parallel half-width trusses are connected by a plurality of high-strength bolt and nut sets to form two parallel main trusses, and a plurality of 250x250 H-shaped steel door-shaped beams arranged at intervals and perpendicular to the main trusses are welded and fixed to the upper longitudinal beams of the two main trusses to improve the stability of the cast-in-place bent cap truss; A6) Installing the lower distribution beam and the bottom form, arranging a plurality of double-spliced 25# I-beams horizontally on the ground, then hoisting the bottom form pieces onto the plurality of lower distribution beams, welding and connecting the bottom form pieces and the plurality of lower distribution beams to form a whole, then hoisting the bottom form pieces and the plurality of lower distribution beams onto the lower longitudinal beams of the two main trusses, and anchoring the ends of the plurality of lower distribution beams to the bottom longitudinal beams of the main trusses, and connecting the plurality of bottom form pieces end to end to form a whole; then installing a plurality of step-shaped side forms end to end, and closing the ends of the connected side forms with end forms; then sequentially performing steel bar binding and installation before pouring the bent cap, and installing the pre-buried pipe, then sequentially performing concrete pouring, prestressed steel wire tensioning and prestressed pipe grouting, and completing all construction operations of the cast-in-place bent cap; B. Disassembling the two main trusses and the vertical supports, respectively, including the following steps: B1) The bottom die is integrally connected with the cast-in-place cover beam. When the prestressed tensioning is completed and the curing period of the cast-in-place cover beam is over, a plurality of upper distribution beams arranged in parallel are horizontally arranged on the top surface of the cast-in-place cover beam. The upper distribution beams are made of double-spliced 20# channel steel. The distance between two upper distribution beams is matched with the distance between the two ends of the bottom die plate. Before the main truss is removed, the welded anchoring of each lower distribution beam and the lower longitudinal beam of the main truss is removed. Then, the two ends of the upper distribution beam are fixed to the two ends of the lower distribution beam under the two ends of the bottom die plate through steel bar pull rods and steel nuts, and the steel nuts are tightened. The remaining lower distribution beams are fixed to the cast-in-place cover beam through high-strength woven belts, i.e. the two ends of the high-strength woven belts are fixed to the two ends of the corresponding lower distribution beams, and the middle part of the high-strength woven belt in the tensioned state is pressed on the top surface of the cast-in-place cover beam, so that the bottom die and the lower distribution beam are integrally connected with the cast-in-place cover beam. Thus, when the vertical support falls as a whole, the bottom die and the lower distribution beam are prevented from falling and closely contacting the lower longitudinal beams of the two main trusses, so that the main truss is difficult to be removed. B2) The vertical supports are lowered, the baffles on both sides of each sand box are removed, the sand in each sand box is taken out, the top cover of each sand box is lowered, the bottom beam and the middle pier assembly vertical support, the side pier assembly vertical support, and the side pier welded vertical support are lowered by 5-7 cm, and the two main trusses are also lowered by 5-7 cm. Thus, the two ends of the lower distribution beam are separated from the lower longitudinal beams of the two main trusses, so that the two main trusses are easily removed. B3) A hand-operated hoist is hung at the reserved steel bar of the middle pier, the other end of the hand-operated hoist is hooked to the upper longitudinal beam of the main truss through a steel wire rope, and the two main trusses are temporarily hung to prevent sliding due to the center of gravity of the main truss deviating from the lifting point, which may endanger the overhead high-voltage line outside the two ends of the main truss. Then, a plurality of door-shaped beams on the upper side of the two main trusses are removed, and a plurality of high-strength bolt and nut groups connecting the two half-span trusses are removed. B4) The removal of the main truss and the vertical supports is sequentially completed, the single-lane road is closed, two truck cranes are used to sequentially lift and transport the two half-span trusses, then the multiple high-strength bolt and nut groups of the middle pier assembly vertical support and the side pier assembly vertical support are sequentially removed from top to bottom after the removal of the screw jacks, then the rectangular frame plates are sequentially lifted away, then the four side pier welded vertical supports are sequentially lifted away, then the bottom beam is lifted away, and all the sand boxes are removed, so that the removal of the main truss and the vertical supports is completed. Then, the side die, the bottom die, and the end die are removed.

2. The method of claim 1, wherein the method further comprises: The height-adjustable sand box comprises a top cover, a lower box body, and two baffles. The lower box body is a steel plate welded box body with an open top surface. The horizontal projection of the lower box body is a square. A pair of side edges of the lower box body is provided with a lower rectangular sand placing gap. The baffles fixed to the pair of side edges block the rectangular sand placing gap. The lower box body is filled with roasted sand. The top surface of the sand is flush with the upper side of the lower box body. The top cover is pressed on the top surface of the sand. The periphery of the top cover and the adjacent edges of the upper side of the lower box body are sealed by sealing glue. The bottom beam is abutted against the top surface of the top cover.

3. The method of claim 2, wherein the method further comprises: The single-side gap A between the top cover periphery and the corresponding inner side of the lower box body top opening is 4-6 mm; the difference between the rectangular sand placing notch width D1 and the H700 steel bottom beam width D2 is D1-D2=5-7 mm, and the rectangular sand placing notch depth H1 is 50 mm.

4. The method for rapid erection and dismantling of long-span portal cast-in-situ deck beam truss according to claim 1, characterized in that, The length of the concrete beam plate is 7 m, and the thickness is 50 mm.

5. The method for rapid erection and dismantling of long-span portal cast-in-situ deck beam truss as claimed in claim 1, wherein, The adjusting stroke of the screw jack is 550-650 mm.

6. The method for rapid erection and dismantling of long span portal cast-in-situ deck beam truss as claimed in claim 1, wherein, The breaking force of the high-strength woven belt is greater than 15 kN.

7. The method for rapid erection and dismantling of long-span portal cast-in-situ deck beam truss according to claim 1, characterized in that, Along the length direction of the main truss, the middle pier assembly vertical support bracket brackets are respectively provided with 300*300 H-shaped steel welded middle pier assembly vertical support bracket support brackets, and the edge pier group welding vertical support bracket brackets are respectively provided with 300*300 H-shaped steel welded edge pier group welding vertical support bracket support brackets.

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