A steel-UHPC composite roof beam and its construction method

Abstract

The present invention discloses a steel-UHPC composite roof beam and a construction method thereof. The beam is formed by prefabricated steel-wrapped UHPC beam segments connected by cast-in-situ nodes. The beam comprises a plurality of linear beam bodies, with multiple beams arranged in parallel and spaced apart in two directions. Each linear beam body in one direction is constructed in a continuous manner and is spaced apart with a plurality of A nodes. Each linear beam body in the other direction is constructed in sections, and adjacent beam segments are connected by corresponding A nodes to assemble into a grid beam. The circumferential beam body comprises a plurality of arcuate beam segments arranged along a circumference. Adjacent arcuate beam segments are connected by C nodes. The C nodes are also used for the joint intersection of the ends of two linear beam bodies arranged in two directions and the circumferential beam body. Each arcuate beam segment is spaced apart with a plurality of B nodes. The B nodes are used for the intersection of the end of a single linear beam body and the circumferential beam body. Each node structure is simple, the connection construction is convenient, and the connection integrity and reliability are strong. No prestressing is required for each beam body, which greatly simplifies the construction process.

Description

Technical Field

[0001] The present invention relates to the technical field of prefabricated and assembled building construction, and in particular to a steel-UHPC composite roof beam and a construction method thereof. Background Art

[0002] Working pits are crucial passageways for tunnel construction, equipment installation, and maintenance. Circular working pits are common in water conservancy projects, and their above-ground structures require circular roofs. Large-scale water conservancy projects often involve dozens of working pits, each with a large span and depth, such as a span of 35.9 meters and a depth of 50 meters. Furthermore, because the working pits must traverse diverse and complex terrain, the scale of the project is large, the technical complexity, and the construction challenges are significant. Therefore, the working pit roof, especially the roof beams, present significant technical and construction challenges.

[0003] In the prior art, the working shaft roof beams include cast-in-place concrete structure, steel structure and prestressed concrete structure, each of which has the following defects:

[0004] Cast-in-place concrete structures require a large amount of support and formwork, have high construction risks, slow construction speed, long construction period, and are prone to cracking.

[0005] Although steel structures are easy to construct, have a fast construction speed, a short construction period, and good seismic performance, they have poor corrosion resistance and fire resistance, and require special fire prevention treatment. Wind resistance requires combination with other measures, and the operation and maintenance workload is large, and the construction cost is high.

[0006] Prestressed concrete structures have high rigidity and require little maintenance during operation. However, in order to meet the bearing capacity requirements, reinforced concrete beams need to have larger structural dimensions and be configured with a large number of prestressed steel bars, ordinary steel bars and stirrups, which makes concrete pouring inconvenient. Prestressing is not well controlled and is prone to cracking, affecting the durability of the structure. The construction process of tying steel bars and setting up formwork is cumbersome. At the same time, the structure is large in size, heavy in weight, inconvenient to install, and the construction is very complicated, which is not conducive to the seismic resistance of the columns. For grid beams, the end cross-node position is complex and difficult to handle. In addition, for grid beams, the transverse beams, longitudinal beams, and circumferential beams all need to be prestressed throughout their lengths (beams with the same cross-section generally have the same prestressing settings). Since grid beams have intersection nodes, and the prestressed steel strands of each beam are at the same height and intersect with each other, the prestressing settings are crisscrossed, and conflicts are inevitable and difficult to resolve. At the same time, the prestressed steel strands need to be anchored at the ends of the transverse and longitudinal beams. The anchors required for prestressing are large in size, and the prestressing requires horizontal or vertical bending to meet the anchoring distance. Since the ends of the transverse and longitudinal beams are mostly at the intersection with the circumferential beams, there is not enough space for anchors. Therefore, prestressed concrete grid beams are difficult to implement.

[0007] Based on the problems existing in the above-mentioned prior art, it is necessary to conduct in-depth research on the working pit roof beam in order to develop a reasonable circular roof beam structure for the working pit of a water conservancy project. Summary of the Invention

[0008] In response to the defects and shortcomings of the above-mentioned prior art, the present invention proposes a steel-UHPC composite roof beam and its construction method to solve the problems of complex construction technology of working well roof beams in current water conservancy projects, unsatisfactory structural bearing performance, seismic performance or durability, and high project costs.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] A steel-UHPC composite roof beam is formed by connecting several prefabricated steel-wrapped UHPC beam segments through cast-in-place nodes, including:

[0011] A plurality of linear beams of varying lengths are arranged parallel and spaced apart in two directions. The linear beams in one direction are continuous and spaced apart with multiple A nodes, while the linear beams in the other direction are segmented and adjacent beam segments are connected by corresponding A nodes, thereby forming a grid beam.

[0012] The circumferential beam body includes a plurality of arcuate beam segments arranged along the circumference, with adjacent arcuate beam segments connected by C nodes. The C nodes are also used for the intersection of the ends of two straight beam bodies arranged along the two directions and the circumferential beam body. A plurality of B nodes are provided at intervals on each arcuate beam segment. The B nodes are used for the intersection of the end of a single straight beam body and the circumferential beam body.

[0013] The outer surface of the steel beams of the plurality of prefabricated steel-wrapped UHPC beam sections is provided with shear connectors, and a steel mesh is provided on the periphery. The shear connectors and the steel mesh are embedded in the prefabricated UHPC, and the longitudinal beam steel bars are provided with reserved sections at the corresponding nodes to construct the node steel mesh.

[0014] The A node is provided with an A node steel member, the B node is provided with a B node steel member, and the C node is provided with a C node steel member. The A node steel member, the B node steel member and the C node steel member are respectively welded to the ends of the corresponding beam section steel beams. Shear connectors are arranged on the surfaces of the A node steel member, the B node steel member and the C node steel member, and steel mesh is arranged on the periphery. Each node steel member and its shear connector and steel mesh are embedded in the cast-in-place UHPC.

[0015] Preferably, the cross-sectional dimensions of the circumferential beam and the linear beam at non-node locations are the same, and the cross-sectional dimensions of the steel beams are also the same.

[0016] Preferably, the plurality of linear beams include a plurality of continuous transverse beams and a plurality of segmented longitudinal beams, each transverse beam intersecting perpendicularly with each longitudinal beam, wherein the two shortest transverse beams and the two shortest longitudinal beams form a rectangle, and the four corner points of the rectangle are located on the circumference of the circumferential beam;

[0017] There are four C nodes, and the centers of the four C nodes correspond to the four corner points. Accordingly, there are four arc-shaped beam segments in total.

[0018] Preferably, the steel beam has an upper flange, a web and a lower flange, the transverse beam body is reserved with a transverse cast-in-situ section corresponding to the A node, the upper flange and the lower flange of the transverse cast-in-situ section steel beam extend horizontally and protrude to both sides at corresponding positions to construct a cross-shaped A node top plate and bottom plate, the A node top plate and the bottom plate and the transverse cast-in-situ section steel beam web together constitute the A node steel member, the end face dimensions of the connecting ends of the A node top plate and the bottom plate match the end face dimensions of the upper flange and the lower flange of the corresponding beam body steel beam to facilitate butt welding, and the web of the corresponding beam body steel beam protrudes outward to be welded to the side face of the transverse cast-in-situ section steel beam web;

[0019] In the described A node, the ends of the reserved sections of the longitudinal beam reinforcement within the height range of the web of the longitudinal beam section steel beam connected to both sides of the A node are spot welded to the corresponding side surfaces of the web of the transverse cast-in-place section steel beam at the node, and the reserved sections of the longitudinal beam reinforcement outside the height range of the web of the longitudinal beam section steel beam on one side avoid and pass through the longitudinal beam reinforcement outside the height range of the web of the transverse cast-in-place section steel beam at the node, and are overlap-welded with the reserved sections of the longitudinal beam reinforcement corresponding to the longitudinal beam section on the opposite side.

[0020] Preferably, the arc-shaped beam section is reserved with an annular cast-in-situ section corresponding to the B node, and the upper flange and the lower flange of the annular cast-in-situ section steel beam extend horizontally inward at corresponding positions to form a Y-shaped B node top plate and bottom plate, and the B node top plate and the annular cast-in-situ section steel beam web together constitute the B node steel member, and the end surface dimensions of the connecting ends of the B node top plate and the bottom plate match the end surface dimensions of the upper flange and the lower flange of the corresponding beam body steel beam to facilitate butt welding, and the web of the corresponding beam body steel beam extends outward to be welded to the side surface of the web of the annular cast-in-situ section steel beam;

[0021] In the B node, the end of the reserved section of the longitudinal beam reinforcement within the web height range of the longitudinal beam section or the transverse beam section connected to the B node is spot welded to the side surface of the web of the circumferential cast-in-place section steel beam at the node, and the reserved section of the longitudinal beam reinforcement outside the web height range of the circumferential cast-in-place section steel beam avoids and passes through the longitudinal beam reinforcement outside the web height range of the circumferential cast-in-place section steel beam at the node, and extends to the surface of the cast-in-place UHPC near the B node.

[0022] Preferably, the C-node steel member includes a steel pipe, four steel pipe webs welded to the side walls of the steel pipe, and a K-shaped C-node top plate and bottom plate welded to the upper and lower ends of the steel pipe. The center of the steel pipe is the center of the C-node. The four steel pipe webs are distributed in a K-shape, corresponding to the centerline positions of the four connection ends of the C-node, and are welded to the C-node top plate and bottom plate. Two of the steel pipe webs are arc-shaped plates, arranged along the circumference of the circumferential beam body. The end face sizes of the four connection ends of the C-node steel member are matched with the end face sizes of the corresponding beam-shaped steel beams, so as to facilitate butt welding.

[0023] In the C node, the two curved beam sections, one longitudinal beam section and one transverse beam section connected to the C node, which are within the web height range of the steel beam, are all extended to the surface of the steel tube side wall. The longitudinal beam sections outside the web height range of the two curved beam sections are overlapped and welded accordingly. The longitudinal beam sections outside the web height range of the longitudinal beam section and the transverse beam section are free from the longitudinal beam sections and pass through the longitudinal beam sections outside the web height range of the steel tube at the node, and extend to the surface of the cast-in-place UHPC near the C node.

[0024] Preferably, the shear connectors are bolts, which are arranged at intervals according to space and stress conditions and welded to the outer surface of each prefabricated steel-wrapped UHPC beam section, as well as the surface of each A-node steel component, B-node steel component and C-node steel component.

[0025] As a general inventive concept, the present invention also proposes a steel-UHPC composite roof, comprising the steel-UHPC composite roof beam described in any of the above technical solutions, and the steel-UHPC composite roof beam is covered with a prefabricated foamed cement board.

[0026] As a general inventive concept, the present invention also proposes a construction method for the steel-UHPC composite roof beam of the above technical solution, comprising the following steps:

[0027] S1. Determine the structure and dimensions of the steel-UHPC composite roof beams, determine the locations of each node, and rationally divide the circumferential and linear beams into segments. The steel structure fabrication plant will manufacture the steel beams and node steel components for each beam segment according to the segment division diagram, and complete the layout of shear connectors. Node A and node B steel components will be processed as one piece with the corresponding steel beams, while node C steel components will be independent steel structures.

[0028] S2. Transport the steel beams of each beam section to the prefabrication yard. Secure and tie a steel mesh around the outer periphery of the steel beams of each beam section. A reserved section is provided for the longitudinal beam reinforcement extending outward from the end of the steel beam. Install formwork for forming the UHPC envelope around the steel mesh. Cast the UHPC and reserve corresponding cast-in-place sections based on the node layout. After steam curing, remove the formwork and air dry at room temperature. This completes the prefabrication of each steel enveloped UHPC beam section.

[0029] S3. Transport the prefabricated beam segments and C-node steel components to the construction site and assemble them according to the following steps:

[0030] S31, positioning and laying out the straight beam segments according to the plan layout design drawing of the composite roof beam, and then performing A-node connection construction one by one to assemble into a grid beam;

[0031] S32, positioning and laying out the curved beam segments according to the plan layout design drawing of the composite roof beam, and then performing B-node connection construction one by one to complete the assembly of the grid beam and the curved beam segments;

[0032] S33. According to the plan layout design drawing of the composite roof beam, install the C-node steel members in place, and then perform C-node connection construction one by one to complete the overall assembly of the steel-UHPC composite roof beam;

[0033] S4. Integrally hoist the steel-UHPC composite roof beams to the installation position of the working pit roof and install them in place so that they can be covered with prefabricated foamed cement panels later.

[0034] Preferably, in step S3, the A node connection construction, the B node connection construction, and the C node connection construction are all carried out in sequence: welding of the node steel member and the end of the corresponding beam section steel beam, welding of the corresponding longitudinal beam reserved section of the steel bar at the node, tying of the steel bars at the node, installation of the node formwork, and casting of the node UHPC.

[0035] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0036] The present invention rationally divides the circumferential beam and the linear beam into segments, prefabricates them in sections in the factory, and connects and assembles them on site through cross-shaped A nodes, Y-shaped B nodes, and K-shaped C nodes. Each node has a simple structure, convenient connection construction, and strong integrity and reliability. It fully utilizes the performance of steel sections, steel bars, and UHPC (ultra-high performance concrete). No prestressing is required for each beam, which greatly simplifies the construction process, improves construction efficiency, and reduces project costs.

[0037] In the steel-UHPC composite roof beam of the present invention, the plastic deformation of the internal steel section plays a leading role in the structure, thereby enhancing the structural ductility, fundamentally improving the structural seismic performance, increasing the structural bending bearing capacity, and effectively preventing the structural brittle failure; the steel bars are easy to lay out and exert a strong hoop constraint effect, which helps to increase the structural ductility and improve the structural crack resistance; the outer layer is wrapped with UHPC, which has high strength and high toughness, and the outer layer thickness is greatly reduced, which reduces the dead weight of the structure and facilitates construction and lifting. In addition, the excellent bonding performance of UHPC, combined with the steel section, greatly improves the steel section's anti-buckling ability, can achieve a higher bearing capacity, while improving the structural durability and the structural fire resistance.

[0038] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Plan view of the steel-UHPC composite roof beam of this embodiment;

[0040] Figure 2 Schematic diagram of the segment division of the steel-UHPC composite roof beam of this embodiment;

[0041] Figure 3 Cross-section diagram of a standard beam segment in this embodiment;

[0042] Figure 4 Elevation drawing of standard beam section steel beam in this embodiment (illustrating shear stud layout);

[0043] Figure 5 Cross-section of the standard beam section steel beam in this embodiment;

[0044] Figure 6 In this embodiment, the plan view of node A (illustrating the layout of shear studs);

[0045] Figure 7 In this embodiment, the elevation view of node A (illustrating the layout of shear studs);

[0046] Figure 8 The plan view of node B in this embodiment (illustrating the shear stud layout);

[0047] Figure 9 Elevation view of node B in this embodiment (illustrating shear stud layout);

[0048] Figure 10 The C node plan view in this embodiment (illustrating the shear stud layout);

[0049] Figure 11 In this embodiment, the elevation view of the C node (illustrating the shear stud layout);

[0050] In the figure: transverse beam 1, longitudinal beam 2, circumferential beam 3, A node 4, B node 5, C node 6, longitudinal beam reinforcement 7, shear studs 8, steel beam 9, and externally wrapped UHPC 10. DETAILED DESCRIPTION

[0051] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting this patent;

[0052] In order to better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size;

[0053] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings;

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "setting" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. It can be said that the internal communication of the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0055] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0056] The steel-UHPC composite roof beam of the present invention is formed by connecting several prefabricated steel-wrapped UHPC 10 beam sections through cast-in-situ nodes. Figure 1 As shown, the steel-UHPC composite roof beam consists of five linear transverse beams 1 arranged parallel to each other, six linear longitudinal beams 2 arranged parallel to each other, and a closed annular beam 3. The length of each transverse beam and longitudinal beam matches the circumference of the annular beam.

[0057] like Figure 2As shown, each transverse beam is constructed through the entire length and is provided with a plurality of cross-shaped A nodes 4 at intervals. Each longitudinal beam is constructed in sections and adjacent beam sections are connected by corresponding A nodes. In this manner, five transverse beams and six longitudinal beams are assembled to form a grid beam. In this embodiment, each transverse beam intersects with each longitudinal beam at right angles, wherein the two shortest (outermost) transverse beams and the two shortest (outermost) longitudinal beams intersect at their ends to form a rectangle, the four corner points of which are located on the circumference of the circumferential beam. It can be understood that in the steel-UHPC composite roof beam, four nodes (i.e., the K-shaped C nodes 6 described below) are required where the transverse beams, longitudinal beams, and circumferential beams intersect, and the centers of the four C nodes correspond to the four corner points of the rectangle. Correspondingly, the circumferential beam body includes four arc-shaped beam segments arranged along the circumference, and adjacent arc-shaped beam segments are connected by C nodes 6. Among them, three Y-shaped B nodes 5 are respectively provided on the two arc-shaped beam segments corresponding to the above-mentioned short sides of the rectangle, which are used to be connected one-to-one with the other three transverse beam ends, and four Y-shaped B nodes 5 are respectively provided on the two arc-shaped beam segments corresponding to the above-mentioned long sides of the rectangle, which are used to be connected one-to-one with the other four longitudinal beam ends.

[0058] To facilitate factory construction, each beam section is prefabricated according to the segmentation and beam length. The circumferential beam body, transverse beam body and longitudinal beam body all use the same cross-sectional dimensions at non-node locations, and the cross-sectional dimensions of the steel beam 9 are the same (standard beam section).

[0059] In order to resist shear force and ensure the bending bearing capacity of the roof beam, the outer surface of each prefabricated steel-clad UHPC beam section steel beam 9 is provided with shear connectors and a steel mesh is arranged on the periphery. The shear connectors and steel mesh are embedded in the prefabricated UHPC, and the longitudinal beam steel bars 7 are provided with reserved sections at the corresponding nodes (such as the end extension section, the cast-in-place section at the A node and the cast-in-place section at the B node) to construct the node steel mesh.

[0060] In order to improve the integrity and reliability of the connection at each node, the A node 4 is provided with an A node steel member, the B node 5 is provided with a B node steel member, and the C node 6 is provided with a C node steel member. The A node steel member, the B node steel member and the C node steel member are respectively welded to the ends of the corresponding beam section steel beams. The surfaces of the A node steel member, the B node steel member and the C node steel member are all provided with shear connectors, and the periphery is provided with steel mesh. The steel members of each node and their shear connectors and steel mesh are embedded in the cast-in-place UHPC.

[0061] like Figure 3 、 Figure 5As shown, the steel beam has an upper flange, a web and a lower flange, which can be processed and formed by I-beams, channel steels, U-shaped steels, etc. In this embodiment, I-beams are preferred. The shear connectors are shear nails 8, such as Φ60x13mm studs, which are welded to the surface of the upper flange, web and lower flange of the steel beam, as well as the surface of each A-node steel member, B-node steel member and C-node steel member. Among them, the shear nails on the upper flange of the steel beam are generally arranged with a horizontal spacing of 115mm and a vertical spacing of 200mm, the shear nails on the lower flange are generally arranged with a horizontal spacing of 115mm and a vertical spacing of 400mm, and the shear nails on the web are generally arranged in three vertical positions with a vertical spacing of 400mm. The shear nails at the beam ends and nodes (i.e., the surface of the node steel members) are appropriately encrypted according to the space and stress conditions (please refer to Figure 4 、 Figures 6-11 ).

[0062] Among them, each transverse beam body 1 is reserved with a transverse cast-in-place section corresponding to the A node 4, and the upper flange and the lower flange of the transverse cast-in-place section steel beam 9 are rounded at the corresponding positions and then extended and protruded horizontally to both sides to construct a cross-shaped A node top plate and bottom plate. The A node top plate and bottom plate and the transverse cast-in-place section steel beam web together constitute the A node steel component. The end face dimensions of the connecting ends on both sides of the A node top plate and bottom plate match the end face dimensions of the upper flange and lower flange of the longitudinal beam body beam section steel beam on both sides of the A node for butt welding, and the webs of the longitudinal beam body beam section steel beams on both sides extend outward for vertical welding to connect the side faces of the transverse cast-in-place section steel beam webs. In this way, the A node steel component is welded with the end of the corresponding beam section steel beam.

[0063] In the A node, the ends of the reserved sections of the longitudinal beam reinforcement 7 within the height range of the web of the longitudinal beam section steel beam connected to both sides of the A node are spot welded to the corresponding side surfaces of the transverse cast-in-place section steel beam web at the node. The reserved sections of the longitudinal beam reinforcement outside the height range of the web of the longitudinal beam section steel beam on one side avoid and pass through the longitudinal beam reinforcement outside the height range of the web of the transverse cast-in-place section steel beam at the node, and are overlap-welded with the reserved sections of the longitudinal beam reinforcement corresponding to the longitudinal beam section on the opposite side. Furthermore, the core area of ​​the A node (the intersection area of ​​the longitudinal beam reinforcement in the transverse and longitudinal directions at the top and bottom plates) does not need to be tied with stirrups. The intersection of the reinforcement can be directly tied with steel wire, which saves stirrups and avoids congestion of reinforcement. Stirrups are tied in the areas outside the core area of ​​the A node (including the web), and stirrups are appropriately added at the chamfers. In this way, a reinforcement mesh of the A node is formed.

[0064] It can be understood that the longitudinal beam reinforcement outside the web height range of the steel beam refers to the longitudinal beam reinforcement arranged on the upper side of the upper flange and the lower side of the lower flange of the steel beam.

[0065] In this embodiment, each longitudinal beam reinforcement uses 16mm diameter fine-rolled threaded steel bars, and the stirrups use 10mm diameter fine-rolled threaded steel bars. It should be noted that in standard beam sections, the number of longitudinal beam reinforcements is calculated based on structural stresses and is evenly distributed according to the cross-sectional dimensions of the beam. The longitudinal beam reinforcements are spaced approximately 100mm apart, and the stirrups are evenly distributed along the length of the beam, with spacing of 100mm.

[0066] Among them, each arc-shaped beam section is reserved with a circumferential cast-in-place section corresponding to the B node 5. The upper flange and the lower flange of the circumferential cast-in-place section steel beam are rounded at the corresponding positions and then extend and protrude horizontally inward to construct a Y-shaped B node top plate and bottom plate. The B node top plate and bottom plate and the circumferential cast-in-place section steel beam web together constitute the B node steel member. The end face dimensions of the connection ends of the B node top plate and bottom plate match the end face dimensions of the upper flange and the lower flange of the corresponding beam body steel beam for butt welding, and the web of the corresponding beam body steel beam extends outward for oblique welding to connect the side faces of the circumferential cast-in-place section steel beam web. In this way, the B node steel member is welded to the end of the corresponding beam section steel beam.

[0067] In the B node, the end of the reserved section of the longitudinal beam reinforcement within the web height range of the longitudinal beam section or the transverse beam section connected to the B node is spot welded to the side of the web of the circumferential cast-in-place section of the steel beam at the node. The reserved section of the longitudinal beam reinforcement outside the web height range of the steel beam avoids and passes through the longitudinal beam reinforcement outside the web height range of the circumferential cast-in-place section of the steel beam at the node, and extends to the surface of the cast-in-place UHPC near the B node (subsequently outsourced to the cast-in-place UHPC). Furthermore, the core area of ​​the B node connected to the end of the transverse beam (the ring at the top and bottom plates, and the intersection area of ​​the longitudinal beam reinforcement in the transverse direction) and the core area of ​​the B node connected to the end of the longitudinal beam (the ring at the top and bottom plates, and the intersection area of ​​the longitudinal beam reinforcement in the longitudinal direction) do not need to be tied with stirrups. The steel bar intersections can be directly tied with steel wire, which saves stirrups and avoids steel bar congestion. Stirrups are tied in areas outside the core area of ​​the B node (including the web), and stirrups are appropriately added at the chamfers. In this way, a B-node steel mesh is formed.

[0068] It should be noted that the rounded corners of the B nodes are designed accordingly according to their locations to meet the node connection requirements, so the B nodes of each Y-shape are different.

[0069] Among them, the C-node steel component includes a vertically arranged circular seamless steel pipe, four vertically arranged steel pipe webs welded to the side walls of the steel pipe, and a K-shaped C-node top plate and bottom plate horizontally arranged and welded to the upper and lower ends of the steel pipe. The corners of the C-node top plate and bottom plate are chamfered, and the center of the steel pipe is the center of the C-node. The four steel pipe webs are distributed in a K-shape, corresponding to the center line positions of the four connecting ends of the C-node, and are welded to the C-node top plate and bottom plate. Two of the steel pipe webs are arc-shaped plates, which are arranged along the circumference of the circumferential beam body. The end face dimensions of the four connecting ends of the C-node steel component are matched with the end face dimensions of the corresponding beam body steel beam for butt welding. In this way, the welding of the C-node steel component and the end of the corresponding beam section steel beam is realized.

[0070] Optionally, the steel tube webs of the C-node steel members are aligned with the end faces of the top and bottom plates. Accordingly, the webs of the corresponding beam sections connected to the C-nodes are aligned with the end faces of the upper and lower flanges. In this way, at each connection end, the top and bottom plates and steel tube webs of the C-nodes are butt-welded to the upper and lower flanges and web ends of the corresponding beam sections at the same section, facilitating welding construction.

[0071] In another embodiment, the top and bottom plates of the C-node are all extended relative to the steel tube web at all four connection ends, and accordingly, the web of each corresponding beam section steel beam is extended relative to the upper and lower flanges; alternatively, the four steel tube webs are all extended relative to the top and bottom plates of the C-node, and accordingly, the upper and lower flanges of each corresponding beam section steel beam are extended relative to the web. In this way, at each connection end, the top and bottom plates of the C-node and the steel tube web are not butt-welded to the upper and lower flanges and web ends of the corresponding beam section steel beam at the same cross-section, and the butt welds are staggered, which increases the overall weld strength. However, the welding process is not as convenient as the above-mentioned welding at the same cross-section.

[0072] In the C node, the two curved beam sections, one longitudinal beam section and one transverse beam section connected to the C node, the longitudinal beam reinforcement sections within the web height range of the steel beam are all extended to the surface of the steel tube side wall. The longitudinal beam reinforcement sections outside the web height range of the two curved beam sections are correspondingly overlapped and welded. The longitudinal beam section and the transverse beam section, the longitudinal beam reinforcement sections outside the web height range of the steel beam avoid and pass through the longitudinal beam reinforcement outside the web height range of the steel tube at the node (i.e., the circumferential longitudinal beam reinforcement overlapped and welded above), and extend to the surface of the cast-in-place UHPC near the C node (subsequently outsourced to the cast-in-place UHPC). Furthermore, the core area of ​​the C node (the intersection area of ​​the longitudinal beam reinforcement in the circular, longitudinal and transverse directions at the top and bottom plates) does not need to be tied with stirrups. The intersection points of the reinforcement can be directly tied with steel wire, which saves stirrups and avoids congestion of reinforcement. Stirrups are tied in areas outside the core area of ​​the C node (including the web), and stirrups are appropriately added at the chamfers to form a C node reinforcement mesh.

[0073] In the present invention, each node has a simple structure, the connection construction is convenient, and the integrity and reliability of the connection are strong, which fully utilizes the performance of steel sections, steel bars and UHPC. Each beam does not need to be prestressed, which greatly simplifies the construction process, improves construction efficiency and reduces project costs.

[0074] The present invention also provides a steel-UHPC composite roof, comprising the steel-UHPC composite roof beams described in any of the above embodiments. After the steel-UHPC composite roof beams are hoisted and installed, they are covered with prefabricated foamed cement panels. This composite roof exhibits all the benefits of the composite roof beams described in the above embodiments and will not be further elaborated here.

[0075] The present invention also proposes a construction method for the above-mentioned steel-UHPC composite roof beam, comprising the following steps:

[0076] S1. The structure and dimensions of the steel-UHPC composite roof beams are determined based on the designed structural dimensions of the working pit roof and the magnitude of various loads on the roof. The positions of each node are determined, and the circumferential and longitudinal beams are rationally divided into segments (the transverse beams are continuous in length, and the segment dividing lines are shown in the segment division diagram). The steel structure processing plant manufactures the steel beams and node steel components of each beam segment according to the segment division diagram, and completes the layout of the shear connectors. Among them, the A-node steel component and the B-node steel component are processed as one piece with the corresponding steel beams, and the C-node steel component is an independent steel structure.

[0077] S2. Transport the steel beams of each beam section to the prefabrication yard. Secure and tie a steel mesh around the outer periphery of the steel beams of each beam section. A reserved section of longitudinal beam reinforcement extends outward from the end of the steel beam. Install formwork for UHPC encapsulation around the steel mesh. Cast UHPC and reserve corresponding cast-in-place sections based on the node layout. Remove the formwork after steam curing and air dry at room temperature. This completes the prefabrication of each steel-encapsulated UHPC beam section.

[0078] S3. Transport the prefabricated beam segments and C-node steel components to the construction site and assemble them according to the following steps:

[0079] S31. Position and lay out the longitudinal beam segments and transverse beams according to the plan layout design drawing of the composite roof beams. Then, perform A-node connection construction on each transverse beam and its corresponding longitudinal beam segment one by one: construct the middle transverse beam first, then the upper and lower transverse beams. For a single transverse beam, the on-site welding and casting of its A-nodes can be completed one by one, starting with the middle and then the sides, or the on-site welding of its A-nodes can be completed first, then the sides, followed by a unified casting. After completing all A-node connection construction, the transverse beams and longitudinal beams are assembled to form a grid beam.

[0080] S32. Position and lay out the curved beam segments according to the planar layout design drawing of the composite roof beam. Then, perform B-node connection construction on each curved beam segment and its corresponding longitudinal beam (or transverse beam) one by one. For each curved beam segment, the on-site welding and pouring of its B nodes can be completed one by one, starting with the center and then the sides. Alternatively, the on-site welding of the B nodes can be completed first, followed by the pouring of the center and then the sides. Once all B-node connection construction is completed, the grid beam and each curved beam segment are assembled.

[0081] S33. Install the C-node steel members according to the composite roof beam layout design drawings. Connect the C-nodes one by one, completing on-site welding and pouring of the C-nodes. Once all C-node connections are complete, the overall assembly of the steel-UHPC composite roof beam is complete.

[0082] It should be understood that the on-site welding work of the above-mentioned various nodes includes the welding of the node steel components to the ends of the corresponding beam section steel beams, as well as the welding of the corresponding longitudinal beam reserved sections of steel bars at the nodes (lap welding or spot welding). After the welding work is completed, the steel bars at the nodes are tied (including the tying of steel bar intersections and stirrups) to form the node steel mesh, the node formwork is installed, and the node UHPC is poured.

[0083] S4. The assembled steel-UHPC composite roof beams are hoisted as a whole to the installation position of the working pit roof and installed in place so that the prefabricated foamed cement panels can be subsequently covered.

[0084] It should be noted that the steel-UHPC composite roof beam can be designed to be equal in width after being wrapped with UHPC at the top and bottom, or it can be designed to be slightly wider than the bottom after the UHPC is cast at the top (compression zone), that is, wider at the top and narrower at the bottom, so as to maximize the bearing capacity of the steel-UHPC composite roof beam.

[0085] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, and these changes should be covered by the scope of protection of the present invention.

Claims

1. A steel-UHPC composite roof beam, characterized in that: It is composed of several prefabricated steel-clad UHPC beam segments connected by cast-in-place nodes, including: A plurality of linear beams of varying lengths are arranged parallel and spaced apart in two directions. The linear beams in one direction are continuous and spaced apart with multiple A nodes, while the linear beams in the other direction are segmented and adjacent beam segments are connected by corresponding A nodes, thereby forming a grid beam. The circumferential beam body includes a plurality of arcuate beam segments arranged along the circumference, with adjacent arcuate beam segments connected by C nodes. The C nodes are also used for the intersection of the ends of two straight beam bodies arranged along the two directions and the circumferential beam body. A plurality of B nodes are provided at intervals on each arcuate beam segment. The B nodes are used for the intersection of the end of a single straight beam body and the circumferential beam body. The outer surface of the steel beams of the plurality of prefabricated steel-wrapped UHPC beam sections is provided with shear connectors, and a steel mesh is provided on the periphery. The shear connectors and the steel mesh are embedded in the prefabricated UHPC, and the longitudinal beam steel bars are provided with reserved sections at the corresponding nodes to construct the node steel mesh. The A node is provided with an A node steel member, the B node is provided with a B node steel member, and the C node is provided with a C node steel member. The A node steel member, the B node steel member, and the C node steel member are respectively welded to the ends of the corresponding beam section steel beams. Shear connectors are arranged on the surfaces of the A node steel member, the B node steel member, and the C node steel member, and steel mesh is arranged on the periphery. Each node steel member and its shear connector and steel mesh are embedded in the cast-in-place UHPC; The cross-sectional dimensions of the circumferential beam and the linear beam at non-node locations are the same, as are the cross-sectional dimensions of the steel beams. The shear connectors are arranged at intervals according to the space and stress conditions and welded to the outer surface of each prefabricated steel-wrapped UHPC beam section, as well as the surfaces of each A-node steel component, B-node steel component, and C-node steel component.

2. The steel-UHPC composite roof beam according to claim 1, characterized in that: The plurality of linear beams include a plurality of continuous transverse beams and a plurality of segmented longitudinal beams, each transverse beam intersecting perpendicularly with each longitudinal beam, wherein the two shortest transverse beams and the two shortest longitudinal beams form a rectangle, and the four corner points of the rectangle are located on the circumference of the circumferential beam; There are four C nodes, and the centers of the four C nodes correspond to the four corner points. Accordingly, there are four arc-shaped beam segments in total.

3. The steel-UHPC composite roof beam according to claim 2, characterized in that: The steel beam has an upper flange, a web and a lower flange. The transverse beam body is reserved with a transverse cast-in-situ section corresponding to the A node. The upper flange and the lower flange of the transverse cast-in-situ section steel beam extend horizontally and protrude to both sides at corresponding positions to construct a cross-shaped A node top plate and bottom plate. The A node top plate and bottom plate and the transverse cast-in-situ section steel beam web together constitute the A node steel member. The end face dimensions of the connection ends of the A node top plate and bottom plate match the end face dimensions of the upper flange and the lower flange of the corresponding beam body steel beam to facilitate butt welding. The web of the corresponding beam body steel beam protrudes outward to be welded to the side face of the transverse cast-in-situ section steel beam web. In the described A node, the ends of the reserved sections of the longitudinal beam reinforcement within the height range of the web of the longitudinal beam section steel beam connected to both sides of the A node are spot welded to the corresponding side surfaces of the web of the transverse cast-in-place section steel beam at the A node, and the reserved sections of the longitudinal beam reinforcement outside the height range of the web of the longitudinal beam section steel beam on one side avoid and pass through the longitudinal beam reinforcement outside the height range of the web of the transverse cast-in-place section steel beam at the node, and are overlap-welded with the reserved sections of the longitudinal beam reinforcement corresponding to the longitudinal beam section on the opposite side.

4. The steel-UHPC composite roof beam according to claim 3, characterized in that: The arc-shaped beam section is reserved with a circumferential cast-in-situ section corresponding to the B node. The upper flange and lower flange of the circumferential cast-in-situ section steel beam extend horizontally and protrude inward at corresponding positions to construct a Y-shaped B node top plate and bottom plate. The B node top plate and bottom plate and the circumferential cast-in-situ section steel beam web together constitute the B node steel member. The end face dimensions of the connecting ends of the B node top plate and bottom plate match the end face dimensions of the upper flange and lower flange of the corresponding beam body steel beam to facilitate butt welding. The web of the corresponding beam body steel beam extends outward to be welded to the side face of the circumferential cast-in-situ section steel beam web. In the B node, the end of the reserved section of the longitudinal beam reinforcement within the web height range of the longitudinal beam section or the transverse beam section connected to the B node is spot welded to the side surface of the web of the circumferential cast-in-place section steel beam at the B node, and the reserved section of the longitudinal beam reinforcement outside the web height range of the circumferential cast-in-place section steel beam avoids and passes through the longitudinal beam reinforcement outside the web height range of the circumferential cast-in-place section steel beam at the node, and extends to the surface of the cast-in-place UHPC near the B node.

5. The steel-UHPC composite roof beam according to claim 4, characterized in that: The C-node steel member includes a steel pipe, four steel pipe webs welded to the side walls of the steel pipe, and a K-shaped C-node top plate and bottom plate welded to the upper and lower ends of the steel pipe. The center of the steel pipe is the center of the C-node. The four steel pipe webs are distributed in a K-shape, corresponding to the centerline positions of the four connection ends of the C-node, and are welded to the C-node top plate and bottom plate. Two of the steel pipe webs are arc-shaped plates, arranged along the circumference of the circumferential beam body. The end face dimensions of the four connection ends of the C-node steel member are matched with the end face dimensions of the corresponding beam-shaped steel beams, so as to facilitate butt welding. In the C node, the two curved beam sections, one longitudinal beam section and one transverse beam section connected to the C node, which are within the web height range of the steel beam, are all extended to the surface of the steel tube side wall. The longitudinal beam sections outside the web height range of the two curved beam sections are overlapped and welded accordingly. The longitudinal beam sections outside the web height range of the longitudinal beam section and the transverse beam section are free from the longitudinal beam sections and pass through the longitudinal beam sections outside the web height range of the steel tube at the node, and extend to the surface of the cast-in-place UHPC near the C node.

6. The steel-UHPC composite roof beam according to claim 1, characterized in that: The shear connector is a stud.

7. A steel-UHPC composite roof, characterized in that: The invention comprises the steel-UHPC composite roof beam according to any one of claims 1 to 6, wherein the steel-UHPC composite roof beam is covered with a prefabricated foamed cement board.

8. A construction method for a steel-UHPC composite roof beam according to claim 1, characterized in that: The steps include: S1. Determine the structure and dimensions of the steel-UHPC composite roof beams, determine the locations of each node, and rationally divide the circumferential and linear beams into segments. The steel structure fabrication plant will manufacture the steel beams and node steel components for each beam segment according to the segment division diagram, and complete the layout of shear connectors. Node A and node B steel components will be processed as one piece with the corresponding steel beams, while node C steel components will be independent steel structures. S2. Transport the steel beams of each beam section to the prefabrication yard. Secure and tie a steel mesh around the outer periphery of the steel beams of each beam section. A reserved section is provided for the longitudinal beam reinforcement extending outward from the end of the steel beam. Install formwork for forming the UHPC envelope around the steel mesh. Cast the UHPC and reserve corresponding cast-in-place sections based on the node layout. After steam curing, remove the formwork and air dry at room temperature. This completes the prefabrication of each steel enveloped UHPC beam section. S3. Transport the prefabricated beam segments and C-node steel components to the construction site and assemble them according to the following steps: S31, positioning and laying out the straight beam segments according to the plan layout design drawing of the composite roof beam, and then performing A-node connection construction one by one to assemble into a grid beam; S32, positioning and laying out the curved beam segments according to the plan layout design drawing of the composite roof beam, and then performing B-node connection construction one by one to complete the assembly of the grid beam and the curved beam segments; S33. According to the plan layout design drawing of the composite roof beam, install the C-node steel members in place, and then perform C-node connection construction one by one to complete the overall assembly of the steel-UHPC composite roof beam; S4. Integrally hoist the steel-UHPC composite roof beams to the installation position of the working pit roof and install them in place so that they can be covered with prefabricated foamed cement panels later.

9. The construction method of the steel-UHPC composite roof beam according to claim 8, characterized in that: In step S3, the A node connection construction, the B node connection construction, and the C node connection construction are all carried out in sequence: welding the node steel member to the end of the corresponding beam section steel beam, welding the corresponding longitudinal beam reserved section of the steel bar at the node, tying the steel bars at the node, installing the node formwork, and casting the node UHPC.

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