Large-span deck-type cable-stayed arch bridge and construction method thereof

Abstract

The application discloses a large-span deck type cable-stayed arch bridge and a construction method thereof, which comprises a main arch, a bridge tower, a main beam, cable-stayed cables and the like. The main beam is located on the top of the main arch to form a deck type multi-arch bridge structure. The cable-stayed cables arranged in the central separation belt of the bridge deck pass through the main beam and are anchored on the bridge tower and the main arch respectively, so as to reduce the bending moment and shear force of the main arch. The upright columns arranged between the main arch and the main beam are used for transmitting the load of the main beam to the main arch. The bridge is an economical and reasonable combined structure system bridge with efficient stress and simple construction. Although the stress is relatively more complex, the mechanical properties are better and the structural redundancy is larger. The bridge type utilizes the anchoring of the cable-stayed cables on the main arch, adjusts the internal force of the main arch through tensioning the cable-stayed cables, reduces the bending moment and shear force of the main arch, and assists and shares the stress of the main arch, so that the main arch structure mainly bears the axial force, the stress distribution of the cross section is more uniform, and the purposes of significantly reducing the cross section size of the main arch, reducing the structural self weight and fully utilizing the material are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a combined structure bridge, in particular to a large-span deck-type cable-stayed arch bridge and a construction method thereof. BACKGROUND

[0002] The deck-type reinforced concrete arch bridge is one of the most competitive bridge types in mountainous areas due to its economic cost, beautiful appearance, large span capacity, and less maintenance workload during operation. Small and medium-span deck-type reinforced concrete arch bridges can generally use construction methods such as support site casting, precast cable hoisting, and integral cast-in-place rotation. For large-span reinforced concrete arch bridges, the temporary cable-stayed cantilever method + cable hoisting method is generally used. This construction method has the advantages of not being restricted by terrain, not hindering traffic under the bridge, and having little impact on the ecological environment under the bridge. However, the temporary cable-stayed cantilever method + cable hoisting method requires the use of construction temporary measures (including ground anchors, temporary stay cables, and temporary stay towers) to assist the main arch in the cantilever stage before it is closed. After the main arch is closed, the construction temporary measures are removed, and finally the arch structure is formed. Since the main arch is a long cantilever structure before it is closed and has a considerable self-weight, the cost of construction temporary measures is very high (generally accounting for 15% to 25% of the total construction cost of the bridge), which significantly reduces the economic performance of large-span reinforced concrete arch bridges.

[0003] Currently, the largest span of large-span deck-type reinforced concrete highway arch bridges constructed using the temporary cable-stayed cantilever method + cable hoisting method is close to 350m. However, when the main span is further increased, the carrying capacity of the main arch will be exhausted by its self-weight, and the economic performance and structural efficiency will be significantly reduced. In addition, as the cantilever length of the main arch before it is closed increases with the increase in span, the construction risk and the cost of construction temporary measures (temporary cable-stayed cantilever and anchor system) will significantly increase. For the above reasons, the application of deck-type reinforced concrete arch bridges to larger spans is limited.

[0004] Cable-stayed bridges are a self-anchored bridge structural system with efficient stress and greater span capacity compared to arch bridges. The main girder of a concrete cable-stayed bridge is generally constructed using segmental cantilever assembly or segmental cantilever casting, and the structure is always in a self-balancing stress state, so no other construction temporary measures are needed except for the beam crane (or hanging basket). However, concrete cable-stayed bridges are generally suitable for main spans not exceeding 500m. As the span further increases, the axial pressure on the main girder will increase significantly, resulting in the need to increase the section of the main girder, which increases the structural self-weight and material consumption, reducing the economic performance.

[0005] Therefore, the traditional deck type reinforced concrete arch bridge, concrete cable-stayed bridge and other classic bridge structure systems with single structure system have certain limitations, and it is difficult to meet the bridge construction requirements under diversified mountainous terrain and complex conditions. SUMMARY

[0006] Therefore, the present application aims to provide a large-span deck type cable-stayed arch bridge and a construction method thereof, which has the characteristics of light self-weight, material saving, strong spanning capacity, large structural rigidity and less construction temporary measures.

[0007] The large-span deck type cable-stayed arch bridge comprises a stay cable (7), a tower, a main arch (1) and a main beam (6), the main beam (6) is located on the arch top of the main arch (1) to form a deck type multi-arch arch bridge structure, the stay cable (7) arranged in the central separation zone of the bridge deck is anchored on the main arch (1) through the main beam (6) to reduce the bending moment and shear force of the main arch (1), and an arch column (5) is arranged between the main arch (1) and the main beam (6) to transmit the load of the main beam (6) to the main arch (1);

[0008] Further, the arch seat (9) is arranged at the longitudinal ends of the bridge, and the abutment (8) is arranged on the arch seat (9) and connected with the arch seat (9) as a whole, the arch seat (9) is fixed with the arch foot of the side span of the main arch, and the stay cable (7) on the tower (side tower) on the abutment (8) is anchored on the ground anchor (10) at both ends of the bridge;

[0009] Further, the main beam (6) is a double-width box beam arranged along the center line of the bridge, and a central separation zone is arranged between the double-width box beams, the central separation zone is arranged in a hollow manner, and the stay cable (7) is anchored on the main arch (1) through the central separation zone;

[0010] Further, the main beam (6) is composed of multiple beam segments in the longitudinal direction of the bridge, the two adjacent beam segments are discontinuous at the center line of the main pier (2), and the top surfaces of the beam ends of the two adjacent beam segments form a beam end expansion joint (66) on the pier to ensure the continuity of the bridge deck, and the longitudinal movable support (65) is arranged on the main pier (2) corresponding to the bottom of the beam end;

[0011] Further, the main arch (1) is a single-box multi-cell variable cross-section structure composed of a top plate, a web plate and a main arch diaphragm (11), the stay cable (7) is anchored in the anchoring area at the intersection of the web plate and the main arch diaphragm (11) of the main arch (1), and the anchoring area is provided with a main arch cable anchoring block (12);

[0012] Further, the anchoring area of the stay cable of the top plate of the main arch (1) is provided with transverse prestress to prevent concrete cracking, and the stay cable (7) is distributed in a fan-shaped cable surface on the elevation and is distributed in parallel in the transverse direction;

[0013] Furthermore, the arch columns (5) are arranged radially along the arch axis, and the spacing between the arch columns (5) gradually decreases from the arch foot to the arch crown along the bridge direction;

[0014] Furthermore, the connection node between the arch column (5) and the main beam (6) and the main arch (1) adopts a UHPC hinge (51). The UHPC hinge (51) includes a connection body formed by casting UHPC and structural steel bars. The middle part of the connection body is laterally recessed to form a hinge neck. The pre-embedded steel bars in the arch column (5) and its adjacent structures extend into the UHPC hinge (51).

[0015] Furthermore, the connecting body is provided with cross steel bars (52), the intersection of the cross steel bars (52) is located at the hinge neck, and spiral steel bars (53) are wound on the cross steel bars (52), and the hinge neck and the connecting body are connected by a curved transition.

[0016] The construction method for a long-span, upper-bearing cable-stayed arch bridge of the present invention includes the following steps:

[0017] S1, construct the main pier pile foundation (22), the main pier cap (21), and the ground anchor (10), arch seat (9), and abutment (8) located at both ends of the bridge;

[0018] S2, Climbing formwork construction of main pier (2); The starting section of the main arch (1) is constructed through cast-in-place brackets and arc-shaped formwork support system; Climbing formwork construction of main pier (2) continues until the bottom of the main beam (6);

[0019] S3, After the main pier (2) is completed, continue to use climbing formwork to construct the bridge tower; use hanging basket (101) to symmetrically and synchronously pour the first cantilevered segment of the main arch (1) on site. After the concrete reaches the strength, move the hanging basket (101) forward to the next cantilevered segment; install and tension the first pair of stay cables;

[0020] S4, continue to use the hanging basket (101) to symmetrically and synchronously pour the Nth cantilevered segment of the main arch (1) on site. After the concrete of the Nth cantilevered segment of the main arch (1) reaches the strength, move the hanging basket (101) forward to the N+1 cantilevered segment; install and tension the Nth pair of stay cables;

[0021] S5, repeat step S4 until the main arch (1) is closed, then remove the hanging basket (101);

[0022] S6, symmetrically and synchronously install the arch columns (5); cast the UHPC hinge (51) on site; erect temporary supports on the main arch and symmetrically and synchronously cast the main beam (6) segments from the bridge tower towards the mid-span.

[0023] S7, after the main girder (6) segment concrete reaches the design strength, tension the main girder prestressed steel bundle; remove the temporary support; repeat step S6;

[0024] S8, symmetrically and synchronously, cast in situ the girder segment of the main girder (6) located in the region of the main arch crown;

[0025] S9, the main girder (6) closes, and the main structure construction of the bridge is completed;

[0026] S10, remove the temporary support; construct the bridge deck accessory project; adjust the cable force of the cable-stayed cable (7) to the bridge completion state, and complete the bridge construction.

[0027] The beneficial effects of the present application are: the long-span deck-type cable-stayed arch bridge and the construction method thereof are an economical and reasonable, efficient and simple-to-construct composite structural system bridge, which is a new structural system with relatively more complex stress and better mechanical properties and larger structural redundancy. The bridge type utilizes the anchoring of the cable-stayed cable on the main arch, adjusts the internal force of the main arch by tensioning the cable-stayed cable, reduces the bending moment and shear force of the main arch, and assists and shares the stress of the main arch, so that the main arch structure mainly bears axial force, and the stress distribution of the cross section is more uniform, thereby achieving the purpose of significantly reducing the cross section size of the main arch, reducing the structural self-weight, and fully utilizing the material, which helps to significantly improve the structural efficiency and economy, and further expands the crossing capacity.

[0028] Compared with the prior art, the long-span deck-type cable-stayed arch bridge has the following advantages:

[0029] (1) The deck-type cable-stayed arch bridge can adapt to different site construction conditions in mountainous areas, and can be designed as single main span or multiple main spans according to the terrain and other design requirements, so that the bridge type can meet the requirements of navigation and terrain conditions with an economical and reasonable span.

[0030] (2) The deck-type arch and the cable-stayed supporting structure are combined in the structural system, the mechanical characteristics of each are fully utilized, and the advantages of the combined structural system are exerted, so that the structural self-weight can be reduced, and the structural bearing capacity and structural stiffness can be significantly improved.

[0031] (3) The cable-stayed cable forms a multi-point elastic support for the main arch, further improving the crossing capacity and stability of the main arch structure. At the same time, the cable-stayed cable can be used to adjust the internal force and linear shape of the main arch, improve the structural stiffness, and reduce the cross section size of the main arch.

[0032] (4) Compared with the cable-stayed bridge under the same conditions (same span, width and design standard), the main arch bears part of the bridge deck load, thereby reducing the stress of the cable-stayed cable. In addition, the main girder does not need to bear the large horizontal force caused by the cable-stayed cable, and the cross section size can be reduced. Since the length and cable force of the cable-stayed cable are reduced, the material consumption can also be reduced.

[0033] (5) The main arch construction of the deck-type cable-stayed arch bridge adopts the self-balanced cantilever erection method similar to the main girder of the cable-stayed bridge, which can directly utilize the cantilever construction assisted by the pylons before the main arch closing, and omits the temporary stay cables. With the assistance of the stay cables, the main arch during the cantilever construction is symmetrical along the pylons, and is always a thrust self-balanced structure before closing, so that the temporary stay cables and the temporary ground anchors are not needed. Therefore, the construction temporary measures can be greatly reduced.

[0034] (6) The main pier foundation of the deck-type cable-stayed arch bridge mainly bears the vertical force, so the foundation scale is small, and it is especially suitable for the bridge construction environment under the complex terrain and geological conditions of mountains and hills. The main pier is a variable cross-section hollow pier, which has a large bending stiffness to resist the unbalanced thrust of the main arch under variable loads, and can resist the occasional loads (such as earthquakes, vehicle and ship impacts, or rock impacts).

[0035] (7) The connection joint of the arch column with the main arch and the main girder adopts the UHPC hinge, which takes full advantage of the high compressive and tensile bending strength, toughness and durability of the UHPC material, avoids the disadvantages of the conventional concrete hinge joint (which is still a weak link of structure connection and works with cracks) reducing the safety and durability of the structure, and significantly enhances the firmness and durability of the hinge neck.

[0036] (8) Compared with the long-span reinforced concrete arch bridge, the main arch erection of the deck-type cable-stayed arch bridge only needs the hanging basket, thereby greatly simplifying the construction measures and saving the cost. In addition, the long-span reinforced concrete arch bridge usually adopts a smaller-span girder bridge as the approach bridge on both sides of the main span, which needs to set a large number of piers, not only consumes a large amount of materials for the substructure, but also occupies the space under the bridge, and the excavation of the approach bridge pier foundation will also destroy the ground vegetation. Compared with the traditional long-span reinforced concrete arch bridge with the same span, the deck-type cable-stayed arch bridge has a large side span, eliminates the need to set a large number of approach bridge piers, maximally reduces the influence on the space under the bridge, and protects the ground vegetation. BRIEF DESCRIPTION OF DRAWINGS

[0037] The application will be further described below in conjunction with the drawings and examples:

[0038] Figure 1 is the elevation layout of the deck-type cable-stayed arch bridge of the embodiment of the application;

[0039] Figure 2 is the A-A cross-sectional layout of Figure 1 ;

[0040] Figure 3 is the three-dimensional schematic view of the deck-type cable-stayed arch bridge of the embodiment of the application;

[0041] Figure 4 is the three-dimensional schematic view of the deck-type cable-stayed arch bridge of the embodiment of the application; Figure 3A local enlarged view at A;

[0042] Figure 5 A three-dimensional structure cutaway view of the embodiment of the present application;

[0043] Figure 6 A main beam standard cross-sectional layout of the embodiment of the present application;

[0044] Figure 7 A main pier cross-sectional layout of the embodiment of the present application;

[0045] Figure 8 A main arch cross-sectional layout of the embodiment of the present application;

[0046] Figure 9 A three-dimensional structure cutaway view of the embodiment of the present application;

[0047] Figure 10 A three-dimensional structure cutaway view of the embodiment of the present application; Figure 9 A local enlarged view at A;

[0048] Figure 11 An elevation view of the embodiment of the present application;

[0049] Figure 12 A three-dimensional structure cutaway view of the embodiment of the present application; Figure 11 A local enlarged view at A;

[0050] Figure 13 A three-dimensional structure cutaway view of the embodiment of the present application;

[0051] Figure 14 A three-dimensional structure cutaway view of the embodiment of the present application; Figure 13 A local enlarged view at A;

[0052] Figure 15 A three-dimensional structure cutaway view of the embodiment of the present application; Figure 2 A three-dimensional structure cutaway view of the embodiment of the present application; Figure 1 A B-B cross-sectional layout of the embodiment of the present application;

[0053] Figure 16Fig. 1 is a schematic diagram of the construction steps of the top-supported cable-stayed arch bridge of the embodiment of the present application; wherein the above-mentioned drawings include the following reference signs: 1-main arch, 2-hollow main pier, 3-bridge tower (middle tower), 4-bridge tower (side tower), 5-arch upright column, 6-main beam, 7-cable-stayed cable, 8-abutment, 9-arch seat, 10-ground anchor, 11-main arch diaphragm, 12-main arch cable anchorage block, 21-main pier pile cap, 22-main pier group pile foundation, 31-concrete tower wall, 32-steel anchor box, 33-shear nail, 51-UHPC hinge, 52-crossed steel bar, 53-spiral steel bar, 54-surface structure steel bar, 61-main beam cross beam, 62-main beam top plate, 63-main beam longitudinal prestressed steel tendon, 64-main beam top plate transverse prestressed steel tendon, 65-longitudinal movable support, 66-beam end expansion joint, 91-enlarged foundation, 92-vertical pile, 93-inclined pile, 101-hanging basket. DETAILED DESCRIPTION

[0054] The above and other advantages and effects of the present application will become readily apparent to those of ordinary skill in the art from the description set forth below of certain specific embodiments of the present application. The present application can be applied to other different embodiments and used in other different ways, and the details of the description can be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only schematically illustrate the basic concept of the present application, and the features in the following examples and embodiments can be combined with each other without conflict.

[0055] The drawings are only used for exemplary illustration, and the representation is only a schematic diagram, not a physical diagram, and should not be understood as a limitation on the present application; in order to better illustrate the embodiments of the present application, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual product size; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0056] The same or similar reference signs in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore the terms describing the position relationship in the drawings should not be understood as a limitation on the present application, and the above-mentioned terms should be understood according to their specific meanings according to the specific circumstances by those skilled in the art.

[0057] Unless otherwise defined, all professional terms used herein have the same meaning as commonly understood by those skilled in the art.

[0058] The long-span decked cable-stayed arch bridge of the embodiment comprises cable stays 7, a tower, a main arch 1 and a main girder 6, the main girder 6 is located on the top of the main arch 1 to form a decked multi-arch bridge structure, the cable stays 7 on the tower pass through the main girder 6 and are anchored on the tower and the main arch 1 respectively to reduce the bending moment and shear force of the main arch 1, a column 5 is arranged between the main arch 1 and the main girder 6 to transmit the load of the main girder 6 to the main arch 1, wherein the tower comprises a middle tower 3 and a side tower 4, the main arch 1 is located below the main girder 6, the main arch 1 is fixed at the arch foot position with a main pier 2 and an abutment 9 respectively, and the main arch 1 is fixed at the arch top region with the main girder 6. The decked cable-stayed arch bridge can be designed as a single main span or multiple main spans according to the terrain and other construction requirements. The bridge type needs to be provided with side spans on both sides of the main span, the side spans are also provided with main arches and balance the horizontal thrust of the main span under the dead load by configuring appropriate counterweights. The main arch 1 is structurally continuous in the middle span and the side span. The main arch of the side span can adopt an asymmetric arrangement mode with an asymmetric arch foot height according to the valley terrain conditions.

[0059] In the embodiment, the abutments 9 are arranged at the longitudinal ends of the bridge, and the bridge abutments 8 are arranged on the abutments 9 and integrally formed with the abutments 9, the abutments 9 are fixed with the arch feet of the main arch of the side span, the cable stays 7 on the tower (side tower) 4 located on the bridge abutments 8 are anchored to the ground anchors 10 at both ends of the bridge; the abutments 9 are arranged at both ends of the bridge, the bridge abutments 8 are located above the abutments 9, and the abutments 8 and the abutments 9 are combined into one body, and the bridge abutments 4 are arranged above the bridge abutments 8. The abutments 9 of the decked cable-stayed arch bridge are composed of an enlarged foundation 91, a vertical pile 92 and an inclined pile 93. Referring to Figure 3 The ground anchors 10 of the decked cable-stayed arch bridge are arranged at both ends of the bridge and are located below the median strips of the roads on both sides of the bridge, and are used to anchor the cable stays of the tower (side tower) 4 and balance the stress of the side tower.

[0060] Referring to Figure 2 , Figure 3 and Figure 7 , the tower (middle tower) 3 and the tower (side tower) 4 are located above the bridge deck and are arranged in the central median strip between the main girders 6 in the transverse direction of the bridge. The tower (middle tower) 3 is directly connected with the main pier 2, and the tower (side tower) 4 is directly connected with the bridge abutment 8.

[0061] Referring to Figure 9 and Figure 10 , the tower anchor is a steel-concrete composite structure, which is composed of a hollow-section concrete tower wall 31 and a steel anchor box 32 arranged inside the concrete tower wall 31. Most of the vertical component force of the cable stay 7 is transmitted to the concrete tower wall 31 through the shear pins 33 on the outside of the steel anchor box, and most of the horizontal component force is borne by the steel anchor box 32 itself, only a small part is transmitted to the concrete tower wall 31.

[0062] In this embodiment, the main girder 6 adopts double-width box girder arranged in parallel with the bridge center line, and a central separation strip is arranged between the double-width box girder, and the central separation strip is arranged in a hollow manner. The main girder 6 adopts a straight web single-box double-chamber structure with an equal girder height section. A plurality of main girder cross beams 61 are arranged at equal intervals along the bridge axial direction to connect the left and right separated double-width main girders together to form an integral structure. The central separation strip is arranged in a hollow manner to ensure that the stay cables 7 can pass through and be anchored on the main arch 1. With the assistance of the stay cables 7 and the multi-point support of the main arch 1, the bending moment and shear force of the main arch 1 are significantly reduced, and the cross-section stress distribution is more uniform, so that the material is fully utilized, and the structural efficiency is obviously improved. The main girder 6 adopts a box girder with flanges on the outer side to ensure good integrity and torsional stiffness. The main girder 6 is a prestressed concrete structure, transverse prestressed steel bars 63 are arranged on the top plate, and longitudinal prestressed steel bars 64 are arranged on the web to ensure sufficient crack resistance.

[0063] In this embodiment, the main girder is composed of multiple girder segments in the longitudinal bridge direction, and the two adjacent girder segments are discontinuous at the center line of the main pier 2, and a girder end expansion joint 66 is arranged between the top surfaces of the girder ends of the two adjacent girder segments, and a longitudinal movable support 65 is arranged on the main pier 2 corresponding to the bottom surface of the girder end. See Figure 4 The main girder 6 of the deck-type cable-stayed arch bridge is provided with a longitudinal movable support 65 and a girder end expansion joint 66 at the top of the main pier 2 and the abutment 8 respectively, and the main girder 6 only maintains structural continuity between the main piers to avoid the longitudinal deformation of the main arch 1 caused by variable loads (such as temperature, live load, etc.) being limited. The longitudinal movable support 65 is a conventional arrangement and has a conventional structure in the prior art, which will not be described here.

[0064] In this embodiment, the main arch 1 is a single-box multi-chamber variable cross-section structure composed of a top plate, a web and a main arch cross beam 11, the stay cables 7 pass through the top plate of the main arch 1 and are anchored in the anchoring area at the intersection of the web and the main arch cross beam 11 of the main arch 1, and the anchoring area is provided with a main arch cable anchoring block (12) for anchoring the cable; the stay cable anchoring area of the top plate of the main arch 1 is provided with transverse prestress to prevent concrete cracking, and the stay cables 7 are distributed in a fan-shaped cable surface on the elevation and are distributed in parallel with each other in the transverse direction; the main arch 1 of the deck-type cable-stayed arch bridge adopts a single-box multi-chamber variable cross-section (equal width and gradually changing height) according to the mechanical characteristics of small stress at the arch top and large stress at the arch foot. The main arch 1 can be designed as a reinforced concrete eccentrically compressed member. See Figure 7 The main pier 2 of the deck-type cable-stayed arch bridge is a reinforced concrete variable cross-section hollow thin-walled pier designed as a two-way eccentrically compressed member, and the main pier 2 adopts a variable cross-section with a small upper part and a large lower part to meet the stress requirements. The main pier 2 is fixed with the pile foundation 22 of the main pier group.

[0065] See Figures 1-3 , Figure 5 ,Figure 11 The cable-stayed cables 7 are located in the center of the bridge in the transverse direction and are arranged between the crash barriers of the central median of the bridge deck. The cable-stayed cables 7 are arranged in a fan shape in the vertical direction and are arranged in parallel in the transverse direction. The cable-stayed cables 7 are made of carbon fiber reinforced polymer (CFRP) cables. The CFRP material has the advantages of light weight, high strength, low creep, low relaxation rate, excellent fatigue resistance and corrosion resistance, and can prevent the cable-stayed cables 7 from chemical corrosion in an acid, alkali, chloride salt and humid environment, greatly improving the durability and service life. In addition, the CFRP has a relatively low coefficient of thermal expansion, and its coefficient of thermal expansion (0.6×10 -6 / ℃) is only 1 / 20 of that of steel (1.2×10 -5 / ℃). The present application takes advantage of this feature of the CFRP material to significantly reduce the axial deformation of the cable-stayed cables 7 under the action of temperature and the incoordination deformation between the cable-stayed cables 7 and the main arch, thereby optimizing the stress of the bridge structure.

[0066] In this embodiment, the arch columns 5 are arranged radially along the arch axis, and the spacing between the arch columns 5 gradually decreases from the arch foot to the arch top in the bridge longitudinal direction. The inclined arch columns 5 shorten the end span of the main girder 6 near the main pier 2 and also offset part of the horizontal thrust of the main arch 1. The main girder 6 has a shorter end span, and the inclined arrangement of the arch columns 5 is more advantageous than the vertical arrangement for the stress of the main arch 1. The arch columns 5 are made of prefabricated PC components. The arch columns 5 are pre-stressed by the "pretensioning method" during factory prefabrication to ensure the crack resistance of the components. See Figure 13 The arch columns 5 are fixed to the main girder 6 and the main arch 1 to ensure the structural integrity of the bridge.

[0067] In this embodiment, the connecting joint of the arch upper column with the main beam and the main arch adopts a UHPC hinge 51, which comprises a connecting body formed by pouring and molding UHPC and construction steel bars, the middle part of the connecting body is laterally retracted to form a hinge neck, and the pre-buried steel bars in the arch upper column 5 and its adjacent structure extend into the UHPC hinge 51; the connecting body is provided with intersecting steel bars 52, the intersection points of the intersecting steel bars 52 are located at the hinge neck, and the intersecting steel bars 52 are wound with spiral steel bars 53, the hinge neck and the connecting body are connected in a curved surface transition mode, and the pre-buried steel bars in the arch upper column 5 and its adjacent structure extend into the UHPC hinge 51. The UHPC hinge 51 is provided with the intersecting steel bars 52 and the spiral steel bars 53 inside to improve the tensile bearing capacity, local compressive bearing capacity and seismic ductility of the structure. At the same time, the surface construction steel bars 54 are arranged to further increase the crack resistance. In addition, the pre-buried steel bars of the arch upper column 5 and the adjacent structure extend into the UHPC hinge 51 to ensure the connecting strength. The appearance construction form of the hinge is "shrinkage reinforcement". The hinge neck is in a curved surface smooth transition mode to reduce stress concentration as much as possible. Because the bending stiffness at the hinge reinforcement position is much smaller than that of the arch upper column 5, when the arch upper column 5 and the connected main beam 6 and main arch 1 have a small angular displacement, most of the bending moment caused by the variable load can be released.

[0068] The construction method of the long-span deck-type cable-stayed arch bridge in this embodiment is as follows. The main pier group pile foundation 22 and the main pier cap 21 are constructed by a conventional method. The main pier 2, the bridge tower (middle tower) 3 and the bridge tower (side tower) 4 are constructed by a climbing form segmented cast-in-place method. The main arch 1 is constructed by a hanging basket 101 in a symmetrical and segmented pouring mode with the assistance of the cable 7 in the cantilever stage until the closure. After the closure of the main arch 1, a temporary support is erected on the main arch 1, the arch upper column 5 is installed, and then the main beam 6 is cast in segments. After the closure of the main beam, the complete bridge structure is formed.

[0069] The method comprises the following steps:

[0070] S1, the main pier group pile foundation 22, the main pier cap 21, the ground anchor 10 at the two ends of the bridge, the arch seat 9 and the abutment 8 are constructed.

[0071] S2, the main pier 2 is constructed by a climbing form method; the initial segment (0# segment) of the main arch 1 is constructed by a cast-in-place bracket and an arc segment formwork support system; the main pier 2 is continuously constructed by a climbing form method until the bottom of the main beam 6.

[0072] S3, after the construction of the main pier 2 is completed, the bridge tower is continuously constructed by a climbing form method; the first cantilever segment of the main arch 1 is constructed by a hanging basket 101 in a symmetrical and synchronous cast-in-place mode, the hanging basket 101 is moved forward to the next cantilever segment after the concrete reaches the strength, and the first pair of cable stays is installed and tensioned.

[0073] S4, continue to use the hanging basket 101 to symmetrically and synchronously cast the Nth cantilever casting segment of the main arch 1 in situ, and after the concrete of the Nth cantilever casting segment of the main arch 1 reaches the strength, move the hanging basket 101 to the N+1th cantilever casting segment; install and tension the Nth pair of stay cables.

[0074] S5, repeat step 4 until the main arch 1 is closed, and then remove the hanging basket 101.

[0075] S6, symmetrically and synchronously install the arch upright column 5; cast the UHPC hinge 51 in situ; symmetrically and synchronously cast the main beam 6 segment in the direction from the bridge tower to the midspan by erecting a temporary support on the main arch.

[0076] S7, after the concrete of the main beam 6 segment reaches the design strength, tension the main beam prestressed steel strand; remove the temporary support; repeat step 6.

[0077] S8, symmetrically and synchronously cast the beam segment of the main beam 6 located in the region of the main arch crown in situ;

[0078] S9, the main beam 6 is closed, and the main structure construction of the bridge is completed.

[0079] S10, remove the temporary support; construct the bridge deck auxiliary works; adjust the cable force of the stay cable 7 to the state of the completed bridge, and complete the bridge construction.

[0080] In summary, the deck-type cable-stayed arch bridge of the application is composed of a main arch, a main pier, a bridge tower, a stay cable, an arch upright column, a main beam, an arch seat (abutment) and a ground anchor, and the technical solutions and invention points of the main structures and components are as follows:

[0081] I. Main arch

[0082] (1) The main arch is located below the bridge deck, and the structure is continuous in the midspan and side span, the arch foot is fixed with the main pier and the arch seat, and the main arch crown is fixed with the main beam in the midspan region.

[0083] (2) In order to adapt to the inclined valley terrain conditions, the main arch on the side span can adopt an asymmetric arrangement mode of arch foot height in combination with specific terrain conditions.

[0084] (3) According to the mechanical characteristics that the main arch crown is small in stress and the arch foot is large in stress, the main arch can adopt a single-box multi-chamber variable cross-section (equal width and gradually changing height).

[0085] (4) The stay cable passes through the main arch top plate and is anchored at the intersection of the main arch web plate and the transverse diaphragm. A transverse prestress is arranged in the stay cable anchoring area of the main arch top plate to prevent concrete cracking.

[0086] II. Main pier

[0087] (1) The main piers, which are the main components for transferring vertical loads from the superstructure to the foundation, are designed as variable cross-section hollow thin-walled piers, which can be designed as reinforced concrete biaxial eccentric compression members.

[0088] (2) The main piers need to have certain flexibility to adapt to the longitudinal displacement caused by concrete creep and temperature effects, while meeting the requirements of strength, stiffness and stability, and to resist the horizontal thrust difference between the side spans and the midspan of the main arch under live load.

[0089] (3) In the arrangement of the bridge span, the height of the main pier and the cross-sectional size of the pier body should be matched to ensure that the thrust resistance stiffness between each pier body is not significantly different.

[0090] Three, bridge towers

[0091] (1) The bridge towers are located above the bridge deck and are arranged in the central median between the left and right main girders in the transverse direction of the bridge. The bridge towers are divided into central towers and side towers, with the central towers directly connected to the main piers and the side towers connected to the abutments.

[0092] (2) The cable tower anchorage of the bridge tower is a steel-concrete composite structure composed of a hollow concrete thin-walled tower column and a steel anchor box arranged inside the tower column. Most of the vertical component of the stay cable is transmitted to the concrete tower wall through the shear pins on the outside of the steel anchor box, while most of the horizontal component is borne by the steel anchor box itself, with only a small part transmitted to the concrete tower wall.

[0093] Four, stay cables

[0094] (1) The stay cables are arranged in a fan-shaped cable plane and are arranged in parallel in the central median.

[0095] (2) The stay cables use CFRP cables, which have a thermal expansion coefficient only 1 / 20 of that of steel, which can significantly reduce the axial deformation of the cables and the non-uniform deformation of the main arch under temperature effects, optimizing the stress of the bridge structure.

[0096] Five, arch columns

[0097] (1) The arch columns are arranged radially along the arch axis, with the spacing in the bridge direction gradually decreasing from the arch foot to the arch top, which not only coordinates with the inclined stay cables in appearance as much as possible, but also reflects a certain rhythm.

[0098] (2) The inclined arch columns not only shorten the end span of the main girder near the main pier, but also offset part of the horizontal thrust of the main arch. The main girder has a shorter end span due to the inclined arrangement of the arch columns, which is more beneficial to the stress of the main arch compared to the vertical arrangement.

[0099] (3) The arch columns are precast PC components. Pre-stress is applied to the arch columns during factory precasting using the "pretensioning method" to ensure the crack resistance of the components.

[0100] (4) In order to ensure the structural integrity of the bridge, the arch column is fixed with the main beam and the main arch respectively. However, under the action of variable load, the fixation will cause huge additional bending moment to the short column. In order to overcome this shortcoming, the UHPC hinge is used at both ends of the arch column. The appearance of the UHPC hinge is in the form of "shrinkage reinforcement". The hinge neck is smoothly transitioned with a curved surface to reduce stress concentration as much as possible. Because the bending stiffness at the hinge reinforcement position is much smaller than that of the arch column, when the arch column and the connected structure have a small angular displacement, most of the bending moment caused by the variable load can be released.

[0101] Six, main beam

[0102] (1) The main beam adopts double-width equal-beam-height box girder arranged in parallel with the center line of the bridge, and transverse beams are arranged at certain intervals to be connected together to form a whole. The central dividing strip of the bridge deck adopts a hollow arrangement to ensure that the stay cables can pass through and be anchored on the main arch.

[0103] (2) The main beam adopts a box girder with flanges on the outer side to ensure good integrity and torsional stiffness. The main beam is a prestressed concrete member, and longitudinal and transverse prestressed steel bars are arranged in the web and top plate respectively to ensure sufficient crack resistance.

[0104] (3) In order to avoid the longitudinal deformation of the main arch caused by variable loads (such as temperature, live load, etc.) being restricted, expansion joints and longitudinal movable supports are arranged on the top of the main pier and abutment, and the structure is continuous only between the main piers.

[0105] Seven, arch seat (abutment)

[0106] (1) The arch seat (abutment) is arranged at both ends of the bridge, and the abutment is located above the arch seat, and the two are combined into one body, and a side tower is arranged above the abutment.

[0107] (2) The arch seat is composed of an enlarged foundation, inclined piles and vertical piles to resist the huge thrust of the side span main arch and has the advantages of clear stress path, small excavation amount and small environmental impact.

[0108] Eight, ground anchor

[0109] The ground anchor is arranged at both ends of the bridge to anchor the side tower stay cable and balance the stress of the side tower.

[0110] In summary, the deck-type cable-stayed arch bridge of the present application adds a kind of economical and applicable bridge type for the design and construction of mountainous area bridges with a main span of 350-400m.

[0111] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A construction method for a long-span, upper-bearing cable-stayed arch bridge, characterized in that: The cable-stayed arch bridge includes cable stays (7), bridge towers, main arch (1) and main beam (6). The main beam (6) is located on the top of the main arch (1) to form an upper-bearing continuous arch bridge structure. The main beam (6) is a double box girder arranged parallel to the bridge centerline, and a central divider is set between the double box girders. The central divider is hollow. The cable stays (7) set in the central divider pass through the main beam (6) and are anchored to the bridge tower and the main arch (1) respectively to reduce the bending moment and shear force of the main arch (1). The main arch (1) is set with an arch column (5) between the main arch (1) and the main beam (6) to transfer the load of the main beam (6) to the main arch (1). The main arch (1) is a single box multi-cell variable section composed of a top plate, a web plate and a main arch transverse diaphragm (11). The cable-stayed structure is as follows: the cable-stayed cable (7) passes through the top plate of the main arch (1) and is anchored in the anchorage area at the intersection of the web plate and the transverse diaphragm (11) of the main arch (1). The anchorage area is provided with the main arch cable anchor block (12). The arch columns (5) are arranged radially along the arch axis. The spacing between the arch columns (5) gradually decreases from the arch foot to the arch top along the bridge direction. The connection node between the arch columns (5) and the main beam (6) and the main arch (1) adopts UHPC hinge (51). The UHPC hinge (51) includes a connection body cast from UHPC and structural steel bars. The middle part of the connection body is laterally recessed to form a hinge neck. The pre-embedded steel bars in the arch columns 5 and their adjacent structures extend into the UHPC hinge (51). The construction method for a cable-stayed arch bridge includes the following steps: S1, construct the main pier pile foundation (22), main pier cap (21), and ground anchors (10), arch seats (9), and abutments (8) located at both ends of the bridge. S2, Climbing formwork construction of main pier (2); The starting section of the main arch (1) is constructed through cast-in-place brackets and arc-shaped section formwork support system; Climbing formwork construction of main pier (2) continues until the bottom of the main beam (6); S3, After the main pier (2) is completed, continue to use climbing formwork to construct the bridge tower; use hanging basket (101) to symmetrically and synchronously pour the first cantilevered segment of the main arch (1) on site. After the concrete reaches the strength, move the hanging basket (101) forward to the next cantilevered segment; install and tension the first pair of stay cables; S4, continue to use the hanging basket (101) to symmetrically and synchronously pour the Nth cantilever segment of the main arch (1) on site. After the concrete of the Nth cantilever segment of the main arch (1) reaches the strength, move the hanging basket (101) forward to the N+1 cantilever segment; install and tension the Nth pair of stay cables; S5, repeat step S4 until the main arch (1) is closed, then remove the hanging basket (101); S6, symmetrically and synchronously install the arch columns (5); cast the UHPC hinge (51) on site; erect temporary supports on the main arch and symmetrically and synchronously cast the main beam (6) segments from the bridge tower towards the mid-span. S7. After the concrete of the main beam (6) segment reaches the design strength, tension the prestressed steel strands of the main beam; remove the temporary support; repeat step S6. S8, the main beam (6) is located in the arch crown area of ​​the main arch and is symmetrically and synchronously cast on site. S9, the main beam (6) is closed, completing the main structure construction of the bridge; S10, dismantle the temporary supports; construct bridge deck ancillary works; adjust the cable tension of the stay cables (7) to the bridge state, and complete the bridge construction.

2. The construction method for a long-span, upper-bearing cable-stayed arch bridge according to claim 1, characterized in that: It also includes arch seats (9) set at both ends of the longitudinal direction of the bridge, and abutments (8) set on the arch seats (9) and connected to the arch seats (9) as a whole. The arch seats (9) are fixed to the arch feet of the main arch side span, and the cable stays (7) of the bridge towers located on the abutments (8) are anchored to ground anchors (10) at both ends of the bridge.

3. The construction method for a long-span, upper-bearing cable-stayed arch bridge according to claim 1, characterized in that: The main beam (6) is composed of multiple beam segments along the longitudinal direction of the bridge. Two adjacent beam segments are discontinuous at the center line of the pier. Expansion joints (66) are provided between the top surfaces of the beam ends of two adjacent beam segments to ensure the continuity of the bridge deck. Longitudinal movable supports (65) are provided at the bottom of the corresponding beam ends on the pier.

4. The construction method for a long-span, upper-bearing cable-stayed arch bridge according to claim 1, characterized in that: The main arch (1) top plate has a cable anchorage zone with transverse prestress to prevent concrete cracking. The cable (7) is distributed in a fan shape on the vertical surface and is distributed in parallel to each other in the transverse direction.

5. The construction method for a long-span, upper-bearing cable-stayed arch bridge according to claim 1, characterized in that: The connecting body is provided with cross steel bars (52), the intersection of the cross steel bars (52) is located at the hinge neck, and spiral steel bars (53) are wound on the cross steel bars (52). The hinge neck and the connecting body are connected by a curved transition.

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