Construction device of pre-tensioning method small box girder and manufacturing method of small box girder

Abstract

The invention discloses a pre-tensioning method small box girder construction device and a small box girder manufacturing method.The small box girder is a pre-tensioning method tensioning zigzag-form steel strand concrete structure prefabricated small box girder and comprises a top plate, a web plate, a bottom plate, a middle partition plate, an end partition plate and a small box girder bottom die; the small box girder bottom die is arranged on the pedestal; the pedestal is provided with an in-beam steering device at a position corresponding to an in-beam conversion point ZN of the zigzag-form steel strand, and is provided with a beam end steering device at a position corresponding to an out-beam conversion point ZW; anchoring beams and tensioning devices are symmetrically arranged on the outer sides of the two beam end steering devices in sequence. When the small box girder is manufactured, steel bars, irrelevant to tensioning of the zigzag-form steel strands, of the small box girder and the zigzag-form steel strands are arranged firstly, then the zigzag-form steel strands are tensioned, the remaining steel bars are arranged, finally concrete is poured, the exposed zigzag-form steel strands are cut off after maintenance reaches a preset age, and corrosion prevention of the ends of the steel strands is conducted. The method solves the problem that the space state is complex when the zigzag-form steel strands are tensioned through a pre-tensioning method in the small prefabricated box girder.

Description

Technical Field

[0001] The invention relates to the technical field of pre-tensioned box girder construction, in particular to a construction device for a pre-tensioned small box girder and a method for manufacturing the small box girder. Background Art

[0002] In the prior art, the main type of bridge components using the pre-tensioning method is the main beam.

[0003] In the pre-tensioned main beam, the cross-section forms include box-shaped, I-shaped, T-shaped, etc. The webs of the pre-tensioned main beam are mostly arranged vertically, and the steel strands in the webs and bottom plates are arranged in a straight line or a broken line. For example, in the pre-tensioned hollow slab beam, the steel strands are arranged along the bottom plate in a straight line; in the pre-tensioned T-beam, the steel strands are arranged along the web, which can be all arranged in a straight line or a broken line.

[0004] The most commonly used prefabricated beams in urban viaducts are small box beams, mainly because they can cover a larger span range (20-40m) and have a more beautiful external effect (few beams, inclined webs). Hollow slabs and T beams are less used because the use of hollow slab beams is limited by span (≤20m) and T beams are limited by appearance (small amount used in urban bridges). However, hollow slab beams and T beams have better economic efficiency than small box beams, especially pre-tensioned T beams with the same span coverage as small box beams, whose economic advantages are more obvious. If the pre-tensioning method can be used for the construction of prefabricated small box beams, its economy and competitiveness can be significantly improved. Therefore, it is necessary to study the pre-tensioning method of small box beams.

[0005] Although many projects have adopted the zigzag pre-stressed T-beam, and from the perspective of technical feasibility, the zigzag pre-stressed small box girder is technically feasible.

[0006] However, all existing prefabricated small box girders use post-tensioning to tension prestressed steel strands, and there are almost no pre-tensioning small box girders in engineering applications. The main reason is that the span of a small box girder is usually more than 25m, and the steel strands need to be arranged in a broken line to achieve its economy. However, due to the inclination of the web of the small box girder, the bent steel strands have a complex spatial state, which puts high requirements on the design of the tensioning equipment, the prefabricated pedestal and the on-site construction, and it is difficult to promote it in general engineering projects.

[0007] Therefore, how to solve the problem of complex spatial state of prefabricated small box girders using the pre-tensioning method to tension the folded steel strands, and reduce the difficulty of designing tensioning equipment, prefabricating pedestals and on-site construction has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0008] In view of the above-mentioned defects of the prior art, the present invention provides a construction device and a method for manufacturing a small box girder by a pre-tensioning method, the purpose of which is to solve the problem of the complex spatial state of the prefabricated small box girder using the pre-tensioning method to tension the folded steel strands, and to reduce the difficulty of designing the tensioning equipment, prefabricating the pedestal and on-site construction.

[0009] To achieve the above purpose, the present invention discloses a construction device for a pre-tensioned small box girder, which is a prefabricated box girder of a concrete structure using pre-tensioned folded steel strands, and includes a top plate, a web plate, a bottom plate, a middle partition plate and end plates.

[0010] The construction device includes a small box beam bottom formwork;

[0011] The bottom mold of the small box beam is arranged on a pedestal;

[0012] The pedestal is provided with an inner-beam steering device at a position corresponding to the inner-beam conversion point ZN of the folded steel strand, and a beam end steering device at a position corresponding to the outer-beam conversion point ZW;

[0013] Anchor beams and tensioning devices are symmetrically arranged on the outsides of the two beam end steering devices;

[0014] Each of the inner-beam steering devices is provided with steering teeth capable of pulling the folded steel strands downwards, and a ground groove as a downward pulling space, corresponding to each of the webs;

[0015] Each of the ground grooves is a local concave structure arranged on the pedestal corresponding to the conversion point ZN in the beam;

[0016] Each of the steering teeth includes a plurality of downward hook-shaped structures corresponding to all of the folded steel strands in the corresponding web;

[0017] All the steering teeth of the steering device in the same beam are connected to the conversion beam through upper pull rods respectively;

[0018] Each of the upper pull rods is arranged parallel to the corresponding web, the lower end is connected to the corresponding conversion beam in a revolving pair, the upper end is embedded in the corresponding web and fixed to the corresponding steering gear;

[0019] Each of the transfer beams is arranged in parallel with the small box beam, and pulls all the upper pull rods and the corresponding steering gears downwards through the lower pull rods and corresponding anchors fixed between the ground trough embedded parts in the ground trough;

[0020] Each of the beam end steering devices comprises a plurality of steering wheels which are arranged corresponding to each of the folded steel strands in each of the webs and are arranged along the width direction of the corresponding webs;

[0021] The rotation axis of each of the steering wheels is spatially perpendicular to the width direction of the corresponding web, or the arrangement direction of all the folded steel strands in the corresponding web;

[0022] Each of the folded steel strands is clamped on the upper side of the corresponding steering wheel at the position of the corresponding beam outer conversion point ZW, and then extends outward along the length direction of the small box beam;

[0023] The end face shape of each anchor beam facing the small box beam covers the corresponding end face of the small box beam and the shape of the tensioning anchor rod in the tensioning device on the corresponding side, and an anchor beam support frame is provided below, which is connected to the anchor beam support frame in a movable pair and can move back and forth along the length direction of the small box beam;

[0024] Each of the anchor beams is connected to all of the folded steel strands at the corresponding end faces of the small box beam, and is connected to the tensioning device via the tensioning anchor rods.

[0025] Preferably, the small box girder is further provided with steel bars; and the web plate has a uniform cross-section in the axial direction of the small box girder.

[0026] Preferably, the inner cavity size of the ground trough meets the use requirements of manual maintenance of the ground trough embedded parts, disassembly of the lower anchor plate and the slewing pair between the upper anchor plate and the beam replacement connection, and the size is not less than 1m×1m×1m;

[0027] The opening formed by the ground trough on the pedestal meets the shear resistance bearing capacity requirement under the vertical tension generated by the turning of the folded steel strand.

[0028] Preferably, each of the steering gears is cut from a whole steel plate, or is a steel casting;

[0029] Each of the upper pull rods is made of steel plates, and the plane of the steel plates is parallel to the corresponding webs. The lower ends are connected to the conversion beams through a pair of matching ear plates and pins to form a slewing pair, and the upper ends are embedded in the corresponding webs and have long slots. The corresponding steering gears are inserted into the corresponding long slots and fixed by welding.

[0030] Each of the transfer beams is made of a steel structure, including double channel steels arranged back to back with a gap;

[0031] The gap between each pair of double channel steels is used to pass the corresponding pull-down rod;

[0032] The upper end of each of the pull-down rods passes through the gap between the corresponding double-channel steels and is anchored or welded to the top edge of the corresponding double-channel steels;

[0033] The upper edge of each of the conversion beams is provided with the ear plate along the inclined direction of the corresponding web plate;

[0034] Each group of the ear plates of each conversion beam is provided with two pieces, and both are parallel to the corresponding web plate;

[0035] The spacing between each group of lug plates of each conversion beam meets the requirements for installation of the lug plates of the corresponding upper pull rod;

[0036] A stiffening plate is provided at a position corresponding to each ear plate in each of the conversion beams;

[0037] Each of the stiffening plates is welded and fixed to the upper edge of the corresponding conversion beam;

[0038] Each of the pull rods is a steel rod, and the lower end passing through the corresponding lower pad and the upper end passing through the corresponding upper pad are both provided with external threads for installing anchor nuts.

[0039] Then, each of the conversion beams is provided with bolt holes at the contact position with the corresponding upper pad, and bolts are provided through the bolt holes to fasten the corresponding upper pad, and each of the conversion beams is provided with vertical stiffening ribs within the range corresponding to the upper pad.

[0040] Moreover, each of the upper pads is a whole steel plate, and anchor bolt holes are arranged at the edge positions and the range of the corresponding conversion beams, and a lower tie rod passing hole is arranged at the position where the lower tie rod is arranged between each of the double channel steels, and the corresponding lower tie rod is fixed by installing a pad screw on the lower tie rod passing through each of the lower tie rod passing holes.

[0041] Alternatively, each of the lower tie rods is a steel strand, and a hot-cast alloy end head is provided through the lower end of the corresponding lower pad, and the external thread for mounting the lower anchor nut is provided on the side surface of the hot-cast alloy end head;

[0042] Then, each of the lower pads is a whole steel plate, and holes are provided corresponding to the corresponding lower tie rods, and the edge position and the range of contact with the corresponding ground trough embedded parts are fixed by bolts, and the position of each lower anchor seat concave block is provided with an anchor seat screw hole, and the corresponding lower anchor seat concave block is installed through the lower anchor seat screw hole;

[0043] The anchor comprises an anchor seat convex block, the anchor nut, and the lower anchor seat concave block arranged at the end of each lower tie rod;

[0044] Each of the lower anchor seat concave blocks and the corresponding anchor seat convex blocks form a revolving pair through matching spherical concave and spherical convex, and a through hole for penetrating the corresponding lower tie rod is provided in the radial direction of the center position;

[0045] Each of the concave blocks of the lower anchor seat is fixed to the corresponding lower pad through the corresponding anchor seat, and the mating surface with the corresponding convex block of the anchor seat is greased, so that the corresponding convex block of the anchor seat can slide relative to the corresponding concave block of the lower anchor seat within the range of the spherical surface to form a joint;

[0046] Each of the ground trough embedded parts is arranged in the corresponding ground trough, and is a steel section or a welded steel structure, and the cross section is a channel steel or an I-beam, and is arranged along the axis direction of the small box beam, and the web plate is perpendicular to the plane of the pedestal, and is arranged in an even number of rows, and every 2 rows constitute a group, which is used to install the lower pad and the corresponding lower anchor seat concave block;

[0047] Each of the ground trough embedded parts is anchored in the corresponding ground trough by welding nails or perforated steel plates, and anchor bolt holes are provided in the relevant range corresponding to each concave block of the lower anchor seat.

[0048] Preferably, each of the steering wheels is fixed by a main support frame whose length direction is parallel to the width direction of the corresponding web;

[0049] Each of the main support frames is made of steel including channel steel or rectangular steel pipe, or a structure welded by steel plates, the lower end of which is connected to the base, both sides of which are connected to the transverse support frame, the front side and the rear side along the length direction of the small box beam are connected to the longitudinal support frame, and the side close to the small box beam is closely attached to the end template of the corresponding end of the small box beam, so that the total thickness of the corresponding end template does not exceed 60mm, so that all the corresponding folded steel strands pass through the corresponding end template and reach the corresponding steering wheel in the shortest distance;

[0050] Each of the end formworks comprises a face plate and a stiffening plate framework;

[0051] Each of the steering wheels is sleeved on the wheel axle, and both ends of the edges are provided with chamfered protruding edges to form a groove surrounding the outer circumference, so that the corresponding folded steel strands are stuck in the corresponding groove;

[0052] Each of the axles is inserted into the plate of the main support frame and is fixed by welding or screws;

[0053] Each of the transverse support frames is arranged on the side of the corresponding main support frame to assist the corresponding main support frame in bearing force, and the bottom is fixed to the base to bear the horizontal force and vertical force generated when the folded steel strand at the corresponding end is tensioned;

[0054] Each of the longitudinal support frames is arranged on a side of the corresponding main support frame facing or facing away from the small box beam, and the bottom is fixed to the base, and is used to withstand the horizontal force generated by the corresponding beam end steering device when the folded steel strand at the corresponding end is tensioned;

[0055] Each of the bases comprises a plurality of transversely arranged I-beams, the top of which is fixed to the corresponding main support frame, the corresponding transverse support frame and the corresponding longitudinal support frame, and the bottom of which is fixed to the pedestal.

[0056] Preferably, each of the anchor beams is a tubular structure, including a first anchor beam panel and a second anchor beam panel, the shape of which matches the cross section of the corresponding small box beam and are both arranged perpendicular to the length direction of the small box beam;

[0057] Between the first anchor beam panel and the second anchor beam panel, a first vertical stiffening plate and a second vertical stiffening plate are respectively provided at the inner and outer sides of each web plate, a bottom plate second stiffening plate is provided at the position of each bottom plate, a steel strand steel pipe is provided for each corresponding folded steel strand, and a tension anchor steel pipe is provided for each corresponding tension anchor;

[0058] Each of the second stiffening plates of the bottom plate is fixed to the lower end of each of the corresponding first vertical stiffening plates and the end of each of the second vertical stiffening plates by welding;

[0059] Each of the first vertical stiffening plates and the second vertical stiffening plates on the corresponding side is provided with a web first top stiffening plate covering the width of the corresponding first vertical stiffening plate and the second vertical stiffening plate on the corresponding side at a position corresponding to the top plate;

[0060] Each of the first top stiffening plates of the web is fixed to the lower end of each of the corresponding first vertical stiffening plates and the end of each of the second vertical stiffening plates by welding;

[0061] The plurality of tension anchor steel pipes are arranged in two layers along the vertical direction on the corresponding anchor beams, respectively located above and below the through holes;

[0062] Between the first anchor beam panel and the second anchor beam panel, between every two adjacent layers of the tensioned anchor steel pipes, a first bottom plate stiffening plate parallel to the corresponding second bottom plate stiffening plate is provided at the position of the tensioned anchor steel pipe close to the lower layer, and a first anchor stiffening plate parallel to the corresponding second bottom plate stiffening plate is provided at the position of the tensioned anchor steel pipe close to the upper layer;

[0063] Between the first anchor beam panel and the second anchor beam panel, an anchor second stiffening plate parallel to the corresponding second stiffening plate of the bottom plate is provided above the tension anchor steel pipe of the uppermost layer;

[0064] Both ends of each of the first stiffening plates of the bottom plate, each of the first stiffening plates of the anchor rods, and each of the second stiffening plates of the anchor rods are welded and fixed to the second vertical stiffening plates on the corresponding side;

[0065] Between each of the first stiffening plates of the bottom plate and the corresponding first stiffening plates of the anchor rods, connecting plate third stiffening plates are provided at positions on both sides of the inner hole corresponding to the corresponding small box beam;

[0066] Between each of the first bottom plate stiffening plates and the corresponding second bottom plate stiffening plates, a fourth connecting plate stiffening plate is provided at a position corresponding to the third connecting plate stiffening plate, and a fifth connecting plate stiffening plate is provided at the remaining positions;

[0067] Between each of the first anchor rod stiffening plates and the corresponding second anchor rod stiffening plates, a second connecting plate stiffening plate is provided at a position corresponding to the third connecting plate stiffening plate, and a first connecting plate stiffening plate is provided at the remaining positions;

[0068] Each of the folded steel strands is anchored by a clip after passing through the corresponding anchor beam;

[0069] Each of the tension anchor rods is anchored in the form of a nut after passing through the corresponding anchor beam.

[0070] Preferably, the manufacturing method of each anchor beam is as follows:

[0071] Step A1, placing the first anchor beam panel on the ground, welding the first vertical stiffening plate, the first top stiffening plate of the web plate, the first stiffening plate of the anchor rod, the first stiffening plate of the bottom plate, the first stiffening plate of the connecting plate, the second stiffening plate of the connecting plate, the third stiffening plate of the connecting plate, the fourth stiffening plate of the connecting plate, the fifth stiffening plate of the connecting plate, the steel strand steel pipe and the tension anchor steel pipe to the first anchor beam panel;

[0072] Step A2, the second anchor beam panel is welded and fixed to the second anchor beam panel, the first vertical stiffening plate, the first top stiffening plate of the web plate, the first stiffening plate of the anchor rod, the first stiffening plate of the bottom plate, the first stiffening plate of the connecting plate, the second stiffening plate of the connecting plate, the third stiffening plate of the connecting plate, the fourth stiffening plate of the connecting plate, the fifth stiffening plate of the connecting plate, the steel strand steel pipe and the tension anchor steel pipe;

[0073] Step A3, insert the second stiffening plate of the base plate, the second stiffening plate of the anchor rod and the second vertical stiffening plate between the first anchor beam panel and the second anchor beam panel in sequence, and weld the second stiffening plate of the base plate, the second stiffening plate of the anchor rod and the second vertical stiffening plate in sequence to close the entire anchor beam.

[0074] Preferably, each of the tensioning devices is a T-beam tensioning device with the same span as the small box girder, located at both ends of the pedestal, arranged symmetrically, and a total of two devices are provided.

[0075] Preferably, when the web and the top plate form an angle of 90 degrees,

[0076] The cross section of each of the anchor beams is a rectangle covering the end surface of the small box beam;

[0077] The main support frame of each beam end steering device extends along the width direction of the web and is closely attached to the end mold of the small box beam;

[0078] Each of the internal steering devices of the beam is provided with a spherical support in the longitudinal direction which can adapt to a small turning angle and adapt to the deformation caused by the tensioning of the folded steel strands;

[0079] The height HH of the installation platform of the small box beam bottom mold from the top edge of the pedestal is calculated by the distance H from the centroid of the end face of the precast beam where the folded steel strand passes through from the top edge of the pedestal and the distance h from the bottom edge of the precast beam, that is, HH=Hh.

[0080] The present invention also provides a method for manufacturing a small box beam, which uses the above-mentioned pre-tensioning method small box beam construction device to manufacture the small box beam, comprising the following steps:

[0081] Step B1, calculating various parameters according to the tension force of the folded steel strand and the design state;

[0082] Step B1.1, calculating the stress-free length L0 of each of the folded steel strands, and the stress-free lengths G1 and G2 of the pull-down anchor rods;

[0083] Step B1.2, marking the corresponding positions of the folded steel strand, including the anchor point M at one end, the turning point ZW outside the beam at one end, the turning point ZN inside the beam at one end, the symmetric point O, the turning point ZN' inside the beam at the other end, the turning point ZW' outside the beam at the other end, and the anchor point M' at the other end;

[0084] Step B1.3, calculating the longitudinal displacement L of the folded steel strand at the turning device in each beam;

[0085] Step B1.4, calculating the longitudinal displacement D of the folded steel strand at each beam end turning device;

[0086] Step B1.5, calculating the distance H from the centroid of the folded steel strand passing through the end face of the small box beam to the top edge of the pedestal, and the distance h from the bottom edge of the small box beam;

[0087] Step B2, installing a bottom formwork bracket on the pedestal to form an installation platform for the bottom formwork of the small box beam, or using cast-in-place concrete to form the installation platform;

[0088] The height between the installation platform and the top edge of the pedestal is HH=Hh.

[0089] Step B3, installing the small box girder and the steel bars that are not related to tensioning the folded steel strands;

[0090] Step B4, installing the anchor beam, the beam end steering device and the beam inner steering device;

[0091] When installing the in-beam steering device, a temporary auxiliary bracket needs to be provided to enable it to reach a predetermined position vertically;

[0092] Step B5, insert the entire folded steel strand in the following order: the anchor beam on one side, the beam end steering device on one side, the end template on one side, the beam inner steering device on one side, the beam inner steering device on the other side, the end template on the other side, the other beam end steering device, and the other anchor beam.

[0093] Then roughly position the symmetry point O so that it is aligned with the midpoint of the pedestal;

[0094] Step B6, accurately adjusting the length of the inner-beam steering device, and then adjusting the steering angle of the inner-beam steering device, so that each steering tooth is aligned with the inner-beam steering point ZN at one end or the inner-beam steering point ZN' at the other end;

[0095] Step B7, installing the nut of the tensioning anchor rod of the tensioning device and pressing it against the corresponding anchor beam;

[0096] Step B8, initially tensioning the folded steel strands, controlling the tensioning stress to about 0.1fpk, so that the folded steel strands are tightened, and installing clips on the side of each anchor beam close to the tensioning device to anchor the two ends of the folded steel strands to the anchor beams.

[0097] Step B9, operating the jack of the tensioning device to make the tensioning device tension the folded steel strand as a whole to reach the tensioning control stress, and reviewing the conformity of the elongation of the folded steel strand with the theoretical calculation;

[0098] Step B10, installing the remaining steel bars of the small box girder;

[0099] Step B11, pouring the small box beam concrete and curing it to a predetermined age;

[0100] Step B12, operating the jack to spread the folded steel strand as a whole;

[0101] Step B13, removing all beam end steering devices and the templates of the small box beam;

[0102] Step B14, cutting the upper pull rod of the steering device in the beam along the bottom surface of the small box beam;

[0103] Step B15, cutting the folded steel strands in batches along the end surface of the small box girder and performing corrosion protection on the ends of the steel strands.

[0104] Beneficial effects of the present invention:

[0105] The invention solves the problem of complex spatial state of prefabricated small box beams tensioning folded steel strands by pre-tensioning method, and reduces the difficulty of tensioning equipment design, prefabricated pedestal and on-site construction.

[0106] The internal beam steering device of the present invention can provide reliable steering anchoring for the prestressing force of the small box beam, and can be adapted to the broken line prestressing method T beam and other beam types after modification, so that the pedestal has the production capacity for various beam types.

[0107] The lower tie rod anchor of the present invention has a micro-sliding function in all directions similar to a joint, and can adapt to the longitudinal displacement caused by prestressing.

[0108] The trough conversion beam of the present invention can provide the pull rod with a turning capability perpendicular to the beam body axis, so that the pull rod can follow the direction of the inclined web of the small box beam after passing through the conversion beam. The specific angle can be adjusted according to the inclination angle of the web, thereby improving versatility.

[0109] The anchoring teeth of the steel strand steering rod of the present invention are provided with rounded corners, and a liner is provided between the anchoring teeth and the steel strand, so as to adapt to the steering of the steel strand and avoid cutting the steel strand.

[0110] The present invention adopts the form of being close to the end of the small box beam, which can minimize the complex spatial form formed by the web steel strand after passing through the beam body, reduce the vertical and horizontal deviation of the steel strand between the steering wheel and the end of the small box beam, reduce the volume of the bogie, save space and steel

[0111] The present invention has the form of the steel strands bypassing the steering wheel, and can reduce the loss of the tensioning of the steel strands by the rotation of the wheel, thereby avoiding the damage of the steel strands due to the hard contact and sliding between the steel strands and the bogie.

[0112] The bogie axis of the present invention is parallel to the web of the small box beam, and the roller axis is perpendicular to the small box beam, so that the force generated by the steering of the steel strand can be clearly transmitted to the steering wheel and then to the bogie, avoiding lateral force on it.

[0113] The anchor beam of the present invention is in a form that adapts to the cross-section of a small box beam, which can increase the anchoring position of the steel strand, increase the open space to improve the processing convenience of the anchor beam, improve the convenience of installing and disassembling each steel strand, and improve the versatility of various beam shapes to adapt to the shaping pedestal.

[0114] The centroid of the cross section of the anchor beam of the present invention is arranged in a coincident form with the centroid of the tensioning system, so that the tensioning system can theoretically only generate axial force, thereby greatly reducing the bending moment caused by the eccentricity of the anchor beam.

[0115] By adjusting the height of the bottom template from the pedestal, the centroid of the steel strand passing through the end face of the prefabricated beam can be made to coincide with the centroid of the anchor beam and the tensioning system, so that the tensioning system can theoretically only generate axial force, greatly reducing the bending moment caused by the eccentricity of the anchor beam.

[0116] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Figure 1 A schematic diagram of a small box girder structure in one embodiment of the present invention is shown.

[0118] Figure 2 A schematic diagram of the inner folded steel strand of a small box girder in one embodiment of the present invention is shown.

[0119] Figure 3 A schematic diagram showing the distribution of the folded steel strands near both ends of a small box girder in one embodiment of the present invention is shown.

[0120] Figure 4 A schematic diagram showing the distribution of the folded steel strands near the middle position in a small box girder in one embodiment of the present invention is shown.

[0121] Figure 5 A schematic diagram of any folded steel strand in an embodiment of the present invention is shown.

[0122] Figure 6 A schematic diagram showing a construction device in one embodiment of the present invention manufacturing a small box beam.

[0123] Figure 7 A schematic diagram of a beam inner steering device in one embodiment of the present invention is shown.

[0124] Figure 8 A schematic structural diagram showing a conversion beam provided with a stiffening plate at the ear plate in an embodiment of the present invention.

[0125] Fig. 9 A schematic diagram of the connection structure between the steering gear and the upper pull rod in one embodiment of the present invention is shown.

[0126] Fig.10 A schematic diagram of the connection structure between the upper pull rod and the ear plate in one embodiment of the present invention is shown.

[0127] Fig.11 A schematic diagram of a beam end steering device in one embodiment of the present invention is shown.

[0128] Fig.12 A side schematic diagram of a beam end steering device in one embodiment of the present invention is shown.

[0129] Fig.13A schematic diagram of a beam end steering device in a top view in one embodiment of the present invention is shown.

[0130] Fig.14 A schematic structural diagram of a conversion beam in an embodiment of the present invention is shown.

[0131] Fig.15 A schematic structural diagram of the side surface of a conversion beam in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0132] Example

[0133] like Figures 1 to 15 As shown, a construction device for a small box girder using a pre-tensioning method is shown, wherein the small box girder 1 is a prefabricated box girder of a concrete structure using pre-tensioning method to tension and fold steel strands N2, N3, N4, N5, N6, and N7, and comprises a top plate 102, a web plate 103, a bottom plate 104, a middle partition plate 105, and an end plate 106; it is characterized in that it comprises a small box girder bottom mold 101; and the bottom plate 104 is also provided with an ordinary steel strand N1.

[0134] The small box beam bottom mold 101 is arranged on the pedestal 2;

[0135] The pedestal 2 is provided with a beam inner steering device 3 at the position of the beam inner conversion point ZN corresponding to the folded steel strands N2, N3, N4, N5, N6, N7, and a beam end steering device 4 at the position of the beam outer conversion point ZW;

[0136] Anchor beams 5 and tensioning devices 6 are symmetrically arranged on the outside of the two beam end steering devices 4;

[0137] Each inner-beam steering device 3 is provided with a steering tooth 301 corresponding to each web 103, which can pull the folded steel strands N2, N3, N4, N5, N6, N7 downwards, and a ground groove 7 as a downward pulling space;

[0138] Each ground groove 7 is a local concave structure provided on the pedestal 2 corresponding to the conversion point ZN in the beam;

[0139] Each steering tooth 301 includes multiple downward hook structures corresponding to all the folded steel strands N2, N3, N4, N5, N6, and N7 in the corresponding web 103; the downward hook structures of the steering teeth 301 can prevent the folded steel strands N2, N3, N4, N5, N6, and N7 from sliding outward during tensioning.

[0140] All steering teeth 301 of the steering device 3 in the same beam are connected to the conversion beam 303 through the upper pull rod 302 respectively;

[0141] Each upper tie rod 302 is arranged parallel to the corresponding web 103, the lower end is connected to the corresponding conversion beam 303 in a revolving pair, the upper end is embedded in the corresponding web 103, and is fixed to the corresponding steering gear 301;

[0142] Each transfer beam 303 is arranged in parallel with the small box beam 1, and pulls all the upper pull rods 302 and the corresponding steering gears 301 downwards through the lower pull rods 305 and the corresponding anchors fixed between the ground groove embedded parts 304 in the ground groove 7;

[0143] Each beam end steering device 4 includes a plurality of steering wheels 401 arranged corresponding to each folded steel strand N2, N3, N4, N5, N6, N7 in each web 103 and arranged along the width direction of the corresponding web 103;

[0144] The rotation axis of each steering wheel 401 is spatially perpendicular to the width direction of the corresponding web 103 or the arrangement direction of all the folded steel strands N2, N3, N4, N5, N6, and N7 in the corresponding web 103;

[0145] Each folded steel strand N2, N3, N4, N5, N6, N7 is clamped on the upper side of the corresponding steering wheel 401 at the position of the corresponding beam outer conversion point ZW, and then extends outward along the length direction of the small box beam 1;

[0146] The end face shape of each anchor beam 5 facing the small box beam 1 envelops the corresponding end face of the small box beam 1 and the shape of the tensioning anchor rod 53 in the tensioning device 6 on the corresponding side, and an anchor beam 5 support frame is provided below, which is connected to the anchor beam 5 support frame in a movable pair and can move back and forth along the length direction of the small box beam 1; the anchor beam 5 support frame itself is a conventional measure, and the specific structure will not be repeated.

[0147] Each anchor beam 5 is connected to all the folded steel strands N2, N3, N4, N5, N6, N7 on the corresponding end faces of the small box beam 1, and is connected to the tensioning device 6 through the tensioning anchor rod 53.

[0148] In some embodiments, the small box girder 1 is further provided with steel bars; the web 103 has a uniform cross-section in the axial direction of the small box girder 1 .

[0149] In some embodiments, the inner cavity size of the ground trough 7 meets the use requirements of manual maintenance of the ground trough embedded parts 304, disassembly of the lower anchor plate and the slewing pair between the upper anchor plate and the replacement beam connection, and the size is not less than 1m×1m×1m;

[0150] The opening formed by the ground trough 7 on the pedestal 2 meets the shear resistance requirement under the vertical tension generated by the turning of the folded steel strands N2, N3, N4, N5, N6, and N7.

[0151] In practical applications, the ground trench 7 itself is a conventional structure. In this embodiment, the ground trench 7 exists as a downward traction space and is used to meet the needs of manual maintenance of the ground trench embedded parts 304, disassembly of the lower anchor plate and the swivel pair between the upper anchor plate and the replacement beam connection.

[0152] In some embodiments, each steering gear 301 is cut from a whole steel plate, or is a steel casting;

[0153] Each upper pull rod 302 is made of steel plate, and the plane of the steel plate is parallel to the corresponding web 103. The lower end is connected to the conversion beam 303 through a pair of matching ear plates 306 and a pin to form a swivel pair. The upper end is buried in the corresponding web 103 and has a long groove. The corresponding steering tooth 301 is inserted into the corresponding long groove and welded and fixed. The upper pull rod 302 is set to provide a fulcrum for the steering of the folded steel strand.

[0154] Each transfer beam 303 is made of a steel structure, including double channel steels arranged in a back-to-back gap;

[0155] The gap between each pair of double channel steels is used to pass the corresponding lower tie rod 305;

[0156] The upper end of each pull rod 305 passes through the gap between the corresponding double channel steels and is anchored or welded to the top edge of the corresponding double channel steels;

[0157] The upper edge of each transfer beam 303 is provided with a lug plate 306 along the inclined direction of the corresponding web plate 103;

[0158] Each set of ear plates 306 of each transfer beam 303 is provided with two pieces, and both are parallel to the corresponding web plate 103;

[0159] The spacing of each set of lug plates 306 of each conversion beam 303 is sufficient for the installation of the lug plates 306 of the corresponding upper pull rod 302;

[0160] A stiffening plate 307 is provided at a position corresponding to each ear plate 306 in each conversion beam 303;

[0161] Each stiffening plate 307 is welded and fixed to the upper edge of the corresponding transfer beam 303;

[0162] Each lower tie rod 305 is a steel rod, and the lower end passing through the corresponding lower pad 308 and the upper end passing through the corresponding upper pad 309 are both provided with external threads for mounting the anchor nut 313.

[0163] Then, each transfer beam 303 is provided with bolt holes at the contact position with the corresponding upper pad 309, and bolts are provided through the bolt holes to fasten the corresponding upper pad 309, and each transfer beam 303 is provided with vertical stiffening ribs within the range of the corresponding upper pad 309.

[0164] Moreover, each upper pad 309 is a whole steel plate, and anchor bolt holes are arranged at the edge position and the range of the corresponding conversion beam 303, and a lower tie rod passing hole is arranged at the position where the lower tie rod 305 is arranged between each double channel steel, and the corresponding lower tie rod 305 is fixed by installing a pad screw 310 on the lower tie rod 305 passing through each lower tie rod passing hole.

[0165] Alternatively, each lower tie rod 305 is a steel strand, and a hot-cast alloy end is provided through the lower end of the corresponding lower pad 308, and an external thread for installing the lower anchor nut 313 is provided on the side surface of the hot-cast alloy end;

[0166] Then, each lower pad 308 is a whole steel plate, and holes are provided corresponding to the corresponding lower tie rods 305, and the edge position contacting the corresponding ground groove embedded parts 304 is fixed by bolts 312, and the position corresponding to each lower anchor seat concave block 311 is provided with an anchor seat screw hole, and the corresponding lower anchor seat concave block 311 is installed through the lower anchor seat screw hole;

[0167] The anchor includes an anchor seat convex block 312, an anchor nut 313, and a lower anchor seat concave block 311 arranged at the end of each lower tie rod 305;

[0168] Each lower anchor seat concave block 311 and the corresponding anchor seat convex block 312 form a revolving pair through matching spherical concave and spherical convex, and a through hole for passing the corresponding lower pull rod 305 is provided in the radial direction of the center position;

[0169] Each lower anchor seat concave block 311 is fixed to the corresponding lower pad 308 through the corresponding anchor seat, and the fitting surface with the corresponding anchor seat convex block 312 is greased so that the corresponding anchor seat convex block 312 can slide relative to the corresponding lower anchor seat concave block 311 within the spherical range to form a joint;

[0170] Each ground trough embedded part 304 is arranged in the corresponding ground trough 7, and is a steel structure or a welded steel structure, and the cross section is a channel steel or an I-beam, arranged along the axis direction of the small box beam 1, and the web 103 is perpendicular to the plane of the pedestal 2, arranged in an even number of lanes, and every 2 lanes constitute a group, for installing the lower pad 308 and the corresponding lower anchor seat concave block 311;

[0171] Each ground groove embedded part 304 is anchored in the corresponding ground groove 7 by welding nails or perforated steel plates, and anchor bolt holes are provided in the relevant range corresponding to each lower anchor seat concave block 311.

[0172] In some embodiments, each steering wheel 401 is fixed by a main support frame 402 whose length direction is parallel to the width direction of the corresponding web 103;

[0173] Each main support frame 402 is made of steel including channel steel or rectangular steel pipe, or a steel plate welded structure, the lower end is connected to the base 403, both sides are connected to the transverse support frame 404, the front side and the rear side along the length direction of the small box beam 1 are connected to the longitudinal support frame 405, and the side close to the small box beam 1 is closely attached to the end template 8 of the corresponding end of the small box beam 1, so that the total thickness of the corresponding end template 8 does not exceed 60mm, so that all the corresponding folded steel strands N2, N3, N4, N5, N6, N7 pass through the corresponding end template 8 and reach the corresponding steering wheel 401 with the shortest distance;

[0174] Each end formwork 8 comprises a face plate and a stiffening plate framework;

[0175] Each steering wheel 401 is sleeved on the wheel axle 406, and both ends of the edge are provided with a chamfered protruding edge to form a groove around the outer circumference, so that the corresponding folded steel strands N2, N3, N4, N5, N6, N7 are stuck in the corresponding groove;

[0176] Each axle 406 is inserted into the plate of the main support frame 402 and is fixed by welding or screws;

[0177] Each transverse support frame 404 is arranged on the side of the corresponding main support frame 402 to assist the corresponding main support frame 402 in bearing force, and the bottom is fixed to the base 403 to bear the horizontal force and vertical force generated when the corresponding end of the folded steel strands N2, N3, N4, N5, N6, N7 are tensioned;

[0178] Each longitudinal support frame 405 is arranged on the side of the corresponding main support frame 402 facing or facing away from the small box beam 1, and the bottom is fixed to the base 403, and is used to withstand the horizontal force generated by the corresponding beam end steering device 4 when the folded steel strands N2, N3, N4, N5, N6, N7 at the corresponding end are tensioned;

[0179] Each base 403 includes a plurality of I-beams arranged transversely, the top of which is fixed to the corresponding main support frame 402 , the corresponding transverse support frame 404 and the corresponding longitudinal support frame 405 , and the bottom of which is fixed to the pedestal 2 .

[0180] In some embodiments, each anchor beam 5 is a tubular structure, including a first anchor beam panel P1 and a second anchor beam panel P2, the shape of which matches the cross section of the corresponding small box beam 1 and are both arranged perpendicular to the length direction of the small box beam 1;

[0181] Between the first anchor beam panel P1 and the second anchor beam panel P2, the first vertical stiffening plate JF1 and the second vertical stiffening plate JF2 are respectively provided at the inner and outer positions of each web 103, the bottom plate second stiffening plate JD2 is provided at the position corresponding to each bottom plate 104, the steel strand steel pipe 52 is provided at each corresponding folded steel strand N2, N3, N4, N5, N6, N7, and the tension anchor steel pipe 51 is provided at each corresponding tension anchor 53;

[0182] Each bottom plate second stiffening plate JD2 is fixed to the lower end of each corresponding first vertical stiffening plate JF1 and the end of each second vertical stiffening plate JF2 by welding;

[0183] Each first vertical stiffening plate JF1 and the second vertical stiffening plate JF2 on the corresponding side are provided with a web first top stiffening plate JF11 covering the width of the corresponding first vertical stiffening plate JF1 and the second vertical stiffening plate JF2 on the corresponding side at the position corresponding to the top plate 102;

[0184] Each web first top stiffening plate JF11 is fixed to the lower end of each corresponding first vertical stiffening plate JF1 and the end of each second vertical stiffening plate JF2 by welding;

[0185] A plurality of tension anchor steel pipes 51 are arranged in two layers along the vertical direction on the corresponding anchor beam 5, respectively located above and below the through hole;

[0186] Between the first anchor beam panel P1 and the second anchor beam panel P2, between every two adjacent layers of tension anchor steel pipes 51, a bottom plate first stiffening plate JD1 parallel to the corresponding bottom plate second stiffening plate JD2 is provided at the position of the tension anchor steel pipe 51 close to the lower layer, and an anchor rod first stiffening plate JM1 parallel to the corresponding bottom plate second stiffening plate JD2 is provided at the position of the tension anchor steel pipe 51 close to the upper layer;

[0187] Between the first anchor beam panel P1 and the second anchor beam panel P2, an anchor second stiffening plate JM2 parallel to the corresponding bottom plate second stiffening plate JD2 is provided above the uppermost tension anchor steel pipe 51;

[0188] Both ends of each bottom plate first stiffening plate JD1, each anchor rod first stiffening plate JM1 and each anchor rod second stiffening plate JM2 are welded and fixed to the second vertical stiffening plate JF2 on the corresponding side;

[0189] Between each bottom plate first stiffening plate JD1 and the corresponding anchor rod first stiffening plate JM1, a connecting plate third stiffening plate JL13 is provided at positions on both sides of the inner hole corresponding to the corresponding small box beam 1;

[0190] Between each bottom plate first stiffening plate JD1 and the corresponding bottom plate second stiffening plate JD2, a connecting plate fourth stiffening plate JL14 is provided at a position corresponding to the corresponding connecting plate third stiffening plate JL13, and a connecting plate fifth stiffening plate JL15 is provided at the remaining positions;

[0191] Between each anchor rod first stiffening plate JM1 and the corresponding anchor rod second stiffening plate JM2, a connecting plate second stiffening plate JL12 is provided at the position corresponding to the corresponding connecting plate third stiffening plate JL13, and a connecting plate first stiffening plate JL11 is provided at the remaining positions;

[0192] Each folded steel strand N2, N3, N4, N5, N6, N7 is anchored by a clip after passing through the corresponding anchor beam 5;

[0193] Each tension anchor rod 53 is anchored in the form of a nut after passing through the corresponding anchor beam 5 .

[0194] In some embodiments, the manufacturing method of each anchor beam 5 is as follows:

[0195] Step A1, placing the first anchor beam panel P1 on the ground, welding the first vertical stiffening plate JF1, the first top stiffening plate JF11 of the web plate, the first anchor rod stiffening plate JM1, the first bottom plate stiffening plate JD1, the first connecting plate stiffening plate JL11, the second connecting plate stiffening plate JL12, the third connecting plate stiffening plate JL13, the fourth connecting plate stiffening plate JL14, the fifth connecting plate stiffening plate JL15, the strand steel pipe 52 and the tensioning anchor steel pipe 51 to the first anchor beam panel P1;

[0196] Step A2, second anchor beam panel P2, welding and fixing the second anchor beam panel P2 to the first vertical stiffening plate JF1, the first top stiffening plate JF11 of the web plate, the first anchor rod stiffening plate JM1, the first bottom plate stiffening plate JD1, the first connecting plate stiffening plate JL11, the second connecting plate stiffening plate JL12, the third connecting plate stiffening plate JL13, the fourth connecting plate stiffening plate JL14, the fifth connecting plate stiffening plate JL15, the steel strand steel pipe 52 and the tensioning anchor steel pipe 51;

[0197] Step A3, insert the second stiffening plate JD2 of the bottom plate, the second stiffening plate JM2 of the anchor rod and the second vertical stiffening plate JF2 in sequence between the first anchor beam panel P1 and the second anchor beam panel P2, and weld the second stiffening plate JD2 of the bottom plate, the second stiffening plate JM2 of the anchor rod and the second vertical stiffening plate JF2 in sequence to close the entire anchor beam 5.

[0198] In some embodiments, each tensioning device 6 is a T-beam tensioning device 6 with the same span as the small box girder 1, which is located at both ends of the pedestal 2, arranged symmetrically, and a total of two are provided.

[0199] In practical applications, the T-beam tensioning device 6 itself is a conventional structure. In this embodiment, it is used to pull and tension the anchor beam 5, and its structure will not be described in detail.

[0200] In some embodiments, when the web 103 and the top plate 102 form an angle of 90 degrees,

[0201] The cross section of each anchor beam 5 is a rectangle covering the end surface of the small box beam 1;

[0202] The main support frame 402 of each beam end steering device 4 extends along the width direction of the web 103 and is closely attached to the end mold of the small box beam 1;

[0203] In practical applications, the main support frame 402 should be close to the precast beam end mold to minimize the spatial shape after the steel strand passes through the precast beam, but the beam end steering device 4 cannot invade the bottom mold installation platform.

[0204] Each inner deflection device 3 of the beam is provided with a spherical support in the longitudinal direction which can adapt to a small turning angle and to the deformation caused by the tensioning of the folded steel strands N2, N3, N4, N5, N6, and N7;

[0205] In practical applications, the steering device 3 in the beam should be provided with a spherical support in the longitudinal direction that can adapt to small turning angles to adapt to the deformation caused by the tensioning of the folded steel strands N2, N3, N4, N5, N6, and N7; the upper pull rod 302 should remain parallel to the web 103 in the transverse direction.

[0206] The height HH of the installation platform of the small box beam bottom mold 101 from the top edge of the pedestal 2 is obtained by the distance H from the centroid of the end face of the precast beam where the folded steel strands N2, N3, N4, N5, N6, and N7 pass through the top edge of the pedestal 2 and the distance h from the bottom edge of the precast beam, that is, HH=Hh.

[0207] The present invention also provides a method for manufacturing a small box beam, which uses the above-mentioned pre-tensioning method small box beam construction device to manufacture a small box beam 1, comprising the following steps:

[0208] Step B1, calculating various parameters according to the tension and design status of the folded steel strands N2, N3, N4, N5, N6, and N7;

[0209] Step B1.1, calculating the stress-free length L0 of each folded steel strand N2, N3, N4, N5, N6, N7, and the stress-free lengths G1 and G2 of the pull-down anchor rod 305;

[0210] The stress-free length is a technical term and can be defined as L0;

[0211] In the design state, each folded steel strand N2, N3, N4, N5, N6, N7 and the corresponding tension anchor rod 53 are subjected to stress, the tension is F, the cross-sectional area is A, the corresponding stress is σ=F / A, the corresponding length of the stress state is L', and the elastic modulus is E; according to the material mechanics formula, L'=L0+σ / E*L0; it can be obtained that: L0=L' / (1+σ / E);

[0212] Step B1.2, mark the corresponding positions of the folded steel strands N2, N3, N4, N5, N6, and N7, including the anchor point M at one end, the turning point ZW outside the beam at one end, the turning point ZN inside the beam at one end, the symmetric point O, the turning point ZN' inside the beam at the other end, the turning point ZW' outside the beam at the other end, and the anchor point M' at the other end;

[0213] Step B1.3, calculate the longitudinal displacement L of the folded steel strands N2, N3, N4, N5, N6, N7 at the turning device 3 in each beam;

[0214] Step B1.4, calculate the longitudinal displacement D of the folded steel strands N2, N3, N4, N5, N6, N7 at the turning device 4 at each beam end;

[0215] Step B1.5, calculate the distance H from the centroid of the folded steel strands N2, N3, N4, N5, N6, and N7 passing through the end face of the small box beam 1 to the top edge of the pedestal 2, and the distance h from the bottom edge of the small box beam 1;

[0216] Step B2, installing a bottom formwork bracket on the pedestal 2 to form an installation platform for the small box beam bottom formwork 101, or using cast-in-place concrete to form the installation platform;

[0217] The height between the mounting platform and the top edge of the pedestal 2 is HH=Hh.

[0218] Step B3, installing the steel bars of the small box girder 1 that are not related to the tensioned folded steel strands N2, N3, N4, N5, N6, and N7;

[0219] Step B4, installing the anchor beam 5, the beam end steering device 4 and the beam inner steering device 3;

[0220] When installing the internal beam steering device 3, a temporary auxiliary bracket needs to be provided to enable it to reach the predetermined position vertically;

[0221] Step B5, insert the whole folded steel strands N2, N3, N4, N5, N6, N7, and the order of passing through is: one side anchor beam 5, one side beam end steering device 4, one side end template 8, one side beam inner steering device 3, the other side beam inner steering device 3, the other side end template 8, the other beam end steering device 4, the other anchor beam 5,

[0222] Then perform rough positioning to align the symmetry point O with the midpoint of the pedestal 2;

[0223] Step B6, accurately adjusting the length of the beam inner steering device 3, and then adjusting the steering angle of the beam inner steering device 3, so that each steering tooth 301 is aligned with the beam inner steering point ZN at one end or the beam inner steering point ZN' at the other end;

[0224] Step B7, installing the nut of the tensioning anchor rod 53 of the tensioning device 6 and pressing it against the corresponding anchor beam 5;

[0225] Step B8, perform initial tensioning on the folded steel strands N2, N3, N4, N5, N6, and N7, and control the tensioning stress to about 0.1fpk, so that the folded steel strands N2, N3, N4, N5, N6, and N7 are tightened, and clips are installed on the side of each anchor beam 5 close to the tensioning device 6 to anchor the two ends of the folded steel strands N2, N3, N4, N5, N6, and N7 to the anchor beam 5.

[0226] Step B9, operate the jack of the tensioning device 6, so that the tensioning device 6 tensions the folded steel strands N2, N3, N4, N5, N6, N7 as a whole to achieve tensioning control stress, and review the conformity of the elongation of the folded steel strands N2, N3, N4, N5, N6, N7 with theoretical calculation;

[0227] Step B10, installing the remaining steel bars of the small box beam 1;

[0228] Step B11, pouring concrete of small box beam 1, and curing until the predetermined age;

[0229] Step B12, operate the jack to release the folded steel strands N2, N3, N4, N5, N6, and N7 as a whole;

[0230] Step B13, removing the templates of all beam end steering devices 4 and small box beams 1;

[0231] Step B14, cutting the upper pull rod 302 of the steering device 3 in the beam along the bottom surface of the small box beam 1;

[0232] Step B15: Cut the folded steel strands N2, N3, N4, N5, N6, and N7 in batches along the end face of the small box girder 1 and perform corrosion protection on the ends of the steel strands.

[0233] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A construction device for a pre-tensioned small box girder, wherein the small box girder (1) is a prefabricated concrete box girder using pre-tensioned folded steel strands (N2, N3, N4, N5, N6, N7), comprising a top plate (102), a web plate (103), a bottom plate (104), a middle diaphragm (105) and an end plate (106); characterized in that: It includes a small box beam bottom formwork (101); The small box beam bottom mold (101) is arranged on a pedestal (2); The pedestal (2) is provided with an inner beam steering device (3) at a position corresponding to an inner beam conversion point ZN of the folded steel strands (N2, N3, N4, N5, N6, N7), and a beam end steering device (4) at a position corresponding to an outer beam conversion point ZW; Anchor beams (5) and tensioning devices (6) are symmetrically arranged on the outside of the two beam end steering devices (4); Each of the inner-beam steering devices (3) corresponding to each of the webs (103) is provided with steering teeth (301) capable of pulling the folded steel strands (N2, N3, N4, N5, N6, N7) downwards, and a ground groove (7) serving as a downward pulling space; Each of the ground grooves (7) is a local concave structure arranged on the pedestal (2) corresponding to the conversion point ZN in the beam; Each of the steering teeth (301) comprises a plurality of downward hook-shaped structures corresponding to all of the folded steel strands (N2, N3, N4, N5, N6, N7) in the corresponding web (103); All the steering teeth (301) of the steering device (3) in the same beam are connected to the conversion beam (303) through upper pull rods (302) respectively; Each of the upper pull rods (302) is arranged in parallel with the corresponding web (103), the lower end is connected to the corresponding conversion beam (303) in a revolving pair, the upper end is embedded in the corresponding web (103) and is fixed to the corresponding steering gear (301); Each of the conversion beams (303) is arranged in parallel with the small box beam (1), and pulls all the upper pull rods (302) and the corresponding steering teeth (301) downward through a lower pull rod (305) and a corresponding anchor fixed between the ground trough embedded parts (304) in the ground trough (7); Each of the beam end steering devices (4) comprises a plurality of steering wheels (401) which are arranged corresponding to each of the folded steel strands (N2, N3, N4, N5, N6, N7) in each of the webs (103) and are arranged along the width direction of the corresponding webs (103); The rotation axis of each of the steering wheels (401) is spatially perpendicular to the width direction of the corresponding web (103), or the arrangement direction of all the folded steel strands (N2, N3, N4, N5, N6, N7) in the corresponding web (103); Each of the folded steel strands (N2, N3, N4, N5, N6, N7) is clamped on the upper side of the corresponding steering wheel (401) at the position of the corresponding beam outer conversion point ZW, and then extends outward along the length direction of the small box beam (1); The end face shape of each anchor beam (5) facing the small box beam (1) encompasses the corresponding end face of the small box beam (1) and the shape of the tensioning anchor rod (53) in the tensioning device (6) on the corresponding side, and an anchor beam (5) support frame is provided below, which is connected to the anchor beam (5) support frame in a movable pair and can reciprocate along the length direction of the small box beam (1); Each of the anchor beams (5) is connected to all of the folded steel strands (N2, N3, N4, N5, N6, N7) on the corresponding end faces of the small box beam (1), and is connected to the tensioning device (6) via the tensioning anchor rods (53).

2. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: The small box girder (1) is also provided with steel bars; the web plate (103) has a uniform cross-section in the axial direction of the small box girder (1).

3. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: The inner cavity size of the ground trough (7) meets the use requirements of manual maintenance of the ground trough embedded parts (304), disassembly of the lower anchor plate and the slewing pair between the upper anchor plate and the beam replacement connection, and the size is not less than 1m×1m×1m; The opening formed by the ground trough (7) on the pedestal (2) meets the shear resistance bearing capacity requirements under the vertical tension generated by the turning of the folded steel strands (N2, N3, N4, N5, N6, N7).

4. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: Each of the steering teeth (301) is cut from a whole steel plate, or is a steel casting; Each of the upper pull rods (302) is made of a steel plate, and the plane of the steel plate is parallel to the corresponding web (103). The lower end is connected to the conversion beam (303) through a pair of matching ear plates (306) and a pin to form a rotary pair. The upper end is embedded in the corresponding web (103) and has a long slot. The corresponding steering gear (301) is inserted into the corresponding long slot and fixed by welding. Each of the transfer beams (303) is made of a steel structure, including double channel steels arranged back to back with a gap; The gap between each pair of double channel steels is used to pass the corresponding lower pull rod (305); The upper end of each of the pull-down rods (305) passes through the gap between the corresponding double-channel steels and is fixed on the top edge of the corresponding double-channel steels; The upper edge of each conversion beam (303) is provided with the ear plate (306) along the inclined direction of the corresponding web plate (103); Each group of the ear plates (306) of each conversion beam (303) is provided with two pieces, and both are parallel to the corresponding web plate (103); The spacing between each group of the ear plates (306) of each conversion beam (303) meets the requirements for installation of the ear plates (306) of the corresponding upper pull rod (302); A stiffening plate (307) is provided at a position corresponding to each ear plate (306) in each conversion beam (303); Each of the stiffening plates (307) is welded and fixed to the upper edge of the corresponding conversion beam (303); Each of the lower pull rods (305) is a steel rod, and the lower end passing through the corresponding lower pad (308) and the upper end passing through the corresponding upper pad (309) are both provided with external threads for installing anchor nuts (313). Then, each of the conversion beams (303) is provided with bolt holes at the contact position with the corresponding upper pad (309), and bolts are provided through the bolt holes to fasten the corresponding upper pad (309), and each of the conversion beams (303) is provided with vertical stiffening ribs within the range corresponding to the upper pad (309). Furthermore, each of the upper pads (309) is a whole steel plate, and anchor bolt holes are provided at the edge positions and the range of the corresponding conversion beam (303), and a lower tie rod passing hole is provided at the position where the lower tie rod (305) is provided between each of the double channel steels, and the corresponding lower tie rod (305) is fixed by installing a pad screw (310) on the lower tie rod (305) passing through each of the lower tie rod passing holes. Alternatively, each of the lower pull rods (305) is a steel strand, and a hot-cast alloy end is provided through the lower end of the corresponding lower pad (308), and the external thread for mounting the lower anchor nut (313) is provided on the side surface of the hot-cast alloy end; Then, each of the lower pads (308) is a whole steel plate, and holes are provided corresponding to the corresponding lower tie rods (305), and the edge positions in contact with the corresponding ground trough embedded parts (304) are fixed by bolts (312), and the positions of each lower anchor seat concave block (311) are provided with lower anchor seat screw holes, and the corresponding lower anchor seat concave blocks (311) are installed through the lower anchor seat screw holes; The anchor comprises an anchor seat convex block (312) arranged at the end of each lower tie rod (305), the anchor nut (313), and the lower anchor seat concave block (311); Each of the lower anchor seat concave blocks (311) and the corresponding anchor seat convex blocks (312) form a revolving pair through matching spherical concave and spherical convex, and a through hole for penetrating the corresponding lower tie rod (305) is provided in the radial direction of the center position; Each of the lower anchor seat concave blocks (311) is fixed to the corresponding lower pad (308) through the corresponding anchor seat, and the mating surface with the corresponding anchor seat convex block (312) is greased, so that the corresponding anchor seat convex block (312) can slide relative to the corresponding lower anchor seat concave block (311) within the spherical range to form a joint; Each of the ground trough embedded parts (304) is arranged in the corresponding ground trough (7), and is a steel section or a welded steel structure, and has a cross section of a channel steel or an I-beam, and is arranged along the axis direction of the small box beam (1), with the web (103) perpendicular to the plane of the pedestal (2), and is arranged in an even number of rows, and every two rows form a group, for installing the lower pad (308) and the corresponding lower anchor seat concave block (311); Each of the ground trough embedded parts (304) is anchored in the corresponding ground trough (7) by means of welding nails or perforated steel plates, and an anchor bolt hole is provided in the relevant range corresponding to each of the lower anchor seat concave blocks (311).

5. The construction device of pre-tensioned small box beam according to claim 1, characterized in that: Each of the steering wheels (401) is fixed by a main support frame (402) whose length direction is parallel to the width direction of the corresponding web (103); Each of the main support frames (402) is made of steel including channel steel or rectangular steel pipe, or a structure welded by steel plates, the lower end of which is connected to the base (403), the two sides of which are connected to the transverse support frame (404), the front side and the rear side along the length direction of the small box beam (1) are connected to the longitudinal support frame (405), and the side close to the small box beam (1) is closely attached to the end template (8) of the corresponding end of the small box beam (1), so that the total thickness of the corresponding end template (8) does not exceed 60 mm, so that all the corresponding folded steel strands (N2, N3, N4, N5, N6, N7) pass through the corresponding end template (8) and reach the corresponding steering wheel (401) at the shortest distance; Each of the end templates (8) comprises a face plate and a stiffening plate framework; Each of the steering wheels (401) is sleeved on the wheel axle (406), and both ends of the edges are provided with chamfered protruding edges to form a groove surrounding the outer circumference, so that the corresponding folded steel strands (N2, N3, N4, N5, N6, N7) are stuck in the corresponding groove; Each of the wheel axles (406) is inserted into the plate of the main support frame (402) and is fixed by welding or screws; Each of the transverse support frames (404) is arranged on the side of the corresponding main support frame (402) to assist the corresponding main support frame (402) in bearing force, and the bottom is fixed to the base (403) to bear the horizontal force and vertical force generated when the corresponding end of the folded steel strand (N2, N3, N4, N5, N6, N7) is tensioned; Each of the longitudinal support frames (405) is arranged on a side of the corresponding main support frame (402) facing or facing away from the small box beam (1), and the bottom is fixed to the base (403) to withstand the horizontal force generated on the corresponding beam end steering device (4) when the folded steel strands (N2, N3, N4, N5, N6, N7) at the corresponding end are tensioned; Each base (403) comprises a plurality of transversely arranged I-beams, the top of which is fixed to the corresponding main support frame (402), the corresponding transverse support frame (404) and the corresponding longitudinal support frame (405), and the bottom of which is fixed to the pedestal (2).

6. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: Each of the anchor beams (5) is of a tubular structure, comprising a first anchor beam panel (P1) and a second anchor beam panel (P2) whose shapes match the cross-section of the corresponding small box beam (1) and are arranged perpendicular to the length direction of the small box beam (1); Between the first anchor beam panel (P1) and the second anchor beam panel (P2), a first vertical stiffening plate (JF1) and a second vertical stiffening plate (JF2) are respectively provided at the inner and outer positions of each web plate (103), a bottom plate second stiffening plate (JD2) is provided at the position of each bottom plate (104), a steel strand steel pipe (52) is provided for each corresponding folded steel strand (N2, N3, N4, N5, N6, N7), and a tension anchor steel pipe (51) is provided for each corresponding tension anchor (53); Each of the bottom plate second stiffening plates (JD2) is fixed to the ends of each of the corresponding first vertical stiffening plates (JF1) and each of the second vertical stiffening plates (JF2) by welding; Each of the first vertical stiffening plates (JF1) and the second vertical stiffening plates (JF2) on the corresponding side are provided with a web first top stiffening plate (JF11) at a position corresponding to the top plate (102) and covering the width of the first vertical stiffening plates (JF1) and the second vertical stiffening plates (JF2) on the corresponding side; Each of the web first top stiffening plates (JF11) is fixed to the lower end of each of the first vertical stiffening plates (JF1) and the end of each of the second vertical stiffening plates (JF2) by welding; The plurality of tension anchor steel pipes (51) are arranged in two layers along the vertical direction on the corresponding anchor beam (5), and are respectively located above and below the through hole; Between the first anchor beam panel (P1) and the second anchor beam panel (P2), and between every two adjacent layers of the tensioned anchor steel pipes (51), a first bottom plate stiffening plate (JD1) parallel to the corresponding second bottom plate stiffening plate (JD2) is provided at a position of the tensioned anchor steel pipe (51) close to the lower layer, and a first anchor stiffening plate (JM1) parallel to the corresponding second bottom plate stiffening plate (JD2) is provided at a position of the tensioned anchor steel pipe (51) close to the upper layer; Between the first anchor beam panel (P1) and the second anchor beam panel (P2), an anchor second stiffening plate (JM2) parallel to the corresponding bottom plate second stiffening plate (JD2) is provided above the uppermost tension anchor steel pipe (51); Both ends of each of the first bottom plate stiffening plates (JD1), each of the first anchor rod stiffening plates (JM1) and each of the second anchor rod stiffening plates (JM2) are welded and fixed to the second vertical stiffening plates (JF2) on the corresponding side; Between each of the first bottom plate stiffening plates (JD1) and the corresponding first anchor rod stiffening plates (JM1), connecting plate third stiffening plates (JL13) are provided at positions on both sides of the inner hole corresponding to the corresponding small box beam (1); Between each of the first bottom plate stiffening plates (JD1) and the corresponding second bottom plate stiffening plates (JD2), a fourth connecting plate stiffening plate (JL14) is provided at a position corresponding to the corresponding third connecting plate stiffening plate (JL13), and a fifth connecting plate stiffening plate (JL15) is provided at the remaining positions; Between each anchor rod first stiffening plate (JM1) and the corresponding anchor rod second stiffening plate (JM2), a connecting plate second stiffening plate (JL12) is provided at a position corresponding to the corresponding connecting plate third stiffening plate (JL13), and a connecting plate first stiffening plate (JL11) is provided at the remaining positions; Each of the folded steel strands (N2, N3, N4, N5, N6, N7) is anchored by a clip after passing through the corresponding anchor beam (5); Each tension anchor rod (53) is anchored in the form of a nut after passing through the corresponding anchor beam (5).

7. The construction device for pre-tensioned small box beam according to claim 6, characterized in that: The manufacturing method of each anchor beam (5) is as follows: Step A1, placing the first anchor beam panel (P1) on the ground, welding the first vertical stiffening plate (JF1), the first top stiffening plate of the web plate (JF11), the first anchor rod stiffening plate (JM1), the first stiffening plate of the bottom plate (JD1), the first stiffening plate of the connecting plate (JL11), the second stiffening plate of the connecting plate (JL12), the third stiffening plate of the connecting plate (JL13), the fourth stiffening plate of the connecting plate (JL14), the fifth stiffening plate of the connecting plate (JL15), the steel strand steel pipe (52) and the tension anchor steel pipe (51) to the first anchor beam panel (P1); Step A2, the second anchor beam panel (P2), the second anchor beam panel (P2) is welded and fixed to the first vertical stiffening plate (JF1), the first top stiffening plate (JF11) of the web plate, the first stiffening plate (JM1) of the anchor rod, the first stiffening plate (JD1) of the bottom plate, the first stiffening plate (JL11) of the connecting plate, the second stiffening plate (JL12) of the connecting plate, the third stiffening plate (JL13) of the connecting plate, the fourth stiffening plate (JL14) of the connecting plate, the fifth stiffening plate (JL15) of the connecting plate, the steel strand steel pipe (52) and the tension anchor steel pipe (51); Step A3, insert the second stiffening plate (JD2) of the bottom plate, the second stiffening plate (JM2) of the anchor rod and the second vertical stiffening plate (JF2) in sequence between the first anchor beam panel (P1) and the second anchor beam panel (P2), and weld the second stiffening plate (JD2) of the bottom plate, the second stiffening plate (JM2) of the anchor rod and the second vertical stiffening plate (JF2) in sequence to close the entire anchor beam (5).

8. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: Each of the tensioning devices (6) is a T-beam tensioning device (6) having the same span as the small box beam (1), and is located at both ends of the pedestal (2), arranged symmetrically, with two devices in total.

9. The construction device for pre-tensioned small box beam according to claim 1, characterized in that: When the web (103) and the top plate (102) form an angle of 90 degrees, The cross section of each anchor beam (5) is a rectangle covering the end surface of the small box beam (1); The main support frame (402) of each beam end steering device (4) extends along the width direction of the web (103) and is closely attached to the end mold of the small box beam (1); Each of the inner-beam steering devices (3) is longitudinally provided with a spherical support capable of adapting to a small turning angle, so as to adapt to the deformation caused by the tensioning of the folded steel strands (N2, N3, N4, N5, N6, N7); The height HH of the installation platform of the small box beam bottom mold (101) from the top edge of the pedestal (2) is obtained by the distance H from the centroid of the end face of the precast beam where the folded steel strands (N2, N3, N4, N5, N6, N7) pass through from the top edge of the pedestal (2) and the distance h from the bottom edge of the precast beam, that is, HH=Hh.

10. A method for manufacturing a small box beam, characterized in that: The small box girder (1) is manufactured by using the pre-tensioned small box girder construction device as claimed in any one of claims 1 to 7, comprising the following steps: Step B1, calculating various parameters according to the tension and design state of the folded steel strands (N2, N3, N4, N5, N6, N7); Step B1.1, calculating the stress-free length L0 of each of the folded steel strands (N2, N3, N4, N5, N6, N7), and the stress-free lengths G1 and G2 of the pull-down anchor rod (305); Step B1.2, mark the corresponding positions of the folded steel strands (N2, N3, N4, N5, N6, N7), including the anchor point M at one end, the turning point ZW outside the beam at one end, the turning point ZN inside the beam at one end, the symmetric point O, the turning point ZN' inside the beam at the other end, the turning point ZW' outside the beam at the other end, and the anchor point M' at the other end; Step B1.3, calculating the longitudinal displacement L of the folded steel strands (N2, N3, N4, N5, N6, N7) at the turning device (3) in each beam; Step B1.4, calculating the longitudinal displacement D of the folded steel strands (N2, N3, N4, N5, N6, N7) at each beam end turning device (4); Step B1.5, calculating the distance H between the centroid of the folded steel strand (N2, N3, N4, N5, N6, N7) passing through the end face of the small box beam (1) and the top edge of the pedestal (2), and the distance h from the bottom edge of the small box beam (1); Step B2, installing a bottom formwork bracket on the pedestal (2) to form an installation platform for the bottom formwork (101) of the small box beam, or using cast-in-place concrete to form the installation platform; The height between the installation platform and the top edge of the pedestal (2) is HH=Hh. Step B3, installing the steel bars of the small box girder (1) that are not related to tensioning the folded steel strands (N2, N3, N4, N5, N6, N7); Step B4, installing the anchor beam (5), the beam end steering device (4) and the beam inner steering device (3); When installing the inner beam steering device (3), a temporary auxiliary bracket needs to be provided to enable it to reach a predetermined position vertically; Step B5, insert the entire folded steel strand (N2, N3, N4, N5, N6, N7) in the following order: the anchor beam (5) on one side, the beam end steering device (4) on one side, the end template (8) on one side, the beam inner steering device (3) on one side, the beam inner steering device (3) on the other side, the end template (8) on the other side, the other beam end steering device (4), and the other anchor beam (5). Then roughly position the device so that the symmetry point O is aligned with the midpoint of the base (2); Step B6, accurately adjusting the length of the beam inner steering device (3), and then adjusting the steering angle of the beam inner steering device (3), so that each steering tooth (301) is aligned with the beam inner steering point ZN at one end or the beam inner steering point ZN' at the other end; Step B7, installing the nut of the tensioning anchor rod (53) of the tensioning device (6) and pressing it against the corresponding anchor beam (5); Step B8, initially tensioning the folded steel strands (N2, N3, N4, N5, N6, N7), controlling the tensioning stress to about 0.1fpk, so that the folded steel strands (N2, N3, N4, N5, N6, N7) are tightened, and a clip is installed on the side of each anchor beam (5) close to the tensioning device (6) to anchor the two ends of the folded steel strands (N2, N3, N4, N5, N6, N7) to the anchor beam (5). Step B9, operating the jack of the tensioning device (6) so that the tensioning device (6) tensions the folded steel strands (N2, N3, N4, N5, N6, N7) as a whole to achieve tensioning control stress, and reviewing the conformity of the elongation of the folded steel strands (N2, N3, N4, N5, N6, N7) with theoretical calculation; Step B10, installing the remaining steel bars of the small box girder (1); Step B11, pouring concrete of the small box beam (1), and curing until it reaches a predetermined age; Step B12, operating the jack to release the folded steel strands (N2, N3, N4, N5, N6, N7) as a whole; Step B13, removing all beam end steering devices (4) and the templates of the small box beam (1); Step B14, cutting the upper pull rod (302) of the steering device (3) in the beam along the bottom surface of the small box beam (1); Step B15, cutting the folded steel strands (N2, N3, N4, N5, N6, N7) in batches along the end face of the small box girder (1) and performing corrosion protection on the ends of the steel strands.

Images