Combined arch rib of circular-ended concrete-filled steel tube with slightly curved web plates and construction method

Abstract

The present invention discloses a micro-bent wall plate type concrete-filled circular-ended steel pipe composite arch rib and a construction method. This application consists of a main arch rib, a core concrete layer filled in the main arch rib, auxiliary arch ribs, and several connecting rods for the main arch rib and the auxiliary arch ribs; the axis of the main arch rib is parabolic, the axes of the two auxiliary arch ribs are circular arc-shaped, and the two auxiliary arch ribs are both inclined and symmetrically arranged on both sides of the main arch rib. The two arch feet of the auxiliary arch ribs are respectively fixedly connected to the two arch feet of the main arch rib. The two auxiliary arch ribs have the same structure, and the two auxiliary arch ribs are higher than the main arch rib. The main arch rib and the auxiliary arch ribs are fixedly connected by connecting rods except at the arch feet; the main arch rib is a micro-bent wall plate type concrete-filled circular-ended steel pipe, and the main arch rib is fixedly connected by enclosing an outwardly convex semi-circular upper wall plate, an outwardly convex semi-circular lower wall plate, and two inwardly micro-bent side wall plates. The structure of the present invention is stable and the construction is safe.

Description

Technical Field

[0001] The present invention relates to the technical field of construction devices, and particularly relates to a concrete-filled steel tube composite arch rib with a micro-bent wall plate and a circular end shape and a construction method thereof. Background Art

[0002] The concrete-filled steel tube composite arch rib is a new type of bridge structure. Bridges of this type that have been built include the Zhangzhou Jiulongjiang Bridge, etc. The self-weight of this type of bridge is reduced by about 50% compared with concrete beam bridges of the same span. While increasing the bridge's spanning ability, it can also reduce the engineering quantity of the bridge's lower structure, and the bridge's appearance is as beautiful as a crescent moon. Therefore, this bridge type has good development prospects.

[0003] Currently, the concrete-filled steel tube composite arch rib generally consists of a steel tube main arch rib, a core concrete layer, a steel tube secondary arch rib, and connecting rods. The main arch rib uses a circular steel tube or a circular-end steel tube, the secondary arch rib uses a circular steel tube, the connecting rods use a circular or rectangular steel tube, and the core concrete uses self-compacting and slightly expanding concrete. The main arch rib can use a vertical circular-end steel tube or a horizontal circular-end steel tube. Among them, the vertical circular-end steel tube has greater flexural stiffness in the arch plane and is more beautiful. However, when the main arch rib uses a circular-end steel tube with an aspect ratio greater than 1.6 and a relatively thin side wall plate, local instability of the side wall plate of the circular-end steel tube may occur during the injection process of the core concrete. To avoid the instability and deformation of the side wall plate of the circular-end steel tube, annular stiffening rib plates or side wall plate tie bars are usually added to the inner surface of the circular-end steel tube. However, the stiffening ribs or tie bars inside the steel tube not only increase the manufacturing difficulty of the steel tube and prolong the construction period, but also increase the wall friction resistance during the injection of the core concrete. According to engineering experience, each group of annular stiffening rib plates can cause a concrete pump pressure loss of about 0.2 MPa. Therefore, more internal stiffening structures in the steel tube significantly increase the concrete injection pump pressure, which also indirectly increases the risk of deformation or rupture of the steel tube wall plate during construction. In addition, adding more stiffening ribs or tie bars inside the steel tube is also likely to cause incomplete compaction of the concrete during pouring, and it is difficult to ensure the construction quality of the concrete-filled steel tube arch rib, thus leaving potential structural safety hazards.

[0004] Of course, in order to improve the compaction degree of the core concrete layer and reduce the pump pressure during the injection of the core concrete, there are also construction cases where the core concrete is continuously injected in sections. However, the construction process is complex, increasing the construction control difficulty, and the injection quality is not as high as that of a one-time continuous injection.

[0005] In summary, it is necessary to improve the structural design of the circular-end concrete-filled steel tube arch rib, optimize the stiffening method of the circular-end steel tube wall plate on the premise of ensuring the stability of the wall plate during the injection of the core concrete into the circular-end steel tube, and design a new type of circular-end concrete-filled steel tube arch rib and construction method that can increase the stability of the circular-end steel tube wall plate and reduce the friction resistance on the inner surface of the circular-end steel tube. Summary of the Invention

[0006] In order to make up for the deficiencies of the existing technology, the present invention provides a concrete-filled steel tubular composite arch rib with a micro-bent wall plate and a circular end shape and a construction method thereof.

[0007] The technical solution of the present invention is as follows:

[0008] A concrete-filled steel tubular composite arch rib with a micro-bent wall plate and a circular end shape is composed of a main arch rib, a core concrete layer filled in the main arch rib, two secondary arch ribs, and several connecting rods for connecting the main arch rib and the secondary arch ribs; the axis of the main arch rib is parabolic, the axes of the two secondary arch ribs are circular arc lines, and the two secondary arch ribs are both inclined and symmetrically arranged on both sides of the main arch rib. The two arch feet of the secondary arch ribs are respectively fixedly connected to the two arch feet of the main arch rib. The two secondary arch ribs have the same structure, and the two secondary arch ribs are higher than the main arch rib. Except at the arch feet, the main arch rib and the secondary arch ribs are fixedly connected by connecting rods; the main arch rib is a micro-bent wall plate type circular end steel pipe, and the main arch rib is fixedly connected by enclosing an outwardly convex semi-circular upper wall plate, an outwardly convex semi-circular lower wall plate, and two inwardly micro-bent side wall plates; the secondary arch rib is a circular hollow steel pipe, and the connecting rod is a rectangular hollow steel pipe.

[0009] Preferably, except at the arch feet, the main arch rib is fixedly connected to the connecting rod through the outer surfaces of its two inwardly micro-bent side wall plates; the arch feet of the secondary arch rib are fixedly connected to the inwardly micro-bent side wall plates at the arch feet of the main arch rib.

[0010] Preferably, the semi-circular upper wall plate and the semi-circular lower wall plate have the same structure and are symmetrically arranged; the two inwardly micro-bent side wall plates have the same structure and are symmetrically arranged.

[0011] Preferably, the inwardly micro-bent side wall plate is an inwardly micro-bent circular arc side wall plate. The calculation method of the bending rise of the inwardly micro-bent side wall plate includes the following steps:

[0012] S1: It is necessary to tentatively determine the wall thickness of the straight side wall plate type main arch rib model, the height and width of the longitudinal section of the main arch rib model through trial calculation. After calculating Ac and As from the wall thickness of the main arch rib model and the height and width values of the longitudinal section of the main arch rib model, verify through formula (1) to determine the parameter values that can make the normal section compressive bearing capacity of the main arch rib model meet the requirements of formula (1), and obtain the tentatively determined straight side wall plate type main arch rib model; where formula (1) is as follows:

[0013] γ0N d ≤0.9φ(f cd A c +f s A s ) (1)

[0014] In formula (1), γ0 is the structural importance coefficient; N dis the design axial compressive force of the main arch rib, N d is obtained by performing a structural stress analysis on the entire arch bridge using finite element software in the prior art; φ is the stability coefficient of axially compressed members, f cd is the design value of the compressive strength of the core concrete layer, f s is the design value of the compressive strength of the steel used for the main arch rib; A c is the cross-sectional area of the core concrete layer, and As is the sum of the cross-sectional areas of the upper wall panel of the semi-circular arc, the lower wall panel of the semi-circular arc, and the two straight side wall panels;

[0015] S2: Perform a deformation analysis of the proposed straight side wall panel type main arch rib model obtained in step S1 under the pumping action of self-compacting and slightly expanding concrete, and calculate the deformation amount of the straight side wall panel;

[0016] S3: Set the deflection deformation amount of the straight side wall panel calculated in step S2 in the reverse direction inward as the basic bending rise of the inwardly slightly bent side wall panel. Considering the impact dynamic action of the pumped concrete, and based on the sectional appearance design effect brought by the proportional coordination of the slightly bent rise and the width and height of the longitudinal section of the main arch rib model, magnify the basic bending rise as the design bending rise. At the same time, the slightly bent line type of the inwardly slightly bent side wall panel adopts a circular arc. Then, combine the wall thickness of the proposed straight side wall panel type main arch rib model obtained in step S1, the width and height of the longitudinal section of the proposed straight side wall panel type main arch rib model, and the design bending rise of the inwardly slightly bent side wall panel determined in step S3 to obtain the proposed slightly bent wall panel type round-ended steel pipe main arch rib;

[0017] S4: Perform a deformation analysis of the cross-section of the proposed slightly bent wall panel type round-ended steel pipe main arch rib again under the pumping action of concrete, and calculate the deformation value of the inwardly slightly bent side wall panel; then check whether the deformation value of the slightly bent wall panel is less than the allowable deflection value of the arched steel structure mainly under compression specified in the design code. The allowable deflection value is 1 / 400 of the arch span, and the arch span is the distance between the lower end of the upper wall panel of the semi-circular arc and the upper end of the lower wall panel of the semi-circular arc; if the deformation amount of the slightly bent wall panel is less than the allowable deflection value, then determine the cross-section design; otherwise, return to step S1 to modify the wall thickness or return to step S3 to increase the basic bending rise, and so on in a cycle until the deformation amount of the slightly bent wall panel of the proposed slightly bent wall panel type round-ended steel pipe main arch rib is less than the allowable deflection value.

[0018] Preferably, step S1 is specifically: According to the site conditions and the requirements of the design code, preliminarily determine the wall thickness of the main arch rib model, as well as the height and width of the longitudinal section of the main arch rib model. Among them, the structure of the main arch rib model is preliminarily determined to be a round-ended steel pipe structure enclosed by the upper wall panel of the semi-circular arc, the lower wall panel of the semi-circular arc, and the two straight side wall panels, and judge whether the wall thickness of the preliminarily determined main arch rib model, as well as the height and width of the longitudinal section of the main arch rib model, make the longitudinal section compressive bearing capacity of the main arch rib model meet the requirements of formula (1).

[0019] Preferably, step S2 is specifically as follows:

[0020] S2-1: Analyze the upper wall plate of the semi-circular arc, the lower wall plate of the semi-circular arc, and the two straight side wall plates of the main arch rib model under the pump pressure acting outward, and calculate the total loss of the injection pump pressure P; the total loss of the injection pump pressure P is calculated by Equation (2);

[0021] P = P v + P H + △P1 + △P2 (2)

[0022] In Equation (2), P v is the static pressure generated by the pumping height, P H is the frictional pressure loss along the way, △P1 is the pump pressure loss caused by the joint flange, and △P2 is the pump pressure loss caused by the sling conduit.

[0023] In this application, the static pressure P v generated by the pumping height is calculated by Equation (3):

[0024] P v = γ C * H (3)

[0025] In Equation (3), γ C is the unit weight of the self-compacting slightly expanding concrete, and H is the pumping height inside the main arch rib; the frictional pressure loss P H along the way is calculated by Equation (4):

[0026] P H = L△P H (4)

[0027] In Equation (4), L is the pumping length inside the main arch rib, and △P H is the frictional pressure loss per unit length;

[0028] The pump pressure loss △P1 caused by the joint flange is calculated by Equation (5):

[0029] △P1 = n1 * 0.2 (5)

[0030] In Equation (5), n1 is the number of joint flanges;

[0031] The pump pressure loss △P1 caused by the sling conduit is calculated by Equation (6):

[0032] △P2 = n2 * 0.2 (6)

[0033] In Equation (6), n2 is the number of sling conduits.

[0034] S2-2: Use the isolation method to separately take out the side wall plate for analysis. The side wall plate is simplified into a simply supported beam under uniformly distributed load, and the deflection deformation amount f of the side wall plate max is calculated by formula (7):

[0035] f max = 5qL 4 / 384EI (7)

[0036] In formula (7), q is the uniformly distributed load, that is, the pump pressure acting on the wall plate of the straight side wall plate type main arch rib model per unit length (i.e., 1 m) in the length direction of the main arch rib (i.e., the left - right direction shown), and the calculation formula of q is shown in formula (8); in formula (7), L is the distance between the lower end of the wall plate on the semi - circular arc and the upper end of the wall plate on the lower semi - circular arc, that is, the longitudinal height of the straight side wall plate, E is the elastic modulus of the steel used in the straight side wall plate type main arch rib model, and I is the moment of inertia of the cross - section resistance to bending of the wall plate of the straight side wall plate type main arch rib model; Figure 3 In the direction shown; the left - right direction) per unit length (that is, 1 m), which is the pump pressure acting on the wall plate of the straight side wall plate type main arch rib model. The calculation formula of q is as shown in formula (8); in formula (7), L is the distance between the lower end of the wall plate on the semi - circular arc and the upper end of the wall plate on the lower semi - circular arc, that is, the longitudinal height of the straight side wall plate, E is the elastic modulus of the steel used in the straight side wall plate type main arch rib model, and I is the moment of inertia of the cross - section resistance to bending of the wall plate of the straight side wall plate type main arch rib model;

[0037] q = P * 1 (8)

[0038] In formula (8), P is the total loss of the grouting pump pressure.

[0039] Preferably, in step S4, the calculation method of the total loss P of the grouting pump pressure is the same as that in step S2. Then, the inward - slightly - bent side wall plate is taken out by the isolation method for analysis. In step S4, the inward - slightly - bent side wall plate is simplified into a two - hinged arch under uniformly distributed load, and the crown deformation is solved by finite - element software to obtain the crown deformation value, that is, the deformation value of the inward - slightly - bent side wall plate.

[0040] Preferably, the distance between two adjacent connecting rods on the same side is 2 - 4 m.

[0041] Preferably, the secondary arch rib is made of circular hollow steel pipe, and the connecting rod is made of rectangular hollow steel pipe.

[0042] A construction method for a slightly - bent wall - plate - type round - ended concrete - filled steel - tube composite arch rib includes the following construction steps:

[0043] 1). Cut and process the upper wall plate on the semi - circular arc, the lower wall plate on the semi - circular arc, and the inward - slightly - bent side wall plate, and weld them to form the main arch rib segment; cut and process the connecting rod; cut and bend the secondary arch rib steel pipe;

[0044] 2). Weld - assemble the upper wall plate on the semi - circular arc, the lower wall plate on the semi - circular arc, and the two inward - slightly - bent side wall plates to form the main arch rib segment;

[0045] 3), Assemble and weld the main arch rib, connecting rod, and secondary arch rib outside the springing to form a segment of a slightly curved wall - type circular - ended steel pipe composite arch rib outside the springing; Assemble and weld the main arch rib, connecting rod, and secondary arch rib at the springing to form a segment of a slightly curved wall - type circular - ended steel pipe composite arch rib at the springing.

[0046] 4), Lift the segments of the slightly curved wall - type circular - ended steel pipe composite arch rib and assemble and weld them into a complete arch rib of the slightly curved wall - type circular - ended steel pipe composite arch rib. The springings of the complete arch rib are cast and fixed in the reinforced concrete arch seats fixedly arranged on the bridge deck.

[0047] 5), Inject self - compacting and slightly expanding concrete into the main arch rib through a concrete injection pipe to form a core concrete layer.

[0048] Preferably, in step 5), the specific technological steps of injecting self - compacting and slightly expanding concrete into the main arch rib through a concrete injection pipe are as follows: Open injection holes and exhaust and slurry - discharging holes on the main arch rib. The injection holes are fixedly connected to the concrete injection pipe, and the exhaust and slurry - discharging holes are fixedly connected to the exhaust and slurry - discharging pipe. The self - compacting and slightly expanding concrete is constructed by one - time continuous pump - pressure injection until the concrete discharged from the exhaust and slurry - discharging pipe is the same as the concrete injected through the concrete injection pipe, then the injection construction is completed; After the injection is completed, cut off the concrete injection pipe and the exhaust and slurry - discharging pipe, and weld steel plates on the injection holes and the exhaust and slurry - discharging holes to seal the injection holes and the exhaust and slurry - discharging holes.

[0049] Preferably, the injection holes are opened at a position 1 m from the bottom end of the springing of the main arch rib.

[0050] Preferably, the concrete injection pipe is located within the plane of the main arch rib and forms an angle of 30° with the main arch rib. In this application, the setting of the above - mentioned angle can make the concrete injection smoother, and can effectively reduce the impact of the injected concrete on the steel pipe wall plate and reduce the segregation of coarse and fine aggregates of the concrete.

[0051] Preferably, the exhaust and slurry - discharging holes are opened at the top of the main arch rib and are inclined along the transverse direction of the bridge. The above - mentioned setting can effectively ensure that the slurry overflows without polluting the main arch rib.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] In the circular - ended steel pipe concrete composite arch rib structure of the present invention, the upper and lower wall plates of the main arch rib are both semi - circular arc - shaped wall plates protruding outwards, and the side wall plates are all slightly curved inwards. Since there is an arch effect when the side wall plates are stressed, the local stability of the side wall plates is improved.

[0054] In addition, in this application, the connecting rod is made of a rectangular hollow steel pipe, and the connecting rod is welded to the outer side of the inwardly slightly curved side wall plate of the main arch rib. The connecting rod actually functions as an external stiffening rib for the inwardly slightly curved side wall plate of the main arch rib. Moreover, in this application, multiple connecting rods are welded and connected to the outer side of the inwardly slightly curved side wall plate of the main arch rib, which also reduces the compression length of the main arch rib.

[0055] In addition, since the connecting rod that functions as a stiffening rib in this application is fixedly connected to the outer side of the slightly curved wall plate of the main arch rib and is not arranged inside the main arch rib, therefore, this application can effectively avoid the problem that during the process of grouting concrete, due to the setting of structural measures such as stiffening plates inside the main arch rib, the flow resistance of the concrete is large, and it is necessary to increase the pressure of the pumped concrete, which in turn leads to an increase in the cross-sectional force of the main arch rib and causes local instability deformation or even damage of the main arch rib cross-section. The above setting in this application can provide a lower pump pressure during the construction of grouting the arch rib concrete, effectively reduce the pressure value on the side wall of the main arch rib, improve the stability and safety of the construction, improve the construction quality, and ensure the safety of the construction personnel during the construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is the side view of the slightly curved wall plate type circular-ended concrete-filled steel tubular combined arch rib of this application;

[0057] Figure 2 is Figure 1 the elevation view of;

[0058] Figure 3 is the top view of the slightly curved wall plate type circular-ended concrete-filled steel tubular combined arch rib of this application;

[0059] Figure 4 is the cross-sectional view of the slightly curved wall plate type circular-ended concrete-filled steel tubular combined arch rib of this application;

[0060] Figure 5 is the cross-sectional view of the main arch rib;

[0061] Figure 6 is the cross-sectional view of the connecting rod;

[0062] Figure 7 is the longitudinal cross-sectional schematic diagram of the straight side wall plate type main arch rib model;

[0063] Figure 8 is the force diagram of the straight side wall plate type main arch rib model;

[0064] Figure 9 is the simplified force diagram of the straight side wall plate;

[0065] Figure 10 is the schematic diagram of the deflection deformation occurred on the straight side wall plate;

[0066] Figure 11 is the simplified force diagram of the slightly curved side wall plate;

[0067] Figure 12 This is a sectional view of the micro-bent wall plate type circular-ended concrete-filled steel tube composite arch rib of the present application;

[0068] Figure 13 This is a schematic diagram of the connection relationship between the concrete injection pipe, the exhaust and slurry discharge pipe and the main arch rib.

[0069] In the figure: 1. Main arch rib; 1-1. Upper wall plate of the semi-circular arc; 1-2. Lower wall plate of the semi-circular arc; 1-3. Inwardly micro-bent side wall plate; 2. Auxiliary arch rib; 3. Connecting rod; 4. Core concrete layer; 5. Reinforced concrete arch seat; 6. Concrete injection pipe; 7. Exhaust and slurry discharge pipe. Specific embodiments

[0070] As Figures 1 to 12 shown, a micro-bent wall plate type circular-ended concrete-filled steel tube composite arch rib includes one main arch rib 1, a core concrete layer 4 filled in the main arch rib 1, two auxiliary arch ribs 2, and connecting rods 3 for connecting the main arch rib and the auxiliary arch ribs;

[0071] In this embodiment, the length of the main arch rib is 56 m, and the distance between two adjacent connecting rods on the same side (in terms of combination Figure 3 viewed, this same side refers to the front side or the rear side) is 2.2 m, and the number of connecting rods 3 on the same side is 17. Therefore, the total number of connecting rods 3 for connecting the main arch rib 1 and the two auxiliary arch ribs 2 is 34; moreover, among the 17 connecting rods 3 on the same side, one is used to connect the middle position of the main arch rib and the middle position of the auxiliary arch rib, and the other connecting rods 3 are symmetrically arranged on the left and right sides, as Figure 3 shown;

[0072] In this embodiment, the axis of the main arch rib 1 is parabolic, the axis of the auxiliary arch rib 2 is circular arc-shaped, the two auxiliary arch ribs 2 are both inclined and symmetrically arranged on both sides of the main arch rib 1. Among them, the auxiliary arch rib 2 is made of a circular hollow steel tube, and the connecting rod 3 is made of a rectangular hollow steel tube; in the present application, the two auxiliary arch ribs 2 are not connected to form an open triangular cross-section. In the present application, the two arch feet of each auxiliary arch rib 2 are respectively fixedly connected to the two arch feet of the main arch rib 1. The two auxiliary arch ribs 2 have the same structure, and the two auxiliary arch ribs 2 are both higher than the main arch rib 1. Except at the arch feet, the main arch rib 1 and the two auxiliary arch ribs 2 are fixedly connected by connecting rods 3. In addition, a core concrete layer 4 is also filled in the main arch rib 1, and the core concrete layer 4 is made of self-compacting and slightly expanding concrete;

[0073] In this embodiment, the main arch rib 1 is a circular-ended steel pipe with a slightly curved wall plate. Specifically, the main arch rib 1 is formed by welding and enclosing a semi-circular upper wall plate 1-1 protruding outward, a semi-circular lower wall plate 1-2 protruding outward, and two inwardly slightly curved side wall plates 1-3; the inwardly slightly curved side wall plates are circular arc side wall plates that are inwardly slightly curved. The structures of the two inwardly slightly curved side wall plates 1-3 are the same and are symmetrically arranged; while the semi-circular upper wall plate 1-1 and the semi-circular lower wall plate 1-2 have the same structure and are symmetrically arranged.

[0074] In this embodiment, the arc radius of the semi-circular upper wall plate is 500 mm, the arc radius of the semi-circular upper wall plate is 500 mm, the distance between the lower end of the semi-circular upper wall plate and the upper end of the semi-circular lower wall plate is 600 mm, and the bending rise of the inwardly slightly curved side wall plate is 1 / 15 of the distance between the lower end of the semi-circular upper wall plate and the upper end of the semi-circular lower wall plate, that is, the bending rise of the inwardly slightly curved side wall plate is 40 mm; in addition, in this application, except at the arch feet, the main arch rib 1 is fixedly connected to the connecting rod 3 through the outer surfaces of its two inwardly slightly curved side wall plates 1-3; the arch feet of the secondary arch rib 2 are fixedly connected to the inwardly slightly curved side wall plates 1-3 at the arch feet of the main arch rib 1; in this embodiment, the bending rise of the inwardly slightly curved side wall plate is specifically calculated and analyzed and determined by the following method. The calculation method of the bending rise of the inwardly slightly curved side wall plate includes the following steps:

[0075] S1: According to the site conditions and the requirements of the design code, preliminarily determine the wall thickness of the wall plate of the main arch rib model and the height and width of the longitudinal section of the main arch rib model (as Figure 7 shown), where the structure of the main arch rib model is preliminarily assumed to be a circular-ended steel pipe structure enclosed by a semi-circular upper wall plate, a semi-circular lower wall plate, and two straight side wall plates. The wall thickness of the preliminarily assumed main arch rib model and the height and width of the longitudinal section of the main arch rib model should make the longitudinal section compressive bearing capacity of the main arch rib model meet the requirements of formula (1):

[0076] γ0N d ≤0.9φ(f cd A c +f s A s ) (1)

[0077] In formula (1), γ0 is the structural importance coefficient; N d is the design axial pressure of the main arch rib, and N d is obtained by performing a structural force analysis on the entire arch bridge using finite element software in the prior art; φ is the axial compression stability coefficient, f cd is the design value of the compressive strength of the core concrete layer, f s is the design value of the compressive strength of the steel used for the main arch rib, and the three parameters φ, f cd , f cd are selected according to the design code; Ac is the cross-sectional area of the core concrete layer, and As is the sum of the cross-sectional areas of the upper semi-circular wall panel, the lower semi-circular wall panel, and the two straight side wall panels. Both Ac and As are obtained through calculation based on the wall thickness of the wall panel of the proposed main arch rib model and the height and width of the longitudinal section of the main arch rib model. The calculation method is prior art and will not be elaborated here. In this application, the hoop effect of the steel pipe on the core concrete layer is not considered safely during the verification.

[0078] In step S1, it is necessary to determine the wall thickness of the straight side wall panel type main arch rib model, the height and width of the longitudinal section of the main arch rib model through multiple attempts. After calculating Ac and As based on the wall thickness of the main arch rib model, the height and width of the longitudinal section of the main arch rib model, verify through formula (1), and finally determine the parameter values that can meet the requirements of formula (1) for the normal section compressive bearing capacity of the main arch rib model, and obtain the proposed straight side wall panel type main arch rib model. Specifically in this embodiment, the applicant found that when the height of the longitudinal section of the main arch rib model is 1600 mm, the width is 1000 mm, and the wall thickness of the main arch rib model, that is, the wall thicknesses of the upper semi-circular wall panel, the lower semi-circular wall panel, and the two straight side wall panels are all 24 mm, it is a set of parameter designs that meet formula (1).

[0079] S2: Conduct a deformation analysis of the proposed straight side wall panel type main arch rib model obtained in step S1 under the pumping action of self-compacting and slightly expanding concrete. The specific steps are as follows:

[0080] S2-1: Analyze the pumping force acting outward on the upper semi-circular wall panel, the lower semi-circular wall panel, and the two straight side wall panels of the main arch rib model, and calculate the total pumping pressure loss P; the total pumping pressure loss P is calculated through formula (2);

[0081] P = P v + P H + △P1 + △P2 (2)

[0082] In formula (2), P v is the static pressure generated by the pumping height, P H is the frictional pumping pressure loss, △P1 is the pumping pressure loss caused by the joint flange, and △P2 is the pumping pressure loss caused by the sling conduit.

[0083] In this application, the static pressure P v generated by the pumping height is calculated through formula (3):

[0084] P v = γ C * H (3)

[0085] In formula (3), γ C is the unit weight of the self-compacting and slightly expanding concrete, and H is the pumping height inside the main arch rib; the frictional pumping pressure loss PH , it is calculated by formula (4):

[0086] P H = LΔP H (4)

[0087] In formula (4), L is the pumping length in the main arch rib, and ΔP H is the frictional pressure loss per unit length;

[0088] The pressure loss ΔP1 caused by the joint flange is calculated by formula (5):

[0089] ΔP1 = n1 * 0.2 (5)

[0090] In formula (5), n1 is the number of joint flanges;

[0091] The pressure loss ΔP2 caused by the sling conduit is calculated by formula (6):

[0092] ΔP2 = n2 * 0.2 (6)

[0093] In formula (6), n2 is the number of sling conduits.

[0094] In this embodiment, the pumping height H is 10m, and the static pressure P generated by the pumping height v = γ C * H = 0.25MPa; The pumping length L in the main arch rib is 28m, and the frictional pressure loss ΔP per unit length H is 7.3 kPa / m, and the total frictional pressure loss P H = LΔP H = 0.065MPa; The pressure loss caused by each joint flange is 0.2MPa, and there are 4 joints in total. The pressure loss ΔP1 caused by 4 joint flanges is 0.8MPa; The pressure loss caused by each sling conduit is 0.2MPa, and there are 5 sling conduits in total. The pressure loss caused by the sling conduits is ΔP2 = 1.0MPa. Therefore, the total pressure loss P of the grouting pump in this embodiment = P v + P H + ΔP1 + ΔP2 = 2.115MPa.

[0095] S2-2: The side wall plate is separately taken out for analysis by the free body method. The side wall plate is simplified as a simply supported beam under uniformly distributed load, and the deflection deformation f of the side wall plate max is calculated by formula (7):

[0096] f max = 5qL 4 / 384EI (7)

[0097] In formula (7), q is the uniformly distributed load, that is, in the direction of the main arch rib length (i.e., alongFigure 3 The pressure of the pump acting on the wall panel of the main arch rib model with straight side wall panels (in the left - right direction shown) per unit length (i.e., 1m) is considered. The calculation formula of q is shown in formula (8); in formula (7), L is the distance between the lower end of the wall panel on the semi - circular arc and the upper end of the lower wall panel of the semi - circular arc, that is, the longitudinal height of the straight side wall panel, E is the elastic modulus of the steel used in the main arch rib model with straight side wall panels, and I is the flexural moment of inertia of the wall panel of the main arch rib model with straight side wall panels.

[0098] q = P * 1 (8)

[0099] In formula (8), P is the total loss of the grouting pump pressure.

[0100] In this embodiment, the value of L is 600mm; the value of E is 2.06×10 5 MPa, and the value of I is 1152000mm 4 ; since 1MPa = 1000KN / m 2 , therefore, in this embodiment, q = 2115kN / m 2 *1m = 2115kN / m; finally, substituting the above specific values of q, L, E, and I into formula (7) for calculation, the deflection deformation of the straight side wall panel is obtained as 15mm.

[0101] S3: Set the deflection deformation of the straight side wall panel calculated in step S2 in the reverse inward direction as the basic bending rise of the inward - slightly - bent side wall panel. Considering the impact dynamic effect of the grouted concrete and according to the sectional appearance design effect brought by the proportional coordination of the micro - bending rise with the width and height of the longitudinal section of the main arch rib model, the basic bending rise is enlarged as the design bending rise, that is, the value of the design bending rise is greater than 15mm. At the same time, the micro - bending line type of the inward - slightly - bent side wall panel adopts a circular arc. Then, with the wall panel thickness of the main arch rib model with straight side wall panels obtained in step S1, the width and height of the longitudinal section of the main arch rib model with straight side wall panels, and the design bending rise of the inward - slightly - bent side wall panel determined in step S3, a proposed micro - bent wall - type circular - ended steel pipe main arch rib can be obtained.

[0102] S4: Analyze the deformation of the cross-section of the proposed circular-ended steel pipe main arch rib with a micro-bent web plate under the pumping action of grouted concrete again. The analysis method is carried out according to step S2. Specifically, in this step S4, the calculation method of the total loss P of the grouting pump pressure is the same as that in step S2. Then, the isolation method is also used to take out the inward micro-bent side wall plate for analysis. Different from step S2, in step S4, the inward micro-bent side wall plate is simplified into a two-hinged arch under uniform load, and the deformation of the arch crown is solved by finite element software to obtain the deformation value of the arch crown, that is, the deformation value of the inward micro-bent side wall plate. Then, check whether the deformation value of the micro-bent wall plate is less than the allowable deflection value of the arched steel structure mainly under compression specified in the national standard "Steel Structure Design Standard". The allowable deflection value is 1 / 400 of the arch span. Specifically in this application, the arch span is the distance between the lower end of the upper wall plate of the semi-circular arc and the upper end of the lower wall plate of the semi-circular arc. If the deformation of the micro-bent wall plate is less than the allowable deflection value, determine the design of this cross-section; otherwise, return to step S1 to modify the wall thickness or return to step S3 to increase the basic bending rise. Repeat this cycle until the deformation of the micro-bent wall plate of the proposed circular-ended steel pipe main arch rib with a micro-bent web plate is less than the allowable deflection value.

[0103] Specifically in this embodiment, the applicant found that when the value of the basic bending rise in step S3 is 40 mm, the calculated deformation value of the arch crown in step S4 is 0.9 mm. And in this embodiment, the distance between the lower end of the upper arc wall plate and the upper end of the lower arc wall plate is 600 mm. Therefore, the allowable deflection value in this embodiment is 600*(1 / 400) = 1.5 mm. Obviously, the calculated deformation value of the arch crown of 0.9 mm in this application is less than the allowable deflection value of 1.5 mm. At this time, it is relatively ideal in both appearance effect and local stability.

[0104] A construction method for a circular-ended steel pipe concrete composite arch rib with a micro-bent web plate includes the following construction steps:

[0105] 1), Cut and process the upper semi-circular arc wall plate 1-1, the lower semi-circular arc wall plate 1-2, and the inward micro-bent side wall plate 1-3 in the factory, and weld them to form the main arch rib 1 segment; Cut and process the connecting rod 3 in the factory; Cut and process and bend the steel pipe of the secondary arch rib 2 in the factory.

[0106] 2), Weld the upper semi-circular arc wall plate 1-1, the lower semi-circular arc wall plate 1-2, and two inward micro-bent side wall plates 1-3 to form the main arch rib 1 segment.

[0107] 3), Assemble and weld the main arch rib 1, the connecting rod 3, and the secondary arch rib 2 outside the arch feet to form a micro-bent web plate circular-ended steel pipe composite arch rib segment outside the arch feet; Assemble and weld the main arch rib 1, the connecting rod 3, and the secondary arch rib 2 at the arch feet to form a micro-bent web plate circular-ended steel pipe composite arch rib segment at the arch feet, as Figure 12 shown;

[0108] 4), hoist the micro-bent wall-plate type circular-ended steel pipe composite arch rib segments, assemble and weld them into a complete arch rib of the micro-bent wall-plate type circular-ended steel pipe composite arch rib, and pour and fix the arch feet of the complete arch rib in the reinforced concrete arch seat 5 fixedly arranged on the bridge deck;

[0109] 5), inject self-compacting and slightly expanding concrete into the main arch rib 1 through the concrete injection pipe to form the core concrete layer 4.

[0110] Among them, in step 5), the specific technological steps of injecting self-compacting and slightly expanding concrete into the main arch rib 1 through the concrete injection pipe 6 are as follows: open injection holes and exhaust and slurry discharge holes on the main arch rib 1. The injection holes are opened at a position 1 m from the bottom end of the arch foot of the main arch rib 1, and the exhaust and slurry discharge holes are opened at the top end of the main arch rib 1 and are inclined along the transverse bridge direction; the injection holes are fixedly connected to the concrete injection pipe 6, the concrete injection pipe 6 is arranged in the plane of the main arch rib 1 and forms an angle of 30° with the main arch rib 1, the exhaust and slurry discharge holes are fixedly connected to the exhaust and slurry discharge pipe 7, and the self-compacting and slightly expanding concrete is constructed by one-time continuous pump pressure injection until the concrete discharged from the exhaust and slurry discharge pipe 7 is the same as the concrete injected by the concrete injection pipe 6, then the injection construction is completed; after the injection is completed, cut off the concrete injection pipe 6 and the exhaust and slurry discharge pipe 7, and weld steel plates on the injection holes and the exhaust and slurry discharge holes to seal the injection holes and the exhaust and slurry discharge holes; in this embodiment, the connection relationship between the concrete injection pipe 6, the exhaust and slurry discharge pipe 7 and the main arch rib 1 is as Figure 13 shown.

[0111] The overall mechanical property of the structure of the micro-bent wall-plate type circular-ended steel pipe concrete composite arch rib in this application lies in: whether the main arch rib 1 and the core concrete layer 4 located therein can work together. In this application, the core concrete layer 4 is made of self-compacting and slightly expanding concrete, and is constructed by one-time continuous pump pressure injection until the concrete discharged from the exhaust and slurry discharge pipe 7 is the same as the concrete injected by the concrete injection pipe 6 before the construction ends. Such a setting in this application can make the injected self-compacting and slightly expanding concrete closely fit with the main arch rib 1 after drying to form an integrated stress body, so as to effectively ensure the cooperative stress between the main arch rib 1 and the core concrete layer 4.

Claims

1. A concrete-filled steel tubular combined arch rib with a circular end shape and a micro-bent wall plate, characterized in that: It is composed of a main arch rib, a core concrete layer filled in the main arch rib, two secondary arch ribs, and several connecting rods for connecting the main arch rib and the secondary arch ribs; the axis of the main arch rib is parabolic, the axes of the two secondary arch ribs are circular arc-shaped, and the two secondary arch ribs are both inclined and symmetrically arranged on both sides of the main arch rib. The two arch feet of the secondary arch ribs are respectively fixedly connected to the two arch feet of the main arch rib. The two secondary arch ribs have the same structure, and the two secondary arch ribs are higher than the main arch rib. Except at the arch feet, the main arch rib and the secondary arch ribs are fixedly connected by connecting rods; the main arch rib is a slightly curved wall plate type circular end steel pipe, and the main arch rib is fixedly connected by enclosing and connecting an outwardly convex semi-circular upper wall plate, an outwardly convex semi-circular lower wall plate, and two inwardly slightly curved side wall plates; the secondary arch rib is a circular hollow steel pipe, and the connecting rod is a rectangular hollow steel pipe; The inwardly slightly curved side wall plate is an inwardly slightly curved circular arc-shaped side wall plate. The calculation method of the bending rise of the inwardly slightly curved side wall plate includes the following steps: S1: It is necessary to tentatively determine the wall thickness of the straight side wall plate type main arch rib model, the height and width of the longitudinal section of the main arch rib model through trial calculations. After calculating Ac and As from the wall thickness of the main arch rib model, the height and width values of the longitudinal section of the main arch rib model, verify through formula (1), and determine the parameter values that can make the normal section compressive bearing capacity of the main arch rib model meet the requirements of formula (1) to obtain the tentatively determined straight side wall plate type main arch rib model; where formula (1) is as follows: γ0N d ≤0.9φ(f cd A c +f s A s )(1) In Equation (1), γ0 is the structural importance coefficient; N d is the design axial compression force of the main arch rib, N d is obtained by performing a structural force analysis on the entire arch bridge using finite element software in the prior art; φ is the axial compression stability coefficient, f cd is the design value of the compressive strength of the core concrete layer, f s is the design value of the compressive strength of the steel used for the main arch rib; A c is the cross-sectional area of the core concrete layer, A s is the sum of the cross-sectional areas of the upper wall panel of the semi-circular arc, the lower wall panel of the semi-circular arc, and the cross-sectional areas of the two straight side wall panels; S2: Conduct a deformation analysis of the pressure injection of self-compacting micro-expansion concrete pump pressure on the tentatively determined straight side wall plate type main arch rib model obtained in step S1, and calculate the deformation amount of the straight side wall plate; S3: Set the deflection deformation amount of the straight side wall plate calculated in step S2 in the reverse inward direction as the basic bending rise of the inwardly slightly curved side wall plate. Considering the impact dynamic effect of the pressure injection of concrete, and according to the sectional appearance design effect brought by the proportional coordination of the micro-bending rise and the width and height of the longitudinal section of the main arch rib model, magnify the basic bending rise as the design bending rise. At the same time, the micro-bending line type of the inwardly slightly curved side wall plate is circular arc-shaped. Then, combine the wall thickness of the tentatively determined straight side wall plate type main arch rib model obtained in step S1, the width and height of the longitudinal section of the tentatively determined straight side wall plate type main arch rib model, and the design bending rise of the inwardly slightly curved side wall plate determined in step S3 to obtain the tentatively determined slightly curved wall plate type circular end steel pipe main arch rib; Step S2 is specifically: S2-1: Analyze the pump pressure acting outward on the semi-circular upper wall plate, semi-circular lower wall plate, and two straight side wall plates of the main arch rib model, and calculate the total pump pressure loss P of the pressure injection; the total pump pressure loss P of the pressure injection is calculated through formula (2); P = P v +P H +ΔP1 + ΔP2 (2) In formula (2), P v is the static pressure generated by the pumping height, P H is the frictional pump pressure loss, △P1 is the pump pressure loss caused by the joint flange, and △P2 is the pump pressure loss caused by the sling conduit; Among them, the static pressure P generated by the pumping height v is calculated by formula (3): P v = γ C × H(3) In formula (3), γ C is the unit weight of self-compacting slightly expansive concrete, and H is the pumping height inside the main arch rib; Frictional pump pressure loss P H , calculated by Equation (4): P H =L△P H (4) In formula (4), L is the pumping length within the main arch rib, and △P H is the frictional pressure loss per unit length; The pump pressure loss △P1 caused by the joint flange is calculated through formula (5): △P1=n1×0.2 (5) In formula (5), n1 is the number of joint flanges; The pump pressure loss △P1 caused by the sling conduit is calculated through formula (6): △P2=n2×0.2 (6) In formula (6), n2 is the number of sling conduits; S2-2: The isolation method is used to separately take out the side wall panel for analysis. The side wall panel is simplified into a simply supported beam under uniformly distributed load, and the deflection deformation amount f of the side wall panel max is calculated by formula (7): f max = 5qL 4 / 384EI (7) In formula (7), q is the uniformly distributed load, that is, the pump pressure applied to the wall panel of the proposed straight side wall plate main arch rib model per unit length of 1m in the main arch rib length direction. The calculation formula of q is shown in formula (8); in formula (7), L is the distance between the lower end of the semicircular upper wall panel and the upper end of the semicircular lower wall panel, that is, the longitudinal height of the straight side wall panel, E is the elastic modulus of the steel used in the proposed straight side wall plate main arch rib model, and I is the bending inertia moment of the wall panel of the proposed straight side wall plate main arch rib model; q=P×1 (8) In formula (8), P is the total pressure loss of the injection pump.

2. The concrete-filled steel tubular composite arch rib with a circular end shape and a micro-bent web plate according to claim 1, characterized in that: The main arch ribs except the arch foot are fixedly connected to the connecting rod through the outer surfaces of their two inward slightly curved side wall panels; the arch foot of the secondary arch rib is fixedly connected to the inward slightly curved side wall panel at the arch foot of the main arch rib.

3. The concrete-filled steel tubular composite arch rib with a circular end and a micro-bent web plate according to claim 1, wherein: The semicircular upper wall panel and the semicircular lower wall panel have the same structure and are symmetrically arranged; the two inwardly slightly curved side wall panels have the same structure and are symmetrically arranged.

4. The concrete-filled steel tubular composite arch rib with a circular end and a micro-bent web plate according to claim 1, characterized in that: The inward slightly curved side wall panel is a slightly inwardly curved arc-shaped side wall panel. The method for calculating the bending sagitta of the inward slightly curved side wall panel further includes step S4: performing deformation analysis on the cross section of the proposed slightly curved wall panel-type round-end steel pipe main arch rib under the action of the injection-cast concrete pump pressure again to calculate the deformation value of the inward slightly curved side wall panel; then checking whether the deformation value of the slightly curved wall panel is less than the allowable deflection value of the arch steel structure mainly subjected to compression as specified in the design specifications, the allowable deflection value being 1 / 400 of the arch span, where the arch span is the distance between the lower end of the semicircular arc upper wall panel and the upper end of the semicircular arc lower wall panel; if the deformation of the slightly curved wall panel is less than the allowable deflection value, then determining the cross-section design; Otherwise, return to step S1 to modify the wall thickness or return to step S3 to increase the basic bending sagitta, and repeat this cycle until the deformation of the proposed slightly curved wall panel of the round-end steel pipe main arch rib is less than the allowable deflection value.

5. The concrete-filled steel tubular composite arch rib with a circular end and a micro-bent web plate according to claim 1, characterized in that: Step S1 specifically comprises: preliminarily planning the wall thickness of the main arch rib model and the height and width of the longitudinal section of the main arch rib model according to the site conditions and design specification requirements, wherein the structure of the main arch rib model is preliminarily planned to be a round-end steel pipe structure formed by a semicircular upper wall panel, a semicircular lower wall panel, and two straight side wall panels, and judging whether the preliminarily planned wall thickness of the main arch rib model and the height and width of the longitudinal section of the main arch rib model make the longitudinal section compressive bearing capacity of the main arch rib model meet the requirements of formula (1).

6. The concrete-filled steel tubular composite arch rib with a circular end and a micro-bent wall plate according to claim 4, characterized in that: In step S4, the total injection pump pressure loss P is calculated in the same manner as in step S2. The inwardly slightly curved sidewall panel is then analyzed using the same isolation method. In step S4, the inwardly slightly curved sidewall panel is simplified to a two-hinged arch subjected to a uniformly distributed load, and the arch crown deformation is calculated using finite element software to obtain the arch crown deformation value, i.e., the deformation value of the inwardly slightly curved sidewall panel.

7. The concrete-filled steel tubular composite arch rib with a circular end and a micro-bent web plate according to claim 1, characterized in that: The distance between two adjacent connecting rods on the same side is 2~4m.

8. A construction method for a concrete-filled steel tubular combined arch rib with a circular end shape and a micro-bent wall panel type, characterized in that: The slightly curved wall plate type round-end steel tube concrete composite arch rib is the slightly curved wall plate type round-end steel tube concrete composite arch rib according to claim 1. The construction method of the slightly curved wall plate type round-end steel tube concrete composite arch rib comprises the following construction steps: 1), Cut and process the upper semi-circular wall panel, the lower semi-circular wall panel, and the inwardly slightly bent side wall panel, and weld them to form the main arch rib segment; Cut and process the connecting rod; Cut and process and bend the secondary arch rib steel pipe; 2), Group-weld the upper semi-circular wall panel, the lower semi-circular wall panel, and the two inwardly slightly bent side wall panels to form the main arch rib segment; 3), Assemble and weld the main arch rib outside the arch foot, the connecting rod, and the secondary arch rib outside the arch foot to form the slightly bent wall panel type circular-ended steel pipe combined arch rib segment outside the arch foot; Assemble and weld the main arch rib, the connecting rod, and the secondary arch rib at the arch foot to form the slightly bent wall panel type circular-ended steel pipe combined arch rib segment at the arch foot; 4), Lift and install the slightly bent wall panel type circular-ended steel pipe combined arch rib segment, and assemble and weld it into the complete arch rib of the slightly bent wall panel type circular-ended steel pipe combined arch rib. The arch foot of the complete arch rib is poured and fixed in the reinforced concrete arch seat fixedly arranged on the bridge deck; 5), Inject self-compacting and slightly expanding concrete into the main arch rib through the concrete injection pipe to form the core concrete layer.

9. The construction method of the concrete-filled steel tubular composite arch rib with a circular end and a micro-bent web plate according to claim 8, characterized in that: In step 5), the specific technological steps of injecting self-compacting and slightly expanding concrete into the main arch rib through the concrete injection pipe are as follows: Open injection holes and exhaust and slurry discharge holes on the main arch rib. The injection holes are fixedly connected to the concrete injection pipe, and the exhaust and slurry discharge holes are fixedly connected to the exhaust and slurry discharge pipe. The self-compacting and slightly expanding concrete is constructed by one-time continuous pumping injection until the concrete discharged from the exhaust and slurry discharge pipe is the same as the concrete injected by the concrete injection pipe, then the injection construction is completed; After the injection is completed, cut off the concrete injection pipe and the exhaust and slurry discharge pipe, and weld steel plates on the injection holes and the exhaust and slurry discharge holes to seal the injection holes and the exhaust and slurry discharge holes.

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