• Steel and Composite Structures
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• 제45권3호
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• pp.437-454
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• 2022

Elliptic-braced simple resisting frame as a new lateral bracing system installed in the middle bay of frame in building facades has been recently introduced. This system not only creates a problem for opening space from the architectural viewpoint but also improves the structural behavior. Despite the researches on the seismic performance of lateral bracing systems, there are few studies performed on the effect of the stiffness parameters on the elastic story drift and calculation of period in simple braced steel frames. To overcome this shortcoming, in this paper, for the first time, an analytical solution is presented for calculating elastic lateral stiffness in a simple steel frame equipped with elliptic brace subjected to lateral load. In addition, for the first time, in this study, a precise formulation has been developed to evaluate the elastic stiffness variation in a steel frame equipped with a two-dimensional single-story single-span elliptic brace using strain energy and Castigliano's theorem. Thus, all the effective factors, including axial and shear loads as well as bending moments of elliptic brace could be considered. At the end of the analysis, the lateral stiffness can be calculated by an improved and innovative relation through the energy method based on the geometrical properties of the employed sections and specification of the used material. Also, an equivalent element of an elliptic brace was presented for the ease of modeling and use in linear designs. Application of the proposed relation have been verified through a variety of examples in OpenSees software. Based on the results, the error percentage between the elastic stiffness derived from the developed equations and the numerical analyses of finite element models was very low and negligible.

• Preventive Nutrition and Food Science
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• 제6권3호
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• pp.163-169
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• 2001

To produce expanded, minimally hard extrudates from blends of raw pork meat (20%), defatted soy flour (25%), and corn starch using a single-screw extruder, various combinations of feed moisture, process temperature, and screw speed were evaluated. First series of extrusion runs were conducted according to a central composite rotatable design/response surface methodology (RSM). Upon assessing the full model for each response, insignificant terms were eliminated to determine final response surface models. Screw speed within the range evaluated was found to have no significant effect on expansion ratio (ER) or shear force (SF) of extrudates. Since examinations of the response surfaces and their generated grids of predicted values indicated that maximum ER and minimum SF were likely to be attained with a moisture-temperature combination outside the RSM experimental range, the second series of extrusion runs were conducted with several selected combinations of moisture and temperature to determine a practical optimum extrusion condition. The combination of 22.78% feed moisture, 16$0^{\circ}C$ process temperature, and 170 rpm screw speed was chosen as such a condition, and used in the final extrusion. The final product required less force to break than did commercial pretzel sticks.

• Preventive Nutrition and Food Science
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• 제6권3호
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• pp.158-162
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• 2001

Blends of pork meat (20%), defatted soy flour (25%), and corn starch (48.61~53.71%) were prepared with or without additional non-meat ingredients, i.e., onion powder (1%), alone or in combination with carrot powder (1.5%) or extract (1.5%), or defatted oat flour (5%). All blends were formulated for 22.78% moisture, with water added where necessary. They were extruded using a laboratory single-screw extruder at 16$0^{\circ}C$ profess temperature and 170 rpm screw speed. The additional ingredients generally decreased product expansion and increased bulk density and shear force. When the product with no additional ingredient and the product with onion powder were evaluated by trained sensory panelists, \"grain complex\" was the most intense flavor note for both. With 1 % onion powder in feed, a distinct \"onion\" flavor note was detectable in extrudates. All the products may be considered \"healthful\" based on nutrient profiles.t; based on nutrient profiles.

• 대한기계학회논문집A
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• 제32권4호
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• pp.354-361
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• 2008

Cold rolled steel sheet for automotive was treated by Ar/$O_2$ atmospheric pressure plasma to improve the adhesive bonding strength. Through the contact angle test and calculation of surface free energy for cold rolled steel sheet, the changes of surface properties were investigated before and after plasma treatment. The contact angle was decreased and surface free energy was increased after plasma treatment. And the change of surface roughness and morphology were observed by AFM(Atomic Force Microscope). The surface roughness of steel sheet was slightly changed. Based on Taguchi method, single lap shear test was performed to investigate the effect of experimental parameter such as plasma power, treatment time and flow rate of $O_2$ gas. Results shows that the bonding strength of steel sheet treated in Ar/$O_2$ atmospheric pressure plasma was improved about 20% compared with untreated sheet.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.855-863
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• 2009

In this study, a beam-column junction type damper is proposed which saves the inner and outer space for the installation of damping devices and allows easy adjustment of control performance The result of the numerical analysis indicated that the displacement response and base shear of a single degree of freedom system by seismic load, El Centro 1940 was reduced with yield moment of the joint hinge and the specific yield moment ratio $\delta$ of the joint hinge existed for the optimal seismic performance. In addition, the dynamic nonlinear characteristics, effects of yielding and dependence of natural period of bi-linear system with the junction type damper is identified. The analysis of multi-degree of freedom system showed that responses of the controlled structures was reduced significantly as the number of a story increases and yield moment ratio decreases when the system is excited by seismic load and sine wave. On top of that, it was also observed that energy dissipation at the joint connected with the dampers was remarkable during excitation.

• Structural Engineering and Mechanics
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• 제18권3호
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• pp.343-362
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• 2004

Rocking response of rigid bodies with rectangular footprint, freely standing on horizontal rigid plane is studied analytically. Bodies are subjected to simulated single component of horizontal earthquakes. The effect of baseline correction, applied to simulated excitations, on the rocking response is first examined. The sensitiveness of rocking motion to the details of earthquakes and geometric properties of rigid bodies is investigated. Due to the demonstrated sensitivity of rocking response to these factors, prediction of rocking stability must be made in the framework of probability theory. Therefore, using a large number of simulated earthquakes, the effects of duration and shape of intensity function of simulated earthquakes on overturning probability of rigid bodies are studied. In the case when a rigid body is placed on any floor of a building, the corresponding probability is compared to that of a body placed on the ground. For this purpose, several shear frames are employed. Finally, the viability of the energy balance equation, which was introduced by Housner in 1963 and widely used by nuclear power industry to estimate the rocking stability of bodies, is evaluated. It is found that the equation is robust. Examples are also given to show how this equation can be used.

• 접착 및 계면
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• 제6권1호
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• pp.1-6
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• 2005

The high accurate simulation of very thin glue layers based on the finite element method is still connected to many problems which result from the necessity to construct a complicated mesh of essentially different sizes of elements. This can lead to a loss of accuracy, unstable calculations and even loss of convergence. However, the implementation of special transmission elements along the glue ling and special edge-elements in the near-edge region would lead to a dramatic decrease of number of finite elements in the mesh and thus, prevent unsatisfactory phenomena in numerical analysis and extensive computation time. The theoretical basis for such special elements is the knowledge about appropriate transmission conditions and the edge effects near the free boundary of the adhesive layer. Therefore, recently proposed so-called non-classical transmission conditions and the behavior near the free edge are investigated in the context of the single-lap tensile-shear test of adhesive technology.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.505-511
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• 2018

Recently, a new foundation model called "Dynamic foundation model" was proposed for the dynamic analysis of structures on the foundation. This model includes a linear elastic spring, shear layer, viscous damping and the special effects of mass density parameter of foundation during vibration. However, the relationship of foundation property parameters with the experimental parameter of the influence of foundation mass also has not been established in previous research. Hence, the purpose of the paper presents a simple experimental model in order to establish relationships between foundation properties such as stiffness, depth of foundation and experimental parameter of the influence of foundation mass. The simple experimental model is described by a steel plate connected with solid rubber layer as a single degree of freedom system including an elastic spring connected with lumped mass. Based on natural circular frequencies of the experimental models determined from FFT analysis plots of the time history of acceleration data, the experimental parameter of the influence of foundation mass is obtained and the above relationships are also discussed.

• Structural Engineering and Mechanics
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• 제66권5호
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• pp.637-648
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• 2018

When the centers of mass and stiffness of a building do not coincide, the structure experiences torsional responses. Such systems can consist of the underlying soil and the super-structure. The underlying soil may modify the earthquake input motion and change structural responses. Specific effects of the input motion shall also not be ignored. In this study, seismic demands of asymmetric buildings considering soil-structure interaction (SSI) under near-fault ground motions are evaluated. The building is modeled as an idealized single-story structure. The soil beneath the building is modeled by non-linear finite elements in the two states of loose and dense sands both compared with the fixed-base state. The infinite boundary conditions are modelled using viscous boundary elements. The effects of traditional and yield displacement-based (YDB) approaches of strength and stiffness distributions are considered on seismic demands. In the YDB approach, the stiffness considered in seismic design depends on the strength. The results show that the decrease in the base shear considering soft soil induced SSI when the YDB approach is assumed results only in the center of rigidity to control torsional responses. However, for fixed-base structures and those on dense soils both centers of strength and rigidity are controlling.

• Steel and Composite Structures
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• 제23권5호
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• pp.529-541
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• 2017

In the present study, vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) plate moving in two directions is investigated. Various types of shear deformation theories are utilized to obtain more accurate and simplest theory. Single-walled carbon nanotubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Moreover, different kinds of distributions of CNTs are considered. Based on extended rule of mixture, the structural properties of composite face sheets are considered. Motion equations are obtained by Hamilton's principle and solved analytically. Influences of various parameters such as moving speed in x and y directions, volume fraction and distribution of CNTs, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of composite plate on the vibration characteristics of moving system are discussed in details. The results indicated that thenatural frequency or stability of FGCNTRC plate is strongly dependent on axially moving speed. Moreover, a better configuration of the nanotube embedded in plate can be used to increase the critical speed, as a result, the stability is improved. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.