Large-span arch ring cast-in-place support constant-weight loading construction method

Abstract

The invention relates to a large-span arch ring cast-in-place support constant-weight loading construction method which comprises the steps of support erecting, formwork installing, support pre-pressing, pre-pressing unloading, parallel construction of an arch ring body, interval groove pouring and support dismantling according to the construction sequence. According to the step of pre-pressing unloading and arch ring body parallel construction, one section of arch ring body is constructed when one section of arch ring body is unloaded in the direction from the arch springing to the arch crown, unloading and arch ring construction are carried out synchronously, and after support pre-pressing is completed, the arch ring body is unloaded in the arch springing and arch crown parallel construction step is completed, and the arch ring body is unloaded in the arch springing and arch crown parallel construction step. Gradually advancing from the arch feet to the arch crown according to the principle that one section of arch ring is constructed after one section of arch ring is unloaded, and compared with a conventional scheme that the arch ring is constructed after unloading is completed, the construction period can be greatly shortened.

Description

Technical Field

[0001] The present application relates to the technical field of bridge construction engineering, specifically to the technical field of the construction method of constant weight ballast for cast-in-situ supports of large-span arch rings. Background Art

[0002] During the traditional construction process of cast-in-situ arch rings, in order to ensure the safety and stability of the final structure, it is usually necessary to preload the support. This process aims to simulate the actual load conditions, eliminate non-elastic deformations, and verify the safety of the support design.

[0003] However, for large-span arch ring structures, firstly, the staged preloading, unloading, and process monitoring of the support carried out in accordance with the specification requirements take a lot of time. Especially during the construction of single-span and large-span structures, the overall loading and unloading processes are particularly time-consuming, resulting in a significant extension of the flow operation cycle.

[0004] Secondly, since the arch ring is a continuous structure, during the process of segment-by-segment construction from the arch foot to the arch top, it will inevitably experience non-elastic and elastic deformations. These deformations accumulate with the construction progress, which may lead to deviations in the arch axis shape. Especially in the case of the arch foot being a hyperstatic structure, the cumulative deformation exceeding the allowable range will result in adverse structural stresses in the cantilever state, and even cause disease cracks, seriously affecting the construction quality.

[0005] In addition, the conventional preloading scheme, which simulates the actual load by setting up a horizontal preloading platform and applying vertical forces, is difficult to accurately reflect the actual stress conditions of the oblique and normal forces brought about by the change in the horizontal angle (from about 45° to 0°) of the arch ring structure from the arch foot to the arch top, thus unable to effectively verify the safety of the support structure.

[0006] In response to this, for example, Patent CN215629394U, a preloading sandbag system for the cast-in-situ concrete support system of the main arch ring of an arch bridge, discloses a preset sandbag device and adjusts the amount of sandbags. Another example is Patent CN111172878A, an intelligent preloading system and construction method for simulating construction loads of an arch bridge, which uses adjustable-weight water tanks to make the preloading more uniform. However, the operation is complex and the efficiency is low. The process of adjusting the amount of substances in the sandbags or water tanks to achieve the ideal preloading effect is time-consuming and laborious, which is not conducive to rapid construction. Summary of the Invention

[0007] In view of the above-mentioned requirements, the present application proposes a construction method of constant weight ballast for cast-in-situ supports of large-span arch rings, aiming to effectively control the support deformation and improve at least one of the above-mentioned problems by reasonably setting up a constant weight ballast device and adopting the method of constructing the arch ring while unloading, so that the support structure is always in a ballasted state.

[0008] To achieve the above object, the present application adopts the following technical solutions:

[0009] The construction method of constant weight ballast for the cast-in-situ support of large-span arch rings includes steps of setting up supports, installing formwork, preloading the supports, parallel construction of preloading unloading and the main body of the arch ring, pouring the interval groove, and removing the supports according to the construction sequence;

[0010] In the step of preloading the supports, symmetrically and synchronously load and preload along the arch curve direction from the arch foot to the arch top, and divide a single arch ring into multiple preloading load sections;

[0011] In the step of parallel construction of preloading unloading and the main body of the arch ring, construct one section of the main body of the arch ring for every section unloaded from the arch foot to the arch top direction, and the unloading is carried out synchronously with the construction of the arch ring.

[0012] In this way, after the preloading of the supports in this application is completed, it is gradually advanced from the arch foot to the arch top direction according to the principle of constructing one section of the arch ring for every section unloaded. Compared with the conventional scheme of constructing the arch ring after the unloading is completed, the construction period can be greatly shortened. In the case of saving the construction period, the personnel management fee, tower crane, and support rental fee are also greatly reduced.

[0013] At the same time, adopting the scheme of constructing the arch ring while unloading eliminates the inelastic deformation and basically forms the elastic deformation. After the linear adjustment of each section of the arch ring construction, there will be no cumulative structural deformation, and the arch axis shape is guaranteed. Further, the load is distributed along the arch curve direction, and the simulated stress condition of the support is closer to the actual construction condition of the main body of the arch ring.

[0014] In some possible implementation manners, in the step of preloading the supports, a single arch ring is symmetrically divided into six sections on one side from the arch foot to the arch top direction.

[0015] In some possible implementation manners, the preloading of the two sections of the preloading load on the arch foot side is carried out simultaneously, and the preloading of the arch top side is carried out section by section.

[0016] In some possible implementation manners, the steps of parallel construction of preloading unloading and the main body of the arch ring are as follows:

[0017] Step S1: Symmetrically unload the preloading loads of the first two sections on the arch foot side and symmetrically pour the concrete of the first section. The construction of the top plate of the first section is synchronized with the installation of the steel bar formwork of the bottom and web of the second section;

[0018] Step S2: Symmetrically unload the third section of the preloading load; symmetrically pour the concrete of the second section. The construction of the top plate of the second section is synchronized with the installation of the steel bar formwork of the bottom and web of the third section;

[0019] Step S3: Symmetrically unload the fourth section of the preloading load; symmetrically pour the concrete of the third section. The construction of the top plate of the third section is synchronized with the installation of the steel bar formwork of the bottom and web of the fourth section;

[0020] Step S4: Symmetrically unload the preloading load of the fifth section; symmetrically pour the concrete of the fourth section, and the construction of the top slab of the fourth section is synchronized with the installation of the steel bar formwork of the bottom web of the fifth section;

[0021] Step S5: Symmetrically unload the preloading load of the sixth section; symmetrically pour the concrete of the fifth section, and the construction of the top slab of the fifth section is synchronized with the installation of the steel bar formwork of the bottom web of the sixth section;

[0022] Step S6: Symmetrically pour the concrete of the sixth section, and install the steel bar formwork of the interval slot.

[0023] In some possible embodiments, the interval slot is arranged between the preloading loads of the fourth section and the fifth section.

[0024] In some possible embodiments, the preloading unloading and the construction process parallel to the main arch ring include unloading the preloading load, laying the bottom film, tying the steel bars, and closing the formwork to pour the concrete.

[0025] In some possible embodiments, an anti-slip triangular support frame is provided at the bottom of each preloading load section.

[0026] In some possible embodiments, the triangular support frame is welded to the top of the longitudinal beam.

[0027] In some possible embodiments, the preloading load is a sandbag, and the sandbag is covered with a flower rain cloth. Description of the Drawings

[0028] Figure 1 is a schematic diagram of the support erection of the construction method of this application;

[0029] Figure 2 is a schematic diagram of the support preloading of the construction method of this application;

[0030] Figure 3 is a schematic diagram of unloading the preloading of the first and second sections and pouring the first section of the construction method of this application;

[0031] Figure 4 is a schematic diagram of unloading the preloading of the third section and pouring the second section of the construction method of this application;

[0032] Figure 5 is a schematic diagram of unloading the preloading of the fourth section and pouring the third section of the construction method of this application;

[0033] Figure 6 is a schematic diagram of unloading the preloading of the fifth section and pouring the fourth section of the construction method of this application;

[0034] Figure 7 is a schematic diagram of unloading the preloading of the sixth section and pouring the fifth section of the construction method of this application;

[0035] Figure 8It is a schematic diagram of the sixth pouring section of the construction method of this application;

[0036] Figure 9 It is a schematic diagram of the pouring interval groove of the construction method of this application;

[0037] Figure 10 It is a schematic diagram of the support removal of the construction method of this application. Specific implementation manners

[0038] The features of this application and other related features are further described in detail below through embodiments for the understanding of those skilled in the same industry:

[0039] It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the terms "bottom surface" and "top surface", "inner" and "outer" refer to the directions towards or away from the geometric center of a specific component respectively.

[0040] Furthermore, unless otherwise clearly specified and defined, the terms "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this case can be understood according to specific situations.

[0041] Before the construction of traditional cast-in-place beams or cast-in-place arches, the support structure needs to be preloaded. The main purposes of preloading are to check the safety of the support, eliminate the non-elastic compression of the support, measure the elastic deformation of the support, and adjust the pre-camber of the support. The preloading schemes in the prior art generally use concrete precast blocks, preloading sandbags / water bags for graded loading after the support is erected, and graded unloading after the preloading observation is completed. The pre-camber is set according to the observation data, and then the construction of the main structure is carried out. This scheme is more applicable to small-span cast-in-place beam structures, and the preloading platform is basically set horizontally, with less loading difficulty.

[0042] Generally speaking, for simply supported beams with a span not greater than 40m, continuous beams with a span not greater than 80m, or small-span arch structures using the support cast-in-place process, the main structure construction is carried out after the overloading preloading is completed and all unloading is done according to the specifications.

[0043] There are also other related cases where a stepped platform is first erected, and then loading preloading is carried out on the platform. After the preloading is completed, all unloading is done, and the arch ring construction is carried out after the preloading platform is removed. This scheme can only apply vertical loads and cannot simulate the oblique and normal components of the self-weight of relevant structures in actual construction, which does not conform to the actual working conditions.

[0044] Especially when the arch ring spans across a distance of up to 150m and has an arch rise of 30m, when using the cast-in-place method with a ground-supported scaffold in sections, since the arch ring has a relatively large horizontal component force on the scaffold structure during the construction process compared to a conventional cast-in-place beam. After the cast-in-place in sections and loading, there will inevitably be cumulative deformation in the scaffold structure, and since the arch ring is a continuous structure, adverse structural stresses will be generated under the condition of cumulative deformation. Therefore, ensuring that the structural alignment and the internal force distribution of the structure reach the ideal design state is the key difficulty in the construction of large-span arch rings. The specific construction difficulties and problems with conventional preloading are as follows.

[0045] 1. During the construction of the cast-in-place scaffold, in accordance with the specification requirements, staged preloading, unloading, and process monitoring are required. Only after the entire preloading and unloading procedures are completed can the construction stage of the main structure be entered. When using the flow operation method to gradually advance, especially in the case of constructing a single-span and large-span structure, the overall loading and unloading process takes an extremely long time, seriously affecting the project progress. Therefore, this traditional process results in a long flow operation time and delays the start time of the main structure construction.

[0046] 2. In the construction of the arch ring, since it is a continuous structure and the scaffold is designed as an integral structure, during the process of constructing section by section from the arch foot to the arch top, the scaffold will exhibit certain non-elastic and elastic deformations. As the construction progresses, these deformations gradually accumulate, and ultimately may lead to deviations in the arch axis alignment. Especially at the arch foot part, which is a hyperstatic structure, when the cumulative deformation of the scaffold exceeds the allowable range, adverse structural stresses will be generated in the cantilever state before the arch ring is closed, and in severe cases, it may even cause disease cracks, posing a significant potential hazard to the construction quality. Therefore, controlling the cumulative deformation of the scaffold is crucial for ensuring the arch axis alignment and structural safety.

[0047] 3. Conventional preloading schemes usually first set up a horizontal preloading platform and then carry out the loading construction. At this time, the preloading load mainly generates vertical forces. However, for the arch ring structure, its horizontal angle changes regularly within a certain range (about 45° to 0°) from the arch foot to the arch top, which means that the preloading load should consider the effects of both oblique and normal forces on the scaffold. Since the traditional preloading simulation method only focuses on vertical loading and cannot accurately reflect this complex actual stress condition, there is a deviation between the simulation result and the real working condition, making it difficult to effectively verify the safety of the scaffold structure. Therefore, the existing preloading methods have deficiencies in ensuring construction safety.

[0048] Please refer to Figures 1 to 10, the construction method of constant weight ballast for the cast-in-place support of the large-span arch ring in this application includes the steps of erecting the support 200, installing the formwork 300, preloading the support, unloading the preload and constructing in parallel with the main body of the arch ring, pouring the interval groove 500, and removing the support 200 in accordance with the construction sequence. In the step of preloading the support, symmetrically and synchronously loading and preloading along the curve direction of the arch ring from the arch foot to the arch top, and dividing a single arch ring into multiple preloading load sections. In the step of unloading the preload and constructing in parallel with the main body of the arch ring, construct one section of the main body of the arch ring every time one section is unloaded from the arch foot to the arch top direction, and the unloading is carried out synchronously with the arch ring construction.

[0049] First, please refer to Figure 1 , the support 200 is erected between the abutments 100. The erection method of the support 200 is a commonly used technical means in the industry and will not be elaborated in detail here. As in this embodiment, when the large-span arch ring is 150m, a floor combination support (side support: φ630×10mm steel pipe, transverse load-bearing beam 3I40a, longitudinal distribution beam I32a, formwork system; middle support: φ630×10mm steel pipe, transverse load-bearing beam 2I40a, Bailey beam, disc buckle support, formwork system), and an inclined anti-slip support frame can be used for erection.

[0050] In some embodiments, considering the process of preloading load stacking, if the cumulative oblique component force of the self-weight of the preloading load is too large, resulting in the instability of the stacking state, after the installation of the support 200 in this application, at least an anti-slip triangular support frame 210 is provided at the bottom of each preloading load section to ensure the construction safety during the preloading process and enable the preloading load 400 to be stably stacked on the curved surface, which can simulate the actual working conditions better than the traditional method of setting a horizontal preloading platform for stacking. Specifically, the triangular support frame 210 is welded to the top of the longitudinal beam. The installation of the formwork 300 mainly refers to the side formwork at this stage.

[0051] As a comparative example, in the traditional process, whether it is a cast-in-place beam support platform or a stepped platform for the arch ring support, the platform is basically in the horizontal direction, and the preloading load is transferred to the support as a vertical load, which cannot truly simulate the actual stress conditions of the arch ring.

[0052] Please refer to Figure 2 , in the stage of preloading the support, in this application, the step of preloading the support divides a single arch ring symmetrically into six sections on one side from the arch foot to the arch top direction. That is, the numbers ① to ⑥ in the figure are its segments, and the position of the arch top is the connection at both sides of ⑥. The preloading load 400 is symmetrically hoisted from the arch foot to the arch top direction and stacked on the support 200. The preloading load 400 is a sandbag, and the sandbag is covered with a flower rain cloth to prevent the sandbag from being wet by rain and affecting the preloading load. Preferably, on the relatively stable side of the arch foot, the two sections of the preloading load 400 on the arch foot side can be carried out simultaneously, and the preloading load 400 on the arch top side is carried out section by section.

[0053] Figures 3 to 8It is the steps of preloading unloading and constructing parallel to the main body of the arch ring. Specifically, the process is to unload the preloading load 400, lay the bottom film, bind the steel bars, close the formwork and pour the concrete, thus forming the main body of the arch ring 600. During the specific construction, after the overall erection of the support 200 is completed and passed the acceptance, the preloading load 400 is symmetrically loaded in segments from the arch feet to the arch crown direction. Monitoring work should be done well according to the plan requirements for each stage of loading until the overall loading observation is qualified before the unloading construction can be carried out. First, unload two segments of the preloading load 400 from the arch feet to ensure two working faces of closing the formwork for the first segment and binding the steel bars for the second segment. Then, for each subsequent unloading, construct one segment of the arch ring. The support 200 can effectively eliminate the cumulative deformation under the eternal ballast state, ensuring that the arch axis shape of the arch ring and the stress of the key sections meet the design requirements.

[0054] The specific construction steps are as follows, where the first segment to the sixth segment respectively correspond to the labels ① to ⑥ in the attached drawings:

[0055] Step S1: Symmetrically unload the first two segments of the preloading load on the arch foot side and symmetrically pour the concrete of the first segment. The construction of the top slab of the first segment is synchronized with the installation of the bottom web steel bars and formwork of the second segment;

[0056] Step S2: Symmetrically unload the third segment of the preloading load; symmetrically pour the concrete of the second segment. The construction of the top slab of the second segment is synchronized with the installation of the bottom web steel bars and formwork of the third segment;

[0057] Step S3: Symmetrically unload the fourth segment of the preloading load; symmetrically pour the concrete of the third segment. The construction of the top slab of the third segment is synchronized with the installation of the bottom web steel bars and formwork of the fourth segment;

[0058] Step S4: Symmetrically unload the fifth segment of the preloading load; symmetrically pour the concrete of the fourth segment. The construction of the top slab of the fourth segment is synchronized with the installation of the bottom web steel bars and formwork of the fifth segment;

[0059] Step S5: Symmetrically unload the sixth segment of the preloading load; symmetrically pour the concrete of the fifth segment. The construction of the top slab of the fifth segment is synchronized with the installation of the bottom web steel bars and formwork of the sixth segment;

[0060] Step S6: Symmetrically pour the concrete of the sixth segment and install the steel bars and formwork of the interval slot 500.

[0061] In some embodiments, the interval slot 500 is arranged between the preloading loads of the fourth segment and the fifth segment, making it in a relatively middle position. Of course, it can also be added according to the size of the arch ring.

[0062] In this way, by adopting the scheme of constructing the arch ring while unloading, the inelastic deformation is eliminated and the elastic deformation is basically formed. After the construction linear adjustment of each segment of the arch ring, there will be no cumulative deformation of the structure, and the arch axis shape is guaranteed. Further, by loading along the arch ring curve direction, the simulated stress condition of the support is closer to the actual construction condition of the main body of the arch ring.

[0063] As a comparative example, in the traditional process, the overall unloading is carried out after the preloading is completed, and then the main structure construction is entered. Although the inelastic deformation is eliminated in the ideal state, the elastic deformation will inevitably accumulate and increase during the process of the construction load gradually increasing. The construction arch axis shape will deviate from the designed theoretical shape, and at the same time, it will also increase the adverse structural stress.

[0064] Please refer to Figure 9 , after the concrete strength of the last section of the arch ring 600 reaches 70%, the concrete of the spacer 500 is poured during the period with relatively low temperature.

[0065] Please refer to Figure 10 , after the concrete strength of the arch ring reaches 90%, the support is removed, and the support is removed synchronously and symmetrically from the top of the arch to the arch feet.

[0066] In this way, after the support preloading of the present application is completed, it is gradually advanced from the arch feet to the top of the arch according to the principle of constructing one section of the arch ring after unloading one section. Compared with the conventional scheme of constructing the arch ring after the unloading is completed, the construction period can be greatly shortened. In the case of saving the construction period, the personnel management fee, tower crane, and support rental fee are also greatly reduced.

[0067] For example, taking the 150m long-span arch ring described above as an example, due to the limitation of site conditions, the preloading sand bags are loaded and unloaded by tower crane hoisting. It is expected that there are more than 7000 preloading sand bags, and it takes 45 days to complete the hoisting. According to the traditional process, the start time of the arch ring needs to be delayed by one and a half months after all the unloading is completed. This scheme saves the time occupied by the unloading in the main body construction.

[0068] At the same time, in the present application, the support 200 is preloaded as a whole first, and then the method of constructing the arch ring while unloading is adopted, so that the support 200 structure is always in the ballast state to eliminate the problem of cumulative deformation of the support structure. Further, the problem of unstable accumulation of the preloading load on the steep inclined surface of the curve is also considered, and the anti-slip support frames 210 are arranged in sections to solve the risk of instability of the preloading load 400 caused by excessive oblique load of the preloading load 400. And it effectively avoids the deviation of the arch axis shape and the adverse structural stress caused by the cumulative deformation of the support 200, ensuring that the key control indexes of the arch ring can meet the design requirements.

[0069] As described above, the present case protects the construction method of the constant weight ballast of the cast-in-place support for the long-span arch ring. All technical solutions that are the same as or similar to the present case should be regarded as falling within the protection scope of the present case.

Claims

1. Construction method of constant pressure ballast for cast-in-place support of large-span arch ring, characterized in that, It includes steps of erecting scaffolds, preloading the scaffolds, unloading the preloading, constructing in parallel with the main arch ring, casting the interval slots, and removing the scaffolds in the construction sequence. In the step of preloading the scaffolds, symmetrically and synchronously loading the preloading from the arch feet to the arch crown along the arch ring curve direction and dividing a single arch ring into multiple preloading load segments. In the step of unloading the preloading and constructing in parallel with the main arch ring, unloading one segment and constructing one segment of the main arch ring from the arch feet to the arch crown direction, and the unloading is carried out synchronously with the arch ring construction.

2. The construction method of permanent load ballasting for the cast-in-place support of long-span arch rings according to claim 1, characterized in that, In the step of preloading the scaffolds, a single arch ring is symmetrically divided into six segments on one side from the arch feet to the arch crown direction.

3. The construction method of constant load ballasting for the cast-in-place support of a long-span arch ring as described in claim 2, characterized in that, The preloading of the two segments on the arch feet side is carried out simultaneously, and the preloading of the arch crown side is carried out segment by segment.

4. The construction method of constant load ballasting for cast-in-place support of long-span arch rings according to claim 2, characterized in that The steps of unloading the preloading and constructing in parallel with the main arch ring are as follows: Step S1: Symmetrically unloading the preloading of the first two segments on the arch feet side and symmetrically casting the concrete of the first segment. The construction of the first segment of the top plate is synchronized with the installation of the bottom web steel bars and formwork of the second segment. Step S2: Symmetrically unloading the preloading of the third segment; symmetrically casting the concrete of the second segment. The construction of the second segment of the top plate is synchronized with the installation of the bottom web steel bars and formwork of the third segment. Step S3: Symmetrically unloading the preloading of the fourth segment; symmetrically casting the concrete of the third segment. The construction of the third segment of the top plate is synchronized with the installation of the bottom web steel bars and formwork of the fourth segment. Step S4: Symmetrically unloading the preloading of the fifth segment; symmetrically casting the concrete of the fourth segment. The construction of the fourth segment of the top plate is synchronized with the installation of the bottom web steel bars and formwork of the fifth segment. Step S5: Symmetrically unloading the preloading of the sixth segment; symmetrically casting the concrete of the fifth segment. The construction of the fifth segment of the top plate is synchronized with the installation of the bottom web steel bars and formwork of the sixth segment. Step S6: Symmetrically casting the concrete of the sixth segment and installing the interval slot steel bars and formwork.

5. The construction method of constant load ballasting for the cast-in-place support of large-span arch rings according to claim 4, characterized in that, The interval slot is arranged between the preloading of the fourth segment and the fifth segment.

6. The construction method of constant load ballasting for the cast-in-situ support of large-span arch rings as described in claim 1, characterized in that, The process of unloading the preloading and constructing in parallel with the main arch ring includes unloading the preloading, laying the bottom film, binding the steel bars, and closing the formwork and casting the concrete.

7. The construction method of permanent load ballasting for the cast-in-place support of the long-span arch ring according to claim 1, characterized in that, An anti-slip triangular support frame is provided at the bottom of each preloading load segment.

8. The method for constructing the permanent load ballast of the cast-in-place support for the long-span arch ring according to claim 7, characterized in that, The triangular support frame is welded to the top of the longitudinal beam.

9. The construction method of permanent load ballasting for the cast-in-place support of large-span arch rings according to claim 1, characterized in that, The preloading is sandbags, and the sandbags are covered with flower rain cloth.

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