CN114045752A

CN114045752A - Floating crane aerial positioning cantilever assembling method for large-section steel truss box girder

Info

Publication number: CN114045752A
Application number: CN202111345430.3A
Authority: CN
Inventors: 黄斌; 安博; 储静山; 闫强; 吴兆营
Original assignee: China Construction Civil Engineering Co Ltd
Current assignee: China Construction Civil Engineering Co Ltd
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-02-15
Anticipated expiration: 2041-11-15
Also published as: CN114045752B

Abstract

The invention discloses a floating crane aerial positioning cantilever assembling method of a large-section steel truss box girder, which comprises the following steps: 1. temporary buttresses (1) are arranged on two sides of the bridge, temporary supports (2) are arranged on the temporary buttresses, and splicing platforms and beam falling jacks (8) are arranged on the temporary supports; 2. the splicing platform is provided with steel box girder sliding equipment; 3. the steel box girders and the rod pieces are transported to a construction site, and the steel box girders comprise side span steel box girders (71) and middle span steel box girders (72); 4. the side span steel box girders are symmetrically arranged section by section from two end parts of the bridge to the middle part, and rod pieces are arranged on the side span steel box girders to form the side span steel truss box girders; 5. a plurality of sections of mid-span steel box girders are installed between the two bank side-span steel truss box girders section by section from the edge part to the middle part and are closed in the middle of the bridge; a rod piece is arranged on the midspan steel box girder to form a middle overhanging steel truss box girder; 6. and (3) installing a support and removing all temporary buttresses and temporary supports.

Description

Floating crane aerial positioning cantilever assembling method for large-section steel truss box girder

Technical Field

The invention relates to a construction method for assembling a bridge, in particular to a floating crane aerial positioning cantilever assembling method for a large-section steel truss box girder.

Background

The assembled steel bridge is generally suitable for emergency emergencies, so the assembled bridge is required to have the characteristics of light structure, strong maneuverability, convenient transportation, quick assembly, strong adaptability and the like, and can be widely applied to the aspects of rush repair in wartime, restoration of traffic in flood control and disaster relief at ordinary times, quick construction of highway bridges and temporary highway temporary bridges, auxiliary highway construction and the like. In the existing construction process, when the large-section cantilever of the steel structure bridge is positioned at high altitude, the large-section cantilever is influenced by construction operation on water, and the construction requirement of high-altitude accurate splicing is difficult to achieve, so that the installation efficiency and the installation quality of the cantilever are difficult to guarantee. Meanwhile, a large-section cantilever dragging and sliding traction device which is not configured in the existing construction process causes difficulty in guaranteeing the bolting accuracy among cantilever sections.

Disclosure of Invention

The invention aims to provide a floating crane aerial positioning cantilever assembling method for a large-section steel truss box girder, which can improve the high-altitude assembling efficiency and precision of the steel truss box girder.

The invention is realized by the following steps:

a floating crane aerial positioning cantilever assembling method for a large-section steel truss box girder comprises the following steps:

step 1: the method comprises the following steps that a plurality of installation nodes are respectively arranged on two banks of a bridge, a temporary buttress is arranged between each installation node and the ground, a temporary support is arranged on each temporary buttress along the length direction of the bridge, and an assembling platform and a beam falling jack are arranged on each temporary support;

step 2: arranging steel box girder sliding equipment on the splicing platform along the length direction of the bridge;

and step 3: transporting the steel box girder and the rod piece to a construction site, wherein the steel box girder comprises a plurality of sections of side span steel box girders and a plurality of sections of mid span steel box girders;

and 4, step 4: hoisting the side span steel box girders to the assembly platform through a floating crane, symmetrically installing a plurality of sections of the side span steel box girders section by section from the end parts of two banks of the bridge to the middle part, and installing rod pieces on the side span steel box girders to form the side span steel truss box girders;

and 5: hoisting midspan steel box girders onto the assembly platform through a floating crane and a truck crane, installing a plurality of midspan steel box girders between the side span steel truss box girders on the two banks section by section from the edge part to the middle part, and closing the middle part of the bridge; installing a rod piece on the midspan steel box girder to form a middle overhanging steel truss box girder;

step 6: and adjusting the line type of the side span steel truss box girder and the middle cantilever steel truss box girder, installing a support, dismantling all temporary buttresses and temporary supports, and continuing the construction of the residual work of the bridge deck.

In the step 2, the steel box girder sliding equipment comprises a dragging track girder and a dragging trolley, a pair of dragging track girders are arranged on the temporary support, dragging tracks with limit stops at two ends are respectively arranged on the pair of dragging track girders, the dragging trolley is arranged on the dragging tracks and can slide along the dragging tracks, and the dragging track girders are provided with assembling stand columns.

In the step 3, the rod piece comprises a lower chord, a web member, an upper chord and a cantilever arm, and the steel box girder, the lower chord, the web member, the upper chord and the cantilever arm are spliced into a steel truss box girder structure.

In the step 4, the plurality of side span steel box girders sequentially comprise a first side span steel box girder, a second side span steel box girder, … and an nth side span steel box girder from the end part to the middle part of the bridge, wherein n is a natural number not less than 2 and is a double number; the hoisting method of the side span steel truss box girder comprises the following steps:

step 4.1: a lower chord is arranged at one end of the bridge and at one side of the first span steel box girder;

step 4.2: hoisting the first section of side span steel box girder and the lower chord on one side of the first section of side span steel box girder to a dragging trolley of the steel box girder sliding equipment through a floating crane;

step 4.3: hoisting a lower chord on the other side of the first section of the edge-span steel box girder to a dragging trolley of the steel box girder sliding equipment through a floating crane, and fixedly connecting the lower chord with the other side of the first section of the edge-span steel box girder;

step 4.4: repeating the step 4.1 to the step 4.3, and symmetrically installing a second joint side span steel box girder at the other end of the bridge;

step 4.5: respectively sliding the first side span steel box girder and the second side span steel box girder to installation positions along a dragging track of the steel box girder sliding equipment through a dragging trolley of the steel box girder sliding equipment, and supporting the first side span steel box girder and the second side span steel box girder through a supporting piece on the temporary buttress;

step 4.6: repeating the step 4.1 to the step 4.5, sliding the third section of the side span steel box girder and the fourth section of the side span steel box girder to the installation position, splicing the third section of the side span steel box girder with the first section of the side span steel box girder, and splicing the fourth section of the side span steel box girder with the second section of the side span steel box girder;

step 4.7: respectively installing web members on a lower chord of a first section of edge-spanning steel box girder, a lower chord of a second section of edge-spanning steel box girder, a lower chord of a third section of edge-spanning steel box girder and a lower chord of a fourth section of edge-spanning steel box girder through truck cranes, and installing upper chords on the web members;

step 4.8: repeating the step 4.1 to the step 4.7 until the assembly of the side span steel truss box girders on the two banks of the bridge is completed;

step 4.9: arranging a jack on a main pier of the bridge, completing beam falling of the side span steel truss box girder at one end of the bridge through the switching of the beam falling jack and the jack, arranging a steel buttress on a temporary buttress, and temporarily supporting the side span steel truss box girder after the beam falling;

step 4.10: repeating the step 4.9 to finish the girder falling of the side span steel truss box girder at the other end of the bridge, wherein the girder falling height of the side span steel truss box girder at the other end of the bridge is smaller than that of the side span steel truss box girder at one end of the bridge;

step 4.11: demolish steel box girder sliding equipment, assembly platform and temporary stand below the steel truss box girder of the side span of bridge one end from top to bottom, demolish the tractor of the steel box girder sliding equipment below the steel truss box girder of the side span of the other end of bridge.

And iron sand concrete is poured at the first and third sections of the side-span steel box girder, and iron sand concrete is poured at the second and fourth sections of the side-span steel box girder.

From the end part to the middle part of the bridge, the plurality of sections of the mid-span steel box girders sequentially comprise a first section of the mid-span steel box girder, a second section of the mid-span steel box girder, … and an mth section of the mid-span steel box girder, m is a natural number not less than 2, and m is singular; the hoisting method of the middle cantilever steel truss box girder comprises the following steps:

step 5.1: installing a lower chord on one side of a midspan steel box girder in a first section at one end of the bridge;

step 5.2: hoisting the first midspan steel box girder and the lower chord on one side of the first midspan steel box girder to an installation position through a floating crane, and splicing the first midspan steel box girder with the (n-1) th side span steel box girder;

step 5.3: hoisting a lower chord on the other side of the first midspan steel box girder by a floating crane;

step 5.4: repeating the step 5.1 to the step 5.3, and splicing a second-section mid-span steel box girder on the nth-section side-span steel box girder at the other end of the bridge;

step 5.5: installing an upper chord on a first midspan steel box girder through a truck crane, and installing a web member on the upper chord; installing an upper chord on the second midspan steel box girder, and installing a web member on the upper chord;

step 5.6: repeating the step 5.1 to the step 5.5 until the installation of the midspan steel box girder in the (m-1) th section, the upper chord member and the web members is completed;

step 5.7: adjusting beam falling jacks below the side span steel truss box girders at two banks of the bridge, and enabling the tail end of the (m-1) th midspan steel box girder and the tail end of the (m-2) th midspan steel box girder to be closed through the m-th midspan steel box girder in an unstressed state;

step 5.8: and hoisting the rest upper chord member, the web member and the cantilever by the truck crane, and splicing to complete the steel truss box girder structure.

And before the closure of the mid-span steel box girder in the m section, continuously monitoring the tail end elevation of the closure steel box girder and the corresponding atmospheric temperature for 24-48h, drawing a temperature-elevation change curve, performing temperature sensitivity analysis on the tail end of the steel box girder, and determining the closure temperature and the closure time.

And in the process of assembling the side span steel box girder and the mid span steel box girder, calculating the downwarping of the assembled steel box girder according to modeling, and if the steel box girder is downwarped, pre-lifting the assembled steel box girder, wherein the pre-lifting height is consistent with the downwarping height.

Compared with the prior art, the invention has the following beneficial effects:

the invention continuously monitors the elevation of the cantilever end of the closure gap and the corresponding atmospheric temperature for 24-48h before the main span closure, draws a temperature-elevation change curve, analyzes the temperature sensitivity of the cantilever section, analyzes the data, determines the optimal closure temperature and closure time, carries out side span falling to the designed position after the two side span steel truss box girders are dragged and slid to be installed, pours the permanent weight iron sand concrete at the side span, improves the anti-overturning safety coefficient of the main span cantilever installation, sets the structural pre-camber reversely according to the constant load +1/2 live load displacement according to the design requirement, determines the rod linear system according to the design vertical curve + pre-camber without additionally setting the pre-camber, reduces the difficulty when a worker erects the cantilever, reduces the possibility of rework, and sets the pre-camber value according to the cantilever section installation calculated by modeling, when the main span steel truss box girder cantilever is installed, pre-lifting is required according to the pre-camber value of each section, and real-time monitoring is carried out, so that the installation line shape of the bridge is ensured to meet the design requirement, and the safety when the cantilever is assembled is improved.

Drawings

FIG. 1 is a flow chart of the floating crane aerial positioning cantilever assembling method of a large-section steel truss box girder;

FIG. 2 is a construction schematic diagram of step 1 in the floating crane aerial positioning cantilever assembling method of the large-section steel truss box girder;

FIG. 3 is a side view of the installation of the lower chord in the floating crane aerial positioning cantilever assembly method of the large-section steel truss box girder of the present invention;

FIG. 4 is a schematic mounting diagram of an edge-span steel box girder in the floating crane aerial positioning cantilever assembly method of the large-section steel truss box girder;

FIG. 5 is a schematic diagram of the installation of the rod members of the side span steel box girder in the floating crane aerial positioning cantilever assembly method of the large-section steel truss box girder of the invention;

FIG. 6 is a construction schematic diagram of step 5 in the floating crane aerial positioning cantilever assembling method of the large-section steel truss box girder;

FIG. 7 is a construction schematic diagram of step 6 in the floating crane aerial positioning cantilever assembling method of the large-section steel truss box girder.

In the figure, 1 temporary buttress, 2 temporary support, 3 floating crane, 4 truck crane, 51 hauling trolley, 52 hauling track beam, 61 lower chord, 62 web member, 63 upper chord, 71 side span steel box beam, 72 middle span steel box beam and 8 beam-falling jacks.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

Referring to the attached figure 1, a floating crane aerial positioning cantilever assembling method for a large-section steel truss box girder comprises the following steps:

before assembly operation, construction preparation is required: and organizing materials to enter the field according to the arrangement of the construction progress in the construction process. And (3) compiling a detailed material plan, requiring the steel plates required by the bridge to be in place 5 days before the start of work, compiling a construction navigation safety guarantee scheme, and handling the above-water and underwater construction licenses to maritime departments and channel departments in time. Before construction, the ship and the floating crane 3 equipment are handled for checking and accepting, the transportation route of the steel member is investigated, and the steel member is guaranteed to be smoothly transported to the bridge site.

Referring to fig. 1 and fig. 6, step 1: set up a plurality of installation node respectively at the both sides of bridge to set up interim buttress 1 between every installation node and ground, along bridge length direction installation interim support 2 on interim buttress 1, set up on interim support 2 and assemble platform and roof beam jack 8 that falls.

The number of the temporary buttress 1 can be adjusted according to the length of the bridge, preferably, the end part to the middle part direction of the bridge can be sequentially provided with a 1# pier, a 2# pier, a 3# pier, a 4# pier, a 5# pier and a 6# pier which respectively correspond to a 1# main pier, a 2# main pier, a 3# main pier, a 4# main pier, a 5# main pier and a 6# main pier of the bridge. And (3) erecting a temporary support 2 and an assembling platform on the 3# pier to the 4# pier and the 5# pier to the 6# pier by using a 25t truck crane 4 for assembling and dragging the steel box girder.

Preferably, the temporary support 2, the splicing platform and the beam falling jack 8 can be erected at the 3# pier, the 4# pier, the 5# pier and the 6# pier by using a 25t truck crane 4.

The splicing platform can adopt a reverse hook form, is reversely hung on the lower part of the steel box girder, and simultaneously utilizes the stress of the help of the inspection track. The width of the assembly platform is about 0.8m, the height of the assembly platform is 1m, angle steel with the thickness of 75 multiplied by 75 mm is adopted as a vertical rod of a main structure, angle steel with the thickness of 50 multiplied by 5mm is adopted as a stepping rod, a pattern steel plate with the thickness of 4mm is laid on the assembly platform in the whole length, and a channel steel with the thickness of 12a is adopted as a main bearing rod; the assembly platform is manufactured in a segmented mode, and the construction platform can be lengthened and is convenient to construct when the cantilever arm is installed at the later stage.

Step 2: and a steel box girder sliding device is arranged on the splicing platform along the length direction of the bridge.

Referring to fig. 2, 4 and 5, the steel box girder sliding device comprises a dragging track girder 52 and a dragging trolley 51, wherein a pair of dragging track girders 52 are arranged on the temporary support 2, and the beam top elevation and the straightness deviation of the dragging track girders 52 are less than or equal to 3 mm. The two ends of each of the pair of dragging track beams 52 are provided with dragging tracks with limit stoppers, the tops of the support base stones of the dragging track beams 52 are leveled by grouting materials, the elevation control is 5-10mm lower than the designed elevation, then the center lines of the supports are discharged from the base stones, and the height difference of the four corners of the supports is not more than 1 mm. The tractor trolley 51 is arranged on the tractor track and can slide along the tractor track, and the sliding amplitude of the tractor trolley 51 is limited by a limit stop. The dragging track beam 52 is provided with assembling upright columns for assembling the steel box beam.

Preferably, the trailing track beam 52 is constructed using beret segments. Before the steel box girder is dragged, the settlement of each buttress is retested, and the distance between the dragging track girders 52 is rechecked to ensure that the dragging track is smooth.

Referring to fig. 3 to 7, step 3: and (3) transporting the steel box girders and the rod pieces to a construction site, wherein the steel box girders comprise a plurality of sections of side span steel box girders 71 and a plurality of sections of mid span steel box girders 72.

Referring to fig. 3, 5 to 7, preferably, the steel box girder may be transported to a construction site by water transportation, and the rod member may be transported to the construction site by land transportation; the member comprises a lower chord 61, a web member 62, an upper chord 63 and a cantilever arm, and the steel box girder, the lower chord 61, the web member 62, the upper chord 63 and the cantilever arm are spliced into a steel truss box girder structure. The splicing of the steel box girder, the lower chord 61, the web member 62, the upper chord 63 and the cantilever can be determined according to the design requirements of the steel truss box girder structure, the structural pre-camber is reversely set according to the constant load +1/2 live load displacement according to the design requirements and modeling calculation, and the rod linear system is determined according to the design vertical curve + pre-camber.

The steel box girder is designed and processed according to the drawing of the bridge, is slipped onto a cargo ship after being checked and accepted, and is transported to a construction site through the water transportation of the cargo ship of 800 t. The water transportation process comprises the following steps: berthing on a wharf → loading the steel box girder in a sliding manner → binding and fixing → navigating to a bridge construction site → positioning a ship → releasing binding → unloading the steel box girder → returning the ship.

And 4, step 4: the side span steel box girders 71 are hoisted to the splicing platform through the floating crane 3, a plurality of sections of the side span steel box girders 71 are symmetrically installed section by section from the end parts of two banks of the bridge to the middle part, and a rod piece is installed on the side span steel box girders 71 to form the side span steel truss box girders.

Referring to fig. 3 to 5, in the direction from the end to the middle of the bridge, the plurality of side span steel box girders 71 sequentially include a first side span steel box girder, a second side span steel box girder, …, and an nth side span steel box girder, where n is a natural number greater than or equal to 2, and n is a double number. The hoisting method of the side span steel truss box girder comprises the following steps:

step 4.1: and a lower chord 61 is arranged at one end of the bridge at one side of the first side span steel box girder, and preferably, the first side span steel box girder and the lower chord 61 at one side thereof can be assembled into a whole in a factory and then transported to a construction site.

Step 4.2: the first side span steel box girder and the lower chord 61 at one side thereof are hoisted to the tractor trolley 51 of the steel box girder sliding equipment through the floating crane 3.

The weight of the first side span steel box girder (including the single-side lower chord 61) and the second side span steel box girder (including the single-side lower chord 61) is 178.08t, and 200t of the floating crane 3 can be adopted to hoist the side span steel box girder 71. At the moment, 200t of the floating crane 3 has the large arm length of 36m, the arm support base is 5m to the bow, the lifting hook is 13m to the bow, the rated lifting capacity is 200t and is larger than the single-point weight of 178.08t, and the hoisting requirements of the steel box girder and the floating crane 3 are met.

After the weight of the side span steel box girder 71 is totally placed on the tractor 51, the temporary support 2 is observed whether the structure is deformed or not and whether the connection welding seam is cracked or not, and the hook can be taken off after the condition that the temporary support 2 is in a good state is confirmed.

Step 4.3: and hoisting the lower chord 61 at the other side of the first joint of the side span steel box girder to the tractor 51 of the steel box girder sliding equipment through the floating crane 3, and fixedly connecting the lower chord 61 with the other side of the first joint of the side span steel box girder.

Preferably, two dragging trolleys 51 can be arranged on one dragging track on one side, and splicing columns are arranged on the dragging track on the other side, so that the lower chord 61 can be conveniently hoisted.

Step 4.4: and (4) repeating the step 4.1 to the step 4.3, and symmetrically installing a second joint side span steel box girder at the other end of the bridge.

Step 4.5: the first side span steel box girder and the second side span steel box girder slide to the installation position along the dragging track of the steel box girder sliding equipment through the dragging trolley 51 of the steel box girder sliding equipment respectively and are supported through the supporting piece on the temporary buttress 1.

Preferably, the side span steel box girder 71 can be dragged by using 4 dragging trolleys 51 with 100t three-dimensional girder-falling jacks 8, the front dragging trolley 51 and the rear dragging trolley 51 are rigidly connected, so that the braking of the dragging trolleys 51 is ensured to be stable, obstacles on a dragging track are cleared, and the dragging track is ensured to have no steps, craters and the like. After the side span steel box girder 71 reaches the installation position, the axial mileage is compounded, and the fine adjustment and the positioning are carried out by using 100t three-dimensional girder-falling jacks 8 on 4 tractor trolleys 51.

Step 4.6: and repeating the step 4.1 to the step 4.5, sliding the third section of the side span steel box girder and the fourth section of the side span steel box girder to the installation position, splicing the third section of the side span steel box girder with the first section of the side span steel box girder, and splicing the fourth section of the side span steel box girder with the second section of the side span steel box girder.

And the first section of edge-span steel box girder and the third section of edge-span steel box girder are poured with iron sand concrete, and the second section of edge-span steel box girder and the fourth section of edge-span steel box girder are poured with iron sand concrete for permanent counter weight and improving the anti-overturning safety coefficient of the steel truss box girder structure.

The weight of the third side span steel box girder (comprising the unilateral lower chord 61) and the fourth side span steel box girder (comprising the unilateral lower chord 61) is 148.29t, at the moment, the 200t floating crane has 3 large arm lengths of 36m, the arm support base is 5m to the bow, the lifting hook is 13m to the bow, the rated lifting capacity of 200t is larger than the single-point weight of 148.29t, and the hoisting requirements of the steel box girders and the floating crane 3 are met. The weight of the fifth side span steel box girder (comprising the single-side lower chord 61) and the sixth side span steel box girder (comprising the single-side lower chord 61) is 132.13t, at the moment, the length of a large arm of a 200t floating crane is 36m, the arm support base is 5m to the bow, the lifting hook is 13m to the bow, the rated lifting capacity is 200t and is more than the single-point weight 132.13t, and the hoisting requirements of the steel box girder and the floating crane 3 are met. The weight of the seventh side span steel box girder (comprising the single-side lower chord 61) and the eighth side span steel box girder (comprising the single-side lower chord 61) is 158.72t, at the moment, the length of a large arm of 200t of the floating crane is 36m, the base of the arm support is 5m to the bow, the lifting hook is 13m to the bow, the rated lifting capacity is 200t and is more than the single-point weight 158.72t, and the hoisting requirements of the steel box girder and the floating crane 3 are met. The weight of the ninth-section side span steel box girder (comprising the single-side lower chord 61) and the tenth-section side span steel box girder (comprising the single-side lower chord 61) is 176.98t, at the moment, the 200t floating crane has the length of 3 large arms of 36m, the arm support base is 5m to the bow, the lifting hook is 13m to the bow, the rated lifting capacity is 200t and is more than the single-point weight of 176.98t, and the hoisting requirements of the steel box girder and the floating crane 3 are met.

The butt joints between the lower chords 61 and the lower chords 61 of the third section of side-span steel box girder and the first section of side-span steel box girder, between the box girder and between the cantilever girder and the cantilever girder are not on the same straight line, so that the box girder and the cantilever girder are actually staggered. When the third section of the side-span steel box girder is dragged to the area between the lower chord 61 of the first section of the side-span steel box girder, the dragging is inching, the dragging speed is controlled, the axis deviation of the first section of the side-span steel box girder and the third section of the side-span steel box girder is rechecked at any time, and the adjustment is carried out in time. When the first section of the side-span steel box girder and the third section of the side-span steel box girder are assembled, the lower chord 61 of the first section of the side-span steel box girder and the lower chord 61 of the third section of the side-span steel box girder are connected firstly, when a splicing plate bolt hole is pre-installed in a web plate bolt hole of the lower chord 61 of the first section of the side-span steel box girder and a splicing plate bolt hole is pre-installed in a web plate of the lower chord 61 of the third section of the side-span steel box girder, a punch nail with the quantity of 20% is driven in, a splicing bolt with the quantity of 10% is penetrated in, and a wrench is used for screwing the bolt. The splicing method of the fourth and second side-span steel box girders is the same as that of the third and first side-span steel box girders, and is not described herein again.

Step 4.7: the web members 62 are respectively installed on the lower chord 61 of the first, second, third and fourth side span

steel box girders

61, 61 and the upper chord 63 is installed on the web members 62 by the truck crane 4.

Preferably, the top chord 63 and web members 62 are mounted using a 100t truck crane 4. Arranging a pre-assembly jig frame on the bridge deck, splicing the upper chord 63 and the web members 62 into a whole, and spraying primer; then temporarily bolting the splicing plates at the connecting parts of the web members 62 and the lower chord members 61 to joints of the web members 62, wherein the bolt bolts cannot be screwed down, so that the splicing plates have movable gaps; temporary construction walkways are arranged on the web members 62 and the upper chord members 63 and are erected by scaffold steel pipes and hooped on the rod members at intervals of 1.5-2 m; and (3) adjusting the standing position of the 100t truck crane 4 on the ground, integrally hoisting the assembled upper chord 63 and the corresponding web member 62, pulling the cable rope, adjusting the posture of the integral component in the air, and slowly falling for alignment. In the hoisting process, a command crane cooperates with workers to insert the lower end of the web member 62 into the lower chord connector, preferentially match 1 bolt hole at the far end, quickly drive in positioning punch nails, then finely adjust 4 large arms of the truck crane to match other bolt holes, drive in 20% of assembly punch nails, penetrate in 10% of assembly bolts and are screwed by a spanner, and sequentially adjust and match the butt joints of the web member 62 and the lower chord member 61 from the side span to the midspan direction. After each joint is matched, 20% of assembly punching nails are immediately driven into the joint, 10% of assembly bolts are penetrated into the joint and are screwed down by a spanner, and all the joints are driven with the punching nails and the bolts according to requirements; the worker climbs up the upper chord 63 to unhook it by climbing the ladder via the end web members 62. And finally, welding and high bolt construction are carried out on the third section of side-span steel box girder and the first section of side-span steel box girder, and the fourth section of side-span steel box girder and the second section of side-span steel box girder, so that the splicing operation is completed.

Step 4.8: and (5) repeating the steps 4.1-4.7 until the assembly of the side span steel truss box girders on the two banks of the bridge is completed.

Step 4.9: the main pier of the bridge is provided with a jack, the side span steel truss box girder at one end of the bridge is turned by the girder falling jack 8 and the jack to complete girder falling, the temporary buttress 1 is provided with a steel buttress to temporarily support the side span steel truss box girder after girder falling.

Preferably, 4 500t hydraulic jacks can be respectively arranged on the tops of the No. 3 main pier and the No. 6 main pier, and 2 hydraulic jacks are arranged on the support on each main pier, and 8 hydraulic jacks are arranged in total; 500t hydraulic jacks are respectively arranged on the tops of the No. 4 main pier and the No. 5 main pier, and 4 hydraulic jacks are arranged on the supports on each main pier, and 16 hydraulic jacks are arranged in total. Every two hydraulic jacks share one pump station. And jacking and hollowing the erected side span steel truss box girder by 50mm by using 8 500t girder-falling jacks 8 arranged on the tops of the 4# and 5# piers and 4 500t girder-falling jacks 8 arranged on the tops of the 3# and 6# piers, statically observing for 10 minutes, checking the deformation conditions of the welding line and the rod piece of the side span steel truss box girder, and supporting the side span steel truss box girder by using a steel cushion seat at a support seat after confirming that no abnormity exists.

Step 4.10: and repeating the step 4.9 to finish the beam falling of the side span steel truss box beam at the other end of the bridge, wherein the beam falling height of the side span steel truss box beam at the other end of the bridge is smaller than that of the side span steel truss box beam at one end of the bridge.

Preferably, the beam falling is realized by switching a hydraulic jack and a pad seat at the main pier, the beam falling height is 100-200mm each time, the total beam falling height at one end of the bridge is 1950mm, and the beam falling height at the other end of the bridge is about 200 mm;

step 4.11: demolish steel box girder equipment, the assembly platform and the temporary stand 2 that slide of steel box girder below the side span steel truss box girder of bridge one end from top to bottom, demolish the small tractor 51 of the steel box girder equipment that slides of steel box girder below the side span steel truss box girder of the bridge other end, avoid small tractor 51 to influence the roof beam that falls.

Please refer to fig. 6, step 5: hoisting midspan steel box girders 72 through a floating crane 3 and a truck crane 4, installing a plurality of sections of the midspan steel box girders 72 between the side-span steel truss box girders at two banks section by section from the edge part to the middle part, and closing the middle part of the bridge; and a rod piece is arranged on the midspan steel box girder 72 to form the middle overhanging steel truss box girder.

From the end part to the middle part of the bridge, the plurality of sections of the mid-span steel box girders 72 sequentially comprise a first section of the mid-span steel box girder, a second section of the mid-span steel box girder, … and an mth section of the mid-span steel box girder, wherein m is a natural number not less than 2, and m is singular. The hoisting method of the middle cantilever steel truss box girder comprises the following steps:

step 5.1: at one end of the bridge, a lower chord 61 is installed at one side of the first section of the mid-span steel box girder, and preferably, the first section of the mid-span steel box girder and the lower chord 61 at one side thereof can be transported to a construction site after being assembled into a whole in a factory.

Step 5.2: and hoisting the first-section mid-span steel box girder and the lower chord 61 on one side of the first-section mid-span steel box girder to an installation position through the floating crane 3, and splicing the first-section mid-span steel box girder and the (n-1) -th-section side-span steel box girder.

Preferably, 200t of floating crane 3 is adopted to hoist the first midspan steel box girder and the lower chord 61 on one side of the first midspan steel box girder, the floating crane 3 is commanded to adjust the position of the first midspan steel box girder to enable the first midspan steel box girder to be slowly close to the (n-1) th side span steel box girder, 1 bolt hole at the far end is preferentially matched, a positioning impact nail is rapidly driven in, then 3 large arms of the floating crane are adjusted to be matched with other bolt holes, 50% assembling impact nails are driven in, and a steel code plate with the thickness of more than 16mm is welded at the interval of 50cm at the joint of the top surface and the bottom surface of the first midspan steel box girder and the (n-1) th side span steel box girder. And then commanding the floating crane 3 to slowly drop the hook, observing whether the spliced steel box girder is deformed or not and whether the welding seam is cracked or not, and after confirming that the spliced steel box girder is in a good state, unhooking.

In order to ensure splicing construction, when the mid-span steel box girder 72 is in suspension splicing, 3 workers, 12 workers in total, 4 welders on the bridge floor, 4 welders on the bottom plate, 8 gas shielded welders and 8 electrician wrenches are arranged on the web plate of the lower chord 61 on each side.

The weight of the first section of midspan steel box girder (containing the unilateral lower chord 61) and the second section of midspan steel box girder (containing the unilateral lower chord 61) is 166.51t, at the moment, the 200t floating crane has 3 large arm lengths of 36m, the arm support base is 5m to the bow, the lifting hook is 13m to the bow, and the lifting height is: 12.034m (height of the top of the beam) -2.3m (annual water level) + 15.6m (height of the hanger and the occupied height of the steel wire rope) is 25.3 mm. When the distance between the main hook of the 200t floating crane 3 and the bow is 7.9m and the horizontal elevation angle is 70 degrees, the maximum hoisting capacity can reach 183t and be larger than 162.5t, the safety coefficient is 1.13, the hoisting height of the main hook is 43m and is larger than 25.3m, the weight of the main hook is larger than 166.51t, and the steel beam hoisting requirement is met.

At the moment, the self-weight down-warping of the assembled steel box girder is obtained through modeling calculation, when the first-section mid-span steel box girder and the second-section mid-span steel box girder are assembled, the assembled steel box girder needs to be pre-lifted by 8mm, namely the assembled steel box girder is lifted by 8mm compared with the design elevation.

Step 5.3: and hoisting the lower chord 61 at the other side of the first midspan steel box girder by the floating crane 3.

When the floating crane 3 hoists the lower chord 61 at the other side and the first midspan steel box girder, the remote end 1 bolt hole is preferentially matched, the positioning punch nail is quickly driven in, then the big arm is adjusted to match other bolt holes, 50% of assembly punch nails are driven in, and after the assembled steel box girder is confirmed to be in a good state, the hook can be taken off.

Step 5.4: and (5) repeating the step 5.1 to the step 5.3, and splicing the second-section mid-span steel box girder on the nth-section side-span steel box girder at the other end of the bridge.

Step 5.5: installing an upper chord 63 on the first midspan steel box girder through the truck crane 4, and installing a web member 62 on the upper chord 63; an upper chord 63 is mounted on the second mid-span steel box girder, and a web member 62 is mounted on the upper chord 63.

Preferably, a 95t truck crane 4 can be adopted, and during hoisting, 4 support legs of the truck crane are fully opened, and 3 × 0.3m road base plates are padded at the support legs to protect the steel box girder.

Step 5.6: and (5.1) repeating the step 5.1 to the step 5.5 until the installation of the mid-span steel box girder in the (m-1) th section and the upper chord 63 and the web members 62 thereof is completed.

The weight of the third section of the mid-span steel box girder (comprising the single-side lower chord 61) and the weight of the fourth section of the mid-span steel box girder (comprising the single-side lower chord 61) are 169.76t, at the moment, the length of a large arm of a 200t floating crane is 3 is 36m, the base of the arm support extends to the bow 5m, the lifting hook extends to the bow 13m, the rated lifting capacity is 200t and is greater than the single-point weight 169.76t, and the steel girder hoisting requirement is met. At the moment, the self-weight downwarping of the assembled steel box girder is obtained through modeling calculation, and when the third-section midspan steel box girder and the fourth-section midspan steel box girder are assembled, the assembled steel box girder needs to be pre-lifted by 12mm, namely the assembled steel box girder is lifted by 12mm compared with the design elevation.

The weight of the fifth midspan steel box girder (containing the single-side lower chord 61) and the weight of the sixth midspan steel box girder (containing the single-side lower chord 61) are both 134.69t, at the moment, the 200t floating crane has 3 large arms with the length of 36m, the arm support base reaches the bow 5m, the lifting hook reaches the bow 13m, the rated lifting capacity is 200t and is more than the single-point weight 134.69t, and the steel girder hoisting requirement is met. At the moment, the self-weight downwarping of the assembled steel box girder is obtained through modeling calculation, and when the fifth-section midspan steel box girder and the sixth-section midspan steel box girder are assembled, the assembled steel box girder needs to be pre-lifted by 12mm, namely the assembled steel box girder is lifted by 12mm compared with the design elevation.

The weight of the seventh midspan steel box girder (containing the single-side lower chord 61) and the weight of the eighth midspan steel box girder (containing the single-side lower chord 61) are both 122.03t, at the moment, the 200t floating crane has 3 large arms with the length of 36m, the arm support base reaches the bow 5m, the lifting hook reaches the bow 13m, the rated lifting capacity is 200t and is more than the single-point weight 122.03t, and the steel girder hoisting requirement is met. At the moment, the self weight of the assembled steel box girder is obtained by modeling calculation, the steel box girder is warped downwards by 19mm, and when the seventh midspan steel box girder and the eighth midspan steel box girder are assembled, the assembled steel box girder needs to be pre-lifted by 19mm, namely, the assembled steel box girder is lifted by 19mm compared with the design elevation.

Step 5.7: and adjusting beam falling jacks 8 below the side span steel truss box girders at two banks of the bridge to enable the tail end of the (m-1) th midspan steel box girder and the tail end of the (m-2) th midspan steel box girder to be closed through the m-th midspan steel box girder, so that the closure of the m-th midspan steel box girder in an unstressed state is realized.

And continuously monitoring the tail end elevation of the closure opening steel box girder and the corresponding atmospheric temperature for 24-48h before closure of the mid-span steel box girder in the mth section, drawing a temperature-elevation change curve, performing temperature sensitivity analysis on the tail section of the steel box girder, analyzing data, and determining the optimal closure temperature and closure time.

Step 5.8: and hoisting the rest upper chord 63, the web member 62 and the cantilever by the truck crane 4 to complete the steel truss box girder structure by splicing. Preferably, the cantilever arm can be installed after the steel box girder is closed in the mth section.

During the assembling process of the side span steel box girder 71 and the middle span steel box girder 72, the down-warping of the assembled steel box girder can be calculated according to modeling, if the steel box girder is down-warped, the assembled steel box girder is pre-lifted during assembling, and the pre-lifting height is consistent with the down-warping height.

Referring to fig. 7, step 6: the line type of steel truss case roof beam and the middle part steel truss case roof beam of encorbelmenting of adjustment side span, erection support are used for supporting the steel case of striding, demolish whole interim buttress 1 and temporary stand 2, including installing steel shotcrete on interim buttress 1, the roof beam jack 8 and the construction of assembling platform etc. that fall on temporary stand 2, continue the remaining work of bridge floor.

When the steel box girder is hoisted, the distances between the hoisting points 3 of the floating cranes of the full-bridge steel box girder are all 18m along the width direction of the bridge floor, the horizontal elevation angle of the hoisting steel wire rope is 60 degrees, and the occupied height of the hoisting tools and the steel wire rope is 18 multiplied by tan60 degrees/2 multiplied by 15.6 m.

The bridge is a three-span continuous steel truss bridge with the length of 42.5+80+42.5m, and the cross section of the bridge is arranged as follows: 3m (sidewalk) +3.5m (non-motor way) +2.5m (truss rod area) +10.75m (motor way) +0.5m (crash barrier) +10.75m (motor way) +2.5m (truss rod area) +3.5m (non-motor way) +3m (sidewalk) + 40+ m, two main girders are arranged in the transverse bridge direction, the center distance of the main girders is 24.5m, a roadway steel box girder is arranged between the two main girders, and a non-cantilever girder is arranged outside the main girders.

The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A floating crane aerial positioning cantilever assembling method of a large-section steel truss box girder is characterized by comprising the following steps: the method comprises the following steps:

step 1: the method comprises the following steps that a plurality of installation nodes are respectively arranged on two banks of a bridge, a temporary buttress (1) is arranged between each installation node and the ground, a temporary support (2) is arranged on each temporary buttress (1) along the length direction of the bridge, and an assembling platform and a beam falling jack (8) are arranged on each temporary support (2);

and step 3: transporting the steel box girders and the rod pieces to a construction site, wherein the steel box girders comprise a plurality of sections of side span steel box girders (71) and a plurality of sections of mid span steel box girders (72);

and 4, step 4: hoisting the side span steel box girders (71) to the assembly platform through the floating crane (3), symmetrically installing a plurality of sections of the side span steel box girders (71) from the end parts of two banks of the bridge to the middle part section by section, and installing rods on the side span steel box girders (71) to form the side span steel truss box girders;

and 5: hoisting midspan steel box girders (72) to the assembly platform through a floating crane (3) and a truck crane (4), installing the midspan steel box girders (72) between the side span steel truss box girders at two banks section by section from the edge part to the middle part, and closing the middle part of the bridge; a rod piece is arranged on the midspan steel box girder (72) to form a middle overhanging steel truss box girder;

step 6: adjusting the line type of the side span steel truss box girder and the middle overhanging steel truss box girder, installing a support, dismantling all the temporary buttresses (1) and the temporary supports (2), and continuing the construction of the rest work of the bridge deck.

2. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 1, which is characterized in that: in the step 2, the steel box girder sliding equipment comprises a dragging track girder (52) and a dragging trolley (51), a pair of dragging track girders (52) are arranged on the temporary support (2), dragging tracks with limit stops at two ends are respectively arranged on the pair of dragging track girders (52), the dragging trolley (51) is arranged on the dragging tracks and can slide along the dragging tracks, and assembling columns are arranged on the dragging track girders (52).

3. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 1, which is characterized in that: in the step 3, the rod piece comprises a lower chord (61), a web member (62), an upper chord (63) and a cantilever, and the steel box girder, the lower chord (61), the web member (62), the upper chord (63) and the cantilever are spliced into a steel truss box girder structure.

4. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 1, which is characterized in that: in the step 4, the plurality of sections of the side span steel box girders (71) sequentially comprise a first section of the side span steel box girder, a second section of the side span steel box girder, … and an nth section of the side span steel box girder from the end part to the middle part of the bridge, wherein n is a natural number not less than 2 and is a double number; the hoisting method of the side span steel truss box girder comprises the following steps:

step 4.1: a lower chord (61) is arranged at one end of the bridge and at one side of the first span steel box girder;

step 4.2: hoisting the first side span steel box girder and a lower chord (61) at one side of the first side span steel box girder to a dragging trolley (51) of the steel box girder sliding equipment through a floating crane (3);

step 4.3: hoisting a lower chord (61) at the other side of the first section of the side span steel box girder to a dragging trolley (51) of the steel box girder sliding equipment through a floating crane (3), and fixedly connecting the lower chord (61) with the other side of the first section of the side span steel box girder;

step 4.5: respectively sliding the first side span steel box girder and the second side span steel box girder to installation positions along a dragging track of the steel box girder sliding equipment through a dragging trolley (51) of the steel box girder sliding equipment, and supporting the first side span steel box girder and the second side span steel box girder through a supporting piece on a temporary buttress (1);

step 4.7: respectively installing a web member (62) on a lower chord member (61) of a first joint of edge-spanning steel box girder, a lower chord member (61) of a second joint of edge-spanning steel box girder, a lower chord member (61) of a third joint of edge-spanning steel box girder and a lower chord member (61) of a fourth joint of edge-spanning steel box girder through a truck crane (4), and installing an upper chord member (63) on the web member (62);

step 4.9: arranging a jack on a main pier of the bridge, completing beam falling of the side span steel truss box girder positioned at one end of the bridge through the switching of a beam falling jack (8) and the jack, arranging a steel buttress on a temporary buttress (1), and temporarily supporting the side span steel truss box girder after beam falling;

step 4.11: demolish steel box girder sliding equipment, assembly platform and temporary support (2) below the steel truss box girder of the side span of one end of bridge from top to bottom, demolish the tractor (51) of the steel box girder sliding equipment below the steel truss box girder of the side span of the other end of bridge.

5. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 4, which is characterized in that: and iron sand concrete is poured at the first and third sections of the side-span steel box girder, and iron sand concrete is poured at the second and fourth sections of the side-span steel box girder.

6. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 1, which is characterized in that: from the end part to the middle part of the bridge, the plurality of sections of the mid-span steel box girders (72) sequentially comprise a first section of the mid-span steel box girder, a second section of the mid-span steel box girder, … and an mth section of the mid-span steel box girder, m is a natural number not less than 2, and m is singular; the hoisting method of the middle cantilever steel truss box girder comprises the following steps:

step 5.1: a lower chord (61) is arranged at one end of the bridge and at one side of the midspan steel box girder in the first section;

step 5.2: hoisting the first midspan steel box girder and the lower chord (61) at one side of the first midspan steel box girder to an installation position through a floating crane (3), and splicing the first midspan steel box girder with the (n-1) th side span steel box girder;

step 5.3: hoisting a lower chord (61) at the other side of the midspan steel box girder in the first section by a floating crane (3);

step 5.5: installing an upper chord (63) on the first midspan steel box girder through a truck crane (4), and installing a web member (62) on the upper chord (63); installing an upper chord (63) on the second-section midspan steel box girder, and installing a web member (62) on the upper chord (63);

step 5.6: repeating the step 5.1 to the step 5.5 until the installation of the midspan steel box girder in the (m-1) th section, the upper chord (63) and the web members (62) is completed;

step 5.7: adjusting beam falling jacks (8) below the side span steel truss box girders at two banks of the bridge, and enabling the tail end of the (m-1) th midspan steel box girder and the tail end of the (m-2) th midspan steel box girder to be closed through the m-th midspan steel box girder in an unstressed state;

step 5.8: and hoisting the rest upper chord (63), the web member (62) and the cantilever by using the truck crane (4), and splicing to complete the steel truss box girder structure.

7. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 6, which is characterized in that: and before the closure of the mid-span steel box girder in the m section, continuously monitoring the tail end elevation of the closure steel box girder and the corresponding atmospheric temperature for 24-48h, drawing a temperature-elevation change curve, performing temperature sensitivity analysis on the tail end of the steel box girder, and determining the closure temperature and the closure time.

8. The assembly method of the floating crane aerial positioning cantilever of the large-section steel truss box girder as claimed in claim 1, which is characterized in that: and in the process of assembling the side span steel box girder (71) and the middle span steel box girder (72), calculating the downwarping of the assembled steel box girder according to modeling, and if the steel box girder is downwarped, pre-lifting the assembled steel box girder, wherein the pre-lifting height is consistent with the downwarping height.