• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.313-319
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• 2017

Cylindrical shells are often used in ship structures at deck plating with a camber, side shell plating at fore and aft parts, and bilge structure part. It has been believed that such curved shells can be modelled fundamentally by a part of a cylinder under axial compression. From the estimations with the usage of cylinder models, it is known that, in general, curvature increases the buckling strength of a curved shell subjected to axial compression, and that curvature is also expected to increase the ultimate strength. We conduct series of elasto-plastic large deflection analyses in order to clarify the fundamentals in buckling and plastic collapse behaviour of cylindrical shells under axial compression. From the numerical results, we derive design formula for predicting the ultimate strength of cylindrical shell, based on a series of the nonlinear finite element calculations for all edges, simply supporting plating, varying the slenderness ratio, curvature and aspect ratio, as well as the following design formulae for predicting the ultimate strength of cylindrical shell. From a number of analysis results, fitting curve can be developed to use parameter of slenderness ratio with implementation of the method of least squares. The accuracy of design formulae for evaluating ultimate strength has been confirmed by comparing the calculated results with the FE-analysis results and it has a good agreement to predict their ultimate strength.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.3
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• pp.295-300
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• 2011

Ship are a box-shaped structure. It is used often fore and aft parts, bilge strake, deck with camber of ship structures. When this structure is compared with flat plate structure, it different to behaviour. Generally, if it subjected to axial compressive load, ultimate strength depend on the change of curvature. Also, In this paper, stiffened curved plate with 1/2+1+1/2 bay model subjected to compressive load carried out the elasto-plastic large deflection series analysis. and parameter effect considered slender ratio, web height/thickness as well as change of curvature and investigated collapse mode for analysis model.

• Steel and Composite Structures
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• v.8 no.1
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• pp.1-18
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• 2008

Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. In addition, axial forces will be induced with temperature increasing and play an important role on the behaviour of the restrained beam. The factors influencing the behavior of a restrained beam subjected to fire include the stiffness of axial and rotational restraints, the load type on the beam and the distribution of temperature in the cross-section of the beam, etc. In this paper, a simplified model is proposed to analyze the performance of restrained steel beams in fire condition. Based on an assumption of the deflection curve of the beam, the axial force, together with the strain and stress distributions in the beam, can be determined. By integrating the stress, the combined moment and force in the cross-section of the beam can be obtained. Then, through substituting the moment and axial force into the equilibrium equation, the behavior of the restrained beam in fire condition can be worked out. Furthermore, for the safety evaluation and repair after a fire, the behaviour of restrained beams during cooling should be understood. For a restrained beam experiencing very high temperatures, the strength of the steel will recover when temperature decreases, but the contraction force, which is produced by thermal contraction, will aggravate the tensile stresses in the beam. In this paper, the behaviour of the restrained beam in cooling phase is analyzed, and the effect of the contraction force is discussed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.91-99
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• 1998

The widespread use of thin shell structures has created a need for a systematic method of analysis which can adequately account for arbitrary geometric form and boundary conditions as well as arbitrary general type of loading. Therefore, the stress and analysis of thin shell has been one of the more challenging areas of structural mechanics. A wide variety of numerical methods have been applied to the governing differential equations for spherical and cylindrical structures with a few results applicable to practice. The analysis of axisymmetric spherical shell is almost an every day occurrence in many industrial applications. A reliable and accurate finite element analysis procedure for such structures was needed. Dynamic loading of structures often causes excursions of stresses well into the inelastic range and the influence of geometry changes on the response is also significant in many cases. Therefore both material and geometric nonlinear effects should be considered. In general, the shell structures designed according to quasi-static analysis may fail under conditions of dynamic loading. For a more realistic prediction on the load carrying capacity of these shell, in addition to the dynamic effect, consideration should also include other factors such as nonlinearities in both material and geometry since these factors, in different manner, may also affect the magnitude of this capacity. The objective of this paper is to demonstrate the dynamic characteristics of spherical shell. For these purposes, the spherical shell subjected to uniformly distributed step load was analyzed for its large displacements elasto-viscoplastic static and dynamic response. Geometrically nonlinear behaviour is taken into account using a Total Lagrangian formulation and the material behaviour is assumed to elasto-viscoplastic model highly corresponding to the real behaviour of the material. The results for the dynamic characteristics of spherical shell in the cases under various conditions of base-radius/central height(a/H) and thickness/shell radius(t/R) were summarized as follows : The dynamic characteristics with a/H. 1) AS the a/H increases, the amplitude of displacement in creased. 2) The values of displacement dynamic magnification factor (DMF) were ranges from 2.9 to 6.3 in the crown of shell and the values of factor in the mid-point of shell were ranged from 1.8 to 2.6. 3) As the a/H increases, the values of DMF in the crown of shell is decreased rapidly but the values of DMF in mid-point shell is increased gradually. 4) The values of DMF of hoop-stresses were range from 3.6 to 6.8 in the crown of shell and the values of factor in the mid-point of shell were ranged from 2.3 to 2.6, and the values of DMF of stress were larger than that of displacement. The dynamic characteristics with t/R. 5) With the thickness of shell decreases, the amplitude of the displacement and the period increased. 6) The values of DMF of the displacement were ranged from 2.8 to 3.6 in the crown of shell and the values of factor in the mid-point of shell were ranged from 2.1 to 2.2.

• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.27-33
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• 2009

Estimation of the buckling and ultimate strength of a continuous stiffened plate subjected to combined transverse compression and lateral pressure is of high importance to ensure the safety of ship structures, particularly for the bottom plating under a deep draft condition For example, bottom plating of bulk carriers is subjected to transverse thrust caused by the bending of double bottom structure and the direct action of pressure on the side shells. Most of experimental tests, theoretical approach and numerical researches have been performed on the buckling and ultimate strength behaviour of plates or stiffened plates under combined compression and lateral pressure. With regard to stiffened panels, however, most of studies have been concerned with the load conditions of combined longitudinal thrust and lateral pressure, while fewer studies have been performed for the combined transverse thrust and lateral pressure. In addition, the previous researches are mainly concerned with an isolated rectangular plate simply supported along the all edges, whereas actual ship plating is continuous across the transverse frames and heavy girders. In the present paper, a series of elastoplastic large deflection FEA on a continuous stiffened plate is performed and then clarify the characteristic of collapse mode and explain the effect of transverse compression.

• Advances in materials Research
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• v.8 no.4
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• pp.337-359
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• 2019

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C⁰ continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (T_g). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

• Steel and Composite Structures
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• v.8 no.3
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• pp.217-230
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• 2008

The increasing use of performance-based approaches in structural fire engineering design of multi-storey composite buildings has prompted the development of various tools to help quantify the influence of tensile membrane action in composite slabs at elevated temperatures. One simplified method which has emerged is the Bailey-BRE membrane action method. This method predicts slab capacities in fire by analysing rectangular slab panels supported on edges which resist vertical deflection. The task of providing the necessary vertical support, in practice, requires protecting a panel's perimeter beams to achieve temperatures of no more than $620^{\circ}C$ at the required fire resistance time. Hence, the integrity of this support becomes critical as the slab and the attached beams deflect, and large deflections of the perimeter beams may lead to a catastrophic failure of the structure. This paper presents a finite element investigation into the effects of vertical support along slab panel boundaries on the slab behaviour in fire. It examines the development of the membrane mechanism for various degrees of edge-beam protection, and makes comparisons with predictions of the membrane action design method and various acceptance criteria.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Journal of the Korean Society of Marine Environment & Safety
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• v.10 no.1 s.20
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• pp.29-33
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• 2004

Design of general steel structure had applied to achieve elastic designing concept so far. Because elastic design supposes that whole structure complies with elasticity formula so that achieve via allowable stress of material. It is concept that calculate stress distribution of construction about action external load and estimate load when the maximum stress reaches equally with allowable stress that is established by maximum safety load of the structure. But, absence that compose actuality structure by deal with external load increase small success surrender and structure hardness falls and structure in limited state finally on the whole as showing complicated process by interference between collapse and buckling under compression. Applied ANSYS (elasto-plasticity large deformation finite element method) to be mediocrity finite element program for analysis method and analysis control used in Newton-Raphson method & Arc-length method.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.93-103
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• 2018

This study showed that experimental study of inelastic nonlinear behavior of two-way beam string structures. General large span structures consisting of beam members have large moment and long cross section of area. In order to decrease these excessive moment and deflection, the two-way beam string structures composed of H-Beam, strut, and cable elements were proposed. In the two-way string beam, the cable with the prestress improves force distribution of some weight reduction. Two systems made of structural steel and cables were tested. The nonlinear behaviour of the two-way beam string structures studied by using finite element model and compared to experimental results. The displacement of the LVDT in the center of the beam correspond with the ABAQUS results. 2,200MPa cable can afford to bear breaking load than 1,860MPa cable. The two-way beam string structures is correlated to the finite element model and the experimental results. In consequence, It showed that the system with two-way cables exhibits much better structural performances than H-Beam structures and beam with cable.