CN215164534U - Prestress system for prefabricated small box girder type hidden cover beam - Google Patents
Prestress system for prefabricated small box girder type hidden cover beam Download PDFInfo
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- CN215164534U CN215164534U CN202120567886.3U CN202120567886U CN215164534U CN 215164534 U CN215164534 U CN 215164534U CN 202120567886 U CN202120567886 U CN 202120567886U CN 215164534 U CN215164534 U CN 215164534U
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Abstract
The utility model discloses a prestressing force system for prefabricating small box girder type hidden bent cap, prefabricated small box girder type hidden bent cap includes prefabricated small box girder, cast-in-place hidden bent cap, has between the end of prefabricated small box girder and the cast-in-place hidden bent cap and is the prefabrication-cast-in-place interface of many abrupt formula tooth piece interlock, and the prestressing force system disposes along prefabricated small box girder web direction to including internal prestressing force system and external prestressing force system; the in-vivo prestressed system comprises a plurality of in-vivo prestressed steel bundles, and the anchoring points of the in-vivo prestressed steel bundles are arranged at the end part of the web plate of the prefabricated small box girder and distributed along the height direction of the web plate of the prefabricated small box girder; the external prestress system comprises a plurality of external prestress steel beams; an inclination angle alpha exists between each external prestress steel beam and the web plate of the prefabricated small box girder. Therefore, the invention can improve the overall height of the lifting frame, meets the requirement of insufficient local clearance of the bridge, and effectively solves the problems of bearing capacity, deformation and durability between the prefabricated small box girder and the cast-in-place hidden cover girder.
Description
Technical Field
The utility model discloses a prestressing force system for latent bent cap of prefabricated small box girder formula belongs to civil engineering design field.
Background
Under the promotion of national strategic guidance and the requirements of society and industry development, the bridge construction technology is developing towards the direction of assembly, industrialization and standardization. In the overhead construction of urban expressways, prefabricated structures gradually replace cast-in-place structures. On one hand, under the same span, the concrete consumption of the prefabricated small box girder is only 50% of that of the cast-in-place box girder; in soft soil areas, the construction cost of the scheme of the prefabricated small box girder is less than 75 percent (the lower structure engineering amount is reduced, the field foundation treatment cost is eliminated) (the general calculation index per square meter of the urban overhead of the prefabricated small box girder is about 4439 yuan/m 2, and the general calculation index per square meter of the cast-in-place box girder is about 5944 yuan/m 2), the prefabricated small box girder or the prefabricated hollow plate girder is adopted for 75 percent of the upper structure (taking Ningbo city as an example, the cast-in-place box girder structure is adopted for 2011 completed airport road upper structure, the south ring and the north ring overhead are adopted for 2015 completed airport road upper structure, the prefabricated small box girder structure or the prefabricated hollow plate girder is adopted for 75 percent of the upper structure, only the curve section, the width-changing section and the ramp connecting section, the south extension of the airport road started in 2017, the west-large bridge connection engineering started in 2018 and the west extension of the south-line of the city road are adopted for 95 percent of the prefabricated small box girder (the curve section, the width-changing section and the ramp connecting section are all prefabricated structures), only the passage clearance limited section adopts a cast-in-place box girder); on the other hand, the prefabricated box girder adopts a mode of factory manufacturing and field installation, and has remarkable advantages in construction period and quality control (factory manufacturing can be synchronous with construction of other structures on the field, the construction period is saved, and the quality is easier to control by adopting assembly line and standardized operation in a factory than field operation).
However, the prefabricated box girders have a significant disadvantage in terms of passage clearance because conventional prefabricated concrete girders (prefabricated box girders) are erected on the capping beams, the specific construction of which is shown in fig. 1. When the bridge deck elevation is fixed, the occupied clearance (the height of the prefabricated small box girder and the height of the cover girder) required by the scheme of the prefabricated concrete girder is larger than that of a cast-in-place box girder, so that when the line type of the bridge deck road is determined and the clearance of the bridge is limited, a prefabricated concrete girder type system cannot be adopted (except for the unadjusted bridge deck elevation, the line type of the whole engineering road can be influenced).
In a conventional precast concrete beam structure, 1 wet joint of 25cm width is provided between precast box girders, see fig. 2. Although the wet joint is not effectively connected with the prefabricated small box girder, the wet joint is positioned in the range of the support, most of the counter-force diffusion area is positioned in the area of the prefabricated small box girder when the counter-force of the support is diffused by 45 degrees, and therefore, the wet joint is not used for bearing load for the conventional prefabricated concrete girder structure. On the contrary, for the conventional precast concrete beam structure, the bridge span part and the beam part are formed by one-time casting, and it is shown according to a large amount of destructive test data that when the structure is designed according to the specification requirement, the shearing failure near the fulcrum is an oblique section, so that the crack development needs to be inhibited by densely distributed stirrups, see fig. 3.
Disclosure of Invention
The utility model discloses to prior art's not enough, provide a prestressing force system for latent bent cap of prefabricated little case beam type, solved bearing capacity, deformation and the durability problem between prefabricated little case beam and the cast-in-place latent bent cap effectively to obtain the latent bent cap of prefabricated little case beam type that mechanical properties satisfies the requirement, thereby carry the whole height of hoisting frame, satisfy the local headroom of bridge not enough.
In order to achieve the technical purpose, the utility model adopts the following technical proposal:
a prestressed system for prefabricating a small box girder type hidden cover beam comprises prefabricated small box girders arranged along a bridge direction and a cast-in-place hidden cover beam arranged along a transverse bridge direction, wherein a prefabricated-cast-in-place interface in multi-protrusion tooth block meshing is arranged between the end head of the prefabricated small box girder and the cast-in-place hidden cover beam;
the in-vivo prestressed system comprises a plurality of in-vivo prestressed steel bundles, wherein the anchoring points of the in-vivo prestressed steel bundles are arranged at the end part of the web plate of the prefabricated small box girder and are distributed along the height direction of the web plate of the prefabricated small box girder;
the in-vitro prestressed system comprises a plurality of in-vitro prestressed steel bundles; an inclination angle alpha exists between each external prestressed steel beam and the web plate of the prefabricated small box girder;
when the prefabricated small box girder type hidden cover beam is positioned in a continuous section, the middle area of each external prestressed steel bundle is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on one side of the cast-in-place hidden cover beam, and the other end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on the other side of the cast-in-place hidden cover beam;
when the small box girder type hidden cover girder is in the simply supported section, one end of each external prestressed steel bundle is anchored on the top plate of the small box girder, and the other end of each external prestressed steel bundle is anchored in the cast-in-place hidden cover girder.
Preferably, when the prefabricated small box girder type hidden cover girder is positioned in a continuous section, the prefabricated small box girders, namely a prefabricated small box girder a and a prefabricated small box girder b, are arranged on two sides of the cast-in-place hidden cover girder; the prefabricated-cast-in-place interface between the end of the prefabricated small box girder a and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface a, and the prefabricated-cast-in-place interface between the end of the prefabricated small box girder b and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface b;
the middle area of each external prestressed steel beam is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface a and then turns through the corresponding turning block a, and is finally anchored on the bottom plate of the prefabricated small box beam a, and the other end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface b and turns through the corresponding turning block b, and is finally anchored on the bottom plate of the prefabricated small box beam b; the steering block a is installed on the web plate of the prefabricated small box girder a, and the steering block b is installed on the web plate of the prefabricated small box girder b.
Preferably, the steering block a and the steering block b respectively comprise a web plate outer side steel plate, a web plate inner side steel plate, an anchor bolt steel bar and a tensioning base plate; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate.
Preferably, when the prefabricated small box girder type hidden cover beam is positioned in the simply supported section, one end of each external prestressed steel beam sequentially penetrates through the prefabricated-cast-in-place interface and the anchor sealing plate, and then is steered by the steering block and finally anchored on the top plate of the prefabricated small box girder;
the steering block comprises a web plate outer side steel plate, a web plate inner side steel plate, an anchor bolt steel bar and a tensioning base plate; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate.
Preferably, the number of the anchor reinforcing steel bars is 4-6.
Preferably, the prefabricated-cast-in-place interface comprises an end head of a prefabricated small box girder and a cast-in-place concrete joint meshed with the end head of the prefabricated small box girder; wherein:
the end of the small prefabricated box girder comprises a box girder bottom plate end, a box girder top plate end and two box girder web plate ends positioned between the box girder bottom plate end and the box girder top plate end; the outer side surface of the end of the box girder bottom plate and the outer side surface of the end of the box girder top plate are positioned in the same plane; a plurality of web raised teeth are arranged on the outer sides of the ends of the web plates of the two box girders; the web convex teeth are arranged on the top of the web convex teeth, the upper end of the web convex teeth starts from the outer side surface of the end of the box girder top plate, the lower end of the web convex teeth crosses the connecting limit of the end of the box girder top plate and the end of the box girder web plate and ends at the outer side surface of the end of the box girder web plate, and the rest web convex teeth are arranged on the outer side surface of the end of the box girder web plate.
Preferably, the number of web lobes matches the number of in vitro prestressed steel strands.
Preferably, the number of the web convex teeth arranged at the end of the web of the single-side box girder is 3, and the number of the external prestressed steel bundles on the single side is 3.
Preferably, 4 in-vivo prestressed steel bundles are arranged in the prefabricated small box girder; correspondingly, 4 individual internal prestressed steel strand anchoring points are arranged at the end part of the prefabricated small box girder web plate along the height direction.
According to foretell technical scheme, for prior art, the utility model has the advantages of as follows:
the utility model discloses concatenation position department between prefabricated little case roof beam and cast-in-place implicit type bent cap, be the prefabricated-cast-in-place interface of many abrupt formula cogs interlock through the setting, convert cast-in-place shear interface into the pressure-bearing interface, and through cast-in-place shear interface transmission, bearing capacity lift effect is showing, and along prefabricated little case web direction configuration prestressing force system, the positive pressure at interface has been increased, the interlock that makes the cogs formula shear force key is inseparable, the validity at interface has been ensured, make aforementioned transmission state full play effect, consequently, the utility model discloses bearing capacity, deformation and durability problem between prefabricated little case roof beam and the cast-in-place implicit type bent cap have been solved effectively.
Drawings
Fig. 1 is a schematic structural view of a conventional precast concrete beam;
FIG. 2 is a schematic force-bearing diagram of a conventional precast concrete beam structure;
fig. 3 is a schematic view of a shear structure of a conventional precast concrete beam structure;
FIG. 4 is a schematic structural view of a prefabricated small box girder type hidden cover beam (a connection structure between the prefabricated small box girder and the hidden cover beam without a prestressed steel beam);
FIG. 5 is a schematic illustration of the prefabricated mini-box girder canopy beam of FIG. 4 having a torsional effect;
FIG. 6 is a shear analysis diagram of the prefabricated mini-box girder hidden cover beam of FIG. 4;
FIG. 7 is a schematic structural view of a prefabricated mini-box girder type hidden canopy beam with an interlocking precast-cast in place interface (with shear analysis);
fig. 8 is a schematic structural diagram of a prestressing system (continuous section) for prefabricating a small box girder type hidden cover beam according to the present invention;
fig. 9 is a schematic structural diagram of a prestressing system (simply supported section) for prefabricating a small box girder type hidden cover beam according to the present invention;
fig. 10 is a schematic structural view of the prefabricated box girder end according to the present invention;
fig. 11 is a schematic view of a turning block according to the present invention;
in FIGS. 1-6: 1-prefabricating a small box girder; 2-cast-in-place hidden bent cap; 2' -capping beam; 3' -a support; 4' -wet seaming; 5' -support reaction force diffusion line; 6' -longitudinal steel bars; 7' -encrypted stirrup;
h1, net height of the original cast-in-place box girder; h2, net height of conventional precast concrete beam; h3, height of a cast-in-place box girder; h4, hidden bent cap net height;
in fig. 7 to 11: 1. prefabricating a small box girder; 1-1, a small box girder bottom plate; 1-2, a small box girder web plate; 1-3, a small box girder top plate; 1-4, web convex teeth; 2. casting a hidden bent cap in situ; 3. sealing the anchor plate; 4. prefabricating a cast-in-place interface; 5. an in-vivo prestressed tendon; 6. a turning block; 6-1, a steel plate outside the web plate; 6-2, a steel plate on the inner side of the web plate; 6-3, anchor bolt reinforcing steel bars; 6-4, tensioning the base plate; 7. an anchoring groove; 8. and (3) externally prestressing tendons.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention. Unless specifically stated otherwise, the relative arrangement of the components and steps, expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may also be oriented in other different ways (rotated 90 degrees or at other orientations).
In order to increase the overall height of the lifting frame due to insufficient local clearance, it is necessary to develop a hidden beam structure system based on prefabricated small box girder type, which can effectively break through the existing bottleneck of the prefabricated structure, and its structural diagram can be seen in fig. 4.
The concept design of the prefabricated small box girder + cast-in-place hidden type capping beam structure system is relatively easy, the function is taken as the target, and the core difficulty of the design is that the prefabricated structure (the prefabricated small box girder) is connected with the cast-in-place structure (the cast-in-place hidden type capping beam), namely the bearing capacity, the rigidity and the durability are all 3 core design elements.
Urban elevations usually adopt a bidirectional 6-lane design and are composed of 8 prefabricated small box girders. When the lanes are not full, the loads borne by different prefabricated box girders are different, and besides the conventional bending and shearing, the prefabricated box girders also generate torsional deformation, and refer to fig. 5. According to the traditional prefabricated small box girder structure, because the end part is located in the range of the support, the prefabricated small box girder forms a couple through the vertical counter force difference of 2 plate type rubber supports, and resists the torque action of uneven load, namely when a prefabricated small box girder and cast-in-situ hidden cover girder structure system is adopted, the end part of the prefabricated small box girder and the combined section of the cast-in-situ hidden cover girder are in fixed end constraint, which means that the prefabricated small box girder needs to rely on self torsional rigidity to resist the effect, namely the nature of the torsional rigidity, and has the performance of bearing and resisting the circumferential shear stress flow.
The end of the prefabricated box girder is a shear peak area. The shear force peak value of the prefabricated small box girder type hidden cover beam system can not be transmitted through a support diffusion area of the traditional prefabricated small box girder, and can not be a continuous structure like a cast-in-place box girder (see figure 6, a construction wet joint exists between new concrete and old concrete, the shear force forms stress concentration in the area, the interface can form association through longitudinal steel bars, but vertical stirrups are discretely distributed and can not effectively influence the interface), the crack development can be restrained through the area encrypted stirrups, the interface area is a concrete surface, if the shear force peak value excessively extends into the cast-in-place hidden cover beam area, the rigidity of the cast-in-place hidden cover beam can be weakened, a weak surface is formed at the prefabricated small box girder, the shear force is of nature, and the shear force peak value is vertical shear stress flow.
In addition, when the prefabricated box girder is simply supported and then constructed continuously, the tearing of the interface area is aggravated by the top surface tensile stress caused by the hogging moment effect of the prefabricated small box girder in the continuous section (the tensile stress and the shear stress act synchronously). Therefore, the core and key of the development of the prefabricated small box girder hidden cover girder system lies in the development of new and old concrete contact surfaces, and the essence of the development lies in how to ensure that the contact surfaces resist shear stress. The existing method cannot meet the requirements of the bearing capacity, deformation and durability of the structural system.
The prefabricated small box girder greatly increases the difficulty of interface treatment due to the structural characteristics of the prefabricated small box girder, namely the end part of a web plate of the prefabricated small box girder is an anchoring area of a prestressed steel beam of the prefabricated small box girder, and the web plate is a key part for transferring shearing force and bearing torque, so that the shearing structural measures of the prefabricated small girder are interrupted at the end part of the web plate, and a continuous shearing structure cannot be formed, which is the biggest difficulty in the research and development of a prefabricated small box girder type hidden cover girder system.
As shown in fig. 7 to 11, the prestressed system for the prefabricated small box girder type hidden bent cap of the present invention includes a prefabricated small box girder arranged along the bridge direction, a cast-in-place hidden bent cap arranged along the transverse bridge direction, and a prestressed system configured along the web direction of the prefabricated small box girder, wherein the prestressed system includes an internal prestressed system and an external prestressed system;
the anchoring points of the steel bundles of the in-vivo prestressed system and the in-vitro prestressed system are arranged at the web plate end of the prefabricated small box girder, and a protrusion is arranged corresponding to each steel bundle anchoring point, so that when the cast-in-place hidden cover girder is poured, a prefabricated-cast-in-place interface in multi-protrusion tooth block engagement is formed between the end of the prefabricated small box girder and the cast-in-place hidden cover girder, and the shearing resistance of the interface is improved. Specifically, the prefabricated-cast-in-place interface comprises an end head of a prefabricated small box girder and a cast-in-place concrete joint meshed with the end head of the prefabricated small box girder; wherein: the end of the small prefabricated box girder comprises a box girder bottom plate end, a box girder top plate end and two box girder web plate ends positioned between the box girder bottom plate end and the box girder top plate end as shown in fig. 10; the outer side surface of the end of the box girder bottom plate and the outer side surface of the end of the box girder top plate are positioned in the same plane; a plurality of web raised teeth are arranged on the outer sides of the ends of the web plates of the two box girders; the web convex teeth are arranged on the top of the web convex teeth, the upper end of the web convex teeth starts from the outer side surface of the end of the box girder top plate, the lower end of the web convex teeth crosses the connecting limit of the end of the box girder top plate and the end of the box girder web plate and ends at the outer side surface of the end of the box girder web plate, and the rest web convex teeth are arranged on the outer side surface of the end of the box girder web plate. And the web convex tooth at the lowest part starts at the position of 20cm from the top surface of the bottom plate, and the depth of the web convex tooth is not less than 25cm of the section plane of the end part of the bottom plate of the box girder. The number of the web convex teeth is matched with the number of the in-vitro prestressed steel bundles. In this embodiment, the number of web convex teeth arranged at the end of the web of the single-side box girder is 3, and the number of the external prestressed steel bundles on the single side is 3. 4 in-vivo prestressed steel bundles are arranged in the small prefabricated box girder; correspondingly, 4 individual internal prestressed steel strand anchoring points are arranged at the end part of the prefabricated small box girder web plate along the height direction.
As shown in fig. 7, although the prefabricated-cast-in-place interface area can not be configured with steel bars, the prefabricated small box girder type hidden cover girder system is divided into 2 independent individuals despite the existence of construction joints, and the two individuals are only communicated through the bonding force of new concrete and old concrete, when the interface state is poor, the interface bearing capacity is not optimistic; when the interface state is good, the interface bearing capacity is not worse than that of a cast-in-place structure, namely, a multi-tooth block protrusion (a multi-tooth block meshed prefabricated-cast-in-place interface) of a shear key type is adopted, the cast-in-place shear interface is converted into a bearing interface and is transmitted through the cast-in-place shear interface, and the bearing capacity lifting effect is obvious; the arrangement of the prestress system increases the positive pressure of the interface, so that the engagement of the tooth block type shear key is tight, the effectiveness of the interface is ensured, and the effect of the transmission state is fully exerted.
The biggest difficulty of the prestress system for the prefabricated small box girder type hidden cover girder is that 4 individual internal prestress steel strand anchoring points are configured at the position of the interface where the prestress steel strands are arranged, namely the end part of a prefabricated small box girder web plate is provided with 4 individual internal prestress steel strand anchoring points along the height direction, and the steel bars and the steel strands in the web plate are dense, so the external prestress steel strand anchoring points are arranged at the prefabricated-cast-in-place interface.
Specifically, as shown in fig. 7-9, the in-vivo prestressed system includes a plurality of in-vivo prestressed steel bundles, and the anchoring points of the in-vivo prestressed steel bundles are arranged at the end of the web of the prefabricated small box girder and distributed along the height direction of the web of the prefabricated small box girder; the in-vitro prestressed system comprises a plurality of in-vitro prestressed steel bundles; an inclination angle alpha exists between each external prestress steel beam and the web plate of the prefabricated small box girder. In other words, the utility model discloses along prefabricated small box girder web direction, configuration and contact surface vertically prestressing force (internal, external prestressing steel bundle) through the normal stress sigma that improves the cross-section, promote the anti shear capacity at interface.
As shown in fig. 8, when the precast mini-box girder hidden cover beam is in a continuous section, the outer bundle of the prestressed body adopts a floor anchoring mode. On one hand, the hogging moment effect of the continuous beam pivot area is considered, if the continuous beam pivot area is anchored at the top, the function of the hogging moment beam of the top plate is counteracted, the beam distribution quantity of the hogging moment beam is increased, and the hogging moment beam is unreasonable and uneconomical; the bottom is anchored, so that the effect of the negative bending moment of a fulcrum can be counteracted, and the positive stress effect can be exerted on the whole cross section of the prefabricated small box girder and the cast-in-place hidden cover girder.
3 external prestressed steel beams are arranged along the height direction, and the external prestressed steel beams are arranged near each web plate of the prefabricated small box girder, namely 6 external prestressed steel beams with single section are arranged, and the external prestressed steel beams with the single section have small diameter and large quantity, so that the positive pressure balance of the section is ensured as much as possible;
the direction of the external prestress is adjusted through the steering block, the steering block needs to be embedded in a prefabricated small box girder web plate and is usually positioned on the rear side of the end sealing plate, namely the prestress steel beam completely passes through a cast-in-place concrete area and then turns, at the moment, the anchor sealing plate of the prefabricated small box girder is consistent with a conventional product and does not need to move backwards.
The steering block consists of 2 embedded plates, 4-6 connecting steel bars and 1 steering plate. Different from the anchoring steel plate of the PBL key, the steering block is anchored by adopting a double-layer steel plate, on one hand, because the concentrated force effect of the prestressed steel beam is obvious; on the other hand, the double-layer steel plate is beneficial to positioning (namely, installation accuracy) in the small box girder prefabricating stage.
The inner side steel plate and the outer side steel plate of the web are connected through anchor bolt steel bars in a welded mode, the outer side distance of the inner side steel plate and the outer side steel plate of the web is the thickness of the web at the position of a tensioning end, meanwhile, a tensioning base plate is welded with the inner side steel plate of the web, and the strength of a welding seam meets the design requirement.
In order to ensure the anchoring strength of the tensioning end, the size of steel plates on the inner side and the outer side of the web plate is not less than 150mmx150mm, the thickness of the steel plates is not less than 20mm, the diameter of anchor bolt steel bars is not less than 20mm, and round steel is adopted.
The size of the tensioning cushion plate is determined according to the design tensioning load, the width of the lower opening is not less than 100mm, and the thickness is not less than 20 mm. Groove welding seams are preferably adopted between the tensioning backing plate and the steel plate on the inner side of the web plate, the quality of the welding seams is designed to the end and meets the standard requirements, 100% detection is carried out by adopting ultrasonic and magnetic powder, and the tensioning backing plate can be used when the design requirements are met.
The bottom of the prefabricated small box girder is provided with a tensioning notch, and the position of the tensioning notch is based on that the inclination angle of the external beam is 15 +/-1 degrees. Besides configuring stiffening spiral ribs (ensuring that the anchoring section is not damaged under local stress), rigid metal corrugated pipes with small diameters are required to be configured near the anchoring section of the tensioning slot at the same time to serve as reserved channels of steel bundles, wherein the diameter of the metal corrugated pipes is small, so that the influence of holes on the prefabricated small box girder is reduced; the metal corrugated pipe is used for bonding the prestressed duct with the precast beam after grouting.
Arranging a metal corrugated pipe (arranged in the stage of binding the cast-in-situ hidden cover beam steel bars) between the anchor sealing plates of the continuous reading section; between the anchor sealing plate and the tensioning notch, a plastic pipeline (before the anchor sealing plate is installed) needs to be pre-embedded in advance, namely, in an installation site, only a steel beam needs to penetrate through a reserved external prestressed steel beam hole, if the pipeline does not exist, the site installation of the prestressed steel beam cannot be executed, the prestressed steel beam is installed and tensioned after the hidden cover beam is cast in place, and otherwise, the prestressed stress cannot take effect on a prefabricated-cast-in-place concrete interface.
In short, for the prefabricated small box girder type hidden cover beam of the continuous section, the middle area of each external prestressed steel bundle is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on one side of the cast-in-place hidden cover beam, and the other end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on the other side of the cast-in-place hidden cover beam; specifically, two sides of a cast-in-place hidden cover beam are respectively provided with a prefabricated small box beam a and a prefabricated small box beam b; the prefabricated-cast-in-place interface between the end of the prefabricated small box girder a and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface a, and the prefabricated-cast-in-place interface between the end of the prefabricated small box girder b and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface b; the middle area of each external prestressed steel beam is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface a and then turns through the corresponding turning block a, and is finally anchored on the bottom plate of the prefabricated small box beam a, and the other end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface b and turns through the corresponding turning block b, and is finally anchored on the bottom plate of the prefabricated small box beam b; the steering block a is installed on the web plate of the prefabricated small box girder a, and the steering block b is installed on the web plate of the prefabricated small box girder b. The structures of the steering block a and the steering block b are consistent, and as shown in fig. 11, the steering block a and the steering block b respectively comprise a web plate outer side steel plate, a web plate inner side steel plate, an anchor bolt steel bar and a tensioning base plate; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate.
When the precast box girder hidden cover beam is in the simply supported section, as shown in fig. 9, the biggest difference between the simply supported section and the continuous section is that no fulcrum bending moment acts, so the prestressed steel beam is allowed to be anchored on the precast box girder top plate, which is lower than the bottom plate in operation difficulty. Note: the continuous section has limited clearance of the hidden cover beam, so the stretching stage can be operated by a climbing vehicle, and the difficulty of stretching the prestressed steel beam on the bottom plate is not particularly high.
The simply supported section has no tension operation space at the side of the cast-in-place hidden cover beam (the beam body at the other side of the telescopic layer is constructed), so that an embedded P anchor is adopted as an anchoring section.
In other words, for the prefabricated small box girder type hidden capping beam of the simply supported section, one end of each external prestressed steel beam is anchored on the top plate of the prefabricated small box girder, and the other end is anchored in the cast-in-place hidden capping beam. Specifically, one end of each external prestressed steel beam sequentially penetrates through a prefabrication-cast-in-place interface and an anchor sealing plate, and is finally anchored on a top plate of the prefabricated small box girder after being turned by a turning block; the structure of the steering block, as shown in fig. 11, includes a web outer steel plate, a web inner steel plate, an anchor bolt steel bar and a tension pad; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate. The number of the anchor bolt reinforcing steel bars is 4-6.
The utility model discloses when using the construction, including 3 parts such as stretch-draw end construction, bellows and steel bundle installation and steel bundle stretch-draw slip casting.
1.1 stretch-draw end construction
1.1.1 continuous end tension anchoring construction
The continuous end tensioning anchoring component is manufactured according to the design drawing requirements, the inner steel plate and the outer steel plate of the web plate are welded with the anchor bolt steel bars to form a tensioning end anchoring structure, the tensioning backing plate and the inner steel plate of the web plate are welded to form a tensioning end integral structure, a welding seam between the inner steel plate of the web plate and the tensioning backing plate needs to be subjected to ultrasonic and magnetic powder 100% detection, and the continuous end tensioning anchoring component can be used after the continuous end tensioning backing plate is qualified.
Because the whole structure of the steel structure at the tensioning end is in contact with the air, the steel structure needs to be subjected to corrosion prevention measures such as galvanizing and the like after being welded and formed, and the durability of the steel structure is improved.
After the prefabricated small box girder bottom web plate steel bars are bound, a small box girder core mould is installed, then a tensioning end steel member is installed according to the designed position, and the core mould needs to be provided with holes at the position of the steel member. The web plate steel plate of the tensioning end steel component, particularly the inner web plate steel plate, must be parallel to the core die so as to ensure that the tensioning base plate is perpendicular to the web plate.
1.1.2 construction of simply supported end tensioning notch
The prefabricated small box girder structure simple support end longitudinal prestress structure stretching end based on the hidden bent cap is arranged at the position of a small box girder top plate to form a top plate stretching notch, the top plate stretching notch is provided with a pre-buried steel plate and a threaded steel bar according to design drawing construction stretching end, a part of corrugated pipes are pre-buried in a box chamber, and the later-stage corrugated pipes are connected with the residual corrugated pipes.
1.2 corrugated pipe and Steel Strand installation
After the small box girder is installed, firstly, the hidden type bent cap transverse main reinforcement construction is carried out, a stirrup space is reserved in the position of the corrugated pipe, then, the corrugated pipe and the steel beam are installed, and the small box girder installation method mainly comprises the following two steps:
1) and the plug plate of the small box girder at the continuous end is perforated in advance according to the design position, the linear corrugated pipe is installed to the tensioning base plates at the two ends, and the corrugated pipe is temporarily fixed on the hidden cover girder and the tenon constructional steel bar for ensuring the corrugated pipe line type.
2) The simple support end adopts a single-end tensioning P anchor structure, the corrugated pipes are arranged according to a design drawing and are connected with the pre-reserved corrugated pipes at the tensioning end, and the corrugated pipe joints are connected by adopting hot melting and are provided with prestressed steel beams.
1.3 stretch-draw grouting of steel bundle
And (3) after the hidden capping beam steel bar and the template project are finished, carrying out hidden capping beam and beam end tenon structural concrete pouring, and stretching prestress and grouting after the concrete strength reaches the design strength. And extra longitudinal prestress between the prefabricated box girders is provided, and the tightness of the male and female tooth structures of the hidden cover girder and the small box girder is provided, so that the shear-resistant bearing capacity of the longitudinal connecting structure is improved.
Claims (9)
1. A prestressed system for prefabricating a small box girder type hidden cover beam comprises prefabricated small box girders arranged along a bridge direction and a cast-in-place hidden cover beam arranged along a transverse bridge direction, and is characterized in that a prefabricated-cast-in-place interface in multi-protrusion tooth block engagement is arranged between the end head of the prefabricated small box girder and the cast-in-place hidden cover beam, and the prestressed system is configured along the web direction of the prefabricated small box girder and comprises an in-vivo prestressed system and an in-vitro prestressed system;
the in-vivo prestressed system comprises a plurality of in-vivo prestressed steel bundles, wherein the anchoring points of the in-vivo prestressed steel bundles are arranged at the end part of the web plate of the prefabricated small box girder and are distributed along the height direction of the web plate of the prefabricated small box girder;
the in-vitro prestressed system comprises a plurality of in-vitro prestressed steel bundles; an inclination angle alpha exists between each external prestressed steel beam and the web plate of the prefabricated small box girder;
when the prefabricated small box girder type hidden cover beam is positioned in a continuous section, the middle area of each external prestressed steel bundle is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on one side of the cast-in-place hidden cover beam, and the other end of each external prestressed steel bundle is anchored on the bottom plate of the prefabricated small box girder on the other side of the cast-in-place hidden cover beam;
when the small box girder type hidden cover girder is in the simply supported section, one end of each external prestressed steel bundle is anchored on the top plate of the small box girder, and the other end of each external prestressed steel bundle is anchored in the cast-in-place hidden cover girder.
2. The prestressing system for precast small box girder hidden cover beams according to claim 1, wherein when the precast small box girder hidden cover beams are in a continuous section, precast small box beams are respectively arranged on two sides of the cast-in-place hidden cover beam, namely a precast small box beam a and a precast small box beam b; the prefabricated-cast-in-place interface between the end of the prefabricated small box girder a and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface a, and the prefabricated-cast-in-place interface between the end of the prefabricated small box girder b and the cast-in-place hidden cover girder is a prefabricated-cast-in-place interface b;
the middle area of each external prestressed steel beam is horizontally buried in the cast-in-place hidden cover beam and distributed along the height direction of the cast-in-place hidden cover beam, one end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface a and then turns through the corresponding turning block a, and is finally anchored on the bottom plate of the prefabricated small box beam a, and the other end of each external prestressed steel beam penetrates through the prefabrication-cast-in-place interface b and turns through the corresponding turning block b, and is finally anchored on the bottom plate of the prefabricated small box beam b; the steering block a is installed on the web plate of the prefabricated small box girder a, and the steering block b is installed on the web plate of the prefabricated small box girder b.
3. The prestressing system for prefabricating the small box girder hidden cover beam according to claim 2, wherein the steering blocks a and b respectively comprise a web outer steel plate, a web inner steel plate, anchor bolts and tensioning cushion plates; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate.
4. The pre-stressing system for the precast small box girder hidden cover beam as claimed in claim 1, wherein when the precast small box girder hidden cover beam is in the simply supported section, one end of each external pre-stressing steel beam passes through the precast-cast-in-place interface and the anchor sealing plate in sequence, then is turned by the turning block and finally anchored on the top plate of the precast small box girder;
the steering block comprises a web plate outer side steel plate, a web plate inner side steel plate, an anchor bolt steel bar and a tensioning base plate; the web outside steel sheet is installed at the web inboard of prefabricated little case roof beam, and the inboard steel sheet of web passes through the crab-bolt reinforcing bar and is connected with web outside steel sheet, and the tensioning backing plate is connected with the inboard steel sheet of web, and external prestressing steel bundle passes the through-hole setting of seting up on the tensioning backing plate.
5. The prestressing system for precast trabecular hidden cover beams according to claim 3 or 4, wherein the number of anchor bars is 4-6.
6. The pre-stress system for the prefabricated small box girder type hidden cover beam as claimed in claim 1, wherein the prefabricated-cast-in-place interface comprises an end head of the prefabricated small box girder and a cast-in-place concrete joint meshed with the end head of the prefabricated small box girder; wherein:
the end of the small prefabricated box girder comprises a box girder bottom plate end, a box girder top plate end and two box girder web plate ends positioned between the box girder bottom plate end and the box girder top plate end; the outer side surface of the end of the box girder bottom plate and the outer side surface of the end of the box girder top plate are positioned in the same plane; a plurality of web raised teeth are arranged on the outer sides of the ends of the web plates of the two box girders; the web convex teeth are arranged on the top of the web convex teeth, the upper end of the web convex teeth starts from the outer side surface of the end of the box girder top plate, the lower end of the web convex teeth crosses the connecting limit of the end of the box girder top plate and the end of the box girder web plate and ends at the outer side surface of the end of the box girder web plate, and the rest web convex teeth are arranged on the outer side surface of the end of the box girder web plate.
7. The prestressing system for precast trabecular hidden canopy beams according to claim 6, wherein the number of web lobes matches the number of in vitro prestressed tendons.
8. The pre-stressing system for precast trabecular hidden canopy beams as claimed in claim 7, wherein the number of web convex teeth provided at the end of the single-sided box girder web is 3, and the number of said single-sided external prestressed steel bundles is 3.
9. The pre-stressing system for precast small box girder hidden bent cap according to claim 7, wherein there are 4 in-vivo pre-stressed steel bundles provided in the precast small box girder; correspondingly, 4 individual internal prestressed steel strand anchoring points are arranged at the end part of the prefabricated small box girder web plate along the height direction.
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| CN113512932A (en) * | 2021-03-19 | 2021-10-19 | 宁波市政工程建设集团股份有限公司 | Prestressed steel beam connected prefabricated small box girder type hidden cover beam and construction method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113512932A (en) * | 2021-03-19 | 2021-10-19 | 宁波市政工程建设集团股份有限公司 | Prestressed steel beam connected prefabricated small box girder type hidden cover beam and construction method thereof |
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