CN112458915A - Construction method of bent cap - Google Patents
Construction method of bent cap Download PDFInfo
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- CN112458915A CN112458915A CN202011366835.0A CN202011366835A CN112458915A CN 112458915 A CN112458915 A CN 112458915A CN 202011366835 A CN202011366835 A CN 202011366835A CN 112458915 A CN112458915 A CN 112458915A
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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
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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
- E01D19/00—Structural or constructional details of bridges
Abstract
The invention discloses a construction method of a bent cap, which comprises the steps of firstly determining the construction position of the bent cap, and erecting a bracket according to the construction position, wherein the bracket is used for supporting the upper load during the construction of the bent cap; and then laying a bottom die of the cover beam on the erected support and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework, so that a side die is laid on the reinforcement framework and concrete of the cover beam is poured, and after the cover beam reaches a preset strength, the side die, the bottom die and the support are sequentially detached to complete construction of the cover beam. In other words, in this embodiment, the bottom mold and the side mold of the capping beam are cast to improve the bearing capacity of the capping beam.
Description
Technical Field
The invention relates to the technical field of bridge engineering, in particular to a construction method of a bent cap.
Background
Along with the vigorous development of urban bridge construction engineering, the construction quality and progress requirements of bridge construction are gradually improved, at present, only bridge deck continuity is adopted for the bent cap construction of the bridge, although the construction method is rapid and can save a large amount of time and cost, the bearing capacity of the whole bent cap structure can be ensured only by specially processing the bent cap joint.
Disclosure of Invention
The invention mainly aims to provide a construction method of a bent cap, aiming at improving the bearing capacity of the bent cap.
In order to achieve the above object, the present invention provides a construction method of a bent cap, including:
determining the construction position of the bent cap, and setting up a support according to the construction position, wherein the support is used for supporting the load of the upper part during the construction of the bent cap;
laying a bottom die of the cover beam on the erected support, and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework;
paving side molds on the steel bar framework, and pouring concrete of the cover beam;
and after the bent cap reaches the preset strength, sequentially detaching the side die, the bottom die and the support to complete the construction of the bent cap.
Further, after the step of laying the bottom die of the bent cap on the erected bracket and binding the steel reinforcement framework of the cast-in-place box girder to form a steel reinforcement framework, the method further comprises the following steps:
penetrating a prestressed pipe into the steel bar framework, wherein a prestressed steel strand is arranged in the prestressed pipe;
after the bent cap reaches preset intensity, demolish in proper order the side form the die block and the support, in order to accomplish the step of bent cap's construction includes:
after the bent cap reaches a preset strength, sequentially dismantling the side die, the bottom die and the bracket;
after the side die, the bottom die and the support are disassembled, performing tension test on the prestressed steel strand;
and if the tension test meets the construction requirements, finishing the construction of the cover beam.
Further, the prestressed steel strand is a high-strength low-relaxation steel strand.
Further, if the tension test meets the construction requirements, after the step of completing the construction of the capping beam, the method further comprises the following steps:
if the tension test meets the construction requirements, erecting a prefabricated box girder below the cover beam, and performing a second tension test on the prestressed steel strand;
and if the second tensioning test meets the construction requirements, finishing the construction of the cover beam.
Further, if the second tensioning test meets the construction requirements, the step of completing the construction of the cover beam further comprises:
and if the second tensioning test meets the construction requirements, grouting and sealing the hole channel on the bent cap to finish the construction of the bent cap.
Further, after the step of paving the side forms on the steel reinforcement framework and pouring the concrete of the cover beam, the construction method of the cover beam further comprises the following steps:
curing and equi-strengthening the bent cap;
and if the concrete of the cover beam reaches a first preset strength, the side die is disassembled.
Further, if the bent cap reaches a first preset strength, after the step of removing the side form, the method further includes:
after the side mold is disassembled, the bent cap is maintained and has equal strength;
and if the cover beam reaches second preset strength, removing the bottom die and the support.
Further, the step of determining the construction position of the bent cap and setting up the bracket according to the construction position comprises:
and determining the construction position of the cover beam, and sequentially installing a bearing platform top embedded part, a steel pipe column, a first distribution beam, a Bailey beam and a second distribution beam at the construction position so as to complete the erection of the bracket.
Further, the first distribution beam is a double-spliced 40b I-steel, and the second distribution beam is a 40b I-steel or a 25b I-steel.
Further, the step of laying the side forms on the steel reinforcement framework further comprises the following steps:
and sealing the joint between the bottom die and the side die by using a sponge strip.
According to the construction method of the bent cap, the construction position of the bent cap is determined, and a support is erected according to the construction position, wherein the support is used for supporting the upper load during construction of the bent cap; and then laying a bottom die of the cover beam on the erected support and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework, so that a side die is laid on the reinforcement framework and concrete of the cover beam is poured, and after the cover beam reaches a preset strength, the side die, the bottom die and the support are sequentially detached to complete construction of the cover beam. In other words, in this embodiment, the bottom mold and the side mold of the capping beam are cast to improve the bearing capacity of the capping beam.
Drawings
Fig. 1 is a schematic flow chart of a construction method of a capping beam according to a first embodiment of the present invention;
FIG. 2 is a schematic view of the attachment of the bent cap to the bracket according to the present invention;
fig. 3 is a schematic flow chart of a construction method of a bent cap according to a second 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
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Because the existing capping beam construction of the bridge only adopts continuous bridge floors, although the construction method is rapid and can save a large amount of time and cost, the bearing capacity of the whole capping beam structure can be ensured only if the capping beam joint needs to be specially treated.
Therefore, the main solution of the embodiment of the invention is to determine the construction position of the bent cap first, and set up a bracket according to the construction position, wherein the bracket is used for supporting the upper load when the bent cap is constructed; and then laying a bottom die of the cover beam on the erected support and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework, so that a side die is laid on the reinforcement framework and concrete of the cover beam is poured, and after the cover beam reaches a preset strength, the side die, the bottom die and the support are sequentially detached to complete construction of the cover beam. In other words, in this embodiment, the bottom mold and the side mold of the capping beam are cast to improve the bearing capacity of the capping beam.
The invention provides a construction method of a bent cap.
Referring to fig. 1, fig. 1 is a flowchart illustrating steps of a first embodiment of a construction method of a capping beam according to the present invention, the construction method of the capping beam including:
s10, determining the construction position of the bent cap, and setting up a support according to the construction position, wherein the support is used for supporting the upper load when the bent cap is constructed;
in this embodiment, the construction position of the bent cap is determined first. For example, the construction position of the bent cap is arranged at the seaport of the western village port in north sea city, the terrain is low and gentle, and the ground elevation is as follows: 0.64m to 1.1m in the riverbed, and the deepest position of the channel can reach 1.5 m; the elevation of the land on the two sides is between 3.0 and 4.5 meters. The cause of the rock and soil of the proposed construction field is mainly clay, silty clay and sandy soil formed by the action of quaternary scouring, flooding and coastal sedimentation, and artificial fill layers with the thickness of 3-4 m are distributed on both banks. In addition, the influence of local weather, hydrology and underground water on construction engineering, risk analysis and corrosivity of site water and soil are required to be evaluated so as to accurately determine the construction position of the capping beam.
And further, after the construction position of the bent cap is determined, a support is erected according to the construction position, and the support is used for supporting the load of the upper part during construction of the bent cap.
Specifically, as shown in fig. 2, the support includes a bearing platform top embedded part 1, a steel pipe column 2, a first distribution beam 3, a bery beam 4, and a second distribution beam 5, which are sequentially arranged from bottom to top, that is, the construction position of the cap beam is determined, and the bearing platform top embedded part 1, the steel pipe column 2, the first distribution beam 3, the bery beam 4, and the second distribution beam 5 are sequentially installed at the construction position to complete the erection of the support. The principle of the bracket design in this embodiment: the concrete has enough rigidity, strength and stability, and can reliably bear construction load, side pressure and other construction loads during concrete pouring; the shape, size, elevation and mutual position of each part of the engineering structure are ensured to be accurate, and the engineering structure meets the design requirements; the structure is simple, the assembly and disassembly are convenient, the construction is convenient, the splicing seam is tight, and the process requirements of pouring, curing and the like of concrete are met.
The embedded part 1 at the top of the bearing platform is an embedded 1800 x 800 x 20mm steel plate on the bearing platform, and 8 phi 20 anchoring steel bars are welded at the bottom of the steel plate for fixing; the steel pipe column 2 is made of steel pipes with the diameter of 630mm multiplied by 10mm, the bottom of the steel pipe column is firmly welded with the base steel plate, 2 steel pipe columns are arranged on two sides of the steel pipe column 2 respectively, the height of the steel pipe column 2 exceeding 6m is provided with longitudinal connection at the position 4.5m away from the top of the bearing platform, the height of the steel pipe column 2 exceeding 10m is provided with two longitudinal connections at the position 4.5m and 9m away from the top of the bearing platform, and the longitudinal connection is a steel pipe with the diameter of 325 multiplied by 8 mm.
Further, in order to reduce the concentrated stress on the top of the steel pipe column 2 and ensure that the top of the steel pipe column 2 is uniformly stressed, reinforcing ribs are welded to the top surface of the steel pipe column 2 by using steel plates and triangular iron, wherein the steel plates are 800 × 20mm, the reinforcing ribs are 20mm thick steel plates, the reinforcing ribs are arranged around the steel plates, and the number of the reinforcing ribs is eight in the embodiment.
Further, two 12-meter-long double-spliced 40b I-shaped steel beams serving as the first distribution beam 3 are arranged at the top end of the steel pipe column 2 in the transverse bridge direction, and the first distribution beam 3 is horizontally arranged. In order to facilitate demoulding and frame dropping, 8 50-ton screw jacks are arranged on the I-beam, two Bailey beams 4 are transversely arranged at the upper ends of the jacks, the Bailey beams 4 are connected by using 75-degree steel, meanwhile, the Bailey beams 4 on two sides are reinforced and connected by using 25b I-beams and U-shaped bolts, and three transverse bridge sides are connected. And laying 25b I-beams on the tops of the Bailey beams 4 to serve as second distribution beams 5, wherein the second distribution beams 5 are arranged in a plurality, and the distance between two adjacent second distribution beams 5 is 60 cm. .
Of course, in other embodiments, the second distribution beam 5 may also be a 40b i-steel.
Furthermore, after the support is erected, the second distribution beam 5 is used as a working platform, a 5cm formwork is laid on the upper layer, the protective railings are installed along the periphery of the I-shaped steel, and a safety net is hung to prevent the falling phenomenon.
S20, laying a bottom die of the cover beam on the erected support, and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework;
s30, paving side forms on the steel bar framework, and pouring concrete of the cover beam;
in this embodiment, the bottom die is hung on the second distribution beam 5, and in addition, the joint and the distance between the two sides of the template and the central axis during the hoisting of the bottom die meet the construction requirements, so that the accuracy of the installation position of the bottom die is ensured.
And binding a steel bar framework of the cast-in-place box girder after the bottom die is hoisted to form a steel bar framework.
The reinforcing bar engineering of this embodiment needs to pay attention to: after the support pre-pressing is finished, cleaning a bottom die, setting the pre-camber according to the support pre-pressing result, and filling glass cement or sticking adhesive tapes in gaps of the template; the prefabricated C50 cushion blocks are well padded on the bottom layer of the bottom plate, the cushion blocks are arranged in a quincunx manner, the number of the cushion blocks is not less than 4 per square meter, and the protective layer is not less than 35 mm; the steel bars with the diameter larger than 20mm are connected by a sleeve, the rest steel bars are connected by welding, and the welding length requires that double-sided welding is not less than 5d and single-sided welding is not less than 10 d; during welding, attention is paid to the current and welding slag treatment, template protection is carried out, water is led to the beam surface by a water pipe, and the bottom die is kept wet at any time to prevent fire hazard and clean the beam bottom; binding the reinforcing steel bars strictly according to the design specification, binding the reinforcing steel bars by using binding wires, and arranging the reinforcing steel bars in a plum blossom shape; the binding wire is bent to the inner side, and the protective layer is prevented from extending out; the steel bars are required to have delivery quality certificates and test report sheets, the steel bars are inspected according to the condition that each batch is not more than 60t when entering a construction site, and the steel bars of the same manufacturer, the same batch number, the same variety and the same specification are inspected in one batch. The product can be used after being qualified; the surface of the steel bar should be clean, and before processing, surface oil fester, paint skin, scale rust and the like should be removed. The steel bars should be straight without local bending, and the coiled steel bars and the bent steel bars should be aligned.
Furthermore, after the reinforcing steel bar framework is formed, the side molds are installed, the demolding agent is coated before hoisting, then the side molds are hoisted by a crane in sequence to be integrally assembled, in order to ensure the integral stability of the side molds, after the side molds are integrally assembled, stiffening and counter-pulling screw rods are installed, the sealing performance of the splicing seams and the protective layer of a reinforcing steel bar framework are ensured when the side molds are assembled, slurry leakage and rib exposure are prevented, and the plane position of the beam is covered by a measuring team after the side molds are installed.
Namely, the bottom die is directly paved on the second distribution beam 5 by adopting a shaped steel template, and then the side die is installed. The elevation of the bottom plate needs to be accurately measured when the I-steel and the bottom die are laid, and the pier top of the hollow pier in the embodiment adopts a platform for erecting the bottom die by the I-steel, the square wood and the bamboo plywood.
Furthermore, the side die and the bottom die are spliced and connected in a mode of clamping the bottom by the aid of the side walls, and the joint between the bottom die and the side die is sealed by the sponge strips to prevent slurry leakage. And after the side die and the bottom die are installed, the plane position, the top elevation, the contact connection and the stability of the side die and the bottom die are checked, the inspection and acceptance of an administrative engineer are reported after the self-inspection is qualified, and the next procedure construction can be carried out after the inspection and acceptance are qualified.
The side mold and the bottom mold are erected accurately, particularly the geometric dimensions, the axial line positions, the firmness and the aesthetic degree of the side mold and the bottom mold, and a specially-assigned person is arranged to frequently check the positions of the template and the embedded steel bars and the dimensions of the protective layer when concrete is poured, so that the position is ensured to be correct and not to deform, and the purposes of no mold running, no slurry leakage and no dislocation are achieved. When concrete is poured, the conditions of templates, supports, caulking and the like are observed frequently.
And further, after the side die and the bottom die are installed, pouring concrete of the cover beam. The concrete is intensively mixed according to the designed mixing proportion by a mixing station and is transported to the site by a tank truck, the concrete is pumped into the side die and the bottom die by a pump truck, and the concrete is vibrated by an inserted vibrator in a stirring mode.
Furthermore, when pouring, the concrete at the lower part of the cover beam is symmetrically poured from the pier top position, then the concrete is poured towards two sides, the concrete is continuously poured, the concrete is horizontally layered and poured at one time, and the thickness of each layer is not more than 30 cm. Wherein, the interval time of the upper layer and the lower layer is as follows: when the temperature is below 30 ℃, the temperature is not more than 1.5 h; when the temperature is above 30 ℃, the temperature is not more than 1h, so that the upper layer concrete is poured before the lower layer concrete is initially set or can be remolded.
In order to ensure the appearance quality of the cover beam pouring concrete, the slump of the concrete is strictly controlled between 160mm and 200 mm. The free-fall height of the cast concrete must not exceed 1.5m in order to avoid segregation. The concrete is poured from bottom to top in a layered mode with the thickness of 30cm, and pouring is carried out in a mode of pouring while vibrating.
Further, after concrete pouring is finished, geotextile is covered for curing, after the side die and the bottom die are detached, geotextile with strong water saturation material is used for sprinkling water, the geotextile is comprehensively contacted and wrapped on the surface of the concrete, and water is properly sprinkled according to the temperature condition, so that the surface of the concrete is kept moist, and the curing period is not less than 7 days.
S40, after the bent cap reaches the preset strength, sequentially detaching the side die, the bottom die and the support to complete the construction of the bent cap;
in other words, in this embodiment, after the bent cap reaches the predetermined strength, the side die, the bottom die, and the support are sequentially removed to complete the construction of the bent cap.
Specifically, pouring the concrete of bent cap, it is right the bent cap keeps in good health and the uniform strength, if the concrete of bent cap reaches first predetermined intensity, then demolishs the side form, and the back is demolishd to the side form, it is right the bent cap keeps in good health and the uniform strength, if the bent cap reaches second predetermined intensity, then demolishs the die block and the support.
In the embodiment, the construction position of the bent cap is determined, and a support is erected according to the construction position, wherein the support is used for supporting the upper load when the bent cap is constructed; and then laying a bottom die of the cover beam on the erected support and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework, so that a side die is laid on the reinforcement framework and concrete of the cover beam is poured, and after the cover beam reaches a preset strength, the side die, the bottom die and the support are sequentially detached to complete construction of the cover beam. In other words, in this embodiment, the bottom mold and the side mold of the capping beam are cast to improve the bearing capacity of the capping beam.
Based on the above embodiment, the present invention proposes a second embodiment of the construction method of the capping beam.
As shown in fig. 3, fig. 3 is a flowchart illustrating steps of a construction method of a bent cap according to a second embodiment of the present invention, and specifically, after the step of laying a bottom mold of the bent cap on the erected support and binding a steel framework of a cast-in-place box girder to form a steel framework, the method further includes:
s21, penetrating a prestressed pipe into the steel bar framework, wherein a prestressed steel strand is arranged in the prestressed pipe;
after the steel reinforcement framework is formed, a prestressed pipe penetrates through the steel reinforcement framework, and after the prestressed pipe is installed and fixed, a prestressed steel strand penetrates through the prestressed pipe.
Specifically, the prestressed pipe adopts a metal prestressed pipe, and the inner diameter is 90 mm. The prestressed pipe is installed while binding the reinforcing steel bars, the joint adopts a large-size prestressed pipe, each side of the joint is lapped by 15cm, the joint needs to be symmetrically screwed, and the joint is sealed by using an adhesive tape or cold-shrinkable plastic to prevent concrete slurry from being mixed. The prestressed pipeline is fixed by C10 positioning steel bars, and the positioning steel bars for fixing the pipeline are firm and stable, so that the pipeline does not displace in the concrete pouring process. The positioning steel bars are in spot welding close to the pipeline and the beam body steel bars in a U-shaped mode, and are arranged at intervals of 30cm strictly according to the distance of 50cm of the straight line sections and the distance of 30cm of the curve sections; to ensure smooth turning. The placed pipeline is smooth and has no break angle, and the deviation of the pipeline axis after positioning is not more than 5 mm. And phi 16 collapse-proof steel bars are arranged in the vertical bending arc curve section of the P anchor end of the tensioning steel bundle at one end of the bottom plate at an interval of 15 cm. Electric welding operation is strictly forbidden around the prestressed pipe, and the pipe wall is prevented from being scalded by electric welding sparks. When the prestressed duct conflicts with the position of the common steel bar, the position of the common steel bar can be properly adjusted. And (4) arranging the prestressed duct strictly according to the position of a design drawing.
Wherein, the prestressed steel strand adopts A15.2mm high-strength low-relaxation steel strand which accords with GB/T5224 national standard. The prestressed steel strand adopts a field blanking processing mode. The method comprises the following steps of strictly blanking according to requirements, wherein the minimum blanking length is calculated according to the length of a pore passage and is +160cm, the blanking size error is not more than (+100mm and-50 mm), the blanking is cut by a disc cutting machine, electric arc cutting is not required, and the prestress steel strand is not required to be influenced by high temperature, welding sparks or grounding current. The cut steel strand should be combed, straightened and braided without loose ends. After each bundle of steel strands is discharged, length and number signboards are hung at two ends of the steel strand bundle and are stored in a classified mode, the steel strand bundle cannot be dragged on the ground during transportation, and the steel strand bundle is required to be lifted off the ground during storage, so that the steel strand bundle is rust-proof and corrosion-proof. Before the prestress is penetrated, whether the serial number of the penetrated pipeline and the steel bundle are consistent with the design or not should be checked to prevent the wrong penetration. The steel bundle with rust pit can not be stretched in the hole. The exposed lengths of the two ends of the prestressed steel strand after penetrating into the pore canal are equal.
Further, the box girder prestress pore channel is designed to be in a straight line and curve form. Before concrete pouring, a prestressed steel strand bundle penetrates into the prestressed pipe, and a steel strand penetrating machine is adopted for penetrating the prestressed steel strand bundle. The bundling process is as follows:
the installed steel strand is tied and hung on an operation platform at the end of the beam; and (5) installing the reeving machine in place and manually reeving. Wrapping the head of each strand of steel strand, and directly penetrating the steel strands into the hole one by one; one end of the steel strand head passes through a reeving machine; starting a power supply of the reeving machine, and starting the reeving machine to work; when the steel strand penetrates to the other end of the beam and reaches the required exposed length of the steel strand, the power supply controller closes the power supply of the reeving machine to complete reeving of the steel strand; and (5) penetrating all the prestressed tendons in the same step.
In the embodiment, the prestressed steel strand pipeline is inspected one by one after the strand is threaded, if a hole is found in the prestressed pipe and the joint is damaged, the prestressed steel strand pipeline is wrapped and repaired in time in a loosening manner, and the next procedure can be performed after the prestressed steel strand pipeline is determined to be free of errors.
Meanwhile, the installation of the embedded part comprises the installation of the ventilation pipes on two sides and the installation of the drain holes on the bottom of the beam. The ventilation pipes on two sides are installed, ventilation holes with the diameter of 100mm are arranged on two sides of the structure in a staggered mode, if the ventilation holes collide with the prestressed steel strands, the positions of the ventilation holes are moved appropriately, the net protection layer of the ventilation holes and the prestressed steel strands is guaranteed to be larger than 1 time of the diameter of the prestressed pipeline, a reinforcing steel bar ring with the diameter of 150mm is additionally arranged at the ventilation hole, and a PVC cross grid net is arranged at the hole opening; the beam bottom drainage holes are arranged in the positions, away from the side pier beam end by 4m, 3.5m away from the middle pier, of each box chamber, and the beam bottom longitudinal bridge of the cover beam is provided with 2 drainage holes with the diameter of 10 cm. When the device is installed, the pipe is ensured to be tightly attached to the bottom die, the top opening is 10cm higher than the top surface of the designed bottom plate, the top opening is sealed by plastic adhesive tape, a spiral rib is additionally arranged, and waterproof treatment is paid attention to at the position of the drain hole.
Further, after the bent cap reaches preset intensity, the side die, the bottom die and the support are sequentially detached to complete the construction steps of the bent cap, including:
after the bent cap reaches a preset strength, sequentially dismantling the side die, the bottom die and the bracket; after the side die, the bottom die and the support are disassembled, performing tension test on the prestressed steel strand; and if the tension test meets the construction requirements, finishing the construction of the cover beam.
If the tension test meets the construction requirement, after the step of constructing the cover beam is completed, erecting a prefabricated box beam below the cover beam and carrying out a second tension test on the prestressed steel strand if the tension test meets the construction requirement; and if the second tensioning test meets the construction requirements, finishing the construction of the cover beam.
In addition, if the second tensioning test meets the construction requirement, the step of completing the construction of the bent cap further comprises the step of grouting and sealing the anchor of the pore passage on the bent cap to complete the construction of the bent cap if the second tensioning test meets the construction requirement.
And further, after the secondary tensioning of the bent cap is finished, grouting and anchoring the pore channel on the bent cap. Before grouting, cutting off redundant steel strands by using an electric hand-held sand wheel until the distance between the redundant steel strands and the anchor plug layer part is 2-3 cm, adding 42.5 common Portland cement and fine sand with the grain diameter smaller than 0.3cm, properly adding water according to the proportion of 1:1.5, uniformly stirring, keeping the core fine, blowing accumulated water in a pore passage by using high-pressure air after manual crack blocking, grouting from a lower pore passage to an upper pore passage in sequence, strictly controlling the water-cement ratio, wherein the water-cement ratio is not more than 0.35, allowing an expanding agent to be doped, controlling the consistency of cement slurry to be 14-18, performing piston grouting, ensuring that the time from stirring to pore passage pressing of the cement slurry is not more than 40min, and pressing in while stirring. And pressing the grouting from the grouting end until full thick grout is sprayed from the grout outlet, and closing the grouting valve when the pressure is increased to 0.6-0.7 MPa. And after the grouting liquid is compacted, removing the grouting pipe valve, and pouring anchor end sealing concrete to the anchor end reinforcing steel bars through a vertical mold.
Wherein, before the mud jacking, still need to do the following work:
a. cutting the outer steel wire of the anchor: the redundant prestressed tendons outside the exposed anchor are required to be cut, and if the cutting is adopted, a cooling measure is adopted, so that the phenomenon that the prestressed tendons and the anchor are overheated to generate thread slipping is avoided. The residual length of the prestressed tendon after cutting is not more than 2 cm;
b. sealing an anchor: the gaps of the prestressed tendons outside the anchorage device are filled with epoxy resin mortar or cotton and cement paste so as to prevent grouting pressure loss caused by grout bleeding, and vent holes are reserved during anchor sealing;
c. the pressure water is applied to the flushing pore channel before grouting to remove impurities in the pore channel and ensure smoothness: after washing, the accumulated water in the hole is blown away by an air compressor, but the hole channel is ensured to be wet, so that the cement paste is well combined with the hole wall. In the process of flushing, if water leakage and water leakage are found, the leak should be blocked in time;
further, the grouting process in this embodiment includes
a. When the pore canal grouting is performed sequentially, the holes concentrated at one position are pressed once, the curve pore canal is pressed in from the grouting hole at the lowest point, and the exhaust hole with the highest point exhausts air and bleeds water;
b. a short pipe with a valve is arranged on the anchor plug and the grout inlet and outlet at the two ends of each grouting pore channel for sealing after grouting and keeping the cement grout in the pore channel to be coagulated under pressure;
c. after the prestressed tendons are tensioned, grouting should be carried out on the pore channels as early as possible, and the pore channels are generally not more than 14 d;
d. the grouting should use the piston type grouting pump, must not use the compressed air;
e. in order to check the actual density of the cement slurry in the pore canal, the compaction condition of the grouting should be checked from the check hole after grouting, and if the grouting is not compact, the grouting should be timely treated and corrected; while cement paste is mixed, a standard test block is manufactured, and the maintenance can be cancelled after the standard test block is maintained to 20Mpa under the same condition with the member;
f. when the pore canal is grouted, workers need to wear protective glasses so as to prevent cement slurry from spraying eyes. Filling the construction records carefully after grouting;
and after the pore canal is grouted, the cement at the beam end is washed clean, the dirt of the support base plate, the anchorage device and the end face concrete is removed, and the end face concrete is chiseled for pouring the end-sealed concrete. The pouring process of the end-capped concrete is as follows:
a. and arranging an end reinforcing mesh. In order to fix the position of the reinforcing mesh, part of the stirrups can be spot-welded on the supporting plate;
b. the strength of the end-blocking concrete is required to meet the design specification, and if the design is random and timing, the strength is not lower than 80% of the standard value of the concrete strength of the beam body;
c. when the end-sealing concrete is poured, careful operation and careful tamping are required to ensure that the concrete at the anchorage device is compacted;
d. and (3) after the end-capped concrete is poured, standing for 1-2 h, and watering and curing with a mold. And after demoulding, the general curing time is not less than 7 days and nights at normal temperature.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The construction method of the bent cap is characterized by comprising the following steps:
determining the construction position of the bent cap, and setting up a support according to the construction position, wherein the support is used for supporting the load of the upper part during the construction of the bent cap;
laying a bottom die of the cover beam on the erected support, and binding a reinforcement framework of the cast-in-place box beam to form a reinforcement framework;
paving side molds on the steel bar framework, and pouring concrete of the cover beam;
and after the bent cap reaches the preset strength, sequentially detaching the side die, the bottom die and the support to complete the construction of the bent cap.
2. The method for constructing a capping beam according to claim 1, wherein after the steps of laying a bottom mold of the capping beam on the erected support and binding a steel reinforcement framework of a cast-in-place box beam to form a steel reinforcement framework, the method further comprises:
penetrating a prestressed pipe into the steel bar framework, wherein a prestressed steel strand is arranged in the prestressed pipe;
after the bent cap reaches preset intensity, demolish in proper order the side form the die block and the support, in order to accomplish the step of bent cap's construction includes:
after the bent cap reaches a preset strength, sequentially dismantling the side die, the bottom die and the bracket;
after the side die, the bottom die and the support are disassembled, performing tension test on the prestressed steel strand;
and if the tension test meets the construction requirements, finishing the construction of the cover beam.
3. The method of constructing a capping beam of claim 2, wherein the prestressed steel strands are high strength low relaxation steel strands.
4. The method for constructing a capping beam as claimed in claim 2, wherein the step of completing the construction of the capping beam if the tension test meets the construction requirement further comprises:
if the tension test meets the construction requirements, erecting a prefabricated box girder below the cover beam, and performing a second tension test on the prestressed steel strand;
and if the second tensioning test meets the construction requirements, finishing the construction of the cover beam.
5. The method for constructing a capping beam as claimed in claim 4, wherein if the second tension test meets the construction requirements, the step of completing the construction of the capping beam further comprises:
and if the second tensioning test meets the construction requirements, grouting and sealing the hole channel on the bent cap to finish the construction of the bent cap.
6. The method of constructing a capping beam according to claim 1, wherein after the steps of laying the side forms on the reinforcing frames and pouring the concrete of the capping beam, the method of constructing a capping beam further comprises:
curing and equi-strengthening the bent cap;
and if the concrete of the cover beam reaches a first preset strength, the side die is disassembled.
7. The method for constructing a capping beam as claimed in claim 6, wherein the step of removing the side form, if the capping beam reaches a first predetermined strength, further comprises:
after the side mold is disassembled, the bent cap is maintained and has equal strength;
and if the cover beam reaches second preset strength, removing the bottom die and the support.
8. The method for constructing a capping beam as claimed in claim 1, wherein the step of determining a construction position of the capping beam and setting up a bracket according to the construction position comprises:
and determining the construction position of the cover beam, and sequentially installing a bearing platform top embedded part, a steel pipe column, a first distribution beam, a Bailey beam and a second distribution beam at the construction position so as to complete the erection of the bracket.
9. The method of constructing a capping beam of claim 8, wherein the first distribution beam is a double split 40b i-beam and the second distribution beam is a 40b i-beam or a 25b i-beam.
10. The method of constructing a capping beam as claimed in claim 1, wherein the step of laying the side form on the reinforcing frame further comprises, after the step of laying the side form:
and sealing the joint between the bottom die and the side die by using a sponge strip.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113089491A (en) * | 2021-04-09 | 2021-07-09 | 中铁九局集团第七工程有限公司 | Construction method of large cantilever prestressed concrete bent cap |
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