CN114657898A - Construction method for cantilever beam in alpine region - Google Patents
Construction method for cantilever beam in alpine region Download PDFInfo
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Classifications
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D21/00—Methods or apparatus specially adapted for erecting or assembling bridges
- E01D21/10—Cantilevered erection
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/025—Adiabatic curing or hardening
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/0263—Hardening promoted by a rise in temperature
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G9/00—Forming or shuttering elements for general use
- E04G9/10—Forming or shuttering elements for general use with additional peculiarities such as surface shaping, insulating or heating, permeability to water or air
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D2101/00—Material constitution of bridges
- E01D2101/20—Concrete, stone or stone-like material
- E01D2101/24—Concrete
- E01D2101/26—Concrete reinforced
- E01D2101/28—Concrete reinforced prestressed
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Structural Engineering (AREA)
- Ceramic Engineering (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Building Environments (AREA)
Abstract
The invention relates to the technical field of building structure engineering, in particular to a construction method of a cantilever beam in a severe cold region, wherein a template structure with an outer heat-insulating body is arranged at the periphery of the cantilever beam to be cast, the cantilever beam to be cast is completely coated by the template structure to form a cantilever beam casting space, then the outer heat-insulating body is preheated to ensure that the temperature in the cantilever beam casting space reaches a target temperature, the cantilever beam construction is carried out at the target temperature to obtain the cantilever beam structure to be maintained, then the heat-insulating maintenance is carried out on the cantilever beam structure to be maintained to ensure that the cantilever beam structure to be maintained reaches the target strength, then the cantilever beam reaching the target strength is subjected to formwork removal, tensioning and grouting construction, finally the prestress of the cantilever beam reaches a design value, and the problem that moisture contained in the concrete of the cast-in-place cantilever beam is easy to freeze to cause the cantilever beam to be subjected to tensioning and grouting processes is solved, the cantilever beam is easy to break or the tension stress of the cantilever beam can not reach the designed value.
Description
Technical Field
The invention relates to the technical field of building structure engineering, in particular to a construction method of a suspended cast beam in a severe cold area.
Background
With the rapid development of economy and increasingly busy traffic and transportation services, the cross construction of highway bridges and existing lines is continuously increased, the structural form of the bridges is also continuously optimized and updated, and the prestressed continuous beam is widely adopted due to the characteristics of low manufacturing cost, large span, wide application range and the like. Due to the restrictions of geographical environment and climate conditions, the construction of bridges in winter is more and more common in northern areas.
In the prior art, when the prestressed cantilever beam construction is carried out in a severe cold or low temperature environment, the technical problem that in the severe cold or low temperature environment, moisture contained in concrete of a cast-in-place cantilever beam is easy to freeze, so that the cantilever beam is easy to break or the tensile stress strength of the cantilever beam cannot reach a design value when the cantilever beam is subjected to a tensioning and grouting process is often faced.
Disclosure of Invention
The invention mainly aims to provide a construction method of a cantilever beam in an alpine region, and aims to solve the technical problem that the prestress of the cantilever beam is difficult to reach the design value when the cantilever beam construction is carried out in the alpine or low-temperature region in the prior art.
In order to achieve the purpose, the construction method of the suspended cast beam in the alpine region, provided by the invention, comprises the following steps:
arranging a template structure with an external heat insulator at the periphery of the to-be-cast cantilever beam so that the template structure completely covers the to-be-cast cantilever beam to form a cantilever beam casting space;
preheating the outer heat insulation body so that the temperature in the casting space of the cantilever beam reaches a target temperature;
carrying out cantilever beam construction at the target temperature to obtain a cantilever beam structure to be maintained;
maintaining the suspended casting beam structure to be maintained in a heat preservation manner so that the suspended casting beam structure to be maintained achieves the target strength to form a suspended casting beam;
and removing the formwork, and tensioning and grouting the cantilever beam to enable the prestress system of the cantilever beam to reach a design value.
Optionally, a template structure with an outer heat insulator is arranged on the periphery of the cantilever beam to be poured, so that the template structure completely covers the cantilever beam to be poured to form a cantilever beam pouring space, and the method includes the following steps:
fixedly arranging a heat-insulating layer supporting framework on the outer surface of the template to form a heat-insulating layer primary structure on the outer side surface of the template;
arranging a temperature adjusting piece on the heat-insulating layer supporting framework to enable the heat-insulating layer primary structure to form a temperature adjusting structure with a temperature adjusting function;
spraying a heat insulation material on the temperature adjusting structure, and enabling the heat insulation material to completely coat the temperature adjusting structure to form a heat insulation template;
and respectively placing at least four heat-insulating templates at the bottom, two sides and the end part of the cantilever beam to be poured, and connecting every two adjacent parts of the at least four heat-insulating templates to form a template structure, so that the cantilever beam to be poured is completely coated by the template structure to form a cantilever beam pouring space.
Optionally, the preheating the outer thermal insulation body to make the temperature in the cantilever beam casting space reach a target temperature includes:
preheating the heat-insulating layer through the temperature adjusting piece so as to raise the temperature in the pouring space of the cantilever beam;
and detecting and adjusting the temperature in the cantilever beam pouring space through the temperature adjusting piece so as to enable the temperature in the cantilever beam pouring space to reach a target temperature.
Optionally, the construction of the cantilever beam at the target temperature to obtain the cantilever beam structure to be maintained comprises the following steps:
binding reinforcing steel bars in the pouring space of the cantilever beam at the target temperature to obtain a cantilever beam reinforcement cage framework;
preparing a concrete mixture, and adjusting the temperature of the mixture to enable the temperature of the concrete mixture to reach a target pouring temperature;
pouring the mixture reaching the target pouring temperature into the cantilever beam pouring space, and enabling the mixture to completely coat the cantilever beam reinforcement cage framework;
and vibrating the mixture poured into the pouring space of the cantilever beam to obtain the cantilever beam structure to be maintained.
Optionally, the target casting temperature value is not less than 10 ℃ and not more than 30 ℃.
Optionally, the construction of the cantilever beam is performed at the target temperature to obtain a cantilever beam structure to be maintained, and the method further includes the following steps:
under the target temperature, three groups of maintenance test pieces are additionally arranged;
maintaining the three groups of maintenance test pieces at the target temperature, respectively carrying out pressure testing on the three groups of maintenance test pieces 5 days, 6 days and 7 days after pouring, and judging whether the maintenance test pieces reach the design strength corresponding to the maintenance time;
and after the maintenance test piece reaches the design strength, stopping heat preservation maintenance of the cantilever beam structure to be maintained to obtain the cantilever beam structure.
Optionally, the three groups of maintenance test pieces are maintained at the target temperature, the three groups of maintenance test pieces are respectively subjected to pressure testing with the three groups of maintenance test pieces 5 days, 6 days and 7 days after pouring, and whether the maintenance test pieces reach the design strength corresponding to the maintenance time is judged, wherein the design strength in the step of:
the corresponding design strength is 75-80% in 5 days after pouring;
the corresponding design strength is not lower than 90% 7 days after pouring.
Optionally, the maintaining and maintaining of the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach the target strength, and the forming of the cantilever beam comprises the following steps:
the outer heat insulator is heated again through the temperature adjusting part, and the temperature in the pouring space of the cantilever beam is maintained at the target temperature;
at the target temperature, adjusting the environment humidity in the pouring space of the cantilever beam to reach the target environment humidity;
and maintaining the cantilever beam structure to be maintained under the target environment humidity so as to enable the cantilever beam structure to be maintained to reach the target strength, and forming the cantilever beam.
Optionally, the formwork stripping and tensioning and grouting the cantilever beam with the target strength being reached so as to enable a prestress system of the cantilever beam to reach a design value, including the following steps:
stopping temperature supply of the temperature adjusting piece to finish heat preservation of the cast space of the cantilever beam;
removing the template structure to expose the suspension casting beam in a natural environment;
and carrying out tensioning and grouting construction on the cantilever beam exposed in the natural environment so as to enable a prestress system of the cantilever beam to reach a design value.
Optionally, the tensioning and grouting construction of the cantilever beam exposed in the natural environment to enable the prestress system of the cantilever beam to reach the design value includes the following steps:
tensioning the cantilever beam to change the prestress of the cantilever beam;
carrying out grouting construction on the cantilever beam, and adjusting the prestress of the cantilever beam so as to enable the prestress system of the cantilever beam to reach a design value;
and/or the presence of a gas in the gas,
grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the duration from the completion of slurry mixing to the pressing of the pore channel of the suspended casting beam is not more than 40 min;
and/or the presence of a gas in the gas,
grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the temperature of the slurry is kept between 5 and 30 ℃ during grouting.
Has the advantages that:
the technical scheme of the invention includes that a template structure with an outer heat insulator is arranged on the periphery of a cantilever beam to be cast, the cantilever beam to be cast is completely coated by the template structure to form a cantilever beam casting space, then the outer heat insulator is preheated to enable the temperature in the cantilever beam casting space to reach a target temperature, cantilever beam construction is carried out at the target temperature to obtain a cantilever beam structure to be maintained, heat preservation maintenance is carried out on the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach a target strength, then formwork stripping, tensioning and grouting construction are carried out on the cantilever beam reaching the strength to finally enable the prestress of the cantilever beam to reach a design value, and through the arrangement mode, the invention realizes the construction of the prestress cantilever beam structure meeting design requirements in a high-cold or low-temperature environment, and solves the problem that when the prestress cantilever beam is constructed in the high-cold or low-temperature area in the prior art, the water contained in the concrete of the cast-in-place cantilever beam is easy to freeze, which causes the technical defect that the cantilever beam is easy to break or the tensile stress of the cantilever beam can not reach the designed value when the cantilever beam is subjected to the tensioning and grouting process.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to a first embodiment of the invention;
FIG. 2 is a schematic flow chart of another embodiment of the construction method of the cantilever beam in the alpine region of the present invention;
FIG. 3 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to another embodiment of the present invention;
FIG. 4 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to yet another embodiment of the present invention;
fig. 5 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to still another embodiment of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
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. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
With the rapid development of economy and increasingly busy traffic and transportation services, the cross construction of highway bridges and existing lines is continuously increased, the structural form of the bridges is also continuously optimized and updated, and the prestressed continuous beam is widely adopted due to the characteristics of low manufacturing cost, large span, wide application range and the like. Due to the restrictions of geographical environment and climate conditions, the construction of bridges in winter is more and more common in northern areas.
In the prior art, when the prestressed cantilever beam is constructed in a severe cold or low-temperature environment, the technical problem faced by the field is that in the severe cold or low-temperature environment, moisture contained in concrete of a cast-in-place cantilever beam is easy to freeze, so that the cantilever beam is easy to break or the tensile stress strength of the cantilever beam cannot reach a design value when the cantilever beam is subjected to a tensioning and grouting process.
Based on the construction, the invention provides a construction method of a suspended cast beam in alpine regions, which comprises the steps of arranging a template structure with an outer heat insulation body at the periphery of the suspended cast beam to be cast, completely coating the suspended cast beam to be cast by using the template structure to form a suspended cast beam casting space, preheating the outer heat insulation body to enable the temperature in the suspended cast beam casting space to reach a target temperature, carrying out suspended cast beam construction at the target temperature to obtain a suspended cast beam structure to be maintained, carrying out heat preservation maintenance on the suspended cast beam structure to be maintained to enable the suspended cast beam structure to reach the target strength, then carrying out form removal, tensioning and grouting construction on the suspended cast beam reaching the strength to finally enable the prestress of the suspended cast beam to reach a design value, and realizing the construction of the prestress cast beam structure meeting the design requirements in alpine or low-temperature environments by the arrangement mode, the technical defects that when the prestressed cantilever beam is constructed in a severe cold or low temperature area, moisture contained in concrete of the cast-in-place cantilever beam is easy to freeze, so that the cantilever beam is easy to break or the tensile stress of the cantilever beam cannot reach a designed value when the cantilever beam is subjected to a tensioning and grouting process in the prior art are overcome.
The inventive concept of the present invention will be further elucidated below in connection with some specific embodiments.
In an embodiment of the invention, the construction method of the cantilever beam in the alpine region comprises the following steps:
s100, arranging a template structure with an outer heat insulator at the periphery of the to-be-cast cantilever beam, so that the template structure completely covers the to-be-cast cantilever beam to form a cantilever beam casting space;
when the formwork structure is arranged, firstly, the formwork with the outer heat insulator is laid at the bottom, two sides and the end of the cantilever beam to be poured, and the placed formworks are connected to form the formwork structure capable of completely coating the cantilever beam to be poured, and at the moment, the space inside the formwork structure is the cantilever beam pouring space. Of course, in this embodiment, it is worth noting that the cantilever beam is generally a box beam, which is understood that the interior of the cantilever beam is a hollow position, in other words, when the cantilever beam pouring space is provided, a formwork structure needs to be provided in the interior of the cantilever beam to be poured. The pouring space of the cantilever beam is an interlayer space formed by an inner formwork structure arranged inside the cantilever beam and an outer formwork structure arranged outside the cantilever beam.
S200, preheating the outer heat insulator to enable the temperature in the casting space of the cantilever beam to reach a target temperature;
when preheating the external heat-insulating body, whether the temperature in the pouring space of the cantilever beam reaches the target preset temperature needs to be detected and judged in real time, if the temperature does not reach the preset temperature, the external heat-insulating body is continuously heated until the pouring space of the cantilever beam reaches the target temperature.
It should be noted that, in this embodiment, the target temperature is an optimum temperature for curing the cast-in-place concrete structure in the natural environment. It can be further stated that the optimum temperature value for maintaining the cast-in-place concrete structure in the natural environment is 20 ℃.
S300, performing cantilever beam construction at the target temperature to obtain a cantilever beam structure to be maintained;
s400, performing heat preservation maintenance on the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach the target strength, and forming a cantilever beam;
s500, removing the formwork, and stretching and grouting the cantilever beam to enable a prestress system of the cantilever beam to reach a design value.
The cantilever beam is not supported at both ends, one end of the cantilever beam is buried or poured on the support, and the other end of the cantilever beam extends out of the support.
The cantilever beam is not a floor slab with direct supports (pillars, solid walls) on each side, and is partially buried or poured in a building structure, and the other part of the cantilever beam extends out of the cantilever structure and is a cantilever plate (such as a cantilever balcony or a roof).
The cast-in-place method is mostly adopted for construction of the cantilever beam, and the prestressed cantilever beam is mostly used for the cast-in-place construction of the cantilever beam. The prestressed suspension casting beam in actual use is mostly obtained by construction through a tensioning method and a mud jacking method. The requirements on the strength and the hardness of the cantilever beam are high when the cantilever beam is constructed by the stretching and pulling method, so that the cantilever beam needs to reach the designed strength when the stretching and pulling method is carried out.
The tension method is to add tension in advance in the component, so that the applied prestress tension component bears compressive stress, and further the component generates certain deformation to deal with the load of the structure, including the load of the component self weight, wind load, snow load, earthquake load action and the like. Generally, the steel strand, the jack, the anchor plate and the clamping piece are used for tensioning.
The grouting is grouting in a corrugated pipe of a prestressed beam after the steel strand is tensioned, and is used for compacting the pipe, fixing the steel strand and helping the steel strand to bear force.
Before the engineering structural member bears external load, pretension stress is applied to the steel strands in the tension module, the bending resistance and rigidity of the member are improved, cracks are controlled, and the durability of the member is improved. In the mechanical structure, the stress is generated in advance, and the advantages of the mechanical structure are that the rigidity of the structure can be improved, the vibration and the elastic deformation are reduced, the elastic strength of the tension module can be obviously improved, and the original resistance is stronger.
The technical scheme of the invention includes that a template structure with an outer heat insulator is arranged on the periphery of a cantilever beam to be cast, the cantilever beam to be cast is completely coated by the template structure to form a cantilever beam casting space, then the outer heat insulator is preheated to enable the temperature in the cantilever beam casting space to reach a target temperature, cantilever beam construction is carried out at the target temperature to obtain a cantilever beam structure to be maintained, heat preservation maintenance is carried out on the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach a target strength, then formwork stripping, tensioning and grouting construction are carried out on the cantilever beam reaching the strength to finally enable the prestress of the cantilever beam to reach a design value, and through the arrangement mode, the invention realizes the construction of the prestress cantilever beam structure meeting design requirements in a high-cold or low-temperature environment, and solves the problem that when the prestress cantilever beam is constructed in the high-cold or low-temperature area in the prior art, the water contained in the concrete of the cast-in-place cantilever beam is easy to freeze, which causes the technical defect that the cantilever beam is easy to break or the tensile stress of the cantilever beam can not reach the designed value when the cantilever beam is subjected to the tensioning and grouting process.
Based on the above embodiment, another embodiment of the construction method of the cantilever beam in the alpine region is provided, which is shown in fig. 2 to 5: FIG. 2 is a schematic flow chart of another embodiment of the construction method of the cantilever beam in the alpine region of the present invention; FIG. 3 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to another embodiment of the present invention; FIG. 4 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to yet another embodiment of the present invention; fig. 5 is a schematic flow chart of a construction method of a cantilever beam in a severe cold area according to still another embodiment of the present invention.
As an improved embodiment, optionally, a template structure with an outer thermal insulator is arranged on the periphery of the cantilever beam to be cast, so that the template structure completely covers the cantilever beam to be cast to form a cantilever beam casting space, and the method includes the following steps:
s101, fixedly arranging a heat-insulating layer supporting framework on the outer surface of a template to enable the outer side surface of the template to form a heat-insulating layer primary structure;
in this embodiment, in order to prevent the outer heat insulator from falling off when the heat insulator is used, the outer surface of the template is provided with the heat insulation layer supporting framework fixed with the outer surface of the template, and then the heat insulation material is sprayed, so that the heat insulation material and the heat insulation layer supporting framework form an integral structure, and finally the function of preventing the heat insulator from falling off is achieved.
As a modified example, in this embodiment, it is particularly clear and described that, in this embodiment, the insulating layer supporting framework is a framework-like structure capable of supporting the insulating layer. When the insulating layer supporting framework of the embodiment is selected or applied by a technician, a steel wire mesh frame or a mesh structure made of soft and firm materials such as Kevlar fiber mesh, ultra-density polyethylene and carbon fibers can be used as the insulating layer supporting framework, and the connecting piece for connecting the supporting framework and the template can be made of materials with high hardness such as steel bars and carbon fiber rods.
In this embodiment, the heat preservation layer is the structure that can be connected with the template outside surface and carry out the heat preservation to template and cantilever beam. The insulation layer may be made of, but not limited to, the following materials or structures: the material can be directly adhered or sprayed on the surface of a template to form a heat-insulating layer, such as a flame-retardant polyurethane plate, a glass wool plate, a molded/extruded polystyrene plate phenolic resin plate and the like.
As will be readily understood, in the related art, in the manufacture of the insulation layer, a flame-retardant polyurethane foaming agent is generally sprayed on the outer surface of the formwork to form the insulation layer. In this embodiment, it is also preferred to spray with a flame retardant polyurethane foam.
As a further example, the insulating layer support frame comprises:
the steel wire mesh is laid on the outer side surface of the template; and
at least one rebar hook, the rebar hook includes first end and second end, first end colludes to be in on the steel wire netting, the second end is fixed on the outside surface of template.
In the embodiment, the steel wire mesh is laid on the outer side surface of the template, at least one steel bar drag hook is welded on the outer side surface of the template, and the steel wire mesh is fixed by the steel bar drag hook, so that the purpose of fixing the heat-insulating layer supporting framework on the outer side surface of the template is finally realized. Further solves the technical defect that the sprayed heat-insulating layer is easy to fall off when the heat-insulating layer is manufactured on the outer surface of the template in the related technology.
It should be noted that, as a preferred embodiment, in this embodiment, the steel mesh is preferably a steel mesh with a pore size of 3cm × 3 cm. The steel bar draw hook is preferably made of phi 8 steel bars, and one steel bar draw hook is preferably arranged at intervals of 60cm multiplied by 80cm according to the size of the rib of the template.
S102, arranging a temperature adjusting piece on the heat-insulating layer supporting framework to enable the heat-insulating layer primary structure to form a temperature adjusting structure with a temperature adjusting function;
in this embodiment, the temperature adjusting member disposed on the supporting framework may be an existing structure (such as a conveying pipeline, a metal heat conductor, etc.) that directly conveys an external heat source into the heat insulating body and heats the heat insulating body, or may be a self-heating material, such as a resistance heating belt that converts electric energy into heat energy.
It may be further stated that said temperature adjustment member comprises:
the main heating belt is laid on the steel wire mesh and communicated with an external heat source or a power source; and
at least two mountings, at least two the mounting all will main heating area with wire net fixed connection.
In the embodiment, the main heating belt is arranged, and the main heating belt is fixed on the steel wire mesh by the at least two fixing pieces, so that the suspended cast beam can be subjected to continuous heat preservation in the high-cold low-temperature environment, and the technical defect of temperature loss caused by temperature shock of the high-cold low-temperature environment is effectively overcome.
It should be particularly clear and explained that, as a preferred embodiment, in the present embodiment, the main heating belt is an existing structure capable of introducing an external heat source or performing self-heating under the supply of external power or energy. In the present embodiment, the main heating belt is preferably a conventional technology or structure capable of realizing self-heating under the driving or supplying of external power (such as a heat pump, an air pump, etc.) or external energy (such as electric energy, solar energy, fossil energy, etc.), and the present embodiment is only applied thereto. Preferably, this embodiment may exemplify that the main heating belt is a heating wire which performs self-heating under the action of electric power.
Of course, it can be further explained that the fixing member is an existing fixing member capable of fixing the main heating belt on the steel wire mesh. Fasteners that may be generally employed by those skilled in the art include, but are not limited to, the following types: the conventional components such as a binding belt, a binding wire or a hoop can fix the main heating belt on the steel wire mesh.
In order to further improve the thermal insulation performance of the present invention, optionally, the method further includes:
the standby heating belt is laid on the steel wire mesh;
the fixing piece is used for fixedly connecting the standby heating belt with the steel wire mesh.
Through setting up reserve heating band to utilize the mounting to fix reserve heating band on the steel wire net, when main heating band can not normally work, the technical staff can adopt reserve heating band to heat the heat-insulating body at once, so that the heat-insulating body can keep warm to the cantilever beam under the most suitable temperature.
It should be particularly clear and explained that, as a preferred embodiment, in the present embodiment, the standby heating belt is an existing structure capable of introducing an external heat source or performing self-heating under the supply of external power or energy. In the present embodiment, the backup heating band is preferably a prior art or a structure that can realize self-heating under the driving or supplying of external power (such as a heat pump, an air pump, etc.) or external energy (such as electric energy, solar energy, fossil energy, etc.), and the present embodiment is only applied to this. Preferably, this embodiment may exemplify that the backup heating belt is a heating wire that performs self-heating under the action of electric power.
S103, spraying a heat insulation material on the temperature adjusting structure, and enabling the heat insulation material to completely coat the temperature adjusting structure to form a heat insulation template;
and at least the heat-insulating layer is formed by mixing a polyurethane foaming agent and a flame retardant according to a ratio of 1:1 and spraying the mixture on the outer side surface of the template. In this embodiment, the mixture spraying that adopts polyurethane foam and fire retardant to form forms the heat preservation on the outside surface of template for the heat preservation has still possessed fire-retardant function on the basis that possesses the heat preservation function, has effectively avoided leading to the hidden danger that partial material burns and causes the incident because of long-term high temperature.
In a preferred embodiment, the polyurethane foam is a high molecular polymer prepared by mixing isocyanate and polyether as main raw materials with a special device under the action of various auxiliary agents such as a blowing agent, a catalyst, a flame retardant and the like, and then spraying the mixture at high pressure to foam the mixture in situ. Polyurethane has both soft and hard foams. The soft bubbles are of an open pore structure, and the hard bubbles are of a closed pore structure; soft foams are classified into skinned and non-skinned.
The flame retardant is a functional auxiliary agent for endowing the inflammable polymer with flame retardancy, and is mainly designed aiming at the flame retardancy of a high polymer material; the flame retardants are of various types, and are classified into additive type flame retardants and reactive type flame retardants according to the method of use.
The additive flame retardant is added into the polymer by a mechanical mixing method to enable the polymer to have flame retardance, and the additive flame retardant mainly comprises an organic flame retardant, an inorganic flame retardant, a halogen flame retardant (organic chloride and organic bromide) and non-halogen. Organic flame retardants are represented by bromine, phosphorus-nitrogen, red phosphorus and compounds, and inorganic flame retardants are mainly flame retardant systems such as antimony trioxide, magnesium hydroxide, aluminum hydroxide, silicon and the like.
The reactive flame retardant is used as a monomer to participate in polymerization reaction, so that the polymer contains a flame retardant component, and the reactive flame retardant has the advantages of less influence on the service performance of a polymer material and lasting flame retardance.
S104, respectively placing at least four heat preservation templates at the bottom, two sides and the end of the cantilever beam to be poured, and enabling every two adjacent positions of the at least four heat preservation templates to be connected to form a template structure, so that the cantilever beam to be poured is completely coated by the template structure to form a cantilever beam pouring space.
In this embodiment, at least four heat preservation templates are adopted, and the to-be-cast cantilever beam is completely coated by the heat preservation templates, so as to form a cantilever beam casting space. In this embodiment, it can be further stated that, when the cantilever beam casting space is manufactured, the shape of the cantilever beam casting space is often determined according to the specific shape of the cantilever beam. In the correlation technique, the common cantilever beam is mostly a box girder type structure. The assembly is that when the box girder type cantilever beam structure is constructed, the cantilever beam pouring space formed by enclosing is defined by an inner template structure arranged inside the cantilever beam and an outer template structure arranged outside the cantilever beam together to form a sandwich type cantilever beam pouring space. When the suspended cast beam pouring space needs to be enclosed, at least eight heat-insulating templates are used. Inner four blocks and outer four blocks.
By adopting the technical scheme, the invention realizes the purpose of preventing the heat insulation body sprayed on the outer surface of the template from falling off, and effectively improves the heat insulation effect of the heat insulation template.
Optionally, preheating the outer thermal insulator to make the temperature in the cast-in-place space of the cantilever beam reach a target temperature, includes:
s201, preheating the heat-insulating layer through the temperature adjusting piece to enable the temperature in the pouring space of the cantilever beam to rise;
s202, detecting and adjusting the temperature in the cantilever beam pouring space through the temperature adjusting piece, so that the temperature in the cantilever beam pouring space reaches a target temperature.
Optionally, the construction of the cantilever beam at the target temperature to obtain the cantilever beam structure to be maintained comprises the following steps:
s301, binding reinforcing steel bars in the pouring space of the cantilever beam at the target temperature to obtain a cantilever beam reinforcement cage framework;
s302, configuring a concrete mixture, and adjusting the temperature of the mixture to enable the temperature of the concrete mixture to reach a target pouring temperature;
s303, pouring the mixture reaching the target pouring temperature into the suspended cast beam pouring space, and completely coating the suspended cast beam reinforcement cage framework with the mixture;
s304, vibrating the mixture poured into the pouring space of the cantilever beam to obtain the cantilever beam structure to be maintained.
In this embodiment, when carrying out the stirring of concrete mixture, the temperature of mixing to the mixture is controlled for adopt this kind of mixture to hang when watering the roof beam and pour, can not lead to hanging because of the mixture absorbs the more temperature and water the roof beam and pour the undulant too big of the temperature in the space, the influence hangs the construction quality who waters the roof beam.
As a preferred embodiment, in this embodiment, it can be further stated that the target casting temperature is a temperature after the temperature of the mixture is adjusted, that is, at this temperature, the technical effect that the temperature in the casting space of the cantilever beam is not affected may not be achieved, and the purpose that the construction quality of the cantilever beam is not affected may also be achieved.
Optionally, the target casting temperature value is not less than 10 ℃ and not more than 30 ℃.
In this embodiment, in the time mixing process, the target pouring temperature of the mixture is set to be not less than 10 ℃, and is not greater than 30 ℃, so that the temperature does not affect the mixing quality of the mixture within the temperature interval, and the construction quality of the cantilever beam is not affected during construction.
As a preferred embodiment, in this embodiment, it can be further explained that the target casting temperature is preferably 20 ℃. When pouring is carried out at the temperature, the target mixing temperature of the mixture is the same as the target temperature in the cantilever beam pouring space, namely the mixture cannot absorb the temperature in the cantilever beam target pouring space, so that the temperature value in the cantilever beam target pouring space fluctuates, and the pouring quality of the cantilever beam is influenced.
Optionally, the construction of the cantilever beam is performed at the target temperature to obtain a cantilever beam structure to be maintained, and the method further includes the following steps:
s305, additionally arranging three groups of maintenance test pieces at the target temperature;
s306, curing the three groups of curing test pieces at the target temperature, respectively carrying out pressure testing on the three groups of curing test pieces 5 days, 6 days and 7 days after pouring, and judging whether the curing test pieces reach the design strength corresponding to the curing time;
and S307, after the maintenance test piece reaches the design strength, stopping heat preservation maintenance of the cantilever beam structure to be maintained, and obtaining the cantilever beam structure.
As a preferred embodiment, in this embodiment, three sets of maintenance test pieces are added for the purpose of enabling a technician to accurately measure the strength of the maintenance test piece maintained under the maintenance of the maintenance method by maintaining and pressure-testing the added maintenance test pieces. The predictability and the mastering strength of technicians on the overall strength of the cast-in-place cantilever beam are improved.
As an improved embodiment, in this embodiment, optionally, the curing test pieces of three groups are maintained at the target temperature, and the curing test pieces of three groups are respectively subjected to pressure testing 5 days, 6 days and 7 days after pouring, and the design strength in the step of determining whether the curing test pieces reach the design strength corresponding to the curing time is:
the corresponding design strength is 75-80% in 5 days after pouring;
the corresponding design strength is not lower than 90% 7 days after pouring.
In this embodiment, through the pressure testing test to three group's maintenance test pieces 5 days after pouring, 6 days and 7 days in time for the technician can know constantly and be located the intensity of the hanging beam that waters of different maintenance time quantum, so that the technician real-time adjustment is to hanging the maintenance temperature of watering the roof beam, very big promotion the convenience of maintenance and carry out the maintenance effect of maintenance to hanging the roof beam of watering.
Optionally, the maintaining and maintaining of the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach the target strength, and the forming of the cantilever beam comprises the following steps:
s401, reheating the outer heat insulator through the temperature adjusting part, and maintaining the temperature in the casting space of the cantilever beam at the target temperature;
s402, adjusting the environment humidity in the cantilever beam pouring space at the target temperature to reach the target environment humidity;
and S403, maintaining the cantilever beam structure to be maintained under the target environment humidity, so that the cantilever beam structure to be maintained achieves the target strength, and forming the cantilever beam.
When treating maintenance cantilever beam structure and carrying out the maintenance, through the regulation to cantilever beam pouring environmental humidity in the space for treat the maintenance cantilever beam structure can be by abundant maintenance under target environmental humidity, effectively ensured treat the maintenance effect of maintenance cantilever beam structure, also promoted the quality of cantilever beam.
As a preferred embodiment, in this embodiment, it can be further explained that the target curing humidity is the optimal curing humidity required for cast-in-place concrete. In this embodiment, it can be said that the target curing humidity is greater than 95%.
As a preferred embodiment, the method of controlling the target curing humidity may be implemented by spraying water mist through a pipe or supplying water vapor. Of course, in the present embodiment, the steam curing system is preferably used for supplying the hot and humid water vapor.
As a preferred embodiment, in this embodiment, optionally, the removing the formwork and tensioning and grouting the cantilever beam having reached the target strength to make the prestressed system of the cantilever beam reach the design value includes the following steps:
s501, stopping temperature supply of the temperature adjusting piece to finish heat preservation of the cast space of the cantilever beam;
s502, removing the template structure to expose the suspended casting beam in a natural environment;
s503, carrying out tensioning and grouting construction on the cantilever beam exposed in the natural environment so as to enable a prestress system of the cantilever beam to reach a design value.
When the prestress is tensioned, the strength of the beam concrete must reach 95% of the design value, the elastic modulus reaches 90% of the design value, and the tensioning can be carried out after the age of the concrete is not less than 7 days.
And a fuel oil warm air gun is arranged in each box room at the top of the poured cantilever beam section, and the box rooms are heated through the skylight opening, so that the maintenance environment is improved.
A pulping heat preservation shed is built on the top surface 0# block of the box girder (the pulping heat preservation shed is built by adopting a scaffold and is packaged by a color steel plate), an electric heating furnace is adopted for heating the inside of the pulping heat preservation shed, the area requirement can meet the requirements of storing and operating a grouting machine for grouting materials, and the temperature of the grouting materials and the temperature of mixing water are not less than 20m2, so that the construction requirements can be met.
In order to prevent the grouting material from being frozen and ensure the grouting quality, the grouting material adopts 'HS-TianYL antifreezing type prestressed pipeline grouting material'. The HS-TianYL antifreezing prestressed pipeline grouting material is prepared by finely mixing an inorganic gelling agent and various mineral materials. The product is convenient to use and can be used by directly adding water. The antifreeze grouting material has a chloride ion content of less than or equal to 0.06 and does not rust the steel strand. The strength requirement can be met in a low-temperature environment (-20 ℃). Meets the standard requirements of technical Specifications for highway, bridge and culvert construction (JTG/T F50-2020) and prestressed duct grouting agent (GB/T25182-2010).
The performance indexes of the antifreeze prestressed pipeline grouting material are as follows:
TABLE 1 Frost-resistant prestressed pipe grouting material performance index
And (4) keeping the same-condition maintenance test piece in the grouting process, placing the test piece on the top surface of the beam body, and reflecting the same-condition strength of the grout. And curing the test pieces of each group of grouting materials under the same conditions to obtain no less than 3 groups, and respectively detecting the strength for 3 days, 7 days and 28 days.
By adopting the scheme, the prestressed cantilever beam structure meeting the design requirement is manufactured in the high-cold or low-temperature environment.
As an improved embodiment, in this embodiment, optionally, the tensioning and grouting construction of the cantilever beam exposed in the natural environment to make the prestressed system of the cantilever beam reach the design value includes the following steps:
tensioning the cantilever beam to change the prestress of the cantilever beam;
carrying out grouting construction on the cantilever beam, and adjusting the prestress of the cantilever beam so as to enable the prestress system of the cantilever beam to reach a design value;
by carrying out tensioning construction on the cantilever beam reaching the designed strength, the prestress of the cantilever beam reaches the designed value.
Grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the duration from the completion of slurry mixing to the pressing of the pore channel of the suspended casting beam is not more than 40 min;
in the embodiment, the duration from the completion of slurry mixing to the pressing of the hole of the cantilever beam is not more than 40min, so that the whole quality of the prestressed cantilever beam cannot be influenced by the slurry mixing due to consolidation.
It is further required that the optimal duration time cannot exceed 15min, and the consolidation effect of the slurry can be effectively guaranteed in the time range.
Grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the temperature of the slurry is kept between 5 and 30 ℃ during grouting.
In this embodiment, the advantage of maintaining the temperature of the slurry at 5-30 ℃ is that in this temperature range, the water material in the slurry will not be solidified due to too low temperature, and the overall strength of the slurry is strongly guaranteed.
Of course, it can be further stated that the slurry has an optimum temperature value of 20 ℃.
The technical scheme of the invention includes that a template structure with an outer heat insulator is arranged on the periphery of a cantilever beam to be cast, the cantilever beam to be cast is completely coated by the template structure to form a cantilever beam casting space, then the outer heat insulator is preheated to enable the temperature in the cantilever beam casting space to reach a target temperature, cantilever beam construction is carried out at the target temperature to obtain a cantilever beam structure to be maintained, heat preservation maintenance is carried out on the cantilever beam structure to be maintained to enable the cantilever beam structure to be maintained to reach a target strength, then formwork stripping, tensioning and grouting construction are carried out on the cantilever beam reaching the strength to finally enable the prestress of the cantilever beam to reach a design value, and through the arrangement mode, the invention realizes the construction of the prestress cantilever beam structure meeting design requirements in a high-cold or low-temperature environment, and solves the problem that when the prestress cantilever beam is constructed in the high-cold or low-temperature area in the prior art, the water contained in the concrete of the cast-in-place cantilever beam is easy to freeze, which causes the technical defect that the cantilever beam is easy to break or the tensile stress of the cantilever beam can not reach the designed value when the cantilever beam is subjected to the tensioning and grouting process.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A construction method for a suspended cast beam in an alpine region is characterized by comprising the following steps:
arranging a template structure with an outer heat insulator at the periphery of the cantilever beam to be cast, so that the template structure completely covers the cantilever beam to be cast to form a cantilever beam casting space;
preheating the outer heat insulation body so that the temperature in the casting space of the cantilever beam reaches a target temperature;
carrying out cantilever beam construction at the target temperature to obtain a cantilever beam structure to be maintained;
maintaining the suspended casting beam structure to be maintained in a heat preservation manner so that the suspended casting beam structure to be maintained achieves the target strength to form a suspended casting beam;
and removing the formwork, and tensioning and grouting the suspended casting beam so as to enable a prestress system of the suspended casting beam to reach a design value.
2. The construction method of the cantilever beam in the alpine region according to claim 1, wherein a template structure with an outer heat insulator is arranged on the periphery of the cantilever beam to be cast, so that the template structure completely covers the cantilever beam to be cast to form a cantilever beam casting space, and the construction method comprises the following steps:
fixedly arranging a heat-insulating layer supporting framework on the outer surface of the template so as to form a heat-insulating layer primary structure on the outer side surface of the template;
arranging a temperature adjusting piece on the heat-insulating layer supporting framework to enable the heat-insulating layer primary structure to form a temperature adjusting structure with a temperature adjusting function;
spraying a heat insulation material on the temperature adjusting structure, and enabling the heat insulation material to completely coat the temperature adjusting structure to form a heat insulation template;
and respectively placing at least four heat-insulating templates at the bottom, two sides and the end part of the cantilever beam to be poured, and connecting every two adjacent parts of the at least four heat-insulating templates to form a template structure, so that the cantilever beam to be poured is completely coated by the template structure to form a cantilever beam pouring space.
3. The construction method of the cantilever beam in the alpine region according to claim 2, wherein the preheating the outer heat insulator to make the temperature in the cantilever beam casting space reach a target temperature comprises:
preheating the heat-insulating layer through the temperature adjusting piece so as to raise the temperature in the pouring space of the cantilever beam;
and detecting and adjusting the temperature in the cantilever beam pouring space through the temperature adjusting piece so as to enable the temperature in the cantilever beam pouring space to reach a target temperature.
4. The construction method of the cantilever beam in the alpine region according to claim 2, wherein the construction of the cantilever beam at the target temperature to obtain the cantilever beam structure to be maintained comprises the following steps:
binding reinforcing steel bars in the pouring space of the cantilever beam at the target temperature to obtain a cantilever beam reinforcement cage framework;
preparing a concrete mixture, and adjusting the temperature of the mixture to enable the temperature of the concrete mixture to reach a target pouring temperature;
pouring the mixture reaching the target pouring temperature into the cantilever beam pouring space, and enabling the mixture to completely coat the cantilever beam reinforcement cage framework;
and vibrating the mixture poured into the pouring space of the cantilever beam to obtain the cantilever beam structure to be maintained.
5. The construction method of the cantilever beam in the alpine region according to claim 4, wherein the target casting temperature value is not less than 10 ℃ and not more than 30 ℃.
6. The construction method of the cantilever beam in the alpine region according to claim 2, wherein the cantilever beam construction is performed at the target temperature to obtain a cantilever beam structure to be maintained, and further comprising the steps of:
under the target temperature, three groups of maintenance test pieces are additionally arranged;
maintaining the three groups of maintenance test pieces at the target temperature, respectively carrying out pressure testing on the three groups of maintenance test pieces 5 days, 6 days and 7 days after pouring, and judging whether the maintenance test pieces reach the design strength corresponding to the maintenance time;
and after the maintenance test piece reaches the design strength, stopping heat preservation maintenance of the cantilever beam structure to be maintained to obtain the cantilever beam structure.
7. The construction method of the cantilever beam in the alpine region according to claim 6,
maintaining three groups of maintenance test pieces at the target temperature, respectively carrying out pressure testing on the three groups of maintenance test pieces 5 days, 6 days and 7 days after pouring, and judging whether the maintenance test pieces reach the design strength corresponding to the maintenance time, wherein the design strength is as follows:
the corresponding design strength is 75-80% in 5 days after pouring;
the corresponding design strength is not lower than 90% 7 days after pouring.
8. The construction method of the cantilever beam in the alpine region according to claim 2, wherein the heat preservation and maintenance of the cantilever beam structure to be maintained are performed to enable the cantilever beam structure to be maintained to reach a target strength, and the formation of the cantilever beam comprises the following steps:
the outer heat insulator is heated again through the temperature adjusting part, and the temperature in the pouring space of the cantilever beam is maintained at the target temperature;
at the target temperature, adjusting the environment humidity in the pouring space of the cantilever beam to reach the target environment humidity;
and maintaining the cantilever beam structure to be maintained under the target environment humidity so as to enable the cantilever beam structure to be maintained to reach the target strength, and forming the cantilever beam.
9. The construction method of the cantilever beam in the alpine region according to claim 2, wherein the formwork removal and the tensioning and grouting of the cantilever beam which has reached the target strength are performed to make a prestress system of the cantilever beam reach a design value, and the method comprises the following steps:
stopping temperature supply of the temperature adjusting piece to finish heat preservation of the cast space of the cantilever beam;
removing the template structure to expose the suspension casting beam in a natural environment;
and carrying out tensioning and grouting construction on the cantilever beam exposed in the natural environment so as to enable a prestress system of the cantilever beam to reach a design value.
10. The construction method of the cantilever beam in the alpine region according to claim 9, wherein the step of performing tensioning and grouting construction on the cantilever beam exposed in the natural environment to enable a prestress system of the cantilever beam to reach a design value comprises the following steps:
tensioning the cantilever beam to change the prestress of the cantilever beam;
carrying out grouting construction on the cantilever beam, and adjusting the prestress of the cantilever beam so as to enable the prestress system of the cantilever beam to reach a design value;
and/or the presence of a gas in the gas,
grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the duration from the completion of slurry mixing to the pressing of the pore channel of the suspended casting beam is not more than 40 min;
and/or the presence of a gas in the gas,
grouting construction is carried out on the cantilever beam, and the prestress of the cantilever beam is adjusted, so that the prestress system of the cantilever beam reaches the design value:
the temperature of the slurry is kept between 5 and 30 ℃ during grouting.
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