A jacking construction method for a large-span composite arch bridge with adjustable construction status

Abstract

The present invention relates to a method for jacking construction of a large-span composite arch bridge with adjustable construction status. The method is characterized in that steel arches, steel beams, hangers, and temporary struts connecting the steel arches and steel beams are pre-assembled on shore into a beam-arch composite system, and the hangers are initially tensioned. During the jacking process of the composite arch bridge with the hangers and temporary struts, a functional function is constructed based on the stress limit of the components, and the construction status during the jacking process is adjusted by optimizing the tensioning force of the hangers. This construction method adjusts the stress state of the composite arch bridge during the jacking process in real time by adjusting the tensioning force of the hangers, thereby ensuring the coordination of the arches and beams to a certain extent, improving the stress performance of the structure, reducing the number of temporary piers in the water and the number of temporary struts for the arches and beams, and reducing the complexity of the structural construction. It has high promotion value in terms of applicability, economy, construction quality, construction period, etc., and has pioneering significance for similar projects in the future.

Description

Technical Field

[0001] The invention relates to the technical field of bridge engineering, in particular to a jacking construction method for a large-span combined system arch bridge with adjustable construction status. Background Art

[0002] Composite arch bridges, with their elegant appearance, reasonable mechanical properties, and good economic efficiency, have gained a significant place in the construction of long-span bridges. Common construction methods for composite arch bridges include scaffolding, rotation, cable hoisting, and jacking.

[0003] For composite steel arch bridges, the scaffolding construction method involves installing the steel beam first, then assembling the steel arch with scaffolding on the beam. This is known as the beam-first, arch-later construction method. Regardless of the method used to construct the steel beam, the arch construction requires scaffolding on the beam, often requiring numerous temporary piers to ensure the beam's load-bearing capacity. However, installing temporary piers and scaffolding in the middle of a river is both costly and difficult. Furthermore, for rivers requiring navigation, the location and number of temporary piers may be subject to navigation restrictions.

[0004] The rotation construction method divides the arch rib or the entire superstructure into two half spans, creates half arches on both sides, and then uses a power device to rotate the two half arches to the bridge axis position to form an arch. This method has a fast construction speed and low cost, but it is not suitable for arch bridges located in the middle of the river, far away from the two banks, or multi-span continuous arch bridges.

[0005] Cable hoisting construction involves installing towers, anchors, cables, and other construction equipment, utilizing a cable hoisting system for scaffold-free construction. However, for arch bridges located in the middle of a river, far from both banks, installing towers and anchors in the river is extremely costly, uneconomical, and difficult to construct.

[0006] The jacking construction method involves setting up a jacking platform on the shore, and then pushing the arch ribs and main beams forward into place after they are assembled. This method is fast, environmentally friendly, and has minimal impact on navigation, and has become increasingly popular in recent years. The "Method for Integral Pushing of Large-Tonnage Multi-Span Composite Arch Bridges with Arches" (Patent Application No. CN101793010) proposes an integral pushing method for arches. However, this method only temporarily connects the arch beams with struts. Hangers are installed after the pushing is complete. This method cannot effectively use the hangers to adjust the forces acting on the arch beams during the pushing process. It also prolongs the existence of temporary piers in the water, affecting flood control and navigation under the bridge. The "Integral Pushing Construction Method for Network-Tied Arch Bridges" (Patent Application No. 2011101028797) proposes a guide-beam-free integral pushing method for network-tied arch bridges. However, this scheme does not consider the adjustability of the hanger forces throughout the construction process. Furthermore, the guide-beam-free integral pushing method is costly for large-span bridges. Furthermore, during construction, the structure is time-varying, and its resistance is a random variable. The load also changes continuously with the construction progress. Using deterministic theory to guide construction makes it difficult to fully guarantee the safety of the structure. Therefore, current pushing construction methods have shortcomings for large-span arch bridges. Summary of the Invention

[0007] The purpose of the present invention is to provide a large-span composite arch bridge jacking construction method with adjustable construction status. The stress on the arch and beam during the jacking process is controlled within a reasonable range by using hangers and temporary struts, thereby reducing the number and existence time of temporary piers during the jacking process and reducing the impact on flooding and navigation under the bridge.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a large-span composite system arch bridge jacking construction method with adjustable construction status, characterized in that the method includes: setting up a jacking platform on land, assembling the steel arch, main beam, hanger and temporary struts connecting the steel arch and main beam into a beam-arch combination system on shore in advance, and initially tensioning the hanger. During the jacking process of the beam-arch combination system with the hanger and temporary struts, the tensioning force of the hanger is continuously adjusted to adapt to the changes in the system until the jacking is in place.

[0009] Furthermore, when assembling a beam-arch system, the main beam is assembled first, then the arch ribs are horizontally assembled on the top surface of the main beam and the arch ribs are put into place by vertical rotation. After the arch-beam connection is completed, the arch-beam hangers and temporary support rods are installed. After the main beam is assembled, the top surface of the main beam is used as an assembly platform for the arch, and the arch ribs are then put into place by vertical rotation, without the need to set up arch rib supports.

[0010] Furthermore, the hanger is pre-installed before the jacking begins, and the jacking is carried out with the hanger. During the jacking process, a functional function is constructed based on the stress limit of the component to determine the tensioning force of the hanger during the jacking process. By optimizing the tensioning force of the hanger, the construction state during the jacking process is adjusted to ensure the reliability of the entire process.

[0011] Furthermore, the temporary support rod is installed between the arch and the beam. The temporary support rod has sufficient rigidity and can be removed only after being pushed into place.

[0012] Furthermore, the overall jacking is to jack the arch, beam, hanger and temporary strut as a whole.

[0013] Furthermore, the method specifically includes the following steps:

[0014] Step 1:

[0015] (1) Erect the trestle and foundation construction platform structure, and set up temporary piers;

[0016] (2) Construction of foundation and pier body, construction of temporary piers in water for jacking, and construction of temporary supports for jacking on permanent piers;

[0017] (3) Steel beams and steel arch rib segments are processed in the factory and assembled on site;

[0018] (4) Set up arch beam assembly, jacking platform and lifting station, and adopt multi-point jacking.

[0019] Step 2:

[0020] (1) Assemble the steel main beam on the jacking platform;

[0021] (2) Assemble the arch ribs on the beams and rotate them vertically into place;

[0022] (3) Install temporary support rods between arches and beams, and initially tension the suspenders;

[0023] (4) Install the front guide beam for jacking;

[0024] (5) The arch-beam combination system is continuously pushed forward as a whole, and the reliability of the entire construction process is ensured by adjusting the tensioning force of the hanger.

[0025] Step 3:

[0026] (1) After the arch-beam combination system is pushed into place, remove the temporary support rods;

[0027] (2) Gradually dismantle temporary piers and assembly platforms;

[0028] (3) Adjust the tension of the boom cable.

[0029] Step 4:

[0030] (1) Construction of auxiliary structures;

[0031] (2) The entire bridge was completed.

[0032] The above-mentioned construction technology and temporary measures, due to the existence of permanent hangers and temporary struts, can ensure the common stress of the arch and beam during the jacking process, reduce the number of temporary piers in the water, and solve the key stress problem in the jacking construction of large-span composite arch bridges. This construction method adjusts the stress state of the overall jacking process of the composite arch bridge in real time by adjusting the tensioning force of the hangers, which ensures the cooperation between the arch and beam to a certain extent, improves the stress performance of the structure, reduces the number of temporary piers in the water and the number of temporary struts for the arch and beam, and reduces the complexity of the structural construction. It has high promotion value in terms of applicability, economy, construction quality, construction period, etc., and has pioneering significance for similar projects in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the pushing process.

[0034] Figure 2 For temporary pier arrangement.

[0035] Figure 3 This is the overall layout drawing of the main bridge.

[0036] Figure 4 This is the cross-sectional layout diagram of the main bridge. DETAILED DESCRIPTION

[0037] The following, combined with the accompanying drawings and specific examples, further details the proposed method for jacking construction of a large-span composite arch bridge with adjustable construction conditions. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clarify the illustration of the present invention.

[0038] Combine Figures 1 to 4 The present invention describes the jacking construction method of a large-span composite arch bridge with adjustable construction status. The main process is as follows: a jacking platform 7 is set up on land, the main beam 2 is first assembled, and then the arch rib 1 is horizontally assembled on the top surface of the main beam and the arch rib is put into place by vertical rotation. After the arch-beam connection is completed, the hangers 4 and temporary struts 3 are installed between the arch and the beam, and the combined arch bridge with the hangers 4 and temporary struts 3 is jacked as a whole. During the jacking process, the tension of the hangers is continuously adjusted to adapt to the changes in the system until the jacking is in place.

[0039] Using a specific bridge as a background project, the specific implementation steps are described. This bridge is a lattice-type tied-arch bridge with a span of (95m + 280m) + 420m + (280m + 95m). The 420m span has a rise-to-span ratio of 1 / 6, a rise of 70m, and an inclination of 3.5°. The 280m span also has a rise-to-span ratio of 1 / 6, a rise of 46.67m, and an inclination of 5.3°. The arch ribs utilize pentagonal steel box sections. The cross-links of the arch ribs are formed using straight braces with octagonal steel box sections. The hangers are arranged in a lattice pattern, with a standard spacing of 9m on the main beams and an inclination of approximately 60° along the bridge. The main beams utilize orthotropic composite deck beams with a beam height of 4.15m. The substructure utilizes pointed thin-walled piers, rectangular caps, and a bored cast-in-place pile foundation. The 95m + 280m span is continuous, while the 420m span is simply supported. Here we take a 420m simply supported span as an example to introduce the specific implementation method.

[0040] During the jacking construction, the bridge deck had not yet been laid, but the hangers between the arches and beams had already been installed and initially tensioned, forming a combined arch-beam system. Temporary braces were also installed between the arches and beams, giving the arch bridge the characteristics of a truss bridge during the jacking process and improving its mechanical properties. Two temporary piers 8 were installed at the 420m span, with 45m-long front and rear jacking guide beams 5 and 6, respectively, installed at the front and rear ends of the jacking process. Jacking equipment was installed at the tops of each permanent and temporary pier, and construction was carried out using multi-point jacking.

[0041] The detailed construction steps of this bridge are as follows:

[0042] Step 1:

[0043] (1) Erect the trestle and foundation construction platform structure, and set up temporary piers;

[0044] (2) Construction of foundation and pier body, construction of temporary piers in water for jacking, and construction of temporary supports for jacking on permanent piers;

[0045] (3) Steel beams and steel arch rib segments are processed in the factory and assembled on site;

[0046] (4) Set up arch beam assembly, jacking platform and lifting station, and adopt multi-point jacking.

[0047] Step 2:

[0048] (1) Assemble the steel main beam on the jacking platform;

[0049] (2) Assemble the arch ribs on the beams and rotate them vertically into place;

[0050] (3) Install temporary support rods between arches and beams, and initially tension the suspenders;

[0051] (4) Install the guide beam for jacking;

[0052] (5) Carry out continuous jacking construction on the entire arch-beam combination system and adjust the tensioning force of the hanger.

[0053] Step 3:

[0054] (1) After the 420m span arch beam combination system is pushed to Figure 2 When it is in the position shown, remove the guide beam and continue pushing it into place;

[0055] (2) Remove some temporary support rods of the main arch;

[0056] (3) Tensioning part of the suspender;

[0057] (4) Remove the remaining temporary support poles;

[0058] (5) Tension the remaining hangers.

[0059] Step 4:

[0060] (1) Gradually dismantle temporary piers and assembly platforms;

[0061] (2) Adjust the tension of the boom cable.

[0062] Step 5:

[0063] (1) Laying prefabricated bridge deck;

[0064] (2) Pour concrete wet joints in sections from the mid-span to the arch foot.

[0065] Step 6:

[0066] (1) Construction of auxiliary structures;

[0067] (2) The entire bridge was completed.

[0068] During bridge construction, various influencing factors are not deterministic variables but rather have a range of variation. This results in a random process for the entire structural state. The structure may become reliable or fail with a certain probability, and using deterministic theories to guide construction has certain limitations. Therefore, based on stochastic finite element theory to calculate the reliability of the entire construction process, a method suitable for adjusting the construction state of composite tied-arch bridges has been developed. This method constructs a functional function based on component stress limits and calculates the hanger tension force at each jacking stage with the goal of ensuring that the structural reliability meets design requirements, thus achieving adjustable construction state.

[0069] Assume that the performance function of the i-th construction stage can be expressed as Z=R﹣S,Where Z is the function of the construction phase, Z>0 represents structural safety, and Z<0 represents structural failure. R is the allowable stress value of the corresponding material, taking into account the uncertainty of material properties, geometric parameters, and calculation model. S is the maximum stress of the cross section of the key component obtained by calculation. It is an implicit function with construction phase loads such as hanger tension, jacking force, dead load, and wind load as design variables. Based on this, the probability of Z>0 during the construction process is calculated and converted into a structural reliability index. Under the condition that the construction phase reliability meets the design requirements, the hanger tension force of construction phase i is calculated. The specific implementation process is as follows:

[0070] (1) Determine the loads acting during the jacking process, and determine the magnitude and statistical characteristics of the suspender tension, jacking force, gravity, and other acting loads based on on-site measurement results;

[0071] (2) Based on the material parameters provided by the steel structure processing plant and combined with the experimental research results, the statistical characteristics of factors such as the material strength and cross-sectional dimensions of the steel box girder and steel arch rib are determined, and a probabilistic statistical model of the resistance R is established;

[0072] (3) Determine the statistical law based on the on-site boom force measurement results, and calculate the magnitude of the stress in each key section and its probability distribution model based on the statistical model of the boom tension force, the load acting during the jacking process, and the material parameters;

[0073] (4) The reliability index of the main beam and arch rib during each jacking process is calculated using random finite element theory. The tensioning force of the hanger in each jacking stage is calculated with the reliability index greater than 4.7 as the target, so as to guide the construction.

[0074] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for jacking construction of a large-span composite arch bridge with adjustable construction status, characterized in that The construction method includes: setting up a jacking platform on land, assembling the steel arch, main beam, hanger and temporary struts connecting the steel arch and main beam into a beam-arch combination system on shore in advance, and initially tensioning the hanger. During the jacking process of the beam-arch combination system with the hanger and temporary struts, the tensioning force of the hanger is continuously adjusted to adapt to the changes in the system until the jacking is in place.

2. The method for jacking construction of a large-span composite arch bridge with adjustable construction status according to claim 1 is characterized by: When assembling a beam-arch combination system, first assemble the main beam, then assemble the arch ribs horizontally on the top surface of the main beam and put the arch ribs into place by vertical rotation. After the arch-beam connection is completed, install the hangers and temporary support rods between the arch and beam.

3. The method for jacking construction of a large-span composite arch bridge with adjustable construction status according to claim 1 is characterized by: During the jacking process, a functional function is constructed based on the component stress limit to determine the hanger tensioning force during the jacking process. By optimizing the hanger tensioning force, the construction status during the jacking process is adjusted to ensure the reliability of the entire process.

4. The method for jacking construction of a large-span composite arch bridge with adjustable construction status according to claim 1, characterized in that: Temporary struts are supported between the main beam and the arch ribs and are removed after being pushed into place.

5. The method for jacking construction of a large-span composite arch bridge with adjustable construction status according to claim 1 is characterized in that The construction method includes the following steps: Step 1: (1) Erect the trestle and foundation construction platform structure, and set up temporary piers; (2) Construction of foundation and pier body, construction of temporary piers in water for jacking, and construction of temporary supports for jacking on permanent piers; (3) Steel beams and steel arch rib segments are processed in the factory and assembled on site; (4) Set up arch beam assembly, jacking platform, lifting station, and adopt multi-point jacking; Step 2: (1) Assemble the steel main beam on the jacking platform; (2) Assemble the arch ribs on the beams and rotate them vertically into place; (3) Install temporary support rods between arches and beams, and initially tension the suspenders; (4) Install the front guide beam for jacking; (5) Carry out continuous jacking construction on the entire arch-beam combination system, and ensure the reliability of the entire construction process by adjusting the tensioning force of the hanger; Step 3: (1) After the arch-beam combination system is pushed into place, remove the temporary support rods; (2) Gradually dismantle temporary piers and assembly platforms; (3) Adjust the suspender cable tension; Step 4: (1) Construction of auxiliary structures; (2) The entire bridge was completed.

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