Formwork-free seamless beam piece structure for post-pouring of top plate

Abstract

The utility model discloses a roof post-cast formwork-free seamless beam piece structure which is characterized by comprising conventional beams which are uniformly erected on a pier at intervals, flange plate steel bars which are pre-buried on two sides of a flange plate of each conventional beam, and thin plate short beams which are erected on the pier and are arranged between adjacent conventional beams, the U-shaped connecting steel bars are embedded in the upper surfaces of top plates of the thin-plate short beams, the transverse connecting steel bars stretch across the upper portions of the thin-plate short beams and are connected between opposite flange plate steel bars of the adjacent conventional beams, and the longitudinal connecting steel bars abut against the two sides of the U-shaped connecting steel bars and are connected with the transverse connecting steel bars. According to the beam piece structure, a formwork does not need to be erected for construction of wet joints, and a series of problems that due to wet joint construction, formworks are difficult to install, safety risks of objects falling from high altitudes exist, and the wet joints are prone to cracking and water seepage can be solved.

Description

Technical Field

[0001] This utility model belongs to the field of bridge construction technology, specifically relating to a formwork-free, jointless beam structure with a post-cast top slab. Background Technology

[0002] Highway engineering, municipal road engineering, and railway engineering commonly involve bridge construction. With the maturity of bridge construction technology, prefabrication is now widely used for small and medium-span bridges. Beams are prefabricated in a prefabrication yard, then transported to the site for installation using bridge erecting machines or cranes. Pre-installed reinforcing bars are then welded or tied on-site, and concrete is poured to integrate multiple unconnected beams into a single structure. Wet joints are crucial for load transfer in prefabricated beam structures and are also weak points during use. Traditionally, wet joints are typically 40cm to 80cm wide. Within this width, rebar tying or welding can meet structural load requirements and ensure structural safety. However, sometimes, due to bridge width constraints, some wet joints are less than 40cm wide, making rebar tying insufficient for structural load requirements. Before pouring concrete at the wet joint, a bottom formwork is usually required. The tying or welding of wet joints and the erection of formwork significantly reduce on-site construction speed, affect the appearance of the wet joints, and fail to meet the requirements for rapid bridge construction.

[0003] In existing technologies, the main methods for constructing wet joints in precast beams are as follows.

[0004] I. Scaffolding Fixing Method. This method uses a full-span scaffolding system to reinforce the bottom membrane of the wet joint. The technical features of this method are: the full-span scaffolding is erected across the entire span, resulting in high stability; the small spacing of the screw rods effectively prevents formwork deformation; and the absence of bolt holes in the formwork installation leads to a better concrete appearance and better overall leak-proof performance of the bridge deck. Workers can operate on the scaffolding, facilitating formwork installation and removal. The absence of reinforcing timber on the bridge deck keeps it clean, which is beneficial for controlling the height of the concrete, the smoothness of the finish, and roughening. However, due to the varying heights of each span from the ground, scaffolding installation and removal are difficult. While the full-span scaffolding, screw rods, and steel bottom formwork are all reusable, the initial material investment is large. Due to these significant drawbacks, this method is now largely obsolete.

[0005] II. Timber Support Method. This method is suitable for the construction of wet joints in T-beams. Using the lower horseshoe-shaped section of the T-beam, square timber is erected between the two T-beams. Wooden planks are then laid on top of the timber to form a construction platform. Afterwards, supports or top braces are used to tighten the bottom formwork of the wet joint before pouring the wet joint. This method is simple to operate and has a relatively fast construction progress. However, erecting square timber between the two T-beams is difficult and has poor construction safety. Due to various reasons, the spacing between the two T-beams varies greatly, resulting in poor timber turnover. When reinforcing the formwork, the limited operating space makes formwork reinforcement inconvenient.

[0006] III. Suspension Construction. The suspension construction of wet joints is mainly to fix the bottom formwork by suspension, including the bolt through-core tie fixing method and the suspension support method. (1) The bolt through-core tie fixing method is to lay two steel pipes at certain intervals on the upper part of the precast beam and erect them on the two adjacent beams. Square timber is added to the bottom of the bottom formwork. The tie rod passes through the PVC sleeve, one side is connected to the bottom square timber, and the other side is connected to the steel pipe on the beam surface. Both the upper and lower parts are fastened with buckles. The contact points between the buckles and the square timber and steel pipes are equipped with steel shims for fastening. One or two tie rods can be set as needed during construction. After the wet joint concrete reaches the strength, the tie rod buckles are loosened, the tie rods are removed, and the bottom formwork, square timber and steel pipes are removed before the construction of the next wet joint is carried out. This construction method is simple and the construction progress is fast. No high-altitude operation is required during construction, and the construction process is relatively safe. Because the formwork is fixed firmly by bolts and square timber, it is not easy to produce grout leakage and concrete vibration sinking phenomenon. However, this method also has significant drawbacks: First, it requires high performance of concrete, and the formwork removal time is greatly affected by environmental factors and is difficult to control. After pouring, before the formwork is removed, or even during the removal process, it is easily disturbed by external forces, which can cause cracks. Second, the formwork is usually used with high turnover, and the formwork removal time is early. The insulation effect does not last long and temperature cracks are easily formed. Third, the formwork is reinforced with square timber and bolts, and the amount of square timber and bolts used is large. There are square timbers reinforced with formwork on the bridge deck, which makes the bridge deck less clean and is not conducive to the finishing and roughening of the bridge deck concrete. The bolt holes are not easy to seal, and the bolt holes are not sealed tightly, which can easily cause water leakage on the bridge deck. When the formwork is removed, the lower formwork cannot be fixed. The bolts and nuts can only be loosened to let the formwork fall freely, which can easily damage the formwork and reduce the number of times the formwork can be reused. (2) The suspension support method is to erect a suspension support by using suspension rods, and then lay the formwork on the support to form a construction platform and lay a dense mesh net to prevent debris from falling. The suspension rods are covered with PVC sleeves so that the suspension rods can be pulled out after the concrete is poured. The formwork is fixed to the suspended scaffold using cup-type brackets, or the bottom formwork of the wet joint is fixed using top supports. Suspended scaffolding can only be erected during periods of low traffic volume, after temporarily diverting traffic. The operation of suspended scaffolding is complex, involves working at height, and has poor construction safety. The holes for the suspension rods are difficult to seal, and inadequate sealing can easily lead to water leakage from the bridge deck.

[0007] In addition to the conventional methods mentioned above, some patents disclose improved technical solutions related to the construction of wet joints in precast beams:

[0008] Chinese invention patent application number 202411146030.3 discloses a smart information-based rapid installation system and construction method for bridge wet joint formwork. Through smart information-based automatic control, the formwork can be lifted and tightened. After pouring, it can be moved along the track. This technical solution can improve construction efficiency, reduce construction costs, and reduce labor input.

[0009] Chinese invention patent application number 202411102247.4 discloses a construction method for wet joints of the bottom plate of a caisson. It also proposes a similar construction method, but it is fundamentally based on the suspension method. It still has some disadvantages of suspension construction, such as poor bridge deck cleanliness, which is not conducive to the finishing and roughening of the bridge deck concrete, as well as the complexity of the formwork removal process.

[0010] To address the impact of supports and formwork on wet joint construction and some shortcomings of existing construction methods, Chinese invention patent application number 202411117832.1 discloses a formwork assembly and construction method for wet joints of bridges crossing existing railway lines. This method uses pre-embedded fasteners on the flange plates of precast beams to set up bottom and top formwork. The two formworks are connected by fasteners, and the bottom and top formworks, along with the side walls of two adjacent flange plates, enclose a wet joint post-pouring strip. The post-pouring strip is suitable for filling with concrete. The bottom and top formworks, together with the concrete, constitute the wet joint structure, eliminating the need for formwork removal, thus reducing procedures, shortening the construction period, and lowering construction costs. While this technical solution reduces some construction problems caused by formwork removal to a certain extent, the technical solution suggests that steel plates are more suitable for the top and bottom formwork in actual construction. However, using steel plates increases the cost of construction materials. Furthermore, the pre-embedded fasteners can affect the construction of precast beams to some extent. If steel plates are used, the connection between the bottom formwork and the fasteners needs to be welded. However, the precast beam flanges will have pre-reserved connecting steel bars, which will obstruct the lower fasteners and the bottom formwork, making welding difficult and the welding quality hard to guarantee.

[0011] Chinese invention patent application number 201810869717.8 discloses a formwork-free U-shaped steel bar wet joint structure and construction method for bridge decks. It proposes that precast bridge decks have a vertical V-shaped groove on the side of the joint. The precast bridge decks are hoisted on-site using U-shaped steel bars. Adjacent precast bridge decks have horizontally extended steps at their bottoms, forming a closed bottom plate during assembly. Part of the precast slab can serve as the bottom formwork for the wet joint. Simultaneously, the U-shaped steel bars overlap and are reinforced with longitudinal steel bars. Leak-proof steel bars are placed in the V-shaped opening at the lower end of the wet joint. The wet joint is then formed by pouring concrete, creating a reliably connected wet joint. The patent's drawback lies in the difficulty of guaranteeing the precast and installation accuracy on-site. The design structure's design, where the top slabs of two precast beams come into contact, can cause significant difficulties during hoisting (which is the original intention of reserving space for the wet joint in the structure), and may even result in chipped edges or corners, thus losing the formwork-free function. Furthermore, the complex side shape of the precast beam top slab increases the difficulty of the precast process, making vibration and demolding challenging. The concave slope makes it difficult for air bubbles to escape during vibration, and the small sharp corners are prone to damage during demolding, resulting in chipped edges and corners. Additionally, roughening the surface is difficult. These complex structural defects significantly weaken the strength of the bond between the precast beam top slab and the wet joint, creating potential quality risks.

[0012] Chinese invention patent application number 202410614509.9 discloses a narrow wet joint structure and construction method that facilitates rapid construction. It modifies the shape of the flange plate, setting it as an upward-opening arc-shaped base support. The base supports are interlocked, with high-strength grout-stopping rubber installed at the joint. Transverse straight steel bars are pre-embedded in the top plate, and the transverse steel bars relative to the precast beam interweave and are tied together with longitudinal steel bars. Then, high-strength concrete is poured into the closed space formed by the arc-shaped base support of the flange plate to form a post-cast strip. This type of solution eliminates the need for formwork; the narrow wet joint structure can be constructed rapidly without the need for U-shaped steel bars in the T-beam, without the need for bottom formwork, and without welding. Similar to the previous patent, this patent requires extremely high prefabrication and installation precision to connect the grooves or arc-shaped supports at the ends of the flange plates with the high-strength grout-stopping strips to form a closed space. However, in actual prefabrication beam construction, achieving the required precision is often difficult, making it hard to guarantee that adjacent beams will not collide or that the space will remain accurate after connection. Furthermore, the irregular shapes such as grooves and arcs at the ends of the flange plates result in thinner edges, making them susceptible to damage during demolding and hoisting. The complex interfaces also make roughening difficult, leading to weak interfaces at wet joints. Additionally, the post-cast strips require high-strength concrete to ensure structural strength, increasing costs.

[0013] Chinese invention patent application number 202310008899.0 discloses a bridge wet joint structure and its construction method. It proposes using precast blocks embedded in the longitudinal wet joint between the flanges of two adjacent T-beams. The precast blocks are prefabricated in a prefabrication yard, and their dimensions are standardized. By filling the longitudinal wet joint with precast blocks, the installation of formwork and the tying of reinforcing steel structures are avoided, thus preventing workers from shirking their responsibilities in tying the reinforcing steel. However, this patent has several drawbacks: First, it uses a whole precast concrete block instead of a wooden formwork as the bottom formwork, and this precast block occupies most of the volume of the wet joint concrete, resulting in a heavy weight and short length per block. This significantly increases the workload for workers, easily creating a safety risk of falling objects from heights and material waste. Secondly, while the precast blocks offer relatively greater adaptability to prefabrication and installation deviations, the uniform customization of wet joints of the same size, coupled with variations in the thickness of the top slab during precast beam production, and the influence of the bridge deck's cross slope, means that the inverted T-shaped precast blocks still do not adequately meet on-site requirements in terms of prefabrication and installation precision deviations. Thirdly, the precast blocks are ultimately connected as a whole through horizontal through-holes with grouting. The grouting material's compressive strength is far greater than its tensile strength, while the primary stress form for connecting the precast blocks through these through-holes is tension. Conventional grouting materials cannot withstand this tensile force; therefore, continuous reinforcing bars or prestressed tendons are required to meet the stress requirements. However, the process of installing continuous reinforcing bars after assembly is complex. Fourth, even if a continuous steel bar is installed in the through hole, the steel bar cannot be effectively connected with the precast block to form a whole. Instead, there is a lot of room for movement in the through hole, and the tensile force of the continuous steel bar is difficult to be evenly transmitted to the precast block. In fact, the tensile stress is still borne by the continuous steel bar and the grout in the through hole, resulting in a huge waste of materials.

[0014] Chinese invention patent application number 202111565315.7 discloses a prefabricated bridge deck structure and its construction method. It proposes using prefabricated connecting beams erected above and covering the structural gap between adjacent prefabricated beams. Several vertical reinforcing bars are pre-reserved on the top surface of the prefabricated beams, and these vertical reinforcing bars are welded or tied to the corresponding horizontal reinforcing bars. A layer of cast-in-place concrete is then placed over the prefabricated beams, prefabricated connecting beams, vertical reinforcing bars, and horizontal reinforcing bars. The drawbacks of this technical solution are: firstly, it is equivalent to adding a cover plate as a formwork-free base plate on top of the original prefabricated beam top slab. This measure thickens the bridge deck pavement, resulting in material waste and increasing the beam's self-weight, thus increasing the permanent load on the structure. Secondly, the protrusions on which the cover plate is placed are concave, which also makes it difficult for air bubbles to escape during vibration and easily leads to chipping and breakage during demolding.

[0015] Wet joints are important connection points in precast concrete bridge structures, and their connection methods directly affect the structural stability and load-bearing capacity of the entire bridge. Currently, the common construction methods for wet joints are suspended construction and various innovations based on suspended construction. However, regardless of the existing construction method or the patented technology solutions mentioned above, they all involve the installation of the bottom formwork for wet joints. This leads to many problems in wet joint construction: First, the width of wet joints is mostly 40cm to 80cm, and the edges of the precast beam flanges are reserved with steel bars for connecting adjacent beams, which results in even smaller gaps between beams, making formwork installation difficult. Second, suspended construction requires placing a large number of formwork, timber, or steel pipes above the beams, resulting in poor bridge deck cleanliness and hindering the finishing and roughening of the bridge deck concrete. Third, suspended construction requires fixing the bottom formwork by passing tie rods or bolts through the wet joint area. Although PVC sleeves can pass through the area to be poured, improper sealing of bolt holes after construction can easily lead to bridge deck leakage. Fourth, when removing formwork during suspended construction, the lower formwork cannot be fixed and can only be loosened by unscrewing the bolts and nuts, allowing the formwork to fall freely, which can easily damage the formwork and reduce the number of times the formwork can be reused. Utility Model Content

[0016] To address the aforementioned problems, the purpose of this utility model is to provide a formwork-free, jointless beam structure for post-cast top slabs. The beams are designed as conventional beams and thin-plate low beams, and the assembly structure of traditional beams is improved by staggering the flange plates of the thin-plate low beams with the flange plates of the adjacent conventional beams on both sides. This allows the top plate of the thin-plate low beams to act as a bottom formwork, enclosing the construction space for casting the post-cast top slab with the flange plates of the adjacent conventional beams on both sides. This eliminates the need for formwork and wet joints, avoiding problems such as difficulties in formwork installation, the risk of falling objects from heights, and the tendency for wet joints to crack and leak.

[0017] This utility model is achieved through the following technical solution.

[0018] A formwork-free, jointless beam structure for post-cast top slab, characterized by comprising: conventional beams erected at uniform intervals on piers; flange plate reinforcement embedded on both sides of the conventional beam flange plates; thin-plate low beams erected on piers and positioned between adjacent conventional beams; U-shaped connecting reinforcement embedded on the upper surface of the top plate of the thin-plate low beams; transverse connecting reinforcement spanning the top of the thin-plate low beams and connecting between the opposite flange plate reinforcements of adjacent conventional beams; longitudinal connecting reinforcement close to both sides of the U-shaped connecting reinforcement and connected to the transverse connecting reinforcement; post-cast top slab; and sealing agent. The flange plates of the thin-plate low beams are staggered and connected to the flange plates of the adjacent conventional beams on both sides. The sealing agent is filled in the gap between the ends of the flange plates of the thin-plate low beams and the ends of the flange plates of the conventional beams, so that the top plate of the thin-plate low beams serves as a bottom formwork and encloses the flange plates of the adjacent conventional beams on both sides to form a construction space for casting the post-cast top slab. The flange plate reinforcement and U-shaped connecting reinforcement are connected into an integral steel mesh structure within this construction space by the transverse connecting reinforcement and the longitudinal connecting reinforcement.

[0019] Preferably, the flange gap 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 is... △h It is 3~5cm.

[0020] Preferably, the top plate thickness of the thin-plate low beam is... a It is 5~8cm.

[0021] Preferably, the overlap length between the flange plates of the thin-plate low beam and the flange plates of the conventional beam is the flange plate misalignment distance. △L It is 20~30cm.

[0022] Preferably, the end of the conventional beam flange is toothed, and the flange reinforcement is embedded in the protruding toothed block at the toothed end of the flange.

[0023] Preferably, a splicing groove is reserved below the end of the flange plate of the conventional beam; the flange plate of the thin plate low beam is embedded in the splicing groove of the flange plates of the conventional beams on both sides, so that the flange plate of the thin plate low beam is staggered and connected to the flange plates of the conventional beams on both sides below.

[0024] Preferably, the distance between the end of the flange plate of the thin-plate low beam and the side of the splicing groove is... b And the gap between the upper surface of the flange plate of the thin-plate low beam and the top edge of the splicing groove. c All are 3~5cm.

[0025] Preferably, 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 poured, the exposed part 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.

[0026] Preferably, the sealing agent is a foam adhesive or a polyurethane foaming agent.

[0027] Compared with the prior art, the beneficial effects of this utility model are as follows: 1) This utility model makes simple improvements on the basis of traditional design, which has little impact on the construction process. The relatively mature precast beam construction process can continue to be used. However, through simple improvements, the conventional formwork and pouring of wet joints are eliminated, which fundamentally solves many process and quality problems involved in wet joint construction projects.

[0028] 2) In this utility model, the top plate of the thin plate low beam can be regarded as the bottom formwork of the cast-in-place top plate. On the one hand, the step of installing the formwork is eliminated, which simplifies the construction process. On the other hand, the cast-in-place structure will not be affected by gravity and will also greatly reduce the disturbance of the cast-in-place structure to changes in the surrounding environment and vehicle traffic, thus avoiding quality problems such as cracks and water leakage.

[0029] 3) During the construction process, this utility model does not require formwork at the bottom of the beam and there are no holes in the bridge deck, which greatly ensures the safety of bridge deck construction and reduces the risk of objects falling from heights during cross-line construction.

[0030] 4) In this utility model, the surface of the cast-in-place roof slab is flat and the shape is simple, which is friendly to the processes of pouring, vibrating, demolding and roughening, and will not create additional quality hazards.

[0031] 5) In this utility model, U-shaped connecting steel bars are pre-embedded in the top slab of the thin-plate low beam. The length of the steel bars must exceed the top surface of the cast-in-place top slab. After the cast-in-place top slab is poured, the exposed part 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. The steel structure is not complicated, but it takes into account the connection and stress requirements of all aspects. Attached Figure Description

[0032] Figure 1 This is the main view of the present invention.

[0033] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0034] Figure 3 This is a top view of the structure of this utility model;

[0035] Figure 4 for Figure 3 Enlarged view of point B in the middle;

[0036] Figure 5 This is the main view of a conventional beam.

[0037] Figure 6 This is the main view of the thin-plate low beam structure.

[0038] Figure 7 The main view of the structure is shown, which shows the staggered connection between the flange plate of the thin-plate low beam and the flange plate of the adjacent conventional beam.

[0039] Figure 8 This is a schematic diagram showing the erection of the beams from the middle outwards.

[0040] Figure 9 This is a front view of the structure of the present invention when the splicing slot is set;

[0041] Figure 10 The main view structural diagram showing the staggered connection between the flange plate of the thin plate beam and the flange plate of the adjacent conventional beam when setting the splicing slot;

[0042] The meanings of the markings in the above figure are as follows: 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, toothed block 7, post-cast top plate 8, toothed block 9, splicing groove 10, sealing agent 11, flange plate 12, top plate 13. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are merely illustrative examples of the present invention, but the scope of protection of the present invention is not limited thereto. The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0044] This embodiment provides a formwork-free, jointless beam-slab structure with a post-cast top slab. Please refer to [link / reference]. Figures 1 to 8 It includes conventional beams 2 erected at uniform intervals on piers 1, flange plate reinforcement 4 embedded on both sides of the flange plate of the conventional beams 2, thin plate low beams 3 erected on piers 1 and located between adjacent conventional beams 2, U-shaped connecting reinforcement 5 embedded on the top surface of the top plate of the thin plate low beams 3, transverse connecting reinforcement 6 spanning above the thin plate low beams 3 and connecting between the opposite flange plate reinforcement 4 of the adjacent conventional beams 2, longitudinal connecting reinforcement 7 close to both sides of the U-shaped connecting reinforcement 5 and connected to the transverse connecting reinforcement 6, post-cast top slab 8, and sealing agent 1. 1; The flange plate of the thin plate beam 3 is staggered with the flange plate of the conventional beam 2 on both sides. The sealing agent 11 is filled in the gap between the end of the flange plate of the thin plate beam 3 and the end of the flange plate of the conventional beam 2, so that the top plate of the thin plate beam 3 can be used as the bottom formwork to enclose the flange plates of the conventional beams on both sides to form a construction space for pouring the post-cast top plate 8. The flange plate steel bars 4 and U-shaped connecting steel bars 5 are connected into an integral steel mesh structure in the construction space by transverse connecting steel bars 6 and longitudinal connecting steel bars 7.

[0045] Furthermore, in a preferred embodiment, the flange gap distance between the upper surface of the flange plate of the thin-plate short beam 3 and the bottom edge of the flange plate end of the conventional beam 2 is... △h The gap should be 3-5cm. When designing the height of the thin-plate low beam 3, at the misalignment point between the flange plate of the thin-plate low beam and the flange plate of the adjacent conventional beams on both sides, a suitable flange plate gap distance needs to be considered. △h To ensure sufficient space for position adjustment during beam installation, but the flange gap distance... △h is not advisable If the gap is too large, it will make it difficult to seal during the subsequent pouring of the top slab, and the flange plate gap distance will be too large. △h The flange clearance distance can be determined by comprehensively considering the actual process precision level on site. △h The diameter should be controlled at 3-5cm.

[0046] Furthermore, in a preferred embodiment, the top plate thickness of the thin-plate beam 3 is... a The thickness is 5-8cm; since the top slab of the thin-plate low beam 3 can be regarded as the bottom formwork of the post-cast top slab, its thickness does not need to be too thick. The specific thickness can be comprehensively considered based on the actual situation such as the bridge span and the height of the precast beam. Usually, the thickness of the top slab of the thin-plate low beam is... a The diameter should be controlled between 5 and 8 cm.

[0047] Furthermore, in a preferred embodiment, the overlap length between the flange plate of the thin-plate short beam 3 and the flange plate of the conventional beam 2, i.e. the flange plate misalignment distance, is... △L The thickness is 20-30cm. Since the top slab of the thin-plate low beam serves as the bottom formwork for the post-cast top slab, at the misalignment point between the flange plate of the thin-plate low beam and the flange plate of the adjacent conventional beam on both sides, the flange plate of the thin-plate low beam needs to partially overlap with the flange plate of the conventional beam. This overlap length is typically the flange plate misalignment distance. △L The height should be controlled between 20 and 30 cm.

[0048] Furthermore, in a preferred embodiment, the ends of the flange plates of the conventional beam 2 are toothed, and the flange plate reinforcing bars 4 are pre-embedded in the protruding toothed blocks 9 at the toothed ends of the flange plates, thereby increasing the connection strength between the post-cast top slab and the conventional beam; in addition, a splicing groove 10 is reserved below the ends of the flange plates of the conventional beam 2; the flange plates of the thin-plate low beam 3 are embedded in the splicing grooves 10 of the flange plates of the adjacent two conventional beams 2, so that the flange plates of the thin-plate low beam are staggered and connected to the flange plates of the adjacent two conventional beams below; base The above configuration achieves two main advantages: firstly, it significantly reduces the thickness of the post-cast roof slab 8, thereby lowering construction costs; secondly, the thin-plate low beam flange is embedded in the splicing groove of the conventional beam flange on both adjacent sides, thus enhancing the connection strength between the thin-plate low beam, the conventional beam, and the cast-in-place roof slab; and thirdly, to ensure sufficient installation and adjustment space during beam installation, the distance b between the end of the flange of the thin-plate low beam 3 and the side of the splicing groove 10, and the gap between the upper surface of the flange of the thin-plate low beam 3 and the top edge of the splicing groove 10 are also considered. c All are 3~5cm.

[0049] Furthermore, in a preferred embodiment, the height of the U-shaped connecting steel bar 5 is greater than the thickness of the post-cast top slab 8, so that after the post-cast top slab 8 is poured, the exposed part of the U-shaped connecting steel bar 5 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.

[0050] Furthermore, in a preferred embodiment, the sealing agent 11 is a foam adhesive or a polyurethane foaming agent. Example

[0051] Without setting the splicing slot 10, the construction method of the formwork-free, jointless beam structure for post-cast top slab of this utility model includes the following steps:

[0052] S1, beam design

[0053] like Figure 1 , Figure 3 and Figure 7 As shown, in this utility model, the beam segment includes a conventional beam 2 and a thin-plate low beam 3. The beam segment is assembled in a combination of conventional beams, thin-plate low beams, conventional beams, thin-plate low beams, ..., conventional beams, thin-plate low beams, and conventional beams. The thin-plate low beam 3 is always assembled between adjacent conventional beams 2, and the flange plate of the thin-plate low beam 3 is offset from the lower part of the flange plate of the adjacent two conventional beams 2. Figure 7 As shown, in order for the beams to be assembled in the above-described configuration, the dimensions of the beams in this invention should meet the following requirements: H = h + H 1 + △h， in H For standard beam height, H 1 This refers to the end thickness of a conventional beam flange plate. hFor thin-slab, low-beam beams, △h is Flange clearance ， Flange clearance Right now The vertical distance between the upper surface of the thin-plate short beam flange and the bottom edge of the conventional beam flange at the offset connection point below the flanges of the adjacent conventional beams; based on the above beam size design, taking a conventional beam as a T-beam as an example, the thin-plate short beam in this utility model can be based on a conventional beam, and the following improvements can be made without changing the thickness of the conventional beam's bottom plate and web:

[0054] First, reduce the web height to create a height difference with the conventional beam, ensuring that the flanges of the thin-plate short beam can be staggered and connected to the lower part of the flanges of the adjacent conventional beams. When designing the height of the thin-plate short beam, it is necessary to consider setting an appropriate flange gap distance. △h To ensure sufficient space for position adjustment during beam installation, but the flange gap distance... △h not should If the gap is too large, it will make it difficult to seal during the subsequent pouring of the top slab, and the flange plate gap distance will be too large. △h The flange clearance distance can be determined by comprehensively considering the actual process precision level on site. △h Control the length to 3-5cm;

[0055] Secondly, reduce the thickness of the top slab. Since the top slab of the thin-slab low beam can be regarded as the bottom formwork of the post-cast top slab, its thickness does not need to be too thick. The specific thickness can be comprehensively considered based on the actual situation such as the bridge span and the height of the precast beam. The thickness of the top slab of the thin-slab low beam is usually... a Control the length to 5-8cm;

[0056] Third, increase the width of the top slab. Since the top slab of the thin-slab low beam serves as the bottom formwork for the post-cast top slab, appropriate flange plate spacing needs to be set. △L This is to allow the flange plates of the thin-plate low-beam to partially overlap with those of the conventional beam flange plates. The typical flange plate spacing is... △ L The height should be controlled between 20 and 30 cm.

[0057] The number of beam segments is determined based on the bridge design parameters. Specifically, since the thin-plate low beams are always assembled between adjacent conventional beams, meaning they can only be located in the middle beam position, this precast beam structure can only be used for an odd number of beam segments. The number of beam segments is usually determined based on the bridge deck design width, typically 5 or 7 segments. According to design convention, conventional road sections use 5 segments, with the beam segment combination being conventional beam, thin-plate low beam, conventional beam, thin-plate low beam, and conventional beam. Curved sections or forks in the road use 7 segments, with the beam segment combination being conventional beam, thin-plate low beam, conventional beam, thin-plate low beam, conventional beam, thin-plate low beam, and conventional beam.

[0058] S2, Precast Beams

[0059] Based on the number and size of the beams determined in step S1, each beam is prefabricated in the factory in the order of beam erection.

[0060] Please see Figure 5 When prefabricating conventional beam 2, flange plate steel bars 4 are pre-embedded on both sides of the flange plate of conventional beam 2. The flange plate steel bars are designed as traditional pre-reserved steel bar structures. In addition, in order to increase the connection strength between the post-cast top slab 8 and conventional beam 2, the ends of the conventional beam flange plate 2 are prefabricated as toothed, and the flange plate steel bars 4 are pre-embedded on the protruding toothed blocks 9 at the toothed ends of the flange plate.

[0061] Please see Figure 6 When precasting the thin-plate low beam 3, U-shaped connecting steel bars 5 are pre-embedded on the upper surface of the top slab of the thin-plate low beam 3, and the height of the U-shaped connecting steel bars 5 is greater than the thickness of the post-cast top slab 8, so that after the post-cast top slab is poured, the exposed part of the U-shaped connecting steel bars can be directly used as the pre-embedded hook bars for connecting the steel mesh of the cast-in-place layer of the bridge deck; since the thin-plate low beam is staggered and located below the conventional beam, its flange plate ends do not need to be connected, so the pre-embedded steel bars at the ends of the thin-plate low beam can be eliminated. When precasting the top slab of the thin-plate low beam, due to the change in thickness, only the top slab steel bars need to be designed according to the thin plate structure requirements.

[0062] S3, Beam Segment Installation and Adjustment

[0063] The precast beams from step S2 are transported to the construction site and stored in the beam storage area. Due to the small thickness of the top slab of the thin-plate, low-span beams, stacking should be avoided as much as possible during storage. Additionally, care should be taken to protect the finished product during transportation to prevent damage to the weaker edges and corners. Please refer to [link / reference]. Figure 8 Then, according to the beam assembly form determined in step S1, the beams are installed sequentially according to their erection order, so that the thin-plate low beam is always assembled between adjacent conventional beams, and the flange plates of the thin-plate low beam are staggered with the flange plates of the adjacent conventional beams on both sides, leaving a flange plate gap. △h As an adjustment space for the beams, the top slab of the thin-plate low beam can serve as the bottom formwork for the post-cast top slab. The top slab of the thin-plate low beam and the flange plates of the conventional beams on both sides enclose the construction space for pouring the post-cast top slab. Since there is a height difference between the thin-plate low beam and the conventional beam, in order to ensure the installation of the thin-plate low beam, the beams must be installed in a certain order. The installation can be carried out from the outer beam to the inner beam, from the inner beam to the outer beam, or from the middle to both sides.

[0064] S4, Reinforcing bar binding

[0065] In addition to pre-embedding the flange plate reinforcement 4 and U-shaped connecting reinforcement 5 during beam prefabrication, this utility model also requires the installation of transverse connecting reinforcement 6 and longitudinal connecting reinforcement 7 to ensure the overall connection strength between beams. For details, please refer to: Figure 2 and Figure 4A transverse connecting bar 6 is connected across the top of the thin-plate beam 3 between the flange plate reinforcing bars 4 opposite to the adjacent conventional beams, and the transverse connecting bar 6 is connected to the U-shaped connecting bar 5; longitudinal connecting bars 7 are connected on both sides of the U-shaped connecting bar 5, and the longitudinal connecting bars 7 are connected above the transverse connecting bar 6, so that the flange plate reinforcing bars and the U-shaped connecting bars are connected into an integral structure through the transverse connecting bars and the longitudinal connecting bars; wherein, the connection points or intersections of the flange plate reinforcing bars, the U-shaped connecting bars, the transverse connecting bars and the longitudinal connecting bars are welded or tied, and the lap length is designed according to the specifications;

[0066] S5, Space Sealing and Pouring

[0067] Please see Figure 1 After the reinforcing bars are tied, foam adhesive or polyurethane foam is used as a sealing agent to seal the flange between the flange of the thin-plate low beam and the flange of the conventional beam on both sides. gap To prevent grout leakage during the subsequent pouring of the top slab, a seal is installed. Then, concrete of the same grade as the beams is poured, and proper vibration is required during pouring. The resulting top slab should be of a certain thickness. l=H 1 + △h, which is greater than Standard beam flange end thickness H 1 ;

[0068] S6. Post-pouring of the roof slab for curing.

[0069] After the pouring is completed, cover the slab with a membrane for curing in a timely manner to prevent cracks from forming in the subsequent pouring of the top slab. Example

[0070] With the splicing slot 10 set, the construction method of the formwork-free, jointless beam structure for post-cast top slab of this utility model is the same as in Example 2, but the following improvements are made based on Example 2: In step S2, during the prefabrication of the beam, a splicing slot 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 slot of the conventional beam flange plates on both adjacent sides, so that the thin-plate short beam flange plate is staggered with the lower part of the conventional beam flange plates on both adjacent sides, and the distance between the end of the thin-plate short beam flange plate and the side of the splicing slot is... b and the distance between the upper surface of the flange plate of the thin-plate low beam and the top edge of the splicing groove. c The determination needs to be made based on a comprehensive consideration of the prefabrication accuracy of the beam segments and the installation process. Make There is sufficient space for installation and adjustment when the beams are installed, usually b , c The value is 3~5cm; in this case, the distance between the upper surface of the flange of the thin plate short beam and the top edge of the splicing groove. c Equivalent to the flange clearance distance △h And the height of a conventional beamH Thin-plate low beams h Flange end thickness H 1 The distance between the upper surface of the flange plate of the thin-plate low beam and the top edge of the splicing groove c The following relationship exists: H = h + H 1 + c； In addition, due to the presence of splicing slots at the ends of conventional beam flange plates, the thickness at the flange plate ends is reduced. H 1 Get smaller Then the thickness of the top slab is l=H 1 + c. Therefore, the thickness of the post-cast top slab also becomes smaller; Meanwhile, the presence of the splicing groove causes abrupt changes in the flange interface, resulting in certain unfavorable stress conditions for the flange. To ensure the stress resistance of the flange, the thickness of the flange end is... H 1 With slot depth H 2 There should be a certain proportional relationship between them, that is H 1 = kH 2 The proportionality coefficient k It can be determined through mechanical analysis methods such as the finite element method.

Claims

1. A formwork-free, jointless beam structure with a post-cast top slab, characterized in that, The structure includes conventional beams erected at even intervals on the piers, flange reinforcement bars embedded on both sides of the conventional beam flanges, thin-plate low beams erected on the piers and positioned between adjacent conventional beams, U-shaped connecting reinforcement bars embedded on the upper surface of the top plate of the thin-plate low beams, transverse connecting reinforcement bars spanning the top of the thin-plate low beams and connecting between the opposite flange reinforcement bars of the adjacent conventional beams, longitudinal connecting reinforcement bars close to both sides of the U-shaped connecting reinforcement bars and connected to the transverse connecting reinforcement bars, a post-cast top slab, and a sealing agent. The flanges of the thin-plate low beams are staggered and connected to the flanges of the adjacent conventional beams on both sides. The sealing agent is filled in the gap between the ends of the flanges of the thin-plate low beams and the ends of the flanges of the conventional beams, so that the top plate of the thin-plate low beams can serve as a bottom formwork to enclose the flanges of the adjacent conventional beams on both sides to form a construction space for pouring the post-cast top slab. The flange reinforcement bars and U-shaped connecting reinforcement bars are connected into an integral steel mesh structure within this construction space by the transverse connecting reinforcement bars and the longitudinal connecting reinforcement bars.

2. The formwork-free, jointless beam structure with post-cast top slab as described in claim 1, characterized in that, The distance between the upper surface of the flange plate of a thin-plate low beam and the bottom edge of the flange plate end of a conventional beam. △h It is 3~5 cm.

3. The formwork-free, jointless beam structure with post-cast top slab as described in claim 1, characterized in that, The top plate thickness of the thin-plate low beam a It is 5~8 cm.

4. The formwork-free, jointless beam structure with post-cast top slab as described in claim 1, characterized in that, The overlap length between the flange plates of a thin-plate low beam and those of a conventional beam is called the flange plate misalignment distance. △L It is 20~30cm.

5. The formwork-free, jointless beam structure with post-cast top slab as described in claim 1, characterized in that, The flange plate of the conventional beam has a toothed end, and the flange plate reinforcement is pre-embedded on the toothed blocks protruding from the toothed end of the flange plate.

6. The formwork-free, jointless beam structure with post-cast top slab as described in claim 5, characterized in that, The flange plate of the conventional beam has a pre-reserved splicing groove at the lower end; the flange plate of the thin plate beam is embedded in the splicing groove of the flange plate of the conventional beam on both sides, so that the flange plate of the thin plate beam is staggered and connected to the flange plate of the conventional beam on both sides.

7. A formwork-free, jointless beam structure with a post-cast top slab as described in claim 6, characterized in that, The distance between the end of the flange plate of the thin-plate low beam and the side of the splicing groove b And the gap between the upper surface of the flange plate of the thin-plate low beam and the top edge of the splicing groove. c All are 3~5 cm.

8. The formwork-free, jointless beam structure with post-cast top slab as described in claim 1, characterized in that, 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 poured, the exposed part 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. A formwork-free, jointless beam structure with a post-cast top slab as described in claim 1, characterized in that, The sealing agent is a foam adhesive or a polyurethane foaming agent.

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