CN112695633A - Prefabricated small box girder prestress engineering construction method for intelligent express way - Google Patents
Prefabricated small box girder prestress engineering construction method for intelligent express way Download PDFInfo
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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
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D2/00—Bridges characterised by the cross-section of their bearing spanning structure
- E01D2/04—Bridges characterised by the cross-section of their bearing spanning structure of the box-girder type
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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
- 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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Abstract
The invention discloses a construction method of a prefabricated small box girder prestress project for an intelligent express way, which specifically comprises the following steps: s1: construction lofting; s2: binding bottom and web plate reinforcing steel bars; s3: mounting a bottom and web prestressed pipeline; the pipeline installation is carried out synchronously with the binding of the prefabricated small box girder reinforcing steel bars; s4: installing a template; s5: binding a top plate steel bar; s6: mounting a top plate prestressed pipeline; s7: mounting an anchor plate; after the pipeline is installed, before the beam end template is sealed, the anchor plate is installed, and the anchor plate is vertically installed with the prestressed pipeline; s8: installing an end template; compared with the traditional prefabricated section beam, the number of sections is greatly reduced, and construction is simplified; the invention adopts the form of in vivo prestress, can ensure the durability of the structure by controlling the grouting quality, reduces the maintenance cost of the structure, and has the advantages of safe and convenient construction, good feasibility and high reliability.
Description
Technical Field
The invention belongs to the technical field of prestressed engineering construction, and particularly relates to a construction method of a prefabricated small box girder prestressed engineering for an intelligent express way.
Background
The small box girder prefabricated on the expressway is usually a small prestressed box girder, and prestress tensioning treatment with different strengths is required in the tensioning process of the small box girder. The tensile strength of the steel wire is different from 10% to 100%, the strength change degree of the steel wire is large in the process from the stretching of the steel wire to the strength increase, if a steel wire breakage accident occurs, the rebound force is large when the steel wire rebounds, the impact force is strong, and the life safety of field workers is seriously threatened. In the prior art, usually, in the prestress tensioning process, anti-collision soil piles are arranged at two ends of a small box girder or a special anti-collision concrete wall is constructed, and although the two methods can play a protective role to a certain extent, the whole method has the following defects: 1. the anti-collision wall is large in size and occupies an overlarge construction site; 2. the anti-collision wall is easy to damage and deform and needs irregular maintenance; 3. the anti-collision wall has higher rigidity and is easy to collapse under impact to cause secondary damage; 4. after the on-site construction of the anti-collision concrete is completed, the anti-collision concrete is difficult to treat and has great influence on the environment.
Disclosure of Invention
The invention aims to provide a pre-stressed engineering construction method of a prefabricated small box girder for an intelligent express way, which greatly reduces the number of sections and simplifies construction compared with the traditional prefabricated section girder; the invention adopts the form of in vivo prestress, can ensure the durability of the structure by controlling the grouting quality, reduces the maintenance cost of the structure, and has the advantages of safe and convenient construction, good feasibility and high reliability.
The purpose of the invention can be realized by the following technical scheme:
a prefabricated small box girder prestress engineering construction method for an intelligent express way specifically comprises the following steps:
s1: construction lofting;
s2: binding bottom and web plate reinforcing steel bars;
s3: mounting a bottom and web prestressed pipeline; the pipeline installation is carried out synchronously with the binding of the prefabricated small box girder reinforcing steel bars;
s4: installing a template;
s5: binding a top plate steel bar;
s6: mounting a top plate prestressed pipeline;
s7: mounting an anchor plate; after the pipeline is installed, before the beam end template is sealed, the anchor plate is installed, and the anchor plate is vertically installed with the prestressed pipeline;
s8: installing an end template; fixing the anchor backing plate on the template by using a positioning bolt, and sealing and wrapping the bell mouth and the pore passage of the anchor backing plate by using a waterproof raw adhesive tape and a plastic adhesive tape;
s9: pouring box girder concrete;
s10: curing the concrete;
s11: penetrating prestressed tendons; the steel strand is used as a prestressed tendon of a prefabricated small box girder, the standard size is phi s15.20mm, the standard strength is 1860MPa, and the elastic modulus is 1.95 multiplied by 105The area of the single stranded steel wire is 140mm2；
S12: anchoring; the anchorage device is a YJM15 type clamping piece type anchorage device and accessories thereof, and is matched with the prestressed pipeline;
s13: tensioning; dismantling the side mold of the box girder before prestress tensioning, and reserving the bottom mold;
s14: grouting the pipeline; the pipeline grouting adopts a vacuum grouting process, the grouting material adopts finished grouting material, and the strength grade is not less than the structural strength of the prefabricated small box girder;
s15: sealing an anchor at the beam end; the anchor sealing adopts non-shrinkage high-performance C50 fine-stone concrete, the water-cement ratio is not more than 0.4, and the thickness of the anchor sealing concrete is not less than 5 cm.
As a further scheme of the invention: in the S7 anchor plate installation construction process, the anchor plate and the prestressed pipeline are connected by adopting a special connecting joint which is in a hoop form.
As a further scheme of the invention: in the process of installing and constructing the S7 anchor plate, grouting holes of the anchor backing plate are plugged by using pipe threads with the same diameter, and a foam plate is lined between the anchor backing plate and the template.
As a further scheme of the invention: s11, before the prestressed tendon penetrating construction, keeping the pipeline dry and clean, and removing impurities in the pipeline by using an air compressor; and numbering the single steel strand and the whole steel strand to ensure that the numbers of the two ends of the prestressed tendon are the same and are consistent with the numbers of the holes of the anchorage device.
As a further scheme of the invention: in the S12 anchoring construction process, the static load test detection is carried out by using the prestressed tendons and the anchorage device assembly parts to obtain the anchorage device efficiency coefficient etaaAnd the total strain epsilon of the stress length of the assembly part when the actually measured ultimate tensile force is reachedapuAnd determining that the static load anchoring performance of the anchorage device meets the requirement.
As a further scheme of the invention: s12, in the anchoring process, the anchor and the connector are installed in the hole channel to be aligned, the exposed length of the clamping pieces is consistent, and the anchor or its accessories need to be provided with mud jacking vent holes.
As a further scheme of the invention: in the S13 tensioning construction process, the tensioning sequence of the prestressed tendons is N2 → N1 → N3 → N4, the prestressed tendons with the same number are sequentially tensioned from the middle to two sides and must be symmetrically tensioned at the same time; tensioning procedure of 0 → initial stress (0.1 σ)con) → control of tensile stress σcon→ hold for 5 minutes → anchor; the prestress tension requires double control of the extension value and the tension stress, the stress control is taken as the main control, and the extension value is taken as the check.
As a further scheme of the invention: in the S13 tensioning construction process, after tensioning is finished, the steel strand can be cut without the phenomenon of wire slipping through inspection; cutting the excessive length of the exposed prestressed tendon after tensioning by using a grinding wheel cutting machine, wherein the distance between a notch and the anchor head is 3 cm; the steel strand cutting adopts a grinding wheel cutting machine, and anchors at two ends and surrounding steel wires are protected during cutting.
As a further scheme of the invention: in the process of S14 pipeline grouting construction, the time from stirring to pressing into a pore channel is not more than 40 minutes, grouting of the same pore channel needs to be continuously carried out without interruption, and the vent holes are kept smooth; when the pore channel is blocked or grouting is interrupted due to reasons, the pore channel is timely flushed by pressure water, and a nozzle of a grouting pipe is connected with a grouting hole;
and (3) the slurry conveying pressure of the slurry pressing pump is kept at 0.7-0.8 MPa, the pressure is stabilized for more than 5 minutes, and the slurry pressing compactness is checked in time after the slurry pressing, if not, the slurry is supplemented in time.
As a further scheme of the invention: s15, in the process of beam end anchor sealing construction, after grouting of the pore channel, the slurry at the beam end is immediately washed clean, dirt of a base plate, an anchorage device and concrete at the beam end face is removed, and the beam end face is roughened;
installing an anchor sealing end reinforcing mesh, fixing an end sealing template, pouring anchor sealing concrete, and reserving an exhaust hole during anchor sealing;
and (4) sealing and curing the anchor sealing concrete by adopting a plastic film, wherein the curing time is more than or equal to 14 days.
The invention has the beneficial effects that: compared with the traditional prefabricated section beam, the construction method greatly reduces the number of sections and simplifies the construction; the invention adopts the form of in vivo prestress, can ensure the durability of the structure by controlling the grouting quality, reduces the maintenance cost of the structure, and has the advantages of safe and convenient construction, good feasibility and high reliability.
Drawings
In order to facilitate understanding for those skilled in the art, the present invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic view of the construction process of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood 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.
Referring to fig. 1, a method for constructing a prestressed engineering of a prefabricated small box girder for an intelligent express way specifically includes the following steps:
s1: construction lofting;
s2: binding bottom and web plate reinforcing steel bars;
s3: mounting a bottom and web prestressed pipeline; the pipeline installation is carried out synchronously with the binding of the prefabricated small box girder reinforcing steel bars;
s4: installing a template;
s5: binding a top plate steel bar;
s6: mounting a top plate prestressed pipeline;
when the pipeline material enters the field, the pipeline is immediately organized to enter the field for acceptance check, quality certification documents and product certificates are checked, and the pipeline material can enter the field after being confirmed to be correct. The corrugated pipe should not leak slurry, leak water, not be jointed, have certain rigidity, and have no hole and crack on the surface.
After the pipeline is qualified by the incoming inspection, the prestressed pipeline is organized and subjected to witness sampling within 3 days, and the prestressed pipeline is sent to a third-party laboratory with inspection qualification to be detected, so that the quality of the pipeline is qualified and the pipeline has use conditions.
Before construction, the prestressed pipeline is subjected to appearance quality inspection, such as the occurrence of damage, corrosion, pollution and the like on the surface of the pipeline, and the prestressed pipeline cannot be used.
The pipeline installation is carried out synchronously along with the binding of the prefabricated small box girder reinforcing steel bars, and the reworking is avoided.
The pipeline positioning is carried out according to the size of a standard steel template of the box girder and in combination with construction drawings, so that the prestressed pipeline positioning is accurate.
The connector is formed by using a large-size corrugated pipe as a connector pipe, the corrugated pipe is overlapped by 15-20 cm, and the connector is connected by hot melting.
When the prestressed pipeline collides with the box girder reinforcing steel bars in construction, the box girder reinforcing steel bars need to be adjusted, and the accuracy of the embedding position of the prestressed pipeline is ensured.
The corrugated pipe is positioned by positioning steel bars according to design coordinates. The prestressed pipeline is fixed by using a # -shaped positioning steel bar, the distance between straight line sections is 75cm, and the distance between curved line sections is 50 cm. The positioning steel bars and the beam body steel bars are welded firmly to prevent the corrugated pipe from floating upwards and the corrugated pipe from extruding and deforming in the concrete pouring process.
The corrugated pipe is prevented from being repeatedly bent in the installation and positioning process to prevent the pipe wall from cracking.
The protection of the pipeline is paid attention to in the installation process of the prestressed pipeline, and strain, damage and deformation in the pipeline construction process are prevented.
After the corrugated pipe is installed, a specially-assigned person is dispatched to check whether the position and the shape of the corrugated pipe are consistent with the design, whether the fixing is firm, whether the joint is intact, whether the pipe wall is damaged or not, and if the joint is damaged, the corrugated pipe is repaired by a method of winding adhesive tapes.
When welding operation is carried out, shielding measures need to be taken, and welding slag is prevented from scalding pipelines.
Before the box girder concrete is poured, a supervisor is requested to perform quality inspection and acceptance before pouring, and after the condition that the box girder concrete is correct is confirmed, the box girder concrete can be poured.
In the concrete pouring process, a specially-assigned person is arranged to check, such as find out pipeline damage and slurry leakage, and repair in time. The concrete is prevented from entering the pipeline, and the steel strand penetrating is prevented from being influenced.
S7: mounting an anchor plate; after the pipeline is installed, before the beam end template is sealed, the anchor plate is installed, and the anchor plate is vertically installed with the prestressed pipeline;
when the anchor plate enters the field, the anchor plate is immediately organized to enter the field for inspection and acceptance, the appearance quality of the anchor is confirmed to meet the requirements, the anchor is free of corrosion, damage, deformation and the like, the tolerance of the appearance dimension needs to meet the requirements of design and specification, quality certification documents and product qualification certificates are checked, and the anchor plate can enter the field after being confirmed to be free of errors.
After the anchor plate is qualified by incoming inspection, the tissues take witness samples of the anchor within 3 days, and the anchor is sent to a third-party laboratory with inspection qualification to be detected, so that the quality of the anchor is qualified and the anchor has use conditions.
The anchor plate and the prestressed pipeline are connected by adopting a special connecting joint which adopts a hoop form.
During installation, the position of the anchor plate is adjusted, the anchor plate is ensured to be vertically installed with the prestressed pipeline, and the angle deviation is avoided.
The joint of the anchor backing plate and the corrugated pipe is bound by adhesive tapes so as to prevent the anchor backing plate from falling off and entering mortar or concrete.
After the anchor plate is installed, the appearance quality and the sealing condition are checked, and the phenomena of pores and leakage are avoided.
S8: installing an end template; fixing the anchor backing plate on the template by using a positioning bolt, and sealing and wrapping the bell mouth and the pore passage of the anchor backing plate by using a waterproof raw adhesive tape and a plastic adhesive tape;
s9: pouring box girder concrete;
s10: curing the concrete;
s11: penetrating prestressed tendons; the steel strand is used as a prestressed tendon of a prefabricated small box girder, the standard size is phi s15.20mm, the standard strength is 1860MPa, and the elastic modulus is 1.95 multiplied by 105The area of the single stranded steel wire is 140mm2；
When the prestressed tendon enters the field, the prestressed tendon is immediately organized to enter the field for inspection and acceptance, the appearance quality is confirmed to meet the requirements, no corrosion, damage, deformation, distortion, damage and the like exist, the tolerance of the appearance dimension needs to meet the requirements of design and specification, performance indexes in quality certification documents and product quality certificates are checked, the design requirements are met, inspection items and inspection results in type inspection reports meet the requirements of the current national specification, and the prestressed tendon can enter the field after being confirmed to be free of errors.
The steel strand incoming site should be inspected and accepted in batches, each batch of steel strands is composed of steel strands twisted by the same brand, the same specification and the same production process, and the weight of each batch of steel strands is not more than 60 t.
After the prestressed tendons are qualified by entering and acceptance, witness sampling is carried out according to the requirements of national standard regulation specifications, and the prestressed tendons are sent to a third-party laboratory with the qualification for inspection to be detected, so that the prestressed tendons are qualified in quality and have use conditions.
The tendon should be kept clean for storage and should be protected from mechanical damage and detrimental corrosion during storage and handling. The storage time after entering the field is not longer than 6 months, and the product is stored in a dry, damp-proof, well-ventilated warehouse without corrosive gas and medium; when the waterproof and waterproof box is stored outdoors, the waterproof and waterproof box cannot be directly stacked on the ground, and is supported and covered to prevent rain and dew and various corrosive media from generating adverse effects on the waterproof and waterproof box.
S12: anchoring; the anchorage device is a YJM15 type clamping piece type anchorage device and accessories thereof, and is matched with the prestressed pipeline;
when the anchorage device, the clamp and the connector enter the field, the anchorage device, the clamp and the connector are immediately organized to enter the field for inspection and acceptance, the appearance quality and the dimensional deviation are confirmed to meet the requirements, no corrosion, damage, crack, deformation and the like exist, the appearance dimensional tolerance needs to meet the requirements of design and specification, quality certification documents and product certification are checked, and the anchorage device, the clamp and the connector can enter the field after being confirmed to be free of errors.
The anchorage devices are matched for use, products of the same manufacturer are used in the same component, and anchorage devices produced by different manufacturers are not mixed for use.
S13: tensioning; dismantling the side mold of the box girder before prestress tensioning, and reserving the bottom mold;
after the strength of the precast small box girder concrete reaches 100% of the designed strength and the age is not less than 10 days, tensioning the prestressed tendons can be carried out.
Before prestress tensioning, a safety warning rope is adopted for carrying out region isolation on a tensioning region, people irrelevant to tensioning operation are prohibited to enter the tensioning region, and full-time supervision is carried out on the tensioning operation by a professional safety worker.
And the jack, the oil meter and the oil pump are matched and calibrated by qualified metering departments, and a formal inspection and calibration certificate is issued and used after being inspected to be qualified.
S14: grouting the pipeline; the pipeline grouting adopts a vacuum grouting process, the grouting material adopts finished grouting material, and the strength grade is not less than the structural strength of the prefabricated small box girder;
after the grouting material enters the field, the grouting material is organized immediately to enter the field for inspection and acceptance, the appearance package, the sealing condition and the like of the grouting material are confirmed, performance indexes in quality certification documents and product certification are checked, the design requirements are met, and the grouting material can enter the field after being confirmed to be correct.
And after the pressure slurry enters a field and is qualified through inspection, carrying out witness sampling according to the requirements of national standard regulation specifications, sending the pressure slurry to a third-party laboratory with inspection qualification for detection, and confirming that the pressure slurry is qualified in quality and has use conditions.
And carrying out slurry adaptation by a third-party laboratory according to conditions such as a pore channel form, a grouting method, material performance, equipment and the like. The slurry adaptation should meet the following requirements:
the rotating speed of the testing machine during fitting is determined according to the rotating speed of a pulping machine adopted in construction, and the consistency of pulping parameters is ensured;
the intensity rating of the laboratory mix should be no less than 1.15 times the design intensity rating.
Before the grouting operation is formally carried out, the on-site process verification is carried out on the mixing ratio of a laboratory, and the performance index of grouting under the construction condition is ensured.
The prestressed pipe is flushed by pressure water before grouting to eliminate powder, slag and other impurities in the hole and ensure smooth hole passage. After washing, the accumulated water in the hole is blown away by an air compressor, but the hole channel needs to be kept moist, so that the combination of cement paste and the hole wall is ensured. In the process of flushing, if the phenomena of water overflow and water leakage are found, the leak hole is blocked in time.
The grouting adopts circulating intelligent grouting equipment, and integrates material metering, automatic mixing, slurry conveying, vacuum grouting and pressure control. The grouting pipe is connected, grouting, circulating and pressure maintaining processes can be automatically completed by pressing down the starting grouting pipe, and grouting records are generated after pressure maintaining is completed.
And grouting should be slowly and uniformly carried out, proper pressure stabilizing time is needed, after the slurry with the same fluidity as the grouting material is discharged from the exhaust hole, the slurry outlet valve is closed, and the connecting pipe and the slurry conveying pipe nozzle are closed after the load is kept for 5min, so that grouting can be stopped and the grouting hole can be closed.
S15: sealing an anchor at the beam end; the anchor sealing adopts non-shrinkage high-performance C50 fine-stone concrete, the water-cement ratio is not more than 0.4, and the thickness of the anchor sealing concrete is not less than 5 cm.
The mix proportion of the anchor sealing concrete must be tested, the strength meets the design requirement, and the anchor sealing concrete is slightly expanded to prevent the concrete from shrinking to generate cracks.
And (3) immediately washing the slurry at the beam end after grouting the pore channel, removing dirt of the base plate, the anchorage and the concrete at the beam end surface, and performing chiseling treatment on the beam end surface.
And installing a reinforcing mesh at the anchor sealing end, fixing the end sealing template, and pouring anchor sealing concrete according to the design requirement. And an exhaust hole is reserved during anchor sealing to ensure air exhaust.
The anchor sealing concrete is timely plastered and calendered, the concrete surface and the beam body concrete are not obviously staggered after the anchor is sealed, and the surface of the anchor sealing concrete needs to be plastered and calendered for three times.
And (4) sealing and curing the anchor sealing concrete by adopting a plastic film, wherein the curing time is more than or equal to 14 days.
In the S7 anchor plate installation construction process, the anchor plate and the prestressed pipeline are connected by adopting a special connecting joint which is in a hoop form.
In the process of installing and constructing the S7 anchor plate, grouting holes of the anchor backing plate are plugged by using pipe threads with the same diameter, and a foam plate is lined between the anchor backing plate and the template to prevent grouting and pipe plugging.
S11, before the prestressed tendon penetrating construction, keeping the pipeline dry and clean, and removing impurities in the pipeline by using an air compressor; and numbering the single steel strand and the whole steel strand to ensure that the numbers of the two ends of the prestressed tendon are the same and are consistent with the numbers of the holes of the anchorage device.
Before the prestressed tendons are threaded, the pipeline is kept dry and clean, and an air compressor is adopted to remove impurities in the pipeline.
In order to prevent the steel strand from being scattered and not easy to pass through, the steel strand is suitable to be manually penetrated.
When the steel bundle is longer, the steel strand is firstly braided, and then the head is wrapped by using a special tool; and finally, finishing the stringing by using a special traction tool.
In the S12 anchoring construction process, the static load test detection is carried out by using the prestressed tendons and the anchorage device assembly parts to obtain the anchorage device efficiency coefficient etaaAnd the total strain epsilon of the stress length of the assembly part when the actually measured ultimate tensile force is reachedapuAnd determining that the static load anchoring performance of the anchorage device meets the requirement.
S12, in the anchoring construction process, the anchor and the connector are installed in the pore channel to be aligned, the exposed lengths of the clamping pieces are consistent, and the anchor is tensioned in time after being installed; grouting exhaust holes are required to be arranged on the anchorage device or the accessories thereof, and the position and the size of the holes meet the grouting construction requirements of the pipeline; when the jack is installed, the tool anchor is aligned with the working anchor, and each prestressed tendon between the tool anchor and the working anchor is not dislocated or twisted.
In the S13 tensioning construction process, the tensioning sequence of the prestressed tendons is N2 → N1 → N3 → N4, the prestressed tendons with the same number are sequentially tensioned from the middle to two sides and must be symmetrically tensioned at the same time; tensioning procedure of 0 → initial stress (0.1 σ)con) → control of tensile stress σcon→ hold for 5 minutes → anchor; prestress tension requirement extension valueAnd tension stress dual control, wherein the stress control is taken as a main control, and the elongation value is taken as a check.
The prestress tension requires double control of the extension value and the tension stress, the stress control is taken as the main control, and the extension value is taken as the check. And correcting the design elongation according to the elastic modulus E' of the prestressed tendon determined by the test, and controlling the error between the actually-measured elongation and the design elongation within +/-6 percent, if the elongation value is found to be abnormal, stopping tensioning, and finding out the reason.
Calculating according to the theoretical elongation value of the prestressed tendon in the technical Specification of construction of highway bridges and culverts:
ΔLL＝PPL/APEP
PP-average tensile force (N) of the tendon;
l is the length (mm) of the prestressed tendon;
AP-cross-sectional area (mm) of tendon2)；
EP-modulus of elasticity of the tendon.
When the prestressed tendon is tensioned, the initial stress sigma should be adjusted0The initial stress is preferably a tension control stress sigmacon10% -25% of the total elongation, measured from the initial stress. Besides the measured elongation value, the actual elongation value of the prestressed tendon should be added with the calculated elongation value below the initial stress. Actual elongation value DeltaL of prestressed tendonsAnd (3) calculating:
ΔLs＝ΔL1+ΔL2
in the formula:
Δ L1 is the measured elongation (mm) from initial stress to maximum tensile stress;
Δ L2 is the estimated elongation (mm) at initial stress.
The tensioning equipment adopts intelligent tensioning equipment, the tensioning system consists of a computer, a control host and a jack, and during construction, the automatic control system is started after the anchorage device and the jack are installed in place, so that the whole tensioning operation is automatically completed, and the control, data processing and memory of the tensioning control force and the elongation of the steel strand are realized.
Before use, the tensioning equipment must be calibrated and calibrated in a matching way through qualified metering departments, and a formal verification and calibration certificate is issued and used after being qualified. And determining the relationship between the reading of the oil meter and the tension force of the jack according to the calibration, and judging whether the jack, the oil pump or the oil meter is damaged or not according to the discrete value during the calibration.
The tensioning device should be recalibrated when one of the following conditions occurs:
(1) the jack is used for more than 6 months;
(2) the stretching times exceed 300 times;
(3) the jack or the pressure gauge is abnormal in the using process;
(4) after the jack is overhauled or the accessories are replaced.
When the jack is installed, the jack, the anchor backing plate and the working anchor are concentric and perpendicular to the anchor backing plate, and oil stains are strictly prohibited on the anchorage device and the clamping piece.
Cleaning the holes of the pipeline before tensioning. The prestressed pipe is flushed by pressure water before grouting to eliminate powder, slag and other impurities in the hole and ensure smooth hole passage. After washing, the accumulated water in the hole is blown away by an air compressor, but the hole channel needs to be kept moist, so that the combination of cement paste and the hole wall is ensured. In the process of flushing, if the phenomena of water overflow and water leakage are found, the leak hole is blocked in time.
A jack and an oil meter which are calibrated during tensioning need to be matched for use, and are strictly forbidden to be mixed.
In the tensioning process, a person should be strictly prohibited from standing behind the pedestal, an operator should stand on the side face of the tensioning equipment, a full-time monitoring of a full-time safety worker is carried out in the operation process, a regional isolation warning rope is arranged, and irrelevant persons are strictly prohibited from entering the tensioning equipment.
In the whole tensioning process, a specially-assigned person makes tensioning original records, records the videos and makes image data well.
During the prestressed tensioning and anchoring process or after the anchoring is finished, the anchorage device cannot be knocked or vibrated by a large force. When the prestressed tendon is released, a special releasing device is adopted for releasing.
In the S13 tensioning construction process, after tensioning is finished, the steel strand can be cut without the phenomenon of wire slipping through inspection; cutting the excessive length of the exposed prestressed tendon after tensioning by using a grinding wheel cutting machine, wherein the distance between a notch and the anchor head is 3 cm; the steel strand cutting adopts a grinding wheel cutting machine, and anchors at two ends and surrounding steel wires are protected during cutting.
Matters to be noted in the tensioning process:
when abnormal conditions are found during tensioning, a 'pause tensioning' button is pressed immediately, and the reason is searched and analyzed.
During tensioning, the tensioning is monitored by a special quality inspector side station and is strictly carried out symmetrically step by step according to a designed tensioning sequence. And recording the reading value of the pressure gauge and the elongation value of the steel strand carefully, and checking whether the wire is broken or not and the wire is slippery.
In the process of S14 pipeline grouting construction, the time from stirring to pressing into a pore channel is not more than 40 minutes, grouting of the same pore channel needs to be continuously carried out without interruption, and the vent holes are kept smooth; when the pore channel is blocked or grouting is interrupted due to reasons, the pore channel is timely flushed by pressure water, and a nozzle of a grouting pipe is connected with a grouting hole;
and (3) the slurry conveying pressure of the slurry pressing pump is kept at 0.7-0.8 MPa, the pressure is stabilized for more than 5 minutes, and the slurry pressing compactness is checked in time after the slurry pressing, if not, the slurry is supplemented in time.
And in the grouting process and within 48 hours after grouting, the temperature of the concrete of the member and the ambient temperature are not lower than 5 ℃, otherwise, heat preservation measures are adopted and are processed according to the construction requirements in winter, but the anti-freezing agent cannot be mixed in the grout. When the ambient temperature is higher than 35 ℃, the grouting is preferably carried out at night.
And maintaining in time after grouting. The box girder is not moved when the grouting is not carried out or the strength of the cement paste does not reach the specified strength.
At least three groups of standard test pieces (40X 160mm) must be reserved for each grouting, standard curing is carried out for 28 days, and the compressive strength and the flexural strength of the grouting are used as the quality evaluation basis of the cement paste.
Quality control considerations:
before grouting, an air compressor is used for removing moisture or dirt remained in a pipeline, so that the vacuum auxiliary grouting work can be smoothly carried out;
the air tightness of the whole communication pipeline needs to be carefully checked, and the next procedure can be carried out after the communication pipeline is qualified;
when the slurry is stirred, the dosage of water, cement and additive must be strictly controlled;
the water consumption must be strictly controlled, and for cement paste which is not used in time and has reduced fluidity, a method of adding water is strictly forbidden to increase the fluidity of the cement paste; the slurry stirred in the stirrer should be completely discharged each time, and before the slurry is completely discharged, the material which is not stirred cannot be put in, and a method of discharging and feeding the slurry cannot be adopted.
S15, in the process of beam end anchor sealing construction, after grouting of the pore channel, the slurry at the beam end is immediately washed clean, dirt of a base plate, an anchorage device and concrete at the beam end face is removed, and the beam end face is roughened;
installing an anchor sealing end reinforcing mesh, fixing an end sealing template, pouring anchor sealing concrete, and reserving an exhaust hole during anchor sealing;
and (4) sealing and curing the anchor sealing concrete by adopting a plastic film, wherein the curing time is more than or equal to 14 days.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (10)
1. A construction method of a prefabricated small box girder prestress engineering for an intelligent express way is characterized by comprising the following steps:
s1: construction lofting;
s2: binding bottom and web plate reinforcing steel bars;
s3: mounting a bottom and web prestressed pipeline; the pipeline installation is carried out synchronously with the binding of the prefabricated small box girder reinforcing steel bars;
s4: installing a template;
s5: binding a top plate steel bar;
s6: mounting a top plate prestressed pipeline;
s7: mounting an anchor plate; after the pipeline is installed, before the beam end template is sealed, the anchor plate is installed, and the anchor plate is vertically installed with the prestressed pipeline;
s8: installing an end template; fixing the anchor backing plate on the template by using a positioning bolt, and sealing and wrapping the bell mouth and the pore passage of the anchor backing plate by using a waterproof raw adhesive tape and a plastic adhesive tape;
s9: pouring box girder concrete;
s10: curing the concrete;
s11: penetrating prestressed tendons; the steel strand is used as a prestressed tendon of a prefabricated small box girder, the standard size is phi s15.20mm, the standard strength is 1860MPa, and the elastic modulus is 1.95 multiplied by 105The area of the single stranded steel wire is 140mm2；
S12: anchoring; the anchorage device is a YJM15 type clamping piece type anchorage device and accessories thereof, and is matched with the prestressed pipeline;
s13: tensioning; dismantling the side mold of the box girder before prestress tensioning, and reserving the bottom mold;
s14: grouting the pipeline; the pipeline grouting adopts a vacuum grouting process, the grouting material adopts finished grouting material, and the strength grade is not less than the structural strength of the prefabricated small box girder;
s15: sealing an anchor at the beam end; the anchor sealing adopts non-shrinkage high-performance C50 fine-stone concrete, the water-cement ratio is not more than 0.4, and the thickness of the anchor sealing concrete is not less than 5 cm.
2. The pre-stressed engineering construction method for the prefabricated small box girder of the intelligent express way as claimed in claim 1, wherein during the installation construction of the S7 anchor plate, the anchor plate and the pre-stressed pipeline are connected by a special connector in the form of a hoop.
3. The pre-stressed engineering construction method for the prefabricated small box girder of the intelligent express way as claimed in claim 1, wherein during the installation construction of the S7 anchor slab, grouting holes of the anchor slab are plugged by using the same-diameter pipe thread, and a foam slab is lined between the anchor slab and the formwork.
4. The pre-stressed engineering construction method for the prefabricated small box girder of the intelligent express way is characterized in that before the S11 pre-stressed tendon penetrating construction, the pipeline is kept dry and clean, and an air compressor is adopted to remove impurities in the pipeline; and numbering the single steel strand and the whole steel strand to ensure that the numbers of the two ends of the prestressed tendon are the same and are consistent with the numbers of the holes of the anchorage device.
5. The pre-fabricated small box girder pre-stressed engineering construction method for intelligent express way as claimed in claim 1, wherein in the anchoring construction process of S12, the pre-stressed tendons and the anchorage assembly parts are used for static load test detection, and the anchorage efficiency coefficient η is usedaAnd the total strain epsilon of the stress length of the assembly part when the actually measured ultimate tensile force is reachedapuAnd determining that the static load anchoring performance of the anchorage device meets the requirement.
6. The pre-fabricated small box girder pre-stressed engineering construction method for the intelligent express way as claimed in claim 1, wherein in the S12 anchoring construction process, the anchor and the connector are installed in the hole channel to be aligned, the exposed length of the clip pieces is consistent, and the anchor or its accessories are required to be provided with grouting exhaust holes.
7. The pre-fabricated small box girder pre-stressed engineering construction method for the intelligent express way as claimed in claim 1, wherein in the S13 tensioning construction process, the tensioning sequence of the pre-stressed tendons is N2 → N1 → N3 → N4, the pre-stressed tendons with the same number are sequentially tensioned from the middle to both sides and must be symmetrically tensioned at the same time; tensioning procedure of 0 → initial stress (0.1 σ)con) → control of tensile stress σcon→ hold for 5 minutes → anchor; the prestress tension requires double control of the extension value and the tension stress, the stress control is taken as the main control, and the extension value is taken as the check.
8. The pre-fabricated small box girder pre-stressed engineering construction method for the intelligent express way as claimed in claim 1, wherein in the S13 tensioning construction process, after tensioning is completed, a steel strand can be cut through checking that no wire sliding occurs; cutting the excessive length of the exposed prestressed tendon after tensioning by using a grinding wheel cutting machine, wherein the distance between a notch and the anchor head is 3 cm; the steel strand cutting adopts a grinding wheel cutting machine, and anchors at two ends and surrounding steel wires are protected during cutting.
9. The pre-stressed engineering construction method for the prefabricated small box girder of the intelligent express way is characterized in that in the S14 pipeline grouting construction process, the time from the completion of stirring to the pressing into the pore channel of the grout does not exceed 40 minutes, the grouting of the same pore channel needs to be continuously carried out without interruption, and the vent holes are kept open; when the pore channel is blocked or grouting is interrupted due to reasons, the pore channel is timely flushed by pressure water, and a nozzle of a grouting pipe is connected with a grouting hole;
and (3) the slurry conveying pressure of the slurry pressing pump is kept at 0.7-0.8 MPa, the pressure is stabilized for more than 5 minutes, and the slurry pressing compactness is checked in time after the slurry pressing, if not, the slurry is supplemented in time.
10. The pre-stressed engineering construction method for the prefabricated small box girder of the intelligent express way is characterized in that in the process of S15 beam end anchor sealing construction, slurry at the beam end is washed clean immediately after grouting of a pore channel, dirt of a backing plate, an anchor and concrete at the beam end is removed, and the beam end face is roughened;
installing an anchor sealing end reinforcing mesh, fixing an end sealing template, pouring anchor sealing concrete, and reserving an exhaust hole during anchor sealing;
and (4) sealing and curing the anchor sealing concrete by adopting a plastic film, wherein the curing time is more than or equal to 14 days.
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| CN113403952A (en) * | 2021-06-25 | 2021-09-17 | 中铁十二局集团有限公司 | Railway continuous beam prestress construction method |
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