CN117309317A - Annular floating platform wave load testing method - Google Patents
Annular floating platform wave load testing method Download PDFInfo
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- 238000007667 floating Methods 0.000 title claims abstract description 154
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M10/00—Hydrodynamic testing; Arrangements in or on ship-testing tanks or water tunnels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
- G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
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Abstract
The application discloses a method for testing wave load of an annular floating platform, which relates to the technical field of safety and reliability of marine engineering structures. According to the closed type measuring structure, the end faces of the measuring beams distributed at the measuring section of each model are rigidly connected with the end faces of the measuring beams distributed at the measuring section of the other model, so that the accuracy of wave load transmission of the annular floating platform with the inner domain can be effectively improved, and the wave load measuring error is reduced.
Description
Technical Field
The application relates to the technical field of safety and reliability of ocean engineering structures, in particular to a method for testing wave load of an annular floating platform.
Background
The annular floating platform can be used as a large floating body and can be used as an offshore travel complex floating platform, and the attractive appearance and the comfortable environment of the annular floating platform are great advantages. However, because the large floating body is subjected to the combined action of multiple loads such as stormy waves and currents in a real marine environment, the structural form of the large floating body is complex, the characteristics of the hydrodynamic wave load suffered by the large floating body are difficult to grasp, the structural design of the large floating body is supported by corresponding standard specifications, if the external wave load of the annular floating platform cannot be accurately determined, the structural design is challenged, the maximum bearing capacity of the structure can be exceeded even under the action of the extreme marine environment load, the local area structure is damaged, the local damage of the ultra-large floating body is caused, and the whole ultra-large floating body is possibly disabled in severe cases, so that the disastrous result is formed.
At present, a plurality of difficulties exist in the wave load model test of the annular floating platform in a complex marine environment, two ends of a common ship measuring beam are of free structures, and the annular floating platform has an inner domain, and if the model design is carried out by adopting the currently known common ship model test method, the load transfer of the annular floating platform is inaccurate, so that the measuring error is increased.
Disclosure of Invention
The applicant provides a method for testing the wave load of an annular floating platform aiming at the technical problems of inaccurate load transmission and large measurement error and the technical requirements of the existing wave load model test, and the technical scheme of the method is as follows:
based on the principles of geometric similarity and motion similarity, the molded line of the model body with the preset reduction ratio lambda is designed according to the molded line of the real-scale annular floating platform, the real-scale annular floating platform and the model body both adopt annular structures, and an inner-domain water body is enclosed inside the annular structures.
And determining a plurality of real-scale measurement sections with the section load of the real-scale annular floating platform as a maximum value and corresponding model measurement sections in the model body, and acquiring rigidity parameters of the real-scale annular floating platform at each real-scale measurement section.
And determining the specification of the measuring beam distributed at the corresponding model measuring section of the model body according to the rigidity parameter of the real-scale annular floating platform at each real-scale measuring section based on the rigidity similarity relation.
Arranging measuring beams with corresponding specifications at each model measuring section of the model body, wherein the length direction of each measuring beam is perpendicular to the model measuring section where the measuring beam is positioned, and the measuring beams are rigidly fixed and restrained at two sides of the model measuring section through mounting brackets fixed on the model body respectively; the end face of the measuring beam arranged at the measuring section of each model is rigidly connected with the end face of the measuring beam arranged at the measuring section of other models to form a closed measuring structure.
Strain gages are respectively distributed on each measuring beam, an annular floating platform wave load test model is manufactured, and the annular floating platform wave load test model is utilized for wave load test.
The further technical scheme is that determining the specification of the measuring beam arranged at the corresponding model measuring section of the model body comprises:
determining the elastic modulus E of each measuring beam distributed at the corresponding model measuring section of the model body according to the rigidity parameter of the real-scale annular floating platform at each real-scale measuring section based on the rigidity similarity relation m And moment of inertia I m 。
Elastic modulus E of each measuring beam laid at each model measuring section of the model body m Determining the material type of each measuring beam, and determining the inertia moment I of each measuring beam at each model measuring section of the model body m The cross-sectional dimensions of the individual measuring beams laid out are determined.
The further technical proposal is that the rigidity parameter is bending rigidity, the rigidity similarity relationship is bending rigidity similarity relationship, and the elastic modulus E of the measuring beam distributed at the corresponding measuring section of the model body is determined m And moment of inertia I m Comprising the following steps:
measuring flexural stiffness at a section based on each model of the model bodyIs of (2)Arrive at->Binding flexural rigidity similarity relationship->Determine->Bending rigidity of full-scale annular floating platform in full-scale measurement section>Substituting to obtain elastic modulus E of corresponding model measurement section in model body m And moment of inertia I m The method comprises the steps of carrying out a first treatment on the surface of the Where n is the number of measurement beams laid at the model measurement profile.
The further technical scheme is that the stiffness parameter is linear stiffness, the stiffness similarity relationship is linear stiffness similarity relationship, and the method further comprises: determining the effective length L of a measuring beam distributed at the corresponding model measuring section of the model body according to the linear rigidity of the real-scale annular floating platform at each real-scale measuring section based on the linear rigidity similarity relation m The method comprises the steps of carrying out a first treatment on the surface of the Effective length L m The distance between the ends of the constraint is fixed for measuring the beam rigidity.
It is further proposed to determine the modulus of elasticity E of the measuring beam arranged at each model measuring section of the model body m Moment of inertia I m And effective length L m The method of (1) comprises:
measuring line stiffness at a profile based on each model of the model bodyExpression +.>Bond line stiffness similarity relationship->Determine->Line stiffness of full-scale annular floating platform in full-scale measurement section>Substituting to obtain elastic modulus E of corresponding model measurement section in model body m Moment of inertia I m And effective length L m The method comprises the steps of carrying out a first treatment on the surface of the Where n is the number of measurement beams laid at the model measurement profile.
The further technical proposal is that the moment of inertia I of the measuring beam distributed at the measuring section according to each model m Determining the cross-sectional dimensions of the deployed measuring beam includes:
the measuring beam adopts a hollow cylindrical tube structure, and according to the moment of inertia I of the measuring beam m According toThe cross-sectional dimensions of the measuring beam are determined, the cross-sectional dimensions of the measuring beam comprising an inner diameter D and an outer diameter D.
The method comprises the following steps that the inside of a model body further comprises a plurality of stiffening beams, each stiffening beam is respectively arranged in other areas except for each measuring section in the model body, the end face of each measuring beam arranged at each model measuring section is directly and rigidly connected with the end face of each measuring beam arranged at the other model measuring section, or after the end face of each measuring beam arranged at the model measuring section is rigidly connected with the end face of the stiffening beam, the end face of each stiffening beam is rigidly connected with the end face of each measuring beam arranged at the other model measuring section;
when n measuring beams are distributed at one model measuring section, wherein n is more than or equal to 2, the n measuring beams are arranged in parallel at intervals and are positioned on the same plane, the same ends of the n measuring beams are rigidly fixed and restrained through the same mounting bracket, and the end faces of the measuring beams positioned at the middle position along the arrangement direction are rigidly connected with the end faces of the measuring beams or the end faces of the reinforcing beams distributed at the other model measuring sections.
The further technical scheme is that the strain gauge is respectively arranged on each measuring beam, and the strain gauge comprises the following components for each measuring beam:
a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a fifth strain gauge and a sixth strain gauge are arranged on the outer side of the pipe wall of the measuring beam; the first strain gauge and the second strain gauge are connected in a half-bridge manner and symmetrically distributed on the cross section of the measuring beam along the gravity direction, the third strain gauge and the sixth strain gauge are symmetrically distributed on the cross section of the measuring beam along the second direction, the fourth strain gauge and the fifth strain gauge are symmetrically distributed on the cross section of the measuring beam along the third direction, the third strain gauge, the fourth strain gauge, the fifth strain gauge and the sixth strain gauge are connected in a full-bridge manner, and the second direction and the third direction form included angles of 45 degrees with the gravity direction respectively.
The further technical scheme is that the wave load test by using the annular floating platform wave load test model comprises the following steps:
the method comprises the steps of placing an annular floating platform wave load test model in a wave test environment, testing the annular floating platform model through preset wave motion parameters, obtaining a wave bending moment of the annular floating platform wave load test model at a model measurement section through a first strain gauge and a second strain gauge which are arranged on a measurement beam at the measurement section of each model, and obtaining a wave shearing force of the annular floating platform wave load test model at the model measurement section through a third strain gauge, a fourth strain gauge, a fifth strain gauge and a sixth strain gauge which are arranged on the measurement beam at the measurement section of each model.
Based on the wave bending moment and the wave shearing force of the annular floating platform wave load test model at each model measurement section, the wave bending moment and the wave shearing force of the real-scale annular floating platform at the corresponding real-scale measurement section are obtained through load similarity transformation, and the wave load of the real-scale annular floating platform at the corresponding real-scale measurement section is obtained based on the wave bending moment and the wave shearing force of the real-scale annular floating platform at each real-scale measurement section.
The further technical proposal is that the expression of the load similarity relation transformation is as follows:
M s ＝λ 4 M m ；
F s ＝λ 3 F m ；
wherein M is s For measuring the wave bending moment of the section of the full-scale annular floating platform in the full-scale, M m Measuring wave bending moment of section in model for annular floating platform wave load test model, F s For measuring the wave shearing force of the section of the real-scale annular floating platform in the real scale, F m And measuring the wave shear force of the section of the annular floating platform wave load test model in the model.
The beneficial technical effects of this application are:
according to the annular floating platform wave load testing method, the molded lines of the model body are designed by combining the similar theory of hydrodynamic characteristics and structural dynamic characteristics, in order to more accurately analyze the wave load distribution rule of the annular floating platform with the real scale, the real scale measurement section with the real scale annular floating platform section load as the maximum value is obtained, and the measurement beams are distributed on the corresponding model measurement section in the model body, so that the measured wave load has more research value; and the distributed measuring beams have a rigidity similar relation with the real-scale measuring section, so that the accuracy of a measuring result is ensured. In addition, the end face of the measuring beam arranged at each model measuring section is rigidly connected with the end face of the measuring beam arranged at other model measuring sections to form a closed measuring structure, and compared with the traditional measuring beam connecting mode, the closed measuring beam connecting system is more suitable for an annular floating platform with an inner domain, can effectively improve the accuracy of wave load transmission and reduce wave load measuring errors. According to the method, the wave shearing force and the wave bending moment at the section of the model measurement are obtained through more accurate measurement through the combined connection mode of the full bridge and the half bridge of the strain gauge, and then the corresponding wave load is obtained through calculation.
According to the method and the device, when the preset scaling ratio of the model body and the measurement beam size are determined, the accommodation capacity of the wave test environment and the convenience in processing are fully considered, and the measurement beam and other components inside the model body can be effectively connected and distributed. When the size of the measuring beam is determined, the standard profile is preferably selected, so that the processing difficulty and the economic cost are better reduced.
In order to ensure that the rigidity of the measuring beam in the gravity direction is consistent with that of the measuring beam in the horizontal direction, the cross section size of the measuring beam of the hollow cylindrical tube is larger than that of the measuring beam of the solid cylindrical tube, high-precision processing is facilitated, and the error rate is reduced, so that the solid cylindrical tube structure is selected as the measuring beam in one embodiment.
Drawings
FIG. 1 is a schematic diagram of a method of testing wave load of an annular floating platform in one embodiment of the present application.
FIG. 2 is a schematic block diagram of a floating platform of the ocean in one embodiment of the present application.
FIG. 3 (a) is a schematic view of the connection of a measuring beam to a mounting bracket when a measuring beam is deployed at a model measuring section in one embodiment of the present application.
FIG. 3 (b) is a schematic diagram of the connection of the measurement beams to the mounting bracket when three measurement beams are deployed at the model measurement profile in one embodiment of the present application.
FIG. 4 is a schematic diagram of a closed measuring beam connection system of a floating platform of the ocean in one embodiment of the present application.
Fig. 5 is a schematic diagram of strain gage distribution in one embodiment of the present application.
Reference numerals: 1. a measuring beam; 2. a first mounting bracket; 3. a second mounting bracket; 4. and a connecting piece.
Detailed Description
The following describes the embodiments of the present application further with reference to the accompanying drawings.
As shown in fig. 1, a method for testing wave load of an annular floating platform of the present application includes:
s110, designing a molded line of a model body with a preset scale ratio according to the molded line of the real-scale annular floating platform based on the principles of geometric similarity and motion similarity, wherein the real-scale annular floating platform and the model body both adopt annular structures, and an inner-domain water body is enclosed inside the annular structures.
In order to ensure that the wave load measured by the annular floating platform wave load test model can accurately correspond to the real-scale annular floating platform, the model body is required to follow the principles of geometric similarity and motion similarity, wherein the geometric similarity means that the real-scale annular floating platform and the model body are scaled according to equal proportion, and the motion similarity means that the Fourier number and the Storholohar number of the real-scale annular floating platform and the model body are the same. Optionally, the model body is also consistent with the weight distribution of the full-scale annular floating platform.
Because the annular floating platform wave load test model finally designed by the application is used for wave load test, the holding capacity of the wave test environment is required to be considered when the preset reduction ratio lambda is selected, so that the preset reduction ratio lambda of the model body is smaller than or equal to a first reduction ratio threshold value; meanwhile, considering that a measuring beam is required to be arranged in the model body for wave load test, if the preset reduction ratio lambda is too small, the error rate of the measuring beam in processing is larger, and further the wave load test result is affected, therefore, the preset reduction ratio lambda of the model body is required to be larger than or equal to the second reduction ratio threshold, and the values of the first reduction ratio threshold and the second reduction ratio threshold are determined according to actual conditions.
The wave load test model designed in the application is applicable to annular floating platforms containing inner domains, and the term annular is used to mainly indicate that one or more inner domains are contained in the platform, and the annular can be any one of a circular shape, an oval shape, a heart shape, a drop shape or other irregular shapes, and is not limited in the application.
S120, determining a plurality of real-scale measurement sections with maximum section loads in the real-scale annular floating platform and corresponding model measurement sections in the model body, and acquiring rigidity parameters of the real-scale annular floating platform at each real-scale measurement section.
Optionally, based on the specific shape, material and weight distribution of the real-scale annular floating platform, the position of the real-scale measurement section of the real-scale annular floating platform and the rigidity parameter of each real-scale measurement section are obtained through software simulation.
S130, determining the specification of the measuring beam arranged at the corresponding model measuring section of the model body according to the rigidity parameter of the real-scale annular floating platform at each real-scale measuring section based on the rigidity similarity relation.
According to the method, the measuring beams are distributed on the model measuring sections corresponding to the real-scale measuring sections with the real-scale annular floating platform section load as the maximum value, so that the measured wave load has a higher research value; and the distributed measuring beams have a rigidity similar relation with the real-scale measuring section, so that the accuracy of a measuring result is ensured.
S140, arranging measuring beams with corresponding specifications at each model measuring section of the model body, wherein the length direction of each measuring beam is perpendicular to the model measuring section where the measuring beam is positioned, and the measuring beams are rigidly fixed and restrained at two sides of the model measuring section through mounting brackets fixed on the model body respectively; the end face of the measuring beam arranged at the measuring section of each model is rigidly connected with the end face of the measuring beam arranged at the measuring section of other models to form a closed measuring structure.
Because the annular floating platform has an inner domain, the existing measuring beam connection modes are mostly open connection, such as 'well' -shaped connection, and the connection modes are not suitable for the annular floating platform with the inner domain, because the end faces of the measuring beams are not associated, the load transmission is inaccurate, and the measured wave load is larger. The measuring beams designed in the application are connected in a closed mode, the measuring Liang Duanmian of each model measuring section is connected end to form an annular closed structure, and in one embodiment, the measuring beams are connected with the stiffening beams in a combined mode, and a closed measuring beam connecting system is obtained based on the structural shape of the annular floating platform.
And S150, respectively arranging strain gages on each measuring beam, manufacturing to obtain an annular floating platform wave load test model, and carrying out wave load test by using the annular floating platform wave load test model.
According to the method, through the combined connection mode of the full bridge and the half bridge of the strain gauge, the wave shearing force and the wave bending moment at the section of the model measurement are obtained through more accurate measurement, and then the corresponding wave load is obtained through calculation.
In order to more clearly describe the method of testing wave load on an annular floating platform of the present application, another embodiment of the present application will be described in detail below with reference to the accompanying drawings.
S210, designing a molded line of a model body with a preset reduction ratio lambda according to the molded line of the real-scale annular floating platform based on the principles of geometric similarity and motion similarity, wherein the real-scale annular floating platform and the model body both adopt annular structures, and an inner-domain water body is enclosed inside the annular structures.
Because the annular floating platform wave load test model designed by the application needs to be placed in a wave test environment to receive wave impact, the model body needs to be guaranteed to have enough strength, difficult deformation, smooth surface, sealing and waterproofing. Optionally, the model body is made of glass fiber reinforced plastic material.
The motion similarity of the model body and the real-scale annular floating platform is as follows:
wherein Fr is Friedel number, V s Is the sailing speed of the real-scale annular floating platform, L s Length g of real-scale annular floating platform s Is the gravity acceleration of the full-scale annular floating platform, V m The sailing speed L of the annular floating platform wave load test model m G is the length of the annular floating platform wave load test model m The gravity acceleration is the gravity acceleration of the annular floating platform wave load test model, st is the St-Ruohan number, t s Is the sailing duration of the real-scale annular floating platform, t m The model is the sailing duration of the annular floating platform wave load test model.
S220, determining a plurality of real-scale measurement sections with maximum section loads in the real-scale annular floating platform and corresponding model measurement sections in the model body, and acquiring rigidity parameters of the real-scale annular floating platform at each real-scale measurement section.
After the positions of a plurality of real-scale measurement sections and the rigidity parameters of each real-scale measurement section are determined, the model body is divided into a plurality of modules based on the real-scale measurement sections. Alternatively, the annular floating platform wave load test model is similar to the full-size floating platform in gravity center position and inertia by configuring each module of the annular floating platform wave load test model with different weights. In one embodiment, as shown in FIG. 2, which is a schematic block division diagram of a floating platform of the ocean, 10 real-scale measurement profiles S1-S10 with maximum profile loads in the floating platform of the ocean are obtained through software simulation, and the floating platform of the ocean is divided into 7 blocks M1, M2, M3, M4-1, M4-2, M5-1 and M5-2 based on the 10 real-scale measurement profiles. Exemplary, the empty ship weight and gross weight of each module of the ocean floating platform wave load test model are shown in table 1, wherein the empty ship weight is the weight of the model body, and the gross weight is the gross weight of the ocean floating platform wave load test model after adding the counterweight.
TABLE 1 hollow ship weight and gross weight of each module of ocean floating platform wave load test model
| Module | Empty ship weight (kg) | Total weight (kg) |
| M1 | 30.0 | 92.4 |
| M2 | 28.0 | 90.3 |
| M3 | 45.0 | 141.6 |
| M4-1 | 22.0 | 63.8 |
| M4-2 | 22.0 | 63.8 |
| M5-1 | 30.0 | 68.0 |
| M5-2 | 30.0 | 68.0 |
S230, determining the specification of the measuring beam arranged at the corresponding model measuring section of the model body according to the rigidity parameter of the real-scale annular floating platform at each real-scale measuring section based on the rigidity similarity relation.
In the present embodiment, the elastic modulus E of each measurement beam laid at the corresponding model measurement section of the model body is determined from the stiffness parameter of the full-scale annular floating platform at each full-scale measurement section based on the stiffness similarity relationship m And moment of inertia I m The method comprises the steps of carrying out a first treatment on the surface of the Elastic modulus E of each measuring beam laid at each model measuring section of the model body m Determining the material type of each measuring beam,moment of inertia I of each measuring beam laid at each model measuring section of the model body m The cross-sectional dimensions of the individual measuring beams laid out are determined.
Optionally, if the stiffness parameter is bending stiffness and the stiffness similarity relationship is bending stiffness similarity relationship, determining elastic modulus E m And moment of inertia I m The method of (1) comprises: measuring flexural stiffness at a section based on each model of the model bodyExpression of (2)Binding flexural rigidity similarity relationship->Determine->Bending rigidity of full-scale annular floating platform in full-scale measurement section>Substituting to obtain elastic modulus E of corresponding model measurement section in model body m And moment of inertia I m The method comprises the steps of carrying out a first treatment on the surface of the Where n is the number of measurement beams laid at the model measurement profile.
Optionally, the stiffness parameter is linear stiffness, the stiffness similarity relationship is linear stiffness similarity relationship, and the method further includes: determining the effective length L of a measuring beam distributed at the corresponding model measuring section of the model body according to the linear rigidity of the real-scale annular floating platform at each real-scale measuring section based on the linear rigidity similarity relation m The method comprises the steps of carrying out a first treatment on the surface of the Effective length L m The distance between the ends of the constraint is fixed for measuring the beam rigidity.
When the stiffness parameter is the linear stiffness, the elastic modulus E is determined m Moment of inertia I m And effective length L m The method of (1) comprises: measuring line stiffness at a profile based on each model of the model bodyExpression +.>Bond line stiffness similarity relationship->Determine->Line stiffness of full-scale annular floating platform in full-scale measurement section>Substituting to obtain elastic modulus E of corresponding model measurement section in model body m Moment of inertia I m And effective length L m 。
In one embodiment, the moment of inertia I of the measurement beam laid out at the measurement profile is measured according to each model m The cross-sectional dimensions of the deployed measuring beams are determined. To ensure that the rigidity of the measuring beam in the direction of gravity and in the horizontal direction is uniform, the measuring beam can be designed to be circular in cross section. And under the same rigidity, the cross section size of the hollow cylindrical tube measuring beam is larger than that of the solid cylindrical tube measuring beam, so that the high-precision processing is facilitated, and the error rate is reduced. Therefore, the measuring beam of the embodiment adopts a hollow cylindrical tube structure, and the moment of inertia I of the measuring beam m According toThe cross-sectional dimensions of the measuring beam are determined, the cross-sectional dimensions of the measuring beam comprising an inner diameter D and an outer diameter D. In addition, the length of the measurement beam may be selected empirically when considering stiffness similarities.
Since the measuring beam is required to be installed inside the model body, after the relational expression of the specification of the measuring beam is obtained based on the rigidity similarity relationship, although there are various combination modes, suitable specifications are designed in combination with the dimensions of the model body and other structures and the convenience of processing. When selecting the material of the measuring beam, for example, if the material of the real-size measuring section of the real-size annular floating platform is steel, the measuring beam of the model measuring section can be made of aluminum alloy material, so that the measuring beam has better elasticity, stability and corrosion resistance on the premise of meeting the similar rigidity, and further, better wave load testing effect is achieved. In one embodiment, the model body also comprises a mounting bracket, a stiffening beam and other structures, so that the cross section size of the measuring beam is ensured not to be excessively large; and because the machining precision can be reduced when the measuring beam is too small, and the strain gauge cannot be effectively attached, the cross section size of the measuring beam is also required to be ensured not to be too small. When the length of the measuring beam is selected, the too short measuring beam can affect the rigid fixing constraint at two ends of the measuring beam and the fitting of the strain gauge, and the measuring Liang Guochang can make the connection of the measuring beam and the stiffening beam difficult. After the material and the size range of the measuring beam are determined, the cross section size of the measuring beam can be selected from standard sectional materials, so that the cost is reduced.
In one example, E is calculated based on flexural rigidity similarity m I m Equal to 168.28Gpa cm 4 Calculated based on similar relation of linear rigidityEqual to 2.8Gpa cm 3 . To meet the design requirement, when 1 measuring beam is arranged on the model measuring section, the measuring Liang Xuan is an aluminum alloy hollow cylindrical tube, the outer diameter of the cross section of the measuring beam is 30mm, the inner diameter of the cross section is 24mm, the total length is 60cm, the effective length is 15cm, and the elastic modulus E of the measuring beam is designed m 71.7Gpa, moment of inertia I m 2.347cm 4 Effective length L m 15cm, and accords with the similar relation of rigidity. For example, when 3 measuring beams are arranged on the model measuring section, the measuring beam Liang Xuan is a hollow cylindrical tube made of aluminum alloy, the outer diameter of the cross section of the measuring beam is 22mm, the inner diameter of the cross section is 17mm, the total length is 60cm, the effective length is 15cm, and the elastic modulus E of the measuring beam is designed m 71.7Gpa, moment of inertia I m 2.220cm 4 Effective length L m 15cm, and accords with the similar relation of rigidity. When the specification of the measuring beam is selected, if the standard profile is not selected, the standard profile is required to be reprocessed, the processing precision is difficult to ensure, and larger errors can be introduced. In this example, therefore, the measurement beam is a standard profile that sacrifices some accuracy of stiffness similarity within the error range threshold.
In another embodiment, the gauge of the measurement beam may be determined by software simulation. Firstly, constructing a virtual connector in software, wherein the virtual connector is a beam structure with two ends fixed and constrained, and inputting preset specification parameters including elastic modulus, moment of inertia and beam length. And applying force F to the virtual connector, and recording the corresponding bending moment M, the linear displacement difference delta d and the angular displacement difference delta theta of the two ends of the virtual connector. Determining the line stiffness of a real-scale measurement profile based on a specific real-scale annular floating platform when the measurement beams are considered to satisfy the line stiffness similarity relationshipAfter that, by the line stiffness similarity formula +.>Calculating to obtain the required line stiffness K of the virtual connector T . Repeatedly changing preset specification parameters, wherein the formula is based on +.>Calculating to obtain the corresponding line stiffness K T Up to the line stiffness K of the virtual connector T Line stiffness to real-scale measurement profile>And the similar relation of the linear rigidity is satisfied, and the corresponding specification parameters are used as the specification of the measuring beam. When the measurement beams are considered to meet the rotation stiffness similarity relationship, determining the rotation stiffness K of the real-scale measurement section based on the specific real-scale annular floating platform R After that, by the line stiffness similarity formula +.>Calculating the required rotational rigidity K of the virtual connector R . Repeatedly changing preset specification parameters, wherein the formula is based on +.>Calculating to obtain corresponding rotation rigidity K R Up to the rotational stiffness K of the virtual connector R Rotational stiffness of the cross section measured with real dimensions>And the similar relation of the rotation rigidity is satisfied, and the corresponding specification parameters are used as the specification of the measuring beam.
S240, arranging measuring beams with corresponding specifications at each model measuring section of the model body, wherein the length direction of each measuring beam is perpendicular to the model measuring section where the measuring beam is positioned, and the measuring beams are rigidly fixed and restrained at two sides of the model measuring section through mounting brackets fixed on the model body respectively; the end face of the measuring beam arranged at the measuring section of each model is rigidly connected with the end face of the measuring beam arranged at the measuring section of other models to form a closed measuring structure.
Optionally, the mounting brackets are fixed inside the model body, and each measurement profile matches the first mounting bracket and the second mounting bracket. When n measuring beams are distributed at a model measuring section, n connecting pieces which are arranged at intervals are arranged in the length direction of the first mounting bracket and the second mounting bracket. The length direction of each measuring beam is perpendicular to the length direction of the mounting bracket, one end of each measuring beam is rigidly fixed and restrained on one connecting piece of the first mounting bracket, and the other end of each measuring beam is rigidly fixed and restrained on one connecting piece of the second mounting bracket. Optionally, the connecting piece is provided with a plurality of bolts for fastening. For example, as shown in fig. 3 (a), when a measuring beam 1 is arranged at the measuring section of the model, a connecting piece 4 is respectively arranged on the first mounting bracket 2 and the second mounting bracket 3, and two ends of the measuring beam 1 are respectively rigidly fixed and restrained on the connecting pieces of the first mounting bracket 2 and the second mounting bracket 3. For example, as shown in fig. 3 (b), when three measuring beams 1 are arranged at the model measuring section, 3 connecting pieces 4 are respectively arranged on the first mounting bracket 2 and the second mounting bracket 3, and two ends of the measuring beam 1 are respectively rigidly fixed and restrained on the connecting pieces of the first mounting bracket 2 and the second mounting bracket 3.
Optionally, the inside of the model body further includes a plurality of stiffening beams, each stiffening beam is respectively arranged in other areas except for each measuring section in the model body, the end face of the measuring beam arranged at each measuring section of the model is directly rigidly connected with the end faces of the measuring beams arranged at the measuring sections of other models, or after the end faces of the measuring beams arranged at the measuring sections of the model are rigidly connected with the end faces of the stiffening beams, the end faces of the stiffening beams are rigidly connected with the end faces of the measuring beams arranged at the measuring sections of other models.
When the measuring beams arranged at the two model measuring sections are rigidly connected through a stiffening beam, the two end surfaces of the stiffening beam are respectively connected with the end surfaces of the measuring beams arranged at the two model measuring sections; when the measuring beams arranged at the two model measuring sections are rigidly connected through two or more than two reinforcing beams, the reinforcing beams are rigidly connected, the end face of one reinforcing beam is connected with the end face of the measuring beam arranged at the one model measuring section, and the end face of the other reinforcing beam is connected with the end face of the measuring beam arranged at the other model measuring section.
When n measuring beams are distributed at one model measuring section, wherein n is more than or equal to 2, the n measuring beams are arranged in parallel at intervals and are positioned on the same plane, the same ends of the n measuring beams are rigidly fixed and restrained through the same mounting bracket, and the end faces of the measuring beams positioned at the middle position along the arrangement direction are rigidly connected with the end faces of the measuring beams or the end faces of the reinforcing beams distributed at the other model measuring sections. And in one embodiment n is an odd number, considering that the measuring beams on the model measuring profile have better stability when symmetrically distributed with respect to the stiffening beam.
The greater the number of measurement beams on a model measurement profile, the greater the load carrying capacity of the model measurement profile. Since the ship conditions are different for each real-size annular floating platform, a more accurate simulation can be performed by laying a corresponding number of measurement beams at different model measurement profiles. In one embodiment, taking the floating platform of the ocean as an example, as shown in fig. 4, three measuring beams are arranged at a model measuring section S5, one measuring beam is arranged at the rest model measuring section, and under the condition of uniform rigidity, the bearing capacity of the three measuring beams is improved by 15% compared with that of one measuring beam.
S250, strain gages are respectively distributed on each measuring beam, an annular floating platform wave load test model is manufactured, and the annular floating platform wave load test model is used for carrying out wave load test.
The strain gages are placed on each measurement beam separately, as shown in fig. 5, including for each measurement beam: a first strain gauge G1, a second strain gauge G2, a third strain gauge G3, a fourth strain gauge G4, a fifth strain gauge G5 and a sixth strain gauge G6 are arranged on the outer side of the pipe wall of the measuring beam; the first strain gauge G1 and the second strain gauge G2 are connected in a half-bridge manner and symmetrically distributed on the cross section of the measuring beam along the gravity direction, the third strain gauge G3 and the sixth strain gauge G6 are symmetrically distributed on the cross section of the measuring beam along the second direction, the fourth strain gauge G4 and the fifth strain gauge G5 are symmetrically distributed on the cross section of the measuring beam along the third direction, the third strain gauge G3, the fourth strain gauge G4, the fifth strain gauge G5 and the sixth strain gauge G6 are connected in a full-bridge manner, and the second direction and the third direction form 45-degree included angles with the gravity direction respectively.
In one embodiment, when n measuring beams are distributed at a model measuring section and n is more than or equal to 2, one measuring beam which is positioned at the middle position in the parallel interval arrangement direction of the n measuring beams is used as a middle beam, and only the middle beam is selected to be distributed with strain gauges.
The wave load test by using the annular floating platform wave load test model comprises the following steps:
the method comprises the steps of placing an annular floating platform wave load test model in a wave test environment, testing the annular floating platform wave load test model through preset wave motion parameters, acquiring a wave bending moment of the annular floating platform wave load test model at a model measurement section through a first strain gauge G1 and a second strain gauge G2 which are arranged on a measurement beam at the position of each model measurement section, and acquiring a wave shearing force of the annular floating platform wave load test model at the position of the model measurement section through a third strain gauge G3, a fourth strain gauge G4, a fifth strain gauge G5 and a sixth strain gauge G6 which are arranged on a measurement beam at the position of each model measurement section.
In one embodiment, the wave motion parameters include any one or more of wave height, wave period, wave direction. And testing the wave load suffered by the annular floating platform wave load test model under the wave conditions corresponding to different wave motion parameters through presetting the wave motion parameters, recording test data, and obtaining the distribution rule of the wave load on the corresponding real-size annular floating platform through analyzing the test data.
Based on the wave bending moment and the wave shearing force of the annular floating platform wave load test model at each model measurement section, the wave bending moment and the wave shearing force of the real-scale annular floating platform at the corresponding real-scale measurement section are obtained through load similarity transformation, and the wave load of the real-scale annular floating platform at the corresponding real-scale measurement section is obtained based on the wave bending moment and the wave shearing force of the real-scale annular floating platform at each real-scale measurement section.
The expression of the load similarity transformation is: m is M s ＝λ 4 M m ；F s ＝λ 3 F m The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is s For measuring the wave bending moment of the section of the full-scale annular floating platform in the full-scale, M m Measuring wave bending moment of section in model for annular floating platform wave load test model, F s For measuring the wave shearing force of the section of the real-scale annular floating platform in the real scale, F m And measuring the wave shear force of the section of the annular floating platform wave load test model in the model.
What has been described above is only a preferred embodiment of the present application, which is not limited to the above examples. It is to be understood that other modifications and variations which may be directly derived or contemplated by those skilled in the art without departing from the spirit and concepts of the present application are to be considered as being included within the scope of the present application.
Claims (10)
1. The annular floating platform wave load testing method is characterized by comprising the following steps of:
based on the principles of geometric similarity and motion similarity, designing a molded line of a model body with a preset reduction ratio lambda according to the molded line of a real-scale annular floating platform, wherein the real-scale annular floating platform and the model body both adopt an annular structure, and an inner-domain water body is enclosed inside the annular structure;
determining a plurality of real-scale measurement sections with maximum section loads in the real-scale annular floating platform and corresponding model measurement sections in the model body, and acquiring rigidity parameters of the real-scale annular floating platform at each real-scale measurement section;
determining the specification of a measuring beam arranged at a corresponding model measuring section of the model body according to the rigidity parameter of the real-scale annular floating platform at each real-scale measuring section based on the rigidity similarity relation;
arranging measuring beams with corresponding specifications at each model measuring section of the model body, wherein the length direction of each measuring beam is perpendicular to the model measuring section where the measuring beam is positioned, and the measuring beams are rigidly fixed and restrained at two sides of the model measuring section through mounting brackets fixed on the model body respectively; the end face of the measuring beam arranged at the measuring section of each model is rigidly connected with the end face of the measuring beam arranged at the measuring section of other models to form a closed measuring structure;
strain gauges are respectively distributed on each measuring beam, an annular floating platform wave load test model is manufactured, and the annular floating platform wave load test model is utilized for wave load test.
2. The method of annular floating platform wave load testing according to claim 1, wherein the determining the gauge of the measurement beams laid at the corresponding model measurement profile of the model body comprises:
based on the similar relation of rigidityDetermining the elastic modulus E of each measuring beam arranged at the corresponding model measuring section of the model body according to the rigidity parameter of the full-scale annular floating platform at each full-scale measuring section m And moment of inertia I m ；
Elastic modulus E of each measuring beam laid at each model measuring section of the model body m Determining the material type of each measuring beam, and determining the inertia moment I of each measuring beam at each model measuring section of the model body m The cross-sectional dimensions of the individual measuring beams laid out are determined.
3. The method according to claim 2, wherein the stiffness parameter is bending stiffness, the stiffness similarity relationship is bending stiffness similarity relationship, and the determining of the elastic modulus E of the measurement beams laid at the corresponding measurement sections of the model body m And moment of inertia I m Comprising the following steps:
measuring bending stiffness at a profile based on each model of the model bodyExpression +.>Binding flexural rigidity similarity relationship->Determine->Bending rigidity of the full-scale annular floating platform in full-scale measurement section>Substituting to obtain elastic modulus E of corresponding model measurement section in the model body m And moment of inertia I m The method comprises the steps of carrying out a first treatment on the surface of the Where n is the number of measurement beams laid at the model measurement profile.
4. The method of annular floating platform wave load testing according to claim 2, wherein the stiffness parameter is line stiffness and the stiffness similarity relationship is a line stiffness similarity relationship, the method further comprising: determining the effective length L of a measuring beam arranged at the corresponding model measuring section of the model body according to the linear rigidity of the full-scale annular floating platform at each full-scale measuring section based on the linear rigidity similarity relation m The method comprises the steps of carrying out a first treatment on the surface of the The effective length L m The distance between the two ends of the constraint is rigidly fixed for the measuring beam.
5. The method of testing wave load of an annular floating platform according to claim 4, characterized by determining the modulus of elasticity E of the measurement beams laid out at each model measurement section of the model body m Moment of inertia I m And effective length L m The method of (1) comprises:
measuring line stiffness at a profile based on each model of the model bodyExpression +.>Bond line stiffness similarity relationship->Determine->Line stiffness of the full-scale annular floating platform in full-scale measurement section>Substituting to obtain a corresponding model in the model bodyMeasuring modulus of elasticity E of section m Moment of inertia I m And effective length L m The method comprises the steps of carrying out a first treatment on the surface of the Where n is the number of measurement beams laid at the model measurement profile.
6. Method according to claim 2, characterized in that the moment of inertia I of the measuring beams laid out at the measuring section according to each model is m Determining the cross-sectional dimensions of the deployed measuring beam includes:
the measuring beam adopts a hollow cylindrical tube structure, and according to the inertia moment I of the measuring beam m According toThe cross-sectional dimensions of the measuring beam are determined, the cross-sectional dimensions of the measuring beam comprising an inner diameter D and an outer diameter D.
7. The method for testing the wave load of the annular floating platform according to claim 1, wherein the inside of the model body further comprises a plurality of stiffening beams, each stiffening beam is respectively arranged in other areas except for each measuring section in the model body, the end face of the measuring beam arranged at each measuring section of the model is directly and rigidly connected with the end faces of the measuring beams arranged at the measuring sections of the other models, or after the end faces of the measuring beams arranged at the measuring sections of the model are rigidly connected with the end faces of the stiffening beams, the end faces of the stiffening beams are rigidly connected with the end faces of the measuring beams arranged at the measuring sections of the other models;
when n measuring beams are distributed at one model measuring section, wherein n is more than or equal to 2, the n measuring beams are arranged in parallel at intervals and are positioned on the same plane, the same ends of the n measuring beams are rigidly fixed and restrained through the same mounting bracket, and the end faces of the measuring beams positioned at the middle position along the arrangement direction are rigidly connected with the end faces of the measuring beams or the end faces of the reinforcing beams distributed at the other model measuring sections.
8. The method of testing wave load of an annular floating platform according to claim 1, wherein said placing strain gages on each measurement beam comprises, for each measurement beam:
a first strain gauge, a second strain gauge, a third strain gauge, a fourth strain gauge, a fifth strain gauge and a sixth strain gauge are arranged on the outer side of the pipe wall of the measuring beam;
the first strain gauge and the second strain gauge are connected in a half-bridge manner and symmetrically distributed along the gravity direction on the cross section of the measuring beam, the third strain gauge and the sixth strain gauge are symmetrically distributed along the second direction on the cross section of the measuring beam, the fourth strain gauge and the fifth strain gauge are symmetrically distributed along the third direction on the cross section of the measuring beam, the third strain gauge, the fourth strain gauge, the fifth strain gauge and the sixth strain gauge are connected in a full-bridge manner, and the second direction and the third direction are respectively 45-degree included angles with the gravity direction.
9. The method of annular floating platform wave load testing according to claim 8, wherein the performing wave load testing using the annular floating platform wave load test model comprises:
placing the annular floating platform wave load test model in a wave test environment, and testing the annular floating platform model through preset wave motion parameters; the method comprises the steps that a first strain gauge and a second strain gauge which are arranged on a measuring beam at a measuring section of each model are used for obtaining a wave bending moment of the annular floating platform wave load test model at the measuring section of the model, and a third strain gauge, a fourth strain gauge, a fifth strain gauge and a sixth strain gauge which are arranged on the measuring beam at the measuring section of each model are used for obtaining a wave shearing force of the annular floating platform wave load test model at the measuring section of the model;
and converting the load similarity relationship based on the wave bending moment and the wave shearing force of the annular floating platform wave load test model at each model measurement section to obtain the wave bending moment and the wave shearing force of the real-scale annular floating platform at the corresponding real-scale measurement section, and obtaining the wave load of the real-scale annular floating platform at the corresponding real-scale measurement section based on the wave bending moment and the wave shearing force of the real-scale annular floating platform at each real-scale measurement section.
10. The method of claim 9, wherein the expression of load similarity transformation is:
M s ＝λ 4 M m ；
F s ＝λ 3 F m ；
wherein M is s Wave bending moment M of section is measured in full scale for the full scale annular floating platform m Measuring the wave bending moment of a section in the model for the annular floating platform wave load test model, F s Measuring the wave shear force of the section of the full-scale annular floating platform in full scale, F m And measuring the wave shear force of the section of the annular floating platform wave load test model in the model.
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