• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.23-31
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• 1992

In this study, Behavior of Eccentrically Loaded Restrained Concrete Slender Columns are investigated the continuation. The paper is : nonlinear constitutive relations of reinforced concrete columns are formulated, the multivariable nonlinear equation formulated in this study is solved by the incremental iterative method, the solution scheme is suitable for computer application, the proposed method bas been compared with the numerical examples and other research results and is shown to be in good agreement Accordingly, the objectives of this investigation are to use the method developed to conduct a parametric study of the different variable (Rotational Restraints,Ratio of End Restraints. End Eccentricity, Ratio of End Eccentricities,Lateral Restraint, Concrete Strength, Ratio of Reinforcement. Yield Point of Reinforcement) influencing the behavior and the ultimate strength for columns. Chosen values for different parameters and their variations are based on values encountered in practice and on results of other analylitical studies.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.515-525
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• 2019

The calculation of active earth pressure behind retaining wall is a typical three-dimensional (3D) problem with spatial effects. With the help of limit analysis, this paper firstly deduces the internal energy dissipation power equations and various external forces power equations of the 3D retaining wall under the nonlinear strength condition, such as to establish the work-energy balance equation. The pseudo-static method is used to consider the effect of earthquake on active earth pressure in horizontal state. The failure mode is a 3D curvilinear cone failure mechanism. For the different width of the retaining wall, the plane strain block is inserted in the symmetric plane. By optimizing all parameters, the maximum value of active earth pressure is calculated. In order to verify the validity of the new expressions obtained by the paper, the solutions are compared with previously published solutions. Agreement shows that the new expressions are effective. The results of different parameters are given in the forms of figures to analysis the influence caused by nonlinear strength parameters.

• Steel and Composite Structures
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• v.46 no.5
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• pp.591-609
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• 2023

In some buildings, the lateral structural response of steel framed buildings depends on the shear walls and it is very important to study the behavior of these elements under near-field seismic loads. The link beam in the opening of the shear wall between two wall plates is investigated numerically in terms of behavior and effects on frames. Based on the length of the beam and its bending and shear behavior, three types of models are constructed and analyzed, and the behavior of the frames is also compared. The results show that by reducing the length of the link beam, the base shear forces reduce about 20%. The changes in the length of the link beam have different effects on the degree of coupling. Increasing the length of the link beam increases the base shear about 15%. Also, it has both, a positive and a negative effect on the degree of coupling. The increasing strength of the coupling steel shear wall is linearly related to the yield stress of the beam materials, length, and flexural stiffness of the beam. The use of a shorter link beam will increase the additional strength and consequently improving the behavior of the coupling steel shear wall by reducing the stresses in this element. The link beam with large moment of inertia will also increase about 25% the additional strength and as a result the coefficient of behavior of the shear wall.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.67-74
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• 2016

With several different dosages of multi-walled CNTs which was 0.1, 0.3, and 0.5% of the weight of binder, the fluidity in fresh CNT cement composites, as well as the strength and strength development with age of the hardened composites were investigated in this experimental study. The experimental results from flow test indicated that the increase in the dosage of CNTs badly impacted on the workability of fresh composites, and the results from rheological measurements presented the decrease in plastic viscosity and the increase in yield stress according to the amount of CNTs. In addition, the thixotrophy in the flow curve obtained from the rheology test was observed more noticeably in the composites with higher dosage of CNTs. With the experiments on the strength properties, the improvement of both compressive and tensile strengths with the increase of CNTs dosage could be obtained. Moreover, early strength development by adding CNTs was found when it was compared with plain cementious matrix without CNT.

• Earthquakes and Structures
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• v.12 no.1
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• pp.23-34
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• 2017

Composite steel plate deep beam (CDB) is proposed as a lateral resisting member, which is constructed by steel plate and reinforced concrete (RC) panel, and it is connected with building frame through high-strength bolts. To investigate the seismic performance of the CDB, tests of two 1/3 scaled specimens with different length-to-height ratio were carried out under cyclic loads. The failure modes, load-carrying capacity, hysteretic behavior, ductility and energy dissipation were obtained and analyzed. In addition, the nonlinear finite element (FE) models of the specimens were established and verified by the test results. Besides, parametric analyses were performed to study the effect of length-to-height ratio, height-to-thickness ratio, material type and arrangement of RC panel. The experimental and numerical results showed that: the CDBs lost their load-carrying capacity because of the large out-of plane deformation and yield of the tension field formed on the steel plate. By increasing the length-to-height ratio of steel plate, the load-carrying capacity, elastic stiffness, ductility and energy dissipation capacity of the specimens were significantly enhanced. The ultimate loading capacity increased with increasing the length-to-height ratio of steel plate and yield strength of steel plate; and such capacity increased with decreasing of height-to-thickness ratio of steel plate and gap. Finally, a unified formula is proposed to calculate their ultimate loading capacity, and fitting formula on such indexes are provided for designation of the CDB.

• Korean Journal of Metals and Materials
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• v.56 no.11
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• pp.796-804
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• 2018

The Charpy impact toughness of the heat affected zone (HAZ) of electro gas welded 390 MPa yield strength grade steel, manufactured by a thermo mechanically controlled process, was investigated. The effects of added Nb on the toughness of the steel and the factors influencing scatter in toughness are discussed in the present work. It was observed that adding Nb to the steel led to the deterioration of HAZ toughness. The presence of soluble Nb in the HAZ increased its hardenability and resulted in a larger amount of low toughness bainitic microstructure. Microstructural observations in the notch root area revealed the significant role of different microstructures in the area. In the presence of a larger amount of bainitic microstructures, the HAZ exhibited a lower Charpy toughness with a larger scatter in toughness. A softened zone with a lower hardness than the base metal was formed in the HAZ. However, theoretical analysis revealed that the presence of the zone might not be a problem in a real welded joint because of the plastic restraint effect enforced by surrounding materials.

• International Journal of Industrial Entomology and Biomaterials
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• v.39 no.1
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• pp.9-13
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• 2019

In this study, 4 different types of GBR membrane were undergone for bio-degradability test; Silk mat from silkworm cocoon (TDI), silk mat from flatwise-spun (FS), collagen membrane (OssGuide), and dPTFE membrane (Cytoplast). Each material was segmented in 10.00 mm length and 0.3 mm thickness. The samples were put into the normal saline at $37^{\circ}C$ for 2 weeks. After that, yield strength and tensile strain were measured and compared them with those of before treatment. The morphology of the membranes was observed by SEM. Tensile strain of FS was significantly increased at 2 weeks' normal saline treatment (P=0.018). When compared to OssGuide, TDI and FS showed significantly higher tensile strain at 2 weeks' normal saline treatment (P<0.05). In the SEM images, there were no significant changes in Cytoplast, TDI, and FS after 2 weeks' treatment. However, OssGuide showed damaged surface after 2 weeks' treatment. In conclusion, both TDI and FS did not have any evidence of biodegradability at 2 weeks' observation in normal saline treatment. However, OssGuide showed more than 20 % decrease in yield strength and tensile strain.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3229-3240
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• 2023

Due to neutron radiation, atomic displacement has a significant effect on material in nuclear reactors. A range of secondary displacement models, including the Kinchin-Pease (K-P), Lindhard, Norgett-Robinson-Torrens (NRT), and athermal recombination-corrected displacement per atom (arc-dpa) have been suggested to calculate the number of displacement per atom (dpa). As neutron elastic interaction is the main cause of displacement damage, the focus of the current study is to calculate the atomic displacement caused by the neutron elastic interaction in order to estimate the exact amount of yield strength in a WWER-1000 reactor pressure vessel. To achieve this purpose, the reactor core is simulated by MCNPX code. In addition, a program is developed to calculate the elastic radiation damage induced by the incident neutron flux (RADIX) based on different models using Fortran programming language. Also, due to non-elastic interaction, the displacement damage is calculated by the HEATR module of the NJOY code. ASME E-693-01 standard, SPECTER, NJOY codes, and other pervious findings have been used to validate RADIX results. The results showed that the RADIX(arc-dpa)/HEATR outputs have appropriate accuracy. The relative error of the calculated dpa resulting from RADIX(arc-dpa)/HEATR is about 8% and 46% less than NJOY code, respectively in the ¼ and ¾ vessel wall.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.715-723
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• 2017

This study investigates the properties of a high-performance cementitious composite with partial substitution of stone dust for fine aggregate. The relationship between the properties and particle size distribution was analyzed using several analytical models. Experiments were carried out to examine the flowability, rheology, and strength of cement mortars with different stone-dust replacement ratios of 0-30 wt.%. The results showed improved flowability, lower rheological parameters (yield stress and plastic viscosity), and improved strength as the amount of stone dust increased. These results are closely related to the packing density of the solid particles in the mortar. The effect was therefore estimated by introducing an optimum particle size distribution (PSD) model for maximum packing density. The PSD with a higher amount of stone dust was closer to the optimum PSD, and the optimization was quantified using RMSE. The improvement in the PSD by the stone dust was proven to affect the flowability, strength, and plastic viscosity based on several relevant analytical models. The reduction in yield stress is related to the increase of the average particle diameter when using stone dust.

• Journal of the Korean Society of Safety
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• v.7 no.1
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• pp.65-72
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• 1992

Objective of this research is to evaluate fracture behaviors of fresh-butt welded metal by the acoustic emission technique. The specimens used are medium carbon steel(SM45C), mild steel (SS41) and stainless steel(SUS304), which have different weldability. The similar welding and dissimilar welding processes are considered, in the former SM45C, SS41 and SUS304 are used, in the later the following metals are used SM45C and SS41, SM45C and SUS304 and SS41 and SUS304. The characteristics of fracture in weld metal are eshmated by the tension test with nominal speciemns, the fracture toughness test with compact tension specimens and fractography analysis. The results of tension test show for base metals and similar welding materials that the yield strength and ultimate strength of similar welding materials are increased, the elongation of those are decreased. The weldability of SUS304 is better than that of SM45C and SS41 In similar welding materials. Mechanical properties of dissimilar welding mateiiths we lower than those of similar welding materials. In dissimilar welding materials, the weldability of SM45C and SUS304 is better than that of SM45C and SS41, and also weidability of SS41 and SUS304 is better than SS41 and SM45C. Comparing mechanical properties with AE counts, it is found that AE conuts appeared on a small before the limit load of elasticity(P$_{e}$), and apper greatly near yield strength region in tension test. These results could contribute to the safety analyses and the evaluation of strength for welding structure.e.