A structural system and design method for urban rail transit cover

Abstract

The present invention discloses a structural system and design method of an urban rail transit upper cover. The internal frame of the lower cover structure is arranged within the vertical projection range of the tower, and the outer frame of the lower cover structure is arranged outside the vertical projection range of the tower. The internal frame and the outer frame are connected, and the internal frame is mainly composed of steel-concrete composite columns and steel-concrete composite beams arranged between the steel-concrete composite columns; the outer frame is mainly composed of concrete columns and concrete beams arranged between the concrete columns, and the upper cover structure is mainly composed of vertical load-bearing components and steel beams arranged between the vertical load-bearing components; the upper cover structure adopts a frame shear wall structure of steel frame-steel plate shear wall. The upper cover structure of the present invention can reduce the mass of the floor and greatly reduce the cost of the foundation. The use of the steel frame-steel plate shear wall structure can greatly reduce the cross-sectional size of the beam and column compared with the traditional concrete frame structure, thereby improving the spatial effect of the building.

Description

Technical Field

[0001] The invention belongs to the technical field of building structures, and in particular relates to a structural system and a design method for a city rail transit upper cover. Background Art

[0002] With the continuous advancement of China's urbanization process, the urban population has grown rapidly, which has put forward higher requirements for urban transportation. Rail transit, as an efficient and large-capacity transportation mode, can effectively alleviate urban traffic congestion and improve urban transportation efficiency. The subway depot is one of the components of the urban rail transit system. As the supporting infrastructure of the subway system, its main function is to provide necessary logistics services for the daily operation of subway vehicles, and is responsible for the parking, inspection, preparation, operation, repair and management of subway vehicles. Since the subway depot occupies a large area, it has an important impact on urban intensive land use, overall planning, landscape environment and other aspects. Therefore, in recent years, more and more cities in China have begun to pay attention to and explore the comprehensive development of subway depots, so as to effectively achieve resource sharing, improve intensive land use and reduce development costs.

[0003] At present, most of the domestic subway superstructures adopt concrete structure. However, due to the particularity of subway functions, the number of ground-to-ground shear walls in the upper development often fails to meet the requirements of ground-to-ground shear walls in some frame-supported shear walls as required by the code. Especially in the vehicle base, shear walls cannot be arranged in the substructure, and a pure frame structure is adopted. According to the process requirements, the parking area height is generally about 10m, and the maintenance area height is generally about 15m. The huge difference in floor height brings about a large difference in floor stiffness, making it difficult for the lateral stiffness ratio of the slab-to-ground structure layer to the adjacent upper layer to meet the requirements of the code.

[0004] In order to meet the requirements of the code on the stiffness ratio, when conventional concrete structures are used, the upper structure mostly adopts a concrete frame structure. Because the cross-section of the frame beams and columns is large, it has a certain impact on the use of the upper development format. When the upper format is a residential building such as a house or apartment, the frame columns and frame beams will protrude from the room more, which will have a greater impact on the use effect. In addition, the existing "Urban Rail Transit Upper Cover Structure Design Standard" T / CECS1035 only requires that the stiffness ratio of the lower cover and the upper cover structure be controlled to be no less than 0.5, which may not guarantee that the plastic hinge will appear in the upper cover part under the action of an earthquake, and it is difficult to achieve the expected yield mechanism. Therefore, it is urgent to research and develop a new structural system and design method to improve living space and improve structural safety. Summary of the invention

[0005] In order to solve the problems existing in the background technology, improve the quality of rail transit cover development, and enhance living comfort, the purpose of the present invention is to provide a structural system and design method for urban rail transit cover. The present invention provides a structural system and design method with a small cross-section of the cover structure components, which reduces the difference in structural stiffness between the cover and the undercover structure, has high structural safety, and is economical and practical.

[0006] The technical solution adopted by the present invention is as follows:

[0007] 1. A structural system for urban rail transit roof:

[0008] The structural system includes an under-cover structure and an over-cover structure. The under-cover structure includes an outer frame and an inner frame. The outer frame is located at the periphery of the under-cover structure, and the inner frame is located at the inside of the under-cover structure. The inner frame is arranged within the vertical projection range of the tower, and the outer frame is arranged outside the vertical projection range of the tower. The inner frame and the outer frame are connected. The inner frame is mainly composed of steel-concrete composite columns and steel-concrete composite beams arranged between the steel-concrete composite columns. The outer frame is mainly composed of concrete columns and concrete beams arranged between the concrete columns. The over-cover structure is mainly composed of vertical load-bearing components and steel beams arranged between the vertical load-bearing components.

[0009] The inner frame and the outer frame respectively adopt a steel-concrete frame structure and a concrete frame structure, and the cover structure adopts a frame shear wall structure of a steel frame-steel plate shear wall.

[0010] The internal frame in the undercover structure includes steel-concrete composite columns and steel-concrete composite beams, and two adjacent steel-concrete composite columns, between a steel-concrete composite column and a steel-concrete composite beam, and between two adjacent steel-concrete composite beams are all connected by steel-concrete composite beams; the peripheral frame includes concrete columns and concrete beams, and two adjacent concrete columns, between a concrete column and a concrete beam, and between two adjacent concrete beams are all connected by concrete beams;

[0011] The steel-concrete composite columns of the internal frame and the concrete columns of the peripheral frame, as well as the steel-concrete composite beams of the internal frame and the concrete columns are connected by concrete beams, and the steel-concrete composite columns and the concrete beams of the peripheral frame, as well as the steel-concrete composite beams and the concrete beams are connected by concrete beams.

[0012] The cover structure includes load-bearing columns, steel beams and steel plate shear walls; two adjacent load-bearing columns, between a load-bearing column and a steel beam, and between two adjacent steel beams can be connected by steel beams. The steel plate shear wall serves as a horizontal load-bearing component, is arranged between two adjacent load-bearing columns, and stiffening ribs are provided on both sides of the steel plate shear wall.

[0013] The steel plate shear wall uses a single steel plate, and the stiffening ribs are used to solve the stability of the single steel plate and improve the shear bearing capacity of the steel plate shear wall. Blocks are also provided on both sides of the steel plate shear wall to protect the steel plate of the steel plate shear wall from corrosion, fire, etc. Infill walls are also provided in the cover structure. The infill walls do not bear loads and are only used to enclose and separate functional spaces. The steel plate shear wall is located inside the infill walls.

[0014] The steel-concrete composite columns in the internal frame are steel-concrete columns or steel tube concrete columns, and the steel sections arranged in the steel-concrete columns are H-shaped steel or cross-shaped steel; the steel-concrete composite beams in the internal frame are steel-concrete beams with rectangular cross sections, and the steel sections arranged in the steel-concrete beams are H-shaped steel;

[0015] The load-bearing columns of the cover structure are steel columns or steel tube concrete columns filled with high-strength self-compacting concrete. The cross-section of the load-bearing columns is one of H-type, rectangular, circular, T-type, L-type and cross-type. The width of the load-bearing columns is smaller than the width of the filling wall in the cover structure, so that the load-bearing columns can be arranged in the filling wall.

[0016] The steel beam of the cover structure is a narrow-flange H-shaped steel, and the flange width of the steel beam is not greater than the width of the load-bearing column.

[0017] The thickness of a single steel plate of the steel plate shear wall in the cover structure is 4 mm to 8 mm.

[0018] 2. A design method for a structural system of an urban rail transit roof comprises the following steps:

[0019] Step S1: First, according to the function of the vehicle base in urban rail transit, the column grid layout of the undercover structure is determined;

[0020] Step S2, then determine the column grid layout of the roof structure according to the function of the roof development business format in urban rail transit;

[0021] Step S3, establishing a three-dimensional finite element model in finite element software according to the column grid arrangement and load of the under-cover structure and the over-cover structure;

[0022] Step S4, combining the building function and the building wall layout, and then setting and constructing the types and sizes of beams, columns, and shear wall components in the three-dimensional finite element model according to the structural system of the urban rail transit cover, while making sure that each component in the cover structure does not protrude from the building wall to meet the requirements of the use function;

[0023] Step S5, using finite element software to perform mechanical property simulation calculations on the three-dimensional finite element model of the structural system constructed in step S4, to determine whether the current three-dimensional finite element model meets the bearing capacity design requirements; if so, the current three-dimensional finite element model is used to set the structural system of the urban rail transit cover; if not, return to step S4 to reset the size, type and arrangement of each component until the three-dimensional finite element model meets the bearing capacity design requirements.

[0024] The step S5 is specifically as follows:

[0025] Step S5.1: First, use finite element software to simulate and verify the overall stiffness of the three-dimensional finite element model constructed in step S4:

[0026] If the stiffness of the lower cover structure and the upper cover structure both meet the stiffness design requirements, proceed to step S5.2;

[0027] Otherwise, return to step S4 to reset the size, type and arrangement of each component until the overall stiffness of the lower cover structure and the upper cover structure meets the design requirements;

[0028] Step S5.2, simulate and verify the structural stiffness ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model:

[0029] If the lateral stiffness ratio between the slab-ground structure layer and the upper cover structure layer adjacent to the slab-ground structure layer is not less than 0.8, it indicates that the structural stiffness ratio between the lower cover structure and the upper cover structure meets the design requirements, and the process proceeds to step S5.3;

[0030] Otherwise, return to step S4 to reset the size, type and arrangement of each component, and repeat steps S4 to S5.2 until the structural stiffness ratio between the lower cover structure and the upper cover structure meets the design requirements;

[0031] The plate ground structure layer is the topmost structure layer in the structure under the cover;

[0032] Step S5.3, simulate and verify the shear bearing capacity ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model:

[0033] If the shear bearing capacity ratio between the slab-ground structure layer and the cover structure layer adjacent to the slab-ground structure layer is not less than 1.0, it indicates that the shear bearing capacity ratio between the cover structure and the cover structure meets the design requirements, and the size, type and arrangement of each component in the urban rail transit cover are set using the current three-dimensional finite element model;

[0034] Otherwise, return to step S4 to reset the size, type and arrangement of each component, and repeat steps S4 to S5.3 until the shear bearing capacity ratio between the under-cover structure and the over-cover structure meets the design requirements.

[0035] The technical principles of the present invention are as follows:

[0036] The inter-story displacement angle control of steel structure is looser than that of concrete structure. The concrete structure under the roof and the steel structure on the roof can easily meet the requirements of the code for the lateral stiffness of the overall structure, avoiding the use of seismic isolation due to unsatisfactory stiffness ratios. Compared with ordinary steel frame structures, the steel frame-steel plate shear wall form can greatly improve the overall lateral stiffness of the structure. While meeting the stiffness requirements of the code, it shares the lateral load, reduces the horizontal effect borne by the frame part, and makes the cross-section of the steel column smaller. The use of narrow rectangular steel pipe columns or T-shaped, L-shaped and other special-shaped columns can be hidden in the building wall, which can well meet the use requirements of residential buildings.

[0037] The shear wall in the steel frame-steel plate shear wall is made of thin steel plates. The thin steel plates have low stiffness and low shear bearing capacity, which makes it easy to control the stiffness ratio and shear bearing capacity ratio of the structures above and below the cover. It is also a ductile wall panel with good performance. Under the action of earthquakes, it can improve the seismic performance of the building structure. For the conversion structure of the rail transit cover, it improves the energy consumption capacity under earthquakes and reduces the seismic response of the structure below the cover.

[0038] The thin steel plate shear wall in the steel frame-steel plate shear wall structure does not bear vertical force. During conversion, it only needs to meet the plane stiffness within the floor and transfer the horizontal force to the vertical components under the cover through the floor surface. The conversion beam only needs to convert the upper columns, making the design of the conversion structure easier, thereby reducing the cost and reducing the difficulty of developing the entire rail transit cover structure.

[0039] The upper cover adopts a steel frame-steel plate shear wall structure, and the lower cover adopts a concrete (steel) frame structure as the overall structural form, adopting a more reasonable structural combination form, and proposing control indicators different from the existing ones for the control of the lateral stiffness ratio and shear bearing capacity ratio between the lower cover structure and the upper cover structure, so that in the seismic performance analysis, the lower cover structure has a higher bearing capacity than the upper cover structure, and the plastic hinge of the overall structure under the action of earthquake appears at the bottom of the upper cover structure, but not in the lower cover structure, which is conducive to realizing the expected yield mechanism. The structural system of the present invention makes the lateral stiffness of the overall structure of the building on the rail transit cover smaller and the basic period longer while meeting the safety requirements, thereby reducing the earthquake effect, reducing the occurrence of earthquake damage, and improving the safety of the structure.

[0040] The beneficial effects of the present invention are:

[0041] 1. In the present invention, within the scope of the tower, the lateral stiffness ratio of the slab-ground structure layer to the adjacent layer on the cover is greater than 0.8, exceeding the requirement of 0.5 in the specification, making the vertical stiffness of the overall structure more uniform, avoiding the use of seismic isolation building forms, and facilitating design, construction and operation and maintenance in the later use stage.

[0042] 2. The steel structure used on the cover of the present invention can reduce the floor mass by 30%, making the design of the transfer layer easier; the reduction of vertical force can also significantly reduce the cost of the foundation.

[0043] 3. The present invention adopts a steel frame-steel plate shear wall structure, so that the cross-sectional size of beams and columns can be greatly reduced compared with the traditional concrete frame structure. Most of the columns and beams can be hidden in the walls of the building, which improves the spatial effect of the building, especially for residential buildings, avoids the occurrence of protruding beams and columns, and greatly improves the quality of the building. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a structural plan view of the under-cover structure of the present invention;

[0045] Figure 2 It is a structural plan view of the cover structure of the present invention;

[0046] Figure 3 It is a diagram of the arrangement of the steel plates in the shear wall of the cover structure of the present invention;

[0047] Figure 4 It is an overall schematic diagram of the structural system of the urban rail transit upper cover of the present invention;

[0048] Figure 5 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with specific implementation cases. The following implementation cases will help those skilled in the art to further understand the present invention, but will not limit the present invention in any form.

[0050] like Figure 1-Figure 3 As shown, the structural system includes an under-roof structure and an over-roof structure. The under-roof structure includes an outer frame and an internal frame. The outer frame is located at the periphery of the under-roof structure, and the internal frame is located inside the under-roof structure. The internal frame is arranged within the vertical projection range of the tower, and the outer frame is arranged outside the vertical projection range of the tower. The internal frame and the outer frame are connected; the internal frame is mainly composed of steel-concrete composite columns and steel-concrete composite beams arranged between the steel-concrete composite columns; the outer frame is mainly composed of concrete columns and concrete beams arranged between the concrete columns; the over-roof structure is mainly composed of vertical load-bearing components and steel beams arranged between the vertical load-bearing components.

[0051] The internal frame and the outer frame adopt steel-concrete frame structure and concrete frame structure respectively, and the cover structure adopts the frame shear wall structure of steel frame-steel plate shear wall.

[0052] The internal frame in the undercover structure includes steel-concrete composite columns and steel-concrete composite beams. Two adjacent steel-concrete composite columns, steel-concrete composite columns and steel-concrete composite beams, and two adjacent steel-concrete composite beams are connected by steel-concrete composite beams. The external frame includes concrete columns and concrete beams. Two adjacent concrete columns, concrete columns and concrete beams, and two adjacent concrete beams are connected by concrete beams.

[0053] The steel-concrete composite columns of the internal frame and the concrete columns of the peripheral frame, as well as the steel-concrete composite beams of the internal frame and the concrete columns are connected by concrete beams, and the steel-concrete composite columns and the concrete beams of the peripheral frame, as well as the steel-concrete composite beams and the concrete beams are connected by concrete beams.

[0054] The structure above the cover includes load-bearing columns, steel beams and steel plate shear walls. Two adjacent load-bearing columns, between a load-bearing column and a steel beam, and between two adjacent steel beams can be connected by steel beams. The steel plate shear wall serves as a horizontal load-bearing member. The steel plate shear wall is arranged between two adjacent load-bearing columns, and stiffening ribs are provided on both sides of the steel plate shear wall.

[0055] The steel plate shear wall uses a single steel plate, and the stiffening ribs are used to solve the stability of the single steel plate and improve the shear bearing capacity of the steel plate shear wall. Blocks are also provided on both sides of the steel plate shear wall to protect the steel plate of the steel plate shear wall from corrosion, fire, etc. Infill walls are also provided in the cover structure. The infill walls do not bear loads and are only used to enclose and separate functional spaces. The steel plate shear wall is located inside the infill walls.

[0056] The steel-concrete composite columns in the internal frame are steel-concrete columns or steel tube concrete columns, and the steel sections arranged in the steel-concrete columns are H-shaped steel or cross-shaped steel; the steel-concrete composite beams in the internal frame are steel-concrete beams with rectangular cross sections, and the steel sections arranged in the steel-concrete beams are H-shaped steel;

[0057] The load-bearing columns of the cover structure are steel columns or steel tube concrete columns filled with high-strength self-compacting concrete. The cross-section of the load-bearing columns is one of H-type, rectangular, circular, T-type, L-type and cross-type. The width of the load-bearing columns is smaller than the width of the infill wall, so that the load-bearing columns can be arranged inside the infill wall.

[0058] The steel beams of the cover structure are made of narrow flange H-shaped steel, and the flange width of the steel beam is not greater than the width of the load-bearing column.

[0059] The thickness of the steel plate shear wall in the cover structure is 4 mm to 8 mm.

[0060] This embodiment provides an overall structural method for rail transit upper cover, and the lower cover structure adopts a frame structure, such as Figure 1 In the upper tower area, steel-concrete frames are used. The columns are steel-concrete columns with cross-shaped steel. Frame beams are directly connected between the columns. The columns and beams together form a frame structure. The frame beams are steel-concrete beams with H-shaped steel. Secondary beams are arranged between the frame beams according to the needs of the upper structure. The secondary beams are also steel-concrete beams with H-shaped steel. Rectangular concrete columns and concrete beams are used in the area outside the tower area.

[0061] The structure above the roof adopts a steel frame-steel plate shear wall structure. Columns are arranged on the axis network. The columns are steel tube concrete columns. The cross-section forms include square steel tubes, narrow rectangular steel tubes, and T-shaped special-shaped steel tubes. Beams are arranged between the columns. The beams and columns together form a steel frame. The beams are H-shaped steel beams. Thin steel plate shear walls are arranged at different positions in the X and Y directions, and steel tube concrete columns are also arranged at both ends of the wall.

[0062] Combined with the design method steps, the embodiment is divided into one and two for specific description.

[0063] Embodiment 1:

[0064] Step S1, firstly, according to the function of the vehicle base in the urban rail transit, the column grid layout of the undercover structure is determined, and the column grid is 9m×18m;

[0065] Step S2, then determine the column grid layout of the structure on the roof according to the function of the development format of the roof in urban rail transit: the roof is a rental residence with residential attributes, and the column grid is 3m×9m;

[0066] Step S3, the under-roof structure is a maintenance workshop of the vehicle depot, with a height of 15m; the upper-roof structure is 8 stories with a floor height of 3m. According to the column grid arrangement and load of the under-roof structure and the upper-roof structure, a three-dimensional finite element model is established in the finite element software;

[0067] Step S4: Combine the building function and the building wall layout, and then set and construct the types and sizes of beams, columns, and shear wall components in the three-dimensional finite element model according to the structural system of the urban rail transit cover, and make each component in the cover structure not protrude from the building wall, and the beams and columns of the cover structure are as follows: Figure 1 The columns on the cover are made of narrow rectangular steel tube concrete columns, and steel plate shear walls are set up so that the components of the cover structure are all inside the building wall to meet the requirements of the use function;

[0068] Step S5, using finite element software to perform mechanical property simulation calculations on the three-dimensional finite element model of the structural system constructed in step S4, to determine whether the current three-dimensional finite element model meets the bearing capacity design requirements; if so, the current three-dimensional finite element model is used to set the structural system of the urban rail transit cover; if not, return to step S4 to reset the size, type and arrangement of each component until the three-dimensional finite element model meets the bearing capacity design requirements.

[0069] In the specific implementation, step S5 is specifically as follows:

[0070] Step S5.1: First, use finite element software to simulate and verify the overall stiffness of the three-dimensional finite element model constructed in step S4:

[0071] Since the stiffness of the lower cover structure and the upper cover structure both meet the stiffness design requirements, proceed to step S5.2;

[0072] Step S5.2, simulate and verify the structural stiffness ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model:

[0073] Because the height of the first floor is 15m, the height is too high, the rigidity of the under-cover structure is small, and the lateral rigidity ratio of the plate-ground structure layer to the adjacent upper-cover structure layer is 0.6, which does not meet the requirement of 0.8; therefore, return to step S4 to increase the cross-section of the under-cover structure columns and beams, and reduce the arrangement of the steel plate wall in the upper-cover structure, so that it can be a structure with fewer walls; repeat steps S4 to S5.2, the rigidity of the under-cover structure and the upper-cover structure both meet the overall rigidity design requirements, and the lateral rigidity ratio of the plate-ground structure layer to the adjacent upper-cover structure layer is 0.82, which meets the set requirements, and enter step S5.3;

[0074] Step S5.3, simulate and verify the shear bearing capacity ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model:

[0075] The shear bearing capacity ratio between the slab-ground structure layer and the adjacent cover structure layer is 1.05, which meets the set requirements; the calculation is completed and the design drawing is formed.

[0076] The drawings can be used later to design and construct the urban rail transit roof at the construction site.

[0077] Embodiment 2:

[0078] Step S1, firstly, according to the function of the vehicle base in the urban rail transit, the column grid layout of the undercover structure is determined, and the column grid is 9m×18m;

[0079] Step S2, then determine the column grid layout of the structure on the roof according to the function of the development format of the roof in urban rail transit: the roof is a rental residence with residential attributes, and the column grid is 3m×9m;

[0080] Step S3: Under the roof is a parking area with a height of 10m; the roof has 16 floors with a floor height of 3m. According to the column grid arrangement and load of the under-roof structure and the roof structure, a three-dimensional finite element model is established in the finite element software;

[0081] Step S4, combining the building function and the building wall layout, then setting and constructing the types and sizes of beams, columns, and shear wall components in the three-dimensional finite element model according to the structural system of the urban rail transit cover, while making sure that each component in the cover structure does not protrude from the building wall, and using narrow rectangular steel tube concrete columns as the cover columns, and setting steel plate shear walls, so that the components of the cover structure are all within the building wall to meet the requirements of the use function;

[0082] Step S5, using finite element software to perform mechanical property simulation calculations on the three-dimensional finite element model of the structural system constructed in step S4, to determine whether the current three-dimensional finite element model meets the bearing capacity design requirements; if so, the current three-dimensional finite element model is used to set the structural system of the urban rail transit cover; if not, return to step S4 to reset the size, type and arrangement of each component until the three-dimensional finite element model meets the bearing capacity design requirements.

[0083] In the specific implementation, step S5 is specifically as follows:

[0084] Step S5.1: First, use finite element software to simulate and verify the overall stiffness of the three-dimensional finite element model constructed in step S4:

[0085] If the under-cover structure meets the requirements, but the upper-cover structure does not meet the requirements, return to step S4, adjust the upper-cover column section to a T-shaped steel tube concrete column, and increase the number of steel plate walls; repeat step S5.1, and if the stiffness of both the under-cover structure and the upper-cover structure meets the stiffness design requirements, proceed to step S5.2;

[0086] Step S5.2, simulate and verify the structural stiffness ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model: the lateral stiffness ratio of the slab-ground structure layer to the adjacent over-cover structure layer is 0.85, which meets the set requirements, and proceed to step S5.3;

[0087] Step S5.3, simulate and verify the shear bearing capacity ratio of the under-cover structure and the upper-cover structure in the three-dimensional finite element model: the shear bearing capacity ratio between the slab ground structure layer and the adjacent upper-cover structure layer is 1.1, which meets the set requirements; after the calculation is completed, a design drawing is formed.

[0088] The drawings can be used later to design and construct the urban rail transit roof at the construction site.

[0089] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A structural system for an urban rail transit roof, characterized in that: The structure comprises an under-cover structure and an over-cover structure, wherein the under-cover structure comprises an outer frame and an inner frame, wherein the inner frame is arranged within the vertical projection range of the tower, and the outer frame is arranged outside the vertical projection range of the tower, and the inner frame and the outer frame are connected; the inner frame is mainly composed of steel-concrete composite columns and steel-concrete composite beams arranged between the steel-concrete composite columns; the outer frame is mainly composed of concrete columns and concrete beams arranged between the concrete columns; the over-cover structure is mainly composed of vertical load-bearing components and steel beams arranged between the vertical load-bearing components; The internal frame in the undercover structure includes steel-concrete composite columns and steel-concrete composite beams, and two adjacent steel-concrete composite columns, between a steel-concrete composite column and a steel-concrete composite beam, and between two adjacent steel-concrete composite beams are all connected by steel-concrete composite beams; the peripheral frame includes concrete columns and concrete beams, and two adjacent concrete columns, between a concrete column and a concrete beam, and between two adjacent concrete beams are all connected by concrete beams; The steel-concrete composite columns of the internal frame and the concrete columns of the external frame, as well as the steel-concrete composite beams of the internal frame and the concrete columns, are all connected by concrete beams; the steel-concrete composite columns and the concrete beams of the external frame, as well as the steel-concrete composite beams and the concrete beams are all connected by concrete beams; The cover structure includes a load-bearing column, a steel beam and a steel plate shear wall; two adjacent load-bearing columns, a load-bearing column and a steel beam, and two adjacent steel beams are connected by steel beams, and the steel plate shear wall is used as a horizontal load-bearing member, and the steel plate shear wall is arranged between two adjacent load-bearing columns, and stiffening ribs are arranged on both sides of the steel plate shear wall; The thickness of a single steel plate of the steel plate shear wall in the cover structure is 4 mm to 8 mm.

2. The structural system of the urban rail transit cover according to claim 1 is characterized by: The steel-concrete composite columns in the internal frame are steel-concrete columns or steel tube concrete columns, and the steel arranged in the steel-concrete columns is H-shaped steel or cross-shaped steel; the steel-concrete composite beams in the internal frame are steel-concrete beams with rectangular cross-sections, and the steel arranged in the steel-concrete beams is H-shaped steel.

3. The structural system of the urban rail transit cover according to claim 1 is characterized by: The load-bearing columns of the cover structure are steel columns or steel tube concrete columns, and the cross-section of the load-bearing columns is one of H-type, rectangular, circular, T-type, L-type and cross-type. The width of the load-bearing columns is smaller than the width of the filling wall in the cover structure.

4. The structural system of the urban rail transit cover according to claim 1 is characterized by: The steel beam of the cover structure is a narrow-flange H-shaped steel, and the flange width of the steel beam is not greater than the width of the load-bearing column.

5. A method for designing a structural system of an urban rail transit roof as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1, firstly, determining the column grid layout of the undercover structure according to the function of the vehicle base in the urban rail transit; Step S2, then determine the column grid layout of the roof structure according to the function of the roof development business format in urban rail transit; Step S3, establishing a three-dimensional finite element model in finite element software according to the column grid arrangement and load of the under-cover structure and the over-cover structure; Step S4, then setting and constructing the types and sizes of beams, columns, and shear wall components in the three-dimensional finite element model according to the structural system of the urban rail transit upper cover, while making sure that each component in the upper cover structure does not protrude from the building wall; Step S5, using finite element software to perform mechanical property simulation calculation on the three-dimensional finite element model of the structural system constructed in step S4, to determine whether the current three-dimensional finite element model meets the bearing capacity design requirements, and if so, to use the current three-dimensional finite element model to set the structural system of the urban rail transit cover; If the bearing capacity design requirements are not met, the process returns to step S4 to reset the size, type and arrangement of each component until the three-dimensional finite element model meets the bearing capacity design requirements.

6. The design method of the structural system of the urban rail transit cover according to claim 5 is characterized by: The step S5 is specifically as follows: Step S5.1: First, use finite element software to simulate and verify the overall stiffness of the three-dimensional finite element model constructed in step S4: If the stiffness of the lower cover structure and the upper cover structure both meet the stiffness design requirements, proceed to step S5.2; Otherwise, return to step S4 to reset the size, type and arrangement of each component until the overall stiffness of the lower cover structure and the upper cover structure meets the design requirements; Step S5.2, simulate and verify the structural stiffness ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model: If the lateral stiffness ratio between the slab-ground structure layer and the upper cover structure layer adjacent to the slab-ground structure layer is not less than 0.8, it indicates that the structural stiffness ratio between the lower cover structure and the upper cover structure meets the design requirements, and the process proceeds to step S5.3; Otherwise, return to step S4 to reset the size, type and arrangement of each component until the structural stiffness ratio between the lower cover structure and the upper cover structure meets the design requirements; The plate ground structure layer is the topmost structure layer in the structure under the cover; Step S5.3, simulate and verify the shear bearing capacity ratio of the under-cover structure and the over-cover structure in the three-dimensional finite element model: If the shear bearing capacity ratio between the slab-ground structure layer and the cover structure layer adjacent to the slab-ground structure layer is not less than 1.0, it indicates that the shear bearing capacity ratio between the cover structure and the cover structure meets the design requirements, and the size, type and arrangement of each component in the urban rail transit cover are set using the current three-dimensional finite element model; Otherwise, return to step S4 to reset the size, type and arrangement of each component until the shear bearing capacity ratio between the under-cover structure and the over-cover structure meets the design requirements.

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