A steel formwork for a long and large precast box girder

Abstract

The application discloses a steel formwork with partially detachable end part of prefabricated long and large box girder, belongs to the technical field of prefabricated concrete beam production, and has a downward detaching mechanism for the bottom die strip in the range of width D close to the end part along the direction of the bridge, and has an outward detaching mechanism for the side die block in the range of height H close to the bottom along the vertical direction, and the surface of the bottom die strip and the side die block after being detached can form a height difference with the surface of the outer formwork, the height difference being h. The use method is as follows: after the concrete is poured and completed, the end part of the outer formwork is subjected to a preset detaching behavior before the prestressed steel strand is tensioned, so that the contact surface provided by the outer formwork can effectively adapt to the upward deflection of the beam body after the prestressed steel strand is tensioned, and thus the phenomenon that the stress is concentrated at the end part of the beam body and the friction effect is remarkable is effectively improved, and the problem that cracks are generated at the edge of the end part of the bottom plate during the prefabrication of the long and large box girder is fundamentally solved.

Description

Technical Field

[0001] This invention belongs to the field of precast concrete beam production technology, specifically relating to a steel template for precast long box beams whose ends can be partially detached. Background Technology

[0002] With the promotion and popularization of advanced construction concepts such as standardization and factory production, the construction of high-speed railway bridges has entered a new stage. The superstructure has gradually transitioned from the more common 32m beam type to the 40m beam type. As the beam length and weight increase, precast beams have encountered certain quality problems during construction and production, among which the problem of cracks appearing on the edge of the bottom plate at the end of the 40m box girder is particularly prominent.

[0003] The root cause of the above quality problems is: such as Figure 9 After the concrete of the beam was poured and the prestressed steel strands were tensioned, the beam deflected upward (arched back), resulting in significant stress concentration and prominent friction effect at the edge of the end plate. Tensile stress exceeding its own tensile strength appeared, causing the concrete in the relevant area to crack. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a steel template that can be partially removed from the end of a precast long box girder, thereby improving the phenomenon of stress concentration and significant friction effect at the end of the girder.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention includes an outer formwork supporting the outer side of the bottom surface of a box girder. The outer formwork has a cut-out groove opened inward along the bottom edge of the bridge direction. The cut-out groove is provided with a bottom formwork strip for vertically unloading downward force and a side module for unloading force to both sides. After the concrete is poured and before the prestressed steel strands are tensioned, the bottom formwork strip and the side module are moved so that the bottom edges at both ends of the box girder are unloaded.

[0007] Furthermore, the bottom mold strip and the side module are provided with several limiting baffles on the outer edge of the outer template, so that the inner side of the bottom mold strip and the side module is flush with the inner side of the outer template.

[0008] Furthermore, a number of bottom mold back ribs are fixed on the outer side of the bottom mold strip, and a number of side mold pads are fixed on the outer side of the side mold. A stress-relieving support part is provided at the cut-out position of the outer mold template, and the stress-relieving support part abuts against the bottom mold back ribs and the side mold pads respectively.

[0009] Furthermore, the stress relief support includes two parallel support plates. One end of each support plate is fixed to the outside of the outer template, and the other end is suspended outside the cut groove. Several fastening nuts are fixed between the two support plates. Fastening screws are threaded onto the fastening nuts, and the fastening screws abut against the side mold pad and the bottom mold back rib, respectively.

[0010] Furthermore, the stress-relieving support includes a support bar distributed along the outer side of the bottom mold strip and the side module. Both ends of the support bar are fixed to the ends of the cut grooves of the outer mold template via connectors. Two long sliding rods and two short sliding rods are slidably arranged within the support bar. The two long sliding rods are located outside the bottom mold strip, and the two short sliding rods are located outside the side module. Each of the long and short sliding rods has several inclined grooves on the side facing the outer mold template. The support bar is vertically slidable on the side facing the outer mold template. There are several abutments, the bottom of which abuts against the inclined groove, and the top of which abuts against the side mold pad and the bottom mold back rib respectively; a trapezoidal block is vertically slidably disposed between the two long sliding rods, and the two long sliding rods abut against the two inclined sides of the trapezoidal block; the support bar is also threadedly connected to a stress relief stud, one end of which abuts against the bottom of the trapezoidal block, and the other end extends out from the outside of the support bar; a bent oil passage is connected between the long sliding rods and the short sliding rods, and the oil passage is filled with hydraulic oil.

[0011] Furthermore, the oil passage has straight sections at both ends, and the ends of the long slide rod and the short slide rod are provided with piston heads, which are slidably disposed within the straight sections.

[0012] Furthermore, a horizontal slide rail is fixed to the outside of the support bar, and a moving carriage is slidably mounted on the slide rail. The moving carriage is equipped with a guide rail perpendicular to the end face of the cast box girder, and a processing carriage is slidably mounted on the guide rail. A grinding roller is rotatably mounted on the processing carriage. The axis of the grinding roller is perpendicular to the end face of the cast box girder, and the upper side of the grinding roller is tangent to the bottom side of the cast box girder.

[0013] The beneficial effects of this invention are as follows:

[0014] The bottom formwork strips, within a width D near the end along the bridge direction, have a downward unloading mechanism, while the side formwork strips, within a height H near the bottom in the vertical direction, have an outward unloading mechanism. After unloading, the surfaces of the bottom formwork strips and side formwork strips can form a height difference of h with the surface of the outer formwork. The method of application is as follows: After the concrete is poured but before the prestressed steel strands are tensioned, the ends of the outer formwork undergo a pre-set unloading behavior. This allows the contact surface provided to adapt in advance to the upward deflection of the beam after the prestressed steel strands are tensioned, effectively improving the phenomenon of stress concentration and significant friction effect at the bottom edge of the beam end, fundamentally solving the problem of cracks at the bottom edge of the long box girder during prefabrication.

[0015] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0016] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0017] Figure 1 This is a schematic diagram of the outer template structure in Embodiment 1 of the present invention;

[0018] Figure 2 This is a schematic diagram of the stress-relieving support structure according to Embodiment 1 of the present invention;

[0019] Figure 3 This is a schematic diagram of the outer template unloading in Embodiment 1 of the present invention;

[0020] Figure 4 This is a schematic diagram of the outer template structure in Embodiment 2 of the present invention;

[0021] Figure 5 for Figure 4 Enlarged view of point A;

[0022] Figure 6 This is a cross-sectional view of the stress-relieving support part in Embodiment 2 of the present invention;

[0023] Figure 7 for Figure 6 Enlarged view of point B;

[0024] Figure 8 for Figure 6 Enlarged view of point C;

[0025] Figure 9 This is a schematic diagram of the upward deflection of a precast beam after tensioning.

[0026] The following are marked in the attached diagram: 1. Outer template; 2. Cut groove; 3. Bottom mold strip; 31. Bottom mold back rib; 4. Side module; 41. Side mold pad; 5. Limiting baffle; 6. Unloading support part; 611. Support plate; 612. Fastening nut; 613. Fastening screw; 621. Support bar; 622. Long slide bar; 623. Short slide bar; 624. Inclined groove; 625. Abutment; 626. Trapezoidal block; 627. Unloading stud; 628. Oil passage; 629. Piston head; 71. Slide rail; 72. Moving carriage; 73. Guide rail; 74. Processing carriage; 75. Grinding roller. Detailed Implementation

[0027] like Figures 1-8As shown, this invention discloses a steel template for the end of a precast long box girder that can be partially detached. The steel template for the box girder consists of an outer template 1, an inner template, and an end template, forming a sealed box girder casting structure. This is prior art and will not be described in detail here.

[0028] Example 1

[0029] like Figure 1 , Figure 2 and Figure 3 As shown, the outer template 1 has a short groove 2 cut inward from its bottom edge along the bridge direction. The depth D of the groove 2 is 5-20cm, and the height H of the groove 2 is 25-50cm. A bottom formwork strip 3 for downward vertical stress relief and a side module 4 for stress relief to both sides are provided at the location of the groove 2. The bottom formwork strip 3 and the side module 4 cover the groove 2, thus closing the outer template 1. (Refer to...) Figure 3 After the concrete is poured and before the prestressed steel strands are tensioned, the bottom formwork strip 3 and the side module 4 can be moved to unload the stress at the bottom edges of both ends of the box girder. The unloading height h of the bottom formwork strip 3 and the side module 4 can be 1 to 20 mm. The bottom formwork strip 3 and the side module 4 that produce the unloading behavior have a reset mechanism and can be restored to the position before unloading. The bearing capacity is not reduced because of the unloading mechanism.

[0030] In further proposals, such as Figure 2 As shown, the bottom mold strip 3 and the side module 4 are respectively provided with several limiting baffles 5 on the outer edge of the outer template 1, so that the inner side of the bottom mold strip 3 and the side module 4 is flush with the inner side of the outer template 1. This structure can also effectively prevent the bottom mold strip 3 from going up beyond the surface of the outer template 1 and prevent the side module 4 from going up beyond the surface of the outer template 1 from the outside to the inside.

[0031] In further proposals, such as Figure 2 As shown, two parallel bottom mold back ribs 31 are fixed on the outer side of the bottom mold strip 3. The bottom mold back ribs 31 can be I-beams, channel steel, or other steel members that meet the stress requirements. Two side mold pads 41 are fixed on the outer side of the side mold module 4. The distance between the side mold pads 41 is the same as the distance between the bottom mold back ribs 31. A stress-relieving support part 6 is provided at the cut groove 2 position of the outer mold template 1. The stress-relieving support part 6 includes two parallel support plates 611. One end of the support plate 611 is fixed to the outer side of the outer mold template 1, and the other end is suspended outside the cut groove 2. Several fastening nuts 612 are fixed between the two support plates 611. Fastening screws 613 are threadedly connected to the fastening nuts 612. The fastening screws 613 abut against the side mold pads 41 and the bottom mold back ribs 31 respectively.

[0032] In this embodiment, the bottom formwork strip 3 with a width of D near the end along the bridge direction has a downward unloading mechanism, and the side module 4 with a height of H near the bottom along the vertical direction has an outward unloading mechanism. After unloading, the surfaces of the bottom formwork strip 3 and the side module 4 can form a height difference of h with respect to the surface of the outer template 1. The method of use is as follows: After the concrete is poured and before the prestressed steel tendons are tensioned, the end of the outer formwork 1 undergoes a pre-set unloading behavior, so that the contact surface it provides can adapt to the upward deflection of the beam after the prestressed steel tendons are tensioned in advance. This effectively improves the phenomenon of stress concentration and significant friction effect at the edge of the bottom plate at the end of the beam, and fundamentally solves the problem of cracking at the edge of the bottom plate during the prefabrication of long box girders. The working principle of this embodiment is clear, and the regional module division is reasonable. It can effectively change the support mode of the formwork in different processes such as concrete pouring and prestressed tendon tensioning of the precast beam, so that the stress state of the beam is more reasonable and avoids crack quality problems. This technical solution is a clever modification of the traditional formwork solution, achieving good social benefits while requiring low economic costs. Moreover, this structure is simple to operate and convenient to construct. The construction of fastening nuts 612 and fastening screws 613 enables the recycling of all formwork tools, which is in line with the concept of safe, green and sustainable development.

[0033] Example 2

[0034] like Figures 4-8 As shown, further improvements are made based on Example 1:

[0035] The structure of the load-bearing unit is as follows Figure 6 and Figure 7As shown, the stress-relieving support part 6 includes a support bar 621 distributed along the outer side of the bottom mold strip 3 and the side module 4. The support bar 621 is horizontal in the middle and curved upward at both ends. The two ends of the support bar 621 are fixed to the two ends of the cut groove 2 of the outer mold 1 by connectors. Two long slide rods 622 and two short slide rods 623 are slidably arranged inside the support bar 621. The two long slide rods 622 are located outside the bottom mold strip 3, and the two short slide rods 623 are located outside the side module 4. The long slide rods 622 and the short slide rods 623 are provided with several inclined grooves 624 on the side facing the outer mold 1. Several abutment posts 625 are slidably arranged vertically on the side of the support bar 621 facing the outer mold 1. The bottom end of the abutment post 625 abuts against the inclined groove 624. The top ends of the abutment 625 abut against the side mold pad 41 and the bottom mold back rib 31 respectively; a trapezoidal block 626 is vertically slidably disposed between the two long slide rods 622, and the two long slide rods 622 abut against the two inclined sides of the trapezoidal block 626; a stress relief stud 627 is also threadedly connected to the support bar 621, one end of the stress relief stud 627 abuts against the bottom of the trapezoidal block 626, and the other end extends out from the outside of the support bar 621; a bent oil passage 628 is connected between the long slide rods 622 and the short slide rods 623, and the two ends of the oil passage 628 are straight sections; piston heads 629 are provided at the ends of the long slide rods 622 and the short slide rods 623, and the piston heads 629 are slidably disposed in the straight sections; the oil passage 628 is filled with hydraulic oil.

[0036] In this structure, under the pressure of the box girder ends, several supporting bottom formwork strips 3 and side modules 4 are simultaneously pressed down, causing the supporting columns 625 to move downwards and outwards, and along the inclined groove 624. Under the contact of the supporting columns 625, the short slide rods 623 and long slide rods 622 simultaneously undergo the same displacement. By setting up oil passages 628, which are filled with hydraulic oil, the short slide rods 623 are supported by hydraulic oil during displacement. Both the short slide rods 623 and long slide rods 622 are supported by trapezoidal blocks 626. By rotating the unloading stud 627, the unloading stud 627 moves downwards, and the trapezoidal block 626 moves downwards. Block 626 moves downward, and short slide bar 623 and long slide bar 622 make the same displacement to allow several abutment columns 625 to move in the same displacement. This structure is an improvement on the unloading support part 6. The unloading support part 6 is controlled by an unloading stud 627. By rotating the unloading stud 627, the unloading distance of the bottom formwork strip 3 and the side module 4 can be adjusted at the same time, and the simultaneous translation of the bottom formwork strip 3 and the side module 4 can be ensured, so that the bottom formwork strip 3 and the side module 4 can always provide full-range support for the bottom edge of the box girder, avoiding damage caused by the concentration of support points and inaccurate distance adjustment during the upward deflection of the bottom edge of the box girder.

[0037] In further proposals, such as Figure 5As shown, a horizontal slide rail 71 is also fixed on the outer side of the support bar 621. A moving carriage 72 is slidably mounted on the slide rail 71. A guide rail 73 perpendicular to the end face of the cast box girder is mounted on the moving carriage 72. A processing carriage 74 is slidably mounted on the guide rail 73. A grinding roller 75 is rotatably mounted on the processing carriage 74. The axis of the grinding roller 75 is perpendicular to the end face of the cast box girder, and the upper side of the grinding roller 75 is tangent to the bottom side of the cast box girder.

[0038] By setting up the grinding roller 75, the slight upward deflection of the box girder is ground down. After the concrete has solidified, when the formwork is dismantled, the bottom formwork strip 3 and the side formwork 4 are completely removed. At this time, the grinding roller 75 moves to the bottom of the box girder with the processing carriage 74. The processing carriage 74 moves along the slide rail 71 with the moving carriage 72. The grinding roller 75 grinds the bottom surface of the box girder end and the nearby clearance protrusion, so that the bottom surface of the box girder end is level again. This structure helps to ensure the flatness of the overall bottom surface of the box girder, providing a level bottom surface for subsequent construction and installation of the box girder, and avoiding uneven support force caused by the downward protrusion of the box girder end when the box girder is placed on a plane.

[0039] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A steel formwork for partially detachable ends of a precast long box girder, characterized in that: The outer formwork (1) supports the bottom surface of the box girder. The outer formwork (1) has a cut-out groove (2) at the bottom edge along the bridge direction. The cut-out groove (2) is provided with a bottom formwork strip (3) for vertical unloading downwards and a side module (4) for unloading to both sides. After the concrete is poured, before the prestressed steel strands are tensioned, the bottom formwork strip (3) and the side module (4) are moved to unload the force at the bottom edge of both ends of the beam. The bottom formwork strip (3) and the side module (4) are provided with several limiting baffles (5) on the outer side of the outer formwork (1) so that the inner side of the bottom formwork strip (3) and the side module (4) is flush with the inner side of the outer formwork (1). Flat; several bottom mold back ribs (31) are fixed on the outer side of the bottom mold strip (3), several side mold pads (41) are fixed on the outer side of the side module (4), and a stress relief support part (6) is provided at the cut groove (2) position of the outer template (1), the stress relief support part (6) abuts against the bottom mold back ribs (31) and the side mold pads (41) respectively; the stress relief support part (6) includes a support strip (621) distributed along the outer side of the bottom mold strip (3) and the side module (4), the two ends of the support strip (621) are fixed to the two ends of the cut groove (2) of the outer template (1) by connectors; the support strip (621) 21) Two long sliding rods (622) and two short sliding rods (623) are provided for sliding inside. The two long sliding rods (622) are located outside the bottom mold strip (3), and the two short sliding rods (623) are located outside the side module (4). The long sliding rods (622) and the short sliding rods (623) are provided with several inclined grooves (624) on the side facing the outer mold template (1). The support strip (621) is provided with several abutments (625) that slide vertically on the side facing the outer mold template (1). The bottom end of the abutment (625) abuts against the inclined groove (624), and the top end of the abutment (625) abuts against the side. On the mold pad block (41) and the bottom mold back rib (31); a trapezoidal block (626) is vertically slidably disposed between the two long sliding rods (622), the two long sliding rods (622) abut against the two inclined sides of the trapezoidal block (626), the support bar (621) is also threadedly connected to a stress relief stud (627), one end of the stress relief stud (627) abuts against the bottom of the trapezoidal block (626), and the other end extends out from the outside of the support bar (621), a bent oil passage (628) is connected between the long sliding rod (622) and the short sliding rod (623), and the oil passage (628) is filled with hydraulic oil.

2. The steel formwork for partially detachable ends of the precast long box girder according to claim 1, characterized in that: The oil passage (628) has straight sections at both ends, and piston heads (629) are provided at the ends of the long slide rod (622) and the short slide rod (623). The piston heads (629) are slidably disposed in the straight sections.

3. The steel formwork for partially detachable ends of the precast long box girder according to claim 2, characterized in that: A horizontal slide rail (71) is fixed on the outside of the support bar (621). A moving carriage (72) is slidably mounted on the slide rail (71). A guide rail (73) perpendicular to the end face of the cast box girder is mounted on the moving carriage (72). A processing carriage (74) is slidably mounted on the guide rail (73). A grinding roller (75) is rotatably mounted on the processing carriage (74). The axis of the grinding roller (75) is perpendicular to the end face of the cast box girder, and the upper side of the grinding roller (75) is tangent to the bottom side of the cast box girder.

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