Ultimate Bearing Capacity Assessment of Hull Girder With Asymmetric Cross Section

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Chenfeng Li ◽  
Peng Fu ◽  
Huilong Ren ◽  
Weijun Xu ◽  
C. Guedes Soares
Keyword(s):  
Cross Section ◽  
Structural Integrity ◽  
Neutral Axis ◽  
Bending Moments ◽  
Hull Girder ◽  
Horizontal Wave ◽  
Asymmetric Load ◽  
Vector Equilibrium ◽  
Error Method ◽  
Force Equilibrium

The objective of this study is to investigate the variation of neutral axis of ship hull girder due to asymmetric geometry or asymmetric load, and its influence on the ultimate strength (ULS) of hull girder. In order to account for asymmetric geometries and loads of hull girders, the force equilibrium and force-vector equilibrium criteria together with a minimum convergence factors (error) method are employed to determine the translation and rotation of neutral axis plane (NAP) of symmetric or asymmetric hull cross section in the application of Smith's method at each step of curvature of the hull girder. The ULSs of Dow's 1/3 frigate model with three predefined structural integrity states, one intact and two damaged, respectively, is investigated by the improved Smith's method (ISM) for a range of variation of heeling angles. The influence of asymmetric geometry and load on the motion of NAP and on the ULS are analyzed and discussed. The results show that the improved iteration strategy together with the minimum convergence factors (error) method is efficient and more accurate in searching the translation and rotation of NAP. Finally, the envelope curves of the bending moments in the three predefined integrity states are obtained, which can be used for assessing ULS of hull girders under combined vertical and horizontal wave bending moments.

Ultimate Bearing Capacity Assessment of Hull Girder With Asymmetric Cross-Section

2017 ◽  
Author(s):  
ChenFeng Li ◽  
Peng Fu ◽  
HuiLong Ren ◽  
WeiJun Xu ◽  
C. Guedes Soares
Keyword(s):  
Ultimate Strength ◽  
Cross Section ◽  
Structural Integrity ◽  
Neutral Axis ◽  
Bending Moments ◽  
Hull Girder ◽  
Horizontal Wave ◽  
Asymmetric Load ◽  
Vector Equilibrium ◽  
Error Method

The objective of this study is to investigate the variation of neutral axis of ship hull girder due to asymmetric geometry or asymmetric load, and its influence on the ultimate strength of hull girder. In order to account for asymmetric geometries and loads of hull girders, the force equilibrium and force-vector equilibrium criteria together with a minimum convergence factors (error) method, are employed to determine the translation and rotation of neutral axis plane of symmetric or asymmetric hull cross-section in the application of Smith’s method at each step of curvature of the hull girder. The ultimate strengths of Dow’s 1/3 frigate model with three predefined structural integrity states, one intact and two damaged respectively, are investigated by the improved Smith’s method for a range of variation of heeling angles. The influence of asymmetric geometry and load on the motion of neutral axis plane and on the ultimate strength are analyzed and discussed. The results show that the improved iteration strategy together with the MCFM is self-adapting and more accurate in searching the translation and rotation of neutral axis plane. Finally, the envelope curves of the bending moments in the three predefined integrity states are obtained, which can be used for assessing ultimate strength of hull girders under combined vertical and horizontal wave bending moments.

A PSO-Based Method for Tracing the Motion of Neutral Axis Plane of Asymmetric Hull Cross-Sections and its Application

2018 ◽  
Author(s):  
Chenfeng Li ◽  
Chao Gao ◽  
Xueqian Zhou ◽  
Sen Dong ◽  
Peng Fu ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
International Association ◽  
Random Search ◽  
Two Dimensions ◽  
Neutral Axis ◽  
Force Vector ◽  
Hull Girder ◽  
Vector Equilibrium ◽  
Force Equilibrium

The Smith’s method is stipulated by the International Association of Classification Societies in the Common Structure Rules as a standard method for estimating ultimate/residual strength of hull girder in both intact and damaged conditions. However, for the latter case where the effective hull cross-section is asymmetric and the neutral axis of damaged cross-section not only translates but also rotates, the additional force vector equilibrium also needs to be applied so as to determine the neutral axis plane. The commonly adopted iterative methods for the two-force-equilibrium problem do not always converge for the desired accuracy. This paper proposes a Particle Swarm Optimization based iteration method to trace the motion of the neutral axis plane of asymmetric cross sections. The translation and rotation of the neutral axis are taken as the two dimensions of particles in the model, and the force equilibrium error and the force vector equilibrium error are the objective functions. The neutral axis is determined by performing a random search within the entire range of possible position of neutral axis. The proposed method has been implemented and validated for the case of the DOW’s 1/3 frigate model, the analysis of efficiency and accuracy shows that the method performs in general better than traditional ones.

Analysis of Thermal Stratification and Fatigue Stress for Pressurizer Surge Line

2010 ◽  
Author(s):  
Xiaofei Yu ◽  
Yixiong Zhang
Keyword(s):  
Cross Section ◽  
Thermal Stratification ◽  
Thermal Stresses ◽  
Structural Integrity ◽  
Bending Moments ◽  
One Dimensional ◽  
Pipe System ◽  
Pipe Cross Section ◽  
Fatigue Stress ◽  
Surge Line

Thermal stratification of pressurizer surge line induced by the inside fluid brings on global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to confirm the structural integrity of pressurizer surge line affected by thermal stratification, this paper theoretically establishes thermal stratified transient and studies the calculation method of thermal stratified stress. A costly three-dimensional computation is simplified into a combined 1D/2D technique. This technique uses a pipe cross-section for computation of local thermal stresses and represents the whole surge line with one-dimensional pipe elements. The 2D pipe cross-section model is used to compute elastic thermal stresses in plane strain condition. Symmetry allows half the cross-section to be considered. The one-dimensional pipe elements model gives the global bending moments including effects of usual thermal expansion and thermal stratification of each model nodes. This combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line in this paper, using computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor are obtained. The stress and fatigue intensity of the surge line tallies with the correlative criterion.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

scholarly journals THE ERROR METHOD IN THE ORGANIZATION OF STUDYING THE TOPIC «THE CROSS SECTION OF THE POLYHEDRONS»

2021 ◽  
Vol 73 (1) ◽  
pp. 56-61
Author(s):  
B.V. Rabinovich ◽  
◽  
Е.А. Tuyakov ◽  
K.D. Mikailova ◽  
◽  
...  
Keyword(s):  
High School ◽  
Collaborative Learning ◽  
Cross Section ◽  
Interactive Methods ◽  
Main Task ◽  
Teaching Techniques ◽  
Interactive Teaching ◽  
Teaching Geometry ◽  
The Cross ◽  
Error Method

The main task of the school today is not just to equip students with a certain set of knowledge, skills, and abilities, but also to form their ability to learn, work in a group. Based on the above, it is advisable to use interactive teaching methods in math lessons. One of the most popular strategies for interactive learning is collaborative learning. The article discusses interactive teaching techniques and their features in teaching geometry in high school. Given examples of the application of the «error method» in the study of the topic «The cross-section of the polyhedrons» are given. It is shown that, when discussing erroneous decisions in collaborative learning, students acquire the skills to solve such problems. The article fills in one of the gaps that exist in the methodological literature on the description of interactive methods of teaching geometry in high school.

CALCULATION OF EFFORTS RIPS FOUNDATION BOLTS IN THE BCALCULATION OF EFFORTS RIPS FOUNDATION BOLTS IN THE BASES OF CENTRAL AND ECCENTRIC COMPRESSION COLUMNASES OF CENTRAL AND ECCENTRIC COMPRESSION COLUMN

2021 ◽  
Vol 295 (2) ◽  
pp. 32-36
Author(s):  
A.E. Svyatoshenko ◽  
◽  
Keyword(s):  
Cross Section ◽  
Software Package ◽  
Calculation Model ◽  
Neutral Axis ◽  
Continuous Section ◽  
Eccentric Compression ◽  
Engineering Technique ◽  
Section Shape ◽  
Longitudinal Bending ◽  
The Stability

An engineering technique for calculating the tearing forces in the foundation bolts in the bases of centrally compressed columns is proposed. The calculation of the forces is based on the calculation of extra-centrally compressed rods, taking into account: the influence of the cross-section shape; the initial curvature of the neutral axis of the column; random eccentricity; nonlinear steel work. The calculation of the attachment forces (Nult and Mfic) of columns on the foundation edge is based on the method of practical calculations of centrally compressed elements using the stability coefficients at central compression φ (longitudinal bending coefficients), which are calculated depending on the flexibility l. The calculation of the attachment forces for rods with different reduced flexibility was performed by FEM in the FEMAP software package, as well as analytically using fictitious forces in centrally compressed rods. To calculate the tearing forces in the foundation bolts, a calculation model is made taking into account the contact interaction of the base and the reinforced concrete base. Graphs of the effect of the flexibility of the centrally compressed rod on the tearing force in the foundation bolts at the stage of exhaustion of the bearing capacity of the column when calculating its stability as an element of a continuous section under central compression are constructed.

Study on the Relationship between Microscopic Structure and Mechanical Properties of HTPB Propellant

2010 ◽  
Vol 152-153 ◽  
pp. 1151-1155 ◽  
Author(s):  
Xu Chang Li ◽  
Jian Jiao ◽  
Jun Yan Yao ◽  
Liang Wang
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Cross Section ◽  
Structural Integrity ◽  
Solid Particles ◽  
Microscopic Structure ◽  
Structure State ◽  
Htpb Propellant ◽  
The Relationship ◽  
Bond Effect

By means of a tensile instrument and SEM, the mechanical property parameters of HTPB propellant test samples with different formulas were tested, and their microscopic fracture cross section patterns were observed. Take advantage of these testing results, the relationship between microscopic structure and mechanical properties of HTPB propellant was studied. The results show that the mechanical properties of a propellant are closely related to its microscpic structure state. The structural integrity of propellant is mainly influenced by the bond effect of the interface between binder and solid particles, solid particle’s shape, size and its distribution, the content of binder matrix, etc. These factors have important effects on the mechanical properties of propellant.

Structural Analysis for a Panamax Bulk Carrier

2008 ◽  
Author(s):  
Sandita Pacuraru-Popoiu ◽  
Paulina Iancu ◽  
Liviu I. Crudu
Keyword(s):  
Structural Analysis ◽  
Stress Distribution ◽  
Structural Integrity ◽  
Dynamic Pressure ◽  
Uniform Structure ◽  
Bulk Carrier ◽  
Element Analysis ◽  
Hull Girder ◽  
Fine Mesh ◽  
Hull Structure

This paper is devoted to the development of a structural analysis for a bulk carrier vessel. According to the CSR requirements for bulk carriers, an assessment of the hull structure using FEA (Finite Element Analysis) on a model extended over 3 cargo holds is presented. This method is used in order to assess the structural integrity of the cargo holds under the considered loads. The selected vessel is a PANAMAX bulk carrier with double hull and longitudinal uniform structure. There are three main priorities for the FE-analysis: one is to perform a fine mesh necessary to capture the stressed induced by the considered loads. The second priority is to apply the right boundary conditions in order to approach the hull girder bending and stress distribution on the cargo holds. The stress distribution is induced by the cargo weight, the hydrostatic pressure and the external water considered as dynamic pressure. The dynamic pressure was computed using an in-house code, neglecting the inertia forces induced by the ship motions and the horizontal accelerations. Also shear forces and bending moments were obtained for head angles of 0, 45 and 180 degrees.

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