CN113468652B

CN113468652B - Design method of large-curvature cable membrane structure

Info

Publication number: CN113468652B
Application number: CN202111027371.5A
Authority: CN
Inventors: 石冬; 钟世原; 沈龙飞; 曹晓凯; 张磊; 李铁东; 万文涛; 魏文龙
Original assignee: China Railway Construction Engineering Group Co Ltd
Current assignee: China Railway Construction Engineering Group Co Ltd
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2022-02-11
Anticipated expiration: 2041-09-02
Also published as: CN113468652A

Abstract

The invention protects a design method of a large-curvature cable membrane structure, aiming at the technical problems that the existing cable membrane structure is easy to deform greatly to change the shape and size or is loose, and the analysis design theory of the cable membrane structure is not completely mature at home and abroad; the design method of the invention comprises the following steps: (1) performing performance analysis on a membrane material to be used for the large-curvature cable membrane structure; (2) performing shape finding analysis on the large-curvature cable membrane structure by adopting ANSYS software; (3) selecting a film material with a proper thickness; (4) optimizing a reinforcing cable net in the large-curvature cable membrane structure; (5) carrying out technical verification and hardware optimization on the large-curvature cable membrane structure; (6) and designing the appropriate light transmittance of the film material. The design method optimizes the steel cable, the membrane material, the hardware and the steel cable-membrane support steel structure cooperative stress system, improves the integral stress stability of the structure and the applicability of the component on the premise of giving full play to the material performance, and enables the architectural shape art to be expressed perfectly.

Description

Design method of large-curvature cable membrane structure

Technical Field

The invention relates to the technical field of cable membrane structure design of constructional engineering, in particular to a design method of a large-curvature cable membrane structure.

Background

With the continuous development of society, the demands of people on public activity spaces such as large-scale exhibition halls, sports stadiums, airports, railway stations and the like are increasing day by day; meanwhile, as the aesthetic level of people is continuously improved, the requirements on the beauty, lightness and the like of buildings are also continuously increased; the cable membrane structure is more and more popular with the public due to the rich color, the light structural form and the beautiful shape. These phenomena greatly promote the continuous innovation of the cable membrane structure. Not only is the innovation in the aspects of safety and economy, but also the innovation in the aspect of modeling, and the aesthetic requirements of people on continuous updating are met.

The cable membrane structure is different from a conventional building structure, the used membrane material is an elastic-plastic material, two yield platforms can appear in the material during a tensile test, the maximum tensile strength is only about 1/10 of that of steel, the larger the tensile deformation is under the action of tensile force, the larger the creep is, and the mechanical property is unique; and the membrane material is sensitive to temperature changes.

The cable membrane structure has obvious advantages in flame retardant property and light transmission, has good durability, can reduce structural load, can reduce material usage amount, saves engineering investment, and is widely applied in recent years.

However, the cable membrane structure is susceptible to temperature performance, and the large-area membrane structure is easily subjected to stress concentration and plastic deformation at the edge of the structure under the action of wind and snow loads or is subjected to large deformation due to temperature change to change the shape size or be loosened. The analysis design theory of the cable membrane structure at home and abroad is not completely mature, so that a suitable design method of the large-curvature cable membrane structure is explored, special design and processing are carried out according to special building shapes, targeted optimization and improvement are carried out in actual construction, and the method is also a requirement for promoting popularization and application of the large-span and large-area cable membrane structure.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a design method of a large-curvature cable membrane structure. The design method optimizes the steel cable, the membrane material, the hardware and the steel cable-membrane support steel structure cooperative stress system, improves the integral stress stability of the structure and the applicability of the component on the premise of giving full play to the material performance, and enables the architectural shape art to be expressed perfectly.

In order to achieve the purpose, the invention provides a design method of a large-curvature cable membrane structure, which comprises the following steps:

(1) performing performance analysis on the membrane material to be used in the large-curvature cable membrane structure to determine the membrane material to be selected; the performance analysis comprises the tensile performance analysis and creep performance analysis of the membrane material; the film tensile property analysis comprises performing a uniaxial tensile test; the creep performance analysis of the membrane material comprises a normal-temperature creep test, wherein the temperature is 30-35 ℃; neglecting the instantaneous strain of a material only considers the creep strain of the material, which is the difference between the strain of the material at any moment of the test and the initial strain, namely:

wherein, ɛ_crFor creep strain, L (t) and ɛ (t) are the displacement and strain of the material at time t; l (t)₀) And ɛ (t)₀) Displacement and strain of the material at the initial moment; l is₀The length between the clamps is 80-120 mm;

(2) performing shape finding analysis on the large-curvature cable membrane structure by adopting ANSYS software, and selecting a SHELL41 unit to simulate a membrane material in the cable membrane structure;

(3) the method comprises the steps of analyzing the stress of membrane materials with different thicknesses under the action of wind load, and selecting the membrane material with the appropriate thickness;

(4) optimizing a reinforcing cable net in the large-curvature cable membrane structure; the method specifically comprises the steps of determining a structure system, selecting and optimizing a cable net arrangement scheme and selecting the diameter of a steel cable;

(5) carrying out technical verification and hardware optimization on the large-curvature cable membrane structure; the method specifically comprises the steps of optimizing a cable bag, optimizing a cable clamp, optimizing an aluminum clamp, optimizing a cable membrane support steel structure and optimizing a tensioning adaptor; technical verification and hardware optimization are mainly realized by manufacturing a 1:1 solid model on site; the rope bag is optimized in such a way that the rope bag is arranged at the position, corresponding to the longitudinal steel cable, on the membrane material, the imprints of the rope bag and the steel cable are weakened, and the shape of the membrane surface is closer to the expected shape; the cable clamp is optimized to use a universal cable clamp, so that the crossed longitudinal and transverse steel cables can rotate independently, and the angle of the universal cable clamp can be freely adjusted according to the stress direction and the linear type of the steel cables in the tensioning process of the steel cables; adding a flexible silica gel pad at the bottom of the universal cable clamp; the aluminum clamp is optimized to be bent according to the edge line type of the membrane material, so that the line type of the aluminum clamp is matched with the edge line type of the membrane material, and a curve edge effect is presented; the cable membrane support steel structure is optimized in such a way that a plurality of mounting supports are processed into an integral module, the module mounting is used for replacing a large number of spare part mounting, the module positioning is used for replacing a plurality of spare part positioning, and meanwhile, the welding seam connection is designed to be bolt connection; the tensioning adaptor is optimized by introducing a universal adaptor at the tensioning end of the steel cable, the universal adaptor is connected with the steel structure of the cable membrane support and is perpendicular to the steel plate surface at the bolt hole of the steel structure of the cable membrane support, and the tensioning bolt at the tensioning end of the steel cable is connected with the universal adaptor;

(6) designing appropriate light transmittance of the film material, wherein the light transmittance range is 75% to 90%;

(7) processing the selected membrane material, including modeling, blanking, cutting and heat sealing; the film material adopts a film material which takes ethylene-tetrafluoroethylene copolymer as a main material and comprises the following components in parts by weight: 60-75 parts of ethylene-tetrafluoroethylene, 25-30 parts of silicon dioxide, 10-12 parts of titanium dioxide, 3-5 parts of an auxiliary crosslinking agent, 5-6 parts of a coupling agent, 3-4 parts of zinc distearate, 5-8 parts of tert-butyl hydroperoxide, 5-10 parts of dibutyl phthalate and 2-4 parts of N, N-dimethylformamide; the preparation method comprises the steps of weighing the components in parts by weight, adding the ethylene-tetrafluoroethylene and the tertiary butyl hydroperoxide into an internal mixer at the temperature of 70-80 ℃, uniformly mixing, and continuously stirring for reacting for 2-3 hours at the temperature of 80-90 ℃; then adding the rest components into the mixture, and uniformly stirring the mixture for 1 to 1.5 hours; finally, extruding the mixture by a screw extruder at the temperature range of 280-300 ℃ to obtain a film material mainly comprising the ethylene-tetrafluoroethylene copolymer;

before modeling and blanking, carrying out high-precision retest on the mounting support of the membrane structure and mounting bolt hole positions of the support steel structure, establishing a three-dimensional model according to a retest result, and carrying out modeling and drawing a processing diagram of the hyperbolic membrane structure on the basis of the model; adopting a three-dimensional scanner to measure the bolt hole positions of the cable membrane support steel structure, generating a structural solid model containing the bolt hole positions by the constructed steel structure through three-dimensional scanning, and using the spatial positions of the bolt hole positions as the edge limiting conditions of the membrane structure to carry out the specific design of the membrane surface; the specific steps of membrane surface design are as follows:

1) comparing the retest result with the design data, and then spreading the film, namely spreading the space curved surface into a plane figure;

2) determining the lengths of the transverse cable and the radial cable and the installation point position of the universal cable clamp;

3) and (5) examining the film surface, and drawing a picture for blanking after confirming no errors. The lapping size of the film surface heat seal is required to be considered during blanking;

when the cutting is carried out in a hot-time mode, the membrane material is cut according to a blanking drawing, a full-automatic membrane material cutting machine is adopted for carrying out three-dimensional cutting, and the cutting is finished at one time according to a cutting curve after the membrane is spread in space; debugging equipment before cutting the membrane to enable the equipment to be in an optimal state, inspecting the size of the membrane by quality inspection personnel after cutting is finished, and enabling the qualified membrane to enter a heat sealing process; before the film is subjected to heat sealing, dust on a heat sealing platform is wiped clean, and a heat sealing operator confirms the film number, the fastener number and the corner number according to the processing sequence and prepares a heat sealing cutting sheet; confirming the overlapping direction and the welding width of the membrane material, wherein the deviation between the heat sealing width and a theoretical design value is not more than +/-1 mm; the heat seal platform is sequentially provided with a membrane material traction mechanism, a hot pressing platform and a stretching mechanism; the film material drawing mechanism draws the cut film material, and the hot pressing table is used for hot pressing the film material drawn by the film material drawing mechanism; the hot pressing platform comprises a flat stretching roller and a hot pressing platform positioned above the flat stretching roller; the hot pressing platform can move downwards to the flat stretching roller; the stretching mechanism is positioned behind the hot pressing table and is used for adjusting the length of the film material after passing through the hot pressing table in cooperation with the hot pressing table; the hot pressing platform and the stretching mechanism are mutually matched through a transmission mechanism.

Preferably, in the step (2), a tension option is selected in the form-finding process to neglect the bending rigidity of the form-finding process; selecting a triangular unit during element division, selecting 650MPa as the elastic modulus of a membrane material, and selecting 0.42 as the Poisson ratio of the membrane material; simulating a guy cable by using a LINK10 unit, wherein the elastic modulus is 1.60 multiplied by 105MPa, the Poisson ratio is 0.3, and prestressing force is applied to the guy cable unit by using a method for changing initial strain; and cooperatively searching the shape of the cable membrane by adopting a small elastic modulus method.

In any of the above solutions, it is preferable that in step (2), the vertical cable arrangement is first determined by calculation before the shape finding analysis, and then the shape finding analysis is performed on 3-5 cables arranged in the transverse direction.

In any of the above schemes, preferably, in the step (3), the maximum stress is strictly controlled during the film structure thickness design, and the maximum stress does not exceed 9 MPa; simulating wind load to apply acting force to the membrane surface in a wind pressure or wind suction mode, wherein the stress is in inverse proportion to the unit length section area of the membrane material, namely the thickness of the membrane material; selecting a film material with the thickness of 280-300 μm.

In any of the above aspects, preferably, in the step (4), the structural system is determined to be a single-layer film reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are mainly stressed steel cables, 7-10 vertical steel cables are arranged on a middle diaphragm, and 3-6 vertical steel cables are arranged on an edge diaphragm; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system by ANSYS software, wherein the steel cable with the diameter of 12-15mm is adopted.

The invention has the beneficial effects that:

1. the design method optimizes the steel cable, the membrane material, the hardware and the steel cable-membrane support steel structure cooperative stress system, improves the integral stress stability of the structure and the applicability of the component on the premise of giving full play to the material performance, and enables the architectural shape art to be expressed perfectly.

2. The invention ensures that the film surface stress and the cable force of the shaped cable film structure are more uniform after the shaping, thereby meeting the engineering design requirements; the cable membrane structure can be ensured to maintain a normal form under the initial tension, wind load and temperature of the membrane surface, and the structural creep can be controlled to an acceptable range.

3. The design method of the invention ensures that the membrane material is stressed reasonably, the stress of the steel cable is lower and the performance of the steel cable can be fully exerted; the cable net linear curve is smoothly transited, and the membrane surface curved surface is smoothly transited; the construction speed can be accelerated, and the construction quality is improved; the installation process is simplified, and the construction efficiency is improved.

Detailed Description

The technical solutions of the present application will be described in detail below with reference to specific embodiments of the present application, but the following examples are only for the understanding of the present invention, and the examples and features of the examples in the present application can be combined with each other, and the present application can be implemented in various different ways as defined and covered by the claims.

Example 1

A design method of a large-curvature cable membrane structure comprises the following steps:

(1) performing performance analysis on the membrane material to be used in the large-curvature cable membrane structure to determine the membrane material to be selected; the performance analysis comprises the tensile performance analysis and creep performance analysis of the membrane material;

(3) selecting a film material with a proper thickness by analyzing the stress of the film materials with different thicknesses under the action of wind load;

(5) carrying out technical verification and hardware optimization on the large-curvature cable membrane structure; the method specifically comprises the steps of optimizing a cable bag, optimizing a cable clamp, optimizing an aluminum clamp, optimizing a cable membrane support steel structure and optimizing a tensioning adaptor;

(6) the film material is designed to have proper light transmittance, and the light transmittance range is 75%.

In the step (1), the film tensile property analysis comprises performing a uniaxial tensile test; the creep performance analysis of the membrane material comprises a normal-temperature creep test, wherein the temperature is 35 ℃; in order to intuitively study the creep performance of the membrane material, only the creep strain of the material is considered regardless of the instantaneous strain of the material, and the creep strain is a difference value between the strain of the material and the initial strain at any time of the test, namely:

wherein, ɛ_crFor creep strain, L (t) and ɛ (t) are the displacement and strain of the material at time t; l (t)₀) And ɛ (t)₀) Displacement and strain of the material at the initial moment; l is₀The length between the clamps was 80 mm.

In the step (2), because the membrane material cannot resist bending deformation, the tensile option is selected to neglect the bending rigidity in the shape finding process; in order to prevent the membrane unit from warping in the shape finding process, a triangular unit is selected during element division, 650MPa is selected as the elastic modulus of the membrane material, and 0.42 is selected as the Poisson ratio of the membrane material; simulating a guy cable by using a LINK10 unit, wherein the elastic modulus is 1.60 multiplied by 105MPa, the Poisson ratio is 0.3, and prestressing force is applied to the guy cable unit by using a method for changing initial strain; the cable membrane is subjected to cooperative shape finding by adopting a small elastic modulus method, and the membrane surface stress and the cable force are uniform after the cable membrane structure which is found by adopting the method is formed, so that the engineering design requirement is met.

In the step (2), before the shape finding analysis, the arrangement of the vertical ropes is firstly calculated and determined, and then the shape finding analysis is carried out on 3-5 steel ropes which are transversely arranged.

In the step (3), the maximum stress is strictly controlled during the design of the thickness of the film structure, and the maximum stress does not exceed 9 MPa; simulating wind load to apply acting force to the membrane surface in a wind pressure or wind suction mode, wherein the stress is in inverse proportion to the unit length section area of the membrane material, namely the thickness of the membrane material; through the experimental analysis and comprehensive consideration of economy, the membrane material with the thickness of 300 mu m is selected, so that the cable membrane structure can be ensured to maintain a normal form under the initial tension, wind load and temperature of the membrane surface, and the structural creep can be controlled to an acceptable range.

In the step (4), in order to ensure reasonable stress of the membrane material, a structural system is determined to be a single-layer membrane reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are main stress steel cables, 10 vertical steel cables are arranged on a middle diaphragm, and 3 vertical steel cables are arranged on an edge diaphragm; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system through ANSYS software, and the steel cable with the diameter of 15mm is adopted, so that the stress of the steel cable is low, and the performance of the steel cable can be fully exerted.

In the step (5), technical verification and hardware optimization are mainly realized by manufacturing a 1:1 solid model on site; the rope bag is optimized in such a way that the rope bag is arranged at the position, corresponding to the longitudinal steel rope, on the membrane material, so that the shadow of the vertical steel rope is narrowed, the imprints of the rope bag and the steel rope are weakened, and the shape of the membrane surface is closer to the expected shape; the cable clamp is optimized to be a universal cable clamp, under the condition of maintaining the appearance of a cylinder of the universal cable clamp, the crossed longitudinal and transverse steel cables can independently rotate, and the angle of the universal cable clamp can be freely adjusted according to the stress direction and the linear shape of the steel cables in the process of tensioning the steel cables; the universal cable clamp is used, so that the cable net linear curve transition is smooth, and the membrane surface curved surface is smooth and smooth. In order to prevent the metal universal cable clamp and the membrane surface from rubbing to damage the membrane surface under wind load, a flexible silica gel pad is added at the bottom of the universal cable clamp to prevent the metal universal cable clamp from directly contacting with the membrane surface; the aluminum clamp is optimized to be bent according to the edge line type of the membrane material, so that the line type of the aluminum clamp is matched with the edge line type of the membrane material, and a curve edge effect is presented; the membrane structure is attached to a main steel structure, a membrane structure stress system is connected with the main steel structure through a cable membrane support steel structure, and the cable membrane support steel structure is equivalent to an installation support of the membrane structure; in order to accelerate the construction speed and improve the construction quality, the cable membrane support steel structure is optimized to process a plurality of mounting supports into an integral module, the module mounting replaces the mounting of a large number of spare parts, the module positioning replaces the positioning of a plurality of spare parts, and meanwhile, the welding seam connection is designed to be bolt connection, so that the mounting process is simplified, and the construction efficiency is improved; the tensioning adaptor is optimized by introducing a universal adapter at a tensioning end of the steel cable, the universal adapter is connected with the cable membrane support steel structure and is perpendicular to a steel plate surface at a bolt hole of the cable membrane support steel structure, a tensioning bolt at the tensioning end of the steel cable is connected with the universal adapter, so that the flexible adjustment of the angle is realized, and the tensioning cable head of the steel cable is always consistent with the stress direction of the steel cable.

Further comprises a step (7) of processing the selected membrane material, including modeling blanking and cutting and heat sealing.

Example 2

(6) and designing the appropriate light transmittance of the film material, wherein the light transmittance range is 90%.

In the step (1), the film tensile property analysis comprises performing a uniaxial tensile test; the creep performance analysis of the membrane material comprises a normal-temperature creep test, wherein the temperature is 30 ℃; in order to intuitively study the creep performance of the membrane material, only the creep strain of the material is considered regardless of the instantaneous strain of the material, and the creep strain is a difference value between the strain of the material and the initial strain at any time of the test, namely:

wherein, ɛ_crFor creep strain, L (t) and ɛ (t) are the displacement and strain of the material at time t; l (t)₀) And ɛ (t)₀) Displacement and strain of the material at the initial moment; l is₀The length between the clamps is 120 mm.

In the step (3), the maximum stress is strictly controlled during the design of the thickness of the film structure, and the maximum stress does not exceed 9 MPa; simulating wind load to apply acting force to the membrane surface in a wind pressure or wind suction mode, wherein the stress is in inverse proportion to the unit length section area of the membrane material, namely the thickness of the membrane material; through the experimental analysis and comprehensive consideration of economy, the membrane material with the thickness of 280 microns is selected, so that the cable membrane structure can be ensured to maintain a normal form under the initial tension, wind load and temperature of the membrane surface, and the structural creep can be controlled to an acceptable range.

In the step (4), in order to ensure reasonable stress of the membrane material, a structural system is determined to be a single-layer membrane reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are main stress steel cables, a middle diaphragm is provided with 7 vertical steel cables, and edge diaphragms are provided with 6 vertical steel cables; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system through ANSYS software, and the steel cable with the diameter of 15mm is adopted, so that the stress of the steel cable is low, and the performance of the steel cable can be fully exerted.

In the step (5), technical verification and hardware optimization are mainly realized by manufacturing a 1:1 solid model on site; the rope bag is optimized in such a way that the rope bag is arranged at the position, corresponding to the longitudinal steel rope, on the membrane material, so that the shadow of the vertical steel rope is narrowed, the imprints of the rope bag and the steel rope are weakened, and the shape of the membrane surface is closer to the expected shape; the cable clamp is optimized to be a universal cable clamp, under the condition of maintaining the appearance of a cylinder of the universal cable clamp, the crossed longitudinal and transverse steel cables can independently rotate, and the angle of the universal cable clamp can be freely adjusted according to the stress direction and the linear shape of the steel cables in the process of tensioning the steel cables; the universal cable clamp is used, so that the cable net linear curve transition is smooth, and the membrane surface curved surface is smooth and smooth. In order to prevent the metal universal cable clamp and the membrane surface from rubbing to damage the membrane surface under wind load, a flexible silica gel pad is added at the bottom of the universal cable clamp to prevent the metal universal cable clamp from directly contacting with the membrane surface; the aluminum clamp is optimized to be bent according to the edge line type of the membrane material, so that the line type of the aluminum clamp is matched with the edge line type of the membrane material, and a curve edge effect is presented; the membrane structure is attached to a main steel structure, a membrane structure stress system is connected with the main steel structure through a cable membrane support steel structure, and the cable membrane support steel structure is equivalent to an installation support of the membrane structure; in order to accelerate the construction speed and improve the construction quality, the cable membrane support steel structure is optimized to process a plurality of mounting supports into an integral module, the module mounting replaces the mounting of a large number of spare parts, the module positioning replaces the positioning of a plurality of spare parts, and meanwhile, the welding seam connection is designed to be bolt connection, so that the mounting process is simplified, and the construction efficiency is improved; the tensioning adaptor is optimized by introducing a universal adapter at a tensioning end of the steel cable, the adapter is connected with the cable membrane support steel structure and is perpendicular to a steel plate surface at a bolt hole of the cable membrane support steel structure, a tensioning bolt at the tensioning end of the steel cable is connected with the universal adapter, so that the flexible adjustment of the angle is realized, and the tensioning cable head of the steel cable is always kept consistent with the stress direction of the steel cable.

Example 3

wherein, ɛ_crFor creep strain, L (t) and ɛ (t) are the displacement and strain of the material at time t; l (t)₀) And ɛ (t)₀) Displacement and strain of the material at the initial moment; l is₀The length between the clamps was 100 mm.

In the step (2), the vertical cable arrangement is firstly calculated and determined before the shape finding analysis, and then the shape finding analysis is carried out on 5 steel cables which are transversely arranged.

In the step (4), in order to ensure reasonable stress of the membrane material, a structural system is determined to be a single-layer membrane reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are main stress steel cables, 9 vertical steel cables are arranged on a middle diaphragm, and 5 vertical steel cables are arranged on an edge diaphragm; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system through ANSYS software, and the steel cable with the diameter of 12mm is adopted, so that the stress of the steel cable is low, and the performance of the steel cable can be fully exerted.

Example 4

(6) and designing the appropriate light transmittance of the film material, wherein the light transmittance ranges from 75% to 90%.

In the step (1), the film tensile property analysis comprises performing a uniaxial tensile test; the creep performance analysis of the membrane material comprises a normal-temperature creep test, wherein the temperature is 30-35 ℃; in order to intuitively study the creep performance of the membrane material, only the creep strain of the material is considered regardless of the instantaneous strain of the material, and the creep strain is a difference value between the strain of the material and the initial strain at any time of the test, namely:

wherein, ɛ_crFor creep strain, L (t) and ɛ (t) are the displacement and strain of the material at time t; l (t)₀) And ɛ (t)₀) Displacement and strain of the material at the initial moment; l is₀The length between the clamps is 80-120 mm.

In the step (3), the maximum stress is strictly controlled during the design of the thickness of the film structure, and the maximum stress does not exceed 9 MPa; simulating wind load to apply acting force to the membrane surface in a wind pressure or wind suction mode, wherein the stress is in inverse proportion to the unit length section area of the membrane material, namely the thickness of the membrane material; through the experimental analysis and comprehensive consideration of economy, the membrane material with the thickness of 280-300 mu m is selected, so that the cable membrane structure can be ensured to maintain a normal form under the initial tension, wind load and temperature of the membrane surface, and the structural creep can be controlled to an acceptable range.

In the step (4), in order to ensure reasonable stress of the membrane material, a structural system is determined to be a single-layer membrane reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are mainly stressed steel cables, 7-10 vertical steel cables are arranged on a middle diaphragm, and 3-6 vertical steel cables are arranged on an edge diaphragm; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system through ANSYS software, and the steel cable with the diameter of 12-15mm is adopted, so that the steel cable has lower stress and can fully exert the performance of the steel cable.

In order to further improve the technical effect of the invention, in the embodiment, during modeling and blanking, the processing of the large-curvature cable membrane structure has extremely high precision requirement, the membrane surface morphology can be changed or wrinkles can appear due to slight deviation of the size, in order to improve the processing precision, high-precision retesting needs to be carried out on the membrane structure mounting support and the mounting bolt hole site of the support steel structure before modeling and blanking, a three-dimensional model is built according to the retesting result, and modeling and drawing of the hyperbolic membrane structure are carried out on the basis of the model. The bolt hole positions are installed on the cable membrane support steel structure by adopting the retest of the three-dimensional scanner, and the three-dimensional scanner has the advantages of high precision, high automation degree, capability of being used together with model design software and the like. And generating a structural solid model containing mounting bolt hole positions by three-dimensional scanning of the constructed steel structure, and carrying out specific design on the membrane surface by taking the spatial positions of the bolt hole positions as the limit conditions of the edge of the membrane structure.

The specific steps of membrane surface design are as follows

1) And (4) comparing the retest result with the design data, and then spreading the film, namely spreading the space curved surface into a plane figure.

2) And determining the lengths of the transverse cable and the radial cable and the installation point position of the universal cable clamp.

3) And (5) examining the film surface, and drawing a picture for blanking after confirming no errors. The lapping size of the film surface heat seal needs to be considered during blanking.

When the cutting is carried out, the film material is cut according to the blanking drawing, the full-automatic film material cutting machine is adopted for carrying out three-dimensional cutting, and the cutting is completed at one time according to the cutting curve after the film is spread in space. Debugging equipment before cutting the membrane material to enable the equipment to be in the optimal state, inspecting the size of the membrane material by quality inspection personnel after cutting, and enabling the qualified membrane material to enter a heat sealing process. Before the film material is heat-sealed, dust on the heat-sealing platform is wiped clean, otherwise the heat-sealing quality is affected. The heat seal operator confirms the film material number, the fastener number and the corner number according to the processing sequence, and prepares the heat seal cutting sheet. The overlapping direction and the welding width of the film materials are confirmed, and the deviation between the heat sealing width and the theoretical design value is not more than +/-1 mm.

The heat seal platform is sequentially provided with a membrane material traction mechanism, a hot pressing platform and a stretching mechanism. The film material drawing mechanism draws the cut film material, and the hot pressing table is used for hot pressing the film material drawn by the film material drawing mechanism; the hot pressing platform comprises a flat stretching roller and a hot pressing platform positioned above the flat stretching roller; the hot pressing platform can move downwards to the flat stretching roller; the stretching mechanism is positioned behind the hot pressing table and is used for adjusting the length of the film material after passing through the hot pressing table in cooperation with the hot pressing table; the hot pressing platform and the stretching mechanism are mutually matched through a transmission mechanism. The tiled stretching roller has viscosity, can appropriately stick the film material during operation, enables the film material to keep a tiled stretching state during forward conveying, and ensures the material state during hot pressing.

The integrated heat seal platform is adopted, so that the manufacturing cost is saved, the production flow property and the working efficiency are improved, and the quality of the membrane material is improved.

Example 5

In order to further improve the technical effect of the present invention, in this embodiment, the film material mainly comprises an ethylene-tetrafluoroethylene copolymer, and comprises the following components in parts by weight: 60-75 parts of ethylene-tetrafluoroethylene, 25-30 parts of silicon dioxide, 10-12 parts of titanium dioxide, 3-5 parts of an auxiliary crosslinking agent, 5-6 parts of a coupling agent, 3-4 parts of zinc distearate, 5-8 parts of tert-butyl hydroperoxide, 5-10 parts of dibutyl phthalate and 2-4 parts of N, N-dimethylformamide.

The preparation method comprises the steps of weighing the components in parts by weight, adding the ethylene-tetrafluoroethylene and the tertiary butyl hydroperoxide into an internal mixer at the temperature of 70-80 ℃, uniformly mixing, and continuously stirring for reacting for 2-3 hours at the temperature of 80-90 ℃; then adding the rest components into the mixture, and uniformly stirring the mixture for 1 to 1.5 hours; finally, the mixture is extruded by a screw extruder at the temperature range of 280-300 ℃ to obtain the membrane material mainly comprising the ethylene-tetrafluoroethylene copolymer.

The film material of the invention has higher strength, high wear resistance, high thermal stability and improved processability. In addition, the film material has better material tensile property, and the preparation method has simple process, easily controlled conditions and strong applicability.

In addition, in order to ensure the technical effect of the invention, the technical schemes of the above embodiments can be reasonably combined.

According to the embodiment, the design method optimizes the steel cable, the membrane material, the hardware and the steel cable-membrane support steel structure cooperative stress system, improves the integral stress stability of the structure and the applicability of the member on the premise of giving full play to the material performance, and enables the architectural shape art to be expressed perfectly.

The invention ensures that the film surface stress and the cable force of the shaped cable film structure are more uniform after the shaping, thereby meeting the engineering design requirements; the cable membrane structure can be ensured to maintain a normal form under the initial tension, wind load and temperature of the membrane surface, and the structural creep can be controlled to an acceptable range.

The design method of the invention ensures that the membrane material is stressed reasonably, the stress of the steel cable is lower and the performance of the steel cable can be fully exerted; the cable net linear curve is smoothly transited, and the membrane surface curved surface is smoothly transited; the construction speed can be accelerated, and the construction quality is improved; the installation process is simplified, and the construction efficiency is improved.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims

1. A design method of a large-curvature cable membrane structure is characterized by comprising the following steps:

(7) processing the selected membrane material, including modeling, blanking, cutting and heat sealing; the film material adopts a film material which takes ethylene-tetrafluoroethylene copolymer as a main material and comprises the following components in parts by weight: 60-75 parts of ethylene-tetrafluoroethylene, 25-30 parts of silicon dioxide, 10-12 parts of titanium dioxide, 3-5 parts of an auxiliary crosslinking agent, 5-6 parts of a coupling agent, 3-4 parts of zinc distearate, 5-8 parts of tert-butyl hydroperoxide, 5-10 parts of dibutyl phthalate and 2-4 parts of N, N-dimethylformamide; the preparation method comprises the steps of weighing the components in parts by weight, adding the ethylene-tetrafluoroethylene and the tertiary butyl hydroperoxide into an internal mixer at the temperature of 70-80 ℃, uniformly mixing, and continuously stirring to react for 2-3h at the temperature of 80-90 ℃; then adding the rest components into the mixture, and uniformly stirring the mixture for 1 to 1.5 hours; finally, extruding the mixture by a screw extruder at the temperature range of 280-300 ℃ to obtain a film material mainly comprising the ethylene-tetrafluoroethylene copolymer;

3) film surface examination, and after confirming that no errors exist, the lapping size of film surface heat seal is required to be considered when the film surface is used for blanking in blanking processing;

2. The design method of large-curvature cable membrane structure as claimed in claim 1, wherein in the step (2), the selection of tension option during the form-finding process is to neglect the bending stiffness; selecting a triangular unit during element division, selecting 650MPa as the elastic modulus of a membrane material, and selecting 0.42 as the Poisson ratio of the membrane material; simulating a guy cable by using a LINK10 unit, wherein the elastic modulus is 1.60 multiplied by 105MPa, the Poisson ratio is 0.3, and prestressing force is applied to the guy cable unit by using a method for changing initial strain; and cooperatively searching the shape of the cable membrane by adopting a small elastic modulus method.

3. The design method of large-curvature cable membrane structure as claimed in claim 2, wherein in step (2), the vertical cable arrangement is first determined by calculation before the shape-finding analysis, and then the shape-finding analysis is carried out on 3-5 transverse cables.

4. The design method of the large-curvature cable membrane structure is characterized in that in the step (3), the maximum stress is strictly controlled during the design of the thickness of the membrane structure, and the maximum stress does not exceed 9 MPa; simulating wind load to apply acting force to the membrane surface in a wind pressure or wind suction mode, wherein the stress is in inverse proportion to the unit length section area of the membrane material, namely the thickness of the membrane material; selecting a film material with the thickness of 280-300 μm.

5. The design method of the large-curvature cable membrane structure as claimed in claim 4, wherein in the step (4), the structural system is determined to be a single-layer membrane reinforced cable net structure; the selection and optimization of the cable net arrangement scheme comprise the steps of carrying out stress analysis and structural design of a cable net system by adopting ANSYS software and 3D3S software, determining that a longitudinal and transverse bidirectional cable net arrangement scheme is adopted, wherein longitudinal cables are mainly stressed steel cables, 7-10 vertical steel cables are arranged on a middle diaphragm, and 3-6 vertical steel cables are arranged on an edge diaphragm; five cables are determined to be arranged on the transverse steel cable through stress analysis and shape finding; the diameter selection of the steel cable comprises the step of researching the internal force and displacement of the steel cable under different steel cable arrangement schemes under the wind load action of a cable net system by ANSYS software, wherein the steel cable with the diameter of 12-15mm is adopted.