Beam piece formwork-free seamless construction method based on prefabricated bridge

Abstract

The invention discloses a beam piece formwork-free seamless construction method based on a prefabricated bridge, which is characterized by comprising the following steps: S1, beam piece design; s2, prefabricating the beam pieces: according to the number and the size of the beam pieces determined in the step S1, prefabricating the beam pieces in a factory in sequence according to the erection sequence of the beam pieces; s3, beam piece installation and adjustment, wherein the beam pieces prefabricated in the step S2 are transported to a construction site, and the beam pieces are sequentially installed on the bridge piers according to the beam piece combination form determined in the step S1 and the erection sequence of the beam pieces; s4, binding reinforcing steel bars; s5, space plugging and pouring; and S6, post-cast roof maintenance. Formwork-erecting construction of the wet joint is not needed, and a series of problems that due to wet joint construction, formwork installation is difficult, safety risks of objects falling from high altitudes exist, and the wet joint is prone to cracking and water seepage can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to a formwork-free and seamless construction method for beam segments based on a prefabricated assembled bridge. Background Art

[0002] Highway engineering, municipal road engineering and railway engineering generally involve bridge construction. With the maturity of bridge construction technology, the construction of small and medium span bridges is currently mostly prefabricated and assembled. The beams are prefabricated in the prefabrication yard, then transported to the site for hoisting construction using a bridge erection machine or crane, and then the reserved steel bars are welded or tied on site and concrete is poured to form a whole of multiple unconnected beams. Wet joints are important components for the transmission of force in prefabricated beam structures and are also weak points during use. Traditional wet joints are mostly 40 cm to 80 cm. Within this width range, steel bar tying or welding can meet the structural force requirements and ensure structural safety. However, sometimes due to the influence of the bridge width, some wet joints are less than 40 cm wide. At this time, steel bar tying cannot meet the structural force requirements. Before pouring wet joint concrete, it is usually necessary to support the bottom formwork. The tying or welding of wet joints and the support of formwork will greatly reduce the on-site construction speed, affect the appearance of wet joints, and fail to meet the requirements of rapid bridge construction.

[0003] In the prior art, there are several main methods for wet joint construction of prefabricated beams.

[0004] 1. Bracket fixing method. This method uses a full-frame bracket to support the reinforcement of the bottom membrane of the wet joint. The technical features of this solution are: the full-frame bracket is installed in the whole hole, which has high stability; the screw is arranged at a small spacing, which effectively prevents the deformation of the formwork, and the formwork is installed without bolt holes, the concrete appearance is good, and the overall leakage resistance of the bridge deck is good. Because workers can operate on the bracket, it is convenient to install and remove the formwork. There is no reinforced square wood on the bridge deck, and the bridge deck is clean, which is conducive to the height control, flatness and roughening of the bridge deck concrete; but because the height of each hole bridge from the ground is different, it is difficult to install and remove the bracket. The full-frame bracket, screw and steel bottom formwork can all be turned over, but the initial purchase of materials requires a large investment. Due to the obvious shortcomings of this method, it is currently basically in a state of elimination.

[0005] 2. Timber support method. This method is suitable for T-beam wet joint construction. With the help of the horseshoe part of the lower part of the T-beam, square timber is set between the two T-beams, and wooden boards are laid on top of the square timber to form a construction platform. Then, a bracket or a top support is used to tighten the wet joint bottom formwork for wet joint pouring. This method is simple to operate and has a fast construction progress, but it is difficult to set up square timber between the two T-beams and the construction safety is poor. Due to various reasons, the spacing between the two T-beams is quite different, and the turnover of square timber is poor. When reinforcing the formwork, it is not convenient to reinforce the formwork due to the small operating space.

[0006] 3. Suspension construction. The suspension construction of wet joints mainly fixes the bottom membrane by hanging, including bolt through-center tension fixing method and suspension support method. (1) Bolt through-center tension fixing method is to lay two steel pipes at a certain distance on the upper part of the precast beam, and erect them on two adjacent beams. The lower part of the bottom formwork is padded with square wood. The tie rod passes through the PVC sleeve, one side is connected to the bottom square wood, and the other side is connected to the beam surface steel pipe. The upper and lower parts are fastened with buckles. The contact points between the buckle and the square wood and the steel pipe are equipped with fastening steel gaskets. During construction, one or two tension screws can be set according to needs. After the wet joint concrete reaches the strength, the tie rod buckle is loosened, the tie rod is removed, and the bottom formwork, square wood and steel pipe are removed before the next wet joint construction. This construction method is simple in process and has a fast construction progress. No high-altitude work is required during construction, and the construction process is relatively safe. Because the formwork is fixed by bolts and square wood, it is not easy to leak slurry and concrete vibration sinking. However, this method also has major disadvantages: First, it has high requirements for the working performance of concrete, and the time for removing the formwork is greatly affected by environmental factors and is difficult to control. After the pouring is completed, before the formwork is removed, or even during the removal process, it is easy to be disturbed by external forces, forming cracks. Second, the formwork is usually used in a high turnover, the formwork is removed early, the insulation effect does not last long, and it is easy to form temperature cracks. Third, square timber and bolts are used to reinforce the formwork, and the amount of square timber and bolts is large; there are square timbers on the bridge deck to reinforce the formwork, the bridge deck is not clean, which is not conducive to the finishing and roughening of the bridge deck concrete; the bolt holes are not easy to seal, and the poor sealing of the bolt holes can easily cause bridge deck leakage; when the formwork is removed, the lower formwork cannot be fixed, and the bolts and nuts can only be unscrewed to let the formwork fall freely, which is easy to break the formwork and reduce the turnover of the formwork. (2) The suspension support method is to build a suspension bracket with hanging rods, and then lay the formwork on the bracket to form a construction platform, and lay a dense mesh to prevent debris from falling. The hanging rod is covered with a PVC sleeve so that the hanging rod can be pulled out after the concrete is poured. Use a cup-hook bracket to fix the formwork on the suspension bracket, or fix the wet joint bottom formwork by jacking. The suspension bracket can only be erected when there is less traffic, and the vehicles are temporarily diverted before the bracket is erected. The operation process of the suspension bracket is complicated, and it is a high-altitude operation, so the construction safety is poor. The holes for the hanging bars are not easy to block, and if the holes for the hanging bars are not tightly blocked, it is easy to cause water leakage on the bridge deck.

[0007] In addition to the conventional methods mentioned above, there are also some patents that disclose improved technical solutions related to the construction of wet joints of prefabricated beams: The Chinese invention patent with application number 202411146030.3 discloses an intelligent information-based rapid installation system and construction method for bridge wet joint formwork. It completes the lifting and tightening of the formwork through automatic control of intelligent information technology, and can move along the track after pouring. This technical solution can improve construction efficiency, reduce construction costs, and reduce labor input.

[0008] The Chinese invention patent with application number 202411102247.4 discloses a wet joint construction method for a box bottom plate. It also proposes a similar construction method, but it is fundamentally based on the suspension construction method. There are still some disadvantages of suspension construction, such as poor cleanliness of the bridge deck, which is not conducive to the plastering and roughening of the bridge deck concrete, and the complicated formwork removal process.

[0009] In order to solve the influence of the bracket and formwork on the wet joint construction and some shortcomings of the construction method, the Chinese invention patent with application number 202411117832.1 discloses a formwork assembly and construction method for the wet joint of the bridge over the existing line, which sets the bottom formwork and the top formwork through the embedded fixings of the precast beam flange plate, and the two formworks are connected by fixings. The bottom formwork, the top formwork and the side walls of the two adjacent flange plates are enclosed to form a wet joint post-casting strip, and the wet joint post-casting strip is suitable for being filled with concrete. The bottom formwork, the top formwork and the concrete are jointly constructed into a wet joint structure, and there is no need to remove the formwork, which is conducive to reducing the process, shortening the construction period and reducing the construction cost. Although this technical solution reduces some construction problems caused by the removal of the formwork to a certain extent, from the perspective of the content of the technical solution, it is more appropriate to use steel plates for the top formwork and the bottom formwork in actual construction, and the use of steel plates will lead to an increase in the cost of construction materials. In addition, during the construction of precast beams, the embedded fixings will affect the construction of precast beams to a certain extent. If steel plates are used, the connection between the bottom formwork and the fixings needs to be welded, but the prefabricated beam flange plates will reserve connecting steel bars, which will cover the lower fixings and the bottom formwork, making welding difficult and the welding quality difficult to guarantee.

[0010] The Chinese invention patent with application number 201810869717.8 discloses a U-shaped steel bar wet joint structure and construction method for bridge decks without bottom formwork. It proposes that the prefabricated bridge deck has a vertical V-shaped groove on the side at the joint, and the prefabricated bridge deck is hoisted on site using U-shaped steel bars. The bottom of adjacent prefabricated bridge decks extends horizontally to form a step structure, forming a closed bottom plate when assembled. Some prefabricated panels can be used as the bottom formwork of the wet joint. At the same time, the U-shaped steel bars are overlapped with each other, and the connection is strengthened by longitudinal steel bar binding. Leak-proof steel bars are placed in the V-shaped mouth at the lower end of the wet joint, and a wet joint with reliable connection is formed by pouring wet joint concrete in situ. The defect of this patent is that the prefabrication and installation accuracy at the construction site is difficult to guarantee. The contact between the two prefabricated beam top plates in the design structure will cause great difficulties in the hoisting process (this is also the original intention of reserving wet joint space in the structure), and even collisions will cause missing edges and corners, thereby losing the function of free formwork. In addition, the complex side shape of the precast beam top plate will increase the difficulty of the precast process, and vibration and demoulding will face difficulties. The concave slope makes it difficult to discharge bubbles during vibration, and the small-sized sharp corners are easy to bump during demoulding, resulting in missing edges and corners, and it is also difficult to roughen. The process defects caused by the complex structure will greatly weaken the strength of the joint surface between the precast beam top plate and the wet joint, posing a quality risk.

[0011] The Chinese invention patent with application number 202410614509.9 discloses a narrow wet joint structure and construction method that is conducive to rapid construction. It changes the shape of the flange plate and sets it as an arc-shaped bottom bracket with an opening upward. The bottom brackets are butted against each other and high-strength stop rubber is set at the butt joint. Transverse straight steel bars are pre-embedded in the top plate. The transverse steel bars relative to the precast beam are staggered and tied with longitudinal steel bars. After that, high-strength concrete is poured in the closed space formed by the arc-shaped bottom bracket of the flange plate to form a post-cast strip. This type of solution omits the formwork, and the narrow wet joint structure can be quickly constructed without setting U-shaped steel bars in the T-beam, setting bottom formwork, and welding. This patent is similar to the previous one. The groove or arc-shaped bottom support at the end of the flange plate and the high-strength grout-stopping belt docking to form a closed space requires very high prefabrication and installation accuracy. However, the construction accuracy is usually difficult to achieve during the actual construction of prefabricated beams. It is difficult to ensure that there will be no collision when two adjacent beams dock or the spatial accuracy after docking. Due to the grooves, arcs and other special-shaped structures at the end of the flange plate, the edge of the flange plate is thin, which is easily damaged by bumps during demoulding and hoisting. In addition, the complex interface is not easy to chisel, resulting in a weak interface at the wet joint. At the same time, high-strength concrete is required for the post-casting belt to ensure the strength of the structure, which will increase costs.

[0012] The Chinese invention patent with application number 202310008899.0 discloses a bridge wet joint structure and its construction method, which proposes to use prefabricated blocks embedded in the longitudinal wet joints between the flange plates of two adjacent T-beams. The prefabricated blocks are prefabricated in the prefabrication yard in advance, and the size of the prefabricated blocks is standardized and unified; the prefabricated blocks are used to fill the longitudinal wet joints to avoid installing formwork and tying steel bar structures in the longitudinal wet joints, thereby avoiding the problem of workers being lazy in tying steel bars. The defects of this patent include: First, the entire concrete prefabricated block is used instead of the wooden formwork as the bottom formwork, and the prefabricated block occupies most of the volume of the wet joint concrete, so the single block is heavy and short, which greatly increases the workload of the workers and easily creates safety risks of falling objects from high altitudes and waste of materials. Second, the adaptability of the prefabricated block to prefabrication and installation deviations is relatively enhanced, but a unified customization method is adopted for wet joints of the same size. Similarly, the thickness of the top plate is prone to deviations during the production of prefabricated beams, with some thick and some thin. Coupled with the influence of the transverse slope of the bridge deck, the adaptability of the inverted T-shaped prefabricated block to prefabrication and installation accuracy deviations is still insufficient to meet on-site needs. Third, the prefabricated blocks are finally grouting and pulled together into a whole through horizontal through holes. The material performance of the grouting material is much higher in compression than in tension, and the main form of force between the prefabricated blocks pulled together through through holes is tension. Conventional grouting materials cannot withstand this tension, and full-length steel bars or prestressed bars should be installed to meet the force requirements. However, the process of installing full-length steel bars after the assembly of this structure is complicated. Fourth, even if full-length steel bars are installed in the through holes, the steel bars cannot form an effective connection with the prefabricated blocks into a whole. On the contrary, there is ample room for movement in the through holes, and the tension of the full-length steel bars is difficult to be evenly transmitted to the prefabricated blocks. In fact, the tensile stress is still borne jointly by the full-length steel bars and the grouting material in the through holes, resulting in a huge waste of materials.

[0013] The Chinese invention patent with application number 202111565315.7 discloses a prefabricated assembled bridge deck structure and its construction method. It proposes to build a prefabricated connecting beam above the structural gap between two adjacent prefabricated beams and cover the structural gap. A number of vertical steel bars are reserved on the top surface of the prefabricated beam body, and the vertical steel bars are welded or tied to the transverse steel bars accordingly; a cast-in-place concrete layer is covered on the prefabricated beam body, prefabricated connecting beam, vertical steel bars and transverse steel bars. The defects of this technical solution are: first, it is equivalent to adding a cover plate on the top plate of the original prefabricated beam as a formwork-free bottom plate. This measure thickens the bridge deck pavement, which not only causes material waste but also increases the deadweight of the beam body and increases the permanent load of the structure. Second, the boss on which the cover plate is placed is concave, which also makes it difficult to discharge bubbles during vibration and easy to lose edges and corners during demolding.

[0014] Wet joints are important connection parts in precast concrete bridge structures, and their connection methods directly affect the structural stability and bearing capacity of the entire bridge. At present, the common wet joint construction methods in construction are suspension construction and various innovations based on suspension construction. However, no matter which existing construction method or the above-mentioned patented technical solution, they all do not bypass the installation of the wet joint bottom formwork, which leads to many problems in wet joint construction: First, the width of the wet joint is mostly 40 cm~80 cm, and at the same time, the edge of the prefabricated beam flange plate will reserve steel bars for the connection of adjacent beam pieces, which leads to a smaller gap between the beam pieces and difficulty in installing the formwork; second, when using the suspension method for construction, a large number of formworks, square wood or steel pipes need to be placed above the beam pieces, which leads to poor cleanliness of the bridge deck and is not conducive to the finishing and roughening of the bridge deck concrete; third, the suspension method construction requires the bottom formwork to be fixed by passing the tension screw or bolt through the wet joint area. Although the PVC sleeve can be passed through the area to be poured, the bolt hole is not tightly sealed after construction, which is easy to cause bridge deck leakage; fourth, when removing the formwork during the suspension method construction, the lower formwork cannot be fixed, and the bolts and nuts can only be unscrewed to let the formwork fall freely, which is easy to break the formwork, thereby reducing the turnover of the formwork. Summary of the invention

[0015] In view of the above problems, the purpose of the present invention is to provide a formwork-free and seamless construction method for beams of prefabricated assembled bridges, in which the beams are designed as conventional beams and thin plate short beams, and the assembly form of traditional beams is improved, and the flange plates of the thin plate short beams are staggered and connected with the lower parts of the flange plates of conventional beams on both adjacent sides, so that the top plate of the thin plate short beams can be used as a bottom formwork and enclosed with the flange plates of conventional beams on both adjacent sides to form a construction space for pouring the post-cast top plate, thereby eliminating the need for formwork to construct wet joints, and avoiding a series of problems such as difficulty in template installation caused by wet joint construction, safety risks of falling objects from high altitude, and easy cracking and water seepage in wet joints.

[0016] The present invention is achieved through the following technical solutions.

[0017] The method for constructing beams without formwork and without joints based on prefabricated assembled bridges is characterized by comprising the following steps: S1. Beam design: The beams include conventional beams and thin plate short beams. The beams are assembled and designed in the form of conventional beams, thin plate short beams, conventional beams, thin plate short beams, ..., conventional beams, thin plate short beams, and conventional beams, so that the thin plate short beams are always assembled between adjacent conventional beams, and the flange plates of the thin plate short beams are controlled to be staggered and connected with the flange plates of the adjacent conventional beams on both sides. The number of beams is determined according to the bridge design parameters. The beam size is designed according to the following requirements: H=h+H 1 + △h， in H For conventional beam height, H 1is the thickness of the flange plate end of a conventional beam, h For thin plates with short beams and high beams, △h is Flange plate clearance ,Right now The vertical distance between the upper surface of the thin plate short beam flange plate and the bottom edge of the conventional beam flange plate end at the offset connection between the thin plate short beam flange plate and the adjacent two sides conventional beam flange plates; S2, beam prefabrication: according to the number and size of beams determined in step S1, the beams are prefabricated in the factory in sequence according to the order of beam erection; when prefabricating conventional beams, flange plate steel bars are pre-embedded on both sides of the flange plates of conventional beams; when prefabricating thin plate short beams, U-shaped connecting steel bars are pre-embedded on the upper surface of the top plate of the thin plate short beams; S3, beam installation and adjustment: transport the beams prefabricated in step S2 to the construction site, and install the beams on the piers in the order of their erection according to the beam combination form determined in step S1, so that the thin plate short beams are always assembled between adjacent conventional beams, and the flange plates of the thin plate short beams are controlled to be staggered and connected with the flange plates of the adjacent conventional beams on both sides, and a gap distance between the flange plates is left. △h As the adjustment and activity space of the beam piece, the thin plate short beam top plate is used as the bottom formwork and is enclosed with the conventional beam flange plates on the adjacent two sides to form a construction space for pouring the post-cast top plate; S4, steel bar binding: connect transverse connecting steel bars across the top of the thin plate short beam between the flange plate steel bars of the adjacent conventional beams, and connect the transverse connecting steel bars to the U-shaped connecting steel bars, connect the longitudinal connecting steel bars on both sides of the U-shaped connecting steel bars, and connect the longitudinal connecting steel bars above the transverse connecting steel bars, so that the flange plate steel bars and the U-shaped connecting steel bars are connected into an integral structure through the transverse connecting steel bars and the longitudinal connecting steel bars; S5. Space blocking and pouring: After the reinforcement is tied, use a blocking agent to seal the flange between the flange plate of the thin plate short beam and the flange plate of the conventional beam on both sides. gap Blocking is done to avoid leakage when pouring the top slab, and then pouring is done with concrete of the same grade as the beams; S6. Maintenance of post-poured roof slab.

[0018] Preferably, in the beam design of step S1, the flange plate gap distance △h Controlled to 3~5 cm.

[0019] Preferably, in the beam design of step S1, the top plate thickness of the thin plate short beam is a Controlled to 5~8 cm.

[0020] Preferably, in the beam design of step S1, the flange plate offset distance is △L Controlled to 20~30 cm, flange plate gap distance △LThat is, the overlapping length of the thin plate short beam flange plate and the conventional beam flange plate at the offset connection below the thin plate short beam flange plate and the adjacent two sides conventional beam flange plates.

[0021] Preferably, in the beam prefabrication step S2, when prefabricating conventional beams, the ends of the flange plates of the conventional beams are prefabricated into tooth shapes, and the flange plate steel bars are pre-embedded in tooth blocks protruding from the toothed ends of the flange plates.

[0022] Preferably, in the step S2 of prefabricating the beam pieces, a splicing groove is reserved below the end of the conventional beam flange plate when prefabricating the conventional beam; in the step S3, the thin plate short beam flange plate is embedded in the splicing groove of the conventional beam flange plates on the adjacent two sides, so that the thin plate short beam flange plate is staggered and connected with the conventional beam flange plates on the adjacent two sides.

[0023] Preferably, in step S3, the distance between the end of the thin plate short beam flange plate and the side of the splicing notch is controlled b And the distance between the upper surface of the thin plate short beam flange and the top edge of the splicing notch c 3~5 cm.

[0024] Preferably, in step S2, the height of the U-shaped connecting steel bar is greater than the thickness of the post-cast top slab, so that after the post-cast top slab is cast, the exposed portion of the U-shaped connecting steel bar can be directly used as the pre-embedded hook bar for connecting the steel mesh of the cast-in-place layer of the bridge deck.

[0025] Preferably, in step S3, the beam pieces are installed in a sequence from the outer side beam to the inner side beam, from the inner side beam to the outer side beam, or from the middle to both sides.

[0026] Preferably, in step S5, the blocking agent is foam glue or polyurethane foaming agent.

[0027] Compared with the prior art, the beneficial effects of the present invention are: 1) The present invention makes simple improvements on the basis of traditional design, which has little impact on the construction process and can continue to use the more mature prefabricated beam construction process. However, through simple improvements, the conventional wet joint formwork casting is omitted, thus solving many process and quality problems involved in wet joint construction projects from the root.

[0028] 2) In the present invention, the top plate of the thin plate short beam can be regarded as the bottom formwork of the post-cast top plate. On the one hand, the step of installing the formwork is eliminated, simplifying the construction process. On the other hand, the post-cast structure will not be affected by gravity and cracks will be generated. It will also greatly reduce the disturbance of the surrounding environment changes and vehicle traffic to the post-cast structure, avoiding quality problems such as cracks and water leakage.

[0029] 3) During the construction process of the present invention, there is no need to support the formwork at the bottom of the beam, and there are no holes on the bridge deck, which largely ensures the safety of the bridge deck construction and reduces the risk of falling objects from high altitudes during cross-line construction.

[0030] 4) In the present invention, the post-cast top plate has a smooth surface and a simple shape, which is friendly to processes such as pouring, vibrating, demoulding, and roughening, and will not cause additional quality risks.

[0031] 5) In the present invention, U-shaped connecting steel bars are embedded in the top plate of the thin plate low beam, and their length needs to exceed the top surface of the post-cast top plate. After the post-cast top plate is cast, the exposed part can be directly used as the embedded hook bar for connecting the steel mesh of the cast-in-place layer of the bridge deck; the steel bar structure is not complicated, but takes into account the connection and force requirements of various aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a main structural diagram of the beam piece formwork-free and seamless construction method of the present invention; Figure 2 for Figure 1 The enlarged schematic diagram of point A in the middle; Figure 3 It is a top view structural diagram of the beam piece formwork-free and seamless construction method of the present invention; Figure 4 for Figure 3 The enlarged schematic diagram of point B in the middle; Figure 5 This is the main structural diagram of a conventional beam; Figure 6 This is the main structural diagram of the thin plate short beam; Figure 7 This is the main structural view of the staggered connection between the flange plate of the thin plate short beam and the flange plate of the adjacent conventional beam on one side; Figure 8 It is a schematic diagram of the installation of beam pieces from the middle to both sides; Fig. 9 It is a main structural diagram of the beam piece formwork-free and seamless construction method of the present invention when setting the splicing notch; Fig.10 The main structural diagram of the staggered connection between the thin plate short beam flange plate and the adjacent conventional beam flange plate at the bottom when setting the splicing notch; The meanings of the symbols in the above figure are: pier 1, conventional beam 2, thin plate short beam 3, flange plate reinforcement 4, U-shaped connecting reinforcement 5, transverse connecting reinforcement 6, longitudinal connecting reinforcement 7, tooth block 7, post-cast top plate 8, tooth block 9, splicing groove 10, plugging agent 11, flange plate 12, top plate 13. DETAILED DESCRIPTION

[0033] The present invention is further described in the form of specific embodiments in conjunction with the accompanying drawings. It should be pointed out that the following implementation modes are only illustrative descriptions of the present invention in the form of examples, but the protection scope of the present invention is not limited thereto. The described embodiments 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 creative work are within the scope of protection of the present invention. Example 1

[0034] This embodiment provides a method for constructing beams without formwork and without joints based on a prefabricated assembled bridge. Figures 1 to 8 , which comprises the following steps: S1. Beam design like Figure 1 , Figure 3 and Figure 7 As shown, the beam piece includes a conventional beam 2 and a thin plate short beam 3; the beam piece is assembled and designed in the combination form of conventional beam, thin plate short beam, conventional beam, thin plate short beam, ..., conventional beam, thin plate short beam, conventional beam, so that the thin plate short beam 2 is always assembled between adjacent conventional beams 3, and the flange plate 12 of the thin plate short beam is controlled to be staggered and connected with the flange plates 12 of the adjacent conventional beams on both sides; like Figure 7 As shown, in order to enable the beam pieces to be assembled in the above-mentioned combination form, the beam piece size in the present invention should meet the following requirements: H=h+H 1 + △h， in H For conventional beam height, H 1 is the thickness of the flange plate end of a conventional beam, h For thin plates with short beams and high beams, △h is Flange plate clearance ， Flange plate clearance Right now The vertical distance between the upper surface of the thin plate short beam flange plate and the bottom edge of the conventional beam flange plate end at the offset connection between the thin plate short beam flange plate and the adjacent two sides of the conventional beam flange plate; Based on the above beam size design, taking the conventional beam as a T beam as an example, the thin plate short beam in the present invention can be based on the conventional beam, and the following improvements are made without changing the thickness of the bottom plate and web of the conventional beam: One is to reduce the web height to form a height difference with the conventional beam to ensure that the thin plate short beam flange plate can be offset and connected with the lower flange plates of the adjacent conventional beams on both sides; when designing the height, it is necessary to consider setting a suitable flange gap distance. △h , to ensure that the beam has enough space for position adjustment, but the gap distance between the flange plate △h is not suitable Too large, otherwise it will make it difficult to block the top slab when pouring it, and the gap between the flange plates △hIt can be comprehensively considered based on the actual process accuracy level on site. Usually, the flange plate gap distance △h Controlled to 3~5 cm; The second is to reduce the thickness of the top plate. Since the top plate 13 of the thin plate short beam can be regarded as the bottom template of the post-cast top plate 8, its thickness does not need to be too thick. The specific thickness can be comprehensively considered according to the actual situation of the bridge span, prefabricated beam height, etc. a Controlled to 5~8 cm; The third is to increase the width of the top plate. Since the top plate 13 of the thin plate short beam is used as the bottom template of the post-cast top plate 8, a suitable flange plate offset distance needs to be set. △L , so that the thin plate short beam flange plate and the conventional beam flange plate partially overlap; wherein the flange plate offset distance △L That is, the overlapping length of the thin plate short beam flange plate and the conventional beam flange plate at the offset connection below the thin plate short beam flange plate and the adjacent two sides of the conventional beam flange plate; usually the flange plate offset distance △L Controlled to 20~30 cm; The number of beams is determined according to the design parameters of the bridge. Specifically, since the thin plate short beam 3 is always assembled between adjacent conventional beams 2, that is, the thin plate short beam can only be located at the middle beam position, the construction method of the present invention can only be used for an odd number of beams. The number of beams can usually be determined according to the design width of the bridge deck, generally 5 or 7. According to the design practice, Figure 1 As shown, the conventional line section has 5 pieces, and the beam piece combination form is conventional beam, thin plate short beam, conventional beam, thin plate short beam, conventional beam; the curved section or bifurcated intersection has 7 pieces, and the beam piece combination form is conventional beam, thin plate short beam, conventional beam, thin plate short beam, conventional beam, thin plate short beam, conventional beam; S2. Beam prefabrication According to the number and size of the beam pieces determined in step S1, the beam pieces are prefabricated in sequence in the factory according to the order in which the beam pieces are erected; See also Figure 5 When prefabricating a conventional beam, flange plate steel bars 4 are pre-embedded on both sides of the conventional beam flange plate, and the flange plate steel bars 4 are designed as a traditional reserved steel bar structure; in addition, in order to increase the connection strength between the post-cast top plate 8 and the conventional beam 2, the ends of the conventional beam flange plates are prefabricated into teeth, and the flange plate steel bars are pre-embedded in the tooth blocks 9 protruding from the toothed ends of the flange plates; See also Figure 6When prefabricating the thin plate short beam, a U-shaped connecting steel bar 5 is embedded on the upper surface of the top plate of the thin plate short beam, and the height of the U-shaped connecting steel bar 5 is greater than the thickness of the post-cast top plate 8, so that after the post-cast top plate 8 is cast, the exposed part of the U-shaped connecting steel bar 5 is directly used as the pre-embedded hook bar for connecting the steel mesh of the cast-in-place layer of the bridge deck; since the thin plate short beam is staggered and located below the conventional beam, the end of its flange plate does not need to be connected, so the end embedded steel bar can be cancelled. When the top plate of the thin plate short beam is prefabricated, due to the change in thickness, it is only necessary to design the top plate steel bar according to the thin plate structural requirements; S3. Beam installation and adjustment The prefabricated beams in step S2 are transported to the construction site and stored in the beam storage area. Since the top plate of the thin plate short beam is relatively thin, it is best not to stack them during storage. In addition, attention should be paid to the protection of the finished products during transportation to avoid damage to the weak corners; please refer to Figure 8 Then, according to the beam piece combination form determined in step S1, the beam pieces are installed on the pier 1 in sequence according to their erection order, so that the thin plate short beam 3 is always assembled between the adjacent conventional beams 2, and the flange plates of the thin plate short beam 3 are controlled to be staggered and connected with the flange plates of the adjacent conventional beams 2 on both sides, and a gap distance between the flange plates is left. △h As the adjustment and activity space of the beam piece, the top plate 13 of the thin plate short beam can be used as the bottom template and enclosed with the flange plates 12 of the conventional beams on both sides to form a construction space for pouring the post-cast top plate; due to the height difference between the thin plate short beam and the conventional beam, in order to ensure the installation of the thin plate short beam, the beam piece needs to be installed in a certain order, which can be installed from the outer edge beam to the inner edge beam, from the inner edge beam to the outer edge beam or from the middle to both sides; Figure 8 It shows the process of erecting the beam from the middle to both sides; S4. Steel bar binding In addition to pre-embedded flange plate steel bars and U-shaped connecting steel bars during beam prefabrication, the present invention also requires installation of transverse connecting steel bars 6 and longitudinal connecting steel bars 7 to ensure the overall connection strength between the beams. For details, please refer to Figure 2 and Figure 4 , connect the transverse connecting steel bar 6 across the top of the thin plate short beam between the flange plate steel bars 4 of the adjacent conventional beams, and connect the transverse connecting steel bar 6 to the U-shaped connecting steel bar 5; connect the longitudinal connecting steel bars 7 on both sides of the U-shaped connecting steel bar 5, and connect the longitudinal connecting steel bar 7 to the top of the transverse connecting steel bar 6, so that the flange plate steel bars and the U-shaped connecting steel bars are connected to form an integral structure through the transverse connecting steel bars and the longitudinal connecting steel bars in the construction space enclosed by the top plate of the thin plate short beam and the flange plates of the conventional beams on both sides; wherein, the connection points or the intersections of the steel bars between the flange plate steel bars, the U-shaped connecting steel bars, the transverse connecting steel bars and the longitudinal connecting steel bars are welded or tied, and the lap length is designed according to the requirements of the specification; S5. Space blocking and pouring See also Figure 1After the steel bars are tied, foam glue or polyurethane foaming agent is used as a sealing agent 11 to seal the flange plate of the thin plate short beam and the flange plate of the conventional beam on both sides. gap Block to avoid leakage when pouring the post-cast top slab, and then pour with concrete of the same grade as the beam, vibrating it into place during pouring; after the post-cast top slab is poured, its thickness l=H 1 + △h, which is greater than Conventional beam flange plate end thickness H 1 ; S6. Maintenance of post-poured roof slab.

[0035] After pouring is completed, timely covering and curing should be carried out to prevent cracks in the later poured top slab. Example 2

[0036] This embodiment provides a method for constructing beams of prefabricated and assembled bridges without formwork and without joints. The method adopts the construction method of embodiment 1, but makes the following improvements on the basis of embodiment 1: Fig. 9 and Fig.10 In step S2, during the prefabrication of the beam pieces, a splicing notch is reserved below the end of the conventional beam flange plate when prefabricating the conventional beam; in step S3, the thin plate short beam flange plate is embedded in the splicing notch of the conventional beam flange plates on both sides, so that the thin plate short beam flange plate is staggered and connected with the lower side of the conventional beam flange plates on both sides, and the distance between the end of the thin plate short beam flange plate and the side of the splicing notch is b And the distance between the upper surface of the thin plate short beam flange and the top edge of the splicing notch c It needs to be determined based on comprehensive consideration of beam prefabrication accuracy and installation technology. To make There is enough space for installation and adjustment when installing the beam. b , c The value is 3~5 cm; in this case, the distance between the upper surface of the thin plate short beam flange and the top edge of the splicing notch is c Equivalent to flange plate clearance distance △h , and the conventional beam height H 、Thin plate low beam high beam h , flange plate end thickness H 1 , the distance between the upper surface of the thin plate short beam flange and the top edge of the splicing notch c The following relationship exists: H=h+H 1 + c； In addition, due to the presence of the conventional beam flange end joint notch, the flange end thickness H 1 Become smaller, Then the thickness of the top plate is l=H 1 + c, so the thickness of the post-cast top slab also becomes smaller;At the same time, due to the existence of the splicing notch, the flange plate interface suddenly changes, which makes the flange plate have a certain unfavorable stress condition. In order to ensure the stress of the flange plate, the thickness of the flange plate end is H 1 With notch depth H 2 There should be a certain proportional relationship between them, that is, H 1 = k 2 , where the proportionality coefficient k It can be determined by mechanical analysis methods such as finite element analysis.

[0037] Based on the improvements of this embodiment, firstly, the thickness of the post-cast top slab can be greatly reduced to reduce the construction cost; secondly, the thin plate short beam flange plate is embedded in the splicing groove of the conventional beam flange plate on the adjacent two sides, thereby enhancing the connection strength between the thin plate short beam, the conventional beam and the post-cast top slab.

Claims

1. A method for constructing beams without formwork and without joints based on prefabricated assembled bridges, characterized in that: The steps include: S1. Beam design: beams include conventional beams and thin plate short beams. The beams are assembled and designed in the form of conventional beams, thin plate short beams, conventional beams, thin plate short beams, ..., conventional beams, thin plate short beams, and conventional beams, so that the thin plate short beams are always assembled between adjacent conventional beams, and the flange plates of the thin plate short beams are staggered and connected with the flange plates of the adjacent conventional beams on both sides. The number of beams is determined according to the bridge design parameters. The beam size is designed according to the following requirements: H=h+H 1 + △h， in H For conventional beam height, H 1 is the thickness of the flange plate end of a conventional beam, h For thin plates with short beams and high beams, △h is Flange plate clearance ， Flange plate clearance Right now The vertical distance between the upper surface of the flange plate of the thin plate short beam and the bottom edge of the flange plate end of the conventional beam at the offset connection between the flange plate of the thin plate short beam and the flange plate of the adjacent conventional beams on both sides; S2, beam prefabrication: according to the number and size of beams determined in step S1, the beams are prefabricated in the factory in sequence according to the order of beam erection; when prefabricating conventional beams, flange plate steel bars are pre-embedded on both sides of the flange plates of the conventional beams; when prefabricating thin plate short beams, U-shaped connecting steel bars are pre-embedded on the upper surface of the top plate of the thin plate short beams; S3, beam installation and adjustment: transport the beams prefabricated in step S2 to the construction site, and install the beams on the piers in the order of their erection according to the beam combination form determined in step S1, so that the thin plate short beam is always assembled between adjacent conventional beams, and the flange plates of the thin plate short beam are controlled to be staggered and connected with the flange plates of the adjacent conventional beams on both sides, and a gap distance between the flange plates is left. △h As the adjustment and activity space of the beam piece, the top plate of the thin plate short beam can be used as the bottom formwork and enclosed with the flange plates of the conventional beams on both sides to form a construction space for pouring the post-cast top plate; S4, steel bar binding: connect transverse connecting steel bars across the top of the thin plate short beam between the flange plate steel bars of the adjacent conventional beams, and connect the transverse connecting steel bars to the U-shaped connecting steel bars, connect the longitudinal connecting steel bars on both sides of the U-shaped connecting steel bars, and connect the longitudinal connecting steel bars above the transverse connecting steel bars, so that the flange plate steel bars and the U-shaped connecting steel bars are connected into an integral structure through the transverse connecting steel bars and the longitudinal connecting steel bars; S5. Space blocking and pouring: After the reinforcement is tied, use the blocking agent to seal the flange between the flange plate of the thin plate short beam and the flange plate of the conventional beam on both sides. gap Carry out plugging to avoid leakage when pouring the top slab, and then pour with concrete of the same grade as the beam; S6. Maintenance of post-poured roof slab.

2. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In the step S1 beam design, the flange plate gap distance △h Controlled to 3~5 cm.

3. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In the beam design of step S1, the top plate thickness of the thin plate short beam is a Controlled to 5~8 cm.

4. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In the step S1 beam design, the flange plate offset distance △L Controlled to 20~30 cm, flange plate gap distance △L That is, the overlapping length of the thin plate short beam flange plate and the conventional beam flange plate at the offset connection below the thin plate short beam flange plate and the adjacent two sides conventional beam flange plates.

5. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In the beam prefabrication step S2, when prefabricating conventional beams, the ends of the flange plates of the conventional beams are prefabricated into tooth shapes, and the flange plate steel bars are pre-embedded in the tooth blocks protruding from the tooth-shaped ends of the flange plates.

6. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 5, characterized in that: In the step S2, during the prefabrication of the beam pieces, a splicing notch is reserved below the end of the conventional beam flange plate when prefabricating the conventional beam; in the step S3, the thin plate short beam flange plate is embedded in the splicing notch of the conventional beam flange plates on the adjacent two sides, so that the thin plate short beam flange plate is staggered and connected with the lower side of the conventional beam flange plates on the adjacent two sides.

7. The method for constructing beams without formwork and without joints based on a prefabricated assembled bridge according to claim 6, characterized in that: In step S3, the distance between the end of the thin plate short beam flange plate and the side of the splicing notch is controlled. b And the distance between the upper surface of the thin plate short beam flange and the top edge of the splicing notch c All are 3~5 cm.

8. The method for constructing beams without formwork and without joints based on a prefabricated assembled bridge according to claim 1, characterized in that: In step S2, the height of the U-shaped connecting steel bar is greater than the thickness of the post-cast top slab, so that after the post-cast top slab is cast, the exposed portion of the U-shaped connecting steel bar can be directly used as the pre-embedded hook bar for connecting the steel mesh of the cast-in-place layer of the bridge deck.

9. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In step S3, the beam pieces are installed in a sequence of from the outer side beam to the inner side beam, from the inner side beam to the outer side beam, or from the middle to both sides.

10. The method for constructing beams without formwork and without joints based on prefabricated assembled bridges according to claim 1, characterized in that: In the step S5, the blocking agent is foam glue or polyurethane foaming agent.

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