CN-121976508-A - Spherical shell enveloping type space connection structure for X-shaped steel pipe nodes

CN121976508ACN 121976508 ACN121976508 ACN 121976508ACN-121976508-A

Abstract

The invention discloses a spherical shell enveloping type space connection structure for an X-shaped steel pipe node, wherein an eccentric spherical shell enveloping body with continuous three-dimensional curvature is arranged at the outer side of a intersecting area of a main pipe section and an inclined strut section, the spherical shell enveloping body adopts a thickness control function based on a spherical angle, so that the shell forms directional reinforcement in the direction of the inclined strut stress, and the other directions are continuously graded to obtain smooth local rigidity distribution. Through the spherical shell force flow diffusion correction function, the node equivalent bending moment and the equivalent membrane force expression, a calculation model of node hot spot stress, stress gradient and fatigue equivalent stress range can be established, and accurate characterization of node stress behavior is realized. The node structure can obviously reduce the hot spot stress of the intersecting area of the diagonal brace and the main pipe, improve the diffusion capacity of force flow on the shell, and improve the local stress gradient of the node, thereby improving the fatigue life and the safety of the whole structure of the X-shaped node of the offshore wind power jacket, and being suitable for the engineering application of steel pipe nodes with various scales.

Inventors

LI TAO
WANG XUEFENG
TANG CAN
Wu Zehou
WANG GANG
Gao Daifan

Assignees

长江三峡集团江苏能源投资有限公司
中国电建集团华东勘测设计研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20251229

Claims (10)

1. The spherical shell enveloping type space connection structure for the X-shaped steel pipe node is characterized by comprising a main pipe section, two symmetrically arranged inclined strut sections and a spherical shell enveloping body positioned at the outer side of an intersection area of the main pipe section and the inclined strut sections, wherein the spherical shell enveloping body is an eccentric spherical shell with continuous three-dimensional curvature, the spherical shell enveloping body is respectively connected with the main pipe section and the inclined strut sections through space transition curved surfaces and meets at least C 1 geometric continuity conditions, so that a continuous curvature three-dimensional shell node is formed in an intersecting area between the main pipe and the inclined strut, thereby realizing natural diffusion of force flow in the node on a spherical shell surface and reducing hot spot stress, and the spherical shell enveloping body comprises the following components: (1) The spherical shell envelope is determined by a spherical shell radius R, a spherical center offset e and a thickness distribution function t s (theta, alpha); (2) The main curvature and the auxiliary curvature of the outer surface of the spherical shell continuously change along the spherical angle direction, and the curvature change rate constraint is satisfied; (3) The space transition curved surface keeps consistent with the outer wall of the main pipe and the outer wall of the diagonal brace in terms of normal displacement and first derivative thereof; (4) The local stress of the node is transferred according to the membrane-bending coupling characteristic of the envelope of the spherical shell.
2. The spatial connection according to claim 1, characterized in that the thickness distribution of the spherical envelope body satisfies a continuous functional form based on spherical angle, the thickness t s (θ, α) being given by: wherein t 0 is the reference thickness of the spherical shell, alpha 1 ,α 2, α 3 is the thickness adjustment coefficient, theta is the spherical polar angle, Is the circumferential angle of the spherical surface, For the circumferential angle that the bracing direction is located, the rate of change in thickness direction satisfies: the local rigidity of the node is smoothly changed in the space direction; The spherical center of the spherical shell enveloping body is offset along the diagonal bracing direction relative to the axis of the main pipe section, wherein e is the offset distance of the spherical center along the diagonal bracing direction, R is the spherical shell reference radius, and the offset ratio is the offset distance of the spherical center along the diagonal bracing direction The method is used for controlling the curvature diffusion capacity of the spherical shell in the direction of the diagonal bracing, and e is 0.1-0.4 times of the reference radius R of the spherical shell so as to form the diffusion curvature consistent with the stress direction of the diagonal bracing, so that the bending-film coupling bearing capacity of the node in the direction of the diagonal bracing is improved; the transition curved surface between the main pipe section and the spherical shell enveloping body adopts a conductive spline function structure, the normal displacement X (s, l) of the transition curved surface keeps continuous with the outer surface of the spherical shell at the outer wall position of the main pipe, X(s,l)=(1-s)X tube (l)+sX shell (l) And the consistency condition of the normal gradient is satisfied, So as to avoid the occurrence of abrupt wall thickness change or curvature fold line on the outer surface of the node, wherein s is a normalized parameter along the transition direction, l is a curved surface parameter along the bus direction of the main pipe or the spherical shell, X tube (l) is a normal displacement function of the outer wall of the main pipe, and X shell (l) is a normal displacement function of the outer surface of the spherical shell; And inclined support side curved surface transition sections are respectively arranged between the two inclined support sections and the spherical shell enveloping body, the local main curvature direction of the transition sections is consistent with the main curvature of the outer wall of the inclined support, and the thickness in the transition section continuously extends towards the spherical shell enveloping body so as to reduce the hot spot stress of the inclined support splicing area.
3. The spatial connection structure according to claim 1, wherein the spherical shell envelope of the present invention uses a spherical shell force flow spread correction function F d (λ) in the node stress evaluation, which is in the form of: Wherein the method comprises the steps of The non-dimensional ratio of the projection width of the diagonal brace to the diameter of the spherical shell is used for representing the diffusion capacity of the input bending moment of the diagonal brace to the spherical shell, a s is the projection width of the diagonal brace on the outer wall of the main pipe, t s is the local thickness of the spherical shell, and a 1 ,a 2 is a fitting coefficient for jointly controlling the diffusion degree of the spherical shell to the input bending moment of the diagonal brace.
4. The space connection structure according to claim 1, wherein the node equivalent bending moment M Shell is represented by the following formula: Wherein M s is the input bending moment of the end part of the diagonal brace, t s is the effective thickness of the spherical shell, R is the radius of the spherical shell, and b 1 ,b 2 is the dimensionless weight coefficient of the thickness-curvature coupling effect.
5. The spatial connection structure according to claim 1, wherein the node equivalent membrane force n eq satisfies the following relationship: Wherein D m is the average diameter of the main pipe, a s is the projection width of the diagonal brace on the outer wall of the main pipe, t s is the effective thickness of the spherical shell, and c 1 、c 2 、c 3 is the dimensionless node equivalent stress correction coefficient, which are all used for determining the distribution characteristic of the node in-plane membranous force N eq .
6. The spatial connection structure according to claim 1, wherein the node hotspot equivalent stress σ eq is represented by the following formula: σ eq ＝K s ·N eq K s (α)＝β 1 +β 2 α+β 3 α 2 , where K s is the hotspot stress amplification, For the shell thickness ratio, β 1 ,β 2 and β 3 are the quadratic regression coefficients of the hotspot stress amplification coefficient to the shell thickness ratio α=t s /t 0 , N eq is the node equivalent film force, and σ eq is the node hotspot equivalent stress.
7. The spatial connection structure according to claim 1, wherein the fatigue equivalent stress range Δs of the node is given by: The method is used for evaluating fatigue performance of the node under the action of long-term cyclic load, wherein sigma eq is node hot spot equivalent stress, a s is projection width of the diagonal brace on the outer wall of the main pipe, D m is main pipe average diameter, delta S is fatigue equivalent stress range of the node under the cyclic load, and gamma is dimensionless geometric abduction fatigue correction coefficient.
8. The spatial connection structure according to claim 1, wherein the node surface stress gradient G is defined by the following index: wherein s is an arc length parameter along the direction of the curved surface of the node, θ is a spherical polar angle, and R is a spherical shell radius, which are used for describing the change characteristics of the stress gradient G of the surface of the node together.
9. The space connection structure according to claim 1, wherein the insertion angle range of the node diagonal brace is adjustable within 25-65 degrees, and the eccentric amount, the thickness distribution function and the space transition curved surface parameters of the spherical shell envelope are automatically matched with the diagonal brace angle, so that the node maintains the low stress gradient and the continuous curvature characteristic.
10. The space connection structure according to claim 1, wherein the structure enables the node hot spot stress to be significantly reduced and the node fatigue life to be improved by the synergistic effect of three-dimensional curvature continuity of the spherical shell envelope, thickness gradient control, space transition curved surface fairing connection and diagonal brace bending-film coupling force transmission mechanism.

Description

Spherical shell enveloping type space connection structure for X-shaped steel pipe nodes Technical Field The invention relates to the field of offshore wind power structures and ocean engineering steel pipe nodes, in particular to a spherical shell enveloping type space connection structure applied to a jacket X-shaped steel pipe node. Background The offshore wind power jacket structure is composed of members such as a main pipe, an inclined strut, a horizontal strut and the like, and the node area is used as a key path for force flow transmission and is the part which is most prone to fatigue damage in the whole structure. The nodes bear the cyclic action of high frequency and low frequency for a long time under the random combined load of wind wave and current, and the weld toe area between the main pipe and the diagonal brace is particularly easy to generate high-level hot spot stress, so that the fatigue life and service reliability of the wind turbine generator are directly determined by the construction mode of the nodes. The traditional Y-shaped or K-shaped node commonly adopts a mode of directly welding the intersecting lines of the pipes, and because the geometric relationship determines that two round pipes are difficult to form natural continuous curved surfaces in space, unavoidable curvature mutation exists on the outer surface of the node, so that local stress lines are extruded, broken lines and densely gathered near weld toes, and obvious secondary bending effect is formed. The stress concentration is not caused by a single load, but caused by the mismatch of the geometrical characteristics of the nodes and the force flow path, and the inherent stress concentration caused by geometrical abrupt change always exists no matter how the external load changes and becomes a key control factor of jacket fatigue. In order to reduce concentrated stress, common measures in engineering include locally thickening the ends of the main pipe and the diagonal bracing, welding triangular or sector stiffening plates outside the joint area of the joints, increasing toe transition fillets, and improving local rigidity by using a plugboard stiffening or internal ribbed form. However, these compensation methods often only strengthen local weak areas, but cannot change the unfavorable geometric characteristics of the node itself in the whole physical and fluidic organization manner, and the thickness abrupt change or stiffening rib boundary still introduces new rigidity abrupt changes, thereby leading to new stress concentration areas. In addition, such nodes are often accompanied by large welding effort and manufacturing complexity, and the fatigue performance is further affected by welding residual stress, quality control of the plate thickness transition region, and defect risk of the inner undetectable region. With the rapid development of the offshore wind turbine generator system to a large-capacity and deep water area, the jacket structure is increased in size, the transmission bending moment is increased, the cyclic stress is increased, and the improvement mode of the traditional node based on linear thickness compensation or local stiffening is difficult to meet the higher fatigue requirement under the new working condition. Accordingly, there is a need for a structural style that improves force flow spreading patterns from a geometric standpoint, creates a continuous curvature on the outer surface of the node and reduces abrupt wall thickness changes, enabling the node region to more naturally transmit force flow in three dimensions, reduce secondary stresses, and improve fatigue sensitivity. Disclosure of Invention The invention aims to provide a spherical shell enveloping type space connection structure for an X-shaped steel pipe node. The three-dimensional continuous curvature, continuous rigidity distribution and natural force flow diffusion capability are provided, and a mathematical model and an analytical formula which can be used for node stress analysis and fatigue evaluation are further provided. The invention replaces curvature fracture area near intersecting line by constructing spherical shell enveloping body, solves inherent defect of traditional intersecting point from two layers of geometry and mechanics, improves integral stress performance of node and prolongs fatigue life obviously. In order to achieve the above purpose, the present invention proposes the following technical scheme: A spherical shell enveloping type space connection structure for an X-shaped steel pipe node is characterized by comprising a main pipe section, two symmetrically arranged inclined strut sections and a spherical shell enveloping body positioned outside a junction area of the main pipe and the inclined strut, wherein the spherical shell enveloping body is an eccentric spherical shell with continuous three-dimensional curvature, the spherical shell enveloping body is respectively connected with the main pipe s