Design method of existing large-span structure additionally-built roof

Abstract

The invention discloses a design method for an additional roof of an existing large-span structure, which comprises the following steps: S1, according to the current situation of the existing large-span structure, determining the total mass M, lateral stiffness k1 and damping ratio of the existing structure and the positions and number n of supporting nodes of the additional roof; the natural vibration frequency of the existing large-span structure is calculated through a formula (1); s2, determining the total mass of the roof; s3, the rigidity of the newly-added roof shock insulation layer is determined; s4, determining design parameters of a single shock insulation support; s5, checking the strength and stability of the components of the roof structure according to the reduced seismic intensity; s6, checking whether the lower supporting structure of the roof meets the standard requirements or not; and S7, building a roof seismic isolation model by taking the roof and the lower structure as a whole, and checking the displacement and acceleration of a seismic isolation layer and the lower structure until the standard requirements are met. By controlling the design process and parameters, the seismic isolation effect on the roof structure can be achieved, seismic oscillation input of the roof structure is isolated, and the seismic force of the roof is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of designing a roof extension for a large-span structure, and in particular to a designing method for extending a roof extension for an existing large-span structure. Background Art

[0002] The large-span roof structure has a beautiful shape and special architectural functions, and is widely used in large public buildings. In the context of urban renewal, there are many renovations that add or replace roofs for existing large-span stadiums, exhibition halls and other structures. After the roof is added to the existing large-span structure, the burden on the original structure is increased. For some structures with a long service life, it is often difficult to meet the seismic requirements and requires a lot of renovation and reinforcement. Through the design method of this application, the size of the small roof structure components can be significantly reduced, the mass damping effect of the new roof on the lower structure can be brought into play, and the amount of reinforcement and renovation work can be significantly reduced.

[0003] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a design method for adding a roof to an existing large-span structure to solve the problems existing in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A design method for adding a roof to an existing large-span structure comprises the following steps:

[0007] S1. According to the existing status of the existing long-span structure, determine the total mass M, lateral stiffness k1, damping ratio ξ1 and the position and number n of the supporting nodes of the newly added roof; calculate the natural frequency of the existing long-span structure by formula (1);

[0008]

[0009] S2. Determine the total mass of the roof: Assume that the total mass of the newly added roof structure is m, and the damping ratio of the isolation layer is ξ2; due to the adoption of the roof isolation scheme, the horizontal force caused by static load or thermal expansion and contraction has been released; determine the reasonable range of the total mass of the newly added roof according to two principles: 1) The vertical load borne by each supporting node is mg / n, and the lower supporting components are not reinforced or simply reinforced to meet the force requirements under the static load of the above formula; 2) By adjusting the ratio of the roof mass to the existing lower structure mass γ=m / M, the mass damping effect of the isolation roof on the lower structure under the action of earthquake is brought into play, and the displacement response of the lower structure under the action of earthquake is reduced;

[0010] S3. Determine the stiffness of the newly added roof isolation layer: Assume that the stiffness of the newly added isolation layer is k2, and use formula (2) to obtain the frequency ω2 of the isolation layer and the structure above it. The frequency ratio of the lower structure to the roof isolation layer is f = ω1 / ω2. According to the principle of controlling the frequency ratio of the lower structure to the isolation layer within [1.0, 1.5], determine the stiffness k2 of the isolation layer;

[0011]

[0012] S4. Determine the design parameters of a single seismic isolation support according to the stiffness of the seismic isolation layer and the number of seismic isolation supports n; determine the damping ratio ξ2 of the seismic isolation layer, the base shear force F of the roof and the shock absorption coefficient through response spectrum or time history analysis. If the shock absorption coefficient is less than 0.4, proceed to the next design process. Otherwise, repeat steps 2, 3, and 4 until the shock absorption coefficient of the roof is less than 0.4.

[0013] S5. Check the strength and stability of the roof structure components according to the reduced earthquake intensity to ensure that the design of the roof structure components meets the requirements of the code;

[0014] S6. Check whether the supporting structure under the roof meets the requirements of the code; if not, reinforce the supporting components;

[0015] S7. Establish a roof isolation model taking the roof and substructure as a whole, and check the displacement and acceleration of the isolation layer and substructure until they meet the requirements of the specification.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects:

[0017] The present invention connects the newly built roof with the lower supporting structure using seismic isolation bearings. By controlling the design process and parameters, on the one hand, the seismic isolation effect of the roof structure can be achieved, the seismic input of the roof structure can be isolated, and the seismic force of the roof can be greatly reduced. The seismic isolation bearings can also release the internal force of the large-span roof structure due to the temperature effect, which not only ensures the safety reserve of the roof itself, but also can significantly reduce the size of the roof components and reduce the burden on the lower structure. On the other hand, the present design method gives full play to the mass damping effect of the seismic isolation roof on the lower structure. By adjusting the parameters through the present design method, the newly built roof can become a mass damper of the lower structure, which can reduce the structural response of the lower structure under the action of earthquakes. In summary, the present design method can reduce the impact of the newly built roof on the overall structure from two aspects, and reduce the amount of renovation and reinforcement engineering caused by the newly built roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The overall structural diagram of adding a roof to the large-span structure of the present invention.

[0020] Figure 2 This is a diagram showing the reduction rule of the displacement of the lower structure of the present invention as the mass ratio of the roof to the lower structure changes.

[0021] Figure 3 Graph showing the relationship between the displacement of the lower structure and the frequency ratio of the present invention. DETAILED DESCRIPTION

[0022] 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.

[0023] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0024] Combination Figure 1-3 As shown, the present invention proposes a design method for adding a roof to an existing large-span structure, comprising the following steps:

[0025] 1. As there is no condition for large-scale reinforcement and reconstruction of the existing stadium, considering the practical operation and economic benefits, in order to minimize the impact of the new roof on the lower supporting structure, the roof isolation scheme is used to connect the new roof with the existing structure below. Figure 1 As shown. According to the status of the existing long-span structure, the total mass M, lateral stiffness k1, damping ratio ξ1 of the existing structure and the position and number n of the supporting nodes of the newly added roof are determined. The natural frequency of the existing long-span structure is calculated by the following formula.

[0026]

[0027] 2. Determine the total mass of the roof. Assume that the total mass of the newly added roof structure is m, and the damping ratio of the isolation layer is ξ2. Due to the adoption of the roof isolation scheme, the horizontal force caused by static load or thermal expansion and contraction has been released. The reasonable range of the total mass of the newly added roof is determined according to two principles. (1) The vertical load borne by each supporting node is mg / n. The lower supporting components can meet the force requirements under the static load in the above formula without reinforcement or after simple reinforcement. (2) By adjusting the ratio of the roof mass to the existing lower structure mass γ=m / M, the mass damping effect of the isolation roof on the lower structure under earthquake action is exerted, thereby reducing the displacement response of the lower structure under earthquake action. The law of displacement reduction of the lower structure is as follows Figure 2 As shown in Figure 1, the mass of the newly added roof must not only meet the vertical load requirements, but also fully reduce the lower structure response under earthquake action. Based on the above two principles, the mass m of the newly added roof is determined.

[0028] For example, the ultimate bearing capacity of each supporting structure can be verified by the code, and the maximum force fmax of each roof support point can be inferred, so as to obtain the maximum roof mass m0=fmax×n / g that the existing large-span structure can support without reinforcement. (1) If the ratio of m0 to the mass of the lower structure γ is between [0.05,0.2], it can be considered that the newly added roof mass is within a reasonable range, and the roof mass is equal to m0. (2) If the ratio of m0 to the mass of the lower structure γ is less than 0.05, γ is taken as 0.05. At this time, the existing supporting structure cannot bear the newly added roof mass and needs to be reinforced. (3) If the ratio of m0 to the mass of the lower structure γ is greater than 0.2, γ can be taken as 0.2. At this time, the lower supporting structure will have a certain safety reserve.

[0029] 3. Determine the stiffness of the newly added roof isolation layer. Assuming that the stiffness of the newly added isolation layer is k2, the frequency ω2 of the isolation layer and the structure above is obtained by the following formula, and the frequency ratio of the lower structure and the roof isolation layer is recorded as f=ω1 / ω2. Since M, m and ω1 have been determined in the above two steps, the stiffness k2 of the isolation layer is determined by controlling the frequency ratio of the lower structure and the isolation layer within [1.0,1.5]. Figure 3As shown in Figure 1, when the frequency ratio is between 1.0 and 1.5, the displacement of the lower structure is the smallest. The stiffness parameters determined in this way can ensure that the roof can fully exert its damping effect on the existing structure mass under earthquake action.

[0030]

[0031] 4. According to the stiffness of the seismic isolation layer and the number of seismic isolation supports n, determine the design parameters of a single seismic isolation support. Determine the damping ratio ξ2 of the seismic isolation layer, the base shear force F of the roof and the shock absorption coefficient through response spectrum or time history analysis. If the shock absorption coefficient is less than 0.4, proceed to the next design process. Otherwise, repeat steps 2, 3, and 4 until the shock absorption coefficient of the roof is less than 0.4.

[0032] 5. Check the strength and stability of the roof structure components according to the reduction of earthquake intensity by one degree, and ensure that the design of the roof structure components meets the requirements of the specification. After the design is completed, the actual mass of the roof should be close to the total mass m determined in the second step, with an error within 5%.

[0033] 6. Check whether the lower supporting structure of the roof meets the requirements of the specification. If not, reinforce the supporting components.

[0034] 7. Establish a roof isolation model taking the roof and substructure as a whole, and check the displacement and acceleration of the isolation layer and substructure until they meet the requirements of the specification.

[0035] Figure 1 In the equation, u1 is the floor displacement of the substructure, and u2 is the inter-story displacement of the roof relative to the substructure.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for adding a roof to an existing large-span structure, characterized in that: The steps include: S1. According to the existing large-span structure status, determine the total mass M, lateral stiffness k1, and damping ratio of the existing structure. and the position and number n of the supporting nodes of the newly added roof; the natural frequency of the existing long-span structure is calculated by formula (1); (1)； S2. Determine the total mass of the roof: Assume that the total mass of the newly added roof structure is m, and the damping ratio of the isolation layer is ; Due to the adoption of the roof isolation scheme, the horizontal force caused by static load or thermal expansion and contraction has been released; the reasonable range of the total mass of the new roof is determined according to two principles: 1) the vertical load borne by each supporting node is mg / n, and the lower supporting components are not reinforced or simply reinforced to meet the force requirements under the above static load; 2) by adjusting the ratio of the roof mass to the existing lower structure mass , Controlled between [0.05, 0.2], the mass damping effect of the seismic isolation roof on the lower structure under earthquake action is brought into play, reducing the displacement response of the lower structure under earthquake action; S3. Determine the stiffness of the newly added roof isolation layer: Assuming the stiffness of the newly added isolation layer is k2, the frequency of the isolation layer and the structure above it is obtained by formula (2): , the frequency ratio of the lower structure and the roof isolation layer is ; According to the principle of controlling the frequency ratio between the substructure and the seismic isolation layer within [1.0,1.5], determine the seismic isolation layer stiffness k2; (2)； S4. Determine the design parameters of a single isolation support according to the stiffness of the isolation layer and the number of isolation supports n; determine the damping ratio of the isolation layer through response spectrum or time history analysis , the base shear force F and horizontal damping coefficient of the roof. If the horizontal damping coefficient is less than 0.4, proceed to the next step of the design process. Otherwise, repeat steps 2, 3, and 4 until the horizontal damping coefficient of the roof is less than 0.4; S5. According to the requirements of reducing the earthquake intensity by one degree, check the strength and stability of the roof structure components according to the specifications to ensure that the design of the roof structure components meets the requirements of the specifications; S6. Check whether the ultimate bearing capacity and deformation of the supporting structure under the roof meet the requirements of the specifications according to the specifications; if not, reinforce the supporting components; S7. Establish a roof isolation model by taking the roof and substructure as a whole, and control the displacement of the isolation layer and substructure, the inter-layer displacement angle, and the acceleration indexes not to exceed the specification limits; if the requirements are not met, reinforcement measures can be taken until the indicators meet the specification requirements.

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