A roof truss composed of a string beam and a cantilever truss and a construction method thereof

Abstract

The present invention relates to a combined roof truss of a beam string and a cantilever truss and a construction method, comprising a beam string assembly and a cantilever truss assembly mounted on both sides of the beam string assembly; the beam string assembly comprises two beam string main beams in an arc-shaped structure, a plurality of beam string main beam support rods are transversely mounted between the two beam string main beams, and two support connecting frames that can be connected on the same plane are respectively arranged at the left and right ends of the two beam string main beams; the two sides of the two support connecting frames are respectively fixed on the cantilever truss assembly; the present invention has a simple structure and an ingenious design, and a combined roof truss between the beam string assembly and the cantilever truss assembly is a new design for the building roof, which increases the roof area above the columns, and at the same time, the beam string and the cantilever truss use the supports as fulcrums to borrow force from each other, which saves materials and meets the needs of modern building development, and is a new roof truss combination system.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction devices, and in particular relates to a roof truss composed of a string beam and a cantilever truss and a construction method. Background Art

[0002] With the development of society, while private space is gradually expanding, the demand for public building space such as cultural centers, gymnasiums, theaters and other buildings is also increasing. These demands have led to the continuous exploration of building structure systems, especially column-free large-space roof structures, which have attracted more and more attention. The traditional building system can no longer meet human needs. The traditional large-space roof structure only studies and applies the spatial structure within the column, such as span height, and often ignores the use of the space outside the column.

[0003] In recent years, with the needs of my country's economic construction and the improvement of people's living standards, the building system is increasingly developing towards high-rise, large space and large span. However, the existing structural system is single, and most of them are pure beam-string and pure truss applications. Although they can meet the problems of safety, economy and efficiency, they lack artistic elements and aesthetics, and fail to integrate and utilize structural resources to play their due role.

[0004] Improvements need to be made in view of the above technical problems. Summary of the invention

[0005] The present invention aims to overcome the defects in the prior art and provide a combined roof truss of a beam string and a cantilever truss and a construction method which has a simple structure, ingenious design, increases the area of ​​the roof system, improves the space utilization rate of the building system, saves materials, and meets the needs of modern building development.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is: a combined roof truss of a beam string and a cantilever truss, including a beam string assembly and a cantilever truss assembly installed on both sides of the beam string assembly; the beam string assembly includes two beam string main beams with an arc-shaped structure, a plurality of beam string main beam struts are transversely installed between the two beam string main beams, and two support connecting frames that can be connected on the same plane are respectively arranged at the left and right ends of the two beam string main beams; the two sides of the two support connecting frames are respectively fixed to the cantilever truss assembly.

[0007] As a preferred solution of the present invention, the cross-sectional dimensions of the two beam-string main beams gradually decrease from the middle to the two sides thereof; and the plurality of beam-string main beam support rods are respectively configured as a plurality of rectangular rods parallel to each other.

[0008] As a preferred solution of the present invention, the beam-string main beam and the beam-string main beam struts are fixedly connected and integrally formed.

[0009] As a preferred solution of the present invention, it also includes a beam string cable device, which is located at the bottom of the beam string assembly, and two ends of the beam string cable device are respectively connected to the bottom of the support connecting frame.

[0010] As a preferred embodiment of the present invention, the beam string cable device includes at least two cable struts and a beam string cable connected to the bottom of the cable struts; both ends of the beam string cable are arranged at the bottom of the support connecting frame, and the cable struts are arranged at the bottom of the beam string main beam struts.

[0011] As a preferred embodiment of the present invention, the cantilever truss assembly includes a lower chord, an upper chord and a web; the lower chord and the upper chord are arranged in parallel, the web is vertically fixed to the outer ends of the lower chord and the upper chord, and the inner sides of the lower chord and the upper chord are fixed to the supporting connecting frame.

[0012] As a preferred solution of the present invention, a positioning plate is vertically fixed to the middle of the lower chord and the upper chord, and inclined plates are symmetrically arranged on both sides of the positioning plate.

[0013] As a preferred solution of the present invention, the web member, the lower chord member, the upper chord member, the positioning plate and the inclined plate are fixedly connected and integrally formed.

[0014] As a preferred solution of the present invention, the web member, the lower chord member, the upper chord member, the positioning plate and the inclined plate are all H-shaped steels.

[0015] As a preferred solution of the present invention, the support connecting frame includes a top plate, a support plate and a support upright; the top plate is an arc-shaped structure, which is consistent with the arc angle of the tension-string main beam, one end of the top plate is fixedly arranged at the connection between the two tension-string main beams, and the other end of the top plate is fixedly arranged at the top end of the support upright, and the support plate is an arc-shaped structure, one end of the support plate is fixedly arranged at the end of the top plate, and the other end of the support plate is fixedly arranged at the bottom of the support upright.

[0016] A construction method of a combined roof truss of a beam string and a cantilever truss comprises the following steps:

[0017] Step 1: Level the site. The site for assembling the combined roof truss should be first leveled and compacted by machinery, with 300mm gravel laid in the middle and 300mm thick C30 reinforced concrete poured on the top. Ensure that the site is solid enough to withstand the deadweight of the assembling of the string beam and truss and the lifting requirements of the crane;

[0018] Step 2: assemble the beam string truss on the ground; the steel components that have been brought in in advance are transported to the prepared assembly site for assembly after passing the quality inspection. A 25t small crane and a tire frame are used as auxiliary tools for assembling the beam string. The crane assists in the transportation of components; the support uprights on both sides of the beam string are installed at both ends of the beam string, and all components are connected by high-strength bolts. Finally, install the beam string cables and cable struts. When installing the cables, use the cable drum, ground roller and winch to unfold the beam string cables and hang them on both ends of the beam string. Then install the cable struts between the cables and the beam string main beam struts and cables;

[0019] Step 3: Initial ground tensioning of the beam string cables; prepare the assembled beam string for prestressed cable tensioning. The cables are made of 1670MPa high vanadium cables. Before tensioning, check whether the structures between the rods are aligned and whether the high-strength bolts are tightened. The tensioning is done by two YCW-70B through-type hydraulic jacks and one end of the supporting tools. During the tensioning process, check whether the changes of each component are normal.

[0020] Step 4: Lifting of the beam string. The total weight of the beam string is 45t. After the initial ground tensioning is completed, the beam string is hoisted by two large-tonnage truck cranes of the SAC2600 type. The height and position of the cranes are guaranteed to be no more than 75% of the rated lifting capacity.

[0021] Step 5, cantilever truss assembly; assemble the 5-meter-long cantilever trusses on both sides on a flat ground. The horizontal assembly method is used for truss assembly. A 25t small crane and a tire frame are used as auxiliary tools for assembling the beam string. During assembly, the tire frames are stably placed at a distance of 4 meters. When assembling, the upper chord and lower chord of the cantilever truss are assembled first, and the middle web is installed last. The components are connected by welding. The NB-350 welding machine is used for welding. Multi-layer and multi-pass welding is performed to form the final fixation. After welding, repair, grinding and UT test are performed;

[0022] Step 6: Installation of cantilever truss; The weight of a single cantilever truss on one side is 2t. QY130 crane is used for lifting. Both sides of the beam string are lifted successively. The lifting machinery temporarily fixes the outer side of the beam string support column with high-strength bolts when the cantilever truss is hoisted. After the temporary fixation is secure, the crane hook is removed. Under the measurement and monitoring of the surveyor, the axis deviation and elevation deviation are corrected with fall chains and wedges. Finally, the cantilever truss and the beam string support column are finally fixed;

[0023] Step 7: Final tensioning of the beam string cables in the air; after the cantilever truss is finally fixed, the final tensioning of the beam string in the air is carried out;

[0024] Step 8: Install the roof structure. Repeat steps 1 to 7 to form a combined roof truss group of beam string and cantilever truss. The purlins in each span are installed in sequence as each combined roof truss is hoisted. Finally, the roof panel horseway and other components are installed to complete the assembly of the entire roof system. The damaged components are repainted with anti-corrosion and fire-proof topcoat.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention has a simple structure and an ingenious design. The combined roof truss between the beam string assembly and the cantilever truss assembly is a new design for the building roof, which increases the roof area above the column. At the same time, the beam string and the cantilever truss use the support as a fulcrum to borrow force from each other, saving materials and meeting the needs of modern building development. It is a new roof truss combination system;

[0027] 2. The combined roof truss of the beam string and the cantilever truss of the present invention is to overcome the limitation of the roof area, especially the cantilever truss part of the combined roof truss, which increases the area of ​​the roof system, improves the space utilization rate of the building system, and injects the artistry and beauty of the architectural elements;

[0028] 3. The combined system of the beam string and cantilever truss of the present invention has the characteristics of simple structure, clear force transmission, light weight, large span, high construction efficiency, etc. It also has the advantages of combining two materials, rigid rod and flexible cable, and has obvious benefits. It is a new type of combined roof truss;

[0029] 4. The beam string cable device provided in the present invention makes the influence between the beam string and the cantilever truss more balanced, the force is more clear, and the rigidity and force bearing capacity of the structure are enhanced; it can withstand vertical pressure and reverse wind pressure, enhance the effect of the reverse load of the structure, and keep the structure volume at a low level, making the building shape lighter and more flexible; the structure is novel and unique, easy to process, transport and simple and convenient to construct;

[0030] 5. The cantilever truss assembly provided in the present invention ensures that the multiple beam string main beam support rods on the beam string assembly are under the lateral constraints of the structures on both sides of the beam string main beam plane, thereby ensuring the plane stability of the beam string main beam during construction, ensuring the structural rigidity during the construction phase, shortening the overall construction period of the structure, and having good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a side view of the present invention;

[0032] Figure 2 is a top view of the present invention;

[0033] Figure 3 It is a partial enlarged view of the present invention in the direction of A;

[0034] Figure 4 is a hoisting stress diagram of the beam string assembly of the present invention;

[0035] Figure 5 is a stress diagram of the final tensioning member of the beam string cable of the present invention;

[0036] The accompanying drawings are denoted as follows: beam string cable 1, beam string main beam 2, beam string main beam strut 3, cable strut 4, support upright 5, web member 6, lower chord 7, upper chord 8, beam string assembly 10, cantilever truss assembly 20, positioning plate 21, inclined plate 22, support connecting frame 30, top plate 31, support plate 32, beam string cable device 40. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Example:

[0040] like Figure 1-5 As shown, a combined roof truss of a beam string and a cantilever truss comprises a beam string assembly 10 with a clear span of 54 meters and two cantilever truss assemblies 20 with a clear span of 5 meters mounted on both sides of the beam string assembly 10; the beam string assembly 10 comprises two beam string main beams 2 with an arc-shaped structure, and the beam string main beams 2 are rectangular bars (the cross-sectional specifications are 600×200×14×14); a plurality of beam string main beam support rods 3 are transversely mounted between the two beam string main beams 2, and the beam string main beam support rods 3 are rectangular bars (the cross-sectional specifications are 600×200×14×14); two support connecting frames 30 that can be connected on the same plane are respectively arranged at the left and right ends of the two beam string main beams 2; and the two sides of the two support connecting frames 30 are respectively fixed to the cantilever truss assembly 20.

[0041] The present invention has a simple structure and an ingenious design. The combined roof truss between the beam string assembly and the cantilever truss assembly is a new design for the building roof, which increases the roof area above the columns. At the same time, the beam string and the cantilever truss use the supports as fulcrums to leverage each other, saving materials and meeting the needs of modern building development. It is a new roof truss combination system.

[0042] Specifically, the cross-sectional dimensions of the two beam-string main beams 2 gradually decrease from the middle to the two sides thereof; this can further increase the usable space within the structure; the beam-string main beams 2 can withstand vertical pressure and reverse wind pressure, and enhance the effect of the reverse load of the structure; and the plurality of beam-string main beam support rods 3 are respectively configured as a plurality of rectangular rods parallel to each other.

[0043] The combined roof truss of the beam string and the cantilever truss of the present invention is to overcome the limitation of the roof area, especially the cantilever truss part of the combined roof truss, which increases the area of ​​the roof system, improves the space utilization rate of the building system, and injects the artistry and beauty of the architectural elements.

[0044] The beam string main beam 2 and the beam string main beam support rod 3 are fixedly connected and formed in one piece; the structural strength and overall firmness of the beam string assembly 10 are improved, and the safety of use is further ensured.

[0045] A combined roof truss of a beam string and a cantilever truss, further comprising a beam string cable device 40, the beam string cable device 40 being located at the bottom of the beam string assembly 10, and the two ends of the beam string cable device 40 being respectively connected to the bottom of a support connecting frame 30; the beam string cable device provided in the present invention makes the influence between the beam string and the cantilever truss more balanced, the force being more clearly received, and the rigidity and force-bearing capacity of the structure enhanced; it can withstand vertical pressure and reverse wind pressure, enhance the effect of reverse load of the structure, and can keep the structure volume at a relatively low level, making the building shape lighter and more flexible; the structure is novel and unique, and is easy to process, transport and construct simply and conveniently;

[0046] Specifically, the beam string cable device 40 includes at least two cable struts 4 and a beam string cable 1 connected to the bottom of the cable struts 4; both ends of the beam string cable 1 are arranged at the bottom of the support connecting frame 30, and the cable struts 4 are arranged at the bottom of the beam string main beam strut 3; wherein the beam string cable struts 4 are circular tube-shaped, and the cross-sectional specifications thereof are φ140×8; the beam string cable 1 adopts φ95 high vanadium cable, and the tensile strength grade is 1670Mpa.

[0047] The cantilever truss assembly 20 includes a lower chord 7, an upper chord 8 and a web 6; the lower chord 7 and the upper chord 8 are arranged in parallel, the web 6 is vertically fixed to the outer ends of the lower chord 7 and the upper chord 8, and the inner sides of the lower chord 7 and the upper chord 8 are fixed to the support connecting frame 30; the cantilever truss assembly provided in the present invention ensures that the multiple beam-string main beam support rods on the beam-string assembly are under the lateral constraints of the structures on both sides of the beam-string main beam plane, thereby ensuring the plane stability of the beam-string main beam during construction, ensuring the structural rigidity of the construction stage, shortening the overall construction period of the structure, and having good economic benefits.

[0048] Specifically, a positioning plate 21 is vertically fixed to the middle of the lower chord 7 and the upper chord 8, and inclined plates 22 are symmetrically arranged on both sides of the positioning plate 21; the web 6, the lower chord 7, the upper chord 8, the positioning plate 21 and the inclined plate 22 are fixedly connected and formed as one piece; the structural strength and overall firmness of the cantilever truss assembly 20 are improved, and the safety of use is further guaranteed.

[0049] The web member 6, the lower chord member 7, the upper chord member 8, the positioning plate 21 and the inclined plate 22 are all H-shaped steels. Among them, the specifications of the upper chord member 8 and the lower chord member 7 are: 400×150×8×8, and the specifications of the web member 6 are: 120×80×6×6).

[0050] The support connecting frame 30 includes a top plate 31, a support plate 32 and a support upright 5; the top plate 31 is an arc-shaped structure, which is consistent with the arc angle of the tension-string main beam 2, one end of the top plate 31 is fixedly arranged at the connection between the two tension-string main beams 2, and the other end of the top plate 31 is fixedly arranged at the top of the support upright 5, the support plate 32 is an arc-shaped structure, one end of the support plate 32 is fixedly arranged at the end of the top plate 31, and the other end of the support plate 32 is fixedly arranged at the bottom of the support upright 5; wherein, the support upright 5 is a rectangular rod, and its specifications are: 500×500×35×35.

[0051] The combined system of the beam string and cantilever truss of the present invention has the characteristics of simple structure, clear force transmission, light weight, large span, high construction efficiency, etc., and has the advantage of combining two materials of rigid rods and flexible cables, with obvious benefits, and is a new type of combined roof truss.

[0052] In a roof truss composed of a beam string and a cantilever truss, the specific construction steps include: the beam string is mainly assembled on the ground; first, the auxiliary assembly tool frame is welded, and the frame is generally placed at a distance of 4 meters along the direction in which the beam string is to be assembled and the foundation is stabilized, and a 25t small crane is used to transport the beam string and the cantilever truss components, and the auxiliary components are assembled. When assembling the beam string, first assemble the beam string main beam 2, the beam string main beam support rod 3 and the support upright rod 5, and assemble the unit components into a whole, and then assemble the beam string cable support rod 4 and the beam string cable 1. After the assembly is completed, check whether the structures between the rods are aligned and whether the high-strength bolts are tightened. After confirmation, start the initial tensioning of the beam string ground cable to 60% of the cable design value. The lifting machinery test-lifts the assembled and initially tensioned beam string, and hoists the entire structure to the roof for fixing. Continue to assemble the cantilever truss. During the assembly, the auxiliary tool frame is still used. First, assemble the lower chord 7 and the upper chord 8 of the cantilever truss, and then assemble the middle web 6 of the cantilever truss. Finally, hoist and fix them to both sides of the tension beam, and start the secondary tensioning of the tension beam cable in the air to 105% of the cable force design value, finally forming a combined roof truss of the tension beam and the cantilever truss.

[0053] Overview of specific construction methods: site leveling → ground assembly of beam string trusses → initial ground tensioning of beam string cables → lifting of beam string → assembly of cantilever trusses → lifting and installation of cantilever trusses → final aerial tensioning of beam string cables → installation of roof structure.

[0054] Specific construction steps:

[0055] Construction preparation;

[0056] 1.1 Temporary water and electricity, use three-phase five-wire system to set up construction power lines, set up nighttime construction lighting fixtures. Connect water pipes according to the water demand on site to ensure that concrete maintenance meets the demand.

[0057] 1.2 Site requirements: level the site for assembling the beam string and cantilever truss, and be able to withstand the deadweight of the beam string and cantilever truss and the bearing capacity requirements of the lifting crane.

[0058] 1.3 Construction machinery: 2 SAC2600 cranes are used for beam string hoisting, 1 QY130 crane is used for cantilever trusses, and 2 QY25 25t cranes are used for component assembly to meet the use requirements. 2 YCW-70B through-type hydraulic jacks and supporting tools are used for beam string prestressed cables to meet the requirements for beam string cable tensioning. NB-350 welding machine is used for welding between steel structure components. Other auxiliary tools, etc.

[0059] Specifically, a construction method of a combined roof truss of a beam string and a cantilever truss comprises the following steps:

[0060] Step 1: Level the site. The site for assembling the combined roof truss should be first leveled and compacted by machinery, with 300mm gravel laid in the middle and 300mm thick C30 reinforced concrete poured on the top. Ensure that the site is solid enough to withstand the deadweight of the assembling of the string beam and truss and the lifting requirements of the crane.

[0061] Step 2: The truss string is assembled on the ground. The steel components that have been brought in in advance are transported to the prepared assembly site for assembly after passing the quality inspection. A 25t small crane and a tire frame are used as auxiliary tools for assembling the beam string. The crane assists in the transportation of components, and the tire frame prevents the beam string from internal or local settlement deformation due to its own weight. As a support point, during assembly, the tire frame is stably placed at a spacing of 4 meters according to the length of the beam string. A 25t small crane is used to equilibrate the main beam of the beam string and the beam string support components from the middle of the beam along the end of the beam, and then the support uprights on both sides of the beam string are installed at both ends of the beam string. All components are connected by high-strength bolts. Finally, the beam string cable and cable support rod are installed. When installing the cable, the cable drum, ground roller and winch are used to unfold the coiled beam string cable and hang it on both ends of the beam string, and then the cable support rod is installed between the cable and the main beam support rod and cable.

[0062] Step 3: Initial ground tensioning of the beam string cable; the assembled beam string is prepared for prestressed cable tensioning. The cable uses 1670MPa high vanadium cable. Before tensioning, check whether the structure between the rods is aligned and whether the high-strength bolts are tightened. The tensioning uses two through-type hydraulic jacks YCW-70B and one end of the supporting tool. During the tensioning process, check whether the changes of each component are normal. In order to ensure the stiffness during hoisting and prevent the internal stress changes of the components from causing changes in the beam string structure, the finite element analysis software SAP2000V22.0.0 is used. Considering the nonlinear effect of the structure, the influence of the cable prestress and P-△ effect is considered in the calculation. It is determined that the initial ground tensioning should be 60% of the cable design value. It cannot be over-tensioned. The tensioning is mainly controlled by cable force, supplemented by deformation control and verticality control of the strut. After the tensioning is completed, the cable force deviation is no more than 5%, and the verticality deviation of the cable strut is no more than 1 / 200.

[0063] Step 4: Lifting of the beam string; The total weight of the beam string is 45t. After the initial ground tensioning is completed, the beam string is hoisted by two large-tonnage truck cranes of the SAC2600 type. The height and position of the cranes are guaranteed to be no more than 75% of the rated lifting capacity. The lifting points are analyzed according to the professional spatial steel structure system MIDASGen software. During the lifting process, the coordinated operation of the two large machines should be controlled. A trial lifting should be carried out before the beam string is lifted. The lifting speed should be uniform and slow. The beam string support pole should be lifted about 300-500mm above the top position of the seismic support before being installed on the column top seismic support. Then the beam string support pole should be slowly lowered to the column top seismic support. The installation alignment should be based on the positioning axis and temporarily fixed. After the temporary fixation is secure, remove the crane hook, and under the measurement and supervision of the surveyor, use jacks, fall chains and wedges to correct its axis deviation and elevation deviation. Finally, weld the support upright to the seismic support. Use NB-350 welding machine for welding, and perform multi-layer and multi-pass welding to form the final fixation. After welding, repair, polishing and UT test are carried out.

[0064] Step five, cantilever truss assembly; continue to assemble the 5-meter-long cantilever trusses on both sides on the flat ground. The horizontal assembly method is adopted for the truss assembly. A 25t small crane and a tire frame are used as auxiliary tools for the assembly of the beam string. During assembly, the tire frames are stably placed at a distance of 4 meters. When assembling, the upper and lower chords of the cantilever truss are assembled first, and the middle web members are installed last. The components are connected by welding. NB-350 welding machine is used for welding. Multi-layer and multi-pass welding is performed to form the final fixation. After welding, repair, polishing and UT test are carried out.

[0065] Step six, cantilever truss hoisting installation; the weight of a single-sided cantilever truss is 2t, and a QY130 crane is used for hoisting. The two sides of the beam string are hoisted in turn. The hoisting machinery uses high-strength bolts to temporarily fix the outer side of the beam string support upright when the cantilever truss is hoisted. After the temporary fixation is secure, the crane hook is removed, and under the measurement and supervision of the surveyor, the axis deviation and elevation deviation are corrected with a fall chain and wedge, and finally the cantilever truss and the beam string support upright are finally fixed.

[0066] Step 7: Final tensioning of the beam string cable in the air; After the cantilever truss is finally fixed, the final tensioning of the beam string in the air is carried out. In order to prevent the weight of the purlin roof panel on the subsequent roof truss from affecting the installation of the combined roof truss, the finite element analysis software SAP2000V22.0.0 is used to consider the nonlinear effect of the structure, and the influence of the cable prestress and P-△ effect is considered in the calculation. The tension value of the final cable is determined to exceed the design value of the tensioned cable by 5%. During tensioning, two through-type hydraulic jacks YCW-70B and supporting tools are used for tensioning at one end. With the help of a suspended operating platform in the air, the cable tensioning control adopts the principle of force control as the main and shape control as the auxiliary, mainly controlling the cable force, and controlling the vertical deformation in the mid-span on the basis of the prestress. During the tensioning process, the deformation of each component should be strictly tested to prevent irreversible deformation until the tension reaches 105% of the design value of the cable.

[0067] Step 8: Install the roof structure. Repeat steps 1 to 7 to form a combined roof truss group of beam string and cantilever truss. The purlins in each span are installed in sequence as each combined roof truss is hoisted. Finally, the roof panel horseway and other components are installed to complete the assembly of the entire roof system. The damaged components are repainted with anti-corrosion and fire-proof topcoat.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention; therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0069] Although the following terms are frequently used in this document: beam string cable 1, beam string main beam 2, beam string main beam strut 3, cable strut 4, support upright 5, web member 6, lower chord 7, upper chord 8, beam string assembly 10, cantilever truss assembly 20, positioning plate 21, inclined plate 22, support connecting frame 30, top plate 31, support plate 32, beam string cable device 40, etc., the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A roof truss composed of a beam string and a cantilever truss, characterized in that: The invention comprises a beam string assembly (10) and a cantilever truss assembly (20) mounted on both sides of the beam string assembly (10); the beam string assembly (10) comprises two beam string main beams (2) with an arc-shaped structure, a plurality of beam string main beam support rods (3) are transversely mounted between the two beam string main beams (2), and two support connection frames (30) that can be connected on the same plane are respectively arranged at the left and right ends of the two beam string main beams (2); the two sides of the two support connection frames (30) are respectively fixed to the cantilever truss assembly (20); the cantilever truss assembly (20) comprises a lower chord (7), an upper chord (8) and a web (6); the lower chord (7) and the upper chord (8) are arranged in parallel, the web (6) is vertically fixed to the outer ends of the lower chord (7) and the upper chord (8), and the inner sides of the lower chord (7) and the upper chord (8) are fixed to the support connection frame (30); the lower chord (7) A positioning plate (21) is fixedly provided perpendicularly to the middle of the upper chord (8), and inclined plates (22) are symmetrically arranged on both sides of the positioning plate (21); the cross-sectional dimensions of the two tension beam main beams (2) gradually decrease from the middle to the two sides thereof; the plurality of tension beam main beam support rods (3) are respectively provided as a plurality of mutually parallel rectangular rods; the support connecting frame (30) comprises a top plate (31), a support plate (32) and a support upright rod (5); the top plate (31) is an arc-shaped structure, which is consistent with the arc angle of the tension beam main beam (2); one end of the top plate (31) is fixedly provided at the connection between the two tension beam main beams (2), and the other end of the top plate (31) is fixedly provided at the top end of the support upright rod (5); the support plate (32) is an arc-shaped structure, one end of the support plate (32) is fixedly provided at the end of the top plate (31), and the other end of the support plate (32) is fixedly provided at the bottom of the support upright rod (5); and the tension beam cable device (40) is also included.

2. The combined roof truss of beam string and cantilever truss according to claim 1, characterized in that: The beam string main beam (2) is fixedly connected to the beam string main beam support rod (3).

3. The combined roof truss of beam string and cantilever truss according to claim 2, characterized in that: The beam string cable device (40) is located at the bottom of the beam string assembly (10), and two ends of the beam string cable device (40) are respectively connected to the bottom of the support connection frame (30).

4. The combined roof truss of beam string and cantilever truss according to claim 3, characterized in that: The beam string cable device (40) comprises at least two cable struts (4) and a beam string cable (1) connected to the bottom of the cable struts (4); both ends of the beam string cable (1) are arranged at the bottom of a support connecting frame (30), and the cable struts (4) are arranged at the bottom of a beam string main beam strut (3).

5. The combined roof truss of beam string and cantilever truss according to claim 1, characterized in that: The web member (6), the lower chord member (7), the upper chord member (8), the positioning plate (21) and the inclined plate (22) are fixedly connected.

6. The combined roof truss of beam string and cantilever truss according to claim 5, characterized in that: The web member (6), the lower chord member (7), the upper chord member (8), the positioning plate (21) and the inclined plate (22) are all H-shaped steels.

7. A construction method of a combined roof truss of a beam string and cantilever truss as claimed in claim 4, characterized in that: The following steps are involved: Step 1: Level the site. The site for assembling the combined roof truss should be first leveled and compacted by machinery, with 300mm gravel laid in the middle and a 300mm thick C30 reinforced concrete layer poured on the top. Ensure that the site is solid enough to withstand the deadweight of the assembling of the string beam and truss and the lifting requirements of the crane. Step 2: assemble the beam string truss on the ground; the steel components that have been brought in in advance are transported to the prepared assembly site for assembly after passing the quality inspection. A 25t small crane and a tire frame are used as auxiliary tools for assembling the beam string, and the crane assists in the transportation of components; the support uprights on both sides of the beam string are installed at both ends of the beam string, and all components are connected by high-strength bolts; finally, the beam string cables and cable stays are installed. When installing the cables, the cable drum, ground roller and winch are used to unfold the coiled beam string cables and hang them on both ends of the beam string, and then the cable stays are installed between the cables and the beam string main beam stays and cables; Step 3: Initial ground tensioning of the beam string cables; prepare the assembled beam string for prestressed cable tensioning. The cables are made of 1670MPa high vanadium cables. Before tensioning, check whether the structures between the rods are tightened with high-strength bolts. Two YCW-70B through-type hydraulic jacks and supporting tools are used for tensioning. During the tensioning process, check whether the changes of each component are normal. Step 4: Lifting of the beam string. The total weight of the beam string is 45t. After the initial ground tensioning is completed, the beam string is hoisted by two large-tonnage truck cranes of the SAC2600 type. The height and position of the cranes are guaranteed to be no more than 75% of the rated lifting capacity. Step 5, cantilever truss assembly; assemble the 5-meter-long cantilever trusses on both sides on a flat ground. The horizontal assembly method is used for truss assembly. A 25t small crane and a tire frame are used as auxiliary tools for assembling the beam string. During assembly, the tire frames are stably placed at a distance of 4 meters. When assembling, the upper chord and lower chord of the cantilever truss are assembled first, and the middle web is installed last. The components are connected by welding. The NB-350 welding machine is used for welding. Multi-layer and multi-pass welding is performed to form the final fixation. After welding, repair, grinding and UT test are performed; Step 6: Installation of cantilever truss; The weight of a single cantilever truss on one side is 2t. A QY130 crane is used for lifting. The two sides of the beam string are lifted successively. The crane temporarily fixes the outer side of the beam string support column with high-strength bolts when the cantilever truss is hoisted. After the temporary fixation is secure, the crane hook is removed. Under the measurement and monitoring of the surveyor, the axis deviation and elevation deviation are corrected with a fall chain and a wedge. Finally, the cantilever truss and the beam string support column are finally fixed; Step 7: Final tensioning of the beam string cables in the air; after the cantilever truss is finally fixed, the final tensioning of the beam string in the air is carried out; Step 8: Install the roof structure. Repeat steps 1 to 7 to form a combined roof truss group of beam string and cantilever truss. The purlins in each span are installed in sequence as each combined roof truss is hoisted. Finally, the roof panel runway components are installed to complete the assembly of the entire roof system. The damaged components are repainted with anti-corrosion and fire-proof topcoat.

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