Method for stable construction of UHPC thin-wall shell bent cap

Abstract

The invention provides a method for stable construction of a UHPC thin-wall shell bent cap. The method comprises the steps that S1, a pit used for forming a UHPC thin-wall shell is excavated in the ground; s2, an outer formwork is arranged in the pit; s3, UHPC concrete is poured in the outer formwork according to the design quantity; s4, the assembled inner formwork and inner support are hoisted to the position over the outer formwork; s5, downward pressure is applied to the inner formwork and the inner support, the UHPC concrete is pressed through the inner formwork, and the liquid level of the UHPC concrete rises between the inner formwork and the outer formwork till the UHPC concrete is pressed downwards to the specified thickness; and S6, after the UHPC concrete reaches the demolding strength, demolding curing is conducted, and the UHPC thin-wall shell is formed. The UHPC thin-wall shell of the bent cap can be manufactured only by hoisting the UHPC thin-wall shell to the pier column, arranging the corresponding steel reinforcement framework and the corresponding prestressed cable and finally pouring common concrete without erecting a temporary support and a template, so that the construction process is effectively simplified, the construction time is shortened, and pollution and noise are reduced.

Description

Technical Field

[0001] The present invention relates to the field of capping beam construction, and particularly to a method for the stable construction of a UHPC thin-walled outer shell capping beam. Background Art

[0002] For the construction of concrete bridges, concrete construction is usually carried out on site, and in-situ concrete construction requires a large number of formworks and temporary supports. Therefore, there are disadvantages such as a large amount of on-site work, complex construction processes, long construction periods, relatively difficult quality assurance, large construction land occupation, and high construction risks. It not only consumes a large amount of energy but also has an adverse impact on the surrounding environment. In addition, the scaffolds and capping beam formworks erected on site are prone to defects, which also have an adverse impact on the quality of the capping beam. Moreover, during the construction of in-situ concrete bridges, the construction quality of the bridge is also restricted by many factors such as construction space, seasonal climate, and surrounding environment, and the construction of the bridge will have a serious impact on the road traffic under the bridge, and even the road traffic under the bridge needs to be interrupted.

[0003] Therefore, precast concrete has emerged as the times require. However, for the hoisting and positioning construction method of integral precast concrete capping beams, although it reduces the impact of construction on the traffic under the bridge compared with the construction method of in-situ pouring of concrete, the large weight of the capping beam causes great difficulties in the transportation and hoisting of the capping beam. In addition, the above construction method is also restricted by many factors such as manufacturing sites, hoisting equipment, hoisting space, and transportation facilities.

[0004] The precast concrete assembly construction technology has become an important development direction of China's engineering construction, and the precast assembly technologies of components such as the superstructure of bridges, bridge piers, and pile foundations have also become mature. However, the assembly problem of large-tonnage capping beams has not been well solved. Especially for large-cantilever capping beams, their self-weight is large, and transportation and hoisting are very difficult, and it is even more difficult to use the assembly construction method. Therefore, a method for the stable construction of a UHPC thin-walled outer shell capping beam is proposed to solve the above problems. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for the stable construction of a UHPC thin-walled outer shell capping beam, to solve the problems that in-situ concrete construction requires a large number of formworks and temporary supports, has a large amount of on-site work, complex construction processes, long construction periods, relatively difficult quality assurance, large construction land occupation, and high construction risks, and the transportation and hoisting of traditional precast concrete capping beams are also greatly difficult and restricted by many factors such as manufacturing sites, hoisting equipment, hoisting space, and transportation facilities.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a method for the stable construction of a UHPC thin-walled outer shell capping beam, the method comprising: S1. Excavate a pit on the ground for forming the UHPC thin-walled shell; S2. Set up an external formwork in the pit; S3. Pour UHPC concrete into the external formwork according to the designed quantity; S4. Hoist the assembled internal formwork and internal support to directly above the external formwork; S5. Apply a downward pressure to the internal formwork and internal support, and use the internal formwork to compact the UHPC concrete, so that the liquid level of the UHPC concrete rises between the internal formwork and the external formwork until it is pressed down to the specified thickness; S6. After the UHPC concrete reaches the demoulding strength, carry out demoulding and curing to form the UHPC thin-walled shell.

[0007] In the preferred solution, the external formwork is an openable and closable structure, specifically including a support frame anchored in the pit. On both sides of the top of the support frame, opening and closing plates are hinged. An extended support structure is arranged on the outer side of the opening and closing plates. An opening and closing oil cylinder is hinged on the outer side of the extended support structure. The other side of the opening and closing oil cylinder is hinged with an anchor. The anchor is anchored on the top wall of the side of the pit. A bottom external form and a side external form are respectively fixed on the top of the support frame and the inner side of the opening and closing plates; The extended support structure includes a plurality of extended vertical plates arranged on the outer side of the opening and closing plates, and a connecting cross plate connecting all the extended vertical plates. An extended hinge seat hinged with the opening and closing oil cylinder is arranged on the outer side of the top of the extended vertical plates; In step S2, the external formwork is in the closed state, and a reinforcing rod is arranged between the opening and closing plates and the side wall of the pit.

[0008] In the preferred solution, in step S3, after the UHPC concrete is poured, it is also necessary to vibrate it. The specific method is: install vibrators on both sides of the bottom of the external formwork, and use the vibrators to level the liquid surface of the UHPC concrete.

[0009] In the preferred solution, the internal formwork in step S4 includes the formwork assembled on the bottom and two sides of the internal support, and shear studs arranged in an array on the formwork. The hoisting of the internal formwork and the internal support is completed by a hoisting device. The hoisting device includes a gantry walking trolley arranged on both sides of the pit and a plurality of electric hoists arranged on the gantry walking trolley; In step S4, a pressing mechanism for applying pressure to the inner formwork and the inner support is suspended by an electric hoist. The pressing mechanism includes two movable crossbeams slidably arranged between the columns of the gantry walking trolley. A lifting lug for connecting the electric hoist is provided at the top of the upper movable crossbeam. A pressing cylinder and a connection locking mechanism are arranged between the two movable crossbeams. A lifting sliding seat and a lateral adjustment cylinder are provided at the bottom of the lower movable crossbeam. The lifting sliding seat is slidably connected to the movable crossbeam, and the output end of the lateral adjustment cylinder is connected to the lifting sliding seat. Height locking mechanisms for fixing the posture are provided between the two movable crossbeams and between the lifting sliding seat and the columns of the gantry walking trolley. The connection locking mechanism includes a docking sleeve rod and a docking insertion rod respectively arranged on the opposite sides of the two movable crossbeams. A docking groove for inserting the docking insertion rod is provided at the end of the docking sleeve rod, and docking pin holes are provided on the docking ends of the docking insertion rod and the docking sleeve rod. A docking automatic pin corresponding to the docking pin hole is provided on the outside of the docking sleeve rod. When the hoisting equipment hoists the inner formwork and the inner support, the connection locking mechanism is in a locked state. The height locking mechanisms of the two movable crossbeams are released, and the two movable crossbeams are lowered by the electric hoist to a preset height. Then the height locking mechanism of the upper movable crossbeam is locked, and the connection of the connection locking mechanism is released. The lower movable crossbeam is driven by the pressing cylinder to drive the lifting sliding seat to the top of the inner formwork and the inner support and connect. Then the lower movable crossbeam and the lifting sliding seat are lifted by the pressing cylinder, and the connection locking mechanism is connected. The two movable crossbeams are lifted to a certain height by the electric hoist, and the gantry walking trolley travels to above the outer formwork.

[0010] In the preferred solution, the specific method of pressing in step S5 is as follows: S51. Anchor the gantry walking trolley to the ground; S52. Start the electric hoist to make the two movable crossbeams slide down along the columns of the gantry walking trolley to a specified height until the inner formwork and the inner support are located above the outer formwork, and lock the upper movable crossbeam through the height locking mechanism; S53. Precisely adjust the lateral position of the inner formwork by using the lateral adjustment cylinder; S54. Release the connection locking mechanism between the two movable crossbeams, start the pressing cylinder to make the lower movable crossbeam drive the lifting sliding seat to descend, so as to press the UHPC concrete by using the downward pressure of the inner formwork and the inner support until it stops after being pressed to the designed thickness; S55. Lock the lower movable crossbeam through the height locking mechanism to prevent floating, and release the pressure of the pressing cylinder. In the preferred solution, after the lateral position of the inner formwork in step S53 is adjusted, a limit card is installed between the tops of the inner formwork and the outer formwork. The limit card is in an inverted U shape and is fixed on the inner formwork and can descend with the inner formwork. In a preferred embodiment, the inner support includes two symmetrically arranged side support frames. The bottoms of the two side support frames on the opposite sides are hinged, and a wedge block is inserted at the top. The demolding process in step S6 includes the demolding of the outer formwork and the removal of the inner support. Among them, when demolding the outer formwork, the reinforcement rod is removed, and the opening and closing oil cylinder is contracted, so that the opening and closing plate and the side outer formwork are rotated and demolded along the bottom hinge point. The method for removing the inner support is as follows: Disconnect the connection between the inner support and the inner formwork, and remove the wedge block on the inner support, so that the middle part of the inner support releases force and rotates inward along the hinge point to approach each other, so that the side support frames on both sides are gradually separated from the inner formwork. Then connect the separated inner support to the hoisting sliding seat, contract the compaction oil cylinder, lift the inner support, and finally release the anchoring of the gantry walking trolley to transport the inner support away.

[0011] In a preferred embodiment, the specific curing method in step S6 is as follows: After the demolding process is completed, high-temperature water is injected into the pit, heating equipment is arranged in the pit, and finally a cover plate is covered above the pit for sealing.

[0012] In a preferred embodiment, the method further includes: S7. An inclined support with a V-shaped cross-section, a cross support located above the inclined support, and an inner formwork lifting lug are arranged inside the inner formwork. S8. Use the inner formwork lifting lug to lift the inner formwork and the UHPC thin-walled shell out of the pit.

[0013] In a preferred embodiment, triangular notches with a triangular cross-section are provided at both corners of the bottom of the inner support and the inner formwork, which are used to enhance the connection strength between the side plate and the bottom plate after the UHPC thin-walled shell is formed.

[0014] The present invention provides a method for the stable construction of a UHPC thin-walled shell capping beam, which can fabricate a UHPC thin-walled shell of a capping beam. During on-site construction, only need to hoist the UHPC thin-walled shell onto the pier column, lay the corresponding steel bar skeleton and prestressed cable, and finally pour ordinary concrete. Compared with the traditional construction process, there is no need to erect temporary supports and formworks, effectively simplifying the construction process, shortening the construction time, reducing pollution and noise. At the same time, due to its light self-weight, there is no need to use a large number of hoisting tools and hoisting space, which can minimize the impact of construction on the road traffic under the bridge. By carrying out the compaction construction in the pit, the strength of the UHPC thin-walled shell after forming can be significantly improved through the compaction process, and it is also convenient for later curing work. In addition, through the combination of UHPC concrete and ordinary concrete, the cost of using UHPC concrete can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the drawings and embodiments: Figure 1It is a test diagram of the positional relationship among the pit, the lifting equipment and the inner formwork of the present invention; Figure 2 It is a schematic structural diagram before the inner formwork is rammed of the present invention; Figure 3 It is a schematic structural diagram after the inner formwork is rammed of the present invention; Figure 4 It is a schematic structural diagram of the outer formwork demoulding of the present invention; Figure 5 It is a schematic structural diagram of the inner support removal of the present invention; Figure 6 It is a schematic structural diagram of the UHPC thin-walled shell curing of the present invention; Figure 7 It is a schematic structural diagram of the UHPC thin-walled shell being lifted out of the pit of the present invention; Figure 8 It is a connection structure diagram of the inner support and the inner formwork of the present invention; Figure 9 It is a connection structure diagram of the extended support structure of the present invention; Figure 10 It is a connection structure diagram of the connection locking mechanism of the present invention; In the figure: pit 1; outer formwork 2; support frame 201; opening and closing plate 202; opening and closing oil cylinder 203; bottom outer formwork 204; side outer formwork 205; extended support structure 206; extended vertical plate 2061; connecting cross plate 2062; extended hinge seat 2063; lifting equipment 3; gantry walking trolley 301; movable cross beam 302; horizontal adjustment oil cylinder 303; hoisting sliding seat 304; ramming oil cylinder 305; electric hoist 306; connection locking mechanism 307; docking plug 3071; docking sleeve 3072; docking groove 3073; docking pin hole 3074; docking automatic bolt 3075; inner support 4; side support frame 401; wedge block 402; inner formwork 5; formwork 501; shear stud 502; diagonal brace 503; cross brace 504; UHPC concrete 6; inner formwork lifting lug 601; cover plate 7; installation limit clamp 8; vibrator 9. Specific implementation manner

[0016] As Figure 1-8 shown, a method for the stable construction of a UHPC thin-walled shell capping beam, the method comprising: S1. Excavate a pit 1 on the ground for forming the UHPC thin-walled shell.

[0017] S2. Set an outer formwork 2 in the pit 1, as Figure 2As shown, the outer formwork 2 is an openable and closable structure, specifically including a support frame 201 anchored in the pit 1. On both sides of the top of the support frame 201, opening and closing plates 202 are hingedly arranged. An extended support structure 206 is arranged on the outer side of the opening and closing plate 202. An opening and closing oil cylinder 203 is hingedly arranged on the outer side of the extended support structure 206. On the other side of the opening and closing oil cylinder 203, an anchor is hinged, and the anchor is anchored on the top wall of the side surface of the pit 1. A bottom outer form 204 and a side outer form 205 are respectively fixedly arranged on the top of the support frame 201 and the inner side of the opening and closing plate 202; As Figure 9 shown, the extended support structure 206 includes a plurality of extended vertical plates 2061 fixedly arranged on the outer side of the opening and closing plate 202, and a connecting cross plate 2062 fixedly connecting all the extended vertical plates 2061. An extended hinge seat 2063 hinged to the opening and closing oil cylinder 203 is arranged on the outer side of the top of the extended vertical plate 2061; In this step, the outer formwork 2 is in the closed form state, and a reinforcing rod is arranged between the opening and closing plate 202 and the side wall of the pit 1. S3. Pour UHPC concrete 6 into the outer formwork 2 according to the designed quantity. After the pouring is completed, use the installation vibrators 9 installed on both sides of the bottom of the outer formwork 2 to level the liquid surface of the UHPC concrete 6, and at the same time remove the vibrators 9 after the vibration is completed; In this embodiment, the components of the UHPC concrete 6 are 700 - 900 kg / cubic meter of 525 ordinary Portland cement, 50 - 200 kg / cubic meter of silica fume of grade 94, 30 - 100 kg / cubic meter of fly ash microspheres of 400 mesh, quartz sand of 20 - 40 mesh, 40 - 70 mesh, 70 - 120 mesh, in a mass ratio of 3:6:1850 - 1100 kg / cubic meter, 1 - 10 kg / cubic meter of a new type of composite expansive agent, 5 - 15 kg / cubic meter of a high-performance powder water reducer, 0.1 - 1.5 kg / cubic meter of a defoaming component, 0.1 - 0.5 kg / cubic meter of a viscosity-reducing component, 150 - 230 kg / cubic meter of copper-plated straight steel fibers of 13 mm, and 145 - 170 kg / cubic meter of water. Among them, the steam-cured compressive strength of the UHPC is between 170 - 220 MPa, and the flexural strength is between 30 - 38 MPa.

[0018] S4. Lift and install the assembled inner formwork 5 and inner support 4 directly above the outer formwork 2. As Figure 1 shown, the inner formwork 5 and inner support 4 are assembled on the ground outside the pit 1; The inner formwork 5 includes formwork 501 assembled on the bottom and two side surfaces of the inner support 4, and shear studs 502 arranged in an array on the formwork 501. The shear studs 502 can effectively improve the connection between the formwork 501 and the concrete; Moreover, the lifting of the inner formwork 5 and inner support 4 is completed by a lifting device 3. The lifting device 3 includes a gantry walking trolley 301 arranged on both sides of the pit 1 and a plurality of electric hoists 306 arranged on the gantry walking trolley 301; The inner support 4 includes two symmetrically arranged side support frames 401. The bottoms of the opposite sides of the two side support frames 401 are hinged, and a wedge block 402 is inserted at the top; A pressing mechanism for applying pressure to the inner formwork 5 and the inner support 4 is suspended on the electric hoist 306. The pressing mechanism includes two movable cross beams 302 slidably arranged between the columns of the gantry walking trolley 301. A lifting lug for connecting the electric hoist 306 is fixedly provided at the top of the upper movable cross beam 302. A pressing oil cylinder 305 and a connection locking mechanism 307 are arranged between the two movable cross beams 302. As Figure 10 shown, the connection locking mechanism 307 includes a docking sleeve rod 3072 and a docking plug rod 3071 respectively arranged on the opposite sides of the two movable cross beams 302. A docking groove 3073 for inserting the docking plug rod 3071 is provided at the end of the docking sleeve rod 3072, and docking pin holes 3074 are arranged on the docking ends of the docking plug rod 3071 and the docking sleeve rod 3072. A docking automatic plug 3075 corresponding to the docking pin hole 3074 is fixedly provided on the docking sleeve rod 3072. The two movable cross beams 302 can be connected into a whole through the connection locking mechanism 307. Thus, by the stretching of the electric hoist 306, the two movable cross beams 302 can slide up and down between the columns of the gantry walking trolley 301, so as to adjust the pressing height. At the same time, by releasing the connection locking mechanism 307, the two movable cross beams 302 can be separated, and the lower movable cross beam 302 is pressed down by the pressing oil cylinder 305 for die casting; A hoisting sliding seat 304 and a lateral adjustment oil cylinder 303 are arranged at the bottom of the lower movable cross beam 302. The hoisting sliding seat 304 is slidably connected with the movable cross beam 302. In this embodiment, a sliding rail structure for sliding is arranged between the movable cross beam 302 and the hoisting sliding seat 304. A rail locking device is arranged on the hoisting sliding seat 304. The output end of the lateral adjustment oil cylinder 303 is connected with the hoisting sliding seat 304. By the telescopic movement of the lateral adjustment oil cylinder 303, the hoisting sliding seat 304 can be pushed to slide horizontally on the movable cross beam 302, so as to accurately adjust the lateral position of pressing; Height locking mechanisms for fixing the posture are arranged between the two movable cross beams 302 and the columns of the gantry walking trolley 301 on the hoisting sliding seat. In this embodiment, sliding rails for the movable cross beam 302 to slide are arranged on the columns of the gantry walking trolley 301. The height locking mechanism is a rail locking device, preferably an automatic plug and pin hole structure; It should be noted that the above-mentioned sliding rail structure and rail locking device are both conventional technical means in the art, so they will not be described in detail here.

[0019] When the hoisting equipment 3 hoists the inner formwork 5 and the inner support 4, the connection locking mechanism 307 is in the locked state. The height locking mechanisms of the two movable crossbeams 302 are released, and the two movable crossbeams 302 are lowered to a preset height by using the electric hoist 306. Then, the height locking mechanism of the upper movable crossbeam 302 is locked, and the connection of the connection locking mechanism 307 is released. The lower movable crossbeam 302 is driven by the ramming oil cylinder 305 to drive the hoisting sliding seat 304 to the top of the inner formwork 5 and the inner support 4 and connect them. Then, the lower movable crossbeam 302 and the hoisting sliding seat 304 are lifted by using the ramming oil cylinder 305, and the connection locking mechanism 307 is connected. The two movable crossbeams 302 are lifted to a certain height by using the electric hoist 306, and the gantry walking trolley 301 walks above the outer formwork 2; In this embodiment, both of the two movable crossbeams 302 are slidably connected to the gantry walking trolley 301, which is convenient for the stability of the overall frame structure. At the same time, during ramming, the sliding of the movable crossbeam 302 on the column of the gantry walking trolley 301 can effectively enhance the lateral stability of the ramming oil cylinder 305.

[0020] In addition, in the preferred solution, a touch sensor is embedded in the inner top wall of the docking groove 3073. When the docking plug 3071 is inserted into it and touches the touch sensor, it is prompted that the plugging is in place, the contraction of the ramming oil cylinder 305 is stopped, and the docking automatic bolt 3075 is started to complete the bolting work.

[0021] S5. Apply a downward pressure to the inner formwork 5 and the inner support 4, and use the inner formwork 5 to ram the UHPC concrete 6, so that the liquid level of the UHPC concrete 6 rises between the inner formwork 5 and the outer formwork 2 until it is pressed down to the specified thickness; The specific method is as follows: S51. Anchor the gantry walking trolley 301 to the ground; S52. Start the electric hoist 306 to make the two movable crossbeams 302 slide down along the columns of the gantry walking trolley 301 to a specified height until the inner formwork 5 and the inner support 4 are located above the outer formwork 2, and lock the upper movable crossbeam 302 through the height locking mechanism; S53. Use the lateral adjustment oil cylinder 303 to accurately adjust the lateral position of the inner formwork 5. After the lateral position is adjusted, an anti - displacement card 8 is installed between the top ends of the inner formwork 5 and the outer formwork 2. The anti - displacement card 8 is in an inverted U - shape and is fixedly arranged on the inner formwork 5 and can descend with the inner formwork 5, so as to perform lateral limit on the ramming inner formwork 5 and avoid unnecessary movement during ramming; S54. Release the connection locking mechanism 307 between the two movable crossbeams 302, start the ramming oil cylinder 305 to make the lower movable crossbeam 302 drive the hoisting sliding seat 304 to descend, so as to ram the UHPC concrete 6 by using the downward pressure of the inner formwork 5 and the inner support 4 until it stops after being pressed down to the designed thickness; S55. Lock the lower movable crossbeam 302 through the height locking mechanism to prevent it from floating up, and relieve the pressure of the compaction oil cylinder 305.

[0022] S6. After the UHPC concrete 6 reaches the demoulding strength, carry out demoulding and curing to form the UHPC thin-walled shell; The demoulding process includes the demoulding of the outer formwork 2 and the removal of the inner support 4. Among them, when the outer formwork 2 is demoulded, the reinforcement rods are removed, and the opening and closing oil cylinder 203 is contracted, so that the opening and closing plate 202 and the side outer form 205 are rotated along the bottom hinge point for demoulding; The method for removing the inner support 4 is as follows: Disconnect the connection between the inner support 4 and the inner formwork 5, and remove the wedge-shaped block 402 on the inner support 4, so that the middle part of the inner support 4 is relieved of force and rotates inward along the hinge point to close, so that the side support frames 401 on both sides are gradually separated from the inner formwork 5. Then connect the hoisting sliding seat 304 to the inner support 4 through the I-beam and bolts, contract the compaction oil cylinder 305, lift the inner support 4, and finally release the anchoring of the gantry walking trolley 301, and transport the inner support 4 away. The hoisting method of the inner support 4 in this method is the same as the hoisting method in step S4; The above-mentioned demoulding angle is 3° - 10°.

[0023] In addition, the curing method is as follows: After the demoulding process is completed, inject high-temperature water into the pit 1, arrange heating equipment in the pit 1, and finally cover the pit 1 with a cover plate 7 for sealing. The temperature of the high-temperature water is 85 - 90°, and the curing time is two days.

[0024] Since the opening and closing oil cylinder 203 is hinged to the top of the pit 1 through the extension support structure 206, it is avoided to be immersed in water during curing, which affects the service performance of the opening and closing oil cylinder 203. The cover plate 7 covers the pit 1 to avoid the opening and closing oil cylinder 203.

[0025] S7. Fix an inclined support 503 with a V-shaped cross-section, a cross support 504 located above the inclined support 503, and an inner formwork lifting lug 601 inside the inner formwork 5; S8. Use the inner formwork lifting lug 601 to lift the inner formwork 5 and the UHPC thin-walled shell out of the pit 1. When hoisting the inner formwork lifting lug 601, the lifting equipment 3 uses the inner formwork lifting tool to lift the UHPC thin-walled shell; The removed UHPC thin-walled shell can be moved to the ground storage area for storage or installed at the capping beam construction site.

[0026] In the preferred solution, triangular notches 402 are provided at both corners of the bottom of the inner support 4 and the inner formwork 5. When the inner support 4 with the notches 402 and the inner formwork 5 are compacted, triangular connecting structures can be formed at the two inner corners of the UHPC thin-walled shell, thereby effectively enhancing the connection strength between the side plate and the bottom plate after the UHPC thin-walled shell is formed.

[0027] During on-site construction of the UHPC thin-walled shell in this embodiment, it is only necessary to hoist the UHPC thin-walled shell onto the pier column, arrange the corresponding steel bar skeletons and prestressing cables, and finally pour ordinary concrete. Compared with the traditional construction process, there is no need to erect temporary supports and formworks, which effectively simplifies the construction process, shortens the construction time, reduces pollution and noise. At the same time, due to its light self-weight, there is no need to use a large number of hoisting tools and hoisting space, which can minimize the impact of construction on the road traffic under the bridge. At the same time, leaving the internal formwork 5, the inclined strut 503 and the cross strut 504 inside the UHPC thin-walled shell can effectively enhance the supporting force during hoisting. At the same time, during on-site construction, while ensuring the strength, the amount of steel bars can be reduced, further reducing the self-cost of the capping beam. The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. Method for stable construction of UHPC thin-walled outer casing bent cap, characterized in that: The method includes: S1. Excavate a pit (1) on the ground for forming a UHPC thin-walled shell; S2. Set an outer formwork (2) in the pit (1); S3. Pour UHPC concrete (6) into the outer formwork (2) according to the designed quantity; S4. Hoist the assembled inner formwork (5) and inner support (4) directly above the outer formwork (2); S5. Apply a downward pressure to the inner formwork (5) and inner support (4), and use the inner formwork (5) to compact the UHPC concrete (6), so that the liquid level of the UHPC concrete (6) rises between the inner formwork (5) and the outer formwork (2) until it is pressed down to the specified thickness; S6. After the UHPC concrete (6) reaches the demoulding strength, carry out demoulding and curing to form a UHPC thin-walled shell.

2. The method for stable construction of the UHPC thin-walled outer casing capping beam according to claim 1, wherein: The outer formwork (2) is a structure that can be opened and closed, and specifically includes a support frame (201) anchored in the pit (1). On both sides of the top of the support frame (201), opening and closing plates (202) are hingedly arranged. An extension support structure (206) is arranged on the outer side of the opening and closing plate (202). An opening and closing oil cylinder (203) is hingedly arranged on the outer side of the extension support structure (206). On the other side of the opening and closing oil cylinder (203), an anchor is hinged, and the anchor is anchored on the top wall of the side of the pit (1). A bottom outer mold (204) and a side outer mold (205) are fixedly arranged on the top of the support frame (201) and the inner side of the opening and closing plate (202) respectively; The extension support structure (206) includes a plurality of extension vertical plates (2061) arranged on the outer side of the opening and closing plate (202), and a connecting cross plate (2062) connecting all the extension vertical plates (2061). An extension hinge seat (2063) hinged to the opening and closing oil cylinder (203) is arranged on the outer side of the top of the extension vertical plate (2061); In step S2, the outer formwork (2) is in a closed mold state, and a reinforcing rod is arranged between the opening and closing plate (202) and the side wall of the pit (1).

3. The method for the stable construction of the UHPC thin-walled outer casing capping beam according to claim 1, characterized in that: In step S3, after the pouring of the UHPC concrete (6) is completed, it is also necessary to vibrate it. The specific method is: install vibrators (9) on both sides of the bottom of the outer formwork (2), and use the vibrators (9) to level the liquid level of the UHPC concrete (6).

4. The method for the stable construction of the UHPC thin-walled outer casing capping beam according to claim 2, characterized in that: The inner formwork (5) in step S4 includes templates (501) assembled on the bottom and two sides of the inner support (4), and shear studs (502) arranged in an array on the templates (501). The hoisting of the inner formwork (5) and the inner support (4) is completed by a lifting device (3). The lifting device (3) includes a gantry walking trolley (301) arranged on both sides of the pit (1) and a plurality of electric hoists (306) arranged on the gantry walking trolley (301); In step S4, a ramming mechanism for applying pressure to the inner formwork (5) and the inner support (4) is suspended on the electric hoist (306). The ramming mechanism includes two movable crossbeams (302) slidably arranged between the columns of the gantry walking trolley (301). A lifting lug for connecting the electric hoist (306) is arranged at the top of the upper movable crossbeam (302). A ramming oil cylinder (305) and a connection locking mechanism (307) are arranged between the two movable crossbeams (302). A hoisting sliding seat (304) and a lateral adjustment oil cylinder (303) are arranged at the bottom of the lower movable crossbeam (302). The hoisting sliding seat (304) is slidably connected to the movable crossbeam (302), and the output end of the lateral adjustment oil cylinder (303) is connected to the hoisting sliding seat (304). Height locking mechanisms for fixing the attitude are arranged between the two movable crossbeams (302) and the columns of the gantry walking trolley (301) for the hoisting sliding seat; The connection locking mechanism (307) includes a docking sleeve rod (3072) and a docking plug rod (3071) respectively arranged on the opposite sides of the two movable crossbeams (302). A docking groove (3073) for inserting the docking plug rod (3071) is arranged at the end of the docking sleeve rod (3072), and docking pin holes (3074) are arranged on the docking ends of the docking plug rod (3071) and the docking sleeve rod (3072). A docking automatic plug pin (3075) corresponding to the docking pin hole (3074) is arranged on the outer side of the docking sleeve rod (3072); When the hoisting equipment (3) hoists the inner formwork (5) and the inner support (4), the connection locking mechanism (307) is in a locked state. The height locking mechanisms of the two movable crossbeams (302) are released, and the two movable crossbeams (302) are lowered to a preset height by using the electric hoist (306). Then, the height locking mechanism of the upper movable crossbeam (302) is locked, and the connection of the connection locking mechanism (307) is released. The lower movable crossbeam (302) is driven by the ramming oil cylinder (305) to bring the hoisting sliding seat (304) to the top of the inner formwork (5) and the inner support (4) and connected. Then, the lower movable crossbeam (302) and the hoisting sliding seat (304) are lifted by using the ramming oil cylinder (305), and the connection locking mechanism (307) is connected. The two movable crossbeams (302) are lifted to a certain height by using the electric hoist (306), and the gantry walking trolley (301) travels above the outer formwork (2).

5. The method for stable construction of the UHPC thin-walled outer casing bent cap according to claim 4, characterized in that: The specific method of ramming in step S5 is as follows: S51. Anchor the gantry walking trolley (301) to the ground; S52. Start the electric hoist (306) to make the two movable crossbeams (302) slide down along the columns of the gantry walking trolley (301) to a specified height until the inner formwork (5) and the inner support (4) are located above the outer formwork (2), and lock the upper movable crossbeam (302) through the height locking mechanism; S53. Precisely adjust the lateral position of the inner formwork (5) by using the lateral adjustment oil cylinder (303); S54. Release the connection locking mechanism (307) between the two movable crossbeams (302), start the compaction cylinder (305), and lower the lower movable crossbeam (302) with the hoisting sliding seat (304), so as to compact the UHPC concrete (6) by pressing down with the inner formwork (5) and the inner support (4) until it stops after pressing down to the designed thickness; S55. Lock the lower movable crossbeam (302) through the height locking mechanism to prevent floating, and relieve the pressure of the compaction cylinder (305).

6. The method for the stable construction of the UHPC thin-walled outer casing capping beam according to claim 5, characterized in that: After the lateral position of the inner formwork (5) in step S53 is adjusted, install a limit card (8) between the top ends of the inner formwork (5) and the outer formwork (2). The installed limit card (8) is in an inverted U shape and is fixed on the inner formwork (5) and can descend with the inner formwork (5).

7. The method for stable construction of the UHPC thin-walled outer casing capping beam according to claim 5, characterized in that: The inner support (4) includes two symmetrically arranged side support frames (401). The bottoms of the opposite sides of the two side support frames (401) are hinged, and a wedge block (402) is inserted at the top; The demoulding process in step S6 includes the demoulding of the outer formwork (2) and the removal of the inner support (4). Among them, when the outer formwork (2) is demoulded, remove the reinforcing rod and contract the opening and closing cylinder (203) to make the opening and closing plate (202) and the side outer formwork (205) rotate and demould along the bottom hinge point; The method for removing the inner support (4) is as follows: release the connection between the inner support (4) and the inner formwork (5), remove the wedge block (402) on the inner support (4), make the middle part of the inner support (4) relieve force and rotate inward along the hinge point to close, so that the two side support frames (401) gradually separate from the inner formwork (5), then connect the separated inner support (4) with the hoisting sliding seat (304), contract the compaction cylinder (305) to lift the inner support (4), and finally release the anchoring of the gantry trolley (301) and transport the inner support (4) away.

8. The method for the stable construction of the UHPC thin-walled outer casing capping beam according to claim 7, characterized in that: step S6 The specific curing method is as follows: after the demoulding process is completed, inject high-temperature water into the pit (1), arrange heating equipment in the pit (1), and finally cover the pit (1) with a cover plate (7) for sealing.

9. The method for stable construction of UHPC thin-walled outer casing capping beams according to claim 7, characterized in that: This method also includes: S7. Install a diagonal brace (503) with a V-shaped cross-section, a cross brace (504) located above the diagonal brace (503), and an inner formwork lifting lug (601) inside the inner formwork (5); S8. Use the inner formwork lifting lug (601) to lift the inner formwork (5) and the UHPC thin-walled shell out of the pit (1).

10. The method for stable construction of the UHPC thin-walled outer casing capping beam according to claim 7, characterized in that: At both corners of the bottom of the inner support (4) and the inner formwork (5), there are notches (402) with a triangular cross-section, which are used to enhance the connection strength between the side plate and the bottom plate after the UHPC thin-walled shell is formed.

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