Long-span deck-type cable-assisted beam-arch composite rigid frame bridge and its construction method

Abstract

The present invention discloses a long-span deck-type cable-assisted beam-arch composite rigid frame bridge, which includes a hollow pier, an upper chord box girder, a lower chord box arch supporting the upper chord box girder, a cable tower located directly above the hollow pier and the upper chord box girder, and stay cables distributed along the cable tower in the beam-arch joint area formed by the convergence and intersection of the upper chord box girder and the lower chord box arch. The upper chord box girder, the lower chord box arch and the hollow pier intersect to form a beam-arch triangular area. The upper chord box girder is supported by the hollow pier and the arch columns on the arch in the beam-arch triangular area. The hollow pier intersects with the arch feet of the lower chord box arches of the side span and the middle span. The arch columns are evenly distributed perpendicular to the lower chord box arch in the elevation view. It improves the bearing efficiency of the bridge structure from the aspects of structural system and force mechanism, overcomes the cracking and deflection problems commonly occurring in conventional concrete rigid frame bridges, further expands the spanning ability of concrete rigid frame bridges, and has the advantages of excellent structural mechanical properties, high cost performance, and convenient maintenance.

Description

Technical Field

[0001] The present invention relates to the field of bridge engineering, and particularly to a long-span deck-type cable-assisted beam-arch composite rigid frame bridge that combines a deck-type arch, a continuous rigid frame bridge, and a partially cable-stayed bridge to give full play to the advantages of the composite structural system. Background Art

[0002] The deck-type reinforced concrete arch bridge is a bridge structural system with thrust, and is widely used due to its advantages such as economic cost, beautiful shape, and large spanning capacity. The long-span deck-type reinforced concrete arch bridge is mainly applicable to mountainous areas or mountainous urban construction environments. The huge thrust generated by it requires relatively hard and complete rocks with high compressive strength as the bearing layer of the arch foot foundation. When the geological conditions of the bridge site are poor, it is often impossible to adopt a long-span arch bridge with thrust.

[0003] The traditional prestressed concrete continuous rigid frame bridge is also a main bridge type applicable to mountainous areas or mountainous urban construction environments, but this bridge type is often applicable to the case where the main span does not exceed 200m. When the prestressed concrete continuous rigid frame bridge develops towards a larger span, due to its excessive self-weight, the concrete strength will be basically consumed by its own weight, and defects such as mid-span deflection and main beam cracking are very likely to occur during service, thus restricting the development of the spanning capacity of this bridge type.

[0004] The reasonable bridge span application range of the traditional prestressed concrete low tower cable-stayed bridge is between 150m and 280m. In terms of structural force, the low tower cable-stayed bridge is mainly beam-based and cable-assisted. The main beam bears most of the load. About 70% of the stay cables only bear about 30% of the overall load to assist. The inclination angle of the stay cables of the low tower cable-stayed bridge is relatively small, so that the component force of the stay cables on the main body of the bridge is not large, and the vertical component force provided is limited. Since the vertical component force generated by the stay cables is very small compared with that of the dense cable system cable-stayed bridge, it will increase the axial pressure and negative moment at the root of the main beam, resulting in the need to increase the cross-section near the consolidation of the main beam, pier, and tower. In this case, if the span is further increased, it is not conducive to saving construction costs and the economy is poor.

[0005] Due to the certain limitations of the mechanical properties of traditional single structural systems such as deck-type reinforced concrete arch bridges, prestressed concrete continuous rigid frame bridges, and low tower cable-stayed bridges, their prospects for development towards larger spans are limited. Compared with traditional single bridge structural systems, composite structural systems can give full play to their respective advantages.

[0006] Therefore, based on the design concept of structural system combination, a new type of deck-type beam-arch composite rigid frame bridge with greater spanning capacity, more efficient force, better economy, and faster construction is developed. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide a long-span deck cable-assisted beam-arch composite rigid frame bridge, which improves the bearing efficiency of the bridge structure from the aspects of structural system and force mechanism, overcomes the cracking and deflection problems commonly occurring in rigid frame bridges, and further expands the spanning ability of concrete rigid frame bridges, having the advantages of excellent structural mechanical properties, high cost performance, and convenient maintenance.

[0008] The long-span deck cable-assisted beam-arch composite rigid frame bridge of the present invention includes a hollow pier (3), an upper chord box girder (1), a lower chord box arch (2) supporting the upper chord box girder (1), a cable tower (4) located directly above the hollow pier (3) and the upper chord box girder (1), and stay cables (8) distributed along the cable tower in the area of the beam-arch joint section (13) formed by the convergence and intersection of the upper chord box girder (1) and the lower chord box arch (2). The upper chord box girder (1), the lower chord box arch (2) and the hollow pier (3) intersect to form a beam-arch triangle area. The upper chord box girder (1) is supported by the hollow pier (3) and the arch columns (5) in the beam-arch triangle area. The hollow pier (3) intersects with the arch feet of the lower chord box arches (2) of the side spans and the middle span. The arch columns (5) are evenly distributed perpendicular to the lower chord box arch (2) in the elevation.

[0009] Furthermore, the arch column (5) is a buried steel strong skeleton with reinforced concrete on the outside, and the steel strong skeleton extends into the pier-arch joint section (34) formed by the beam-arch joint section (13), the hollow pier (3) and the intersection of the arch feet of the lower chord arches of the side spans and the middle span.

[0010] Furthermore, the hollow pier (3) is a variable cross-section structure with a smaller top and a larger bottom.

[0011] Furthermore, the upper chord box girder (1) includes a box girder top plate (111), a box girder bottom plate (121) and box girder webs (302), and longitudinal prestressed steel tendons (113) are arranged in the box girder top plate (111), the box girder bottom plate (121) and the box girder webs (302).

[0012] Furthermore, box girder top plate strengthening transverse ribs (112) are arranged along the center of the bottom edge of the box girder top plate (111) in the longitudinal bridge direction, box girder bottom plate strengthening transverse ribs (122) are arranged along the center of the top edge of the box girder bottom plate (121) in the longitudinal bridge direction, and web transverse connections (305) are formed by connecting the box girder webs (302) in the transverse bridge direction.

[0013] Furthermore, a cantilever top plate strengthening longitudinal beam (115) is provided at a position about 1 / 3 of the cantilever length from the cantilever end of the box girder top plate (111). A UHPC precast diagonal bracing rod (131) is provided at the intersection of the cantilever top plate strengthening longitudinal beam (115) and the box girder top plate strengthening transverse rib (112). The UHPC precast diagonal bracing rod (131) is connected to the box girder top plate strengthening transverse rib (112) and the box girder bottom plate (121) through a precast diagonal bracing rod UHPC cast-in-place connection joint (132), and is aligned with the box girder top plate strengthening transverse rib (112) and the box girder bottom plate strengthening transverse rib (122) in the longitudinal bridge direction with the same spacing.

[0014] Furthermore, the embedded steel pipe concrete strong skeleton of the lower chord box arch (2) is a truss structure, including an embedded stiff skeleton upper chord steel pipe (201), an embedded stiff skeleton lower chord steel pipe (202), an embedded stiff skeleton vertical web member (203), and an embedded stiff skeleton inclined web member (204). The embedded stiff skeleton upper chord steel pipe (201) and the embedded stiff skeleton lower chord steel pipe (202) are arranged in parallel on both sides in the longitudinal bridge direction. An embedded stiff skeleton vertical web member (203) and an embedded stiff skeleton inclined web member (204) are fixedly connected between the embedded stiff skeleton upper chord steel pipe (201) and the embedded stiff skeleton lower chord steel pipe (202) arranged in parallel in the longitudinal bridge direction. The embedded stiff skeleton upper chord steel pipes (201) in the transverse bridge direction are fixedly connected to form an embedded stiff skeleton upper horizontal bracing (205), and the embedded stiff skeleton lower chord steel pipes (202) in the transverse bridge direction are fixedly connected to form an embedded stiff skeleton lower horizontal bracing (206). An embedded stiff skeleton cross bracing (208) is connected between the embedded stiff skeleton upper horizontal bracing (205) and the embedded stiff skeleton lower horizontal bracing (206).

[0015] Furthermore, the cast-in-place connection joints between the UHPC precast diagonal bracing rod (131) and the box girder top plate strengthening transverse rib (112) and the box girder bottom plate (121), the beam-column joint section (15), and the lower chord arch and arch-column joint section (25) all use UHPC as the material for the connection nodes.

[0016] The present invention discloses a construction method for a long-span upper-supported cable-assisted beam-arch composite rigid frame bridge, including the following steps:

[0017] Step a: Construct the pile foundation (7) and the bearing platform (6);

[0018] Step b: Construct the hollow pier (3) by climbing formwork. The pier-arch joint section (34) is constructed through the lower chord arch pier-arch joint section cast-in-place bracket (801) and the lower chord arch pier-arch joint section cast-in-place bracket arc section formwork support system (802).

[0019] Step c: Continue the climbing formwork construction of the hollow pier (3) above the pier-arch joint section (34), install the strong skeleton segments of the lower chord box arch (2), and use the inverted triangle suspended casting hanging basket (804) of the lower chord arch to symmetrically and synchronously cantilever the on-site casting of the concrete of the lower chord box arch (2) segments. After the concrete of the first suspended casting segment of the lower chord box arch (2) reaches the strength, move the inverted triangle suspended casting hanging basket (804) of the lower chord arch to the next suspended casting segment;

[0020] Step d: Install the in-situ bracket and formwork system for the pier-beam-tower joint section (14) at the top of the hollow pier (3), and cast the pier-beam-tower joint section (14) on-site; after the concrete of the 3rd suspended casting segment of the lower chord box arch (2) reaches the strength, tension the first pair of temporary stay cables (805) of the lower chord arch;

[0021] Step e: After the construction of the pier-beam-tower joint section (14) above the top of the hollow pier (3) is completed, install the standard segments of the triangular suspended casting hanging basket (803) of the upper chord box girder, and symmetrically and synchronously cantilever the construction of the upper suspended beam segments by each segment;

[0022] Step f: Continue the symmetric and synchronous construction of the upper chord beam segments and the suspended casting segments of the lower chord box arch (2). The temporary stay cables (805) of the lower chord arch are strung and tensioned 1 segment behind the suspended casting segments of the lower chord box arch (2); use the climbing formwork to construct the cable tower (4);

[0023] Step g: When the suspended casting segments of the lower chord box arch (2) and the standard segments of the upper chord beam are constructed to the arch-column (5) above the pier, install the arch-column (5), and pour the UHPC in-situ joint of the beam-column joint section (15) and the joint section of the lower chord arch and the arch-column (25);

[0024] Step h: After the upper chord box girder (1) is constructed to the cable-stayed cable anchorage section, after each construction of an upper chord box girder (1), install and tension the corresponding cable-stayed cable (8) of this segment;

[0025] Step i: Repeat Steps f to h to construct the upper chord box girder (1), the lower chord box arch (2) and the arch-column (5) by each segment until the upper chord box girder (1) converges with the lower chord box arch (2); install the locking wedge blocks, and tightly combine the upper chord box girder (1), the lower chord box arch (2) and the locking wedge blocks to form a stable triangular stress structure in advance;

[0026] Step j: Complete the construction of the beam-arch joint section (13), and symmetrically and synchronously construct the conventional beam segments (12) on both sides;

[0027] Step k: Remove the triangular suspended casting hanging basket (803) of the upper chord box girder, first close the side span using the side span support, and then use the inverted triangle suspended casting hanging basket (804) of the lower chord arch to close the middle span, and tension the longitudinal prestressed steel tendons (307) of the bottom slab and the longitudinal prestressed steel tendons (308) of the web of the conventional beam segments;

[0028] Step 1: Demolish the inverted triangular cantilever casting hanging basket (804) of the lower chord arch, symmetrically demolish the temporary stay cables (805) of the lower chord arch, the in-situ casting bracket (801) at the pier-arch joint section of the lower chord arch, and the formwork support system (802) of the arc section of the in-situ casting bracket at the pier-arch joint section of the lower chord arch to complete the construction of the main bridge structure;

[0029] Furthermore, for the hollow pier (3), the pier-arch joint section (34), and the cable tower (4), in-situ casting construction is adopted. The lower chord box arch (2) utilizes the hollow pier (3) between the pier-arch joint section (34) and the pier-beam-cable tower joint section (14) to support the cantilever force during the auxiliary construction stage of the temporary stay cables (805) of the lower chord arch. Symmetric and synchronous installation of a strong skeleton and cantilever casting construction are adopted. The upper chord box girder (1) adopts symmetric and synchronous cantilever casting construction, and the arch-column (5) is symmetrically and synchronously installed.

[0030] The beneficial effects of the present invention are as follows: The long-span deck-type cable-assisted beam-arch composite rigid frame bridge disclosed by the present invention improves the bearing efficiency of the bridge structure from the aspects of structural system and force mechanism, overcomes the cracking and deflection problems commonly occurring in rigid frame bridges, and further expands the spanning ability of concrete rigid frame bridges. It has the advantages of excellent structural stress performance, high cost performance, and convenient maintenance. Description of the Drawings

[0031] The present invention will be further described below in conjunction with the drawings and embodiments:

[0032] Figure 1 It is the elevation layout drawing of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0033] Figure 2 It is the cross-sectional layout drawing of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0034] Figure 3 It is the three-dimensional axonometric perspective view of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0035] Figure 4 It is the structural system schematic diagram of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0036] Figure 5 It is the force mechanism schematic diagram of the structural system of the cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0037] Figure 6 It is the typical cross-sectional drawing of the upper chord beam cable anchor area of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0038] Figure 7 It is the elevation layout drawing of the lower chord arch of the deck-type cable-assisted beam-arch composite rigid frame bridge of the embodiment of the present invention;

[0039] Figure 8 It is the cross-sectional layout drawing of the lower chord arch of the deck-type open-web girder-arch composite rigid frame bridge according to the embodiment of the present invention;

[0040] Figure 9 It is the typical cross-sectional layout drawing of the conventional beam section of the deck-type cable-assisted girder-arch composite rigid frame bridge according to the embodiment of the present invention;

[0041] Figure 10 It is the three-dimensional structure schematic diagram of the beam-arch connection section of the deck-type cable-assisted girder-arch composite rigid frame bridge according to the embodiment of the present invention;

[0042] Figure 11 It is the schematic diagram of the construction method steps of the deck-type cable-assisted girder-arch composite rigid frame bridge according to the embodiment of the present invention;

[0043] Figure 12 It is the schematic diagram of the construction method of the triangular area of the deck-type cable-assisted girder-arch composite rigid frame bridge according to the embodiment of the present invention.

[0044] Among them, the above-mentioned drawings include the following reference numerals: 1 - upper chord box girder, 2 - lower chord box arch, 3 - bridge pier, 4 - cable tower, 5 - arch-column on the arch, 6 - bearing platform, 7 - pile foundation, 8 - stay cable, 12 - conventional beam section, 13 - beam-arch connection section, 14 - pier-beam-cable tower connection section, 15 - beam-column connection section, 25 - connection section between the lower chord arch and the arch-column on the arch, 34 - pier-arch connection section, 41 - turning saddle, 111 - box girder top plate, 112 - transverse stiffening rib of the box girder top plate, 113 - longitudinal prestressed steel bundle of the top plate, 114 - anchor of the longitudinal prestressed steel bundle, 115 - longitudinal stiffening beam of the cantilever of the box girder top plate, 116 - cable-beam anchorage block, 121 - box girder bottom plate, 122 - transverse stiffening rib of the box girder bottom plate, 123 - longitudinal prestressed steel bundle of the bottom plate, 131 - UHPC precast diagonal bracing rod, 132 - UHPC cast-in-place connection joint of the precast diagonal bracing rod, 201 - upper chord steel pipe of the embedded stiffening skeleton, 202 - lower chord steel pipe of the embedded stiffening skeleton, 203 - vertical web member of the embedded stiffening skeleton, 204 - inclined web member of the embedded stiffening skeleton, 205 - upper horizontal bracing of the embedded stiffening skeleton, 206 - lower horizontal bracing of the embedded stiffening skeleton, 207 - gusset plate of the embedded stiffening skeleton, 208 - transverse bracing of the embedded stiffening skeleton, 209 - gusset plate of the transverse bracing of the embedded stiffening skeleton, 210 - gusset plate of the transverse bracing of the embedded stiffening skeleton, 211 - concrete poured into the steel pipe of the embedded stiffening skeleton, 212 - concrete wrapped outside the stiffening skeleton, 301 - bottom plate of the conventional beam section, 302 - web of the conventional beam section, 303 - vertical stiffening rib for strengthening the middle web of the conventional beam section, 304 - transverse stiffening rib of the bottom plate of the conventional beam section, 305 - transverse bracing of the web of the conventional beam section, 306 - UHPC cast-in-place connection joint of the transverse bracing of the web of the conventional beam section, 307 - longitudinal prestressed steel bundle of the bottom plate of the conventional beam section, 308 - longitudinal prestressed steel bundle of the web of the conventional beam section. Detailed implementation manners

[0045] The long-span deck-type cable-assisted beam-arch composite rigid frame bridge of this embodiment includes a hollow pier 3, an upper chord box girder 1, a lower chord box arch 2 supporting the upper chord box girder 1, a cable tower 4 located directly above the hollow pier 3 and the upper chord box girder 1, and stay cables 8 distributed along the cable tower in the area of the beam-arch joint section 13 formed by the convergence of the upper chord box girder 1 and the lower chord box arch 2. The upper chord box girder 1, the lower chord box arch 2, and the hollow pier 3 intersect to form a beam-arch triangular area. The upper chord box girder 1 is supported by the hollow pier 3 and the upper-arch columns 5 in the beam-arch triangular area. The hollow pier 3 intersects with the arch feet of the lower chord box arches 2 of the side span and the middle span. The upper-arch columns 5 are evenly distributed perpendicular to the lower chord box arch 2 in the elevation. The hollow pier 3 is consolidated with the pile foundation 7 and is provided with a bearing platform 6. The upper chord box girder 1 and the lower chord box arch 2 converge and intersect to form a beam-arch joint section 13. The conventional beam sections 12 are located between the beam-arch joint section 13 at the side span and the end of the upper chord beam and between the beam-arch joint sections 13 at the middle span. The cable tower 4 is arranged directly above the hollow pier 3 and the upper chord box girder 1. A pier-beam-cable tower joint section 14 is arranged between the hollow pier 3, the upper chord box girder 1, and the cable tower 4. A beam-column joint section 15 is arranged between the upper chord box girder 1 and the upper-arch columns 5. A lower chord arch-upper-arch column joint section 25 is arranged between the lower chord box arch 2 and the upper-arch columns 5. The hollow pier 3 intersects with the arch feet of the lower chord arches of the side span and the middle span to form a pier-arch joint section 34. The upper chord box girder 1, the lower chord box arch 2, the hollow pier 3, and the upper-arch columns 5 are pairwise consolidated. The cable tower 4 is consolidated with the hollow pier 3 and the upper chord box girder 1. Stay cables 8 are arranged between the cable tower 4, the upper chord box girder 1, and the conventional beam section 12, jointly forming a beam-deck-type arch-partially cable-stayed composite continuous rigid frame system. A longitudinal movable bearing is provided at the bottom edge of the side span beam end. The lower chord box arch 2 and the upper-arch columns 5 are symmetrically arranged along the center line of the hollow pier 3. Rounded chamfers are provided in the transition areas of the beam-arch joint section 13, the pier-beam-cable tower joint section 14, the beam-column joint section 15, the lower chord arch-upper-arch column joint section 25, and the pier-arch joint section 34. The bottom edge line shapes of the conventional beam section 12 and the beam-arch joint section are the same as the bottom edge line shape of the lower chord box arch 2, and the elevation is arched. The upper chord box girder 1 adopts a straight web single-box multi-room structure with a constant beam height and a constant web height. A diaphragm beam is arranged in the pier top section. A pier-beam-cable tower joint section 14 is arranged at the bottom of the pier top section beam, which is fixedly connected to the hollow pier 3 and the cable tower 4. In this embodiment, the deck-type arch and the rigid frame bridge structural systems are combined, making full use of the mechanical characteristics of the arch, beam, and low tower cable-stayed structural systems, giving full play to the advantages of the composite structural system, significantly improving the structural bearing efficiency and structural stiffness, and increasing its maximum spanning ability by at least 1.8 to 2.5 times or more. The formed "thrust-free-self-balanced" force system enables the bridge foundation to mainly bear vertical forces, thereby reducing the foundation scale. It is particularly suitable for the construction environment of mountainous or hilly urban bridges, especially in areas with poor geological conditions where large-span thrust arch bridges cannot be used, but the spans of low tower cable-stayed bridges, beam-arch composite rigid frame bridges, and continuous rigid frame bridges cannot meet the requirements of the bridge site.

[0046] In this embodiment, the above-arch column 5 is a buried steel strong framework with reinforced concrete on the outside. The steel strong framework extends into the beam-arch joint section 13 and the pier-arch joint section 34 formed by the intersection of the hollow pier 3 with the lower chord arch feet of the side span and the middle span. The steel strong framework and the reinforced concrete on the outside together form an SRC structure, and the above-arch column 5 is prefabricated in the factory. During on-site construction, high-performance concrete is poured into the steel pipes of the strong framework. At the same time, formwork is erected outside the strong framework to pour the outer concrete in sections and layers. After it solidifies and bears force, the concrete poured into the steel pipes in the strong framework and the reinforced concrete on the outside and the steel pipes together form an SRC structure, jointly exerting the structural bearing capacity. After the lower chord arch solidifies and takes shape, the stiffening framework is filled and wrapped with concrete, enhancing the buckling stability of the stiffening framework and significantly improving the stiffness, strength, and seismic ductility of this bridge type. Compared with the simple reinforced concrete box arch structure, the lower chord arch adopts the combined structure of concrete-filled steel pipe strong framework + reinforced concrete on the outside, effectively reducing the wall thickness and cross-sectional area, and reducing the consumption of concrete materials and the structural self-weight.

[0047] In this embodiment, the hollow pier 3 is a variable cross-section structure with a smaller top and a larger bottom; it has a relatively large flexural stiffness to resist the unbalanced thrust of the lower chord arches of the side span and the middle span under variable loads. The main pier, the lower chord arch, and the upper chord beam form a stable triangular frame structure. The arranged stay cables can not only effectively reduce the negative bending moment and shear force of the upper chord beam, but also actively adjust the structural internal force and long-term deflection deformation, thus avoiding the structural deflection and cracking caused by the late creep of the long-span concrete structure to the greatest extent.

[0048] In this embodiment, the upper chord box girder 1 includes a box girder top plate 111, a box girder bottom plate 121, and box girder webs 302. Longitudinal prestressed steel tendons 113 are provided in the box girder top plate 111, the box girder bottom plate 121, and the box girder webs 302. Longitudinal prestressed steel tendon corrugated pipes are provided in the top plates, bottom plates, and webs of the upper chord box girder 1 and the conventional beam segments 12, and are connected by longitudinal prestressed steel tendons. Longitudinal prestressed steel tendon anchors 114 are provided at the ends of each cantilever segment for tensioning and anchoring to provide pre-compressive stress to counteract the horizontal thrust generated by the lower chord box arch 2, as well as the tensile stress generated by the self-weight of the structure and vehicle loads on the beam cross-section. The lower chord box arch 2, the hollow piers 3, and the cable towers 4 bear compression, the arch-column 5 corresponding to the cable-beam anchorage block 116 of the stay cables bears tension, and the remaining arch-columns 5 bear compression. The horizontal thrust generated by the lower chord box arch 2 is resisted and balanced by the stay cables 8 and the longitudinal prestressed steel tendons 113 provided in the top plates, bottom plates, and webs of the upper chord box girder 1 and the conventional beam segments 12, forming a "thrust-free self-balanced" force system. The beam-arch connection segments 13 between the end of the upper chord beam and the beam-arch connection segments 13 in the mid-span are conventional beam segments 12 that mainly bear bending, constituting a beam-through arch-partial cable-stayed combined force system. The center line of the cable tower 4 is located at the exact center of the bridge transversely. The cable tower 4 and the stay cables 8 are both arranged between the vehicle lane crash barriers in the central isolation belt of the bridge deck transversely. The cable tower 4 adopts a common reinforced concrete structure, and a swivel saddle 41 is provided in the cable tower anchorage area as the turning and force transmission structure of the stay cables on the cable tower. Each pair of stay cables 8 and swivel saddles 41 are symmetrically arranged along the center line of the cable tower 4 transversely, at the intersection of the box girder top plate 111 and the central web of the box girder at the corresponding segment in the cable-stayed anchorage area of the upper chord box girder 1 and the conventional beam segments 12.

[0049] In this embodiment, box girder top plate strengthening transverse ribs 112 are provided at the bottom edges of the box girder top plate 111 along the central longitudinal direction, box girder bottom plate strengthening transverse ribs 122 are provided at the top edges of the box girder bottom plate 121 along the central longitudinal direction, and web cross connections 305 are formed by connecting the box girder webs 302 along the transverse direction. The upper chord box girder 1 and the conventional beam segments 12 both adopt common high-performance concrete. Box girder top plate strengthening transverse ribs 112 are provided at the bottom edges of the box girder top plate 111 along the central longitudinal direction of each cantilever casting segment, and box girder bottom plate strengthening transverse ribs 122 are provided at the top edges of the box girder bottom plate 121 along the central longitudinal direction of each cantilever casting segment.

[0050] In this embodiment, a cantilever top plate strengthening longitudinal beam 115 is provided at a position about 1 / 3 of the cantilever length from the cantilever end on the top plate 111 of the box girder. A UHPC precast diagonal bracing rod 131 is provided at the intersection of the cantilever top plate strengthening longitudinal beam 115 and the box girder top plate strengthening transverse rib 112. The UHPC precast diagonal bracing rod 131 is connected to the box girder top plate strengthening transverse rib 112 and the box girder bottom plate 121 through a precast diagonal bracing rod UHPC cast-in-place connection joint 132, and is aligned with the box girder top plate strengthening transverse rib 112 and the box girder bottom plate strengthening transverse rib 122 in the longitudinal bridge direction with the same spacing.

[0051] In this embodiment, the embedded steel tube concrete strong skeleton of the lower chord box arch 2 is a truss structure, including an embedded stiffening skeleton upper chord steel tube 201, an embedded stiffening skeleton lower chord steel tube 202, an embedded stiffening skeleton vertical web member 203, and an embedded stiffening skeleton diagonal web member 204. The embedded stiffening skeleton upper chord steel tube 201 and the embedded stiffening skeleton lower chord steel tube 202 are arranged in parallel on both sides in the longitudinal bridge direction. An embedded stiffening skeleton vertical web member 203 and an embedded stiffening skeleton diagonal web member 204 are fixedly connected between the embedded stiffening skeleton upper chord steel tube 201 and the embedded stiffening skeleton lower chord steel tube 202 that are parallel in the longitudinal bridge direction. The embedded stiffening skeleton upper chord steel tubes 201 in the transverse bridge direction are fixedly connected to form an embedded stiffening skeleton upper horizontal bracing 205, and the embedded stiffening skeleton lower chord steel tubes 202 in the transverse bridge direction are fixedly connected to form an embedded stiffening skeleton lower horizontal bracing 206. An embedded stiffening skeleton cross bracing 208 is connected between the embedded stiffening skeleton upper horizontal bracing 205 and the embedded stiffening skeleton lower horizontal bracing 206.

[0052] In this embodiment, the cast-in-place connection joints between the UHPC precast diagonal bracing rod 131 and the box girder top plate strengthening transverse rib 112 and the box girder bottom plate 121, the beam-column joint section 15, and the lower chord arch and arch column joint section 25 all use UHPC as the material for the connection nodes. Using UHPC material for the cast-in-place joints of the connection node components has less material consumption, a simple structure, shortens the construction period, enhances the strength of the connection section, conforms to the structural design concept of "strong nodes, weak members", and thus significantly improves the diseases of the rigid frame arch connection nodes caused by easy cracking, resulting in reduced structural safety and durability.

[0053] The construction method of the long-span upper-supported cable-assisted beam-arch composite rigid frame bridge in this embodiment includes the following steps:

[0054] Step a: Construct the pile foundation 7 and the bearing platform 6;

[0055] Step b: Construct the hollow pier 3 by climbing formwork. The pier-arch joint section 34 is constructed through the lower chord arch pier-arch joint section cast-in-place bracket 801 and the lower chord arch pier-arch joint section cast-in-place bracket arc section formwork support system 802.

[0056] Step c: Continue the climbing formwork construction of the hollow pier 3 above the pier-arch joint section 34, install the strong skeleton sections of the lower chord box arch 2, and use the inverted triangle cantilever casting hanging basket 804 of the lower chord arch to symmetrically and synchronously cast the concrete of the lower chord box arch 2 sections on-site. After the concrete of the first cantilever casting section of the lower chord box arch 2 reaches the strength, move the inverted triangle cantilever casting hanging basket 804 of the lower chord arch to the next cantilever casting section;

[0057] Step d: Install the in-situ bracket and formwork system of the pier-beam-tower joint section 14 at the top of the hollow pier 3, and cast the pier-beam-tower joint section 14 on-site; after the concrete of the 3rd cantilever casting section of the lower chord box arch 2 reaches the strength, tension the first pair of temporary stay cables 805 of the lower chord arch;

[0058] Step e: After the construction of the pier-beam-tower joint section 14 above the top of the hollow pier 3 is completed, install the standard sections of the upper chord box girder triangular cantilever casting hanging basket 803, and symmetrically and synchronously construct the upper suspension beam sections by cantilever for each section;

[0059] Step f: Continue to symmetrically and synchronously construct the upper chord beam sections and the cantilever casting sections of the lower chord box arch 2. The temporary stay cables 805 of the lower chord arch are strung and tensioned 1 section behind the cantilever casting sections of the lower chord box arch 2; construct the cable tower 4 by climbing formwork;

[0060] Step g: When the cantilever casting sections of the lower chord box arch 2 and the standard sections of the upper chord beam are constructed to the arch-column 5, install the arch-column 5, and cast the UHPC in-situ joint of the beam-column joint section 15 and the joint section between the lower chord arch and the arch-column 25;

[0061] Step h: After the upper chord box girder 1 is constructed to the cable-stayed cable anchorage section, after each construction of an upper chord box girder 1, install and tension the corresponding cable-stayed cable 8 of this section;

[0062] Step i: Repeat steps f to h to construct the upper chord box girder 1, the lower chord box arch 2 and the arch-column 5 section by section until the upper chord box girder 1 and the lower chord box arch 2 converge; install the locking wedge blocks, tightly combine the upper chord box girder 1 with the lower chord box arch 2 and the locking wedge blocks, and form a stable triangular stress structure in advance;

[0063] Step j: Complete the construction of the beam-arch joint section 13, and symmetrically and synchronously construct the conventional beam sections 12 to both sides;

[0064] Step k: Remove the upper chord box girder triangular cantilever casting hanging basket 803, first close the side span using the side span support, then close the middle span using the inverted triangle cantilever casting hanging basket 804 of the lower chord arch, and tension the longitudinal prestressed steel tendons 307 of the bottom slab and the longitudinal prestressed steel tendons 308 of the web of the conventional beam section;

[0065] Step 1: Demolish the inverted triangle cantilever casting hanging basket 804 of the lower chord arch, symmetrically demolish the temporary cable of the lower chord arch 805, the cast-in-place bracket 801 of the combined section of the pier and arch of the lower chord arch, and the formwork support system 802 of the arc section of the cast-in-place bracket of the combined section of the pier and arch of the lower chord arch to complete the construction of the main bridge structure.

[0066] In this embodiment, the hollow pier 3, the combined section of the pier and arch 34, and the cable tower 4 are constructed by in-situ casting. The lower chord box arch 2 uses the hollow pier 3 between the combined section of the pier and arch 34 and the combined section of the pier, beam and cable tower 14 to support the cantilever force during the auxiliary construction stage of the temporary cable 805 of the lower chord arch. The strong skeleton is installed symmetrically and synchronously, and the cantilever casting construction is adopted. The upper chord box girder 1 is constructed by symmetric and synchronous cantilever casting, and the columns on the arch 5 are installed symmetrically and synchronously.

[0067] Compared with the prior art, the long-span deck-type cable-assisted beam-arch composite rigid frame bridge of the present invention has the following beneficial effects:

[0068] (1) The structure systems of the deck-type arch and the rigid frame bridge are combined, making full use of the mechanical characteristics of the arch, beam and low tower cable-stayed structure systems, giving full play to the advantages of the composite structure system, significantly improving the bearing efficiency and structural stiffness of the structure, and increasing its maximum spanning capacity by at least 1.8 to 2.5 times or more. The formed "thrust-free - self-balanced" force system enables the foundation of the bridge to mainly bear vertical forces, thereby reducing the foundation scale. It is especially suitable for the construction environment of mountainous or hilly urban bridges, especially in areas with poor geological conditions where large-span thrust arch bridges cannot be used, but the spans of low tower cable-stayed bridges, beam-arch composite rigid frame bridges, and continuous rigid frames cannot meet the requirements.

[0069] (2) The lower part of the main pier below the combined section of the pier and arch is a variable-section hollow pier, which has a large flexural stiffness to resist the unbalanced thrust of the lower chord arches of the side span and the middle span under variable loads. The main pier, the lower chord arch and the upper chord beam form a stable triangular frame structure. The cable-stayed cables set not only effectively reduce the negative bending moment and shear force of the upper chord beam, but also can actively adjust the internal force and long-term deflection deformation of the structure, thus minimizing the deflection and cracking of the large-span concrete structure caused by creep in the later stage.

[0070] (3) The lower chord arch adopts a buried steel tube concrete strong framework. By pouring high-performance concrete into the steel tube, and at the same time erecting formwork outside the strong framework to pour the outer concrete in sections and layers. After its solidification and force bearing, the concrete poured into the steel tube in the strong framework and the outer reinforced concrete together with the steel tube form an SRC structure, jointly exerting the structural bearing capacity. After the lower chord arch is formed by the solidification of concrete, the stiffening framework is filled and wrapped by concrete, enhancing the buckling stability of the stiffening framework and significantly improving the stiffness, strength and seismic ductility of this bridge type. Compared with the simple reinforced concrete box arch structure, the lower chord arch adopts a combined structure of concrete-filled steel tube strong framework + outer reinforced concrete, effectively reducing the wall thickness and cross-sectional area, and reducing the consumption of concrete materials and the structural self-weight.

[0071] (4) The UHPC material is used for the cast-in-place joint of the connection node components. It has less material consumption, simple structure, shortens the construction period, enhances the strength of the connection section, conforms to the structural design concept of "strong nodes, weak components", and thus significantly improves the diseases of the rigid frame arch connection node, such as the reduction of structural safety and durability due to easy cracking.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A long-span deck-type cable-assisted beam-arch composite rigid frame bridge, characterized in that: It includes a hollow pier (3), an upper chord box girder (1), a lower chord box arch (2) supporting the upper chord box girder (1), a cable tower (4) located directly above the hollow pier (3) and the upper chord box girder (1), and stay cables (8) distributed along the cable tower in the area of the beam-arch connection section (13) formed by the convergence and intersection of the upper chord box girder (1) and the lower chord box arch (2). The upper chord box girder (1), the lower chord box arch (2) and the hollow pier (3) intersect to form a beam-arch triangular area. The upper chord box girder (1) is supported by the hollow pier (3) and the arch-column on the pier (5) in the beam-arch triangular area. The hollow pier (3) intersects with the arch feet of the lower chord box arches (2) of the side span and the middle span. The arch-columns on the pier (5) are evenly distributed perpendicular to the lower chord box arch (2) in the elevation view.

2. The long-span deck-type cable-assisted beam-arch composite rigid frame bridge according to claim 1, wherein: The lower chord box arch (2) is a buried steel strong framework with reinforced concrete on the outside. The steel strong framework extends into the pier-arch connection section (34) formed by the beam-arch connection section (13), the hollow pier (3) and the arch feet of the lower chord arches of the side span and the middle span.

3. The long-span deck-type cable-assisted beam-arch composite rigid frame bridge according to claim 2, characterized in that: The hollow pier (3) is a variable cross-section structure with a smaller top and a larger bottom.

4. The long-span deck-type cable-assisted beam-arch composite rigid frame bridge according to claim 3, characterized in that: The upper chord box girder (1) includes a box girder top plate (111), a box girder bottom plate (121) and box girder webs (302). Longitudinal prestressed steel tendons (113) are provided in the box girder top plate (111), the box girder bottom plate (121) and the box girder webs (302).

5. The long-span deck-type cable-assisted beam-arch composite rigid frame bridge according to claim 4, characterized in that: Box girder top plate strengthening transverse ribs (112) are provided along the center of the bottom edge of the box girder top plate (111) in the longitudinal bridge direction. Box girder bottom plate strengthening transverse ribs (122) are provided along the center of the top edge of the box girder bottom plate (121) in the longitudinal bridge direction. Web transverse connections (305) are formed by connecting the box girder webs (302) in the transverse bridge direction.

6. The long-span deck type cable-assisted beam-arch composite rigid frame bridge according to claim 5, characterized in that: Cantilever top plate strengthening longitudinal beams (115) are provided at a position about 1 / 3 of the cantilever length from the cantilever end of the box girder top plate (111). UHPC precast diagonal strut bars (131) are provided at the intersection positions of the cantilever top plate strengthening longitudinal beams (115) and the box girder top plate strengthening transverse ribs (112). The UHPC precast diagonal strut bars (131) are connected to the box girder top plate strengthening transverse ribs (112) and the box girder bottom plate (121) through precast diagonal strut bar UHPC cast-in-place connection joints (132), and are aligned with the box girder top plate strengthening transverse ribs (112) and the box girder bottom plate strengthening transverse ribs (122) in the longitudinal bridge direction with the same spacing.

7. The long-span deck type cable-assisted beam-arch composite rigid frame bridge according to claim 6, characterized in that: The embedded steel tube concrete strong skeleton of the lower chord box arch (2) is a truss structure, including an embedded stiff skeleton upper chord steel tube (201), an embedded stiff skeleton lower chord steel tube (202), an embedded stiff skeleton vertical web member (203), and an embedded stiff skeleton diagonal web member (204). The embedded stiff skeleton upper chord steel tube (201) and the embedded stiff skeleton lower chord steel tube (202) are arranged in parallel on both sides along the longitudinal bridge direction. Between the embedded stiff skeleton upper chord steel tube (201) and the embedded stiff skeleton lower chord steel tube (202) that are parallel along the longitudinal bridge direction, there are fixedly connected an embedded stiff skeleton vertical web member (203) and an embedded stiff skeleton diagonal web member (204). Between the embedded stiff skeleton upper chord steel tubes (201) along the transverse bridge direction, there are fixedly connected to form an embedded stiff skeleton upper horizontal bracing (205). Between the embedded stiff skeleton lower chord steel tubes (202) along the transverse bridge direction, there are fixedly connected to form an embedded stiff skeleton lower horizontal bracing (206). Between the embedded stiff skeleton upper horizontal bracing (205) and the embedded stiff skeleton lower horizontal bracing (206), there is connected an embedded stiff skeleton transverse bracing (208).

8. The long-span deck-type cable-assisted beam-arch composite rigid frame bridge according to claim 7, characterized in that: For the cast-in-place connection joints between the UHPC precast diagonal bracing (131), the strengthened transverse ribs of the box girder top slab (112), and the box girder bottom slab (121), the beam-column joint section (15), and the joint section between the lower chord arch and the arch column (25), UHPC is used as the material for the connection nodes.

9. The construction method of the long-span upper-supported cable-assisted beam-arch composite rigid frame bridge according to claim 1, characterized in that: It includes the following steps: Step a, construct the pile foundation (7) and the bearing platform (6); Step b, use climbing formwork to construct the hollow pier (3). The pier-arch joint section (34) is constructed through the cast-in-place bracket for the lower chord arch pier-arch joint section (801) and the formwork support system for the arc section of the cast-in-place bracket for the lower chord arch pier-arch joint section (802); Step c, continue to use climbing formwork to construct the part of the hollow pier (3) above the pier-arch joint section (34), install the strong skeleton segments of the lower chord box arch (2), and use the inverted triangle cantilever casting hanging basket (804) for the lower chord arch to symmetrically and synchronously cantilever cast the concrete of the lower chord box arch (2) segments on-site. After the concrete of the first cantilever casting segment of the lower chord box arch (2) reaches the strength, move the inverted triangle cantilever casting hanging basket (804) for the lower chord arch forward to the next cantilever casting segment; Step d, install the cast-in-place bracket and formwork system for the pier-beam-tower joint section (14) on the top of the hollow pier (3), and cast the pier-beam-tower joint section (14) on-site; after the concrete of the 3rd cantilever casting segment of the lower chord box arch (2) reaches the strength, tension the first pair of temporary stay cables (805) for the lower chord arch; Step e, after the construction of the pier-beam-tower joint section (14) above the top of the hollow pier (3) is completed, install the standard segments of the triangular cantilever casting hanging basket (803) for the upper chord box girder, and symmetrically and synchronously construct the upper suspended beam segments section by section; Step f, continue to symmetrically and synchronously construct the upper chord beam segments and the cantilever casting segments of the lower chord box arch (2). The temporary stay cables (805) for the lower chord arch are strung and tensioned with a lag of 1 segment behind the cantilever casting segments of the lower chord box arch (2); use climbing formwork to construct the cable tower (4); Step g: When the cantilever casting segment of the lower chord box arch (2) and the standard segment of the upper chord beam are constructed to the location of the arch-column (5) on the arch, install the arch-column (5) on the arch, and cast the UHPC cast-in-place joints of the beam-column connection segment (15) and the connection segment between the lower chord arch and the arch-column on the arch (25); Step h: After the upper chord box girder (1) is constructed to the cable-stayed cable anchorage section, after each upper chord box girder (1) is constructed, install and tension the corresponding cable-stayed cable (8) for this segment; Step i: Repeat Steps f to h to construct the upper chord box girder (1), the lower chord box arch (2) and the arch-column on the arch (5) section by section until the upper chord box girder (1) converges with the lower chord box arch (2); install the locking wedge blocks, tightly combine the upper chord box girder (1), the lower chord box arch (2) and the locking wedge blocks to form a stable triangular stress structure in advance; Step j: Complete the construction of the beam-arch connection segment (13), and symmetrically and synchronously construct the conventional beam segments (12) on both sides; Step k: Demolish the triangular cantilever casting hanging basket (803) of the upper chord box girder, first close the side span using the side span support, and then close the middle span using the inverted triangular cantilever casting hanging basket (804) of the lower chord arch, and tension the longitudinal prestressed steel bundles (307) of the bottom slab of the conventional beam segment and the longitudinal prestressed steel bundles (308) of the web of the conventional beam segment; Step l: Demolish the inverted triangular cantilever casting hanging basket (804) of the lower chord arch, symmetrically demolish the temporary stay cables (805) of the lower chord arch, and the cast-in-place bracket (801) of the pier-arch connection segment of the lower chord arch and the formwork support system (802) of the arc section of the cast-in-place bracket of the pier-arch connection segment of the lower chord arch to complete the construction of the main structure of the bridge.

10. The construction method of the long-span upper-supported cable-assisted beam-arch composite rigid frame bridge according to claim 9, characterized in that: For the hollow pier (3), the pier-arch connection segment (34) and the cable tower (4) are constructed by in-situ casting. The lower chord box arch (2) uses the hollow pier (3) between the pier-arch connection segment (34) and the pier-beam-cable tower connection segment (14) to support the cantilever stress during the auxiliary construction stage of the temporary stay cables (805) of the lower chord arch, and adopts symmetric and synchronous installation of the strong framework and cantilever casting construction. The upper chord box girder (1) adopts symmetric and synchronous cantilever casting construction, and the arch-columns on the arch (5) are installed symmetrically and synchronously.

Images