CN115418951A

CN115418951A - Assembly type cantilever bent cap support and construction method thereof

Info

Publication number: CN115418951A
Application number: CN202210615784.3A
Authority: CN
Inventors: 徐声亮; 王明达; 陈生云
Original assignee: Ningbo Municipal Engineering Construction Group Co Ltd
Current assignee: Ningbo Municipal Engineering Construction Group Co Ltd
Priority date: 2022-05-31
Filing date: 2022-05-31
Publication date: 2022-12-02
Anticipated expiration: 2042-05-31
Also published as: CN115418951B

Abstract

The invention discloses an assembled cantilever bent cap support and a construction method thereof. The assembled cantilever bent cap support comprises an upper structure, a supporting sand box and a lower structure; the upper structure comprises two truss type beam bodies which are arranged in parallel, the lower structure comprises a middle fulcrum, and the truss type beam bodies are of an assembled structure and are formed by splicing a plurality of prefabricated module type sections on site; the prefabricated module type sections comprise main truss girders and variable height truss girders; two sections of main truss girders are arranged at the positions of the middle fulcrums of the truss girder bodies, and are correspondingly a first main truss girder and a second main truss girder; the first main truss beam and the second main truss beam are spliced into a whole through a first connecting assembly; the outer sides of the first main truss girder and the second main truss girder are respectively spliced with a section of heightening truss girder through a second connecting assembly, and the section of heightening truss girder is the first heightening truss girder. Therefore, the invention has reliable connection measures, low requirements for field assembly, better universality and enough bearing capacity and rigidity.

Description

Assembled cantilever bent cap support and construction method thereof

Technical Field

The invention relates to an assembled cantilever bent cap support and a construction method thereof, belongs to the field of civil engineering construction, belongs to an industrialized large-scale temporary measure structure, can be used as a temporary support for large-volume concrete structure construction requiring high-altitude operation, and is particularly suitable for urban expressway overhead bent cap construction.

Background

The expressway viaduct has become an important means for solving traffic jam in cities, and urban viaducts are built or are built on a large scale in main cities in China.

At present, the urban expressway is mainly provided with a double-column cantilever type cover beam, 8 prefabricated small box beams are configured to form an expressway driving route with 6 bidirectional lanes, the width of a bridge deck is about 25.5m, and the width of the cover beam is about 25-26.5 m, as shown in the specification; meanwhile, in the widening section spliced with the ramp, the upper structure is widened to 10-12 prefabricated small box girders, the lower structure of the box girders is correspondingly adjusted to be a four-column type continuous cover girder, the width of the bridge deck is wide, and the length of the cover girder is about 36-45 m. In addition, the ramp of the urban expressway overhead is usually 7.5m wide, the requirement of a one-way 2-lane is met, and the width of the cover beam is about 8.5m.

Different professional design houses in China slightly differ about the structural form of the urban expressway overhead bent cap, wherein the two key parameters of the bent cap section structure (form & width) and the concrete volume (dead weight) mainly have great influence on a bracket system. At present, the urban expressway is mainly provided with a double-column cantilever type bent cap, the maximum total length of the bent cap is 33.5m, and the minimum total length is 15.6m; the maximum cantilever length is 15m, and the minimum cantilever length is 4.5m; the maximum pillar outer spacing is 12m, and the minimum pillar outer spacing is 2.8m. Wherein the total length of the common bent cap is about 21.98 m-27.6 m, the length of the cantilever is 7-10 m, and the distance between the outer sides of the columns is 6 m-10 m. The difference of the design standard is small, so the prefabrication and assembly feasibility of the bent cap support is high, and the universalization can be realized.

At present, the commonly used stent systems mainly include: the full framing system, bailey truss system and cantilever mounting system. Wherein:

full hall support system can't adapt to city overhead and erect, mainly embodies in 2 aspects:

1) Occupying the land for operation, and extruding a temporary channel protection way and a construction operation channel space;

the city expressway construction usually lags behind the expansion and development of cities, so that the project construction land range is limited, and the construction site is very narrow. To newly-built project, conventional full hall support system need occupy bent cap projection scope construction place, can lead to the fact serious influence to vehicle in the place, fills the access road outside the projection scope, will cause the repeated excavation and the waste of ground timber, not only the increase cost and be not conform to green requirement. For the rapid reconstruction project of the existing road, the more space occupied by the bent cap support system, the larger the workload of traffic guidance and reconstruction, especially the occupation of the main road, and the serious influence on urban traffic.

2) The alternation of new and old processes and the cost increase greatly

In the past, the bowl buckle type support is adopted in the domestic conventional full-scale support system, and the process level and the cost control are balanced. In recent years, in order to match with the upgrading and transformation of the building industry, governments in various places gradually push disc buckle type bracket systems to replace bowl buckle type brackets. The dish buckle type support is mainly used for upgrading and transforming a bowl buckle type support system in two aspects of a vertical rod piece connecting node structure and a transverse rod piece node structure. Compared with the bowl buckle type bracket system which is generally adopted in the prior art, the cost of the dish buckle type bracket system is greatly increased and is about 1.8-2.0 times of that of the bowl buckle type bracket.

The temporary support of a 'cantilever, long span' structure is difficult to shoulder by the bailey truss system because:

1) Mismatch between bending and shearing resistance

The Bailey truss is used as military river crossing equipment in the early stage, and emphasizes the span requirement under a certain load state. Considering that the moving load (people, vehicles, tanks and the like) is mainly borne during the military river crossing, and in order to avoid the vibration problem of a temporary structure, the Bailey truss adopts a diamond web member system, so that the bending resistance bearing capacity of the Bailey truss is very high, but the shearing resistance bearing capacity of the Bailey truss is very poor, when the Bailey truss is used as a temporary supporting structure, the shearing resistance bearing capacity becomes a controllability factor, and the Bailey truss is generally limited to a structure with smaller unit concentration (the thickness of concrete is not more than 1 m).

2) Pin bolt connection between Bailey trusses and axial bearing capacity of chord member are not matched

According to the design Specification for highway steel structure bridges (JTG D64-2015), the damage forms of pin bolt connection mainly comprise 3 types of tension damage, shearing damage, local pressure bearing damage and the like.

Generally, the bearing capacity of the pin bolt is the minimum value of 420kN, which is only 60% of the axial bearing capacity of the chord member, meaning that the connection bearing capacity between the Bailey trusses is far lower than the self bearing capacity of the Bailey trusses, so that the deflection of the Bailey truss system is greatly different from the classical structure mechanics, and the application of the Bailey truss system in a large-span structure, a cantilever structure and a structure with high load concentration is limited.

3) Bailey truss gives way to structural performance with 'universal performance' requirement

On the other hand, a support structure mainly including a beret truss has an upper limit of load bearing. Taking 321 type Bailey truss which is the absolute dominant truss at present as an example, the height of the truss is 1.5m, the peak value shear bearing capacity and bending bearing capacity are determined, and the connection strength is lower than the strength of a member; on the other hand, the internal force distribution of the supporting system usually has peak-valley regions, the structural specifications of the regions are the same, and the stress state difference is large. The member specifications of the respective cross sections are the same, and the stress state of about 40% of the segment members is made lower than the average state, which limits the material use efficiency.

The existing cantilever support system mainly has 4 types, and the correspondence is:

class 1 (a cantilever support system assembled by a Bailey truss with higher turnover capacity and a large steel pipe system) still needs to occupy extra supporting space (an outermost supporting pile), and the temporary foundation cost in a soft soil area is higher (a large amount of steel pipes need to be input into a steel pipe pile foundation, and the mechanical cost for inserting, beating and removing is high, the construction period is long; an RC concrete foundation needs extra foundation treatment, and the cost is not trivial);

the problems of weak foundation and construction operation space are solved in the category 2 (a cover beam support system assembled by a Bailey truss, a steel truss positioned below the Bailey truss and a large steel pipe system positioned below the steel truss) and the category 3 (a cover beam support system formed by a large-span steel welded rigid frame), but the structural force transfer system is not good (the rod simultaneously bears the action of bending moment and axial force, the stress of the same rod is not uniformly distributed), the steel index is high (the cross section of the rod is too large to meet the stress state of the worst cross section due to the nonuniform stress distribution of the rod, the weight of a single support is not lower than 45 tons), and the economic benefit is poor;

a4 th class cantilever bent cap type bent cap support system is shown in figure 1, and the maximization of economic benefits is realized on a single bent cap support system (on one hand, all rod pieces only bear the action of axial force, and the stress of the rod pieces is uniform; on the other hand, a truss is only provided with 1 on-site bolt splicing seam, and other nodes are connected by welding seams, so that the weight of connecting materials is reduced), but 2 key problems still exist:

1) The integration of the components increases the difficulty of reuse, especially in multiple projects: (1) the single truss is too large in size, so that the short barge transportation difficulty in a construction site is small, but the size requirement of road transportation cannot be met; (2) the single trusses are in a space state and have good bearing capacity and rigidity when bearing vertical action, but the action of uncertain external loads (such as collision, impact and the like) in other directions (non-vertical load directions) in the transportation process causes the single trusses to be damaged and deformed, and the subsequent application functions of the single trusses are influenced;

2) The method is only suitable for the double-cantilever type bent cap and is not suitable for the variable-width section of the urban expressway overhead, namely the four-column continuous bent cap. The structural characteristics of the truss system determine that the truss system is only suitable for a cantilever system in the span direction and cannot be lengthened into a continuous system.

To sum up, research and development a section can be applicable to the construction of the overhead bent cap of the vast majority of express ways in China, possesses great headroom simultaneously, can reduce the influence of construction all ring edge borders to with low costs, the industrialization prefabricated assembled cantilever bent cap support system that has stronger economic nature is the inevitable trend of trade development, also is the requirement of social progress to the building trade.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an assembled cantilever bent cap support. This assembled cantilever bent cap support can be applicable to the construction of the overhead bent cap of the vast majority of express ways in China, possesses great headroom simultaneously, can reduce the influence of construction all ring edge borders to with low costs, the prefabricated assembled cantilever bent cap support system of industrialization that has stronger economic nature.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

an assembled cantilever bent cap support comprises an upper structure, a supporting sand box and a lower structure; the upper structure comprises two truss type girder bodies which are arranged in parallel, and the truss type girder bodies are connected through a support frame; the lower structure comprises a middle fulcrum, the truss type girder body is of an assembled structure and is formed by splicing a plurality of prefabricated module type sections on site along the length extending direction of the truss type girder body;

the prefabricated modular segments comprise a main truss girder and a heightening truss girder; wherein:

two sections of main truss girders are arranged at the middle pivot of the truss girder body, and are correspondingly a first main truss girder and a second main truss girder; the first main truss beam and the second main truss beam are spliced into a whole through a first connecting assembly;

the outer sides of the first main truss girder and the second main truss girder are respectively spliced with the expansion end of the section of the high truss girder through the second connecting assembly, and the section of the high truss girder is the first high truss girder.

Preferably, the prefabricated modular segment further comprises a sub-truss beam;

and the contraction end of the first heightening truss girder is spliced with the auxiliary truss girder into a whole through a third connecting assembly.

Preferably, the lower structure further comprises more than one side supporting point;

a section of main truss girder is uniformly distributed at the position of each edge pivot of the truss girder body, and the main truss girder corresponds to a third main truss girder;

the inner side of the third main truss girder is spliced with a section of heightening truss girder through a second connecting assembly, and the section of heightening truss girder is a second heightening truss girder;

the first and second variable-height truss girders are spliced into a whole through a fourth connecting assembly.

Preferably, the main truss girder comprises a main truss upper chord member, a main truss lower chord member, a main truss straight web member and a main truss diagonal web member, wherein:

the main truss upper chord and the main truss lower chord are arranged in parallel, and the main truss upper chord is positioned above the main truss lower chord;

the number of the main truss diagonal web members is 4, and the main truss diagonal web members correspond to first to fourth main truss diagonal web members; each main truss diagonal web member is arranged between the upper chord member and the lower chord member of the main truss in a W shape;

the number of the main truss straight web members is 4, and the main truss straight web members are correspondingly a first main truss straight web member, a second main truss straight web member and a fourth main truss straight web member; each main truss straight web member is vertically arranged between the main truss upper chord member and the main truss lower chord member;

three gusset plates a which are arranged at intervals are welded and fixed on the upper chord of the main truss, and are correspondingly a first gusset plate a, a second gusset plate a and a third gusset plate a, wherein the first gusset plate a is arranged at the middle position of the upper chord of the main truss, and the second gusset plate a and the third gusset plate a are symmetrically arranged at two sides of the first gusset plate a and are arranged close to the end part of the upper chord of the main truss;

two node plates b which are arranged at intervals are welded and fixed on the lower chord of the main truss, and the two node plates b correspond to a first node plate b and a second node plate b;

the upper ends of the second main truss diagonal web members and the third main truss diagonal web members are respectively fixed with the outer side plate surface of the first gusset plate a, the lower ends of the second main truss diagonal web members are fixed with the outer side plate surface of the first gusset plate b, and the lower ends of the third main truss diagonal web members are fixed with the outer side plate surface of the second gusset plate b; the upper end of the first main truss diagonal web member is fixed with the outer side plate surface of the second gusset plate a, and the lower end of the first main truss diagonal web member is fixed with the outer side plate surface of the first gusset plate b; the upper end of the fourth main truss diagonal web member is fixed with the outer side plate surface of the third gusset plate a, and the lower end of the fourth main truss diagonal web member is fixed with the outer side plate surface of the second gusset plate b;

the upper end of the first main truss straight web member is connected with the main truss upper chord member, and the lower end of the first main truss straight web member is fixed with the inner side plate surface of the second gusset plate b; the upper end of the second main truss straight web member is fixed with the inner side plate surface of the third node plate a, and the lower end of the second main truss straight web member is fixed with the inner side plate surface of the main truss lower chord member; the upper end of the third main truss straight web member is connected with the main truss upper chord member, and the lower end of the third main truss straight web member is fixed with the inner side plate surface of the second gusset plate b; the upper end of the fourth main truss straight web member is fixed with the inner side plate surface of the second gusset plate a, and the lower end of the fourth main truss straight web member is fixed with the inner side plate surface of the main truss lower chord member.

Preferably, the first connecting assembly comprises two connecting plates and a plurality of bolt assemblies; the two connecting plates A are rectangular and are correspondingly a first connecting plate A and a second connecting plate A;

one end of the first connecting plate A is fixed at the end part of the upper chord of the main truss of the first main truss girder through a bolt component, and the other end of the first connecting plate A is fixedly connected with the end part of the upper chord of the main truss of the second main truss girder through a bolt component;

one end of the second connecting plate A is fixed at the end part of the lower chord of the main truss of the first main truss girder through a bolt component, and the other end of the second connecting plate A is fixedly connected with the end part of the upper chord of the main truss of the second main truss girder through a bolt component.

Preferably, the heightening truss girder comprises an upper heightening truss chord, a straight heightening truss web member, a diagonal heightening truss web member and a lower heightening truss chord member;

the upper chord of the variable-height truss is horizontally arranged and is formed by splicing a first variable-height truss upper chord and a second variable-height truss upper chord;

the lower chord of the heightening truss is positioned below the upper chord of the heightening truss and is arranged obliquely to the upper chord of the heightening truss;

the straight web members and the inclined web members of the heightening truss are uniformly arranged between the upper chord member and the lower chord member of the heightening truss, the straight web members of the heightening truss are vertical, and the inclined web members of the heightening truss are inclined; the number of the heightening truss straight web members is three, and the heightening truss straight web members are correspondingly a first heightening truss straight web member, a second heightening truss straight web member and a third heightening truss straight web member; the number of the heightening truss diagonal web members is three, and the heightening truss diagonal web members are correspondingly a first heightening truss diagonal web member, a second heightening truss diagonal web member and a third heightening truss diagonal web member;

two gusset plates c are arranged on the upper chord of the heightening truss and correspond to a first gusset plate c and a second gusset plate c,

two gusset plates d are arranged on the lower chord of the high-rise truss and correspond to a first gusset plate d and a second gusset plate d;

the upper end of the first heightening truss straight web member is fixed with a first gusset plate c arranged at the end part of the upper chord member of the heightening truss, and the lower end of the first heightening truss straight web member is fixed with the descending end of the lower chord member of the heightening truss; the upper end of the straight web member of the second heightening truss is connected with the middle part of the upper chord member of the second heightening truss, and the lower end of the straight web member of the second heightening truss is fixed with a second gusset plate d arranged at the position corresponding to the lower chord member of the heightening truss; the upper end of the third heightening truss straight web member is fixed with the other end of the upper chord member of the heightening truss, and the lower end of the third heightening truss straight web member is fixed with a first gusset plate d arranged at the rising end of the lower chord member of the heightening truss;

the upper end of the first heightening truss diagonal web member is fixed with the outer side plate surface of the first gusset plate c, and the lower end of the first heightening truss diagonal web member is fixed with the inner side plate surface of the lower chord member of the heightening truss; the upper end of the diagonal web member of the second heightening truss is fixed with the outer side plate surface of a second gusset plate c, the lower end of the diagonal web member of the second heightening truss is fixed with the outer side plate surface of a second gusset plate d, and the second gusset plate c is arranged at the splicing position of the upper chord members of the first heightening truss and the second heightening truss; the upper end of the third heightening truss diagonal web member is fixed with the outer side plate surface of the second gusset plate c, and the lower end is fixed with the outer side plate surface of the first gusset plate d.

Preferably, the second connecting assembly comprises two connecting plates B, namely a first connecting plate B, a second connecting plate B and a plurality of bolt assemblies;

the first connecting plate B is a straight plate, one end of the first connecting plate B is fixedly connected with the upper chord of the heightening truss of the first heightening truss girder through a bolt assembly, and the other end of the first connecting plate B is fixedly connected with the upper chord of the main truss girder through a bolt assembly;

the second connecting plate B is a bending plate, one end of the second connecting plate B is fixedly connected with the variable-height truss lower chord of the first variable-height truss girder through a bolt assembly, and the other end of the second connecting plate B is fixedly connected with the main truss lower chord of the main truss girder through a bolt assembly.

Preferably, the secondary truss girder comprises a secondary truss upper chord, a secondary truss lower chord, a secondary truss straight web member and a secondary truss diagonal web member, wherein:

the upper chord member and the lower chord member of the auxiliary truss are horizontally arranged, the straight web member and the inclined web member of the auxiliary truss are arranged between the upper chord member and the lower chord member of the auxiliary truss, the straight web member of the auxiliary truss is vertical, and the inclined web member of the auxiliary truss is inclined;

the number of the first auxiliary truss straight web members is three, and the first auxiliary truss straight web members, the second auxiliary truss straight web members and the third auxiliary truss straight web members correspond to each other;

the number of the secondary truss diagonal web members is four, and the secondary truss diagonal web members are correspondingly a first secondary truss diagonal web member to a fourth secondary truss diagonal web member;

the first auxiliary truss straight web member is arranged in the middle of the auxiliary truss girder, and the second and third auxiliary truss straight web members are arranged on two sides of the auxiliary truss girder;

the first auxiliary truss diagonal web members and the third auxiliary truss diagonal web members are symmetrically arranged on two sides of the first auxiliary truss straight web members, the second auxiliary truss diagonal web members and the fourth auxiliary truss diagonal web members are symmetrically arranged, the second auxiliary truss diagonal web members are arranged on the outer sides of the first auxiliary truss diagonal web members, and the fourth auxiliary truss diagonal web members are arranged on the outer sides of the third auxiliary truss diagonal web members; and the first to fourth secondary truss diagonal web members are integrally arranged in an M shape.

Preferably, the third connecting assembly comprises an ear plate and a pin joint; the number of the lug plates and the number of the pin bolt joints are two;

the two ear plates are respectively arranged at the end parts of the upper chord member and the lower chord member of the auxiliary truss, the two pin bolt joints are arranged at the contraction end of the heightening truss beam and fixed at the upper end and the lower end of the straight web member of the third heightening truss, or the two ear plates are arranged at the contraction end of the heightening truss beam and respectively arranged at the end parts of the upper chord member and the lower chord member of the heightening truss, and the pin bolt joints are arranged at the end part of the auxiliary truss beam and respectively arranged at the upper end and the lower end of the straight web member of the third auxiliary truss.

The invention also aims to provide a construction method of the assembled cantilever bent cap support, which comprises the following steps:

a. when the bearing platform is constructed, a fixed iron plate is pre-embedded according to the size of the bracket and the position of the cross beam;

b. after the construction of the bearing platform is finished, after the concrete reaches the designed strength, hoisting and installing the 60a I-shaped steel beam;

c. according to the actual height requirement of the support, installing the steel pipe piles and the support frames section by section on the ground, hoisting the whole section, and installing the flange bolts section by section;

d. measuring the pile top elevation of a section of steel pipe pile at the top, calculating the adjusting height of a supporting sand box, and mounting the supporting sand box;

c. the upper structure of the support is integrally installed on the ground, the main truss girder, the heightening truss girder, the auxiliary truss girder and the support frame are completely installed and then hoisted to the position of a supporting point of a supporting sand box, and the installation inspection and acceptance work of the trusses is well carried out before hoisting;

d. confirming whether the position and the elevation of the truss meet the design construction requirements again after the truss is installed;

e. installing a cover beam I-shaped steel bottom die beam on the upper structure of the bracket, and fixing an I-shaped steel flange plate and an upper chord reinforced iron plate of the upper structure by using a U-shaped clamp;

f. mounting a cover beam bottom die on the I-shaped steel cross beam, binding cover beam reinforcing steel bars, pouring cover beam concrete, and strictly monitoring the support in the cover beam construction process, wherein the deformation of the support cannot exceed 5mm;

g. after the bent cap is maintained to the designed strength, the elevation of the support is reduced by using the supporting sand box, so that the upper structure is separated from the bottom of the bent cap, and the bottom die system is disassembled;

h. the upper structure is hung below the cover beam by using a manual hoist, the truss-type beam body and the support frame are lifted out from one side of the cover beam together after the splicing bolts between the truss-type beam bodies are removed, and the support frame is removed after the truss-type beam bodies and the support frame are lifted to the ground; the truss girder body hoisting sequence is that firstly, the auxiliary truss girder is hoisted, then, the high truss girder is hoisted, and then, the main truss girder is hoisted;

i. after the truss type beam body is dismantled, firstly dismantling the supporting sand boxes from top to bottom, then removing the flange connection between the steel pipe piles, and hoisting the steel pipe pile system in a segmented and integral manner;

j. and finally, cutting off the connection between the 60a I-steel and the pre-buried iron plate of the bearing platform to finish the dismantling of all components of the support.

Based on the technical purpose, compared with the prior art, the invention has the following advantages:

the truss girder body of the upper structure of the single support system is formed by freely combining and splicing different modular sections to form various structural specifications, and the construction requirements of bent caps with different lengths and sizes can be met. The modular sections are mainly divided into a main truss girder, a variable height truss girder and two specifications of sub truss girders (the two specifications of the sub truss girders are different only in pin joint at the end part).

Only the main truss beams are provided with supporting points, so that a beam body formed by splicing two main trusses is used as a basic beam body in various working conditions, and an elevated truss beam, an auxiliary truss beam and the like are spliced on the basic beam body formed by splicing the two main trusses according to the length structure of the capping beam so as to meet the construction requirements.

Therefore, the invention has the following advantages:

1) Better versatility: the single component needs to adopt a plane structure similar to a Bailey truss instead of a three-dimensional structure, and meanwhile, the assembled component has good specification modulus and can meet the requirements of various capping beam sizes;

2) Excellent load bearing capacity and stiffness: the bracket system has enough bearing capacity and rigidity, meets the requirements of capping beams with various specifications and weights, and has additional rod piece reinforcing measures to adapt to the requirements of individual large-volume concrete capping beams;

3) Reliable, boundary connection measures: the connection between the main body components needs to be matched with the main body components and convenient and fast installation;

4) Excellent economic benefit: the support system has light self weight, low manufacturing cost and good economy.

In addition, the stent system also needs to have the following functions:

1) The lower on-site assembly requirement is as follows: the labor required for one-time installation and removal is not more than 6 persons, the number of the 70-ton automobile crane is not more than 2, the one-time installation time is not more than 8 hours, and the one-time removal and transfer time is not more than 8 hours;

2) The durability is better: ensuring the turnover capacity of more than 100 times of cyclic use.

Drawings

FIG. 1 is a schematic structural view of a prior art outrigger type bent cap support system;

fig. 2 is a schematic structural view of a first fabricated cantilever capping beam support (temporary support for a standard-section double cantilever capping beam) according to the present invention;

fig. 3 is a schematic structural view of a second fabricated cantilever capping beam support (temporary support for a double cantilever capping beam for a ramp section) according to the present invention;

FIG. 4 is a schematic structural view of a third fabricated cantilevered capping beam bracket (temporary support for a three pivot capping system) according to the present invention;

FIG. 5 is a schematic structural view of a fourth fabricated cantilevered capping beam bracket (temporary support for a four-pivot capping beam system) according to the present invention;

fig. 6 is a schematic structural view of a sub-truss girder in the fabricated cantilever capping beam bracket according to the present invention;

fig. 7 is a schematic structural view of an elevated truss girder in the fabricated cantilever capping beam support according to the present invention;

fig. 8 is a schematic structural view of a main truss girder in the fabricated cantilever capping beam bracket according to the present invention;

in FIGS. 2-8: 1-auxiliary truss girder; 2-a height-variable truss girder; 3-a main truss beam;

101-a first secondary truss beam; 102-a second sub-lattice beam; 103-a third secondary truss girder;

201-a first elevated truss beam; 202-second high-rise truss girder; 203-a third elevated truss beam; 204-fourth high truss girder;

301-a first main truss beam; 302-a second main truss girder; 303-a third main truss beam; 304-fourth main truss beam.

1-1, upper chords of the auxiliary trusses; 1-2, an auxiliary truss lower chord; 1-3, an auxiliary truss straight web member; 1-4, a first secondary truss diagonal web member; 1-5, a second secondary truss diagonal web member; 1-6, ear plates; 1-7, a pin joint;

2-1, a first upper chord of the high-rise truss; 2-2, a second upper chord of the high truss; 2-3, a first connecting plate B; 2-4, a first heightening truss straight web member; 2-5, a second connecting plate B;2-6, a first heightening truss diagonal web member; 2-7, a second heightening truss straight web member; 2-8, a second heightening truss diagonal web member; 2-9, a third heightening truss diagonal web member; 2-10, connecting joints of a third high-rise truss; 2-11, third high-rise truss straight web members;

3-1, upper chords of the main trusses; 3-2, a first main truss web member; 3-3, connecting plate A;3-4, a first main truss diagonal web member; 3-5, main truss lower chord; 3-6, a second main truss diagonal web member; 3-7, connecting a second main truss; 3-8, and a second main truss straight web member.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention. The relative arrangement of the components and steps, expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values.

The rack of the present invention, as shown in fig. 2-8, is largely divided into an upper structure, a cushioned flask, and a lower structure.

The upper structure of a single support is composed of two truss type beam bodies, and the two beam bodies are connected and fixed through a support frame to ensure the overall stability of the support body.

In order to meet the support assembly type construction, the single truss girder body is formed by freely combining and assembling the module type sections, and the module type sections are mainly divided into a main truss girder (shown in an attached figure 8), a variable height truss girder (shown in an attached figure 7) and an auxiliary truss girder (shown in an attached figure 6). The length specification of the single-piece main truss girder is set to be 5.0m, the length specification of the single-piece high truss girder is set to be 3.75m, and the length specification of the single-piece auxiliary truss girder is set to be 5.0m.

Note: the maximum beam body section is 5.0m, and the beam body is of a sheet structure and convenient to transport.

The main truss girder and the main truss girder can be assembled respectively, the main truss girder and the auxiliary truss girder can be assembled through the variable height truss, and the auxiliary truss girder can be assembled respectively. Through assembling and combining the plurality of truss girders, the construction requirements of capping girders with different lengths and sizes and various pier stud forms can be met.

The members constituting the truss girder include upper and lower chords, straight web members and diagonal web members. The single rod piece is formed by symmetrically arranging two channel steel, the chord member is in a shape of [ "(limb back opposite), and the straight web member is in a shape of [ ]" (limb back opposite). The diagonal web members are in the form of "[" (limb back facing) in the main and the heightening truss girders and in the form of "[ ]" (limb back facing) in the sub-truss girders.

Note: the web members in the form of [ ] "(limb back-to-back) are welded at the flange ends to form a closed cylindrical structure which has great stability both inside and outside the plane.

The upper chord and the lower chord of the single-piece main truss girder adopt 25# channel steel, and the center distance between the upper chord and the lower chord is 3.0m. And a strong rectangular frame structure is formed after the web members are additionally arranged, so that the load effect of the standard section of the bent cap can be resisted. Bolt holes with the diameter of 33.0mm are formed in the two ends of the chord member, and the bolt holes are matched with 8.8-grade M30 bolts and used for assembling and splicing the truss girders.

The single-piece main truss girder web member consists of 4 straight web members and 4 inclined web members, the straight web members adopt No. 10 channel steel, two ends of the truss are respectively provided with 1 straight web member, and the middle 2 straight web members are respectively arranged at the 1/4 and 3/4 positions of the chord length. The 4 oblique web members are 20# channel steel and are arranged at two sides of the 2 straight web members in the middle in a W shape. The crossing position of the oblique web member and the chord member is welded and fixed by adopting a 2cm thick iron plate, the crossing position of the web member and the lower chord member is used as a node to be connected with a supporting point of a lower structure, the iron plate at the crossing position is welded and stiffened by adopting a 2cm thick rib plate, and the 4cm thick iron plate is additionally arranged below the node to be welded with the node plate and the stiffening plate for the supporting point to be stressed for use. The member arrangement and node treatment are carried out in this way, so that not only can the bending action of the upper chord be effectively reduced, but also the load can be effectively transmitted to the lower supporting structure.

The upper chord member and the lower chord member of the single-piece auxiliary truss girder adopt 14# channel steel, the center distance between the upper chord member and the lower chord member is 1.5m, and a rectangular frame structure is formed after the web members are erected, so that the load effect of the cover girder cantilever end variable section can be resisted. The chord member both ends set up the cotter joint, and the cotter joint who splices the end with excessive truss girder is "male" form, and the other end sets up female head or male (divide into two kinds of vice truss girders, these two kinds of vice truss girders only have one end cotter joint and be female head or positive one kind difference, these two kinds of truss girders all can with uprising truss girder bolt connection).

The web member of the single-piece auxiliary truss girder consists of 3 straight web members and 4 diagonal web members, the straight web members and the diagonal web members are all 10# channel steel, two ends of the truss are respectively provided with 1 straight web member, and the other 1 straight web member is arranged at the 1/2 position of the length of the chord member. 4. The root diagonal web members are arranged on two sides of the middle straight web member in an M shape and are in stress forms of 5 nodes of the upper chord member and 3 nodes of the lower chord member. The crossing position of the web member and the chord member is fixed by welding, and the length of the web member extending into the chord member is consistent with the height of the chord member.

The center distance between the two ends of the upper chord and the lower chord of the single-piece variable-height truss girder is respectively set to be 1.5m and 3.0m. A single channel steel of the upper chord is welded and connected through a switching steel plate with the thickness of 2cm by a 14# channel steel and a 25# channel steel, the node steel plate is arranged at the back of the channel steel, one third section close to the end of 1.5m adopts the 14# channel steel, and the other third section close to the end of 3.0m of the upper chord adopts the 25# channel steel. The outer side of the lower end of the adapter plate is provided with a node steel plate with the thickness of 2cm, and the adapter plate is welded and fixed with the node plate. Evenly set up 6 diameter 2 cm's plug weld hole on this gusset plate, the welding height in plug weld hole is a little more than gusset plate thickness, is polishing to flushing with the gusset plate surface.

The lower chord of the height-variable truss girder adopts 20# channel steel, is of a trapezoidal frame structure after being provided with the web members, and can connect and assemble the main truss girder and the spoke truss girder in a geometric form while resisting the load of the variable section of the capping girder.

The single-chip heightening truss girder web member is composed of 3 straight web members and 3 inclined web members, the straight web members adopt 10# channel steel, two ends of the truss are respectively provided with 1 straight web member, and the other 1 straight web member is arranged at the 1/3 part of the length of the chord member and is close to the position of the long straight web member. And the 3 diagonal web members adopt 14# channel steel for 1 diagonal web member close to the end of 1.5m, and adopt 20# channel steel for 2 diagonal web members close to the end of 3.0m. 3 oblique web members arrange in the frame with "N style of calligraphy", form 4 nodes of upper chord, the atress form of 3 nodes of lower chord. And the intersecting positions of the diagonal web members and the chords are welded and fixed by adopting an iron plate with the thickness of 2 cm.

22a I-steel is placed at a node above the truss girder to serve as a cross beam of the bottom die of the cover girder, the I-steel is arranged along the bridge direction and coincides with the intersection point position of the web member and the upper chord member of the truss girder, and the I-steel and the iron plate are fixed by a steel U-shaped clamp, so that the bottom die system has the assembling performance, and the stability of the I-steel is effectively guaranteed.

The two truss beams forming the support structure are fixedly connected in a support frame mode, the support frame is mainly made of 10# channel steel and 2cm iron plates, and the components are mainly divided into transverse rods, vertical rods, inclined rods, small transverse rods and connecting plates.

The cross bar of the support frame is formed by symmetrically arranging 2 channel steels in a mode, and 1 bolt hole with the diameter of 22.0mm is arranged at the end part of the cross bar. And a connecting plate with the thickness of 2.0cm is arranged near the end bolt and is welded with 2 transverse rod channel steel. A gusset plate with the thickness of 2.0cm is arranged in the middle of the cross rod and is welded with 2 cross rod channel steel. The vertical rod of the supporting frame is also symmetrically arranged in the form of a beam by 2 channel steels and is firmly welded with the connecting plate. A gusset plate with the thickness of 2.0cm is arranged in the middle of the vertical rod and is welded with 2 vertical rod channel steels. The diagonal rods are symmetrically arranged in the form of 4 channel steels and are firmly welded with the node plates on the transverse rods and the vertical rods respectively. The small cross rods are also symmetrically arranged in the form of 2 channel steels, and the connecting plates in the middle of the vertical rods are firmly welded.

And welding a connecting iron plate with a bolt hole at the flange end of the truss girder straight web member joint at the connecting position of the support frame, wherein the connecting iron plate is vertical to the web plate of the straight web member and is additionally welded with a triangular stiffening iron plate.

The support frame only provides the lateral stabilization of the upper structure of the support and does not serve as a transmission structure for the main load.

The member size of the support frame matches the height of the corresponding main and auxiliary truss girders. The length of the support frame is set to be 2.66m, and the construction requirements of most of column sizes and cover beam width sizes can be met.

The single support system has 4 support sand boxes, and the support sand boxes are arranged at the supporting point positions between the upper structure and the lower structure (below the main truss beam supporting iron plates). The sand box is connected with the supporting points of the truss girder by bolts and connected with the lower structure by flanges, and the supporting sand box can play the roles of adjusting the elevation of the support and unloading the support.

The lower structure of the single support system is composed of 4 steel pipe piles and 2 steel cross beams, and longitudinal and transverse support frames are arranged between the steel pipe piles for connection and fixation, so that the overall stability of the lower structure is ensured.

The steel pipe piles are also in an assembled structure, the steel pipe piles are connected through flanges, the set lengths of the steel pipe piles are 5 specifications including 6.0m,5.0m,4.0m,3.0m and 0.5m, and the steel pipe piles can be correspondingly combined to meet the construction requirements of engineering sites.

2 pieces of 60a I-steel are arranged at the bottom of the steel pipe pile, and 2cm back iron plates are attached to the I-steel at the supporting point of the steel pipe pile and can be connected with the first section of the steel pipe pile at the bottom through bolts. The additional iron plate and the I-shaped steel lower wing plate are provided with stiffening steel plates.

The structural form of the support frame between the steel pipe piles is the same as that of the truss girder support frame, the height specification of the transverse support frame is set to be 3.78m and 2.78m, the height specification of the longitudinal support frame is set to be 1.78m and 2.78m, the support frames with different specifications are combined for use, and the connecting requirements of the steel pipe pile columns with different heights can be met.

In summary, the modular construction process ensures that the set of stent systems has good versatility and meets the desired target requirements.

1.1 Combined Split mounting function

Only the main truss beams are provided with supporting points, so that a beam body formed by splicing two main trusses is used as a basic beam body in various working conditions, and an elevated truss beam, an auxiliary truss beam and the like are spliced on the basic beam body formed by splicing the two main trusses according to the length structure of the capping beam so as to meet the construction requirement.

1) Double-cantilever cover beam with standard section

For the standard-section double-cantilever capping beam, as shown in fig. 2, the upper structural beam body of the bracket is spliced by sections of 'auxiliary truss beam + variable-height truss beam + main truss beam + variable-height truss beam + auxiliary truss beam'.

2) Double-cantilever cover beam of ramp section

For the double-cantilever capping beam at the ramp section, as shown in fig. 3, the sections of the "high truss beam + main truss beam + high truss beam" are selected and spliced for the structural beam body at the upper part of the bracket.

Note: when the length of the ramp capping beam is not more than 8.5m, the sections of the main truss beam and the main truss beam can be spliced to be used as the upper structure of the bracket.

3) Three-pivot capping beam system

For the three-pivot capping beam system, as shown in fig. 4, the upper structural beam body of the bracket is spliced by sections of "auxiliary truss beam + heightening truss beam + main truss beam + heightening truss beam + auxiliary truss beam + heightening truss beam + main truss beam".

Note: the actual number of two "sub-truss girder" sections of the continuous section is selected according to the specific span.

4) Four-pivot bent cap system

For the four-pivot capping beam system, as shown in fig. 5, the section "main truss beam + heightening truss beam + sub truss beam + heightening truss beam + main truss beam + heightening truss beam + sub truss beam + heightening truss beam + main truss beam" is selected for the structural beam body on the upper portion of the bracket for splicing.

1.2 diversified node assembling system

The design of the connection between the units follows 2 principles: (1) the bearing capacity of the splicing joint is matched with the axial bearing capacity of the chord member; (2) the installation and the disassembly of the splicing joint are convenient and quick.

(1) Pin joint

The 321-type Bailey sheet which is widely applied at present is combined, and the connection between the plane trusses adopts a pin bolt joint, so that the convenience in installation and removal is remarkable. Meanwhile, the bearing capacity of the pin-bolt joint is obviously 'ceiling' due to the construction requirement, the size of the lug plate of the pin-bolt joint is limited by the specification of the connecting section steel, and the maximum matching pin-bolt joint lug plate of 10# channel steel and 20# channel steel is constructed as shown in figure 6.

The bearing capacity was evaluated based on the maximum gauge pin lug, as shown in table 1.

TABLE 1 evaluation table for bearing capacity of lug plates with pin bolt structures of different specifications

Note: when the specifications of the chords at the two ends of the splicing joint are different, the smaller chords are used as the reference.

As can be seen from table 1, the pin-and-bolt connection can still match with the 14# channel, but cannot be applied to the 20# channel. Therefore, it is used as a connection between a 1.5m truss (sub-truss girder) and a high truss (high-truss girder).

(2) Joint assembling system of' connecting plate + bolt

When the chord specification exceeds 14# channel steel, the bearing capacity of the pin bolt joint slides down remarkably, and the bearing capacity of the chord of 20# channel steel is higher than that of the pin bolt joint by nearly 40%, so that the 3.0m truss is connected with the heightening truss without the pin bolt connection, and a connecting plate and bolt structure is adopted.

The number of bolts at the connecting joints is set according to the strength of the connected rods, namely the total strength of the bolts and the strength of the connecting plates are greater than the strength of the connected rods. Consequently for satisfying quick assembly disassembly's requirement, after bolt quantity satisfies the intensity requirement again, need improve bolt intensity and diameter and reach the total number that reduces the bolt for the support ann tears the progress open.

1) Upper chord

Go up the chord, it all adopts the doublet 25# channel-section steel with 3.0m truss (main truss roof beam) to uprise the truss, and chord member axial bearing capacity is:

N＝f _y ·A＝190MPa×3490mm ² ＝663.1kN

the splicing region adopts 8.8-grade common bolts, and the shear strength design value f of a single bolt is according to the design Specification of Highway Steel Structure bridges (JTG D64-2015) _vd ^b For 280MPa, select 4 pieces of M30, the bolt is two rows, every row two to be arranged, and single chord member sets up 1 shear plane, so the bolt shearing resistance bearing capacity does:

choose t =25mm connecting plate for use, its gusset plate pressure-bearing capacity is:

the tensile bearing capacity of the connecting plate is as follows:

N＝f _y ·(A ₀ -n·d·t _w )＝190MPa×3500mm ² ＝665kN

therefore, 4M 30 8.8-grade bolts are adopted for the upper chord to meet the bearing capacity requirement of the node.

Similarly, 4M 30 8-grade bolts are adopted between the 3.0M truss (main truss girder) and the 25# channel steel of the upper chord of the 3.0M truss (main truss girder).

2) Lower chord

The lower chord of the high truss girder is formed by double-spliced 20# channel steel, the 3.0m truss (main truss girder) is formed by double-spliced 25# channel steel, and the bearing capacity of the node is controlled according to a small component. The axial bearing capacity of the double-spliced 20# channel steel is as follows:

N＝f _y ·A＝190MPa×2880mm ² ＝574.2kN

the variable height truss and the 3.0m truss lower chord have a certain included angle, when the connecting plate and the bolt are connected, the core problem is that the included angle also exists in the connecting plate, and the node design follows the following 2-point principle:

a) The center lines of the chord members of the high truss and the 3.0m truss are positioned at the same height at the splicing seams to provide a foundation for arranging a corner connecting plate, namely, the influence of the additional bending moment of the node on the node plate is avoided;

note: if the top edge alignment or the bottom edge alignment is adopted, the axis of the high chord member and the axis of the main truss chord member intersect at the center of the connecting node, and a large additional bending moment is generated. The additional bending moment can enable a connecting plate of the node to bear large concentrated stress, so that the node plate is unstable, and buckling failure is caused.

B) The included angle of the connecting plate is consistent with the angle of the chord connected with the connecting plate, and the connecting plate is arranged in a straight manner, so that the axial force of the lower chord of the variable-height truss is transmitted to the main truss.

The splicing region adopts 8.8-grade common bolts, and the shear strength design value f of a single bolt is according to the design Specification of Highway Steel Structure bridges (JTG D64-2015) _vd ^b For 280MPa, choose 3 pieces of M30, single chord member sets up 1 shear plane, so the bolt shear resistance bearing capacity does:

choose t =30mm connecting plate for use, its gusset plate pressure-bearing capacity is:

the tensile bearing capacity of the connecting plate is as follows:

N＝f _y ·(A ₀ -n·d·t _w )＝190MPa×3600mm ² ＝684kN

therefore, 3M 30 8-grade bolts are adopted between the lower chord high truss and the main truss to meet the bearing capacity requirement of the node.

The arrangement of bolt holes on the connecting plate with respect to the spacing requirement meets the requirements of design Specifications for bridges with steel highway structures (JTG D64-2015): bolt center containerThe minimum allowable distance is 3d ₀ (d ₀ Bolt hole diameter); the minimum distance from the center of the bolt to the edge is 1.5d ₀ (d ₀ Bolt hole diameter). Two bolt holes are formed in the connecting plate in the height direction of the connecting plate, and the height of the connecting plate is (1.5 +3+ 1.5) d ₀ =198mm. And the height of the connecting plate meets the construction requirements, namely the height of the connecting plate is not more than the length of the straight section at the inner side of the channel steel web, the length of the straight section at the inner side of the 20# channel steel web is 156mm, and the height of the connecting plate is 150mm on the premise of ensuring the machining error.

Note: the inboard straight section length of channel-section steel web = the web height-2 x (edge of a wing thick + circular arc section), and the connecting plate height surpasss the inboard straight section length of channel-section steel web and can cause the connecting plate can't take place effective contact with the channel-section steel web, can make the connecting plate seriously warp and then lead to bolted connection inefficacy at the bolt operation process.

Therefore, the maximum height of the connecting plate is 150mm, the bolt holes are required to be arranged in a single mode in the height direction of the connecting plate, and the overall bolt holes are arranged in a delta mode.

In conclusion, the lower chord high-rise truss and the main truss are arranged in a delta form to meet the requirement of section construction.

The connection between the 3.0M truss (main truss girder) and the lower chord 25# channel steel of the 3.0M truss (main truss girder) is the same as the upper chord 25# channel steel, and the bearing capacity requirement can be met by adopting 4M 30 8.8-grade bolts.

1.3 node splice area settings

In addition to considering the bearing capacity of the connecting member, the node area should also pay attention to the arrangement of the splicing area.

The chord members between the straight web members on the two sides of the joint bear the action of larger bending moment, the peak value is positioned at the intersection point of the chord members and the straight web members, the absolute value of the bending moment is obviously improved along with the increase of the distance between the straight web members, and the maximum stress value of the whole chord member is correspondingly improved, so that the section becomes the most unfavorable section. In order to satisfy the stress state of the worst cross section, the cross section size of the rod piece needs to be increased, and the weight of a single bracket needs to be increased greatly. Therefore, the distance between the straight web members on the two sides of the node is reduced.

(1) 'connecting plate + bolt' joint

The joints of the connecting plates and the bolts are arranged at the splicing part of the main truss girder and the splicing part of the main truss girder and the heightening truss girder. The edge of the straight web member at the splicing position of the joint of the connecting plate and the bolt is 2cm away from the end part of the chord member, and the straight web member and the chord member are used as welding and fixing areas of the straight web member and the chord member, so that the length of a cantilever of the chord member outside the intersection point of the web member is reduced. In order to avoid the bolt holes from welding areas at the joints of the straight web members and the chords, the bolt holes are arranged outside the axis of the straight web members.

(2) Pin bolt joint

The pin bolt joint is arranged at the splicing position of the auxiliary truss girder and the splicing position of the auxiliary truss girder and the heightening truss girder. The edge of the straight web member at the splicing position of the pin bolt joint is 5cm away from the end part of the chord member and is used as a welding and fixing area of the pin bolt male head and the chord member.

Two female head parts of the pin bolt are respectively welded and fixed with the inner sides (the channel steel flange overhanging sides) of two channel steel webs of the chord member. The pin bolt female head and the chord member channel steel are fixed without colliding with other rod pieces, and the pin bolt female head and the chord member channel steel can be provided with enough welding length to meet the strength requirement.

The male head part of the pin bolt is welded and fixed with the outer sides of two channel steel webs of the chord member respectively (the male head is fixed between two channel steels of the chord member), and the distance between the male head and the two channel steels of the chord member is constant. The length that chord member channel-section steel was encorbelmented the end and can be with the pin bolt male joint welded fastening is 5cm. The pin bolt male head and chord member channel steel contact area, evenly set up the plug welding hole of three 1cm diameter at the channel steel web that this region corresponds. The welding height of the plug welding hole is slightly higher than the thickness of the web plate of the channel steel, and the plug welding hole is polished to be flush with the web plate of the channel steel. The plug welding hole can enhance the connection strength of the pin bolt male head and the chord member channel steel, and meets the strength requirement of joint splicing.

1.4 Bar Reinforcement in the node area

The reinforced design of the node area mainly comprises 2 aspects: 1) The straight web member is embedded between the two channel steels of the chord member; 2) And the diagonal web members of the variable height truss girder and the main truss girder are welded and fixed with the chord members through the gusset plates.

Straight web member embedded arrangement

The straight web member is embedded between the two channel steels of the chord member and is welded and fixed. Two channel-section steels of chord member and straight web member welded fastening make the chord member link root channel-section steel and connect into whole, reduce in a large number and use the batten plate to connect two channel-section steels of chord member. And the straight web members and the chord members are embedded and welded to reinforce the truss system.

For the heightening truss girder and the main truss girder, the straight web members are embedded in the chord members, and the inclined web members and the straight web members can be arranged in a staggered manner. The oblique web members are arranged on the outer sides of the straight web members, the whole node is compact in structure, and the load transfer path is obvious. The oblique web members and the straight web members are arranged in a staggered mode, so that the distance between the end portions of the oblique web members and the intersection points can be obviously reduced, and the rigidity of the gusset plate is enhanced.

Setting gusset plate

Oblique web members of the heightening truss girder and the main truss girder are welded and fixed with the chord members through node plates with the thickness of 2 cm. The gusset plate welds in the chord member channel-section steel edge of a wing, and the gusset plate outward flange flushes in the channel-section steel web outside. The welding length of the diagonal web members can be controlled by adjusting the size of the gusset plate, and the stability of the connecting node is improved. The oblique web members are connected with the chord members through the gusset plates, so that fatigue resistance of the connecting joints can be enhanced, and the using times of the truss are increased.

2 method of implementation

b. after the construction of the bearing platform is finished, after the concrete reaches the designed strength, the 60a I-shaped steel beam is hung and installed;

d. measuring the pile top elevation of a section of steel pipe pile at the top, calculating the height of a support sand box for adjusting, and mounting the sand box;

c. integrally installing the truss girder on the ground, completely installing the main truss girder, the heightening truss girder, the auxiliary truss girder and the support frame, hoisting the main truss girder, the heightening truss girder, the auxiliary truss girder and the support frame to the position of a supporting point of a supporting sand box, and performing the operation of checking and accepting the truss installation before hoisting;

e. and installing a bent cap I-shaped steel bottom die beam on the truss girder, and fixing the I-shaped steel flange plate and the truss girder upper chord reinforced iron plate by using a U-shaped clamp.

f. Installing a cover beam bottom die on the I-shaped steel cross beam, binding cover beam steel bars, pouring cover beam concrete, and strictly monitoring the support in the cover beam construction process, wherein the support deformation cannot exceed 5mm.

g. After the bent cap is maintained to the designed strength, the elevation of the support is reduced by using the support sand box, so that the truss girder is separated from the bottom of the bent cap, and the bottom die system is disassembled;

h. the truss is suspended on the cover beam by using the hand hoist and is placed downwards, splicing bolts between the truss beams are removed, the truss beams and the support frame are lifted out from one side of the cover beam, and the support frame is removed after the truss beams and the support frame are lifted to the ground. The truss girder hoisting sequence is that firstly the auxiliary truss girder is hoisted, then the high truss girder is hoisted, and then the main truss girder is hoisted.

i. And after the truss girder is completely dismantled, firstly dismantling the supporting sand box from top to bottom, then removing the flange connection between the steel pipe piles, and hoisting the steel pipe pile system in a segmented and integral manner.

j. And finally, cutting off the connection between the 60a I-steel and the bearing platform embedded iron plate to finish the dismounting of all the components of the bracket.

Claims

1. An assembled cantilever bent cap support comprises an upper structure, a supporting sand box and a lower structure; the upper structure comprises two truss type girder bodies which are arranged in parallel, and the truss type girder bodies are connected through a support frame; the lower structure comprises a middle fulcrum and is characterized in that the truss type girder body is of an assembled structure and is formed by splicing a plurality of prefabricated module sections on site along the length extending direction of the truss type girder body;

the prefabricated modular segment comprises a main truss girder and a variable height truss girder; wherein:

2. The fabricated cantilever capping beam support of claim 1, wherein the prefabricated modular segment further comprises a sub-truss beam;

3. The fabricated cantilever capping beam bracket of claim 2, wherein the substructure further comprises more than one side support point;

a section of main truss girder is uniformly distributed at the position of each side pivot of the truss girder body, and the main truss girder is a third main truss girder correspondingly;

4. The fabricated cantilever capping beam support of claim 3, wherein the main truss beam comprises a main truss upper chord, a main truss lower chord, a main truss straight web and a main truss diagonal web, wherein:

three node plates a which are arranged at intervals are welded and fixed on the upper chord of the main truss and correspond to a first node plate a, a second node plate a and a third node plate a, the first node plate a is arranged at the middle position of the upper chord of the main truss, and the second node plate a and the third node plate a are symmetrically arranged at two sides of the first node plate a and are arranged close to the end part of the upper chord of the main truss;

5. The fabricated cantilever capping beam bracket of claim 4, wherein the first connection assembly comprises two connection plates and a plurality of bolt assemblies; the two connecting plates A are rectangular and are correspondingly a first connecting plate A and a second connecting plate A;

6. The fabricated cantilever capping beam bracket of claim 5 wherein the elevated truss beam includes an elevated truss upper chord, an elevated truss straight web, an elevated truss diagonal web and an elevated truss lower chord;

the upper chord of the high-height truss is horizontally arranged and is formed by splicing a first high-height truss upper chord and a second high-height truss upper chord;

two gusset plates c are arranged on the upper chord of the high truss and correspond to a first gusset plate c and a second gusset plate c,

the upper end of the first heightening truss diagonal web member is fixed with the outer side plate surface of the first gusset plate c, and the lower end of the first heightening truss diagonal web member is fixed with the inner side plate surface of the lower chord member of the heightening truss; the upper end of the second heightening truss diagonal web member is fixed with the outer side plate surface of a second gusset plate c, the lower end of the second heightening truss diagonal web member is fixed with the outer side plate surface of a second gusset plate d, and the second gusset plate c is arranged at the splicing position of the upper chords of the first heightening truss and the second heightening truss; the upper end of the third heightening truss diagonal web member is fixed with the outer side plate surface of the second gusset plate c, and the lower end is fixed with the outer side plate surface of the first gusset plate d.

7. The fabricated cantilever capping beam bracket of claim 6, wherein the second connecting assembly comprises two connecting plates B, corresponding to the first and second connecting plates B, and a plurality of bolt assemblies;

the first connecting plate B is a straight plate, one end of the first connecting plate B is fixedly connected with an upper chord of an heightening truss of the first heightening truss girder through a bolt assembly, and the other end of the first connecting plate B is fixedly connected with an upper chord of a main truss of the main truss girder through a bolt assembly;

the second connecting plate B is a bending plate, one end of the second connecting plate B is fixedly connected with the lower chord of the first heightening truss girder through a bolt assembly, and the other end of the second connecting plate B is fixedly connected with the lower chord of the main truss girder through a bolt assembly.

8. The fabricated cantilever capping beam bracket of claim 7 wherein the sub-truss beam comprises a sub-truss upper chord, a sub-truss lower chord, a sub-truss straight web member, and a sub-truss diagonal web member, wherein:

the upper chord member and the lower chord member of the auxiliary truss are horizontally arranged, the straight web member of the auxiliary truss and the diagonal web member of the auxiliary truss are arranged between the upper chord member and the lower chord member of the auxiliary truss, the straight web member of the auxiliary truss is vertical, and the diagonal web member of the auxiliary truss is inclined;

the first auxiliary truss diagonal web members and the third auxiliary truss diagonal web members are symmetrically arranged on two sides of the first auxiliary truss straight web members, the second auxiliary truss diagonal web members and the fourth auxiliary truss diagonal web members are symmetrically arranged, the second auxiliary truss diagonal web members are arranged on the outer sides of the first auxiliary truss diagonal web members, and the fourth auxiliary truss diagonal web members are arranged on the outer sides of the third auxiliary truss diagonal web members; and the first to fourth auxiliary truss diagonal web members are integrally arranged in an M shape.

9. The fabricated cantilever capping beam bracket of claim 8 wherein the third connection assembly comprises an ear plate and a pin joint; the number of the lug plates and the number of the pin bolt joints are two;

10. A construction method of an assembly type cantilever bent cap support is characterized by comprising the following steps:

a. when the bearing platform is constructed, a fixed iron plate is embedded according to the size of the bracket and the position of the cross beam;

d. measuring the pile top elevation of a section of steel pipe pile at the top, calculating the adjusting height of the supporting sand box, and installing the supporting sand box;

c. the upper structure of the support is integrally installed on the ground, the main truss girder, the heightening truss girder, the auxiliary truss girder and the support frame are completely installed and then hoisted to the position of a supporting point of a supporting sand box, and the installation of the truss is checked and accepted before hoisting;

e. installing a bent cap I-steel bottom die beam on the upper structure of the support, and fixing an I-steel flange plate and an upper chord reinforced iron plate of the upper structure by using a U-shaped clamp;

f. mounting a cover beam bottom die on the I-shaped steel cross beam, binding cover beam steel bars, pouring cover beam concrete, and strictly monitoring the bracket in the cover beam construction process, wherein the deformation of the bracket cannot exceed 5mm;