Dumbbell-shaped steel pipe concrete arch rib and construction method thereof

Abstract

The present application provides a kind of dumbbell type steel pipe concrete arch rib, including two parallel upper circular steel tube and lower circular steel tube, the upper circular steel tube and lower circular steel tube are filled with concrete, between upper circular steel tube and lower circular steel tube, intermediate straight web and two sides concave arc web are connected, form left and right two abdominal cavity, abdominal cavity is filled with concrete.The present application provides a kind of dumbbell type steel pipe concrete arch rib and its construction method, its structure is reasonable and stress performance is good, construction is simple, can solve the current dumbbell type steel pipe concrete construction web burst, abdominal cavity concrete cannot use pressure injection and other problems.

Description

Technical Field

[0001] This invention relates to the field of bridge construction engineering technology, and in particular to a dumbbell-shaped steel-concrete composite arch rib and its construction method. Background Technology

[0002] Concrete-filled steel tube arch bridges possess numerous advantages, including high compressive strength, economic efficiency, aesthetic appeal, and ease of construction, leading to their widespread application in bridge engineering in my country. Currently, hundreds of concrete-filled steel tube arch bridges of various forms have been constructed in my country. The dumbbell-shaped arch rib is the most widely used type in concrete-filled steel tube arch bridges. It consists of an upper and lower circular steel tube concrete structure, a cavity formed by two straight webs connecting the upper and lower circular steel tube concrete structures, and concrete poured into the cavity. However, extensive engineering practice has shown that the existing dumbbell-shaped concrete-filled steel tube arch ribs are prone to bulging of the webs under the pressure of the concrete during the pressure pouring of the cavity. In severe cases, the welds at the connection between the webs and the steel tubes can crack, leading to a "cavity burst" accident. The main reason for this is the significant stress generated at the junction of the webs and the steel tubes during the pressure pouring of the concrete into the cavity.

[0003] Currently, the main technical measures to prevent bursting accidents during the injection of concrete into the abdominal cavity of dumbbell-shaped steel-concrete composite arch ribs include: 1. using steel sections to stiffen the web plates and adding tie rods between the web plates; 2. adding partitions within the abdominal cavity to divide it into compartments, and then injecting concrete into each compartment separately. These methods are complex in construction and have limited effectiveness. Furthermore, the concrete in the abdominal cavity still cannot be pressure-injected, resulting in low construction efficiency and unreliable concrete compaction. Due to the limitations of existing technology, my country's "Design Code for Highway Steel-Concrete Composite Arch Bridges" stipulates that when calculating the main arch of a dumbbell-shaped steel-concrete composite arch, the concrete in the abdominal cavity is not included in the stress on the main arch section; only its self-weight is considered. This means that the strength of the concrete in the abdominal cavity is not utilized during design, leading to material waste and affecting the economic efficiency of steel-concrete composite arch bridges. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a dumbbell-shaped steel-tube concrete arch rib and its construction method. This rib has a reasonable structure, good load-bearing performance, and is easy to construct. It solves problems such as web bursting and the inability to use pressure grouting for the concrete within the web cavity in current dumbbell-shaped steel-tube concrete construction. To achieve this objective:

[0005] This invention provides a dumbbell-shaped steel tube concrete arch rib, comprising two parallel upper and lower circular steel tubes, both of which are filled with concrete. A straight web in the middle and two concave arc-shaped webs on both sides are connected between the upper and lower circular steel tubes to form two abdominal cavities, both of which are filled with concrete.

[0006] As a further improvement of the present invention, the straight web plate is provided with round holes at certain intervals, so that the left and right abdominal cavities can be connected by opening the round holes.

[0007] As a further improvement of the present invention, the cross-section of the arc-shaped web is circular arc-shaped, and the sag-to-span ratio f / L of the arc-shaped web cross-section is about 1 / 10, which can ensure the stress of the arc-shaped web, its welding with the upper and lower circular steel pipes, and the space for pouring concrete inside the web cavity.

[0008] As a further improvement of the present invention, the concrete filling the abdominal cavity is filled by pressure injection, which can ensure that the concrete filling is dense.

[0009] This invention provides a construction method for dumbbell-shaped steel-tube concrete arch ribs, the specific steps of which are as follows:

[0010] a. Weld a straight web plate between the upper and lower round steel pipes;

[0011] b. Weld the arc-shaped webs on both sides to form hollow steel pipe arch ribs;

[0012] c. The hollow steel pipe arch ribs are erected in sections on the construction site until the hollow steel pipe arch ribs are closed.

[0013] d. According to the grouting sequence determined by the loading calculation, complete the injection of concrete into the upper circular steel pipe and the lower circular steel pipe respectively;

[0014] e. After the concrete inside the upper and lower circular steel pipes reaches the design strength, inject concrete into the abdominal cavity;

[0015] f. Once the concrete in the abdominal cavity reaches its strength, the construction of the dumbbell-shaped steel tube concrete arch rib is completed.

[0016] The present invention has the following advantages over the prior art:

[0017] 1. The concave arc-shaped webs on both sides form an arch-like stress pattern, which greatly reduces the stress generated when pouring concrete into the web cavity and solves the problem of web bursting in the current dumbbell-shaped steel tube concrete construction.

[0018] 2. The concrete inside the abdominal cavity can be pressure-injected, which can significantly improve construction efficiency and reduce construction difficulty.

[0019] 3. Pressure grouting of concrete within the abdominal cavity helps ensure compactness, allowing the strength of the concrete within the abdominal cavity to be utilized during the design phase, thus improving material utilization and structural load-bearing capacity.

[0020] 4. The concave arc-shaped webs on both sides and the upper and lower circular steel tubes act as a constrictor for the concrete in the abdominal cavity, thereby increasing the compressive strength of the concrete in the abdominal cavity.

[0021] 5. The two side webs are made of concave arc-shaped steel plates, and the dumbbell-shaped arch ribs have a more aesthetically pleasing appearance. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the dumbbell-shaped steel tube concrete arch rib of the present invention.

[0023] Figure 2 This is a schematic elevation view of the middle straight web of the present invention;

[0024] Figure 3 This is a schematic diagram showing the stress on the two arc-shaped webs during the intra-abdominal concrete pouring of the present invention.

[0025] Figure 4 This is a schematic diagram showing the force balance of the web plate at the upper and lower circular steel pipes during the intracavitary concrete pouring of the present invention.

[0026] Figure 5 This is a schematic diagram of the constraint stress on the concrete inside the abdominal cavity of the present invention.

[0027] Figure 6 The example diagram shows the finite element model of the original bridge arch foot section A.

[0028] Figure 7 The following is a finite element model diagram of the arch foot segment model B according to the improved version of the present invention;

[0029] Figure 8 The example diagram shows the finite element model of the arch foot section with thickened web of the original bridge.

[0030] Figure 9 The stress contour plot and deformation plot magnified 20 times are shown for model A when the intra-abdominal pressure is 1.1 MPa.

[0031] Figure 10 The stress contour plot and deformation plot magnified 20 times are shown for model B when the intra-abdominal pressure is 1.1 MPa.

[0032] Figure 11 The stress contour plot and deformation plot magnified 20 times are shown for model C when the intra-abdominal pressure is 1.1 MPa.

[0033] Figure 12 A comparison curve of the maximum stress at the web weld points of Model A and Model B under different intra-abdominal pressures;

[0034] Figure 13 A comparison curve of the maximum stress at the web weld points of Model B and Model C under different intra-abdominal pressures;

[0035] Figure 14 A comparison curve of the maximum deformation at the 1 / 2 height point of the lateral abdominal plate of Model A and Model B under different intra-abdominal pressures;

[0036] Figure 15 The figure shows a comparison of the maximum deformation at the half-height point of the lateral web of models B and C under different intra-abdominal pressures. The figures are labeled as follows: 1. Upper circular steel tube; 2. Lower circular steel tube; 3. Arc-shaped web; 4. Straight web; 5. Upper circular steel tube filled with concrete; 6. Lower circular steel tube filled with concrete; 7. Intra-abdominal cavity filled with concrete; 8. Circular hole in straight web. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0038] This invention provides a dumbbell-shaped steel tube concrete arch rib and its construction method. It has a reasonable structure, good stress performance, and is easy to construct. It can solve the problems of web bursting and inability to use pressure grouting for concrete in the abdominal cavity in the current construction of dumbbell-shaped steel tube concrete.

[0039] The invention provides the following: Figure 1 The dumbbell-shaped steel-concrete arch rib shown includes two parallel upper circular steel pipes 1 and lower circular steel pipes 2. Both the upper circular steel pipes 1 and lower circular steel pipes 2 are filled with concrete. A straight web plate 4 in the middle and two concave arc-shaped web plates 3 on both sides are connected between the upper circular steel pipes 1 and lower circular steel pipes 2 to form two abdominal cavities, both of which are filled with concrete.

[0040] The straight web 4 described in this application is as follows: Figure 2 As shown, there are circular holes at certain intervals, which connect the left and right abdominal cavities.

[0041] The cross-section of the arc-shaped web 3 described in this application is as follows: Figure 3 As shown, the arc-shaped web has a span-to-span ratio f / L of approximately 1 / 10, which ensures the stress on the arc-shaped web, its welding with the upper and lower circular steel pipes, and the space for pouring concrete into the web cavity.

[0042] The concrete filling the abdominal cavity described in this application is filled by pressure injection, which ensures that the concrete filling is dense.

[0043] The construction method for producing the dumbbell-shaped steel tube concrete arch rib described in this application includes the following specific steps:

[0044] a. Weld an intermediate straight web plate 4 between the upper round steel pipe 1 and the lower round steel pipe 2;

[0045] b. Weld the arc-shaped web plates 3 on both sides to form hollow steel pipe arch ribs;

[0046] c. The hollow steel pipe arch ribs are erected in sections on the construction site until the hollow steel pipe arch ribs are closed.

[0047] d. According to the grouting sequence determined by the loading calculation, the concrete filling 5 in the upper circular steel pipe and the concrete filling 6 in the lower circular steel pipe are respectively completed by injection.

[0048] e. After the concrete inside the upper and lower circular steel pipes reaches the design strength, inject 7% concrete into the abdominal cavity;

[0049] f. Once the concrete 7 inside the abdominal cavity reaches its strength, the construction of the dumbbell-shaped steel tube concrete arch rib is completed.

[0050] The stress diagram of the two arc-shaped webs on both sides of the dumbbell-shaped steel tube concrete arch rib during the pouring of concrete into the abdominal cavity is shown in the figure below. Figure 3 As shown in the diagram, the force balance diagram of the web plate at the upper and lower circular steel pipes is as follows. Figure 4 As shown, during the pouring of concrete into the abdominal cavity, the concrete exerts outward horizontal pressure on the two side webs. When the two side webs are straight, the stress mode is that of a plate fixed at both sides bearing the bending moment, with the junction of the web and the steel pipe being the fixed edge of the plate. Due to the thinness of the plate and its low bending stiffness, a large bending stress is generated at the junction of the web and the steel pipe, leading to a bursting accident. In this invention, the two side webs are made of concave arc-shaped plates, and their stress mode becomes an arch mainly bearing in-plane axial force. The thrust of the arch is transmitted to the upper and lower circular steel pipes at both ends and the concrete filling the steel pipes, and then converted into the tensile force of the middle web, achieving self-balance. The arch stress mode can greatly reduce the stress of the arc-shaped web, thereby avoiding the occurrence of bursting accidents.

[0051] When the concrete within the abdominal cavity reaches its strength and bears pressure, the concave arc-shaped webs on both sides and the upper and lower circular steel tubes further constrain the lateral deformation of the concrete within the abdominal cavity, acting as a clamp. A schematic diagram of the constrained stress on the concrete within the abdominal cavity is shown below. Figure 5 As shown, this can improve the compressive strength of the concrete in the abdominal cavity.

[0052] The invention will be further described in detail below using a specific through-type steel-concrete composite arch bridge as an example. This bridge employs a rigid tied arch with a span of 130m. The arch axis is a quadratic parabola with a rise-to-span ratio of 1 / 5. The arch ribs are dumbbell-shaped steel-concrete composite tubes, with the outer diameter of the upper and lower circular steel tubes being 110cm, a center-to-center distance of 150cm, a total section height of 260cm, and a web spacing of 60cm. All the upper and lower circular steel tubes and the webs are made of Q345C steel with a wall thickness of 14mm, and are filled with C50 micro-expansion concrete.

[0053] The concrete in the cavity of this bridge is injected from the arch foot to the arch crown. Considering the static pressure of the concrete and the frictional resistance between the concrete and the steel plate in the cavity during the injection process, based on experience, the maximum pressure of the concrete in the cavity at the grout inlet of this project is estimated to be 1.1 MPa.

[0054] A finite element model of a 5m long arch foot section was established using the spatial finite element program ANSYS. Outward pressure was applied to the web plate step by step, and the relationship between the stress and deformation of the web plate and the pressure of the pumped concrete in the web plate during the injection of concrete into the web cavity was analyzed.

[0055] Finite element models were established for three different cases based on the different structures of the web:

[0056] Model A: Uses the original bridge's two 14mm thick straight webs, such as... Figure 6 As shown;

[0057] Model B: According to the present invention, a straight web is provided in the middle, and a concave arc-shaped web is provided on each side. The thickness of the web is 14mm. The sag-to-span ratio of the arc-shaped web is 1 / 10. The welding positions of the arc-shaped webs on both sides to the upper and lower circular steel pipes are consistent with the straight web of the original bridge. Figure 7 As shown;

[0058] Model C: The thickness of the two straight webs of the original bridge is changed to 19mm, and the total steel consumption of the webs is the same as that of Model B, such as... Figure 8 As shown.

[0059] Based on the finite element analysis results, the maximum stress values ​​(unit: MPa) at the web weld points of each model under different intra-abdominal pressures are shown in the table below:

[0060] Intra-abdominal pressure / MPa 0.4 0.5 0.6 0.8 1.0 1.1 Model A 256.4 320.5 384.7 370.5 390.6 375.3 Model B 68.6 85.7 102.8 137.1 171.4 188.6 Model C 150.3 187.9 225.5 300.6 375.8 413.3 Intra-abdominal pressure / MPa 1.2 1.4 1.6 1.8 2.0 2.2 Model A - - - - - - Model B 205.7 240.0 274.3 308.6 342.9 377.2 Model C 413.3 395.1 405.0 391.7 379.9 376.4

[0061] The results in the table above show that: Model A reached yield at the web weld point when the intra-abdominal pressure was only 0.6 MPa, Model C reached yield at the web weld point when the intra-abdominal pressure was 1.0 MPa, while Model B only approached yield when the intra-abdominal pressure reached 2.0 MPa.

[0062] Based on the finite element analysis results, the maximum stress values ​​(unit: MPa) at the weld seam of the middle straight web of model B under different intra-abdominal pressures are shown in the table below:

[0063] Intra-abdominal pressure / MPa 0.4 0.5 0.6 0.8 1.0 1.1 Model B 65.3 81.6 98.0 130.6 163.2 179.6 Intra-abdominal pressure / MPa 1.2 1.4 1.6 1.8 2.0 2.2 Model B 192.9 219.6 246.3 273.0 299.7 326.4

[0064] The results in the table above show that the maximum stress in the middle straight web of model B is less than the maximum stress in the two curved webs, and it has not yet reached yield when the intra-abdominal pressure reaches 2.2 MPa.

[0065] Based on the finite element analysis results, the maximum deformation (unit: mm) at the lateral abdominal plate half-height point of each model under different intra-abdominal pressures is shown in the following table:

[0066] Intra-abdominal pressure / MPa 0.4 0.5 0.6 0.8 1.0 1.1 Model A 2.52 3.15 3.78 5.46 8.83 13.4 Model B 0.59 0.74 0.88 1.18 1.47 1.62 Model C 1.03 1.29 1.55 2.07 2.58 2.84 Intra-abdominal pressure / MPa 1.2 1.4 1.6 1.8 2.0 2.2 Model A - - - - - - Model B 1.77 2.06 2.35 2.65 2.94 3.24 Model C 3.34 4.02 4.8 5.96 8.48 48.61

[0067] The results in the table above show that, under the same intra-abdominal pressure, the outward deformation value at the half height point of the lateral abdominal plate of model A is about 4 times that of model B, and the outward deformation value at the half height point of the lateral abdominal plate of model C is about 2 times that of model B. Moreover, the multiple increases with the increase of intra-abdominal pressure, and suddenly increases sharply after reaching the critical pressure.

[0068] The stress contour plots and 20x magnified deformation plots of models A, B, and C at an intra-abdominal pressure of 1.1 MPa are shown below. Figure 9 , Figure 10 , Figure 11 As shown in the figure. The maximum stress comparison curves of the web weld points of Model A and Model B under different intra-abdominal pressures are as follows. Figure 12 As shown; the maximum stress comparison curves of the web weld points of models B and C under different intra-abdominal pressures are as follows. Figure 13 As shown; the maximum deformation comparison curves of the lateral abdominal plate at half height point under different intra-abdominal pressures for models A and B are as follows. Figure 14 As shown; the maximum deformation comparison curves of the lateral abdominal plate at half height point under different intra-abdominal pressures for models B and C are as follows. Figure 15 As shown.

[0069] Based on the above analysis, the following conclusions can be drawn:

[0070] 1. The dumbbell-shaped steel-concrete composite arch ribs of the original bridge had already yielded at the web weld points when the pressure inside the abdominal cavity was only 0.6 MPa, which could not meet the requirement of 1.1 MPa pressure when injecting concrete into the abdominal cavity.

[0071] 2. The dumbbell-shaped steel tube concrete arch rib of the present invention can significantly reduce the stress in the web plate during the injection of concrete into the abdominal cavity. It only approaches yielding when the pressure in the abdominal cavity reaches 2.0 MPa, which fully meets the requirements of the concrete injection into the abdominal cavity and has a large margin.

[0072] 3. When the thickness of the straight web of the original bridge is increased to make the amount of steel used the same as that of the present invention, the weld points of the web plate of the dumbbell-shaped steel tube concrete arch rib reach yield when the pressure in the abdominal cavity is 1.0MPa, which cannot meet the requirements of intracavitary injection of concrete.

[0073] 4. The dumbbell-shaped steel tube concrete arch rib of the present invention can significantly improve the out-of-plane stiffness of the web plates on both sides, and significantly reduce the outward deformation of the web plates during the injection of concrete into the web cavity.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A dumbbell-shaped steel-concrete arch rib, comprising two parallel upper circular steel pipes (1) and lower circular steel pipes (2), characterized in that: The upper round steel pipe (1) and the lower round steel pipe (2) are both filled with concrete. A straight web plate (4) in the middle and an arc-shaped web plate (3) on both sides are connected between the upper round steel pipe (1) and the lower round steel pipe (2) to form two abdominal cavities, both of which are filled with concrete. The straight web (4) has round holes at certain intervals; The cross-section of the arc-shaped web (3) is arc-shaped, and the span-to-span ratio f / L of the arc-shaped web (3) is about 1 / 10. The concrete filling the abdominal cavity is filled by pressure injection.

2. The construction method of the dumbbell-shaped steel-concrete arch rib according to claim 1 is as follows, characterized in that: a. Weld an intermediate straight web plate (4) between the upper round steel pipe (1) and the lower round steel pipe (2); b. Weld the arc-shaped webs (3) on both sides to form hollow steel pipe arch ribs; c. The hollow steel pipe arch ribs are erected in sections on the construction site until the hollow steel pipe arch ribs are closed. d. According to the grouting sequence determined by the loading calculation, the concrete filling (5) in the upper circular steel pipe and the concrete filling (6) in the lower circular steel pipe are respectively injected. e. After the concrete inside the upper and lower circular steel pipes reaches the design strength, inject concrete into the abdominal cavity (7); f. Once the concrete in the abdominal cavity (7) reaches its strength, the construction of the dumbbell-shaped steel tube concrete arch rib is completed.

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