Pre-tensioning method for prefabricating small box girder and construction method thereof

Abstract

The application discloses a pre-tensioning method prefabricated small box girder and a construction method thereof. The pre-tensioning method prefabricated small box girder comprises a bottom plate, two webs, a first prestressed member and a second prestressed member. The bottom plate extends along a first direction. The two webs are respectively connected to opposite edges of the bottom plate along the first direction. The first prestressed member is arranged in the bottom plate along the first direction. The second prestressed member is arranged in the web along a direction which forms a certain angle with the first direction, and a first end of the second prestressed member is located in the web, and a second end of the second prestressed member is located on a side of the bottom plate which is away from the web. The pre-tensioning method prefabricated small box girder does not need to be provided with a prestressed pipe, thereby simplifying a processing procedure, reducing prestress loss caused by friction between a prestress beam and the prestressed pipe, improving structural durability of the prefabricated small box girder and reducing cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge construction, in particular to a precast small box girder by pretensioning method and a construction method thereof. BACKGROUND

[0002] The precast small box girder is widely used in highway bridges and urban bridges because of its reliable quality, short production and processing period, convenient and safe assembly at the construction site, beautiful appearance and strong durability.

[0003] In the prior art, the precast small box girder is processed by the pretensioning method, which has the following disadvantages: 1. The precast small box girder needs to be provided with a prestressed pipe and a special anchor, which cannot be reused and increases the cost; 2. The prestressed pipe makes it difficult to vibrate the concrete below the pipe, and the insufficient vibration is prone to cause bubbles or cavities, which affects the appearance and internal quality of the structure, and the prestressed pipe is prone to damage and leakage, which causes blockage, and it is difficult to dredge the pipe, thereby increasing the construction cost and the construction period; 3. The prestressed pipe is not compacted, which is prone to cause gaps between the prestressed steel bar and the concrete and lead to corrosion of the steel strand, or the prestressed steel bar is not grouted in time after tensioning, which is prone to cause the prestressed steel bar to retract, further increase the loss of prestress, and be unfavorable to the durability of the box girder structure; 4. For the whole long prestressed beam, it is difficult to ensure the uniform distribution of the prestressed steel bar tension in the tensioning process, and the friction force generated by the contact between the prestressed steel bar and the pipe wall on the curved long pipe causes a prestress loss of up to 40%, which greatly reduces the effective prestress and affects the overall stress performance of the structure, the structural safety of the beam body and the service life. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a precast small box girder by pretensioning method, which does not need to be provided with a prestressed pipe, simplifies the processing procedure, reduces the prestress loss caused by the friction between the prestressed beam and the prestressed pipe, improves the structural durability of the precast small box girder, and reduces the cost.

[0005] The present application also aims to provide a construction method of the precast small box girder by pretensioning method.

[0006] The precast small box girder by pretensioning method according to the embodiment of the first aspect of the present application comprises: a bottom plate extending along a first direction; two webs respectively connected to opposite sides of the bottom plate along the first direction; a first prestressed member arranged in the bottom plate along the first direction; and a second prestressed member arranged in the web along a direction forming a certain angle with the first direction, with a first end located in the web and a second end located on a side of the bottom plate away from the web.

[0007] The pre-tensioning method prefabricated small box girder according to the present application has the following advantages: the second prestressed member is arranged along a direction at an angle with the first direction, and the first end of the second prestressed member is located at the web, and the second end is located at the bottom plate away from the web, compared with the curve arrangement in the prior art, the positioning of the prestressed member is simpler, the construction precision requirement is lower, the linear shape is easier to match the design coordinates, and the production efficiency is improved; meanwhile, compared with the post-tensioning method in the prior art, the pre-tensioning method does not need to arrange prestressed pipe, thereby reducing the engineering cost, and avoiding the problems of structure appearance and internal quality caused by the arrangement of the prestressed pipe; the prestressed member also does not need to be bundled and arranged in the prestressed pipe, each prestressed member can be in full contact with the concrete, so that the prestress in the small box girder is more uniformly distributed, and the performance of the small box girder is optimized.

[0008] According to some embodiments of the present application, along the first direction, the web is provided with at least one set of two symmetrical second prestressed members, and the second ends of the two symmetrical second prestressed members are respectively located on the two sides of the center line of the web along the first direction.

[0009] According to some embodiments of the present application, along the direction away from the web, the first prestressed member includes first upper prestressed members, first middle prestressed members and first lower prestressed members arranged at intervals.

[0010] Along the width direction of the bottom plate, the first upper prestressed members, the first middle prestressed members and the first lower prestressed members are respectively arranged at intervals.

[0011] According to some embodiments of the present application, the ends of the first upper prestressed members and the first middle prestressed members are respectively provided with first failure sections and second failure sections, and the length l1 of the first failure section is greater than the length l2 of the second failure section.

[0012] According to some embodiments of the present application, the outer surface of the first failure section is sleeved with a first isolation member, and a first lubricating layer is arranged between the first failure section and the first isolation member.

[0013] According to some embodiments of the present application, along the width direction of the web, the second prestressed member includes second upper prestressed members and second lower prestressed members arranged at intervals.

[0014] Along the width direction of the bottom plate, the second upper prestressed members and the second lower prestressed members are respectively arranged at intervals.

[0015] According to some embodiments of the present application, the angle between the second upper prestressed member and the first direction is α1, and 5°< α1< 20°.

[0016] The included angle between the second lower pre-stressed member and the first direction is α2, and 5°<α2<20°.

[0017] According to some embodiments of the present application, α1=α2.

[0018] According to some embodiments of the present application, the distance from the intersection of the second end of the second pre-stressed member and the bottom plate to the center line of the web along the first direction is l3, and the length of the bottom plate along the first direction is l4, wherein (1 / 6)l4

[0019] The construction method according to the second aspect of the embodiments of the present application is applied to the precast small box girder by the pre-tensioning method in the above embodiments, and comprises the following steps:

[0020] Step 1, the first pre-stressed member and the second pre-stressed member are arranged in the bottom plate and the web respectively, and the first pre-stressed member and the second pre-stressed member are tensioned;

[0021] Step 2, the concrete is poured into the bottom plate and the web.

[0022] According to the construction method of the embodiments of the present application, the precast small box girder by the pre-tensioning method in the above embodiments is adopted, and the engineering cost is saved.

[0023] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic view of an elevation of the precast small box girder according to the embodiments of the present application;

[0025] Figure 2 is a schematic view of the arrangement of the pre-stressed members in the precast small box girder according to the embodiments of the present application;

[0026] Figure 3 is a schematic view of the failure section in the precast small box girder according to the embodiments of the present application;

[0027] Figure 4 is Figure 1 a schematic view of A-A in FIG.

[0028] Figure 5 is Figure 1 a schematic view of B-B in FIG.

[0029] Figure 6 is Figure 1 a schematic view of C-C in FIG.

[0030] Figure 7 is Figure 1 a schematic view of D-D in FIG.

[0031] Reference signs:

[0032] precast small box girder 100,

[0033] bottom plate 10, first prestressing member 11, first upper prestressing member 111, first middle prestressing member 112, first lower prestressing member 113, first failure section 114, first isolation member 114a, first lubricating layer 114b, second failure section 115, second isolation member 115a, second lubricating layer 115b, center line 12,

[0034] web plate 20, second prestressing member 21, second upper prestressing member 211, second lower prestressing member 212. DETAILED DESCRIPTION

[0035] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the same or like reference numerals and characters are used throughout the drawing figures and the following description to indicate like components. The embodiments described below are merely exemplary for the purposes of explanation and are not intended to limit the application, which is set forth in the claims.

[0036] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of explanation, specific details are set forth in the following description of the embodiments to provide a thorough understanding of the present application. However, it will also be apparent to one of ordinary skill in the art that the present application can be practiced without the specific details. In other instances, well-known structures and devices are shown in block diagram form to avoid obscuring the present application. Furthermore, the present application provides various examples of the processes and materials used in the various embodiments. One of ordinary skill in the art can recognize that other processes and / or materials can be used without departing from the scope of the present application.

[0037] A precast small box girder 100 according to embodiments of the present application is described below with reference to the attached drawings.

[0038] Referring to Figure 1 , Figure 2 , Figures 4-7 , the precast small box girder 100 according to embodiments of the first aspect of the present application comprises a bottom plate 10, two web plates 20, a first prestressing member 11 and a second prestressing member 21.

[0039] Referring to Figure 1 , the bottom plate 10 extends along a first direction. Exemplarily, the first direction can be the length direction of the bottom plate 10.

[0040] Referring to Figures 4-7The two webs 20 are respectively connected to opposite sides of the bottom plate 10 along the first direction to form a chamber with an open top with the bottom plate 10. For example, the two webs 20 are located on the same side of the bottom plate 10 and are inclined away from each other, that is, the distance between the ends of the two webs 20 connected to the bottom plate 10 is less than the distance between the other ends of the two webs 20.

[0041] In some embodiments, referring to Figures 4-7 , the prefabricated small box girder 100 further comprises a top plate connected to the other ends of the two webs 20.

[0042] Referring to Figure 1 and Figure 2 , the first prestressed member 11 is arranged in the bottom plate 10 along the first direction to provide prestress to the structure of the bottom plate 10. The second prestressed member 21 is arranged in the web 20 along a direction at an angle to the first direction, that is, the second prestressed member 21 is arranged in a straight line in the web 20. The first end of the second prestressed member 21 is located in the web 20, and the second end is located on the side of the bottom plate 10 away from the web 20. Compared with the curved arrangement of the prior art, the positioning of the prestressed member is simpler, the construction precision requirement is lower, the linear shape is easier to match the design coordinates, and the production efficiency is improved. For example, the two ends of the second prestressed member 21 can be anchored to the pedestal structure by anchorages or the like.

[0043] The pretensioning method prefabricated small box girder 100 of the present application does not need to set a prestressed pipe, simplifies the processing procedure, reduces the prestress loss caused by the friction between the prestressed bundle and the prestressed pipe, improves the structural durability of the prefabricated small box girder 100, and reduces the cost.

[0044] Thus, referring to Figure 1 , Figure 2 , Figures 4-7 , according to the pretensioning method prefabricated small box girder 100 of the present application, by arranging the second prestressed member 21 in the web 20 along a direction at an angle to the first direction, and arranging the first end of the second prestressed member 21 in the web 20 and the second end on the side of the bottom plate 10 away from the web 20, compared with the curved arrangement of the prior art, the positioning of the prestressed member is simpler, the construction precision requirement is lower, the linear shape is easier to match the design coordinates, and the production efficiency is improved. At the same time, compared with the post-tensioning method of the prior art, the pretensioning method does not need to set a prestressed pipe, thereby reducing the engineering cost and avoiding the problems of structural appearance and internal quality caused by the setting of the prestressed pipe. The prestressed members also do not need to be bundled and arranged in the prestressed pipe, each prestressed member can be in full contact with the concrete, so that the prestress in the small box girder is more uniformly distributed, and the performance of the small box girder is optimized.

[0045] In some embodiments, the second prestressed member 21 can be arranged at the end of the web 20 along the first direction, at the top plate opposite to the web 20, or at both the end of the web 20 along the first direction and the top plate opposite to the web 20.

[0046] When the second prestressed member 21 is arranged at the end of the web 20 along the first direction, the first end of the second prestressed member 21 is located at the end of the web 20 away from the bottom plate 10 along the height direction of the prefabricated small box girder 100.

[0047] The first prestressed member 11 and the second prestressed member 21 can be prestressed steel bars or the like.

[0048] In some embodiments of the present application, referring to Figure 1 and Figure 2 , along the first direction, the web 20 is provided with at least one set of two symmetric second prestressed members 21, and the second ends of the two symmetric second prestressed members 21 in the set are respectively located on both sides of the center line 12 of the web 20 along the first direction.

[0049] By arranging at least one set of two symmetric second prestressed members 21 along the first direction, prestress can be provided at both ends of the girder body. The second ends of the two second prestressed members 21 are respectively located on both sides of the center line 12 of the web 20 along the first direction, which prevents the two prestressed members from crossing, facilitates arrangement, and balances the prestress on both sides of the center line 12 of the girder body along the first direction.

[0050] It can be understood that, since the two prestressed members in a set are symmetrically arranged, the distance between the second end of each prestressed member and the center line 12 of the web 20 along the first direction is the same, and the inclination angle of each prestressed member is the same.

[0051] In some embodiments of the present application, referring to Figure 1 and Figure 4 , along the direction away from the web 20, the first prestressed member 11 comprises a first upper prestressed member 111, a first middle prestressed member 112, and a first lower prestressed member 113 arranged at intervals; and along the width direction of the bottom plate 10, the first upper prestressed member 111, the first middle prestressed member 112, and the first lower prestressed member 113 are respectively arranged at intervals.

[0052] The multiple layers of prestressed members arranged along the direction away from the web 20, and the multiple prestressed members arranged at intervals in each layer, improve the prestress of the bottom plate 10.

[0053] It can be understood that the intervals between two adjacent ones of the first upper prestressing members 111, the first middle prestressing members 112 and the first lower prestressing members 113 can be the same or different. Preferably, the intervals between the first upper prestressing members 111 and the first middle prestressing members 112, and between the first middle prestressing members 112 and the first lower prestressing members 113 are the same, so that the prestress of the bottom plate 10 in the thickness direction is relatively uniform.

[0054] Similarly, the plurality of first upper prestressing members 111 can be arranged at the same intervals or different intervals. Preferably, the plurality of first upper prestressing members 111 are arranged at the same intervals. The plurality of first middle prestressing members 112 can be arranged at the same intervals or different intervals. Preferably, the plurality of first middle prestressing members 112 are arranged at the same intervals. The plurality of first lower prestressing members 113 can be arranged at the same intervals or different intervals. Preferably, the plurality of first lower prestressing members 113 are arranged at the same intervals.

[0055] The intervals between two adjacent first upper prestressing members 111, the intervals between two adjacent first middle prestressing members 112 and the intervals between two adjacent first lower prestressing members 113 can be the same, two of them can be the same, or none of them can be the same. Preferably, the intervals between two adjacent first upper prestressing members 111, the intervals between two adjacent first middle prestressing members 112 and the intervals between two adjacent first lower prestressing members 113 are the same.

[0056] In some embodiments of the present application, with reference to Figure 2 and Figure 3 the end portions of the first upper prestressing members 111 and the first middle prestressing members 112 are respectively provided with first failure sections 114 and second failure sections 115, and the length l1 of the first failure sections 114 is greater than the length l2 of the second failure sections 115.

[0057] By respectively providing the first failure sections 114 and the second failure sections 115 at the end portions of the first upper prestressing members 111 and the first middle prestressing members 112, and by making the length of the first failure sections 114 greater than the length of the second failure sections 115, the small box girder has better bearing capacity and prestress.

[0058] Specifically, the two end portions of the first upper prestressing members 111 are respectively provided with the first failure sections 114, and the first failure sections 114 extend from the end portions to the middle portions of the first upper prestressing members 111. Similarly, the two end portions of the first middle prestressing members 112 are respectively provided with the second failure sections 115, and the second failure sections 115 extend from the end portions to the middle portions of the first middle prestressing members 112.

[0059] The lengths of the first failure sections 114 and the second failure sections 115 can be set according to actual construction needs, so as to improve the bearing capacity and the prestress of the small box girder.

[0060] In some embodiments of the present application, referring to Figure 2 and Figure 3 The outer surface of the first failure section 114 is sleeved with a first isolation member 114a, and a first lubricating layer 114b is arranged between the first failure section 114 and the first isolation member 114a.

[0061] By sleeving the outer surface of the first failure section 114 with the first isolation member 114a, the first isolation member 114a is in contact with the concrete when the concrete is poured, so that the concrete is isolated from the first upper prestressed member 111. At the same time, the first lubricating layer 114b is arranged between the first failure section 114 and the first isolation member 114a, so that the first upper prestressed member 111 moves relative to the first isolation member 114a when it is pulled back, so that the concrete in the first failure section 114 has no prestress.

[0062] Correspondingly, the outer surface of the second failure section 115 is sleeved with a second isolation member 115a, and a second lubricating layer 115b is arranged between the second failure section 115 and the second isolation member 115a.

[0063] In some embodiments, the first lubricating layer 114b and the second lubricating layer 115b can be lubricating oil or the like, for example, butter or the like. The first isolation member 114a and the second isolation member 115a can be an isolation pipe or the like sleeved on the first upper prestressed member 111 and the first middle prestressed member 112. For example, the first isolation member 114a and the second isolation member 115a can be a hard plastic pipe or a plastic film or the like.

[0064] In some embodiments of the present application, referring to Figure 2 and Figure 4 Along the width direction of the web plate 20, the second prestressed member 21 comprises a plurality of second upper prestressed members 211 and second lower prestressed members 212 arranged at intervals; along the width direction of the bottom plate 10, the second upper prestressed members 211 and the second lower prestressed members 212 are respectively arranged at intervals.

[0065] By arranging the second upper prestressed members 211 and the second lower prestressed members 212 at intervals along the width direction of the web plate 20, and arranging a plurality of second upper prestressed members 211 and second lower prestressed members 212 at intervals along the width direction of the bottom plate 10, the prestress of the beam body can be improved, and the use performance of the beam body structure can be ensured.

[0066] Specifically, the plurality of second upper prestressed members 211 can be arranged at the same interval, or can be arranged at different intervals. Preferably, the plurality of second upper prestressed members 211 are arranged at the same interval. The plurality of second lower prestressed members 212 can be arranged at the same interval, or can be arranged at different intervals. Preferably, the plurality of second lower prestressed members 212 are arranged at the same interval.

[0067] In some embodiments of the present application, with reference to Figure 2 , the angle between the second upper prestressed member 211 and the first direction is α1, and 5°<α1<20°; the angle between the second lower prestressed member 212 and the first direction is α2, and 5°<α2<20°.

[0068] By setting the angles α1 and α2 between the second upper prestressed member 211 and the second lower prestressed member 212 and the first direction to be 5°-20°, the second end of the second prestressed member can be close to the middle part of the beam body, thereby ensuring the prestress of the beam body.

[0069] Specifically, the angle α1 between the second upper prestressed member 211 and the first direction can be 5°, 6°, 7°, 8°, 10°, 12°, 15°, 18°, 20°, etc. Similarly, the angle α1 between the second upper prestressed member 211 and the first direction can be 5°, 6°, 7°, 8°, 10°, 12°, 15°, 18°, 20°, etc.

[0070] In some embodiments of the present application, with reference to Figure 2 , α1=α2.

[0071] By setting the angles between the second upper prestressed member 211 and the second lower prestressed member 212 and the first direction to be the same, the setting is facilitated, the construction is facilitated, the construction difficulty is reduced, and the construction efficiency is improved.

[0072] It can be understood that the angle between the second upper prestressed member 211 and the first direction and the angle between the second lower prestressed member 212 and the first direction can also be set to be different. At this time, in order to avoid the intersection of the second upper prestressed member 211 and the second lower prestressed member 212, the angle α1 between the second upper prestressed member 211 and the first direction should be less than the angle α2 between the second lower prestressed member 212 and the first direction, and the difference can be 3°-5°.

[0073] In some embodiments of the present application, with reference to Figure 1 , the distance from the intersection of the second end of the second prestressed member 21 and the bottom plate 10 to the center line 12 of the web plate 20 along the first direction is l3, and the length of the bottom plate 10 along the first direction is l4, wherein (1 / 6)l4

[0074] By setting the distance from the intersection of the second end of the second prestressed member 21 and the bottom plate 10 to the center line 12 of the web plate 20 along the first direction to be l3 to be (1 / 6)l4≤l3≤(3 / 10)l4, the use performance of the beam body is ensured, and the construction setting is facilitated.

[0075] Specifically, l3 can be (1 / 6)l4, (1 / 5)l4, (1 / 4)l4, (7 / 30)l4, (4 / 15)l4, (3 / 10)l4, etc.

[0076] According to the construction method of the second aspect of the present application, the pre-tensioning method precast small box girder 1001 in the above-mentioned embodiments is applied, which comprises the following steps:

[0077] Step 1, the first prestressed member 11 and the second prestressed member 21 are arranged in the bottom plate 10 and the web plate 20 respectively, and the first prestressed member 11 and the second prestressed member 21 are tensioned;

[0078] The two ends of the first prestressed member 11 can be anchored to the pedestal at the end of the precast small box girder 100 by the anchoring assembly. The end of the second prestressed member 21 located in the web plate 20 can be anchored to the pedestal at the end of the precast small box girder 100 by the anchoring assembly, and the other end can be anchored to the pedestal at the bottom of the small box girder.

[0079] The tensioning of the first prestressed member 11 and the second prestressed member 21 can be achieved by a jack or the like.

[0080] Step 2: pouring concrete into the bottom plate 10 and the web plate 20.

[0081] According to the construction method of the embodiment of the present application, the pre-tensioning method precast small box girder 100 in the above-mentioned embodiments is adopted, which saves the engineering cost.

[0082] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0083] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, they can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection, or communication; can be directly connected, or indirectly connected through an intermediate medium; can be the communication or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0084] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or means that the first feature is horizontally lower than the second feature.

[0085] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0086] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A precast small box girder by the pre-tensioning method, characterized in that, The application relates to a floor slab, which comprises the following components: a bottom plate extending along a first direction; two webs respectively connected to opposite sides of the bottom plate along the first direction; a first prestressed member arranged in the bottom plate along the first direction and a second prestressed member arranged in the web along a direction at an angle to the first direction, with a first end located in the web and a second end located on a side of the bottom plate away from the web; along the first direction, the web is provided with at least one set of two symmetrical second prestressed members, and the second ends of the two symmetrical second prestressed members are respectively located on two sides of a center line of the web along the first direction; along a direction away from the web, the first prestressed member comprises a first upper prestressed member, a first middle prestressed member and a first lower prestressed member arranged at intervals; along the width direction of the bottom plate, the first upper prestressed member, the first middle prestressed member and the first lower prestressed member are respectively arranged at intervals; the end of the first upper prestressed member and the first middle prestressed member is respectively provided with a first failure section and a second failure section, and the length l1 of the first failure section is greater than the length l2 of the second failure section; the outer surface of the first failure section is sleeved with a first isolation member, and a first lubricating layer is arranged between the first failure section and the first isolation member.

2. The precast small box girder by the pre-tensioning method according to claim 1, characterized in that, along the width direction of the web, the second prestressed member comprises a second upper prestressed member and a second lower prestressed member arranged at intervals; along the width direction of the bottom plate, the second upper prestressed member and the second lower prestressed member are respectively arranged at intervals.

3. The precast small box girder by the pre-tensioning method according to claim 2, characterized in that, the angle between the second upper prestressed member and the first direction is alpha1, and 5 DEG < alpha1 < 20 DEG; the angle between the second lower prestressed member and the first direction is alpha2, and 5 DEG < alpha2 < 20 DEG.

4. The precast small box girder by the pre-tensioning method according to claim 3, characterized in that, α1=α2。 5. The precast small box girder by the pre-tensioning method according to claim 1, characterized in that, the distance between the intersection of the second end of the second prestressed member and the bottom plate and the center line of the web along the first direction is l3, and the length of the bottom plate along the first direction is l4, wherein (1 / 6) l4 < l3 < (3 / 10) l4.

6. A construction method applied to the precast small box girder of the cantilever method according to any one of claims 1-5, characterized in that, The application further relates to a method for manufacturing the floor slab, which comprises the following steps: step 1, arranging the first prestressed member and the second prestressed member in the bottom plate and the web respectively, and tensioning the first prestressed member and the second prestressed member; step 2, pouring concrete into the bottom plate and the web.

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