CN113089491A - Construction method of large cantilever prestressed concrete bent cap - Google Patents
Construction method of large cantilever prestressed concrete bent cap Download PDFInfo
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- CN113089491A CN113089491A CN202110383986.5A CN202110383986A CN113089491A CN 113089491 A CN113089491 A CN 113089491A CN 202110383986 A CN202110383986 A CN 202110383986A CN 113089491 A CN113089491 A CN 113089491A
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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
- E01D19/02—Piers; Abutments ; Protecting same against drifting ice
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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 provides a construction method of a large cantilever prestressed concrete bent cap, belonging to the field of construction of a bridge structure in a building with special purpose, comprising the following steps: step S1, constructing a support column foundation; step S2, mounting the bracket steel pipe column; step S3, manufacturing and installing a beam falling sand box; step S4, mounting a cross beam; s5, assembling and mounting the Bailey beam; step S6, mounting a bottom die; step S7, pre-pressing the bracket; step S8, installing steel bars, constructing embedded parts and reserved holes; step S9, mounting a side die; step S10, pouring concrete on the cover beam; step S11, dismantling the side mould and curing the concrete; step S12, performing prestressed construction on the cover beam; and step S13, removing the support and the bottom die. The capping beam construction method is simple and rapid, can greatly improve the construction efficiency, quickens the construction progress, is beneficial to the control of the construction quality and the construction safety, reduces the construction cost and has strong applicability.
Description
Technical Field
The invention belongs to the technical field of construction of bridge structures in buildings with special purposes, and particularly relates to a construction method of a large cantilever prestressed concrete bent cap.
Background
With the rapid development of urban traffic, viaducts have been adopted by more and more cities. And the surrounding environment has great influence on the model selection of the bridge substructure, and in order to ensure enough driving width under the bridge and transparent visual field, the large cantilever and few pier studs become the preferred scheme of municipal bridge design.
The construction speed of the traditional construction method for the large cantilever bent cap is slow, the construction cost is high, the safety risk is high, and the traditional construction method for the concrete bent cap has the following defects and shortcomings: the bent cap has long cantilever, the underground is influenced by traffic or river channels, the full floor type support cast-in-place construction cannot be adopted, the deflection deformation of the end of the cantilever end support in the traditional construction method is overlarge, more turnover materials are consumed, the workload is large, large-scale mechanical hoisting equipment is required to be matched, and the construction difficulty and the construction period are increased.
Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide a construction method of a large cantilever prestressed concrete bent cap, which at least solves the problems of low construction speed, low cost and high safety risk at present.
In order to achieve the above purpose, the invention provides the following technical scheme:
a construction method of a large cantilever prestressed concrete bent cap comprises the following steps:
step S1, constructing a support column foundation, constructing a concrete column foundation between a bearing platform and the ground, wherein the concrete column foundation is positioned on one side of a pier body facing a cantilever end, constructing concrete cushion plate foundations on two side road slopes below a bent cap, and embedding reinforcing steel bars in the concrete column foundation and the concrete cushion plate foundations;
step S2, mounting a support steel pipe column, wherein the steel pipe column comprises a first steel pipe column and a second steel pipe column, the first steel pipe column is connected above a concrete column foundation, the second steel pipe column is connected above a concrete pad plate foundation, and bolts are pre-buried above the concrete column foundation and the concrete pad plate foundation and used for being connected with the steel pipe column;
step S3, manufacturing and installing a beam falling sand box, wherein the beam falling sand box is fixed above the first steel pipe column and the second steel pipe column after being manufactured, and is used for finely adjusting the elevation of the bracket system and facilitating the disassembly of the bracket system;
step S4, mounting a cross beam, wherein the cross beam is arranged along the road passing direction, is mounted above the beam falling sand box and is positioned between the beam falling sand box and the Bailey beam and used for providing a placing platform for the Bailey beam and conducting the force above the Bailey beam downwards;
step S5, assembling and installing the Bailey beams, assembling a plurality of Bailey pieces into Bailey beam sections, connecting any two Bailey beam sections by adopting a cross frame to form an integrally assembled Bailey beam, installing a plurality of square pipe brackets at the longitudinal two sides of the integrally assembled Bailey beam, forming an operation platform by the square pipe brackets and the integrally assembled Bailey beam, integrally hoisting the Bailey beam and the square pipe brackets assembled on the ground above a cross beam, and adjusting the elevation by utilizing a beam falling sand box;
step S6, mounting a bottom die, namely combining a plurality of sections of bottom dies into a capping beam bottom die, wherein the bottom die is a shaping steel template, and mounting and fixing the capping beam bottom die on the integrally assembled Bailey beam;
step S7, pre-pressing the bracket, pre-pressing the bottom die by stacking, adopting a step-by-step loading mode, monitoring the settlement of the bracket after each step of loading is finished, and unloading step by step after the deformation of the bracket is stable;
step S8, installing steel bars, constructing an embedded part and a reserved hole, installing a bent cap steel bar on a bottom die, and determining the positions of the embedded part and the reserved hole;
step S9, mounting side molds, namely mounting the side molds at the cantilever ends of the cover beams by taking the bottom mold as a positioning template, wherein the side molds are symmetrically arranged left and right, and the staggering and tightness of seams are controlled in the mounting process;
step S10, pouring the cover beam with concrete, wherein the pouring process is continuously carried out, the bottom plate and the web plate are layered and sectionally poured from a lower position to a higher position when being poured, and the positions of the template, the steel bar, the settlement observation point and the embedded part and the size of the protective layer are checked in the pouring process to ensure that the positions are not deformed;
step S11, dismantling the side die and curing the concrete, after the concrete is poured and initially set, carrying out watering curing on the capping beam covering cotton felt cloth, and dismantling the side die after the strength of the capping beam concrete meets the requirement;
step S12, performing prestressed construction on the bent cap, performing tensioning operation after the bent cap beam body reaches the specified strength and elastic modulus, performing double control on the tension force and the elongation value of the steel strand bundle, plugging the end of the anchorage device after the tension force reaches the design requirement, and performing mud jacking construction;
and step S13, removing the support and the bottom die, and removing the bottom die and the support when the strength of the concrete reaches the design strength and the temperature difference between the concrete core and the outer surface and the temperature difference between the outer surface of the concrete and the environment are less than 15 ℃.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, the foundation of the concrete pad plate is embedded with the foundation bolt, and the foundation of the concrete pad plate is detachably connected with the ground through the foundation bolt;
the concrete cushion plate is a C30 concrete member with the structural size of 1.8m multiplied by 0.5m and the interior is provided with
HRB400 steel bars.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, two pier bodies of the bent cap are provided, two rows of the steel pipe columns are arranged along the road passing direction, and each row comprises a first steel pipe column positioned below the center of the bent cap and second steel pipe columns positioned below two sides of the cantilever end of the bent cap.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, a horizontal steel pipe support and an inclined steel pipe support are arranged between two adjacent first steel pipe columns along the road passing direction; and a horizontal steel pipe support and an inclined steel pipe support are also arranged between every two adjacent second steel pipe columns along the road passing direction.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, between the step S5 and the step S6, that is, after the bailey beam is installed, the installation of the collapse prevention beam is further included, and the collapse prevention beam is arranged between the integrally assembled bailey beam and the bent cap;
the anti-crushing beam is respectively arranged at the lower part of the center of the bent cap and the part of the cantilever end of the bent cap, which is close to the pier cap.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, the cross beam is a double-spliced I-shaped steel structure, and the length direction of the I-shaped steel is consistent with the road passing direction; the length of a single I-steel is 6 m.
In the construction method of the large cantilever prestressed concrete capping beam, preferably, the support pre-pressing in the step S7 is carried out in three stages, wherein the pre-pressing is respectively 60%, 100% and 110% of the standard weight of the capping beam, the settlement of the support is monitored at an interval of 12h after the loading of each stage is finished, and the next stage of loading is carried out when the average value of the settlement of the monitoring point at the top of the support at the interval of 12h is less than 2 mm;
the unloading process is carried out step by step according to 110%, 100% and 60%, deformation of the support is checked after unloading, the elevation of the bottom die is adjusted under the condition that the support is deformed in elastic deformation and no part is damaged, and the next procedure construction is carried out after the support is reinforced.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, when the bent cap is cast with concrete in the step S10, the cast-in temperature of the concrete is between 5 and 30 ℃, and the concrete is cast in layers in the casting process, so that the casting interval time of each two layers of concrete is not more than 2 hours.
In the construction method of the large cantilever prestressed concrete cap beam, preferably, a barrier is arranged on a traffic lane between the first steel pipe column and the second steel pipe column.
In the construction method of the large cantilever prestressed concrete bent cap, preferably, the length of the large cantilever prestressed concrete bent cap is 28-30 m;
the outer diameters of the first steel pipe column and the second steel pipe column are
The wall thickness is 10 mm.
Has the advantages that:
the construction method of the large cantilever prestressed concrete bent cap adopts the support system in the form of the combination of the steel pipe column and the integral assembled Bailey beam to construct the municipal bridge large cantilever prestressed concrete bent cap, the construction is simple and rapid, the construction efficiency can be greatly improved, and the construction progress is accelerated; the Bailey pieces can be freely spliced according to requirements, cutting is not needed, applicability is strong, a support system formed by the spliced Bailey beams is light in weight and high in rigidity, cost is saved, safety and reliability are realized, mounting and dismounting are relatively simple and rapid, construction efficiency of the bent cap support can be improved, and passing safety of vehicles on the road surface below the bent cap can be guaranteed.
Through the movable concrete cushion base with the embedded foundation bolts, the movable concrete cushion base is convenient to mount and dismount, and can be used in a turnover mode at any time according to construction needs, so that construction materials are greatly saved, and energy conservation and consumption reduction are achieved.
The construction method is simple and rapid, improves the construction efficiency, is beneficial to the control of construction quality and construction safety, reduces the construction cost, has strong applicability and has wide popularization prospect.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. Wherein:
FIG. 1 is a process flow diagram of a construction method according to an embodiment of the present invention;
FIG. 2 is a front view of a bent cap construction bracket system according to an embodiment of the present invention;
FIG. 3 is a top view of FIG. 2;
FIG. 4 is a side view of FIG. 2;
FIG. 5 is a graph of weight distribution and monitoring point positions (circled representative monitoring points) in the step of pre-pressing the stent;
fig. 6 is a schematic view of a capping beam prestressed duct grouting structure according to an embodiment of the present invention.
In the figure: 1. a bearing platform; 2. a pier body; 3. a capping beam; 4. the integrated assembled Bailey beam; 5. a concrete column foundation; 6. a concrete pad foundation; 7. a first steel pipe column; 8. a second steel pipe column; 9. fencing; 10. dropping the beam sand box; 11. a cross beam; 12. the beam is prevented from being crushed; 13. a gangboard; 14. a thermal line; 15. supporting by a horizontal steel pipe; 16. supporting the inclined steel pipe; 17. a square tube bracket; 18. a pre-stressed duct; 19. and (4) exhausting holes.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected" and "connected" used herein should be interpreted broadly, and may include, for example, a fixed connection or a detachable connection; they may be directly connected or indirectly connected through intermediate members, and specific meanings of the above terms will be understood by those skilled in the art as appropriate.
As shown in fig. 1 to 6, according to an embodiment of the present invention, a construction method of a large cantilever prestressed concrete cap beam is provided, and the present invention adopts a construction principle of first breaking whole into parts and then breaking whole into parts. Firstly, designing a support structure and an operation platform according to the size of a bent cap determined by a design drawing; the method comprises the steps of firstly decomposing into groups, assembling the Bailey pieces into Bailey beam segments and installing an operation platform so as to reduce the construction time of bracket assembly, reduce the interference of a travelling crane and accelerate the construction progress. And then integrally hoisting in sequence to form a support structure and an operation platform, and finally performing prestressed concrete cover beam construction.
The construction method specifically comprises the following steps:
step S1, constructing a support column foundation, constructing a concrete column foundation 5 between the bearing platform 1 and the ground, wherein the concrete column foundation 5 is positioned on one side of the pier body 2 facing the cantilever end, constructing concrete cushion plate foundations 6 on the highway slopes on two sides below the bent cap 3, and embedding reinforcing steel bars in the concrete column foundation 5 and the concrete cushion plate foundations 6.
In the specific embodiment of the invention, foundation bolts are embedded in the concrete cushion plate foundation 6, and the concrete cushion plate foundation 6 is detachably connected with the ground through the foundation bolts; the concrete cushion plate is a C30 concrete member with the structural size of 1.8m multiplied by 0.5m and the interior is provided with
And (5) reinforcing steel bars. And a flange plate is arranged above the concrete cushion plate foundation 6 and is used for being connected with the steel pipe column above.
The concrete column foundation 5 is a C30 concrete column with the diameter of 1m and is internally provided with
The HRB400 steel bars are arranged on the steel bar,
the reinforcing steel bars are transversely arranged, and the reinforcing steel bars are arranged,
the reinforcing steel bars are vertically arranged. And a flange plate is arranged above the concrete column and is used for being connected with the steel pipe column above the concrete column.
Step S2, installing a support steel pipe column, wherein the steel pipe column comprises a first steel pipe column 7 and a second steel pipe column 8, the first steel pipe column 7 is connected above the concrete column foundation 5, the second steel pipe column 8 is connected above the concrete pad plate foundation 6, and bolts are pre-buried above the concrete column foundation 5 and the concrete pad plate foundation 6 and used for being connected with the steel pipe columns.
In the embodiment of the invention, the length of the large cantilever prestressed concrete capping beam 3 is 28-30m (such as 28.2m, 28.4m, 28.6m, 28.8m, 29m, 29.2m, 29.4m, 29.6m and 29.8 m); pier shaft 2 of bent cap 3 is provided with two, and the steel-pipe column is provided with two rows along the road direction of passing, all includes the first steel-pipe column 7 that is located bent cap 3 center below and is located the second steel-pipe column 8 of 3 cantilever end both sides of bent cap below in every row. The first steel pipe column 7 and the second steel pipe column 8 have outer diameters of
The wall thickness is 10 mm.
8 double column pier steel-pipe columns design altogether, and four steel-pipe columns that are close to the pier stud directly sit on cushion cap 1 connects the concrete column on, 4 steel-pipe columns in the outside directly sit on the concrete backing plate, set up the reinforcing bar in the backing plate, are used for the steel-pipe column to be connected with the concrete backing plate with the pre-buried M24 bolt of steel-pipe column junction.
A horizontal steel pipe support 15 and an inclined steel pipe support 16 are arranged between two adjacent first steel pipe columns 7 along the road passing direction; and a horizontal steel pipe support 15 and an inclined steel pipe support 16 are also arranged between every two adjacent second steel pipe columns 8 along the road passing direction. The horizontal steel pipe supports 15 and the diagonal steel pipe supports 16 are used for ensuring the mutual support stability of the two adjacent first steel pipe columns 7 and the two adjacent second steel pipe columns 8. And (4) checking and accepting the installation quality of the steel pipe column after connection according to construction drawings, and mainly checking whether the connection quality and the connection among the rod pieces are close, whether the stress is uniform, whether the verticality meets the design requirements and the like. And after the experience is qualified, the next procedure can be carried out.
And a barrier 9 is arranged on the traffic lane between the first steel pipe column 7 and the second steel pipe column 8. The enclosure 9 is used for isolating a construction site from a traffic road; a thermal pipeline 14 is buried in the underground part between the bearing platform 1 and the ground, and the thermal pipeline 14 is arranged between the two pier bodies 2.
And step S3, manufacturing and installing the beam dropping sand box 10, wherein the beam dropping sand box 10 is fixed above the first steel pipe column 7 and the second steel pipe column 8 respectively after being manufactured, and the beam dropping sand box 10 is used for finely adjusting the elevation of the bracket system and facilitating the disassembly of the bracket system.
In the specific embodiment of the invention, the girder dropping sand box 10 is divided into a sub box and a mother box, the sub box is reversely buckled in the mother box, the sub box body adopts a steel pipe column with the outer diameter of 48cm multiplied by 25cm multiplied by 1cm, and the upper part of the sub box body is welded with the steel pipe column
The sub-box bodies are filled with concrete and then used
The sub-box is sealed by the round steel plate, and the sub-box is manufactured; the box body of the master box adopts a steel pipe column with the outer diameter of 52cm multiplied by 25cm multiplied by 1cm, and the bottom of the master box is welded
The round steel plate is filled with dry sand in the box body and compacted, then the sub-box is buckled in the mother box in a reverse mode, the distance between the top plate of the sub-box and the bottom plate of the mother box is 40 cm-42 cm, the top plate of the sub-box and the upper longitudinal bridge are electrically welded to the I-shaped steel cross beam 11, the bottom plate of the mother box and the steel pipe column at the lower part are electrically welded, and the sand box is installed completely.
And step S4, mounting the cross beam 11, arranging the cross beam 11 along the road passing direction, mounting the cross beam 11 above the drop beam sand box 10 and between the drop beam sand box 10 and the Bailey beam, and providing a placing platform for the Bailey beam and conducting the force above the Bailey beam downwards.
In the specific embodiment of the invention, the beam 11 is of a double-spliced I-shaped steel structure, and the length direction of the I-shaped steel is consistent with the road passing direction; the length of a single I-steel is 6 m. The double-spliced 56# I-steel serves as a longitudinal beam and provides a placing platform for the Bailey beam, force above the Bailey beam is conducted downwards, the double-spliced I-steel is formed by connecting 4cm multiplied by 1cm steel plates into a whole, and the two ends of the combined I-steel are provided with hanging rings to facilitate hoisting. Before the I-steel is hoisted, the I-steel placement position is lofted, so that the influence of the I-steel placement deviation on force transmission is prevented; after the I-steel is installed, the measuring team lofts the Bailey beam to erect a side line, and the Bailey beam erection position is guaranteed.
Step S5, assembling and installing the Bailey beams, assembling a plurality of Bailey pieces into Bailey beam sections, connecting any two Bailey beam sections by adopting a cross frame to form an integrally assembled Bailey beam 4, installing a plurality of square pipe brackets 17 at the longitudinal two sides of the integrally assembled Bailey beam 4, enabling the distance between any two square pipe brackets 17 to be equal, forming an operation platform by the square pipe brackets 17 and the integrally assembled Bailey beam 4, integrally hoisting the Bailey beams and the square pipe brackets 17 assembled on the ground to the upper side of the cross beam 11, and adjusting the elevation by utilizing the girder dropping sand box 10.
In a specific embodiment of the invention, each group of bailey beam segments consists of 2 bailey pieces, and the longitudinal length of the integral assembled bailey beam 4 is arranged according to the span of the capping beam 3. The square pipe support 17 is fixed on the Bailey beam in a triangular shape, and the springboard 13 is arranged above the square pipe support 17 on two sides of the integral assembled Bailey beam 4 and used as an auxiliary construction platform.
The construction method of the large cantilever prestressed concrete bent cap 3 further comprises the step of installing an anti-crushing beam 12, wherein the anti-crushing beam 12 is arranged between the integral assembled Bailey beam 4 and the bent cap 3; the construction and installation of the anti-crushing beam 12 are carried out after the installation of the Bailey beam, and the anti-crushing beam 12 is respectively arranged at the lower part of the center of the bent cap 3 and the place where the cantilever end of the bent cap 3 is close to the pier cap.
In the specific embodiment of the invention, the anti-crushing beam positioned at the lower part of the center of the cover beam 3 consists of 3I-beams, the distance between the I-beams is 20cm, the part, close to a pier cap, of the cantilever end of the cover beam 3 consists of 2I-beams, the distance between the I-beams is 20cm, and the lower parts of the cantilever ends at the left side and the right side are provided with 4I-beams in total. The anti-crushing beam 12 is used for providing support for the construction of the cover beam 3.
And step S6, mounting a bottom die, namely combining a plurality of sections of bottom dies into a bent cap 3 bottom die which is a shaping steel template, and mounting and fixing the bent cap 3 bottom die on the integrally assembled Bailey beam 4.
In the specific embodiment of the invention, in order to conveniently detach the bottom die of the bent cap 3, the bottom die of the cantilever end of the bent cap 3 on each side is divided into four sections, before the die is erected, the bent cap 3 is firstly lofted, and then the bottom die is installed. The bottom die is used as a positioning template, the plane position and the horizontal precision of the top of the bottom die are repeatedly checked, and the bottom die is fixed with the platform iron piece after being qualified. During installation of the bottom die, great collision is avoided so as to prevent great deformation. In the installation process, the dislocation and the tightness of the joint of the bottom die are strictly controlled, the dislocation is controlled within a specification allowed range, and the tightness of the joint of the bottom die is ensured by sticking double-sided adhesive tapes. The template of the bent cap 3 at each side is divided into 4 small blocks, the longest segment is 2.4m, the maximum weight is 1.4t, a 30t crane is selected for hoisting, and the bent cap 3 bottom die is stably placed on the Bailey beam frame.
And step S7, pre-pressing the support, pre-pressing the bottom die in a stacking manner, monitoring the settlement of the support after each stage of loading is finished, and unloading the support stage by stage after the support is stable in deformation.
In the specific embodiment of the invention, the support pre-pressing is carried out in three stages, namely 60%, 100% and 110% of the standard weight of the bent cap 3, the settlement of the support is monitored at intervals of 12h after the loading of each stage is finished, and the next stage of loading is carried out when the average value of the settlement of the monitoring point 12h at the top of the support is less than 2 mm; specific monitor points are shown in fig. 5 (in the figure, 1#, 3#, 5#, 7#, 8#, 10#, 12#, and 14# are monitor points, respectively). And observing the support in the loading process, wherein the observation range comprises deformation observation and structural installation strength and stability observation. The pre-pressed load with the weight of 1.1 times is maintained for more than 24 hours to reach a stable state, if the pre-pressed state of the bracket meets the condition that the average settlement amount of 24 hours is less than 1mm or the average accumulated settlement amount of 72 hours is less than 5mm, the bracket can be unloaded, otherwise, the observation is continued until the deformation of the bracket is basically stable.
The unloading process is carried out step by step according to 110%, 100% and 60%, deformation of the support is checked after unloading, the elevation of the bottom die is adjusted under the condition that the deformation is in elastic deformation and no part is damaged, and the next procedure construction is carried out after the support is reinforced.
And S8, installing steel bars, constructing the embedded part and the reserved hole, installing the steel bars of the bent cap 3 on the bottom die, and determining the positions of the embedded part and the reserved hole.
In the concrete embodiment of the invention, the steel bars are uniformly manufactured in the steel bar processing field, the steel bars are cleaned before processing, and the steel bars are cleaned when encountering oil stains, paint coats, rust and the like. In order to reduce the workload of installing the steel bars on the support, the whole steel bars can be firstly bound into a plane or vertical face framework before installation, when the span of the beam is large, the binding can be carried out in a segmented mode, and when the binding cannot be carried out in a whole or segmented mode, the binding can be carried out in a scattered mode.
The positions of all embedded parts need to be checked again through measurement before concrete pouring, and pouring construction can be carried out on the embedded parts when requirements are met; and carrying out corresponding anticorrosion treatment on the exposed part. The number and the aperture of each reserved hole are reduced as much as possible, no sharp water caltrop is available, and reinforcing steel bar meshes are added around the holes.
And step S9, mounting side dies, namely mounting the cantilever end side dies of the cover beam 3 by taking the bottom die as a positioning template, wherein the side dies are symmetrically arranged left and right, and controlling the joint dislocation and the sealing property in the mounting process.
In the concrete embodiment of the invention, in order to ensure the beautiful appearance of the concrete surface, a large block of shaped steel mould side moulds are used for construction, and in order to facilitate the disassembly of the side mould moulds, the side moulds at the cantilever end of the cover beam 3 are divided into nine sections and are symmetrically arranged in the left and right directions. And after the side die template is installed, drawing wind cables at four corner points of the top cap.
And S10, pouring concrete of the bent cap 3, carrying out concrete pouring on the bent cap 3, wherein the pouring process is continuously carried out, layering and subsection pouring are carried out from a lower position to a higher position when the bottom plate and the web plate are poured, and the positions of the template, the steel bar, the settlement observation point and the embedded part and the size of the protective layer are checked in the pouring process to ensure that the positions are not deformed.
In the concrete embodiment of the invention, when the concrete of the bent cap 3 is poured, the temperature of the concrete in the mould is between 5 and 30 ℃, and the concrete is poured in layers in the pouring process, so that the pouring interval time of every two layers of concrete is not more than 2 h.
Concrete is poured and intensively mixed by a concrete mixing station, a concrete transport vehicle is transported to a construction site, the concrete pump vehicle is transported to a beam top for concrete pouring, when the free pouring height of concrete exceeds 2m, the concrete is poured by a chute or a string cylinder, and the distance between the outlet of the string cylinder and the surface of the concrete is about 1.5m, so that the concrete is prevented from being separated.
And step S11, dismantling the side mold and curing the concrete, after the concrete is poured and initially set, carrying out watering curing on the covering cotton felt cloth of the bent cap 3, and dismantling the side mold after the concrete strength of the bent cap 3 meets the requirement.
In the specific embodiment of the invention, because the weight of the side formwork is larger, the side formwork is strictly prohibited from being pulled and dragged and constructed brutally during the formwork dismantling operation, and the accidents that the side formwork damages the concrete surface or blocks are damaged and fallen off due to hard damage are avoided. The side mould and the capping beam 3 side mould which does not bear the vertical load generally can be dismounted when the strength of the concrete reaches more than 2.5Mpa (the value can be determined by the compressive strength of the test piece through the synchronous maintenance). And after the form is removed, if the concrete curing time is not enough, continuing curing.
And step S12, performing prestress construction on the bent cap 3, performing tensioning operation after the beam body of the bent cap 3 reaches the specified strength and elastic modulus, tensioning the steel strand bundle by adopting a tension and elongation value dual control method, plugging the end of the anchorage device after the tension reaches the design requirement, and performing mud jacking construction.
In the specific embodiment of the invention, before the tensioning operation, tensioning preparation is carried out: inspecting the anchorage device, the clamping piece and the like; the jack, an oil pump, an oil meter and the like are calibrated in a matching way; checking and confirming the operation space of the jack; carrying out comprehensive inspection on the beam body; and cutting off redundant steel strand wires. The working anchor, the limiting plate, the jack, the tool anchor and the clamping piece are installed as required, and the working anchor is positioned in the groove of the anchor backing plate and closely attached to each other; the four-concentricity meets the requirement, namely the prestressed pipeline, the anchor backing plate, the anchor and the jack are basically concentric; the oil pipe joints are fastened fully, and the mounting positions of the jack and the oil meter are matched correctly.
All longitudinal prestressed bundles are tensioned by self-anchored anchors, and the tensioning sequence is strictly carried out according to the requirements of design drawings. And (5) performing tensioning operation after the beam body of the bent cap 3 reaches the specified strength and the corresponding elastic modulus. The prestress tensioning is carried out in two batches, the prestressed tendons of the tensioning part of the first batch bear the dead weight of the beam body and the construction load, and the residual prestressed tendons are tensioned after the second batch is loaded on the bridge under constant load to bear the design load. The steel strand bundle is tensioned by adopting a tension force and elongation value double control method, namely after the tension force reaches the design requirement, if the error between the actual elongation value and the theoretical value is between-6% and + 6%, the tensioning of the steel strand bundle is qualified. Otherwise, if the tension force reaches the design requirement, but the error between the actual elongation value and the theoretical value exceeds the standard, the construction is suspended, and the tension is continued after the reason is analyzed and processed. If all normal, the end of the anchorage device is blocked, grouting is carried out as soon as possible, and end sealing is carried out.
And (3) grouting the prestressed duct after tensioning is finished, wherein the grouting of the prestressed duct comprises the following three steps:
1. and after tensioning is finished, cutting the redundant steel strands by using a cutting machine, wherein the length of the cut steel strands is not less than 3 cm. And after the cutting is finished, the cement is adopted to seal the pores between the tensioning anchorage device and the tensioning cable, and the sealing head is checked to ensure that slurry does not leak in the slurry pressing process.
2. The grouting agent is prepared, slurry stirring is carried out according to the mixing proportion strictly, the stirred slurry meets the design requirement, and the slurry has the performance of no bleeding and no shrinkage and can be poured for a time meeting the requirement of a construction process. According to the embodiment of the invention, SY-CG type pipeline grouting material is adopted, the water-material ratio is 0.28:1, 80-90% of water is firstly added during slurry mixing, a stirrer is started (the stirring speed is not lower than 1000r/min), all grouting materials are uniformly added while stirring, stirring is carried out again after all the grouting materials are added, then the rest 10-20% of stirring water is added, and stirring is continued for not less than 2min until uniform consistency is achieved. After the slurry is uniformly stirred, a machine-out fluidity test is carried out on site, after the fluidity meets the requirement, the slurry can enter the storage tank through the filter screen, and the slurry is continuously stirred in the storage tank so as to ensure the fluidity of the slurry. And (4) grouting construction of the prestressed duct 18 is carried out by adopting a grouting pump.
3. The prestressed duct grouting construction is generally completed within 48 hours after the tensioning and anchoring.
Before grouting, high-strength cement slurry and the like are adopted to block gaps between anchor clamps and other possible grout leakage positions, the thickness of a blocking covering layer is not less than 15mm, and grouting can be performed after the blocking material reaches a certain strength.
The time from stirring to pressing into the pore channel is not more than 40 min. For slurries that have a reduced fluidity due to delayed use, the fluidity must not be increased by the addition of water.
Grouting is carried out from one end to the other end in the grouting sequence, the lower layer of prestressed duct 18 is firstly injected, and 4 rows of prestressed ducts 18 are arranged from top to bottom.
The grouting is not interrupted, and the exhaust holes 19 at the highest point are sequentially opened and closed one by one, so that the air exhaust of the pore passage is smooth. During grouting of a certain prestressed duct 18, the exhaust hole 19 connected to the duct is opened, and after grouting, the exhaust hole 19 is closed.
The longitudinal grouting pressure of the beam body is preferably 0.5-0.7 MPa, and when the pore channel is long or primary grouting is adopted, the maximum pressure is preferably 1.0 MPa. Pressing slurry at one end, discharging slurry at the other end, sealing and maintaining pressure when the concentration of a slurry outlet of the pore channel is the same as that of slurry inlet, closing the slurry outlet, and maintaining a pressure stabilizing period (pressure maintaining for 5 minutes) of 0.5-0.6MPa and not less than 3 min.
And (4) checking the compaction condition of the grouting from the grouting inlet and the grouting outlet after grouting, and if the grouting is not compact, timely supplementing the grouting to ensure that the pore channel is completely compact. When pressure slurry filling is carried out, the water-slurry suspension in the prestressed duct 18 is allowed to freely flow out from the outlet. And pumping by using a grouting pump again until homogeneous slurry flows out at the outlet end, keeping for 5min under the pressure of 0.5MPa, and repeating the process for 1-2 times.
After the grouting work is finished, equipment is cleaned immediately or other prestressed ducts 18 are shifted to carry out grouting, valve equipment on the prestressed ducts 18 can be dismantled after the cement paste is finally set, the valve equipment is cleaned immediately after the valve equipment is dismantled, and the valve equipment is allowed to be reused after necessary inspection.
And step S13, removing the support and the bottom die, and removing the bottom die and the support when the strength of the concrete reaches the design strength and the temperature difference between the concrete core and the outer surface and the temperature difference between the outer surface of the concrete and the environment are less than 15 ℃.
In the specific embodiment of the invention, for a non-bearing template, the template can be disassembled when the temperature difference between the concrete core and the outer surface and between the concrete outer surface and the environment is less than 15 ℃ and the concrete reaches 2.5 MPa; for the bearing template, the template can be detached when the concrete strength reaches the design strength and the temperature difference between the concrete core and the outer surface and between the concrete outer surface and the environment is less than 15 ℃.
The bottom die template is dismantled to meet the following requirements: (1) the removal of the bottom die template follows the sequence of first supporting and then removing, and then removing the template first; (2) the template is strictly forbidden to be thrown when the template is removed; (3) when the bottom die is dismantled, the bottom die is dismantled from the position with the largest deflection deformation, and finally the position with small deformation is dismantled; (4) the bottom die template is not allowed to be dismantled by methods of violent beating, strong twisting and the like; (5) and after the bottom die template is removed, the bottom die template is maintained and sorted in time and is properly stored in a classified mode.
In conclusion, the construction method of the large cantilever prestressed concrete bent cap of the invention adopts the steel pipe column and the integral assembled Bailey beam combined bracket system to carry out the construction of the municipal bridge large cantilever prestressed concrete bent cap, the construction is simple and rapid, the construction efficiency can be greatly improved, and the construction progress is accelerated; the Bailey pieces can be freely spliced according to requirements, cutting is not needed, applicability is strong, a support system formed by the spliced Bailey beams is lighter in weight, high in rigidity and high in cost saving, safety and reliability are achieved, mounting and dismounting are relatively simple and rapid, construction efficiency of the bent cap support can be improved, and passing safety of vehicles on the road surface below the bent cap can be guaranteed.
Through the movable concrete cushion base with the embedded foundation bolts, the movable concrete cushion base is convenient to mount and dismount, and can be used in a turnover mode at any time according to construction needs, so that construction materials are greatly saved, and energy conservation and consumption reduction are achieved.
The construction method is simple and rapid, improves the construction efficiency, is beneficial to the control of construction quality and construction safety, reduces the construction cost, has strong applicability and has wide popularization prospect.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The construction method of the large cantilever prestressed concrete bent cap is characterized by comprising the following steps of:
step S1, constructing a support column foundation, constructing a concrete column foundation between a bearing platform and the ground, wherein the concrete column foundation is positioned on one side of a pier body facing a cantilever end, constructing concrete cushion plate foundations on two side road slopes below a bent cap, and embedding reinforcing steel bars in the concrete column foundation and the concrete cushion plate foundations;
step S2, mounting a support steel pipe column, wherein the steel pipe column comprises a first steel pipe column and a second steel pipe column, the first steel pipe column is connected above a concrete column foundation, the second steel pipe column is connected above a concrete pad plate foundation, and bolts are pre-buried above the concrete column foundation and the concrete pad plate foundation and used for being connected with the steel pipe columns;
step S3, manufacturing and installing a beam falling sand box, wherein the beam falling sand box is fixed above the first steel pipe column and the second steel pipe column after being manufactured, and is used for finely adjusting the elevation of the bracket system and facilitating the disassembly of the bracket system;
step S4, mounting a cross beam, wherein the cross beam is arranged along the road passing direction, is mounted above the girder dropping sand box and is positioned between the girder dropping sand box and the Bailey girder, and is used for providing a placing platform for the Bailey girder and downwards transmitting the force above the Bailey girder;
step S5, assembling and installing the Bailey beams, assembling a plurality of Bailey pieces into Bailey beam sections, connecting any two Bailey beam sections by adopting a cross frame to form an integrally assembled Bailey beam, installing a plurality of square pipe brackets at the two longitudinal sides of the integrally assembled Bailey beam, forming an operation platform by the square pipe brackets and the integrally assembled Bailey beam, integrally hoisting the Bailey beam and the square pipe brackets assembled on the ground above a cross beam, and adjusting the elevation by utilizing a beam falling sand box;
step S6, mounting a bottom die, namely combining a plurality of sections of bottom dies into a capping beam bottom die, wherein the bottom die is a shaping steel template, and mounting and fixing the capping beam bottom die on the integrally assembled Bailey beam;
step S7, pre-pressing the bracket, pre-pressing the bottom die by stacking, adopting a step-by-step loading mode, monitoring the settlement of the bracket after each step of loading is finished, and unloading step by step after the deformation of the bracket is stable;
step S8, installing steel bars, constructing an embedded part and a reserved hole, installing a bent cap steel bar on a bottom die, and determining the positions of the embedded part and the reserved hole;
step S9, installing side forms, namely, installing the side forms at the cantilever ends of the cover beams by taking the bottom die as a positioning template, wherein the side forms are symmetrically arranged left and right, and the staggering and the sealing performance of seams are controlled in the installation process;
step S10, pouring the cover beam with concrete, wherein the pouring process is continuously carried out, the bottom plate and the web plate are layered and sectionally poured from a lower position to a higher position when being poured, and the positions of the template, the steel bar, the settlement observation point and the embedded part and the size of the protective layer are checked in the pouring process to ensure that the positions are not deformed;
step S11, dismantling the side die and curing the concrete, after the concrete is poured and initially set, carrying out watering curing on the capping beam covering cotton felt cloth, and dismantling the side die after the strength of the capping beam concrete meets the requirement;
step S12, performing prestressed construction on the bent cap, performing tensioning operation after the bent cap beam body reaches the specified strength and elastic modulus, performing double control on the tension force and the elongation value of the steel strand bundle, plugging the end of the anchorage device after the tension force reaches the design requirement, and performing mud jacking construction;
and step S13, removing the support and the bottom die, and removing the bottom die and the support when the strength of the concrete reaches the design strength and the temperature difference between the concrete core and the outer surface and the temperature difference between the outer surface of the concrete and the environment are less than 15 ℃.
2. The construction method of the large cantilever prestressed concrete cap beam according to claim 1, wherein an anchor bolt is embedded in the concrete pad foundation, and the concrete pad foundation is detachably connected with the ground through the anchor bolt;
the concrete cushion plate is a C30 concrete member, the structural size is 1.8m multiplied by 0.5m, and the interior of the concrete cushion plate is provided with
HRB400 steel bars.
3. The construction method of the large cantilever prestressed concrete bent cap as claimed in claim 2, wherein there are two pier bodies of the bent cap, and there are two rows of the steel pipe columns along the road passing direction, each row including a first steel pipe column below the center of the bent cap and a second steel pipe column below both sides of the cantilever end of the bent cap.
4. The construction method of the large cantilever prestressed concrete cap beam according to claim 3, wherein a horizontal steel pipe support and an inclined steel pipe support are arranged between two adjacent first steel pipe columns along the road passing direction; and a horizontal steel pipe support and an inclined steel pipe support are also arranged between every two adjacent second steel pipe columns along the road passing direction.
5. The construction method of the large cantilever prestressed concrete cap beam, according to claim 1, wherein, between the step S5 and the step S6, that is, after the beret beam is installed, the construction method further comprises the installation of an anti-collapse beam, wherein the anti-collapse beam is arranged between the integrally assembled beret beam and the cap beam;
the anti-crushing beam is respectively arranged at the lower part of the center of the cover beam and the part of the cantilever end of the cover beam, which is close to the pier cap.
6. The construction method of the large cantilever prestressed concrete bent cap according to claim 1, wherein the cross beam is a double-spliced I-shaped steel structure, and the length direction of the I-shaped steel structure is consistent with the road passing direction; the length of a single I-shaped steel is 6 m.
7. The construction method of the large cantilever prestressed concrete capping beam as claimed in claim 1, wherein the pre-pressing of the bracket in step S7 is performed in three stages, which are 60%, 100% and 110% of the standard weight of the capping beam, respectively, after each stage of loading is completed, the settlement of the bracket is monitored at an interval of 12h, and when the average value of the settlement of the monitoring point at the top of the bracket at the interval of 12h is less than 2mm, the next stage of loading is performed;
the unloading process is carried out step by step according to 110%, 100% and 60%, deformation of the support is checked after unloading, the elevation of the bottom die is adjusted under the condition that the support is deformed in elastic deformation and no part is damaged, and the next procedure construction is carried out after the support is reinforced.
8. The construction method of the large cantilever prestressed concrete cap beam, according to claim 1, characterized in that, in the step S10, when the cap beam is concreted, the concrete mold-entering temperature is between 5-30 ℃, and the concrete is poured in layers during the concrete pouring process, so as to ensure that the time between the concrete pouring of each two layers is not more than 2 h.
9. The construction method of the large cantilever prestressed concrete cap beam according to claim 1, wherein a fence is arranged on a traffic lane between the first steel pipe column and the second steel pipe column.
10. The construction method of the large cantilever prestressed concrete cap beam according to claim 1, wherein the length of the large cantilever prestressed concrete cap beam is 28-30 m;
the outer diameters of the first steel pipe column and the second steel pipe column are
The wall thickness is 10 mm.
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