Expansion joint construction method based on prefabricated T-beam end plate top plate descending cast-in-place

Abstract

The invention discloses an expansion joint construction method based on prefabricated T-beam end head top plate special-shaped post-pouring. The expansion joint construction method comprises the following steps that S1, a prefabricated T-beam is machined; s2, mounting a prefabricated T beam; s3, wet joints are constructed; s4, backfilling a notch; s5, paving a bridge deck; s6, a groove sealing plate is constructed; s7, installing an expansion joint device; and S8, backfilling and repairing treatment. The problems that according to a traditional notch construction method, positioning of the embedded bars is not accurate, the size error is large, slab staggering is likely to happen to the beam end, the size error of the reserved gap of the expansion joint is large, and construction of the expansion joint is affected are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a method for constructing expansion joints based on cast-in-place lowering of a top plate at the end of a prefabricated T-beam. Background Art

[0002] Expansion joint construction is commonly involved in highway projects, municipal road projects, railway projects and bridge projects, and expansion joint technology has become relatively mature after years of development.

[0003] For the construction of bridge expansion joints, the slot construction method is currently widely used, and its specific steps are as follows: (1) When prefabricating beams, embed the expansion joint device connecting steel bars at the beam ends; (2) After the asphalt paving is completed, accurately locate the expansion joint slot, use a cutting machine to cut along the marking line, and then use a jackhammer and a hydraulic rock drill to break the asphalt and concrete in the expansion joint slot and clean up the concrete fragments; (3) Correct the embedded expansion joint device connecting steel bars to ensure that their position and quantity meet the design requirements; (4) Hoist the expansion joint device into place, check whether its center line coincides with the center line of the beam joint, and whether its top surface is consistent with the road surface elevation, and make timely adjustments; (5) Weld and tie the expansion joint device and the embedded expansion joint device connecting steel bars to ensure that they are firm and reliable.

[0004] In the notch construction method, since the expansion joint connecting steel bars are already pre-embedded at the beam ends, the expansion joint installation can be carried out after cleaning the notch and confirming that the positioning and reserved dimensions of the pre-embedded bars meet the design requirements. However, because the expansion joint connecting steel bars are pre-embedded during the prefabrication of the beam segments, due to factors such as construction quality, it is difficult to ensure that the positioning and reserved dimensions of the pre-embedded bars meet the design requirements on site. This will have the following adverse effects on subsequent installation work: First, the welding points will not be aligned, affecting the anchoring strength of the expansion joint device. Second, the reserved dimensions will be insufficient, requiring the beam ends to be broken and re-embedded, increasing construction costs and affecting the quality of the beam. Third, the pre-embedded bars can be easily damaged during the notching process, affecting the quality of the subsequent expansion joint installation.

[0005] In addition, when constructing expansion joints using the slot construction method, due to errors in beam erection or prefabricated beam segments, the expansion joints at both beam ends often become misaligned or the reserved gaps in the expansion joints are too large or too small, which can hinder subsequent construction and affect construction progress. Summary of the Invention

[0006] In response to the above problems, the purpose of the present invention is to provide a method for constructing expansion joints based on cast-in-place lowering of the top slab at the end of a prefabricated T-beam, aiming to solve the problems of inaccurate positioning of embedded reinforcement and large dimensional errors in the traditional notch construction method, misalignment of the beam ends, and large dimensional errors in the reserved gaps of the expansion joints, which affect the construction of the expansion joints.

[0007] The present invention is achieved through the following technical solutions.

[0008] The method for constructing expansion joints based on the special-shaped post-casting of the top plate of the prefabricated T-beam end is characterized by comprising the following steps:

[0009] S1. Processing prefabricated T-beams

[0010] When processing the precast T-beam, the end top plate of the precast T-beam is lowered to below the original end top plate position to form an end notch at the original end top plate position, and at the same time, the top plate steel bars of the precast T-beam are extended into the end notch to form longitudinal connecting steel bars;

[0011] S2. Install prefabricated T-beams

[0012] S3. Construction of wet joints

[0013] S4, slot backfill

[0014] The concave grooves formed by the end notches of adjacent precast T-beams are fully covered with geotextiles, the geotextiles at the expansion joints are covered with steel plates, and the concave grooves are filled with backfill materials that meet the strength requirements for traffic.

[0015] S5. Bridge deck pavement

[0016] S6, construction of sealing plate

[0017] Remove the bridge deck pavement at the concave notch, clear the backfill material in the notch, dismantle the steel plate and geotextile, install the expansion joint device to connect the steel bars and the steel skeleton of the sealing plate, and cast the sealing plate in the end notch on both sides according to the design elevation of the expansion joint device;

[0018] S7. Install expansion joint device

[0019] After the sealing plate reaches the design strength, the expansion joint device is installed in the traditional way;

[0020] S8. Backfill and repair.

[0021] Preferably, in step S1, when processing the prefabricated T-beam, an isolation membrane is coated on the surface of the longitudinal connecting steel bars, and one end of the isolation membrane is pre-embedded in the top plate of the prefabricated T-beam.

[0022] Preferably, the isolation film is a plastic film or cellophane.

[0023] Preferably, in step S1, when processing the prefabricated T-beam, the thickness of the end top plate is 0.3-0.5 times the original thickness.

[0024] Preferably, in step S3:

[0025] For the wet joints of precast T-beams along the longitudinal bridge stagger, only the wet joints at the non-end notch positions are constructed, while the wet joints at the end notch positions are constructed simultaneously when the sealing plate is cast;

[0026] The wet joints in other locations are constructed in the normal way, and local lowering treatment is carried out simultaneously when the wet joints are poured to the end top plate.

[0027] Preferably, in step S4, the backfill material includes a concrete layer and a fine sand and gravel layer filled in sequence from bottom to top, the concrete layer is filled to a position 1-2 cm above the longitudinal connecting steel bars, and the fine sand and gravel layer is filled to the surface position of the prefabricated T-beam top plate.

[0028] Preferably, in step S4, after covering the steel plate, vertical positioning ribs are welded between one edge of the steel plate and the longitudinal connecting steel bars, and the upper ends of the vertical positioning ribs are located 1-2 cm above the longitudinal connecting steel bars.

[0029] Preferably, in step S6:

[0030] When pouring the sealing slab, if the precast T-beam is misaligned along the longitudinal direction of the bridge, resulting in the expansion joint gap not being straight, the following methods should be used to deal with it:

[0031] When the expansion joint gap is too large, lengthen the sealing plate cast on one or both sides of the expansion joint gap to reduce the width of the expansion joint gap;

[0032] When the expansion joint gap is too small, first break the excess concrete at the end of the precast T-beam on one or both sides of the expansion joint gap, and shorten the sealing plate cast on the corresponding side to increase the width of the expansion joint gap.

[0033] Preferably, in step S1, when processing the prefabricated T-beam, the web of the prefabricated T-beam is retracted.

[0034] Preferably, when the slot sealing plate is extended and cast, a diagonal support plate is cast at the armpit corner between the extended portion of the slot sealing plate and the lower web.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) In the present invention, the end top of the prefabricated T-beam is lowered to form an end notch, and the sealing plate is cast in place in the end notch, and the expansion joint device connecting steel bars are pre-embedded. Therefore, there is no need to pre-embed the expansion joint device connecting steel bars in advance when the prefabricated T-beam is processed. Compared with the traditional notch construction method, it has the following advantages: First, it avoids the problem of damaging the reserved steel bars when the notch is broken in the traditional method; second, when breaking the concrete in the notch, there is no need to worry about damaging the pre-embedded expansion joint device connecting steel bars, which speeds up the construction speed; third, when casting the sealing plate, the expansion joint device connecting steel bars can be accurately tied and welded to position, avoiding the problems of inaccurate positioning of the expansion joint device connecting steel bars and excessive dimensional errors, and enhancing the anchor connection quality between the expansion joint device and the steel bars.

[0037] 2) In the present invention, since the sealing plate is formed by cast-in-situ, and the connecting steel bars of the expansion joint device are pre-buried when the sealing plate is cast, compared with the traditional notch construction method, the present invention can lengthen or shorten the casting length of the sealing plate when casting the sealing plate to adjust the width of the expansion joint gap secondary, thereby being more flexible and coping with the situation where the error in the prefabrication or erection of the beam piece causes the misalignment and the expansion joint gap is not straight, so that the on-site construction can quickly solve the problem of the reserved gap between the two beams being too large or too small. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the three-dimensional structure of the prefabricated T-beam;

[0039] Figure 2 This is a schematic diagram of the main structure of the concave notch formed after the prefabricated T-beam is installed;

[0040] Figure 3 This is a schematic diagram of the main structure of laying geotextile and covering steel plate when backfilling the groove;

[0041] Figure 4 A top view of laying geotextile and covering steel plate when backfilling the trench;

[0042] Figure 5 Schematic diagram of filling the notch with backfill material and paving the bridge deck;

[0043] Figure 6 for Figure 5 A magnified schematic diagram of point A in the middle;

[0044] Figure 7 This is a schematic diagram of the main structure after removing the backfill material from the end groove during the construction of the sealing plate;

[0045] Figure 8 This is a top view of the construction wet joint;

[0046] Figure 9This is a top view of the sealing plate being lengthened when the expansion joint gap is too large;

[0047] Figure 10 To shorten the sealing plate when the expansion joint gap is too small;

[0048] Figure 11 for Figure 9 Cross-section at the middle BB;

[0049] Figure 12 for Figure 10 Cross-section at the middle CC;

[0050] Figure 13 This is a schematic diagram of the main structure after the expansion joint device is installed;

[0051] The meanings of the symbols in the above figure are: precast T-beam 1, end top plate 101, end notch 102, concave notch 103, longitudinal connecting steel bars 2, isolation membrane 201, steel plate 3, bridge deck pavement layer 4, geotextile 5, expansion joint device connecting steel bars 6, sealing plate steel skeleton 7, expansion joint gap 8, backfill material 9, concrete layer 901, fine sand and gravel layer 902, sealing plate 10, vertical locating bars 11, diagonal bracing plate 12, wet joint 13, expansion joint device 14, expansion joint gap control line 15, web 16, pier 17, excess concrete 18. DETAILED DESCRIPTION

[0052] The present invention will be further described below in the form of specific embodiments in conjunction with the accompanying drawings. It should be noted that the following embodiments are merely illustrative of the present invention in the form of examples, but the scope of protection of the present invention is not limited thereto. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0053] This embodiment provides a method for constructing expansion joints based on cast-in-place drop-down slabs at the ends of prefabricated T-beams. Figures 1 to 13 , which includes the following steps:

[0054] S1. Processing prefabricated T-beams

[0055] In this embodiment, the conventional prefabricated T-beam is improved in the following manner. For details, please refer to Figure 1 According to the construction position of the expansion joint, the top plate of the prefabricated T-beam 1 at the expansion joint notch position is cut according to the traditional notch construction method, that is, the end top plate 101 is lowered to below the original end top plate position to form an end notch 102 at the original end top plate position, and at the same time, the top plate steel bars of the prefabricated T-beam 1 are extended into the end notch 102 to form the longitudinal connecting steel bars 2;

[0056] Among them, after the position of the end top plate 101 is lowered, it mainly bears a certain degree of pressure and serves as the base plate for the subsequent casting of the sealing plate 10. Therefore, its plate thickness can be reduced to a certain extent. Specifically, the thickness h of the end top plate 101 is 0.3-0.5 times the original thickness. The longitudinal connecting steel bars 2 are provided for connecting with the sealing plate steel skeleton 7 to ensure the connection strength between the precast T-beam top plate and the sealing plate 10, and for connecting with the expansion joint device connecting steel bars 6.

[0057] As a further improvement of this embodiment, please refer to Figure 6 , an isolation membrane 201 can be coated on the surface of the longitudinal connecting steel bar 2. The isolation protection of the isolation membrane 201 can reduce the difficulty of cleaning the backfill material 9, so as to prevent the backfill material 9 from adhering to the longitudinal connecting steel bar 2 and affecting the quality of the welded connection between the longitudinal connecting steel bar 2 and the steel bar 6 of the expansion joint device and the sealing plate 10. In addition, one end of the isolation membrane 201 should be pre-buried in the top plate of the prefabricated T-beam 1 to prevent the isolation membrane 201 from falling off from the longitudinal connecting steel bar 2. Preferably, the isolation membrane 201 is a plastic film or cellophane.

[0058] As a further improvement to this embodiment, the web of the prefabricated T-beam can be retracted. In this way, when the sealing plate 10 needs to be shortened during the construction of the sealing plate in step S6, the volume of concrete to be removed can be reduced, thereby reducing construction costs and damage to the beam body.

[0059] In this embodiment, the specific processing steps of the prefabricated T-beam are as follows:

[0060] 1. Determine the relevant dimensions of the special-shaped top slab precast T-beam according to the bridge span, including conventional dimensions such as beam length, beam height, and top slab width. Determine the lowered height H and thickness h of the end top slab 101 based on the structural design requirements of the special-shaped top slab precast T-beam, the design requirements of the expansion joint device, and the embedded depth requirements of the subsequent expansion joint device connecting steel bars. Design the prestressing conditions and reinforcement of the precast beam in accordance with relevant design specifications.

[0061] 2. Process the precast T-beam in accordance with the order of bridge erection. The precast process of the precast T-beam is the same as the traditional method. However, since the end top plate 101 of the improved precast T-beam is lowered by H compared to the original top plate, and the thickness of the top plate after the plate is lowered is h, the mold required for the improved precast T-beam is different from that of the conventional precast T-beam. A specific template needs to be designed at the end top plate 101 to meet the requirements of pouring the end notch 102. That is, after the end top plates 101 on both sides are poured, a "trapezoidal" template is used to cover and fix between the end top plates 101, and then continue to pour to the top of the precast T-beam, and lead the top plate steel bars at the notch to form longitudinal connecting steel bars 2; due to special circumstances such as local plate lowering at the end after the beam piece is improved, attention should be paid to the prefabrication of the above-mentioned special parts and the protection of the finished product after pouring during the construction process;

[0062] S2. Install prefabricated T-beams

[0063] Install precast T-beams according to the bridge erection sequence. The installation method of precast T-beams is the same as the traditional method.

[0064] S3. Construction of wet joints

[0065] See also Figures 8-10 For the wet joints of the precast T-beams at the longitudinal bridge staggered locations, only the wet joints at the non-end notch 102 locations are constructed, and the wet joints at the end notch 102 locations are constructed simultaneously when the sealing plate 10 is cast; the wet joints at other locations are constructed in the normal manner, and local lowering treatment is performed when the wet joints are cast to the end top plate 101;

[0066] S4, slot backfill

[0067] See also Figures 2 to 4 , the concave groove 103 formed by the adjacent end grooves 102 of the adjacent prefabricated T beams is fully covered with geotextile 5, please refer to Figures 5 and 6 , a steel plate 3 with a width slightly larger than that of the expansion joint gap 8 is covered on the geotextile at the expansion joint gap 8, and a backfill material 9 with a strength that meets the traffic requirements is filled in the concave notch 103; in this step, by covering the steel plate 3 at the expansion joint gap 8 and filling the backfill material 9 in the concave notch 103, it is possible to ensure that the bridge deck has the conditions for the passage of large-scale construction machinery and equipment, and at the same time, it is possible to avoid the situation in the traditional method where the expansion joint position of the beam piece is uneven due to the protrusion of the embedded steel bars, and the damage of the embedded steel bars by driving; in addition, in this step, the full laying of the geotextile facilitates the subsequent cleaning of the backfill material 9 to prevent the backfill material 9 from adhering to the upper surface of the concave notch 103;

[0068] For details, please refer to Figures 5 and 6The backfill material 9 includes a concrete layer 901 and a fine sand and gravel layer 902 filled in sequence from bottom to top. The concrete layer 901 is filled to a position 1-2 cm above the longitudinal connecting steel bars 2, and the fine sand and gravel layer 902 is filled to the surface of the top plate of the prefabricated T-beam 1. Since the backfill material 9 is backfilled in layers, the fine sand and gravel layer 902 in the upper layer is convenient for later cleaning and can buffer the driving pressure on the bridge deck. The concrete layer 901 in the lower layer embeds and fixes the longitudinal connecting steel bars 2, which can prevent the longitudinal connecting steel bars 2 from shifting under pressure.

[0069] As a further improvement of this embodiment, please refer to Figures 3 to 6 After covering the steel plate 3, a vertical positioning rib 11 can be welded between the edge of one side of the steel plate 3 and the longitudinal connecting steel bar 2, and the upper end of the vertical positioning rib 11 is located 1-2 cm above the longitudinal connecting steel bar 2; by welding the vertical positioning rib 11, it can be ensured that the steel plate 3 will not shift after covering the expansion joint gap 8, so as to prevent the supporting function of the steel plate 3 from failing; secondly, the position of the longitudinal connecting steel bar 2 can be marked by the vertical positioning rib 11 to prevent the longitudinal connecting steel bar 2 from being damaged when the concrete layer 901 is subsequently removed; thirdly, the vertical positioning rib 11 can facilitate the control of the pouring thickness of the concrete layer 901.

[0070] S5. Bridge deck pavement

[0071] The bridge deck pavement was constructed using traditional methods according to the design requirements;

[0072] S6, construction of sealing plate

[0073] See also Figure 7 , break the bridge deck pavement 4 at the location of the concave notch 103, remove the backfill material 9 in the notch, remove the steel plate 3 and geotextile 5, install the expansion joint device connecting steel bars 6 and the sealing plate steel frame 7, and cast the sealing plate 10 in the end notches 102 on both sides according to the design elevation of the expansion joint device; when casting the sealing plate 10, if the precast T-beam is misaligned along the longitudinal direction of the bridge, resulting in the expansion joint gap 8 being not straight, the following method is adopted:

[0074] See also Figure 9 and Figure 11 When the expansion joint gap 8 is too large, the sealing plate 10 cast on one side or both sides of the expansion joint gap 8 is lengthened to the expansion joint gap control line 15 to reduce the width of the expansion joint gap 8; when the sealing plate 10 is lengthened, the diagonal brace plate 12 is cast at the armpit corner between the extended portion of the sealing plate 10 and the lower web, thereby enhancing the connection strength and stability between the end of the sealing plate 10 and the web; preferably, the cross-section of the diagonal brace plate 12 is triangular or trapezoidal;

[0075] See also Figure 10 and Figure 12When the expansion joint gap 8 is too small, first remove the excess concrete 18 at the end of the precast T-beam on one or both sides of the expansion joint gap 8, and shorten the sealing plate 10 cast on the corresponding side to the expansion joint gap control line 15, thereby increasing the width of the expansion joint gap 8;

[0076] In the present invention, since the sealing plate 10 is formed by cast-in-place, and the expansion joint device connecting steel bars 6 are pre-buried when casting the sealing plate 10, compared with the traditional slot construction method, the present invention can lengthen or shorten the casting length of the sealing plate 10 when casting the sealing plate 10 to adjust the width of the expansion joint gap 8 for the second time, thereby being more flexible and coping with the situation where the error in the prefabrication or erection of the beam piece causes the misalignment and the expansion joint gap 8 is not straight.

[0077] S7. Install expansion joint device

[0078] See also Figure 13 After the sealing plate 10 reaches the design strength, the expansion joint device 14 is installed in a conventional manner;

[0079] S8. Backfill and repair.

Claims

1. The expansion joint construction method based on the cast-in-place drop-down slab of the prefabricated T-beam end top slab is characterized by The steps include: S1. Processing prefabricated T-beams When processing the prefabricated T-beam, the end top plate (101) of the prefabricated T-beam (1) is lowered below the original end top plate position to form an end notch (102) at the original end top plate position, and at the same time, the top plate steel bars of the prefabricated T-beam (1) are extended into the end notch (102) to form longitudinal connecting steel bars (2); S2. Install prefabricated T-beams S3. Construction of wet joints S4, slot backfill A geotextile (5) is fully laid in a concave notch (103) formed adjacent to the end notches (102) of adjacent prefabricated T-beams, a steel plate (3) is covered on the geotextile at the location of the expansion joint gap (8), and a backfill material (9) having a strength that meets traffic requirements is filled in the concave notch (103); S5. Bridge deck pavement S6, construction of sealing plate The bridge deck pavement layer (4) at the location of the concave notch (103) is removed, the backfill material (9) in the notch is cleared, the steel plate (3) and the geotextile (5) are removed, the expansion joint device connecting the steel bars (6) and the sealing plate steel frame (7) are installed, and the sealing plates (10) are poured into the end notches (102) on both sides according to the design elevation of the expansion joint device; S7. Install expansion joint device After the sealing groove plate (10) reaches the design strength, the expansion joint device is installed in a conventional manner; S8. Backfill and repair.

2. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs according to claim 1 is characterized in that: In step S1, when processing the prefabricated T-beam, an isolation membrane (201) is coated on the surface of the longitudinal connecting steel bar (2), and one end of the isolation membrane (201) is pre-buried in the top plate of the prefabricated T-beam (1).

3. The expansion joint construction method based on cast-in-place drop-down of the top plate of the prefabricated T-beam end as claimed in claim 2 is characterized in that: The isolation film (201) is a plastic film or cellophane.

4. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs according to claim 1 is characterized in that: In step S1, when processing the prefabricated T-beam, the thickness of the end top plate (101) is 0.3-0.5 times the original thickness.

5. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs according to claim 1 is characterized in that: In step S3: For the wet joints of the precast T-beams along the longitudinal bridge staggered position, only the wet joints at the non-end notch (102) positions are constructed, and the wet joints at the end notch (102) positions are constructed simultaneously when the sealing plate (10) is cast; The wet joints at other locations are constructed in a normal manner, and local lowering is performed simultaneously when the wet joints are poured to the end top plate (101).

6. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs according to claim 1, characterized in that: In step S4, the backfill material (9) includes a concrete layer (901) and a fine sand and gravel layer (902) filled in sequence from bottom to top, the concrete layer (901) is filled to a position 1-2 cm above the longitudinal connecting steel bars (2), and the fine sand and gravel layer (902) is filled to the surface position of the top plate of the prefabricated T-beam (1).

7. The expansion joint construction method based on cast-in-place drop-down of the top plate at the end of prefabricated T-beams according to claim 6 is characterized in that: In step S4, after covering the steel plate (3), a vertical positioning rib (11) is welded between one side edge of the steel plate (3) and the longitudinal connecting steel bar (2), and the upper end of the vertical positioning rib (11) is located 1-2 cm above the longitudinal connecting steel bar (2).

8. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs according to claim 1, characterized in that: In step S6: When casting the sealing slab, if the precast T-beam is misaligned along the longitudinal direction of the bridge, resulting in the expansion joint gap (8) not being straight, the following method is adopted to deal with it: When the expansion joint gap (8) is too large, the sealing plate (10) cast on one side or both sides of the expansion joint gap (8) is lengthened to reduce the width of the expansion joint gap (8); When the expansion joint gap (8) is too small, the excess concrete at the end of the precast T-beam on one or both sides of the expansion joint gap (8) is first removed, and the sealing plate (10) cast on the corresponding side is shortened, thereby increasing the width of the expansion joint gap (8).

9. The expansion joint construction method based on cast-in-place drop-down of prefabricated T-beam end top slabs as claimed in claim 8, characterized in that: In step S1, when processing the prefabricated T-beam, the web of the prefabricated T-beam is retracted.

10. The expansion joint construction method based on cast-in-place drop-down of the top plate at the end of prefabricated T-beams according to claim 8, characterized in that: When the slot sealing plate (10) is extended and cast, the diagonal support plate (12) is cast at the armpit corner position between the extended portion of the slot sealing plate (10) and the lower web.

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