CN114919710A - Net frame type box floating raft structure and design method thereof - Google Patents
Net frame type box floating raft structure and design method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/58—Rafts, i.e. free floating waterborne vessels, of shallow draft, with little or no freeboard, and having a platform or floor for supporting a user
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B71/00—Designing vessels; Predicting their performance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B73/00—Building or assembling vessels or marine structures, e.g. hulls or offshore platforms
- B63B73/20—Building or assembling prefabricated vessel modules or parts other than hull blocks, e.g. engine rooms, rudders, propellers, superstructures, berths, holds or tanks
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Abstract
The invention relates to a net rack type box body floating raft structure and a design method thereof, wherein the structure comprises a net rack structure, an upper panel, a lower panel and a bulkhead; the grid structure is a spatial three-dimensional frame structure consisting of horizontal, longitudinal and horizontal plane truss structures; the plane truss structure is an open-web lattice type bending member formed by connecting rod pieces, and the rod pieces comprise chord members and web members; the upper panel is arranged on the upper surface of the horizontal plane truss at the top, and the lower panel is arranged on the upper surface of the horizontal plane truss at the bottom; the bulkhead is arranged inside the grid structure and is connected with the upper panel and/or the lower panel; the method comprises the steps of grid structure design, plate design and integral check of the floating raft. According to the invention, the net frame structure is applied to the traditional floating raft structure design to form the net frame type box floating raft structure, so that the fusion design of the raft frame structure and the cabin structure and the lightweight design of the cabin raft vibration isolation system can be realized, and the net frame type box floating raft structure has better vibration and noise reduction effects compared with the traditional plate frame type floating raft structure under the same weight.
Description
Technical Field
The invention belongs to the technical field of ship vibration isolation structures, and particularly relates to a net frame type box floating raft structure and a design method thereof.
Background
During the sailing process of the ship, a power system consisting of a plurality of power devices inevitably brings vibration and noise to the main body. Although complete elimination of structure vibration and noise is not possible under the existing conditions, it is necessary to limit the ship vibration to an acceptable range in order to enable the entire system to operate safely and stably.
In recent thirty years, a large number of theoretical and experimental researches are carried out on the vibration reduction and noise reduction aspects of underwater vehicles at home and abroad, the design of a mechanical equipment vibration isolation system is developed from an early single-layer and one-way simple vibration isolation device to the existing multilayer and multidirectional space three-dimensional floating raft vibration isolation device, and the vibration isolation performance is improved to a great extent. The buoyant raft vibration isolation is a novel and complex vibration isolation method, and is mainly used in projects which simultaneously carry out vibration isolation on a plurality of power equipment and have higher requirements on installation environment and vibration isolation effect. The main principle of the floating raft vibration isolation is that a plurality of mechanical devices are installed on the same raft frame through vibration isolators, and the raft frame is connected with a base through the vibration isolators, so that the devices, the raft frame and the base form a multi-degree-of-freedom multi-layer vibration isolation system. The floating raft vibration isolation system is mainly applied to ship vibration isolation engineering, and the vibration isolation performance of the floating raft vibration isolation system is superior to that of a single-layer vibration isolation system and a double-layer vibration isolation system.
Traditional buoyant raft structure generally adopts plane slab posture structural design as buoyant raft vibration isolation device's middle quality, and it only can realize the effect of equipment fixing platform and damping vibration, and function and structural style are single. On the other hand, the realization of traditional buoyant raft vibration isolation mounting damping effect mainly relies on its "quality effect", and its damping effect is directly proportional with the weight of middle raft frame structure, in order to reach better damping effect, often need consume more weight and space resource. Therefore, a new method for designing a raft structure is needed, so that the raft frame structure has more excellent vibration reduction effect while realizing light weight.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a net-frame type box floating raft structure and a design method thereof, aiming at the defects existing in the prior art, wherein the net-frame type box floating raft structure with a three-dimensional space is formed by applying the net-frame structure to the traditional floating raft structure design.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a net frame type box floating raft structure comprises a net frame structure, an upper panel, a lower panel and a bulkhead; the grid structure is a spatial three-dimensional frame structure consisting of horizontal, longitudinal and horizontal plane truss structures; the plane truss structure is an open-web lattice type bending member formed by connecting rod pieces, and each rod piece comprises a chord member and a web member; the upper panel is arranged on the upper surface of the horizontal plane truss at the top, and the lower panel is arranged on the upper surface of the horizontal plane truss at the bottom; the bulkhead is mounted inside the grid structure and is connected to the upper panel and/or the lower panel.
In the scheme, the bulkhead adopts a plane bulkhead consisting of a stiffening material and bulkhead plates.
In the above scheme, the grid structure, the upper panel, the lower panel and the bulkhead are connected in a welding mode.
In the scheme, the net frame type box floating raft structure is used as a ship cabin.
Correspondingly, the invention also provides a design method of the net frame type box body floating raft structure, which comprises the following steps:
s1, designing the grid structure including
S1.1, selecting appropriate materials based on the action of each rod piece on the grid structure;
s1.2, designing a grid structure type based on a vibration isolation design target;
s1.3, designing parameters including rod length, section form and slenderness ratio of the rod piece according to the determined grid structure type;
s1.4, designing a node based on the determined rod piece;
s1.5, designing the load of the plane truss structure according to the actual use environment of the grid structure, wherein the load comprises a permanent load and a variable load; for the plane truss structure, checking the section strength, stability, rigidity and nodes of the plane truss structure based on internal force analysis according to the designed load;
s2, designing the plate material, including
S2.1, selecting proper materials according to the application of the plate and the load borne by the plate, wherein the plate comprises an upper panel, a lower panel and a bulkhead;
s2.2, designing the panel, wherein the maximum bending stress and the deflection value of the panel are designed to be smaller than allowable values in consideration of the weight of equipment on the panel;
s2.3, designing the bulkheads, wherein the design comprises the thickness of the bulkheads, the size design of the stiffening materials and the arrangement and the number of the bulkheads;
s3, checking the floating raft integrally, including
Performing static force check on the whole floating raft, wherein the static force check comprises positive floating state check and inclined state check, and the maximum stress of the structure in the two states is smaller than the yield stress of the material;
vibration isolation check is carried out on the whole buoyant raft, and the vibration isolation capability of the designed net rack buoyant raft in the full frequency band is larger than that of the traditional board frame buoyant raft under the same weight.
In the method, the selection range of the rod piece material and the plate material is as follows: 16Mn steel, Q235, Q345, Q390, Q420 and Q460 steel.
In the method, in step S1.2, the design of the grid structure type includes determining the plane truss structure type, the height of the grid, and the size of the grid; the plane truss structure type comprises a Prader truss, a Wallon truss, a Fenker truss and an arch truss.
In the above method, in step S1.4, the node types include lap K-shape, T-shape, and planar KT-shape; the eccentric position of the joint of the welded branch pipe and the main pipe is avoided as much as possible, and if the eccentric position cannot be avoided, the value of the eccentric position is not more than the limit of the following formula:
e/D (or e/h) is more than or equal to 0.55 and less than or equal to 0.25
Wherein e is eccentricity;
d, the outer diameter of the main pipe of the circular pipe;
h is the section height of the main pipe of the rectangular pipe in the connecting plane;
when a plurality of branch pipes at the nodes of the steel pipe network frame are lapped, the lapped pipes are selected in a certain sequence, and in K-shaped or N-shaped nodes with gaps, the gaps of the branch pipes are not less than the sum of the wall thicknesses of the two branch pipes; in the overlapped K-shaped or N-shaped node, the overlapping rate of the node is more than or equal to 25 percent and less than or equal to O v Less than or equal to 100 percent, and the connecting welding seam between the branch pipes of the lap joint part can reliably transmit the internal force.
In the method, in step S2.3, the thickness of the bulkhead plate and the section modulus of the stiffening material should meet the specification requirements; the arrangement and the number of the bulkheads are divided by the internal space of the floating raft, the longitudinal bulkheads, the transverse bulkheads or the half bulkheads are selected at proper positions to be uniformly arranged, and the number of the bulkheads is reduced as much as possible under the condition of meeting the requirement of strength design.
In the method, in step S3, the overall verification of the raft further includes performing impact resistance verification on the raft structure, and the stress response of the structure under the environmental impact should meet the structural strength requirement.
The invention has the beneficial effects that:
1. the net frame type box body floating raft structure has the following advantages:
1) the integrated design of the raft frame structure and the cabin structure can be realized, the overall rigidity and strength level of the middle part of the raft frame can be effectively improved by utilizing the reinforcing design of the cabin bulkhead stiffening materials, and the light weight design effect of the cabin raft vibration isolation system can be achieved on the basis that the rigidity and strength requirements are met by utilizing the member structure at the periphery;
2) the raft frame structure is not only an installation platform of equipment, but also has cabin functions, the loading capacity of the whole cabin floating raft can be improved, all auxiliary machine systems are conveniently integrally and intensively arranged on the floating raft, and the equipment, pipelines and related auxiliary devices are subjected to vibration isolation through the floating raft, so that the problem of vibration reduction and isolation of the pipeline systems is solved; the upper system of the floating raft realizes fluid exchange in the floating raft as much as possible, so that pipelines connected with the outside can be reduced, and vibration transfer channels between the cabin raft and the boat body can be effectively reduced;
3) the box body floating raft structure can realize more equipment integration installation, and the vibration isolation system has a large mass effect and a more obvious mass effect, and is favorable for improving the low-frequency vibration isolation effect.
2. The design method of the net frame type box floating raft structure has the following advantages:
1) the net frame type box floating raft based on the process design can realize the fusion design of a raft frame structure and a cabin structure and the lightweight design of a cabin raft vibration isolation system, and has better vibration and noise reduction effects compared with the traditional plate frame type floating raft structure under the same weight;
2) can guide the structural design of the floating raft similar to the net rack box body.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic structural view of a net-frame type tank buoyant raft structure of the present invention;
fig. 2 is a flow chart of the method for designing the structure of the net-frame type tank buoyant raft according to the present invention;
FIG. 3 is a schematic view of a type of planar truss structure;
FIG. 4 is a schematic view of a longitudinal planar truss structure in an embodiment of the invention;
FIG. 5 is a schematic view of a transverse planar truss structure in an embodiment of the invention;
fig. 6 is a schematic node diagram of a truss-type tank raft structure according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of the main arrangement of the upper layer device in the embodiment of the present invention;
fig. 8 is a graph comparing the vibration isolation effect of the net-frame type tank raft structure of the embodiment of the invention and the conventional plate-frame type raft.
In the figure: 11. a longitudinal planar truss structure; 12. a transverse planar truss structure; 13. a horizontal planar truss structure; 14. a chord member; 15. a web member; 21. an upper panel; 22. a lower panel; 23. a bulkhead.
Detailed Description
For a more clear understanding of the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
The invention provides a net frame type box floating raft structure which is mainly used for being elastically installed in a cabin section of a ship, and achieves the purposes of impact resistance protection on important equipment and personnel and vibration isolation of the equipment while realizing the functions of an equipment installation platform and the cabin. As shown in fig. 1, the net-framed box raft structure includes a net-framed structure, an upper panel 21, a lower panel 22, and bulkheads 23. The space three-dimensional truss structure comprises a truss structure, a truss structure and a truss structure, wherein the truss structure is a space three-dimensional frame structure consisting of transverse, longitudinal and horizontal plane truss structures; the plane truss structure is a hollow lattice type bending member formed by connecting rod pieces, and the rod pieces comprise chord members 14 and web members 15. The upper face plate 21, lower face plate 22, and bulkheads 23 are plate structures, wherein the upper face plate 21 is mounted to the upper surface of the top horizontal planar truss structure 13, and the lower face plate 22 is mounted to the upper surface of the bottom horizontal planar truss structure 13. The bulkhead 23 is a plane bulkhead composed of stiffening materials and bulkhead plates, the bulkhead 23 is installed inside the grid structure, and the bulkhead plates are connected with the upper panel 21 and/or the lower panel 22. The grid structure, the upper panel 21, the lower panel 22 and the bulkhead 23 are connected by welding.
The design process of the net frame type box floating raft structure is shown in figure 2, and comprises the following steps:
s1 design of net rack structure
S1.1, determining rod material
Based on the function of each member (chord member and web member) in the grid structure, a proper material is selected. The steel material of the net rack rod piece structure is preferably 16Mn steel, Q235, Q345, Q390, Q420 and Q460 steel, and can be selected according to actual needs, and the quality of the steel material respectively conforms to the regulations of the existing national standards GB/T700 of carbon structural steel and GB/T1591 of Low alloy high strength structural steel. In this embodiment, the rod member is made of Q345 steel with a material density of 7.85 × 10 3 kg/m 3 Elastic modulus E2.06X 10 11 N/m 2 The poisson ratio σ is 0.3.
S1.2, design of grid structure
Based on the vibration isolation design target, the grid structure type is designed, including determining the plane truss structure type, the height of the grid and the size of the grid.
According to the stress characteristics and different rod arrangement, the plane truss structure is divided into a Pratt truss, a Warren truss, a Fink truss and an arch truss, and the plane truss structure is shown in figure 3. The structure of the box floating raft is influenced by the arrangement of the ship cabin, the height of the box floating raft is basically determined, and the box floating raft structure comprises an upper panel and a lower panel which are parallel to each other and is of a box-type structure integrally, so that the box floating raft is designed in a rectangular grid structure mode, namely, the box floating raft is designed in a regular Hualun truss mode and a Pratet truss mode. The corresponding mesh size is obtained in combination with the arrangement position of the cabin bulkhead 23 and the grid structure pattern.
S1.3, determining rod piece parameters
According to the determined grid structure type, the rod pieces (chord members and web members) are designed, and the proper rod length, section form, slenderness ratio and the like are selected. The steel pipe structure can be a circular pipe or rectangular pipe structure according to the stress condition of the component, the manufacturing and mounting conditions, the appearance requirement, the economical efficiency and other specific conditions, and can also be mixed with two kinds of steel pipes. When the two-way connecting rod is used in a mixed mode, the chord members are rectangular tubes, and the web members are circular tubes. The chord members can also adopt H-shaped steel, and the web members can adopt rectangular pipes or round pipes. The calculated length and the allowable slenderness ratio of the rod member should satisfy the requirements of the relevant regulations. The node design of the structure needs to be reasonable in stress and accords with actual economic benefits.
In this embodiment, the concrete size is confirmed by actual demand to the member all chooses the rectangular pipe rack cross-section for use. The calculated length of the rods of the net rack is set to be smaller than the geometric length of the rods, the web members are designed in a single-layer web member mode (namely, only one layer of net rack) and the allowable slenderness ratio of the rods is considered like the chord members.
S1.4, node design
And designing nodes based on the determined rod pieces, wherein the node types comprise lap joint K shapes, T shapes, plane KT shapes and the like.
For the joint design of the embodiment, attention should be paid to the requirement of the directly welded steel pipe joint, and the connecting part of the branch pipe and the main pipe is prevented from being eccentric as much as possible. If eccentricity cannot be avoided, the value should not exceed the limit of the following formula:
e/D (or e/h) is more than or equal to 0.55 and less than or equal to 0.25
Wherein e is eccentricity;
d, the outer diameter of the main pipe of the circular pipe;
h is the height of the section of the main pipe of the rectangular pipe in the connecting plane.
When a plurality of branch pipes at the nodes of the steel pipe network frame are lapped, the lapped pipes are selected in a certain sequence, and in the K-shaped or N-shaped nodes with gaps, the gaps of the branch pipes are not less than the sum of the wall thicknesses of the two branch pipes. In the overlapped K-shaped or N-shaped node, if the overlapping rate is more than or equal to 25 percent and less than or equal to O v Less than or equal to 100 percent, and the connecting welding seam between the branch pipes of the lap joint part can reliably transmit the internal force.
Combining the above factors and the difference of the horizontal and vertical plane truss structures of the floating raft, the two-way plane truss structures are respectively designed, the structural forms of the preliminarily designed vertical plane truss structure 13 and the horizontal plane truss structure 12 are respectively shown in fig. 4 and 5, and the node types contained in the preliminarily designed vertical plane truss structure and the preliminarily designed horizontal plane truss structure are overlapped K-shaped, T-shaped and plane KT-shaped, which are respectively No. 1, 2 and 3 nodes in fig. 6. The horizontal grid structure is a strong and weak material which is jointed, and the design can be designed by referring to a deck structure of 'Steel sea vessel entry and construction Standard' of China classification society.
S1.5, determining design load
For the rod piece design, for the preliminarily designed planar net rack (namely, a planar truss structure), the section strength, stability, rigidity and nodes of the net rack rod piece need to meet the calculation requirements in the standard, and when the requirements are checked, the planar net rack load design is carried out. Under static conditions, the net frame bears the weight of the upper panel 21 and the equipment and personnel on the upper panel 21. Therefore, the dead load of the flat net rack needs to be designed according to the weight of the upper panel 21 and the equipment and personnel on the upper panel 21. The weight statistics of the equipment and personnel on the top panel 21 are shown in table 1, the main equipment layout of the top layer is shown in fig. 7 (equipment E is numerous and scattered, the mass is much smaller than other structures, and is ignored in fig. 7) in combination with the weight of the top panel 21 as the load input, wherein the loading effect of the weight of the top panel 21 and equipment is denoted as constant load, and the loading effect of the weight of personnel is denoted as live load. Assuming that the weight is borne by the lattice structure in the raft frame, and simplifying the weight into equivalent load acting on the nodes of the upper chords of the lattice structure.
Table 1 upper layer preliminary design equipment and personnel weight table
| Device name | Weight (kg) | Number of | Total kg |
| Person(s) | 75 | 20 | 1500 |
| Device A | 200 | 5 | 1000 |
| Device B | 500 | 1 | 500 |
| Device C | 500 | 1 | 500 |
| Device D | 200 | 5 | 1000 |
| |
23 | 14 | 322 |
| Apparatus F | 180 | 3 | 540 |
| Device G | 208 | 3 | 624 |
| Plant H | 178 | 2 | 356 |
| Device I | 186 | 2 | 372 |
The constant load borne by the grid structure is 11.024t, and the live load is 1.5 t. Considering the difference between the test value and the actual value of the load and the material performance, the safety factor of the general building structure design is 1.5 when the safety factor is K, but considering that the raft frame structure is different from the general building structure, the safety factor is 2.0 when checking. The loads on each side of the planar lattice structure are shown in table 2 below.
TABLE 2 load of single side grid structure (unit: kN)
| Constant load | Live load | Kx constant load | Kx live load | |
| Longitudinal plane net rack | 36.00 | 4.32 | 72.00 | 8.64 |
| Transverse plane net rack | 26.48 | 3.18 | 52.96 | 6.35 |
Checking the stress of the planar net rack:
after the design load is determined, the cross section strength, stability, rigidity and nodes of the net rack rod piece are calculated, checked and analyzed.
For the axial tension member, when the plates forming the cross section at the end connection and the middle splicing part are directly transmitted by the connecting piece, the strength of the cross section is calculated to meet the following regulations:
in addition to the high strength bolt friction type joint, the sectional strength thereof should be calculated using the following equations (1) and (2):
yield of the cross section of the hair:
fracture of the clear section:
in the formula: n-design value of tension at calculated section (N)
f-design tensile Strength (N/mm) of Steel 2 )
A-area of the cross-section of the bristles of the component (mm) 2 )
A n The net cross-sectional area of the member, when the plurality of cross-sections of the member are provided with holes, is the most unfavourable cross-section (mm) 2 )
f u Minimum design tensile (N/mm) of steel 2 )
For the axial compression member, when the plates forming the cross section at the end connection part and the middle splicing part are directly transmitted with force by the connecting piece, the strength of the cross section is calculated according to the formula (1), and the member containing the virtual hole is required to be calculated according to the formula (2) on the cross section of the hole center. The checking standard mainly calculates the stress component of the axle center according to the seventh chapter of the national standard, namely design Standard of Steel Structure (GB 50017-2017).
The stability of the components such as the chord member, the web member and the like in the net rack is checked according to the national standard 'steel structure design standard' (GB 50017-2017) and the components are stressed according to the axis. The initial defects of the component are considered in the specification formula, and the section is allowed to have certain plasticity development. In addition to a solid web member in which the post-yield strength can be considered, the axial center pressed member is subjected to stability calculation using equation (3):
in the formula: n is the axial stress of the rod;
A f -rod cross-sectional area;
In the design of a planar net rack, the structural rigidity is ensured by adopting a method of limiting the length-to-thickness ratio of a component, and according to the design standard of a steel structure (GB 50017-2017), the component adopts a formula (4) to calculate the rigidity:
in the formula: l-calculating the length of the rod;
r-effective radius of gyration of the bar;
[ lambda ] -the rod tolerance slenderness ratio.
The safety of the node is mainly determined by the strength and rigidity of the node, and the node is prevented from failing due to cracking of connecting parts such as welding seams and bolts or redistribution of internal force of the structure caused by excessive deformation of the node. There are different design checking requirements for different node formats. During checking, the requirement that the axial force of a component is not greater than a bearing capacity design value is met, then the node can be checked according to the design requirement in a node design part, and calculation and checking can be carried out by referring to a formula specified in chapters 12 and 13 in Steel Structure design Standard (GB 50017-2017) during checking.
S2 structural design of sheet material
S2.1, determining the plate material
For the design of the plate structure, 16Mn steel, Q235, Q345, Q390, Q420 and Q460 steel are preferably adopted, and can be selected according to actual needs, and the quality of the steel respectively conforms to the regulations of the existing national standard GB/T700 of carbon structural steel and GB/T1591 of Low-alloy high-strength structural steel. For the structure bearing dynamic loads such as vibration or impact, the standard requirements of GB 712-. The example selected Q345 steel for further analysis.
S2.2, Panel design
When the panel is designed, the design is carried out according to the space size of the structure, on one hand, the whole weight control of the floating raft is required to be met, and on the other hand, the design requirement under the load action is required to be met. During design, the maximum bending stress and the maximum deflection value of the panel under the action of design load need to be calculated, so that the requirement of being smaller than the design value is met. The calculation model during calculation can be simplified into an equal-thickness rectangular plate with simply supported four sides and is uniformly loaded. The maximum bending stress value is calculated according to the formula (5):
the formula is as follows: α — the calculated coefficient;
b-Panel Width;
t is the panel thickness;
q-designing uniform load;
[ sigma ] -allowable stress value.
The maximum deflection is calculated according to the formula (6):
in the formula: beta-coefficient of calculation;
b-panel width;
t is the panel thickness;
e-modulus of elasticity;
q-designing uniform load;
[ omega ] -deflection control value.
The thickness of the upper and lower panels is calculated to be 12 mm.
S2.3 bulkhead design
The bulkhead of the net rack box body floating raft structure is mainly designed by adopting a plane bulkhead consisting of stiffening materials and bulkhead plates, and the bulkhead in the raft structure is mainly used for separating cabins or is arranged due to the strength requirement, so that a watertight bulkhead is not needed. The arrangement and the number of the bulkheads are determined according to the internal space division of the raft frame, and the vertical bulkheads, the transverse bulkheads or the half bulkheads are selected at proper positions to achieve uniform arrangement. The number of bulkheads is minimized while meeting the strength design requirements. The thickness of the bulkhead plate and the size of the strengthening material can be designed according to the following calculation requirements by referring to the steel sea vessel entry and construction specifications:
the bulkhead thickness t should not be less than the value calculated according to equation (7):
in the formula: K. c-coefficient, selected according to Table 3;
s-the space between the reinforcing materials, m;
h is the vertical distance from the lower edge of the bulkhead to the top end of the bulkhead (0.5 m is additionally added to the deep bulkhead), m;
TABLE 3 values of coefficient K, c
| Bulkhead kind | Anti-collision bulkhead | Storage compartment bulkhead | Deep cabin wall |
| K | 4.0 | 3.2 | 4.2 |
| c | 0.5 | 0 | 1.0 |
The bulkhead stiffener should be generally vertically arranged and its section modulus W should be not less than the value calculated according to the formula (8)
W＝Kshl 2 cm 3 (8)
In the formula: k is the coefficient, selected according to Table 4;
s is the spacing between the stiffening materials, m;
h is the vertical distance m from the middle point of the strengthening material to the top end of the bulkhead (0.5 mm is added to the deep bulkhead);
l is the span of the stiffening material, m, and the length of the stiffening material including the toggle plate is taken.
TABLE 4 planar bulkhead stiffener coefficient K value
The resulting bulkhead design is shown in fig. 1, with bulkheads located intermediate the longitudinal and transverse directions of the integrated raft and a short transverse bulkhead below the equipment F and G.
And combining the designed planar grid structure with the plate frame structure to form a typical net frame type box floating raft structure. The thickness of the upper panel and the lower panel is 12mm, the whole weight of the net frame type floating raft is 23.84t, and the weight is almost equal to that of the frame type floating raft (23.95 t).
S3, checking and calculating the whole structure of the net frame type box floating raft
The method comprises the steps of performing static check on the whole floating raft, wherein the static check comprises check in a positive floating state and check in an inclined state, and the maximum stress of the structure in the two states is smaller than the yield stress of a material; vibration isolation check is carried out on the whole buoyant raft, and the vibration isolation capability of the designed net rack buoyant raft in the full frequency band is larger than that of the traditional board frame buoyant raft under the same weight.
Taking the positive floating state as an example, the static checking, the inclination and the swing quasi-static analysis of the whole raft frame and the upper and lower panels are carried out. And analyzing whether the static response of the designed net frame type box body floating raft and the traditional frame type floating raft in the positive floating state can meet the design requirement. The method specifically comprises the steps of adopting fixed constraint boundary conditions on two sides of the lower boundary of the whole model and limiting the degree of freedom of the model in six directions. In the calculation, the gravity field applied to the model is calculated by only considering the weight of the equipment and the raft frame (gravity acceleration Gy is 9810 mm/s) 2 ). Corresponding calculation under positive superficial state is respectively carried out net rack formula box buoyant raft and traditional grillage formula buoyant raft, and the computational result is referred to table 5, and final result shows that the static response performance of net rack formula buoyant raft is all superior to traditional grillage formula buoyant raft under positive superficial state.
And (4) carrying out vibration isolation check analysis on the whole structure of the net frame type box floating raft according to the structural design process of the net frame type box floating raft. And (3) adopting a finite element model established by ABAQUS, and importing the finite element model into VA one calculation software to finally obtain calculation results under different frequency bands, which is shown in figure 8. Finally, vibration level drop curves of the two structures show that the vibration isolation effect of the net frame type floating raft is superior to that of the plate frame type floating raft.
TABLE 5 maximum stress and maximum displacement value table for each structure of the raft in the positive floating state
When necessary, dynamic impact resistance check (namely dynamic check) needs to be carried out on the floating raft structure, and the stress response of the structure under the action of environmental impact meets the requirement on the structural strength.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A net frame type box floating raft structure is characterized by comprising a net frame structure, an upper panel, a lower panel and a bulkhead; the space truss structure is a space three-dimensional frame structure consisting of horizontal, longitudinal and horizontal plane truss structures; the plane truss structure is an open-web lattice type bending member formed by connecting rod pieces, and the rod pieces comprise chord members and web members; the upper panel is arranged on the upper surface of the horizontal plane truss at the top, and the lower panel is arranged on the upper surface of the horizontal plane truss at the bottom; the bulkhead is mounted inside the grid structure and is connected to the upper panel and/or the lower panel.
2. The lattice-framed box raft structure of claim 1, wherein the bulkheads are planar bulkheads comprised of stiffeners and bulkhead plates.
3. The truss-type box raft structure of claim 1 wherein the truss structure, the upper panel, the lower panel, and the bulkheads are connected by welding.
4. The net-framed box raft structure of claim 1, wherein the net-framed box raft structure doubles as a boat cabin.
5. A method of designing a net-framed tank raft structure as claimed in claim 1, comprising the steps of:
s1, designing a grid structure, including
S1.1, selecting appropriate materials based on the action of each rod piece on the grid structure;
s1.2, designing a grid structure type based on a vibration isolation design target;
s1.3, designing parameters including rod length, section form and slenderness ratio of the rod piece according to the determined grid structure type;
s1.4, designing a node based on the determined rod piece;
s1.5, designing the load of the plane truss structure according to the actual use environment of the grid structure, wherein the load comprises a permanent load and a variable load; for the plane truss structure, checking the section strength, stability, rigidity and node of the plane truss structure based on internal force analysis according to the designed load;
s2, designing the plate material including
S2.1, selecting proper materials according to the application of the plate and the load borne by the plate, wherein the plate comprises an upper panel, a lower panel and a bulkhead;
s2.2, designing the panel, wherein the maximum bending stress and the deflection value of the panel are designed to be smaller than allowable values in consideration of the weight of equipment on the panel;
s2.3, designing the bulkhead, wherein the design comprises the thickness of the bulkhead plate, the size design of the stiffening materials and the arrangement and number of the bulkhead;
s3, checking the floating raft integrally, including
Performing static check on the whole floating raft, wherein the static check comprises check of a positive floating state and check of an inclined state, and the maximum stress of the structure in the two states is smaller than the yield stress of the material;
vibration isolation check is carried out on the whole buoyant raft, and the vibration isolation capability of the designed net rack buoyant raft in the full frequency band is larger than that of the traditional board frame buoyant raft under the same weight.
6. The method of designing a net-framed tank raft structure of claim 5, wherein the selection of the rod material and the plate material is in the range of: 16Mn steel, Q235, Q345, Q390, Q420 and Q460 steel.
7. The method of claim 5, wherein in step S1.2, the designing of the truss structure type includes determining a planar truss structure type, a truss height, and a mesh size; the plane truss structure type comprises a planter truss, a Wallon truss, a Fenker truss and an arched truss.
8. A method for designing a net-frame-type tank raft structure according to claim 5, wherein in step S1.4, the node types include an overlap K-shape, a T-shape and a plane KT-shape; the welded junction between the branch pipe and the main pipe is prevented from being eccentric as much as possible, and if the eccentricity cannot be avoided, the value of the eccentricity is not more than the limit of the following formula:
e/D (or e/h) is more than or equal to 0.55 and less than or equal to 0.25
Wherein e is eccentricity;
d, the outer diameter of the main pipe of the circular pipe;
h is the height of the section of the rectangular pipe main pipe in the connecting plane;
when a plurality of branch pipes at the nodes of the steel pipe network frame are lapped, the lapped pipes are selected in a certain sequence, and in K-shaped or N-shaped nodes with gaps, the gaps of the branch pipes are not less than the sum of the wall thicknesses of the two branch pipes; in the overlapped K-shaped or N-shaped node, the overlapping rate of the node is more than or equal to 25 percent and less than or equal to O v Less than or equal to 100 percent, and the connecting welding seam between the branch pipes of the lap joint part can reliably transmit the internal force.
9. The method of claim 5, wherein in step S2.3, the thickness of the bulkhead plate and the section modulus of the stiffening material are in accordance with the specification; the arrangement and the number of the bulkheads are divided by the internal space of the floating raft, the longitudinal bulkheads, the transverse bulkheads or the half bulkheads are selected at proper positions to be uniformly arranged, and the number of the bulkheads is reduced as much as possible under the condition of meeting the requirement of strength design.
10. The method of claim 5, wherein in step S3, the integral verification of the raft further comprises performing anti-impact verification on the raft structure, and the stress response of the structure under the effect of environmental impact should meet the structural strength requirement.
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| CN115822224A (en) * | 2022-12-03 | 2023-03-21 | 江苏速捷模架科技有限公司 | Frame beam unit of enclosure system construction platform module |
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