• Journal of Korean Association for Spatial Structures
• /
• v.12 no.2
• /
• pp.89-98
• /
• 2012

This study investigates the optimum structural design of space truss considering global buckling, and is to obtain the minimal weight of the structure. The mathematical programming method is used for optimization of each member by member force. Besides, dynamic programming method is adapted for consideration in snap-through buckling. The mathematical modeling for optimum design of truss members consists of objective function of total weight and constrain equations of allowable tensile (or compressive) stress and slenderness. The tangential stiffness matrix is examined to find the critical point on equilibrium path, and a ratio of the buckling load to design load is reflected in iteration procedures of dynamic programming method to adjust the stiffness of space truss. The star dome is examined to verify the proposed optimum design processor. The numerical results of the model are conversed well and satisfied all constrains. This processor is a relatively simple method to carry out optimum design with consideration in global buckling, and is viable in practice with respect to structural design.

• Proceedings of KOSOMES biannual meeting
• /
• 2005.05a
• /
• pp.155-159
• /
• 2005

Analysis target ship is not introduced yet in domestic as steel yacht that is getting into the spotlight by leisure life in Australia or Japan. Sailing yacht or Yacht for leisure time made of FRP into controlling power fare mainly and the design and made of latest fishing boat and something of domestic is consisting mainly. To need investigated for concept is various kinds overall strength as that use mainly steel wire material structurally of steel yacht by small crafts about Longi strength, Transe strength portion even of design safety factor at subject to do Rule's allowable stress enough stable structure accomplish. But it is assessment of part intensity that become refer to most in small size ship.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.1 s.34
• /
• pp.125-135
• /
• 1998

This study presents a design method for three-span continuous preflex composite girder bridges (3S-PCB) which imposes prestresses in the negative moment region by lifting or lowering interior supports and the design method is automated by a computer program which incorporates optimal design procedure. The objective function for the design of 3S-PCB minimizes the cost of construction materials and the constraint functions represent the limited dimensions of the design section and the allowable stress for each structural member as given in the specifications. Optimal design procedure used in this study is a modification of existing sequential unconstrained minimization technique (SUMT), a numerical analyses procedure for two-span continuous preflex composite bridges. The optimized design sections determined for each span length are compared with those of simple preflex composite beams (SPCB) and the optimal girder depth is determined by defining the relationship between girder depth and construction material costs.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.1
• /
• pp.1-8
• /
• 2008

This research carried out to optimize crossbeams and stringers of steel box girder bridges, which are parts of floor system and support loading from the bridge deck. In the current design practice, the crossbeam is densely deployed with a spacing of 6 meters, and the stringer is placed between the crossbeams. The crossbeams and stringer are connected to the deck through slab anchors but the allowable stress of the compression flange is determined by the lateral-torsional buckling. To increase economic efficiency of the steel box girder bridges. the increased spacing of the crossbeam was studied. The study shows that the spacing can be increased up to 10 meters. However, higher strength steel plates are necessary. Shear studs rather than slab anchors are also recommended to prevent lateral-torsional buckling strength of the crossbeams and stringer.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.1
• /
• pp.396-408
• /
• 2019

The tubes which are applied in jacket platforms as the supporting structure might be collided by supply vessels. Such kind of impact will lead to plastic deformation on tube members. As a result, the ultimate strength of tubes will decrease compared to that of intact ones. In order to make a decision on whether to repair or replace the members, it is crucial to know the residual strength of the tubes. After being damaged by lateral impact, the simply supported tubes will definitely loss a certain extent of load carrying capacity under uniform axial compression. Therefore, in this paper, the relationship between the residual ultimate strength of the damaged circular tube by collision and the energy dissipation due to lateral impact is investigated. The influences of several parameters, such as the length, diameter and thickness of the tube and the impact energy, on the reduction of ultimate strength are investigated. A series of numerical simulations are performed using nonlinear FEA software LS-DYNA. Based on simulation results, a non-dimensional parameter is introduced to represent the degree of damage of various size of tubes after collision impact. By applying this non-dimensional parameter, a simplified formula has been derived to describe the relationship between axial compressive residual ultimate and lateral impact energy and tube parameters. Finally, by comparing with the allowable compressive stress proposed in API rules (RP2A-WSD A P I, 2000), the critical damage of tube due to collision impact to be repaired is proposed.

• Progress in Superconductivity and Cryogenics
• /
• v.21 no.1
• /
• pp.40-44
• /
• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.34 no.2
• /
• pp.29-40
• /
• 2018

Strength design wind loads for the wind resistance design of structures shall be evaluated by the product of wind loads calculated based on the basic wind speed with 100 years return period and the wind load factor 1.3 specified in the provisions of load combinations in Korean Building Code (KBC) 2016. It may be sure that the wind load factor 1.3 in KBC(2016) had not been determined by probabilistic method or empirical method using meteorological wind speed data in Korea. In this paper, wind load factors were evaluated by probabilistic method and empirical method. The annual maximum 10 minutes mean wind speed data at 69 meteorological stations during past 40 years from 1973 to 2012 were selected for this evaluation. From the comparison of the results of those two method, it can be found that the mean values of wind load factors calculated both probability based method and empirical based method were similar at all meteorological stations. When target level of reliability index is set up 2.5, the mean value of wind load factors for all regions should be presented about 1.35. When target level of reliability index is set up 3.0, wind load factor should be presented about 1.46. By using the relationship between importance factor(conversion factor for return period) and wind load factor, the return periods for strength design were estimated and expected wind speeds of all regions accounting for strength design were proposed. It can be found that return period to estimate wind loads for strength design should be 500 years and 800 years in according to target level of reliability index 2.5 and 3.0, respectively. The 500 years basic wind speed map for strength design was suggested and it can be used with a wind load factor 1.0.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.5
• /
• pp.27-35
• /
• 2008

Geotechnical characteristic values for reliability-based design were analyzed using domestic marine clays. Analysis results indicate that there were close to mean values in oder of Student/Ovesen, Schneider and EN 1990's approach. However, it was found that the EN 1990's approach is inappropriate far estimating geotechnical characteristic value due to low reliability of estimation results. Four approaches had a trend of evaluating characteristic value conservatively with increasing of soil variability. Also, stability and settlement of breakwater subjected to nominal stress with unimproved soft grounds were computed to investigate the effects of estimated characteristic values. In case of using the Schneider's approach, the ratio of allowable bearing capacity/acting loads suggested 65% of that obtained from using the arithmetic mean approach, and showed underestimated value of 13.6% of the settlement obtained from the latter. The comparison of case designs using a representative value from arithmetic mean approach with the proposed approaches, using characteristic value showed that the former was mostly overestimated.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.8
• /
• pp.107-116
• /
• 2007

Load and Resistance Factor Design (LRFD) method is being used increasingly in geotechnical design practice worldwide, and is expected to completely replace the current Allowable Stress Design (ASD) method in the near future. LRFD has advantages over ASD in that it allows the design of superstructures and substructures at a consistent reliable level by quantification of failure probability based on reliability analysis. At present, resistance factors for cast-in-place piles embedded in rocks are determined by AASHTO only for the intact rock conditions. In Korea, however, most of the bedrocks in which piles are embedded are heavily weathered. Thus, this study will try to determine the resistance factors of heavily weathered rocks (so-called intermediate goo-materials). To this aim, reliability analysis was carried out to evaluate the resistance factors of cast-in-place piles embedded in intermediate geo-materials in Korea. Pile load test data of 21 cast-in-place piles of 4 construction sites were used for the analysis. Depending on the method which calculates the pile capacities, the resulting resistance factors ranged between 0.1 and 0.6.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.18 no.1
• /
• pp.19-25
• /
• 2022

Nuclear Power Plants (NPP) should be designed to have sufficient safety margins and to ensure seismic safety against earthquake that may occur during the plant life time. After the 9.12 Gyeongju earthquake accident, the structural integrity of nuclear power plants due to the beyond design basis earthquake is one of key safety issues. Accordingly, it is necessary to conduct structural integrity evaluations for domestic NPPs under beyond design basis earthquake. In this study, the Level 3 LBB (Leak Before Break) evaluation was performed by considering the beyond design basis earthquake for the surge line of a OPR1000 plant of which design basis earthquake was set to be 0.2g. The beyond design basis earthquake corresponding to peak ground acceleration 0.4g at the maximum stress point of the surge line was considered. It was confirmed that the moment behaviors of the hot leg and pressurized surge nozzle were lower than the maximum allowable loading in moment-rotation curve. It was also confirmed that the LBB margin could be secured by comparing the LBB margin through the Level 2 method. It was judged that the margin was secured by reducing the load generated through the compliance of the pipe.