• Steel and Composite Structures
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• v.34 no.6
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• pp.853-862
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• 2020

In recent years, due to the many advantages cable-stayed bridges have often constructed in medium and long span. These advantages can be listed as an aesthetically pleasing appearance, economic and easy construction, etc. The main structural elements of cable-stayed bridges are listed as deck, pylon, cables and foundation. Perhaps one of the most vital and expensive of these structural elements is stay-cables. Stay-cables ensure the allowable displacement and distribution of bending moments along the bridge deck with prestressing force. Therefore the optimum design of the stay-cables and prestressing force are very important in achieving the performance expected from the cable-stayed bridges. This paper aims to obtain the stay-cables size and prestressing force optimization of the cable-stayed bridge. For this purpose, single pylon and fan type cable configuration Manavgat Cable-Stayed Bridge was selected as an example. The three dimensional (3D) finite element model (FEM) of the bridge was created with SAP2000. Analysis of the 3D FEM of the bridge was conducted under the different combined effects of the self-weight of the structural element, prestressing force of stay-cable and live load. Stay-cable stress and deck displacement were taken into account as constraints for the optimization problem. To optimize this existing bridge a metaheuristic algorithm named Jaya was used in the optimization process. 3D FEM of the selected bridge was repeatedly analyzed by using Open Applicable Programming Interface (OAPI) properties of SAP2000. To carry out the optimization process the developed program which integrates the Jaya algorithm and the required codes for calling SAP2000 is coded in MATLAB. At the end of the study, the total weight of the stay-cables was reduced more than 40% according to existing stay cables under loads taken into account.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.4
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• pp.61-68
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• 1986

This paper presents a method for developing a probability-based working stress design code for reinforced concrete. Reliability of reinforced concrete structural members is evaluated by using an advanced second moment reliability method, and then, a practical method for code calibration is shown in this paper. The target reliability indices for various structural elements are determined by considering the results of the numerical studies on the safety of the structures designed by the current code, and by reflecting the construction practice. A set of allowable stresses and safety factors for reinforced concrete is proposed as a possible substitute for the current safety provisions, based on the rational target reliability indices.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1190-1199
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• 2014

As a considerable, experimental approach, an autocarriage type of $CO_2$ welding machine and a MIG(metal inert gas) welding robot in the inert gas atmosphere were utilized in order to realize Al 5083 welding to hull and relevant components of green leisure ships. This study aims at investigating the effect of welding conditions(current, voltage, welding speed, etc.) on thermal deformation that occurs as welding operation and tensile characteristics after welding, by using Al 5083, nonferrous material, applied to manufacturing of eco-environmental leisure ships. With respect to welding condition to minimize the thermal deformation, 150 A and 16 V at the wire-feed rate of 6 mm/sec were acquired in the process of welding Al 5083 through an auto carriage type of $CO_2$ welding feeder. As to tensile characteristics of Al 5083 welding through a MIG welding robot, most of tensile specimens showed the fracture behavior on HAZ(heat affected zone) located at the area joined with weld metal, except for some cases. Especially, for the case of the Al specimen with 5 mm thickness, 284.62 MPa of tensile strength and 11.41 % of elongation were obtained as an actual allowable tensile stress-strain value. Mostly, after acquiring the optimum welding condition, the relevant welding data and technical requirements might be provided for actual welding operation site and welding procedure specification (WPS).

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.1
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• pp.37-49
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• 2005

In a tunnel, failure of its supports can cause failure of the tunnel. Therefore it is important to estimate safety factor of the tunnel which the failure of its supports is taken into account. In previous studies, supports of tunnels were usually modelled as beam elements. The failure of the supports was decided by comparing the allowable stress and the calculated bending stresses inside the beam elements in estimating safety factor of the tunnel considering the failure of its supports. In this study, it is suggested how to model the supports properly. To this end, supports of a tunnel were modelled by both beam (elastic) elements and continuum (elasto-plastic) elements in two dimensional numerical analyses. Meanwhile, it was analyzed how rock mass class, coefficient of lateral pressure, shotcrete thickness, the existence of rock bolt, and excavation method had an effect on the safety factor of a tunnel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2581-2587
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• 2013

This paper aims at the design of wheel and axle with cap. The cap is conceptually designed by using TRIZ/CAE. Wheel axle is used at railway vehicle to safety and it is always investigated to reduce the railway vehicle weight. The cap has hollow shaft with the material of SM45C. Cap is located in the bearing seat of wheel and axle. The cap becomes durable within the allowable stress of EN13103, 13104 standard. In this study, the strength of wheel and axle with cap becomes higher than that of hollow shaft. The weight of wheel and axle with cap becomes lower by about 6.75 percent than that of solid shaft. The confidence of wheel and axle with cap can be improved by comparing with solid and hollow shafts.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.137-146
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• 2010

This study was conducted to develop the design methodology of gap slabs for the post-tensioned concrete pavement (PTCP). The gap slabs were considered as unbonded, half bonded, and bonded types. According to the types of the gap slabs, the curling stresses were investigated first under the environmental loads. The stresses due to the vehicle loads were analyzed considering both the single and tandem axles. The method to calculate the prestressing amount was suggested by comparing the combined stresses due to both loads and the allowable tensile stress of concrete. The prestressing amount for the unbonded type gap slab could be designed by considering only the gap slab; however, for the half bonded and bonded gap slabs, the whole PTCP slab should be analyzed to properly design the prestressing amount.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.117-126
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• 2011

The buckling assessment of plate panels described in common structural rules (CSR) is to be determined according to the buckling utilization factor with hull girder stresses calculated on net hull girder sectional properties. As the thickness requirement for the buckling assessment of plate panels is not explicitly given in CSR, a lot of time is spent to find the proper thickness of plate panels until reaching to an allowable buckling utilization factor. In this study, in order to reduce time and cost, the thickness requirement of plate panels satisfying buckling assessment was derived. The structural design system included with the thickness requirement for buckling assessment was developed. The system is called as Oil-tanker Automated Structural Investigation System (OASIS). The design result of longitudinal strength members using OASIS was verified by Nauticus Hull which is the rule scantling software of DNV. Finally, optimum design of a double hull tanker for the minimum weight using OASIS was presented.

• Land and Housing Review
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• v.3 no.3
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• pp.279-286
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• 2012

The limit states design method is replacing the allowable stress design method worldwide, e.g. the design code of ISO and various construction codes of Korea are adopting the reliability based limit state method. This paper proposed LRFD design value which is one of limit states design method for the PHC bored pile used as building foundation. This paper analysed 81 load test results and the bearing design(Meyerhof method & SPT-CPT conversion method), and proposed LRFD value for each design reliability Index 2.33 and 3.0 for PHC bored pile. LRFD value of PHC bored pile represents 0.36~0.44 for Meyerhof method and 0.24~0.31 for SPT-CPT conversion method according to the deign reliability index.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.112-118
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• 2015

These days, there are lots of skyscrapers being constructed in downtown areas. However, it requires columns which have a way heavier load. and far more extensive cross sections of column as well. Therefore, it is hard to lay the foundation in downtown areas. This being the case, composite columns such as CFT column are primarily being used. However, CFT column is occurred of difficult beam-column connection development and lower performance since CFT column is closed cross-section. Especially, the result of the study concerning development of connection details with CFT column and exterior diaphragms are very low in current state. In this study, through developing CFT column-H shape steel beam applicating Y shape plate, set width and depth of Y shape plate which affect structural performance of connection details applicating Y shape plate as main variables, and evaluate structural performance through experiments. And also, design Y shape plate used at experiments as setting allowable stress for tension suggested at design criteria lower than axial force of tension side flange connected Y shape plate, through shape of destruction, verify the structural safety and performance of Y shape plate.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.90-97
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• 1996

The optimal mesh refinement has a meaning that error of the every element is within an allowable level and in uniformly distributed. The adaptive mesh generation may be required to achieve the optimal mesh generation. For the purpose of optimal mesh generation, an error estimation and an adaptive mesh refinement are required. Using the adaptive mesh generation the second finite element analysis is performed with the result of the first analysis. In the process the error estimation is required. In this study the adaptive mesh generation program for triangular element is developed, and for a posteriori error estimation the stress projection approach is considered. It has been found the multigrid technique, where the error estimation and the mesh generation are combined in multi-step of analysis, may be used efficiently in the finite element analysis.