A construction method for cast-in-place steel truss support for high-altitude large-span upper crossbeam of cable tower

Abstract

The invention discloses a construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower, comprising the following steps: step 1, construction of reserved notches for steel corbels and pre-buried pipelines for steel corbel pull rods; step 2, steel component processing; welding of steel truss lifting units; step 3, cleaning reserved notches for steel corbels and pre-buried pipelines for steel corbel pull rods; step 4, installation of a side support support system; step 5, installation of a longitudinal distribution beam and arrangement of a lower sliding surface; step 6, lifting of the steel truss support in place and arrangement of an upper sliding surface; step 7, construction of upper crossbeam concrete pouring and equal strength; step 8, dismounting of the steel truss support; step 9, sliding and removal of the steel truss support; step 10, removal of the steel corbels and equal strength sealing of reserved notches for the steel corbels. The invention is based on the construction characteristics of the cast-in-place steel truss support of the upper cross beam; it adopts a side support point support system, and the construction method of the steel truss support is quickly hoisted into place in groups and hoisted and removed in groups by sliding. It has the construction advantages of strong adaptability, reasonable force structure, fast construction speed, high safety, etc.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a construction method for a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower. Background Art

[0002] Cable-stayed bridges are mainly composed of three parts: main beams, towers and cables. The towers are usually reinforced concrete structures. With the rapid development of transportation engineering and bridge technology, ultra-wide and ultra-large span cable-stayed bridges continue to emerge, and the height of the main towers of cable-stayed bridges also shows a positive correlation. There may be more than two beams between the two towers of the super-high main tower to ensure the overall stress performance of the main tower. The construction of the beam is a key link in the construction of the main tower. At present, the tower beams of cable-stayed bridges show a trend of high height and heavy weight, and the construction period is long. Therefore, the choice of the construction method of the beam has a great impact on the quality, safety and progress of the main tower construction.

[0003] Conventional construction methods for beams mainly include the ground bracket method and the pre-buried climbing cone group method, but for the upper beams with high height and heavy weight, both methods have certain limitations. If the ground bracket method is used for construction, a large amount of materials are required, the structure is relatively complex, and the cost is high, the construction period is long, and the risk is high; if the pre-buried climbing cone group is used for construction, it saves materials, but for the construction of upper beams with large spans and heavy weight, the force structure analysis of the climbing cone group is relatively complex, and the on-site pre-buried is greatly affected by human factors, the safety factor is difficult to guarantee, the construction risk is high, and the applicability is not strong. Summary of the invention

[0004] The purpose of the present invention is to provide a construction method for a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower, which has the advantages of fast construction speed, clear force transmission path, reasonable force structure, short construction period and high safety.

[0005] The object of the present invention is achieved in that:

[0006] A construction method for a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower, characterized by the following specific steps:

[0007] Step 1: Pre-install notches for steel corbels and pre-buried pipes for steel corbel tie rods, and cast segmental tower columns with notches for steel corbels:

[0008] The main tower is constructed normally. The steel corbel reserved slots are pre-buried in the segmental tower columns at the steel corbel reserved slots corresponding to the upstream and downstream tower columns. After the pre-buried steel corbel reserved slots are completed, the steel corbel pre-buried parts are reinforced around the steel corbel reserved slots. The steel corbel tie rods and pre-buried pipes are pre-buried above the pre-buried steel corbel reserved slots. The segmental tower column concrete is poured at the steel corbel reserved slots. The elevation of the steel corbel reserved slots is determined by the bottom elevation of the upper crossbeam and the height of the steel truss beam support.

[0009] Step 2: Steel component processing, welding steel truss hoisting unit:

[0010] While the main tower is being constructed, all the steel components, including steel truss brackets, steel brackets, and steel pads, are prefabricated in the steel structure processing plant, welded and formed nearby at the construction site, and the lifting lugs are set and the lifting equipment is ready; the steel truss bracket is connected as a whole by four steel trusses through a welded steel truss connection system, and every two steel trusses are assembled into a set of steel truss lifting units through a welded connection system between steel trusses, with a total of two sets of steel truss lifting units; each steel truss is composed of main load-bearing members, upper and lower chords, and web members;

[0011] Step 3: Clean the reserved notches of the steel corbels and the pre-buried pipes of the steel corbels tie rods:

[0012] After the main tower is constructed to the section flush with the upper beam, the climbing formwork frame on the inner wall of the main tower needs to be removed; before removing the climbing formwork frame, the working platform inside the climbing formwork can be used to clean out the reserved notches of the steel corbels and the pre-buried pipes of the steel corbel tie rods in advance;

[0013] Step 4: Install the side support system:

[0014] Start to install the side support support system. First, install the steel corbels one by one into the pre-buried notches of the steel corbels. Use the steel corbel tie rods to temporarily fix the top of the steel corbels. After all the steel corbels are installed, use the through-hole jack to pre-tension and anchor the steel corbel tie rods. The pre-tension force is not less than the required tonnage in the design. The steel corbels at the side support points are connected and fixed to the tower column of the main tower through the steel corbel tie rods. The side support support system is composed of the steel corbels, the reserved notches of the steel corbels of the tower column, the steel corbel tie rods, the pre-buried pipes of the steel corbel tie rods, and the tower column. The steel corbel tie rods are precision-rolled threaded steel.

[0015] Step 5, install the longitudinal distribution beam:

[0016] After the side support system is completed, install the steel pads on the top of the steel corbels in sequence, measure the top elevations of all the steel pads, and level them; then install the longitudinal distribution beam on the top of the steel pads, and lay the lower sliding surface stainless steel plate on the top of the longitudinal distribution beam, and weld it to fix it; the longitudinal distribution beam, steel pads and steel corbels should be temporarily intermittently welded and fixed;

[0017] Step 6: Lifting and positioning of steel truss brackets:

[0018] After the longitudinal distribution beam is firmly installed and fixed, the steel truss bracket is hoisted; the two groups of steel truss hoisting units of the steel truss bracket are hoisted and installed by tower crane. After the hoisting is completed, the steel truss connection system between the two groups of steel truss hoisting units is welded to form the whole steel truss bracket; the grouping of steel truss hoisting units must match the hoisting performance of the tower crane. Before the steel truss hoisting units are hoisted, the steel truss bracket is inspected and signed before use, and the key welds are inspected by radiography according to the design requirements; the sliding surface stainless steel plate is welded on the contact part between the bottom of the steel truss bracket and the longitudinal distribution beam;

[0019] Step 7, upper beam concrete pouring construction and equal strength:

[0020] When the steel truss beam support is installed, the bottom formwork system, side formwork, upper beam steel bars and prestressing are installed in sequence, and the upper beam concrete is poured; the bottom formwork system is composed of an "I"-shaped longitudinal distribution beam, an "I"-shaped transverse distribution beam and bamboo plywood from bottom to top; the strength and elastic modulus of the upper beam concrete reach 100%, and the upper beam prestressing construction is carried out within a period of not less than 7 days; the steel truss beam support of the subsequent upper beam can be dismantled only after the upper beam prestressing construction is completed;

[0021] Step 8, steel truss support dismounting operation:

[0022] When dismantling the steel truss support of the upper crossbeam, first set steel corbel reaction seats on both sides of the steel corbel, arrange unloading jacks on the steel corbel reaction seats, and simultaneously lift the unloading jacks to replace the steel pads to bear the force; cut off the steel pads, and simultaneously and slowly unload the steel truss support onto the steel corbel to complete the unloading operation of the steel truss support;

[0023] Step 9, sliding and removal of steel truss support:

[0024] Remove the bottom formwork system, then release the connection system between the two sets of steel truss girder hoisting units, set sliding reaction seats at the ends of the longitudinal distribution beams on the upstream and downstream sides, and arrange sliding through-core jacks at the ends of the sliding reaction seats on the upstream and downstream sides. Use the sliding through-core jacks to act on the sliding reaction seats, repeatedly tension the sliding pull rods, slowly move a set of steel truss girder hoisting units outward from the upper crossbeam, and then use a tower crane to lift them away. The tensioning operations of the sliding through-core jacks on the upstream and downstream sides must be synchronized;

[0025] Step 10: Remove the steel corbels and seal the reserved notches of the steel corbels:

[0026] After the steel truss support is dismantled, the longitudinal distribution beam, steel corbels and steel corbel tie rods are removed from top to bottom, and the steel corbel reserved notches are strongly sealed.

[0027] In step 1, the elevation of the reserved notch of the steel corbel is determined by the bottom elevation of the upper crossbeam and the height of the steel truss support; the elevation deviation of the reserved notch of the steel corbel is controlled within -10 to 0 mm; an embedded part anchor plate is provided around the reserved notch of the steel corbel to improve the local strength of the reserved notch of the steel corbel; a steel mesh is added to the concrete range at the position of the embedded part anchor plate to reinforce the concrete at the position of the embedded part anchor plate;

[0028] The diameter of the steel corbel tie rod embedded pipe is Φ70mm, and it is fixed in a "well" shape. The steel corbel tie rod embedded pipe needs to be horizontal, and the height difference between the two ends of the steel corbel tie rod embedded pipe should not exceed 5mm.

[0029] In step 2, the cross-sectional shape of the steel truss beam support in the transverse direction of the bridge is a right-angled trapezoid, and the top of the right-angled trapezoidal steel truss beam support corresponds to the chamfer of the lower part of the upper cross beam; the steel truss beam support is composed of 4 steel trusses, two steel trusses form a group of steel truss beam hoisting units, and the center distance between the two steel trusses of the steel truss beam hoisting unit is 1.5m, with a total of two groups; the 4 steel trusses of the steel truss beam support are symmetrically arranged at a spacing of 1.5+2.4+1.5m along the transverse center line of the upper cross beam; the main load-bearing rods, the upper and lower chords are 2HN500*200 double-piece; the main material of the web member and the connection system is channel steel;

[0030] The steel corbel is a boot-shaped steel corbel, and a hole with a diameter of Φ80mm for passing the steel corbel tie rod is opened on the upper part of the steel corbel; the steel pad is formed by processing of steel plate.

[0031] In step 4, the steel corbel tie rod is a finely rolled threaded steel bar with a diameter of Φ32mm; the steel corbel tie rod has the following two functions: first, to prevent the steel corbel from tipping over during construction; second, by applying pre-tension to the steel corbel tie rod, the bending moment at the root of the steel corbel when the steel corbel bears the upper beam load is reduced, and the structure of the steel corbel is optimized;

[0032] The steel corbel has a simple and light structure; the steel corbel and the reserved notch of the steel corbel are not fixed and can be reused; when installing the steel corbel, it is necessary to ensure that the steel corbel is in close contact with the steel corbel embedded parts in the reserved notch of the tower column steel corbel on site;

[0033] The pre-tensioning equipment for the steel corbel rod is an 80t hydraulic through-hole top, which is pre-tensioned one by one. The pre-tensioning force of a single steel corbel rod is 32t. After installation, the steel corbel should fit tightly against the side wall of the tower column.

[0034] In step 5, the top surface elevation of the steel pad is padded and leveled with a steel plate of standard thickness; both sides of the longitudinal distribution beam extend 2m beyond the upper crossbeam, serving as an outer slideway for the upper crossbeam range when the steel truss beam support is removed;

[0035] The lower sliding surface stainless steel laid on the top surface of the longitudinal distribution beam is made of mirror stainless steel, which is used as a sliding resistance reduction material; it is welded and fixed with special welding rods.

[0036] In step 6, the weight of a single set of steel truss lifting units constituting the steel truss support is about 29.0t. Both sets of steel truss lifting units are hoisted by an STL1400D tower crane with a maximum lifting capacity of 68t. According to the horizontal center line of the main tower, each set of steel truss lifting units is accurately positioned and lowered;

[0037] After the first set of steel truss hoisting units are in place, auxiliary diagonal bars are welded on the large and small mileage sides to temporarily fix them to prevent overturning; after the first set is in place and temporarily fixed, the second set of steel truss hoisting units are hoisted in the same way; after the two sets of steel truss hoisting units are in place, the steel truss connection system between the two sets of steel truss hoisting units is constructed to connect the two sets of steel truss hoisting units into a whole;

[0038] The material of the upper sliding surface stainless steel plate welded at the contact part between the bottom of the steel truss support and the longitudinal distribution beam is mirror stainless steel; the upper sliding surface stainless steel at the bottom of the steel truss support and the sliding surface stainless steel laid on the top surface of the longitudinal distribution beam slide against each other to form a steel truss support sliding system, which is required when the steel truss support is dismantled.

[0039] In step 8, the unloading jack is a 100t screw jack with a main body height of 452mm; the height of the steel pad is 300mm, and the maximum one-time stroke of the unloading jack is 200mm. To ensure that the longitudinal distribution beam and the steel truss support are unloaded onto the steel corbel as a whole, the height between the steel corbel reaction seat and the bottom surface of the longitudinal distribution beam shall not be less than the sum of the screw top height and the steel pad height, 752mm.

[0040] The steel truss support is dismounted using a cyclic dismounting method. The dismounting is carried out in two steps. The specific operations are as follows:

[0041] A. The top surface of the steel bull leg reaction seat is padded with a steel plate with a total height of 120mm. The unloading jack is arranged on the steel bull leg reaction seat. The unloading jack is within the working stroke range, and the top is lifted to replace the steel pad to bear the force, and the steel pad is cut off and removed;

[0042] B. If the unloading height of the steel truss support is 300mm, which is greater than the working stroke of the unloading jack, it will be dropped in two times, 150mm each time;

[0043] C. After the steel pad is removed, a steel plate with a total height of 150mm is placed on the steel bracket. The unloading jacks on both sides are retracted and dropped synchronously. The first drop is 150mm. The load of the longitudinal distribution beam and the steel truss beam bracket is transferred by the unloading jacks to the steel plate on the steel bracket. Remove the steel plate with a total height of 120mm under the unloading jack, lift it up synchronously again, lift up the longitudinal distribution beam and the steel truss beam bracket again, remove the steel plate with a total height of 150mm on the steel bracket, and drop the jack synchronously. After two cycles of unloading, the longitudinal distribution beam and the steel truss beam bracket are lowered by 300mm as a whole and placed on the steel bracket. The unloading work of the steel truss beam bracket is completed.

[0044] D. After the longitudinal distribution beam and steel truss support are unloaded into place, and in order to balance the bending moment and reaction force generated by the external sliding of the lower beam, the longitudinal distribution beam needs to be welded and fixed with the steel corbel.

[0045] In step 9, lubricating grease is applied to the top surface of the stainless steel of the lower sliding surface of the longitudinal distribution beam to reduce the sliding friction of the steel truss beam support;

[0046] The sliding reaction seat reserves a Φ40 hole for the sliding tension rod, and a Φ40 sliding anchor hole is set at the end of the steel truss support. The anchor end of the sliding tension rod is anchored with a 20mm thick pad and a double nut; the sliding tension rod is Φ32 finely rolled threaded steel; the sliding through-core jack uses a 50t through-core jack;

[0047] The sliding through-hole jack, sliding tension rod, and steel truss anchorage points must be in the same straight line;

[0048] Mark the top surface of the stainless steel plate of the longitudinal distribution beam on the upstream and downstream sides with a ruler. The tensioning and sliding movement on the upstream and downstream sides must be synchronized, and the sliding speed should not exceed 0.05m / min.

[0049] Before the steel truss lifting unit is towed out, the longitudinal distribution beam and the steel corbel must be vertically connected and firmly locked using fine-rolled threaded steel.

[0050] Compared with the prior art, the advantages of the present invention are:

[0051] In the construction method of the cast-in-place steel truss support of the upper crossbeam of the present invention, the side support point support system of the upper crossbeam support adopts a "combined support system of boot-shaped steel corbels + pre-tensioned precision-rolled threaded steel bars"; compared with the construction using pre-buried climbing cone groups, it has the advantages of simple and light structure, clear force, and reusability.

[0052] In the construction method of the cast-in-place steel truss support for the upper cross beam of the present invention, the upper cross beam steel truss support "prefabricates steel components in factories, assembles steel truss hoisting units on site, and quickly hoists the steel truss hoisting units into place". Compared with traditional floor-standing supports, it has the advantages of less construction consumables, shorter construction period, reduced high-altitude working time and higher safety.

[0053] In the construction method of the cast-in-place steel truss support for the upper cross beam of the present invention, the upper cross beam steel truss support is dismantled, and upper and lower sliding surfaces are set between the steel truss support and the longitudinal distribution beam. The steel truss supports are grouped and directly hoisted and dismantled by the sliding method. Compared with the overall dismantling method of lowering the support, there is no need to arrange large-tonnage winches and pulley groups and other dismantling equipment on the top surface of the upper cross beam. The construction is simple and the operability is high.

[0054] The invention is based on the construction characteristics of the cast-in-place steel truss support of the upper cross beam: adopting a side support point support system, the steel truss support is quickly hoisted into place in groups, and the steel truss support is hoisted and dismantled in groups by sliding. It has the construction advantages of strong adaptability, reasonable force structure, fast construction speed, high safety, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is the general arrangement drawing of the cast-in-place steel truss support of the upper crossbeam;

[0056] Figure 2 yes Figure 1 Side view of

[0057] Figure 3 It is a schematic diagram of the arrangement of the reserved notches of the steel corbel and the reserved pipes of the steel corbel tie rod;

[0058] Figure 4 It is a structural diagram of the side support system;

[0059] Figure 5 This is a schematic diagram of the arrangement of the steel truss support bracket reaction seat and unloading jack;

[0060] Figure 6 It is a large-scale drawing of the upper and lower sliding surfaces between the steel truss support and the longitudinal distribution beam;

[0061] Figure 7 This is a schematic diagram of the sliding removal of the steel truss support;

[0062] Markings in the figure: 1-steel corbel embedded parts, 2-steel corbel, 3-steel corbel pull rod, 4-steel pad, 5-longitudinal distribution beam, 6-tower column, 7-steel truss support, 8-bottom formwork system, 9-upper crossbeam, 10-tower crane 200-steel corbel reserved notch, 201-steel corbel reaction seat, 202-unloading jack, 300-steel corbel pull rod embedded pipe, 401-lower sliding surface stainless steel plate, 402-upper sliding surface stainless steel plate, 501-sliding reaction seat, 502-sliding through-hole jack, 503-sliding pull rod, 700-steel truss connection system, 701-steel truss, 702-steel truss lifting unit. DETAILED DESCRIPTION

[0063] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0064] See also Figures 1 to 7 As shown, an embodiment of the present invention provides a construction method for a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower, and the specific steps are as follows:

[0065] Step 1: Pre-install notches for steel corbels and pre-buried pipes for steel corbel tie rods, and cast segmental tower columns with notches for steel corbels:

[0066] The main tower is constructed normally. The segmental tower column 6 corresponding to the steel corbel reserved slot 200 position of the upstream and downstream tower columns is pre-embedded with the steel corbel reserved slot 200. After the pre-embedding is completed, the steel corbel pre-embedded parts 1 are reinforced around the steel corbel reserved slot 200, the steel corbel tie rod pre-embedded pipe 300 is pre-embedded above the reserved steel corbel reserved slot 200, and the segmental tower column 6 at the steel corbel reserved slot 200 position is poured with concrete. The elevation of the steel corbel reserved slot 200 is determined by the bottom elevation of the upper crossbeam 9 and the height of the steel truss beam support 7;

[0067] Step 2: Steel component processing, welding steel truss hoisting unit:

[0068] While the main tower is being constructed, all the steel components, such as the steel truss support 7, the steel bracket 2, and the steel pad 4, are prefabricated in a steel structure processing plant and welded together at the construction site. The steel truss support 7 is composed of four steel trusses 701 connected as a whole by a welded steel truss connection system 700. Every two steel trusses 701 are assembled into a set of steel truss hoisting units 702 by a welded steel truss connection system 700, and there are two sets of steel truss hoisting units 702 in total.

[0069] Step 3: Clean the reserved notches of the steel corbels and the pre-buried pipes of the steel corbels tie rods:

[0070] When the tower column 6 is constructed to be flush with the upper crossbeam 9 and the concrete curing age of the tower column 6 meets the requirements, the climbing formwork frame on the inner wall of the tower column 6 needs to be removed; before removing the climbing formwork frame, the working platform inside the climbing formwork can be used to clean out the reserved notches 200 of the steel corbels and the pre-buried pipes 300 of the steel corbel tie rods in advance.

[0071] Step 4: Install the side support system

[0072] Start to install the side support point support system. First, install the steel corbels 2 one by one into the steel corbel pre-buried slots 200. The top of the steel corbels 2 is temporarily fixed with steel corbel tie rods 3. After all the steel corbels 2 are installed, use through-hole jacks to pre-tension and anchor the steel corbel tie rods 3. The pre-tension force is not less than the required tonnage of the design. The steel corbels 2 at the side support points are connected and fixed to the tower column 6 of the main tower through the steel corbel tie rods 3. The side support point support system is composed of the steel corbels 2, the steel corbel pre-buried slots 200 of the tower column, the steel corbel tie rods 3, the steel corbel tie rod pre-buried pipes 300, and the tower column 6. The steel corbel tie rods 3 are precision-rolled threaded steel.

[0073] Step 5: Install the longitudinal distribution beam

[0074] After the side support system is completed, install the steel pads 4 above the steel corbels 2 in sequence, and measure the top elevations of all the steel pads 4 to level them; then install the longitudinal distribution beam 5 on the top of the steel pads 4, and lay the lower sliding surface stainless steel plate 401 on the top of the longitudinal distribution beam 5, and weld it to fix it; the longitudinal distribution beam 5, the steel pads 4 and the steel corbels 2 should be temporarily intermittently welded and fixed;

[0075] Step 6, Steel Truss Support Hoisting: Put in Place

[0076] After the longitudinal distribution beam 5 is installed and fixed firmly, the steel truss support 7 is hoisted; the two groups of steel truss hoisting units 702 of the steel truss support 7 are hoisted and installed by the tower crane 10. After the hoisting is completed, the steel truss connection system 700 between the two groups of steel truss hoisting units 702 is welded to form the steel truss support 7 as a whole; the grouping of the steel truss hoisting unit 702 needs to match the hoisting performance of the tower crane 10. Before the steel truss hoisting unit 702 is hoisted, the steel truss support 7 is inspected and signed before use, and the key welds are inspected by radiography according to the design requirements; the upper sliding surface stainless steel plate 402 is welded to the contact part between the bottom of the steel truss support 7 and the longitudinal distribution beam 5;

[0077] Step 7: Concrete pouring of upper beam and equal strength

[0078] When the steel truss beam support 7 is installed, the bottom formwork system 8, the side formwork, the upper cross beam 9 steel bars and prestressing, and the upper cross beam 9 concrete are poured in sequence; the bottom formwork system 8 is composed of an "I"-shaped longitudinal distribution beam, an "I"-shaped transverse distribution beam and bamboo plywood from bottom to top; the concrete strength and elastic modulus of the upper cross beam 9 reach 100%, and the upper cross beam 9 prestressing construction is carried out for no less than 7 days; the steel truss beam support 7 of the upper cross beam 9 can be removed only after the prestressing construction of the upper cross beam 9 is completed;

[0079] Step 8: Dismounting of steel truss support

[0080] When the steel truss beam support 7 of the upper cross beam 9 is removed, firstly, a steel corbel reaction seat 201 is set on both sides of the steel corbel 2, and a discharging jack 202 is arranged on the steel corbel reaction seat 201, and the discharging jack 202 is synchronously lifted to replace the steel pad 4 to bear the force; the steel pad 4 is cut off, and the steel truss beam support 7 is synchronously and slowly unloaded onto the steel corbel 3 to complete the dismounting operation of the steel truss beam support 7;

[0081] Step 9: Sliding and removal of steel truss support

[0082] The bottom formwork system 8 is removed, and then the connection system between the two groups of steel truss girder hoisting units 702 is released. Sliding reaction seats 501 are set at the ends of the longitudinal distribution beams 5 on the upstream and downstream sides, and sliding through-core jacks 502 are arranged at the ends of the sliding reaction seats 501 on the upstream and downstream sides. The sliding through-core jacks 502 act on the sliding reaction seats 501 to repeatedly tension the sliding rods 503 to slowly move a group of steel truss girder hoisting units 702 outward from the upper cross beam 7, and then use the tower crane 10 to lift them away; the tensioning operation of the sliding through-core jacks 502 on the upstream and downstream sides needs to be synchronized;

[0083] Step 10: Remove the steel corbels and seal the reserved notches of the steel corbels.

[0084] After the steel truss beam support 7 is dismantled, the longitudinal distribution beam 5, the steel corbel 2 and the steel corbel tie rod 3 are dismantled in sequence from top to bottom, and the reserved notches 200 of the steel corbel are strongly sealed.

[0085] The present invention is not limited to the above-mentioned embodiments. For those skilled in the art, improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A construction method for a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower, characterized in that: The steps include: Step 1: Pre-install notches for steel corbels and pre-buried pipes for steel corbel tie rods, and cast segmental tower columns with notches for steel corbels: The main tower is constructed normally. The steel corbel reserved slots are pre-buried in the segmental tower columns at the steel corbel reserved slots corresponding to the upstream and downstream tower columns. After the pre-buried steel corbel reserved slots are completed, the steel corbel pre-buried parts are reinforced around the steel corbel reserved slots. The steel corbel tie rods and pre-buried pipes are pre-buried above the pre-buried steel corbel reserved slots. The segmental tower column concrete is poured at the steel corbel reserved slots. The elevation of the steel corbel reserved slots is determined by the bottom elevation of the upper crossbeam and the height of the steel truss beam support. Step 2: Steel component processing, welding steel truss hoisting unit: While the main tower is being constructed, all the steel components, including steel truss brackets, steel brackets, and steel pads, are prefabricated in the steel structure processing plant, welded and formed nearby at the construction site, and the lifting lugs are set and the lifting equipment is ready; the steel truss bracket is connected as a whole by four steel trusses through a welded steel truss connection system, and every two steel trusses are assembled into a set of steel truss lifting units through a welded connection system between steel trusses, with a total of two sets of steel truss lifting units; each steel truss is composed of main load-bearing members, upper and lower chords, and web members; Step 3: Clean the reserved notches of the steel corbels and the pre-buried pipes of the steel corbels tie rods: After the main tower is constructed to the section flush with the upper beam, the climbing formwork frame on the inner wall of the main tower needs to be removed; before removing the climbing formwork frame, the working platform inside the climbing formwork can be used to clean out the reserved notches of the steel corbels and the pre-buried pipes of the steel corbel tie rods in advance; Step 4: Install the side support system: Start to install the side support support system. First, install the steel corbels one by one into the pre-buried notches of the steel corbels. Use the steel corbel tie rods to temporarily fix the top of the steel corbels. After all the steel corbels are installed, use the through-hole jack to pre-tension and anchor the steel corbel tie rods. The pre-tension force is not less than the required tonnage in the design. The steel corbels at the side support points are connected and fixed to the tower column of the main tower through the steel corbel tie rods. The side support support system is composed of the steel corbels, the reserved notches of the steel corbels of the tower column, the steel corbel tie rods, the pre-buried pipes of the steel corbel tie rods, and the tower column. The steel corbel tie rods are precision-rolled threaded steel. Step 5, install the longitudinal distribution beam: After the side support system is completed, install the steel pads on the top of the steel corbels in sequence, measure the top elevations of all the steel pads, and level them; then install the longitudinal distribution beam on the top of the steel pads, and lay the lower sliding surface stainless steel plate on the top of the longitudinal distribution beam, and weld it to fix it; the longitudinal distribution beam, steel pads and steel corbels should be temporarily intermittently welded and fixed; Step 6: Lifting and positioning of steel truss brackets: After the longitudinal distribution beam is firmly installed and fixed, the steel truss bracket is hoisted; the two groups of steel truss hoisting units of the steel truss bracket are hoisted and installed by tower crane. After the hoisting is completed, the steel truss connection system between the two groups of steel truss hoisting units is welded to form the whole steel truss bracket; the grouping of steel truss hoisting units must match the hoisting performance of the tower crane. Before the steel truss hoisting units are hoisted, the steel truss bracket is inspected and signed before use, and the key welds are inspected by radiography according to the design requirements; the sliding surface stainless steel plate is welded on the contact part between the bottom of the steel truss bracket and the longitudinal distribution beam; Step 7: Concrete pouring of upper beam: When the steel truss beam support is installed, the bottom formwork system, side formwork, upper beam steel bars and prestressing are installed in sequence, and the upper beam concrete is poured; the bottom formwork system is composed of an "I"-shaped longitudinal distribution beam, an "I"-shaped transverse distribution beam and bamboo plywood from bottom to top; the strength and elastic modulus of the upper beam concrete reach 100%, and the upper beam prestressing construction is carried out within a period of not less than 7 days; the steel truss beam support of the upper beam can be removed only after the upper beam prestressing construction is completed; Step 8, steel truss support dismounting operation: When dismantling the steel truss support of the upper crossbeam, first set steel corbel reaction seats on both sides of the steel corbel, arrange unloading jacks on the steel corbel reaction seats, and simultaneously lift the unloading jacks to replace the steel pads to bear the force; cut off the steel pads, and simultaneously and slowly unload the steel truss support onto the steel corbel to complete the unloading operation of the steel truss support; Step 9, sliding and removal of steel truss support: Remove the bottom formwork system, then release the connection system between the two sets of steel truss girder hoisting units, set sliding reaction seats at the ends of the longitudinal distribution beams on the upstream and downstream sides, and arrange sliding through-core jacks at the ends of the sliding reaction seats on the upstream and downstream sides. Use the sliding through-core jacks to act on the sliding reaction seats, repeatedly tension the sliding pull rods, slowly move a set of steel truss girder hoisting units outward from the upper crossbeam, and then use a tower crane to lift them away. The tensioning operations of the sliding through-core jacks on the upstream and downstream sides must be synchronized; Step 10, remove the steel corbel and close the reserved notch of the steel corbel: After the steel truss support is dismantled, the longitudinal distribution beam, steel corbel and steel corbel tie rod are removed from top to bottom, and the reserved notches of the steel corbel are closed.

2. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized by: In step 1, the elevation of the reserved notch of the steel corbel is determined by the bottom elevation of the upper crossbeam and the height of the steel truss support; the elevation deviation of the reserved notch of the steel corbel is controlled within -10 to 0 mm; an embedded part anchor plate is provided around the reserved notch of the steel corbel to improve the local strength of the reserved notch of the steel corbel; a steel mesh is added to the concrete range at the position of the embedded part anchor plate to reinforce the concrete at the position of the embedded part anchor plate; The diameter of the steel corbel tie rod embedded pipe is Φ70mm, and it is fixed in a "well" shape. The steel corbel tie rod embedded pipe needs to be horizontal, and the height difference between the two ends of the steel corbel tie rod embedded pipe should not exceed 5mm.

3. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized by: In step 2, the cross-sectional shape of the steel truss beam support in the transverse direction of the bridge is a right-angled trapezoid, and the top of the right-angled trapezoidal steel truss beam support corresponds to the chamfer of the lower part of the upper cross beam; the steel truss beam support is composed of 4 steel trusses, two steel trusses form a group of steel truss beam hoisting units, and the center distance between the two steel trusses of the steel truss beam hoisting unit is 1.5m, with a total of two groups; the 4 steel trusses of the steel truss beam support are symmetrically arranged at a spacing of 1.5+2.4+1.5m along the transverse center line of the upper cross beam; the main load-bearing rods and the upper and lower chord rods are all 2HN500*200 double-piece; the material of the web rod and the connection system is channel steel; The steel corbel is a boot-shaped steel corbel, and a hole with a diameter of Φ80mm for passing the steel corbel tie rod is opened on the upper part of the steel corbel; the steel pad is formed by processing of steel plate.

4. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized in that: In step 4, the steel corbel tie rod is a precision-rolled threaded steel bar with a diameter of Φ32 mm; When installing the steel corbel, it is necessary to ensure that the steel corbel is in close contact with the steel corbel embedded parts in the reserved notches of the tower column steel corbel on site; The pre-tensioning equipment for the steel corbel rod is an 80t hydraulic through-hole top, which is pre-tensioned one by one. The pre-tensioning force of a single steel corbel rod is 32t. After installation, the steel corbel should fit tightly against the side wall of the tower column.

5. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized in that: In step 5, the top surface elevation of the steel pad is padded and leveled with a steel plate of standard thickness; both sides of the longitudinal distribution beam extend 2m beyond the upper crossbeam, serving as an outer slideway for the upper crossbeam range when the steel truss beam support is removed; The lower sliding surface stainless steel laid on the top surface of the longitudinal distribution beam is made of mirror stainless steel, which is used as a sliding resistance reduction material; it is welded and fixed with special welding rods.

6. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized by: In step 6, the weight of a single set of steel truss lifting units constituting the steel truss support is about 29.0t. Both sets of steel truss lifting units are hoisted by an STL1400D tower crane with a maximum lifting capacity of 68t. According to the horizontal center line of the main tower, each set of steel truss lifting units is accurately positioned and lowered; After the first set of steel truss hoisting units are in place, auxiliary diagonal bars are welded on the large and small mileage sides to temporarily fix them to prevent overturning; after the first set is in place and temporarily fixed, the second set of steel truss hoisting units are hoisted in the same way; after the two sets of steel truss hoisting units are in place, the steel truss connection system between the two sets of steel truss hoisting units is constructed to connect the two sets of steel truss hoisting units into a whole; The material of the upper sliding surface stainless steel plate welded at the contact part between the bottom of the steel truss support and the longitudinal distribution beam is mirror stainless steel; the upper sliding surface stainless steel at the bottom of the steel truss support and the sliding surface stainless steel laid on the top surface of the longitudinal distribution beam slide against each other to form a steel truss support sliding system, which is required when the steel truss support is dismantled.

7. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized by: In step 8, the unloading jack is a 100t screw jack with a main body height of 452mm; the height of the steel pad is 300mm, and the maximum one-time stroke of the unloading jack is 200mm. To ensure that the longitudinal distribution beam and the steel truss support are unloaded onto the steel corbel as a whole, the height between the steel corbel reaction seat and the bottom surface of the longitudinal distribution beam shall not be less than the sum of the screw top height and the steel pad height, 752mm.

8. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 7 is characterized by: The steel truss support is dismounted using a cyclic dismounting method. The dismounting is carried out in two steps. The specific operations are as follows: A. The top surface of the steel bull leg reaction seat is padded with a steel plate with a total height of 120mm. The unloading jack is arranged on the steel bull leg reaction seat. The unloading jack is within the working stroke range, and the top is lifted to replace the steel pad to bear the force, and the steel pad is cut off and removed; B. If the unloading height of the steel truss support is 300mm, which is greater than the working stroke of the unloading jack, it will be dropped in two times, 150mm each time; C. After the steel pad is removed, a steel plate with a total height of 150mm is placed on the steel bracket. The unloading jacks on both sides are retracted and dropped synchronously. The first drop is 150mm. The load of the longitudinal distribution beam and the steel truss beam bracket is transferred by the unloading jacks to the steel plate on the steel bracket. Remove the steel plate with a total height of 120mm under the unloading jack, lift it up synchronously again, lift up the longitudinal distribution beam and the steel truss beam bracket again, remove the steel plate with a total height of 150mm on the steel bracket, and drop the jack synchronously. After two cycles of unloading, the longitudinal distribution beam and the steel truss beam bracket are lowered by 300mm as a whole and placed on the steel bracket. The unloading work of the steel truss beam bracket is completed. D. After the longitudinal distribution beam and steel truss support are unloaded into place, and in order to balance the bending moment and reaction force generated by the external sliding of the lower beam, the longitudinal distribution beam needs to be welded and fixed with the steel corbel.

9. The construction method of a cast-in-place steel truss support for a high-altitude large-span upper crossbeam of a cable tower according to claim 1 is characterized by: In step 9, lubricating grease is applied to the top surface of the stainless steel of the lower sliding surface of the longitudinal distribution beam to reduce the sliding friction of the steel truss beam support; The sliding reaction seat reserves a Φ40 hole for the sliding tension rod, and a Φ40 sliding anchor hole is set at the end of the steel truss support. The anchor end of the sliding tension rod is anchored with a 20mm thick pad and a double nut; the sliding tension rod is Φ32 finely rolled threaded steel; the sliding through-core jack uses a 50t through-core jack; The sliding through-hole jack, sliding tension rod, and steel truss anchorage points must be in the same straight line; Mark the top surface of the stainless steel plate of the longitudinal distribution beam on the upstream and downstream sides with a ruler. The tensioning and sliding movement on the upstream and downstream sides must be synchronized, and the sliding speed should not exceed 0.05m / min. Before the steel truss lifting unit is towed out, the longitudinal distribution beam and the steel corbel must be vertically connected and firmly locked using fine-rolled threaded steel.

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