• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.95-104
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• 2011

As sea state harsher in the ocean space, more large motion and wave loads occurs on ships hull by non-linear phenomena. To consider nonlinear effect on ships hull in the structural design verification, the direct calculation method with numerical approach is used rather than rule values for the reliable accuracy. In this paper, the non-linear wave loads analysis in time domain is performed by using a Rankine Panel Method together with numerical schemes. Linear calculations have been carried out based on DNV CSA-2 notation to generate the motion responses and wave loads of large ships. By short and long term analysis, the design wave amplitudes are selected for the nonlinear analysis. The maximum wave induced bending moment in hogging and sagging conditions are calculated in the nonlinear analysis. Also, the green water effect on the wave induced vertical bending moment was investigated. The results show the vertical bending moments are more influenced by green water in sagging condition than in hogging condition due to green water loading.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.4
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• pp.386-402
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• 2012

In this paper, a method to estimate ice loads as a function of the buttock angle of an icebreaker is presented with respect to polycrystalline freshwater ice. Ice model tests for different buttock angles and impact velocities are carried out to investigate ice pressure loads and tendencies of ice pressure loads in terms of failure modes. Experimental devices were fabricated with an idealized icebreaker bow shape, and medium-scale ice specimens were used. A dry-drop machine with a freefall system was used, and four pressure sensors were installed at the bottom to estimate ice pressure loads. An estimation equation was suggested on the basis of the test results. We analyzed the estimation equation for design ice loads of the International Association of Classification Societies (IACS) classification rules. We suggest an estimation equation considering the relation between ice load, buttock angle, and velocity by modifying the equations given in the IACS classification rules.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.4
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• pp.195-203
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• 2018

The wave impact on ships could cause local damage to the ship's hull, which has been a concerning issue during the ship design process. In recent years, local structural damages of ships caused by slamming loads have been reported by accident; therefore, it is necessary to study the local slamming pressure loads and structural response assessment. In the present study, slamming loads around the ship's bow region in the presence of regular wave have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM) in conjunction with the $k-{\Box}$ turbulence model. The dynamic structural response has been calculated using an explicit FE method. By adding the slamming pressure load of each time step to the finite element model, establishing the reasonable boundary conditions, and considering the material strain-rate effects, the dynamic response prediction of the bow flare structure has been achieved. The results and insights of this study will be helpful to design a container ship that is resistant enough to withstand bow flare slamming loads.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.443-450
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• 2010

A concrete lining of NATM tunnel had been considered as interior materials. But recently we consider it as structural materials. Therefore we must consider various loads. Relaxed rock load is a main load which decides thickness and reinforcement presence of concrete lining. In practice conservatively, Terzaghi's rock load theory has been accepted to estimate relaxed rock loads in urban subway tunnel design. This study investigates the equations of relaxed rock loads used in the design of NATM concrete lining. Structural analysis are executed based on various equations of relaxed rock loads, and concrete lining forces are compared.

• Geomechanics and Engineering
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• v.37 no.2
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• pp.167-178
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• 2024

The natural frequency shift under cyclic environmental loads is a key issue in the design of monopile-based offshore wind power turbines because of their dynamic sensitivity. Existing evidence reveals that the natural frequency shift of the turbine system in sand is related to the varying foundation stiffness, which is caused by soil deformation around the monopile under cyclic loads. Therefore, it is an urgent need to investigate the effect of soil deformation on the system frequency. In the present paper, three generalized geometric models that can describe soil deformation under two-way cyclic loads are proposed. On this basis, the cycling-induced changes in soil parameters around the monopile are quantified. A theoretical approach considering three-spring foundation stiffness is employed to calculate the natural frequency during cycling. Further, a parametric study is conducted to describe and evaluate the frequency shift characteristics of the system under different conditions of sand relative density, pile slenderness ratio and pile-soil relative stiffness. The results indicate that the frequency shift trends are mainly affected by the pile-soil relative stiffness. Following the relevant conclusions, a design optimization is proposed to avoid resonance of the monopile-based wind turbines during their service life.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.207-216
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• 1997

Estimation of loads on tunnel lining is one of the major issues to be addressed in the design of a tunnel. The existing analytical methods do not consider important details of construction and the variation of geology along the tunnel axis. The measured loads obtained from several sanitary and subway tunnels in Edmonton, Alberta, Canada, are compared with the lining loads calculated using the existing analytical methods. However, the existing methods are determined to be not fully satisfactory for the estimation of lining loads. To account for face and heading effects occurring prior to lining installation, the stress reduction factor determined using Eisenstein and Negro's method is used coupled with an analytical solution for calculation of lining loads.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.330.2-330
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• 2002

It is conducted to analyze vibration loads on KSR-III and its major segments during their ground transportation and various handling process. These loads may be different from the real flight environment. Inadequate assessment of these loads can cause not only local damages on the rocket system but also the critical problem like flight mission failure. Therefore, transportation and handling loads must be considered during design and attenuated to ensure that the rocket structural damage does not occur. (omitted)

• Wind and Structures
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• v.3 no.2
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• pp.83-96
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• 2000

Due to their high corrosion and chemical resistance, fiber reinforced plastics (FRP) are becoming widely used as the main structural material for industrial chimneys. However, no national code currently exists for the design of such type of chimneys. The purpose of this study is to investigate analytically the response of FRP chimneys to wind loads. The classical lamination theory is used to substitute the angle-ply laminate of a FRP chimney with an equivalent orthotropic material that provides the same stiffness. Dynamic wind loads are applied to the equivalent chimney to evaluate its response to both along and across wind loads. A parametric study is then conducted to identify the material and geometric parameters affecting the response of FRP chimneys to wind loads. Unlike the across-wind response, the along-wind tip deflection is found to be highly dependent on the angle of orientation of the fibers. In general, the analysis shows that FRP chimneys are very vulnerable to across-wind oscillations resulting from the vortex shedding phenomenon.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.269-279
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• 2008

This study was conducted to develop the design methodology of transverse post-tensioning for the prestressed concrete pavement (PSCP). The transverse stress distribution was analyzed when the transverse anchor spacing changed. The tensile stress distribution in the PSCP slab due to the environmental and vehicle loads was also investigated. The reasonable methods were discussed to determine the design loads including environmental and vehicle loads and the PSCP allowable tensile stress used for the basis of the selection of the stress application amount from the tensioning. The results of this study showed that as the transverse anchor spacing increased, the range of the stress loss became larger and the stress loss was significant near the shoulder. The design of the transverse post-tensioning can be performed by obtaining the stresses under the design loads and by considering the allowable tensile stress; however, the tensile stresses at different locations such as the shoulder, wheel pass, and slab interior should also be checked and kept below the allowable tensile stress.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.83-90
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• 2018

Considering the increased threats from worldwide terrors and the increased demands on the blast resistant design of commercial buildings, this study is aimed at understanding the basic concept of blast resistant design and evaluating the blast performance with an actual design example. Although there are many differences between earthquake and blast loads, the design concept against both loads is similar in terms of allowing the plastic behavior of a structure and sharing the ductile detailing. Through the blast performance evaluation of a target building provided in this study, it is noted that a well-designed building for the conventional loads can have a certain level of blast resistance. However, this cannot be generalized since the blast load on a structure varies depending on the type of weapon, TNT equivalence, standoff distance, etc. Architectural planning with positioning the sacrificial structure or maintaining a sufficient standoff distance from the expected detonation is the simple and effective way of improving the blast resistance of a building.