Fabricated prestressed concrete continuous beam construction method

Abstract

The invention provides an assembly type prestressed concrete continuous beam construction method which comprises the steps that a continuous beam is divided into a No.0 block and continuous segmental beams symmetrically arranged on the two sides of the No.0 block, the multiple continuous segmental beams are prefabricated to form an integral segmental beam before being folded, and construction is conducted according to the No.0 block firstly and the No.0 block secondly; then, the continuous segmental beams which are symmetrically located on the two sides of the No.0 block are constructed in sequence; the No.0 block is of a cast-in-place structure, the continuous segmental beam is of a prefabricated structure, and the prefabricated structure is prefabricated and maintained in a centralized mode; and after the continuous segmental beams are assembled, closure, subsequent tensioning, grouting and anchor sealing are completed according to the sequence that side span closure is conducted firstly and then middle span closure is conducted, system conversion is completed, and the bridge is formed.

Description

Technical Field

[0001] The invention relates to the technical field of construction of assembled continuous beams, and in particular to a construction method of assembled prestressed concrete continuous beams. Background Art

[0002] Prestressed concrete continuous beam bridge is a type of bridge structure with the advantages of good stress performance, fast construction speed and convenient maintenance. Due to the unloading effect of the negative bending moment at the support, the positive bending moment in the mid-span is greatly reduced, the bridge height is increased, the span capacity is increased, it adapts to limited space working conditions, avoids the impact of cross-construction, conforms to the current situation of bridge engineering construction in my country, and has wide promotion and application value.

[0003] At present, the main construction method of prestressed concrete continuous beam bridges in China is cantilever construction. The cantilever construction method uses a hanging basket to symmetrically hang materials such as formwork, steel bars and prestressed tendons on both sides of the bridge pier, and then pour and maintain the concrete. The maximum span of a prestressed concrete continuous beam with a constant cross-section can be about 80m, and the span of a prestressed concrete continuous beam with a variable cross-section can generally be about 200m.

[0004] However, under the conditions of changeable meteorological environment, cantilever construction is prone to temperature shrinkage changes, concrete creep and creep, especially when the concrete volume is large. Under poor maintenance, it will cause large-scale cracks on the outside of the concrete and cause loss of vertical prestress. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a construction method for an assembled prestressed concrete continuous beam, which, through assembled prefabricated components, has the effect of improving the construction conditions during production, increasing productivity, and improving the component production accuracy and overall quality. In order to avoid cracking of the continuous beam bridge and reduce the loss of vertical prestress, it is proposed to design the cantilever construction method of the prestressed concrete beam bridge into an assembled assembly construction method, and ensure effective connection between segments.

[0006] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows: The method for constructing a prefabricated prestressed concrete continuous beam includes dividing the continuous beam into a No. 0 block and continuous segments symmetrically located on both sides of the No. 0 block, prefabricating a plurality of continuous segment beams into an integral segment beam before closing them, and constructing the No. 0 block first and then constructing the segment beams symmetrically located on both sides of the No. 0 block; The block No. 0 is a cast-in-place structure, and the continuous segmental beam is a prefabricated structure, and the prefabricated structure is centrally prefabricated and maintained; after the assembly of several of the continuous segmental beams is completed, the side spans are closed first and then the middle spans are closed, followed by tensioning, grouting and anchoring to complete the system conversion and form a bridge.

[0007] Furthermore, it also includes the erection of the Block No. 0 brackets on both sides of the Block No. 0. Specifically, on the pedestal under the cantilever of the Block No. 0, the Block No. 0 brackets are built by double-jointing to form a crossbeam through the support of steel pipe columns and reinforcement of scissor braces.

[0008] Furthermore, the construction of block No. 0 is specifically as follows: a pier top bracket is installed between two No. 0 block brackets and below block No. 0, a permanent support is installed above the top pier bracket, and a temporary consolidation is installed between the top pier bracket and the permanent support, and then after pouring and curing between the two brackets, the cast prestressed tendons are threaded, tensioned, and grouted between the pier top bracket, the permanent support, and the temporary support to complete the construction.

[0009] Furthermore, in the prestressed tendon bundle, the vertical prestressed tendons are formed by fine-rolled threaded steel bars, and iron pipes are arranged outside the vertical prestressed tendons and the vertical prestressed steel pipe bundle.

[0010] Furthermore, the prefabricated structure is first prefabricated and cured in sections, and then assembled into an integral segmental beam in the prefabrication site, and then transported to the site, hoisted as a whole to form a continuous beam structure, and the side of the prefabricated structure forms a serrated structure, and the prefabricated structure is stored at room temperature.

[0011] Furthermore, the prefabricated structure is assembled specifically by applying a two-component epoxy resin adhesive on the serrated structure in the prefabrication site, and assembling the segmented prefabricated structure into a continuous beam segment integral structure in a segmented manner.

[0012] Furthermore, the overall structure of the continuous beam section is connected to block No. 0 by adhesive after being lifted by a movable Bailey frame hanging basket.

[0013] Furthermore, the temporary prestressed extrusion time is within 3 hours, and the extrusion pressure is not greater than 0.3Mpa.

[0014] Furthermore, it also includes the construction of a mobile Bailey frame basket for lifting the integral segmental beam, which is specifically assembled through a main truss, a suspension system, an anchoring system, a walking system, a working platform and a bottom formwork frame.

[0015] Furthermore, before the side span is closed, the side span segment is prefabricated, and the length of the side span segment is less than or equal to 2m.

[0016] The present invention has the following beneficial effects: The present invention can avoid concrete cracking and vertical prestress loss of segmental beams due to changes in the construction environment by designing the assembled construction method, improve the construction conditions when manufacturing the segmental beams, better control the material mix ratio, casting quality and maintenance conditions, and improve the overall quality of the segmental beams; the prefabrication of beam segments can improve the construction accuracy of the segmental beams, facilitate the control of the beam body size, and meet various design requirements; the prefabricated beams are completed in the factory, which improves labor productivity, reduces the waste of human resources, and improves construction efficiency. In the present invention, the continuous segment beam is produced according to the prefabricated structure and then hoisted as a whole before closing, thereby improving the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of the method for constructing an assembled prestressed concrete continuous beam provided by the present invention; Figure 2 A schematic diagram of the structure of the No. 0 block bracket provided by the present invention; Figure 3 A schematic diagram of the structure of the pier top bracket, permanent support and temporary consolidation of the No. 0 block provided by the present invention; Figure 4 A schematic diagram of the structure of the continuous beam segment provided by the present invention during construction; Figure 5 A schematic diagram of the structure of the prefabricated segments provided by the present invention during assembly; Figure 6 One of the structural schematic diagrams of the side span closure construction provided by the present invention; Figure 7 The second structural schematic diagram of the side span closure construction provided by the present invention; In the figure: 1. Integral segmental beam; 2. Block No. 0 bracket; 3. Block No. 0; 4. Continuous segmental beam; 5. Side span beam section; 6. Side span closure section; 7. Temporary locking; 8. Middle span closure section; 9. Tooth block; 10. Adhesive; 11. Permanent support; 12. Temporary consolidation; 13. Pier top bracket. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in the field based on these embodiments are all within the scope of protection of the present invention.

[0019] See attached Figure 1-7As shown, the prefabricated prestressed concrete continuous beam construction method in this embodiment has the characteristics of large torsional rigidity, good lateral distribution, high bearing capacity, and small structural deadweight. In this embodiment, the cantilever construction method is designed as a prefabricated assembly construction method. Through the prefabrication and assembly of segmental beams, while improving labor productivity, it can effectively reduce the temperature shrinkage changes, concrete creep and creep caused by environmental changes in continuous beam bridges, resulting in concrete cracks and vertical prestress loss.

[0020] The method for constructing an assembled prestressed concrete continuous beam of the present invention comprises dividing the continuous beam into a block 3 No. 0 and a plurality of continuous segmental beams 4 symmetrically disposed on both sides of the block 3 No. 0, and then prefabricating the plurality of segmental beams before closing to form an integral segmental beam 1; and constructing the block 3 No. 0 first, and then constructing the continuous segmental beams symmetrically disposed on both sides of the block 3 No. 0 in the order of: In the present embodiment, specifically, block No. 0 3 uses a cast-in-place structure, while the continuous segment beam 4 uses a prefabricated structure, and then all the prefabricated structures are centrally prefabricated and maintained, and stored before hoisting the corresponding continuous segment beam 4; after the assembly of several of the continuous segment beams 4 is completed, they are closed in the order of first closing the side spans and then closing the middle spans, followed by tensioning, grouting and anchoring to complete the system conversion and form a bridge.

[0021] In the conventional prior art, continuous segmental beams are cast in situ, but in the present embodiment, after they are prefabricated, several prefabricated structures are combined to form an integral segmental beam before being closed, which greatly improves the construction efficiency.

[0022] The technical solution of the present invention is applied to the project, and the entire detailed construction method process is as follows: Step 1, erection of support block No. 0; At this time, the No. 0 block support 2 is erected: before the construction of the continuous segmental beam, the No. 0 block support 2 is first erected, pre-stressed and inspected. If the inspection fails, adjustments need to be made until the inspection passes after the adjustments.

[0023] See attached Figure 2-3 As shown, the above step 1 is specifically as follows: the bracket is set up as shown in Figure 2 In the structure, the format of the support 2 of block 0 is to support 2 rows of φ630×10mm steel pipe columns on each side of the pedestal position of the cantilever lower projection surface of block 0 3, and set a 20a channel steel scissors brace in the middle of the horizontal and vertical directions of the steel pipe columns to connect and reinforce the steel pipe columns. Double HW400*408 is used as a crossbeam between the steel pipe columns, and double I32b I-beams are laid on it as longitudinal distribution beams, and finally the bottom plate and side molds are laid on the steel plate. The support is pre-pressed, and the construction of block 0 is carried out after acceptance; in this embodiment, the support is specifically set up on both sides of block 0 3 to form a corresponding space.

[0024] Step 2, Structural installation before construction of Block 0 3: Before the construction of block 0, it is necessary to install the pier top bracket 13, permanent support 11 and temporary consolidation 12. In this process, the permanent support 11 preferably uses a pot-type rubber movable support, and the temporary consolidation of block 0 uses fine-rolled threaded coarse steel bars. In this embodiment, the pier top bracket 13, permanent support 11 and temporary consolidation 12 are located on both sides of block 0 and are arranged below block 0 3.

[0025] Step 3, construction of block 3: Casting, curing, threading, tensioning and grouting of prestressed tendons of block 03.

[0026] In this embodiment, for pouring, concrete is poured in one go for block No. 0 in order to increase its integrity. After the concrete pouring is completed, geotextile should be used for covering and curing in a timely manner, and the curing time should be no less than 7 days.

[0027] Furthermore, in the construction of Block 0 3, the vertical prestressed tendons in the later stage were made of finely rolled threaded steel bars, and the prestressed steel strands and vertical prestressed tendons were wrapped with iron pipes, and finally grouting was performed. After the construction of Block 0 was completed, the longitudinal prestressed tendons and vertical prestressed tendons were tensioned and anchored.

[0028] Step 4: Prefabrication and centralized assembly of continuous segmental beams to form an integral segmental beam (i.e. Figure 1 Continuous beam segment in the

[0029] Specifically, the continuous segment beams 4 are prefabricated and stored in the factory, and the joints of adjacent continuous segment beams 4 are prefabricated into tooth blocks 9, which is convenient for subsequent assembly and various forces. At this time, the side of the tooth block 9 is provided with several concave and convex shapes along the height direction, the purpose is to facilitate installation, increase the installation bite force, improve the integrity of the continuous beam, and detect the quality of the prefabricated segment blocks. They can be used only after meeting the requirements. Specifically, each continuous segment beam 4 is provided with tooth blocks 9 on at least one side, and of course, on both sides, and then adjacent continuous segment beams 4 are connected by tooth blocks 9.

[0030] In actual construction, each continuous segmental beam 4 is first prefabricated and cured in sections, and then several continuous segmental beams 4 are assembled together in the prefabrication site to form an integral segmental beam 1, which is then transported to the construction site and hoisted to form the entire continuous beam structure.

[0031] In this embodiment, adjacent continuous segmental beams 4 are assembled by applying a two-component epoxy resin adhesive with a thickness of less than 3 mm on the tooth blocks 9 of the sawtooth structure, and assembling the segmented prefabricated structure into an integral segmental beam 1 in combination with the form of segmented prestressing.

[0032] Step 5: Install the mobile Bailey rack basket.

[0033] In this embodiment, the formed integral segment beam 1 needs to be hoisted by a mobile Bailey frame hanging basket and then connected with the No. 0 block 3 by adhesive.

[0034] In this embodiment, the mobile Bailey frame hanging basket is mainly composed of the main truss, suspension system, anchoring system, walking system, working platform, bottom formwork and other parts. The design parameters such as the size of the subsequent mobile Bailey frame hanging basket can be determined by referring to the cross-sectional dimensions and segments of the prestressed beam. The hanging basket is subjected to the acceptance sequence of preloading, relevant parameter monitoring, trial hanging, etc., and is transported to the site for assembly after passing the acceptance. In this embodiment, the purpose of the mobile setting is to facilitate adjustment as the construction position is adjusted.

[0035] In this embodiment, when assembling adjacent continuous segment beams 4 and connecting the entire integral segment beam 1 with block No. 0, prestressed extrusion can be added to increase the connection strength. At this time, the prestressed extrusion time is within 3 hours and the extrusion pressure is not greater than 0.3Mpa.

[0036] Step 5: Detailed introduction to the construction of a single prefabricated structure.

[0037] In this embodiment, taking block No. 1 as an example, the symmetrical lifting, trial assembly, adhesive application, and prestressing of block No. 1 are introduced.

[0038] The specific steps are as follows: After block No. 1 is transported to the site, it is hoisted by a Bailey frame hanging basket. The prefabricated assembly of the present invention adopts adhesive joints, and splicing glue is injected into the adhesive joints to form an adhesive layer. At this time, the splicing glue 10 is a two-component epoxy resin adhesive of A and B, which is a conventional material, composited by a variety of organic and inorganic modified materials, and has excellent properties of high strength and high thixotropy. The adhesive is mechanically mixed, and block No. 1 4 is tried to be assembled before gluing. The adhesive is evenly applied to cover the entire matching surface, and the application thickness is ≤3mm. Temporary prestress is applied to the adhesive joints for extrusion, and the extrusion force should be 0.2Mpa, and it should be completed within 3h. The temporary prestressed steel bundle can be removed after the permanent prestressing construction of the structure is completed.

[0039] Step 6, construction of remaining sections.

[0040] In this embodiment, the construction is carried out symmetrically according to the construction process of block 1 until the last segment is completed; at this time, the assembly method is used to construct the closed segment by glue joint assembly. The lower support of the side span beam segment 5 is erected by brackets, and the prefabricated segments are hung on the brackets. Permanent bearings are installed at the abutment position. The brackets can be removed only after the side span is closed and the concrete strength meets the requirements.

[0041] Step 7, close.

[0042] In this embodiment, the side spans are closed, the temporary consolidation is released, and the middle span is closed: the closing section adopts a cast-in-place concrete structure, the side spans are closed first, and then the middle span is closed.

[0043] In this embodiment, when the side span segments are prefabricated, care should be taken to control the length of the closing section within 2 meters to reduce the effects of concrete cracking caused by stress concentration. First, the side span is temporarily locked. The outer mold of the closing section adopts a steel film, and the inner mold adopts a combined wooden mold to ensure the appearance quality. After the temporary rigid structure is completed, the temporary prestressed beam is immediately tensioned to implement locking, and finally the concrete is poured. The closing section adopts micro-expansion concrete. After the tensioning and grouting of the side span closing section 6 are completed, the remaining transverse prestressed tendons are tensioned. The construction of the middle span closing section 8 is basically the same as that of the side span closing section. The middle span temporary lock 7 is set, but it should be noted that after the temporary rigid connection of the middle span closing section is set and part of the prestress is tensioned, the temporary lock of all movable supports on the fixed support side should be released. At the same time, according to the elevation provided by the linear control, a weight water tank is set at both ends of the closing mouth. During the pouring of concrete, the weight is gradually removed while pouring to ensure that the relative position of the beams at both ends of the closing mouth is basically unchanged, so as to prevent cracks in the newly poured concrete of the closing section.

[0044] Step 8: tensioning the overall prestressed tendons, grouting, and anchoring: The overall prestressing of the entire bridge can only be carried out after the concrete of the closing section reaches 80% of the design strength, and grouting and anchoring can be carried out within 2 days to complete the prefabricated construction. After the prestressing, grouting and anchoring of the entire bridge section are completed, the system conversion of the entire bridge can be carried out.

[0045] Through the above-mentioned construction method, the construction of the entire bridge is completed by adopting the prefabricated prestressed concrete continuous beam bridge construction method.

[0046] In this embodiment, the advantages of adopting this construction method, especially the connection method, are as follows: (1) Through centralized prefabrication and maintenance of continuous beam segments in factories, a stable environment is ensured during the production of prestressed concrete segments, reducing cracking of concrete caused by environmental changes.

[0047] (2) By replacing cast-in-place segments with prefabricated ones, the vertical prestressing loss inside the continuous beam caused by temperature changes can be reduced, thereby improving the serviceability and durability of the bridge.

[0048] (3) By optimizing organizational methods, sequential operations are transformed into flow operations, which improves labor efficiency while making full use of the work surface construction, resulting in a shorter construction period.

[0049] (4) When cross-line construction is involved, the impact of cast-in-place construction on existing roads and buildings is avoided, which is safe and environmentally friendly.

[0050] Compared with the construction method in the prior art, the segmented setting in this embodiment makes it more accurate, and the beam body can be designed in a variety of ways, which improves the construction efficiency. In this embodiment, the continuous beam is specifically divided into several parts, and then prefabrication is carried out in advance when the corresponding sections are constructed, which reduces the external storage time before the construction of the continuous bridge, thereby reducing the temperature shrinkage changes caused by environmental changes, concrete creep and creep, ensuring the quality of the concrete, reducing the generation of cracks, and the loss of vertical prestress.

[0051] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0052] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for constructing an assembled prestressed concrete continuous beam, characterized in that: The method includes dividing the continuous beam into a No. 0 block and continuous segmental beams symmetrically located on both sides of the No. 0 block, prefabricating a plurality of the continuous segmental beams before closing them to form an integral segmental beam, and constructing the No. 0 block first and then the continuous segmental beams symmetrically located on both sides of the No. 0 block in sequence; The block No. 0 is a cast-in-place structure, and the continuous segmental beam is a prefabricated structure, and the prefabricated structure is centrally prefabricated and maintained; after the assembly of several of the continuous segmental beams is completed, the side spans are closed first and then the middle spans are closed, followed by tensioning, grouting and anchoring to complete the system conversion and form a bridge.

2. The method for constructing an assembled prestressed concrete continuous beam according to claim 1, characterized in that: It also includes the erection of the Block No. 0 bracket on both sides of the Block No.

0. Specifically, on the pedestal under the cantilever of Block No. 0, the Block No. 0 bracket is built by double-jointing to form a crossbeam through the support of steel pipe columns and reinforcement of scissor braces.

3. The method for constructing an assembled prestressed concrete continuous beam according to claim 2, characterized in that: The construction of block No. 0 is specifically as follows: between the two No. 0 block supports and below block No. 0, a pier top bracket is installed, a permanent support is located above the top pier bracket, and a temporary consolidation is set up between the top pier bracket and the permanent support, and then after pouring and curing between the two supports, the cast prestressed tendons are threaded, tensioned, and grouting is performed between the pier top bracket, the permanent support, and the temporary support to complete the construction.

4. The method for constructing an assembled prestressed concrete continuous beam according to claim 3, characterized in that: In the prestressed tendon bundle, the vertical prestressed tendons are formed by fine-rolled threaded steel bars, and iron pipes are arranged outside the vertical prestressed tendons and the vertical prestressed steel pipe bundle.

5. The method for constructing an assembled prestressed concrete continuous beam according to claim 1, characterized in that: The prefabricated structure is first prefabricated and cured in sections, and then assembled into an integral segmental beam in a prefabrication site, and then transported to the site, hoisted as a whole to form a continuous beam structure, and the side of the prefabricated structure forms a serrated structure, and the prefabricated structure is stored at room temperature.

6. The method for constructing an assembled prestressed concrete continuous beam according to claim 5, characterized in that: The prefabricated structure assembly is specifically to apply a two-component epoxy resin adhesive on the serrated structure in the prefabrication site, and to assemble the segmented prefabricated structure into a continuous beam segment integral structure in a form of segmented prestressed extrusion.

7. The construction of prestressed concrete continuous beam according to claim 6 is characterized in that: The overall structure of the continuous beam section is lifted by a movable Bailey frame hanging basket and then connected with the No. 0 block by an adhesive.

8. The method for constructing an assembled prestressed concrete continuous beam according to claim 6, characterized in that: The prestressed extrusion time is within 3 hours, and the extrusion pressure is not greater than 0.3Mpa.

9. The method for constructing an assembled prestressed concrete continuous beam according to claim 7, characterized in that: It also includes the construction of a mobile Bailey frame for lifting integral segmental beams, which is assembled through the main truss, suspension system, anchoring system, walking system, working platform and bottom formwork.

10. The method for constructing an assembled prestressed concrete continuous beam according to claim 1, characterized in that: Before the side span is closed, the side span segment is prefabricated, and the length of the side span segment is less than or equal to 2m.

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