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To accommodate growing demands on either heavy steel structures or unique buildings with irregular configurations, built-up wide-flange steel (BWS) beams are being popularly used in modern steel construction. In current fabrication practices of BWS members, high-performance steels produced in steelmaking factories under the thermo-mechanical control process (TMCP) are typically utilized to achieve proper welding performances. However, since its basic unit price is quite higher than typical hot-rolled steel materials, this study introduced a hybrid BWS section for cost saving with no performance degradation, where high-performance TMCP steel was used in flanges, and conventional hot-rolled steel was adopted in web plate. To verify the tensile performances of a hybrid BWS section with non-uniform properties, split T tension and Charpy impact tests were conducted, and flexural tests were also carried out on hybrid and homogeneous BWS beam members. On this basis, it was confirmed that the structural performance of the hybrid BWS member is comparable with that of the conventional one with a uniform section property.

The diagrid structural system has been in the spotlight because of its superiority in terms of its resistance to lateral forces when applied to skyscrapers. In the diagrid structural system, most columns can be eliminated because the vertical loads (gravity loads) and horizontal loads (lateral loads) are delivered simultaneously due to the triangular shape of the diagrid module. Despite this increasing interest, few studies have examined the connection shape and details, which has made it difficult to employ the system to the buildings. In this study, the structural safety of the node connections in a circular steel tube diagrid structural system, which has been considered in the Cyclone Tower in Korea (Seven stories below and fifty-one above the ground), was evaluated using finite element analysis and 4 full-scale specimens. The parameters assessed were the extended length (20, 40, and 60 mm) and thickness (40 and 50 mm)

Received 19 April 2014; received in revised form 14 May 2014; accepted 3 June 2014ABSTRACTEngineering applications of global optimization techniques are recently abundant in the litera-ture and it may be caused by both new methodologies arising and faster computers coming out.Many of the optimization techniques are based on natural or biological phenomena. This studyput focus on enhancing the performace of Cuckoo Search (CS) among them since it has theleast number of parameters to tune. The proposed enhancement can be achieved by applyingsurrogate-based optimization at every cycle of CS, which fortifies the exploitation capability ofthe original method. The enhanced algorithm has been applied several engineering design prob-lems with constraints. The proposed method shows comparable or superior performance to theoriginal method.Key Words: Approximation, Cuckoo Search (CS), Design of experiments (DOE), Global optimi-zation, Metamodel, Surrogate-based optimization (SBO)

Various types of reinforcement splicing methods have been developed and implemented in reinforced concrete construction projects for achieving the continuity of reinforcements. Due to the complicated reinforcement arrangements and the difficulties in securing bar spacing, the traditional lap splicing method, which has been widely used in reinforced concrete constructions, often shows low constructability and difficulties in quality control. Also, lap spliced regions are likely to be over-reinforced, which may not be desirable in seismic design. On the other hand, mechanical splicing methods can offer simple and clear arrangements of reinforcement. In order to utilize the couplers for the ribbed-deformed bars, however, additional screw processing at the ends of reinforcing bars is typically required, which often lead to performance degradations of reinforced concrete members due to the lack of workmanship in screw processing or in adjusting the length of reinforcing bars. On the contrary, the use of screw-ribbed reinforcements can easily solve these issues on the mechanical splicing methods, because it does not require the screw process on the bar. In this study, the mechanical coupler suitable for the screw-ribbed reinforcements has been developed, in which any gap between the reinforcements and sleeve device can be removed by grouting high-flow inorganic mortar. This study presents the uniaxial tension tests on the screw-ribbed reinforcement with the mechanical sleeve devices and the cyclic loading tests on RC columns with the developed coupler. The test results show that the mechanical sleeve connection developed in this study has an excellent splicing performance, and that it is applicable to reinforced concrete columns with a proper confinement by hoop reinforcement.

The concept of robust optimization is based on Taguchi's method. Especially, robustness indices of objective function pursue an insensitive and conservative design when there are variations on design variables and parameters. To accomplish the purpose, various robustness indices on the objective function have been developed. However, it can be caused limitations to develop the robustness index, because there is difference between the Taguchi's method and robust optimization. In this paper, an investigation is performed to identify the characteristics and the drawbacks of the previous studies. To achieve the purpose, evaluations are conducted by using the examples which have both a deterministic optimum and a robust optimum. Moreover, a new viewpoint as well as a robustness index using a supremum value of the objective function is proposed based on the investigation.

Vehicle collisions frequently happen at a low speed. Insurance companies and the Research Council for Automobile Repairs both require reduction of repair costs and improvement in occupant safety in a low-speed crash. In order to reduce repair costs, an energy absorbing device such as the crash box is usually installed. The crash box is a thin-walled structure attached between the vehicle bumper structure and the side rail. The determination of the crash box geometry is quite important to absorb the impact energy, since the installation space of the crash box is not very large. In this research, a design procedure to determine the cross-sectional dimensions is proposed to enhance the energy absorption capability of the crash box. The proposed process has two steps. In the first step, the cross-sectional dimensions for the conceptual design are determined in two ways. One is a parameter study using discrete design with an orthogonal array. The cross-sectional dimensions of the crash box are selected among the available cross-sections, such as a circle or a polygon. The cross-sectional dimensions are determined by the analysis of the mean from the discrete design with an orthogonal array. The other is topology optimization, which is performed to determine the cross-section of the crash box to maximize the absorbed strain energy based on the Research Council for Automobile Repairs test conditions. The equivalent static loads method for non linear static response structural optimization is employed to solve the formulated topology optimization problems. The cross sections of the crash box are determined from the results of the conceptual design. In the second step, the detailed design processes are performed by using discrete design with an orthogonal array for the models that are selected in the first step. The detailed shapes of the new crash boxes are determined from the detailed design. The optimization problem for the crash box is formulated considering the geometric constraints of fitting into the given space for the crash box. Three new types of crash box are suggested, with detailed shapes from the proposed design procedure.

The thorns of Gleditsia sinensis are used as a medicinal herb in China and Korea. However, the mechanisms responsible for the antitumor effects of the water extract of Gleditsia sinensis thorns (WEGS) remain unknown. HCT116 cells treated with the WEGS at a dose of 800 μg/mL (IC50) showed a significant decrease in cell growth and an increase in cell cycle arrest during the G2/M-phase. G2/M-phase arrest was correlated with increased p53 levels and down-regulation of the check-point proteins, cyclinB1, Cdc2 and Cdc25c. In addition, treatment with WEGS induced phosphorylation of extracellular signal-regulated kinase (ERK), p38 MAP kinase and JNK (c-Jun N-terminal kinases). Moreover, inhibition of ERK by treatment of cells with the ERK-specific inhibitor PD98059 blocked WEGS-mediated p53 expression. Similarly, blockage of ERK function in the WEGS-treated cells reversed cell-growth inhibition and decreased cell cycle proteins. Finally, in vivo WEGS treatment significantly inhibited the growth of HCT116 tumor cell xenografts in nude mice with no negative side effects, including loss of body weight. These results describe the molecular mechanisms whereby the WEGS might inhibit proliferation of colon cancer both in vitro and in vivo, suggesting that WEGS has potential as an anticancer agent for the treatment of malignancies. Copyright © 2010 John Wiley & Sons, Ltd.

Malfunctions or critical fatigue problems often occur in mistuned periodic structural systems since their vibration responses may become much larger than those of perfectly tuned periodic systems. These are called vibration localization phenomena and it is of great importance to accurately predict the localization phenomena for safe and reliable designs of the periodic structural systems. In this study, a simple discrete system which represents periodic structural systems is employed to analyze the vibration localization phenomena. The statistical effects of mistuning, stiffness coupling, and damping on the vibration localization phenomena are investigated through Monte Carlo simulation. It is found that the probability of vibration localization was significantly influenced by the statistical properties except the standard deviation of coupling stiffness.