Large-span steel arch bridge hoisting construction method under narrow working face

Abstract

The invention discloses a large-span steel arch bridge hoisting construction method under a narrow working face. The method comprises the steps that a bearing platform is poured, and a bridge abutment and a pier abutment are built on the bearing platform; arch foot sections are installed on the bridge abutment, and a temporary support is installed on the pier abutment or the bearing platform; the two side span arch rib sections are firstly hoisted through a crawler crane, and then the two main span arch rib sections are hoisted; the inclined struts are sequentially hoisted from the side span to the middle span through a crawler crane, and the inclined struts on the left side and the right side in the bridge direction are synchronously hoisted in place; the main beams are sequentially hoisted from the side span to the middle span through a crawler crane, and every two adjacent main beams are connected through a horse plate and I-shaped steel; paving a bridge floor, and coating a weld joint with paint; and dismantling the temporary bracket. According to the invention, the single crawler crane is adopted to hoist the arch ribs, the inclined struts and the main beam sections, so that the problem of narrow construction site is solved, especially the hoisting of steel arch bridges near farmlands and creeks.

Description

Technical Field

[0001] The invention relates to the technical field of steel arch bridge construction, and in particular to a hoisting construction method for a large-span steel arch bridge under a narrow working surface. Background Art

[0002] With the rapid development of modern tourism economy, there are more and more landscape bridges, especially steel arch bridges, which are increasingly widely used because of their lighter overall structure (compared with concrete structures), beautiful appearance, short construction period, and ability to solve many complex problems in the construction of large-span bridges.

[0003] However, large-span steel arch bridges have the characteristics of large beam span, heavy mass, high altitude, narrow construction site, and difficult assembly. In addition, the construction site is usually narrow and the truck crane cannot be fully unfolded for erection. Summary of the invention

[0004] In view of this, the present invention provides a method for hoisting and constructing a large-span steel arch bridge under a narrow working surface, so as to solve the problems existing in the above-mentioned background technology.

[0005] A method for hoisting and constructing a large-span steel arch bridge under a narrow working surface specifically comprises the following steps:

[0006] S1, pouring the cap and building abutments and piers on the cap;

[0007] S2, install the arch foot segment on the abutment and install temporary brackets on the pier or cap;

[0008] S3, using temporary brackets to install the arch rib segments: using crawler cranes to first hoist the arch rib segments on both side spans, and then hoist the arch rib segments on the two main spans;

[0009] S4: Use crawler crane to hoist diagonal braces from side span to middle span in sequence, and hoist diagonal braces on the left and right sides along the bridge direction into place simultaneously;

[0010] S5: Use crawler crane to hoist the main beams from the side span to the middle span in sequence, and use horse plates and I-beams to connect two adjacent main beams;

[0011] S6, laying the bridge deck and repainting the welds;

[0012] S7, remove the temporary support.

[0013] Preferably, the temporary support includes a support body, a construction platform horizontally arranged on the top of the support body, and a distribution beam vertically fixed to the top of the support body, and a tooth plate for adjusting the height of the support is provided on the distribution beam.

[0014] Preferably, the height of the construction platform of the temporary support should be 10-20 mm higher than the theoretical elevation of the bottom of the main beam.

[0015] Preferably, the temporary support installed on the pier is fixed to the pier via a pad at the bottom thereof;

[0016] The temporary bracket installed on the pedestal is fixed to the embedded parts in the pedestal through expansion bolts.

[0017] Preferably, in step S4, after the diagonal brace is installed, the diagonal brace and the arch rib segment are temporarily fixed, and after the bridge deck is installed, the weld between the diagonal brace and the arch rib is welded.

[0018] Preferably, the specific steps of hoisting the main beam in step S5 are:

[0019] Draw the main beam edge line and center line on the top of the temporary support, and verify whether the elevation of the temporary support construction platform and the support surface elevation of the pier meet the requirements of the specification;

[0020] Connect the hook of the crawler crane to the lifting lug on the main beam, and then slowly lift the main beam. When the main beam is lifted to the set height, slowly rotate the main arm of the crawler crane to the air above the bridge position, and then slowly drop the hook until the main beam stops 10cm away from the top surface of the temporary support;

[0021] Then, adjust the main beam position so that the bottom plate edge and center line are aligned with the main beam edge and center line at the top of the temporary support. After the adjustment is in place, continue to slowly drop the hook to the installation position.

[0022] After the main beam is installed in place, temporary supports are set on both sides of the main beam to prevent it from slipping or overturning, and the steel beam matching parts are used to temporarily fix the main beam in place.

[0023] Preferably, when the main beam is installed, the position of the diagonal brace is used to assist in adjusting the linear shape of the main beam, and the gap between two adjacent main beams is adjusted according to the steel beam matching parts.

[0024] Preferably, when removing the temporary supports in step S7, the supports at the mid-span are removed first, and then the supports at the piers. The temporary supports are removed in sequence from the mid-span toward the piers on both sides, and the removal is carried out in accordance with the principle of from top to bottom, first erect and then dismantle, and then erect and then dismantle.

[0025] Preferably, before removing the temporary support, select a beam settlement observation point on the top of the main beam and measure the beam elevation. During the removal of the temporary support, always observe the changes in the beam elevation and observe the bottom of the beam. If any abnormal situation occurs, stop the removal operation immediately.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention adopts a single crawler crane to lift the arch ribs, diagonal braces and main beam sections, which solves the problem of narrow construction sites, especially for lifting steel arch bridges near farmland and rivers. It also avoids the use of a larger crane, or is more economical than using a larger crane for lifting outside the span, greatly saving the lifting cost.

[0028] 2. Avoid hoisting multiple sections of the same beam, and assemble them after hoisting, which reduces more safety hazards when workers are working at height. Using a single crane to lift is also more economical and faster than using multiple cranes for double-machine lifting.

[0029] 3. The construction period is short. About 3 to 4 main beams can be hoisted every day. The speed of hoisting depends mainly on the speed of ground assembly. The use of a movable platform for assembly on the ground also avoids the defect of difficult steel beam assembly when the site is uneven. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a schematic diagram of the layout of temporary support.

[0032] Figure 2 It is a schematic diagram of the layout of temporary support.

[0033] Figure 3 It is a schematic diagram of the front view structure of the temporary support.

[0034] Figure 4 It is a side view structural diagram of the temporary support.

[0035] Figure 5 It is a top view of the temporary support fixed on the pier.

[0036] Figure 6 It is a side view of the temporary support fixed on the pier.

[0037] Figure 7 It is a schematic diagram of hoisting the arch rib segments on both sides.

[0038] Figure 8 It is a schematic diagram of the hoisting of the arch rib segments of the two main spans.

[0039] Fig. 9 This is a schematic diagram of hoisting diagonal braces from the side span to the middle span in sequence.

[0040] Fig.10 and Fig.11These are schematic diagrams of hoisting the main beams from the side span to the middle span.

[0041] Fig.12 It is a schematic diagram showing the construction platforms of the two temporary supports on the left and right being connected as one.

[0042] Fig.13 It is a top view of the construction platforms of the two temporary supports on the left and right sides connected as one.

[0043] Fig.14 It is a flow chart of steel arch bridge hoisting construction.

[0044] The meanings of the numbers in the figure are:

[0045] 1 is a temporary support, 11 is the support body, 12 is the construction platform, 13 is the distribution beam, 14 is the tooth plate,

[0046] 2 is the pier,

[0047] 3 is the arch rib segment,

[0048] 4 is a diagonal brace,

[0049] 5 is the main beam. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0051] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0052] In order to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings.

[0053] The present invention provides a method for hoisting and constructing a large-span steel arch bridge under a narrow working surface, which specifically comprises the following steps:

[0054] S1, pour the cap and build abutments and piers on the cap.

[0055] S2, install the arch foot segment on the abutment and install the temporary support 1 on the pier or cap.

[0056] In this embodiment, according to the site conditions and transportation conditions, the arch ribs of the steel arch bridge are divided into 20 segments in the longitudinal direction, and a total of 13 sets of temporary brackets 1 need to be installed for support. The layout diagram of the temporary brackets 1 is as follows: Figure 1 , Figure 2 shown.

[0057] like Figure 3 , Figure 4 As shown, the temporary support 1 includes a support body 11, a construction platform 12 horizontally arranged on the top of the support body 11, and a distribution beam 13 vertically fixed on the top of the support body 11. The distribution beam 13 is provided with a tooth plate 14 for adjusting the height of the support. In this embodiment, the support body 11 is composed of a column, a horizontal brace and a diagonal brace. The column adopts It is made of steel pipes, and the cross brace is made of 14a channel steel. The cross brace is connected between two vertical columns. A diagonal brace is diagonally fixed between the upper and lower cross braces. The diagonal brace is made of ∠70*6 angle steel. A construction platform 12 and a distribution beam 13 are fixed on the top of the bracket body 11. Double-piece 14a channel steel is used as the tooth plate 14 on the distribution beam 13. The tooth plate 14 can be used to adjust the height of the temporary bracket 1.

[0058] The main frame of the construction platform 12 is made of 14a channel steel, The scaffolding is made of steel pipes and scaffolding boards. A guardrail is arranged on the construction platform 12. The guardrail is composed of four guardrail columns and two upper and lower horizontal bars connecting the left and right guardrail columns. A double-track safety rope is also tied on the guardrail.

[0059] When installing the temporary support 1, a part of the temporary support is fixed on the pier 2 based on the pier 2, and the pad at the bottom of the temporary support is fixed to the pier 2 through expansion bolts, that is, the pad is welded at the bottom of the support body of the temporary support 1, bolt holes are opened at the corresponding positions of the pad, and the support column is fixed to the pier 2 through expansion bolts. Figure 5 , Figure 6 As shown, in this embodiment, a pad is welded and fixed to each foot of the bracket body of the temporary bracket 1, and each pad is provided with a bolt hole. The four pads are connected to the pier 2 by expansion bolts, so that the temporary bracket 1 is firmly fixed to the pier 2.

[0060] The other part of the temporary support is not at the pier, it is based on the foundation, fixed on the foundation, and pre-buried on the foundation. Steel mesh is used to strengthen the foundation, and the pedestal foundation is made of C30 concrete. In this way, the temporary bracket can be firmly connected to the concrete foundation by using the embedded parts pre-embedded on the pedestal.

[0061] It should be noted that the area under the temporary support and the crane occupation area must be backfilled and compacted. When backfilling, the construction slag must be not less than 70cm thick and compacted in layers according to the actual situation, and the bearing capacity must be not less than 150kpa.

[0062] It should also be noted that in order to facilitate the subsequent positioning of the main beam, when the temporary support is erected, the height of the construction platform should be 10-20mm higher than the theoretical elevation of the bottom of the main beam, so as to facilitate the adjustment of the elevation; when the main beam section is hoisted into place, the bottom elevation of the main beam section can be adjusted by jacks and small steel pipes.

[0063] Preferably, if Fig.12 , Fig.13 As shown, after all temporary supports are installed, in order to facilitate the subsequent welding construction of the left and right arch ribs, the construction platforms 12 of the left and right temporary supports are connected as a whole through the 14a channel steel, that is, the construction platforms 12 of the left and right temporary supports are connected as a whole, and then the 14a channel steel is covered with scaffolding boards, the scaffolding boards and the temporary supports are spot-welded and fixed, the 14a channel steel is welded and fixed to the support body of the left and right temporary supports, and a safety net is laid in the hole between the left and right construction platforms.

[0064] S3, using temporary support 1 to install arch rib segment 3: using crawler crane to first hoist the arch rib segments of both side spans, and then hoist the arch rib segments of both main spans.

[0065] like Figure 7 As shown, first hoist the arch rib segments 3 on both sides, that is, hoist K1-1 / K5-1→P1 / P4→K1-3 / K5-3 (closing)→K1-2 / K5-2 (closing)→cross bracing in sequence. The weight is the largest when hoisting the P1 / P4 segment, which is 18.0t. The accessories such as lifting lugs, wire ropes, and shackles are about 5.0t in total, and the maximum hoisting weight is 18.0+5.0=23t. The segment plus 1.2 times the dynamic load factor is 23*1.2=27.6t. At this time, the maximum hoisting radius is 14m, and the rated lifting capacity is 35.7t>27.6t, which meets the hoisting requirements;

[0066] Then, if Figure 8As shown, the arch rib segments 3 of the two main spans are hoisted, that is, P2 / P3→K3-1 / K3-6→K2-2 / K4-2 (closing)→K2-1 / K4-1 (closing)→cross bracing→K3-3 / K3-5 (closing)→K3-2 / K3-4 (closing)→cross bracing are hoisted in sequence. Among them, the weight is the largest when the P2 / P3 segment is hoisted, which is 13.2t. The lifting lugs, wire ropes, shackles, etc. are about 5.0t. The beam segment is added with 1.2 times the dynamic load factor It is (13.2+5.0)*1.2=21.84t. At this time, the lifting radius is 12m, and the rated lifting capacity is 44.0t>21.84t, which meets the lifting requirements; the lifting radius of the K3-3 segment is the largest, and the weight is 13.0t. The beam segment plus 1.2 times the dynamic load coefficient is (13.0+5.0)*1.2=21.6t. At this time, the lifting radius is 16m, and the rated lifting capacity is 29.9t>21.6t, which meets the lifting requirements.

[0067] In this embodiment, a 130t crawler crane is used to hoist the arch rib segment 3. After the arch rib segment 3 is hoisted into place, a temporary bracket 1 is used to support it.

[0068] After the arch rib segment 3 is pre-installed in place, it can be welded. When the arch rib is closed, the bottom plate butt weld is welded first, then the web butt weld is welded, and finally the top plate patch butt weld is welded. The arch rib web is welded symmetrically from the middle to both sides at the same time. The bottom plate and the top plate are welded by two-guard welding. After the bottom plate and the web are welded, the top plate patch is installed and welded with a steel liner.

[0069] S4, use crawler crane to hoist diagonal braces 4 from side span to middle span in sequence, and hoist the left and right diagonal braces along the bridge direction into place simultaneously.

[0070] After the diagonal brace 4 is hoisted, the diagonal brace 4 is temporarily fixed to the arch rib segment 3. After the subsequent bridge deck is installed, the position of the diagonal brace is adjusted according to the actual situation and the weld between the diagonal brace 4 and the arch rib 3 is welded. However, the diagonal braces on both sides of the U3 panel segment segment opening must be welded in advance.

[0071] like Fig. 9 As shown in the figure, when hoisting each diagonal brace, the weight of the diagonal brace C1 segment is the largest, which is 1.5t. The lifting lugs, wire ropes, shackles, etc. weigh approximately 5.0t. The beam segment plus 1.2 times the dynamic load factor is 6.5*1.2=7.8t. At this time, the hoisting radius is 16m, and the rated lifting capacity is 29.9t>7.8t, which meets the hoisting requirements.

[0072] S5, use crawler crane to hoist main beams 5 from side span to middle span in sequence, and use horse plates and I-beams to connect two adjacent main beams.

[0073] like Fig.10As shown, first hoist U1a / U5a→U1b / U5b→U2a / U4a→U2b / U4b in sequence. Among them, the weight is the largest when hoisting the U2b / U4b segment, which is 20.442t. The lifting lugs, wire ropes, shackles, etc. are about 5.0t beam segments plus 1.2 times the dynamic load factor is (20.442+5.0)*1.2=30.53t. At this time, the maximum hoisting radius is 14m, and the rated lifting capacity is 35.7t>30.53t, which meets the hoisting requirements;

[0074] Then, if Fig.11 As shown, U3-1a / U3-4a→U3-1b / U3-4b→U3-2a / U3-3a→U3-2b / U3-3b are hoisted in sequence. Among them, the weight is the largest when hoisting the U3-2a / U3-3a segment, which is 18.72t. The lifting lugs, wire ropes, shackles, etc. weigh about 5.0t. The beam segment plus 1.2 times the dynamic load factor is (18.72+5.0)*1.2=28.46t. At this time, the maximum hoisting radius is 14m, and the rated lifting capacity is 35.7t>28.46t, which meets the hoisting requirements.

[0075] The hoisting steps of each main beam section 5 are the same, that is, the surveyor first draws the main beam edge line and center line on the top of the temporary support 1 to facilitate the hoisting positioning of the main beam section, and at the same time verifies whether the elevation of the construction platform of the temporary support and the elevation of the supporting surface of the pier meet the specification requirements. If they do not meet the specification requirements, they are adjusted in time to avoid delaying the hoisting of the main beam section;

[0076] Then, the hook of the crawler crane is connected to the lifting lug on the main beam 5, and two guy ropes are tied to the main beam section 5 currently being lifted to control the state of the beam section in the air;

[0077] Then slowly lift the main beam 5. When the main beam 5 is lifted to the set height (more than 1m above the top surface of the temporary support), the crawler crane slowly rotates its main arm to the air above the bridge position, and then slowly drops the hook until the main beam stops about 10cm away from the top surface of the temporary support;

[0078] Then, adjust the position of the main beam 5 so that the edge line and center line of the bottom plate are aligned with the edge line and center line of the main beam at the top of the temporary support 1 respectively. After adjusting in place, continue to slowly drop the hook to the installation position;

[0079] After the main beam 5 is temporarily in place, temporary supports are set on both sides of the main beam 5 to prevent it from sliding or overturning, and the main beam in place is temporarily fixed using steel beam matching parts to prevent displacement of the steel beam section.

[0080] According to the above hoisting steps and hoisting sequence, each main beam section is hoisted in turn. After each main beam section is hoisted, the staff must cross-measure and lay out the top plate of the installed beam section, and at the same time perform elevation measurement to verify whether the plane direction and vertical direction of the main beam section are installed correctly. If the error exceeds the specification requirements, timely adjustments are made. The interface position of two adjacent main beam sections is connected by horse plates and I-beams.

[0081] After the main beam 5 is temporarily installed in place, the position of each beam section is fine-tuned to adjust the main beam line shape, and the position of the diagonal brace is used to assist in adjusting the line shape of the main beam. Preferably, when pre-assembling each beam section in the factory, sample punching holes can be punched on each beam section according to the pre-assembly effect, so that when fine-tuning the position of each beam section during the actual installation process, the sample punching holes on each beam section and the pre-assembly data can be used as a reference to monitor the installation process to ensure the line shape and accuracy of the main beam.

[0082] Specifically, there are expansion joints between the main beams U01, U02, and U03. The installation line shape of U01 and U02 only needs to control the elevations at both ends of the beam sections. The U03 beam section is divided into two sections longitudinally. The interfaces are pre-assembled and punched in the factory. During installation, reflective stickers are affixed to the top, and a total station is used for positioning and measurement to control the line shape.

[0083] When adjusting the line shape of the main beam 5, the gap between the two adjacent main beams should be adjusted according to the steel beam matching parts so that the welding spacing between the two main beams meets the requirements.

[0084] Preferably, when fine-tuning the position of the main beam section, a pad is added at the top to prevent damage to the steel beam coating. If a hard object contacts the steel beam, sleepers should be added to avoid direct contact with the steel beam, causing scratches and damage to the coating. At the same time, sacks and geotextiles can also be used to surround the easily contaminated parts of the main beam to prevent oil pollution from contaminating the steel beam.

[0085] After each main beam section is hoisted into place and the main beam line shape and the gap between two adjacent main beams are adjusted, the butt welds between the main beam sections can be carried out.

[0086] Before welding, the butt weld and both sides should be derusted by 50mm, and no water, oil, scale and other contaminants should be allowed. There should be no dust, water, oil and other contaminants within 120mm of the ceramic lining surface. When welding, first weld the transverse sections and then weld the transverse ring weld. The welding sequence is: longitudinal butt joint of top plate and bottom plate → butt joint of partition → transverse butt joint of top and bottom plates → butt joint of web plates → reserve fillet welds, stiffening ribs or inlays between web plates and top and bottom plates.

[0087] Preferably, in order to reduce the additional stress and deformation caused by welding, the straight web is welded from bottom to top; the transverse welds of the top and bottom plates are welded symmetrically from the center line of the bridge axis to both sides. The arc starting and arc stopping of the transverse welds of the top and bottom plates should be more than 200mm away from the longitudinal welds.

[0088] When pasting ceramic lining on butt weld, the longitudinal weld excess height should be ground to at least 60mm wide from the end to facilitate pasting of ceramic lining and flaw detection to ensure weld quality.

[0089] After the welding of each beam section interface is completed, the axis of the steel beam bridge needs to be measured, and the measurement data will serve as the basis for fine adjustment and control of the next beam section.

[0090] For welding operations on bridges, protective measures such as wind and rain protection should be taken. Operations should be stopped when the wind speed is greater than 5m / s or when it is raining heavily. When the wind speed is low or it is raining lightly, a wind shield or wind and rain shelter can be used for protection.

[0091] S6, lay the bridge deck and apply paint to the welds.

[0092] The bridge deck base is welded by double shielded welding, and the filling and covering are welded by a submerged arc automatic welding machine. For positions that are difficult to reach by automatic welding, CO2 semi-automatic gas shielded welding is used.

[0093] S7, remove the temporary support 1.

[0094] Preferably, before removing the temporary support 1, a beam settlement observation point is selected at the top of the main beam and the beam elevation is measured. During the removal of the temporary support, the changes in the beam elevation are always observed, and the bottom of the beam is observed. If any abnormal situation occurs, the removal operation is stopped immediately, and the cause is found out or discussed before the operation is carried out according to the adjustment plan.

[0095] Temporary support 1 is dismantled by using a 50-ton crane and a 5-ton forklift.

[0096] When dismantling temporary support 1, first dismantle the non-load-bearing temporary supports and then the load-bearing temporary supports, that is, first dismantle the supports at the mid-span and then the supports at the piers. Dismantle each temporary support in sequence from the mid-span toward the piers on both sides, and dismantle according to the principle of from top to bottom, first erect and then dismantle, and then erect and then dismantle. Dismantle the supports step by step from high to low, and do not dismantle the supports in separate facades or in two steps at the same time.

[0097] Before dismantling the support, set up a warning area and warning signs around it, use temporary guardrails to fence it off, and take traffic diversion measures to prohibit unauthorized personnel from entering the warning area.

[0098] This application adopts a single crawler crane to lift the arch ribs, diagonal braces, and main beam sections. The crawler crane's rotation radius is an open area, and there are no adverse factors that affect the lifting around it. The crawler crane is limited in its position on the construction access road. In this embodiment, the crawler crane's maximum segment weight is about 20.442t. Considering the weight of the lifting lugs, wire ropes, and hooks, the maximum lifting weight is about 25t. To ensure construction safety, a safety factor of 1.2 is considered, and the maximum lifting weight is 25×1.2=30t. The maximum lifting height is 8m. When the rotation radius is 14m, the arm length needs to be 31m. Therefore, according to the segmentation and lifting height, the Zoomlion QUY130 crawler crane can be selected, with a maximum rated total lifting weight of 130t. Under this working condition, the rated lifting weight of the crane is 35.7t>30t, which meets the lifting requirements.

[0099] And because the maximum hoisting weight is about 25t, when a single segment is hoisted, it is calculated as if three wire ropes are subjected to force at the same time. Then the force on a single wire rope is 25 / 3 / sin60°=25 / 3 / 0.866t=9.62t=96.2KN. Considering the 6-fold safety factor, it is 6×96.2KN / 0.82=703.9KN. Fiber core wire rope can meet the requirements of segment lifting. According to the segment weight, the maximum load of a single lifting point is 6.25t. Considering the 2 times safety factor, a 6-level 16t shackle can be selected to meet the lifting requirements.

[0100] Arrange 4 lifting eyes, the maximum weight of the segment is 20.442t, considering the weight of temporary lifting eyes, wire rope and hook, the lifting weight is about 25t, considering that there are 3 lifting eyes under force, the force on each lifting eye is F=25*3=8.3t, for the sake of safety, choose 10-20t lifting eyes.

[0101] The safety factor of the wire rope used for hoisting shall not be less than 6 times. When the ends of the wire rope are connected by braiding, the length of the braided part must not be less than 20 times the diameter of the wire rope, and should not be less than 300mm; and when the wire rope is fixed by rope clamps, the number and spacing of rope clamps matching the diameter of the wire rope shall comply with relevant regulations. The saddle of the rope clamp should be located on the side of the wire rope under stress, the U-shaped bolts should be at the tail end of the wire rope, and they shall not be used alternately. The distance between the last rope clamp and the rope head shall not be less than 140mm.

[0102] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for hoisting and constructing a large-span steel arch bridge under a narrow working surface, characterized in that: The specific steps include: S1, pouring the cap and building abutments and piers on the cap; S2, install the arch foot segment on the abutment and install temporary brackets on the pier or cap; S3, using temporary brackets to install the arch rib segments: using crawler cranes to first hoist the arch rib segments on both side spans, and then hoist the arch rib segments on the two main spans; S4: Use crawler crane to hoist diagonal braces from side span to middle span in sequence, and hoist diagonal braces on the left and right sides along the bridge direction into place simultaneously; S5: Use crawler crane to hoist the main beams from the side span to the middle span in sequence, and use horse plates and I-beams to connect two adjacent main beams; S6, laying the bridge deck and repainting the welds; S7, remove the temporary support.

2. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: The temporary support comprises a support body, a construction platform horizontally arranged on the top of the support body, and a distribution beam vertically fixed on the top of the support body, and a tooth plate for adjusting the height of the support is provided on the distribution beam.

3. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 2 is characterized in that: The height of the construction platform of the temporary support should be 10-20mm higher than the theoretical elevation of the bottom of the main beam.

4. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: The temporary support installed on the pier is fixed to the pier through the pad at the bottom; The temporary bracket installed on the pedestal is fixed to the embedded parts in the pedestal through expansion bolts.

5. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: In step S4, after the diagonal brace is installed, the diagonal brace and the arch rib segment are temporarily fixed, and after the bridge deck is installed, the weld between the diagonal brace and the arch rib is welded.

6. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: The specific steps of hoisting the main beam in step S5 are: Draw the main beam edge line and center line on the top of the temporary support, and verify whether the elevation of the temporary support construction platform and the support surface elevation of the pier meet the requirements of the specification; Connect the hook of the crawler crane to the lifting lug on the main beam, and then slowly lift the main beam. When the main beam is lifted to the set height, slowly rotate the main arm of the crawler crane to the air above the bridge position, and then slowly drop the hook until the main beam stops 10cm away from the top surface of the temporary support; Then, adjust the main beam position so that the bottom plate edge and center line are aligned with the main beam edge and center line at the top of the temporary support. After the adjustment is in place, continue to slowly drop the hook to the installation position. After the main beam is installed in place, temporary supports are set on both sides of the main beam to prevent it from slipping or overturning, and the steel beam matching parts are used to temporarily fix the main beam in place.

7. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 6 is characterized in that: When installing the main beam, the position of the diagonal brace is used to assist in adjusting the linear shape of the main beam, and the gap between two adjacent main beams is adjusted according to the steel beam matching parts.

8. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: When removing temporary supports in step S7, first remove the supports at the mid-span, then remove the supports at the piers, and then remove the temporary supports in sequence from the mid-span toward the piers on both sides, and remove them in accordance with the principle of from top to bottom, first erect and then dismantle, and then erect and then dismantle.

9. The method for hoisting and constructing a large-span steel arch bridge under a narrow working surface according to claim 1 is characterized in that: Before dismantling the temporary support, select a beam settlement observation point on the top of the main beam and measure the beam elevation. During the dismantling of the temporary support, always observe the changes in the beam elevation and observe the bottom of the beam. If any abnormal situation occurs, stop the dismantling operation immediately.

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