An external prestressing system of a UHPC composite beam and a construction method thereof

Abstract

The application discloses a kind of UHPC composite beam's external prestressing system and its construction method, including UHPC composite beam in external prestressing bundle, external prestressing bundle embedded pipe in fulcrum high area, anchoring tooth block;The bridge deck of UHPC composite beam includes upper steel bottom plate with PBL shear key and UHPC panel;Steel bottom plate includes flat bottom plate and side bottom plate, and the upper part of steel girder diaphragm is surrounded by adjacent side bottom plate to form bridge deck fulcrum high area;External prestressing bundle is anchored at both ends in anchoring tooth block;External prestressing bundle passes through from the embedded pipe in fulcrum high area;Anchoring tooth block includes tooth block end plate, tooth block bottom plate and tooth block side plate and internal UHPC, and the anchoring area where anchoring tooth block is located, two PBL shear keys directly extend downward to steel bottom plate below as tooth block side plate.The UHPC composite beam external prestressing system of the application can avoid setting internal prestressing to increase the thickness of bridge deck, reduce the dead weight, simplify the structure and construction technology of anchoring tooth block, and improve the reliability and force transmission efficiency of anchoring tooth block.

Description

Technical Field

[0001] This invention relates to an external prestressing system for UHPC composite beams, and also to a construction method for the external prestressing system of UHPC composite beams. Background Technology

[0002] The bridge deck of the composite bridge is made of ultra-high performance concrete (UHPC) with high tensile and compressive strength, low chloride ion diffusion coefficient, zero shrinkage and small creep after steam curing. It can effectively avoid the long-standing problems that have plagued the engineering community, such as fatigue cracking, pavement damage and easy cracking of ordinary concrete bridge decks caused by using only orthotropic steel bridge decks.

[0003] For the tension zone of the UHPC composite beam at mid-span or the negative bending moment zone of the UHPC composite continuous beam support in a double-tower cable-stayed bridge, prestressing needs to be set according to the stress condition of the UHPC bridge deck. Since the UHPC composite beam bridge deck is relatively thin, prestressing can be carried out in flat corrugated tubes between the upper and lower layers of steel mesh by appropriately thickening it. However, the long-strand flat tubes are prone to deformation and blockage during segmental connection and tendon threading construction. Moreover, the prestressed corrugated tubes will fill the gaps between the steel bars, affecting the density of the UHPC and the distribution of steel fibers, thereby affecting the performance of the UHPC. Summary of the Invention

[0004] The first technical problem to be solved by this invention is to provide an external prestressing system for UHPC composite beams, which has a simple layout and is suitable for various types of bridge composite beam structures.

[0005] The second technical problem to be solved by this invention is to provide a construction method for an external prestressed system of UHPC composite beams, which is convenient to construct.

[0006] To solve the first technical problem of this invention, the technical solution adopted by this invention is as follows:

[0007] An external prestressing system for a UHPC composite beam includes external prestressing tendons in the UHPC composite beam, embedded pipes for external prestressing tendons in the support heightening zone, and anchoring teeth. The UHPC composite beam includes a bridge deck and a steel main beam. The bridge deck includes several steel base plates with PBL shear keys on the upper part and UHPC panels cast on the steel base plates. The steel base plates include flat base plates and side base plates. Each steel base plate is a truncated pyramid steel member with an open bottom surface and closed top and side surfaces. The PBL shear keys are arranged on the upper surface of the flat base plates along the bridge direction. The side base plates are welded to the upper flanges of the steel main beam. The support heightening zone of the bridge deck is formed above the transverse diaphragm of the steel main beam by adjacent side base plates. The two ends of the external prestressing tendons are anchored to the anchoring teeth. The external prestressing tendons pass through the embedded pipes in the support heightening zone above the transverse diaphragm.

[0008] The anchoring tooth block includes an anchoring box consisting of a tooth block end plate, a tooth block bottom plate, and a tooth block side plate. An anchor plate is installed inside the anchoring box. UHPC is cast inside the anchoring box to form the anchoring tooth block. The anchoring area where the anchoring tooth block is located is extended downwards from the two PBL shear keys to the bottom of the steel base plate as the tooth block side plate. The flat bottom plate between the two PBL shear keys has a notch in the anchoring area. The tooth block bottom plate is located below the steel base plate and connects to the two tooth block side plates. The tooth block end plate, the tooth block bottom plate, and the tooth block side plates are connected to form the anchoring box.

[0009] This invention involves installing external prestressing tendons beneath the bridge deck. These tendons pass through pre-drilled holes in the side base plate, and the anchoring blocks, UHPC deck, and steel base plate are integrated into a single unit. By implementing this external prestressing system, the bridge deck thickness is not increased, reducing the self-weight. The structure and construction process of the anchoring blocks are simplified, improving their reliability and force transmission efficiency. This also avoids affecting the density of the UHPC and the distribution of steel fibers, thus better utilizing the superior properties of the UHPC material.

[0010] The present invention also has the following preferred designs:

[0011] The embedded pipe of the present invention can be a seamless steel pipe or an HDPE pipe, preferably a seamless steel pipe, which can be welded to the side plate of the steel base plate to form a whole, and the positioning is accurate.

[0012] The present invention fills the gap between the external prestressed tendon and the outlets at both ends of the pre-embedded pipe with silicone structural sealant or rubber pads to form a constraint damping device.

[0013] The main body thickness of the bridge deck of this invention is 120-200 mm, the thickness of the bridge deck at the support heightened area is 220-300 mm, and the thickness of the steel base plate is 6-16 mm.

[0014] The bridge deck support heightening area of ​​this invention is increased by 100-120 mm. The diameter of the pre-embedded pipe is 89-108 mm and the wall thickness is 5-8 mm. The inner lining of the pre-embedded pipe is a nylon pipe or HDPE pipe with a wall thickness of 2.9-8.2 mm to prevent wear of the epoxy protective layer of the external prestressed tendons.

[0015] The external prestressing strands of this invention use single replaceable unbonded epoxy steel strands. After the pre-reserved pipes, wire-split pipes, and wire-split plates of the external prestressing strands are installed in the anchorage box, UHPC is poured inside to form anchorage teeth. The wire-split plates are lined at the outlet of the pre-reserved pipes, allowing single prestressing steel strands to pass through and be replaced.

[0016] The anchoring tooth block of the present invention has shear studs provided on the inner side of the bottom plate and the side plate of the tooth block.

[0017] The steel main beam of the present invention is any one of PK steel box girder, channel steel box girder, double-sided box steel box girder, I-beam steel main beam, and steel truss beam, so that the steel bottom plate is connected to the upper flange of the longitudinal web or transverse diaphragm of the steel main beam.

[0018] The bridge deck of this invention is an S-UHPC ultra-high performance concrete composite bridge deck or a UHPC ultra-high performance concrete bridge deck. The S-UHPC ultra-high performance concrete composite bridge deck is composed of cast UHPC and a steel base plate. As another feasible implementation, the steel base plate may not be set under the UHPC bridge deck. Temporary formwork is used to cast a bridge deck and anchoring teeth with the same shape as the above-mentioned composite bridge deck. The bridge deck and the steel main beam form a composite beam, and an external prestressing system is set under the bridge deck.

[0019] To solve the second technical problem of this invention, the technical solution adopted by this invention is as follows:

[0020] A construction method for the external prestressed system of the above-mentioned UHPC composite beam, characterized by comprising the following steps:

[0021] S1: The main steel beam is divided into several segments. The bridge deck steel bottom plate is pre-processed: the pipe holes for installing the embedded pipes are pre-processed on the transverse side bottom plate of the bridge deck steel bottom plate corresponding to the position of the embedded pipe. The tooth block bottom plate, anchor plate, tooth block side plate of the anchoring tooth block are welded together with the steel bottom plate and then the embedded pipe is fixed by welding. The inner lining pipe of the embedded pipe and the inner lining wire plates at both ends are installed.

[0022] S2: In the steel beam assembly plant, the steel bottom plate is welded to the two bottom plates on both sides in the longitudinal direction of the bridge and the two bottom plates on both sides in the transverse direction of the bridge. Then, the PBL shear key is welded to the upper surface of the flat bottom plate to form the steel bottom plate, and then welded to the upper flange of the corresponding segment of the steel main beam.

[0023] S3: In the prefabrication yard of composite beams, install the reinforcing steel mesh of the bridge deck, pour UHPC to form each segment of the bridge deck, perform static curing and high temperature steam curing, and reserve wet joints between adjacent bridge deck segments.

[0024] S4: The steel main beams are constructed on-site using a bridge deck crane for suspended assembly or on a support frame.

[0025] S5: After static curing of ultra-high performance concrete for wet joints, high-temperature steam curing is carried out.

[0026] S6: Install and tension the external prestressed tendons, and take measures to prevent corrosion of the anchor heads.

[0027] In this invention, the PBL (Perfobond Strip Connector) shear key is a perforated steel plate connector.

[0028] In this invention, the HDPE (High Density Polyethylene) pipe is a high-density polyethylene pipe.

[0029] In this invention, the PK steel box girder is: the main girder of the Pasco Kennewick Bridge in Washington State was the first to adopt an open beam cross-section with triangular side boxes. This cross-section is subsequently referred to as the PK cross-section, and the PK steel box girder is a steel beam that adopts the PK cross-section.

[0030] In this invention, S-UHPC (Steel-UHPC) refers to a steel-ultra-high performance concrete composite structure.

[0031] The present invention has the following beneficial effects

[0032] 1. The UHPC composite beam external prestressing system of the present invention can avoid increasing the bridge deck thickness by setting internal prestressing, reduce the self-weight, simplify the structure and construction process of anchoring teeth, and improve the reliability and force transmission efficiency of anchoring teeth.

[0033] 2. In the external prestressing system of the UHPC composite beam of the present invention, in the non-prestressed anchorage section, only the external prestressing tendons need to be installed in the pre-reserved pipe holes on the side bottom plate of the steel bottom plate. The bridge deck structure can be consistent with that of conventional standard bridges. The purpose of setting prestress according to the stress condition of UHPC bridge deck can be achieved through simple structure. It can avoid the impact of dense prestressing pipes on the compactness of UHPC and steel fiber distribution, and better utilize the excellent properties of UHPC material.

[0034] 3. In the external prestressed system of the UHPC composite beam of the present invention, in the prestressed anchorage zone, the PBL shear key extends downward to the bottom of the bridge deck as a toothed block side plate, which is connected with the toothed block bottom plate, toothed block end plate and anchor plate. By setting shear nails on the toothed block side plate and toothed block bottom plate, the wall plate of the anchored toothed block is effectively connected to the UHPC bridge deck to form a whole under stress. The structure is simple and easy to construct.

[0035] 4. The UHPC composite beam external prestressing system of the present invention can be applied to any type of steel main beam, such as PK steel box girder, channel steel box girder, double-sided box steel box girder, I-beam steel main beam, steel truss beam, etc., and has a wide range of applications. Attached Figure Description

[0036] Figure 1 This is an elevation view of an external prestressing system for a UHPC composite beam according to the present invention;

[0037] Figure 2 This is a top view of the steel base plate in the embodiment;

[0038] Figure 3 This is a side cross-sectional view of the steel base plate in the embodiment;

[0039] Figure 4 This is a schematic diagram of the embedded pipe of the external prestressing system passing through the support heightening area in the embodiment;

[0040] Figure 5 This is a schematic elevation view of the anchoring tooth block of the external prestressing system in the embodiment;

[0041] Figure 6 yes Figure 5 A-A cross-section diagram;

[0042] Figure 7 yes Figure 5 B-B cross-section diagram;

[0043] Figure 8 yes Figure 5 C-C section view;

[0044] Figure 9 This is a cross-sectional schematic diagram of the arrangement of external prestressed tendons in the supported heightened area of ​​the main beam according to the present invention.

[0045] Figure 10 This is a cross-sectional schematic diagram of the arrangement of external prestressed tendons in the unsupported heightened area of ​​the main beam according to the present invention.

[0046] Explanation of reference numerals in the attached drawings: 100-steel main beam, 110-longitudinal web, 120-diaphragm, 200-steel bottom plate, 210-flat bottom plate, 220-side bottom plate, 230-PBL shear key, 300-support heightened area, 400-UHPC panel, 500-stressed steel mesh, 600-external prestressed tendon, 610-embedded pipe, 620-anchoring tooth block, 621-tooth block bottom plate, 622-tooth block end plate. Detailed Implementation

[0047] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention.

[0048] Example

[0049] like Figures 1 to 10The diagram illustrates an external prestressing system for a UHPC composite beam, comprising external prestressing tendons 600 within the UHPC composite beam, embedded external prestressing tendon tubes 610 in the support heightening zone 300, and anchoring teeth 620. The UHPC composite beam includes a bridge deck and a steel main beam 100. The bridge deck includes several steel base plates 200 with PBL shear keys 230 on the upper part and UHPC panels 400 cast on the steel base plates 200. The steel base plates 200 include a flat bottom plate 210 and side bottom plates 220. Each steel base plate 200 is a frustum-shaped steel member with an open bottom surface and closed top and side surfaces. PBL shear keys 230 are arranged longitudinally on the upper surface of the flat bottom plate 210. The side bottom plate 220 is welded to the upper flange of the steel main beam 100. The support elevation area 300 of the bridge deck is formed by the adjacent side bottom plates 220 above the transverse diaphragm 120 of the steel main beam 100. The two ends of the external prestressed tendons 600 are anchored to the anchoring teeth 620. The external prestressed tendons 600 pass through the pre-embedded pipes 610 in the support elevation area 300 above the transverse diaphragm 120.

[0050] See Figures 5 to 8 The anchoring tooth block 620 includes an anchoring box consisting of a tooth block end plate 622, a tooth block bottom plate 621, and tooth block side plates. An anchor plate, an existing structure for prestressed anchoring (not shown in the figure), is installed inside the anchoring box. UHPC is cast inside the anchoring box to form the anchoring tooth block 620. The anchoring area where the anchoring tooth block 620 is located extends downwards from two PBL shear keys 230 below the steel base plate 200, serving as the tooth block side plates. A notch is cut into the flat bottom plate 210 between the two PBL shear keys 230 in this anchoring area. The tooth block bottom plate 621, located below the steel base plate 200, connects to the two tooth block side plates. The tooth block end plate 622, the tooth block bottom plate 621, and the tooth block side plates are connected to form the anchoring box. The anchoring tooth block 620 can be integrally formed with the UHPC panel 400.

[0051] As a preferred embodiment:

[0052] The embedded pipe 610 can be made of seamless steel pipe or HDPE pipe. In this embodiment, seamless steel pipe is preferred. It can be welded to the side plate 220 of the steel base plate 200 as a whole, and the positioning is accurate.

[0053] A constraint damping device is formed by filling the gap between the external prestressed tendon 600 and the two ends of the pre-embedded pipe 610 with silicone structural sealant or rubber pads.

[0054] In this embodiment, the main body thickness of the bridge deck is 120-200 mm, the thickness of the bridge deck at the support heightening area 300 is 220-300 mm, the thickness of the steel base plate 200 is 6-16 mm, and the main body thickness of the UHPC panel 400 of the composite bridge deck is taken in the range of 120-190 mm, preferably 150 mm.

[0055] The bridge deck support heightening zone 300 is increased by 100-120 mm. The diameter of the pre-embedded pipe 610 is 89-108 mm and the wall thickness is 5-8 mm. The inner lining of the pre-embedded pipe 610 is a nylon pipe or HDPE pipe with a wall thickness of 2.9-8.2 mm. Strict measures are taken to prevent wear on the epoxy protective layer of the external prestressed tendons 600.

[0056] The PBL shear keys 230 are arranged along the bridge deck length direction in the longitudinal direction and are arranged in parallel at intervals along the bridge deck width direction in the transverse direction. The external prestressed tendons 600 are located between two adjacent PBL shear keys 230 in the transverse direction.

[0057] In this embodiment, the PBL shear keys 230 above the flat bottom plate 210 are 90 mm high and 8-10 mm thick, and are arranged side by side with a horizontal bridge spacing of 450 mm. The spacing can be 400 mm to 600 mm depending on the actual situation. The height of the PBL shear keys 230 can be in the range of 60-110 mm, and the thickness can be in the range of 8-12 mm.

[0058] In this embodiment, the external prestressing strand 600 uses a single replaceable unbonded epoxy steel strand. After the pre-reserved pipe, wire-distributing pipe, and wire-distributing plate of the external prestressing strand 600 are installed in the anchoring box, UHPC is poured inside to form the anchoring tooth block 620. The outlet of the pre-reserved pipe is lined with a wire-distributing plate, which allows for the passage and replacement of a single prestressing steel strand. Shear studs are provided on the inner side of the tooth block base plate 621 and the tooth block side plate of the anchoring tooth block 620.

[0059] The main steel beam 100 can be any one of the following: PK steel box girder, channel steel box girder, double-sided box steel box girder, I-beam steel main beam, or steel truss beam. The steel base plate 200 is connected to the upper flange of the longitudinal web 110 or transverse diaphragm 120 of the main steel beam 100, forming a closed steel box girder, plate girder, double-sided box girder, or steel truss beam. In this embodiment, the spacing between adjacent transverse diaphragms 120 on the main steel beam 100 is 3000–4500 mm, preferably 3500 mm. The PBL shear keys 230 on both sides of the reserved duct approximately 1.2–1.5 transverse diaphragm spacings in front of the anchorage connection of the external prestressed tendons 600 extend below the bridge deck to form the toothed side plates of the anchorage toothed blocks 620.

[0060] Construction method:

[0061] A construction method for the external prestressed system of the above-mentioned UHPC composite beam includes the following steps:

[0062] S1: The main steel beam 100 is divided into several segments. The bridge deck steel bottom plate 200 is pre-processed: the transverse side bottom plate 220 of the bridge deck steel bottom plate 200 corresponding to the position of the embedded pipe 610 is pre-processed to install the pipe hole of the embedded pipe 610. The tooth block bottom plate 621, anchor plate, tooth block side plate of the anchoring tooth block 620 are welded together with the steel bottom plate 200 and then the embedded pipe 610 is fixed by welding. The inner lining pipe of the embedded pipe 610 and the inner lining wire plates at both ends are installed.

[0063] S2: In the steel main beam assembly plant, the steel bottom plate 200 is welded to the two side bottom plates 220 in the longitudinal direction of the bridge and the two side bottom plates 220 in the transverse direction of the bridge. Then, the PBL shear key 230 is welded to the upper plate surface of the flat bottom plate 210 to form the steel bottom plate 200, and then welded to the upper flange of the corresponding segment of the steel main beam 100.

[0064] S3: In the composite beam prefabrication plant, install the 500-mesh reinforcing steel mesh for the bridge deck, pour UHPC to form each segment of the bridge deck, perform static curing and high-temperature steam curing, and reserve wet joints between adjacent bridge deck segments.

[0065] S4: At the bridge site, the steel main beam 100 is constructed by cantilever assembly or assembly on a support frame. The cantilever assembly can be carried out using a bridge deck crane.

[0066] S5: After the wet joint UHPC is poured and static curing is carried out, high-temperature steam curing is performed.

[0067] S6: Install and tension the external prestressed tendons 600, and take measures to prevent corrosion of the anchor heads.

[0068] The bridge deck of this invention is an S-UHPC ultra-high performance concrete composite bridge deck or a UHPC ultra-high performance concrete bridge deck. The S-UHPC ultra-high performance concrete composite bridge deck is composed of cast UHPC and a steel base plate. In other embodiments, when using a UHPC ultra-high performance concrete bridge deck, the steel base plate 200 may not be provided below the UHPC panel. A temporary formwork is used to cast a UHPC panel and anchoring teeth with the same shape as the above-mentioned composite bridge deck. The UHPC panel and the steel main beam form a composite beam, and the above-mentioned external prestressing tendons 600 are provided below the bridge deck. The external prestressing tendons 600 are also provided with embedded pipes 610 at the support heightened area 300.

[0069] The above embodiments are merely preferred embodiments of the present invention, but should not be construed as limiting the invention. Any modifications and improvements made based on the concept of the present invention should fall within the protection scope of the present invention, and the specific protection scope is subject to the claims.

Claims

1. An external prestressing system for UHPC composite beams, characterized in that, The bridge deck includes external prestressing tendons in a UHPC composite beam, embedded pipes for external prestressing tendons in the support heightening zone, and anchoring teeth. The UHPC composite beam includes a bridge deck and a steel main beam. The bridge deck includes several steel base plates with PBL shear keys on the upper part and UHPC panels cast on the steel base plates. The steel base plates include flat base plates and side base plates. Each steel base plate is a truncated pyramidal steel member with an open bottom surface and closed top and side surfaces. The PBL shear keys are arranged on the upper surface of the flat base plates along the bridge direction. The side base plates are welded to the upper flanges on the steel main beam. The support heightening zone of the bridge deck is formed above the transverse diaphragms of the steel main beam by adjacent side base plates. The two ends of the external prestressing tendons are anchored to the anchoring teeth. The external prestressing tendons pass through the embedded pipes in the support heightening zone above the transverse diaphragms. The anchoring tooth block includes an anchoring box consisting of a tooth block end plate, a tooth block bottom plate, and a tooth block side plate. An anchor plate is installed inside the anchoring box. UHPC is cast inside the anchoring box to form the anchoring tooth block. The anchoring area where the anchoring tooth block is located is extended downwards from the two PBL shear keys to the bottom of the steel base plate as the tooth block side plate. The flat bottom plate between the two PBL shear keys has a notch in the anchoring area. The tooth block bottom plate is located below the steel base plate and connects to the two tooth block side plates. The tooth block end plate, the tooth block bottom plate, and the tooth block side plates are connected to form the anchoring box. Shear studs are provided on the inner sides of the tooth block bottom plate and the tooth block side plates of the anchoring tooth block.

2. The external prestressing system of the UHPC composite beam according to claim 1, characterized in that: The external prestressed tendon embedded pipe in the support heightening zone is a seamless steel pipe or HDPE pipe.

3. The external prestressing system of the UHPC composite beam according to claim 2, characterized in that: The gap between the external prestressed tendon and the outlets at both ends of the embedded pipe is filled with silicone structural sealant or rubber gaskets to form a constraint damping device.

4. The external prestressing system of the UHPC composite beam according to claim 1, characterized in that: The main body thickness of the bridge deck is 120-200 mm, the thickness of the bridge deck at the support heightened area is 220-300 mm, and the thickness of the steel base plate is 6-16 mm.

5. The external prestressing system of the UHPC composite beam according to claim 4, characterized in that: The bridge deck support heightening area is increased by 100-120 mm, the pre-embedded pipe has a diameter of 89-108 mm and a wall thickness of 5-8 mm, and the inner lining of the pre-embedded pipe is a nylon pipe or HDPE pipe with a wall thickness of 2.9-8.2 mm.

6. The external prestressing system of the UHPC composite beam according to claim 1, characterized in that: The external prestressing strands are single replaceable unbonded epoxy steel strands, and the anchorage box contains reserved pipes, wire-splitting pipes, and wire-splitting plates for installing the external prestressing strands.

7. A construction method for an external prestressed system of a UHPC composite beam as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: The main steel beam is divided into several segments. The bridge deck steel bottom plate is pre-processed: the pipe holes for installing the embedded pipes are pre-processed on the transverse side bottom plate of the bridge deck steel bottom plate corresponding to the position of the embedded pipe. The tooth block bottom plate, anchor plate, tooth block side plate of the anchoring tooth block are welded together with the steel bottom plate and then the embedded pipe is fixed by welding. The inner lining pipe of the embedded pipe and the inner lining wire plates at both ends are installed. S2: Weld the steel base plate on both sides along the bridge direction to the steel base plate on both sides in the transverse direction, then weld the PBL shear key to the upper surface of the flat base plate to form a steel base plate, and then weld it together with the upper flange of the corresponding segment of the steel main beam. S3: Install the reinforcing steel mesh for the bridge deck, pour UHPC to form each segment of the bridge deck, perform high-temperature steam curing after static curing, and reserve wet joints between adjacent bridge deck segments. S4: The steel main beam is constructed by cantilever assembly or assembly on a support frame; S5: After static curing of ultra-high performance concrete for wet joints, high-temperature steam curing is carried out. S6: Install and tension the external prestressed tendons, and take measures to prevent corrosion of the anchor heads.

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