• Journal of the Korean housing association
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• v.17 no.3
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• pp.61-69
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• 2006

Vertical vibrations on the slab of buildings are affected by types of vibration sources, transfer paths, and the material property and the size of members. Among these parameters, the vibration sources and the transfer path can not be controlled, but the property and the size of members can be controlled in the phase of design the members. In this study, the vibration responses according to the property and size of members were obtained by using a prediction program based on dynamic-stiffness matrix. Three parameters which are not usually considered as major factors for architecral planning were selected fur these analyses. They are the strength of materials, the thickness of wall and the thickness of slab. The ground vibration source located near a building was used as vibration input data in the analyses. This study has its originality on presenting appropriate property and size of structural members in order to reduce vertical vibration of slab in shear-wall structures. Analysing the results from the vibration estimation program according to the variations of parameters, the appropriate ratio among the sizes of structural members were proposed. From these results, the vibration level on the slab which is not constructed yet would be predicted and the vibration peak level can be reduced or shifted into the desirable frequency range. Therefore, the vertical vibration could be controlled in the phase of designing buildings.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.761-771
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• 1998

In this study, attempt has been made to evaluate the effect of $CO_2$ laser irradiation on enamel surface structure and the bond strength of sealant material. Conventional acid etching was used as a control technic for comparison. The results obtained from this experiment were as follows; 1. The highest mean shear bond strength value was observed in samples of Group I (acid-etching) with the statistical significance(p<.05) between all the other groups. 2. The shear bond strength in Group IV was the lowest among laser etching groups. but there were no significant difference between them(p>.05). 3. Scanning electron microscopic observation showed that the rough and irregular surface was created by $CO_2$ laser treatment with the formation of numerous pores, micro-cracks, and small bubble-like inclusion. Increasing the energy density induced localized surface melt with a thin smooth glaze-like appearance. 4. In acid-etched control specimen cohesive failure predominated, whereas adhesive failure was the main mode in laser-treated group. Based upon the above-mentioned results, it can be assumed that the $CO_2$ laser is not an adequate substitute for the acid-etch technique in enamel preconditioning. More studies are required to explore the effective condition of laser irradiation which could attain the better bond strength of restorative materials.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.805-816
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• 2010

For earthquake simulation test it is essential to make sure the similitude in behaviors between the full scale prototype and the reduced scale model. This paper presents the test results obtained through the cyclic lateral-force test, on two-story RC wall subassemblages. A lower 2-story portion of the prototype structure was selected as subassemblages. The global behavior such as the strength and ductility, and the local behavior such as flexural, shear and uplift deformation were measured. The test results of the 3 : 5 scale specimens representing the prototype were compared with those of 1 : 7 scale models. Two types of subassemblages were used: One with lintel beams and one without lintel beams. The comparison shows that 1 : 7 scale model simulated in general successfully the global and local behaviors of the prototype.

• Proceedings of the Korean Geotechical Society Conference
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• 1988.06c
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• pp.3-67
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• 1988

Model studies on the response of homgeneous earth embankment dams subjected to strike-slip fault movement have been penomed via centrifuge and finite element analysis. The centrifuge model tests have shown that crack development in earth embankment experiences two major patters: shear failure deep inside the embankment and tension failure near the surface. The shear rupture zone develops from the base level and propagates upward continuously in the transverse direction but allows no open leakage chnnel. The open tensile cracks develop near the surface of the embankment, but they disappear deep in the embankment. The functional relationship has been developed based on the results of the centrifuge model tests incorporating tile variables of amount of fault movement, embankment geometry, and crack propagation extent in earth des. This set of information can be used as a guide line to evaluate a "transient" safety of the duaged embankment subjected to strike-slip fault movement. The finite element analysis has supplemented the additional expluations on crack development behavior identified from the results of the centrifuge model tests. The bounding surface time-independent plasticity soil model was employed in the numerical analysis. Due to the assumption of continuum in the current version of the 3-D FEM code, the prediction of the soil structure response beyond the failure condition was not quantitatively accurate. However, the fundamental mechanism of crack development was qualitatively evaluated based on the stress analysis for the deformed soil elements of the damaged earth embankment. The tensile failure zone is identified when the minor principal stress of the deformed soil elements less than zero. The shear failure zone is identified when the stress state of the deformed soil elements is at the point where the critical state line intersects the bounding surface.g surface.

• Computers and Concrete
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• v.19 no.4
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• pp.365-374
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• 2017

With the continuous evolution of the numerical methods and the availability of advanced constitutive models, it became a common practice to use complex physical and geometrical nonlinear numerical analyses to estimate the structural behavior of reinforced concrete elements. Such simulations may yield the complete time history of the structural behavior, from the first moment the load is applied until the total collapse of the structure. However, the evolution of the cracking pattern in geometrical discontinuous zones of reinforced concrete elements and the associated failure modes are relatively complex phenomena and their numerical simulation is considerably challenging. The objective of the present paper is to assess the applicability of the Applied Element Method in simulating the development of distinct failure modes in reinforced concrete walls subjected to monotonic loading obtained in experimental tests. A pushover test was simulated numerically on three distinct RC shear walls, all presenting an opening that guarantee a geometrical discontinuity zone and, consequently, a relatively complex cracking pattern. The presence of different reinforcement solutions in each wall enables the assessment of the reliability of the computational model for distinct failure modes. Comparison with available experimental tests allows concluding on the advantages and the limitations of the Applied Element Method when used to estimate the behavior of reinforced concrete elements subjected to monotonic loading.

• Computers and Concrete
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• v.21 no.5
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• pp.495-504
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• 2018

The possibility of earthquakes in vulnerable regions indicates that efficient technique is required for seismic protection of buildings. During the recent decades, the concept is moving towards the insertion of base isolation on seismic prone buildings. So, investigation of structural behavior is a burning topic for buildings to be isolated in base level by bearing device. This study deals with the incorporation of base isolation system and focuses the changes of structural responses for different types of Lead Rubber Bearing (LRB) isolators. A number of sixteen model buildings have been simulated selecting twelve types of bearing systems as well as conventional fixed-base (FB) scheme. The superstructures of the high-rise buildings are represented by finite element assemblage adopting multi-degree of freedoms. Static and dynamic analyses are carried out for FB and base isolated (BI) buildings. The dynamic analysis in finite element package has been performed by the nonlinear time history analysis (THA) based on the site-specific seismic excitation and compared employing eminent earthquakes. The influence of the model type and the alteration in superstructure behavior of the isolated buildings have been duly assessed. The results of the 3D multistory structures show that the lateral forces, displacement, inertia and story accelerations of the superstructure of the seismic prone buildings are significantly reduced due to bearing insertion. The nonlinear dynamic analysis shows 12 to 40% lessening in base shear when LRB is incorporated leading to substantial allowance of horizontal displacement. It is revealed that the LRB isolators might be potential options to diminish the respective floor accelerations, inertia, displacements and base shear whatever the condition coincides. The isolators with lower force intercept but higher isolation period is found to be better for decreasing base shear, floor acceleration and inertia force leading to reduction of structural and non-structural damage. However, LRB with lower isolator period seems to be more effective in dropping displacement at bearing interface aimed at reducing horizontal shift of building structure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1417-1426
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• 2001

Turbulent flow characteristics in the near wake of a square cylinder have been studied experimentally by using a Digital PIV method. Experiments are performed at the Reynolds numbers of 1600 and 3900 based on the free-stream velocity and the square height. The ensemble averaged turbulence statistics are acquired from 2030 realizations of instantaneous fluctuating velocity field after the conventional Reynolds decomposition. The differences in turbulent intensity and Reynolds shear stress profiles fur both oases indicate that the effect of Reynolds number seems to be descernible mainly due to the occurrence of transition in the separated shear layer. Because of the periodic nature of vortex shedding process, transverse velocity fluctuations contribute dominantly , to turbulent kinetic energy distribution. A comparison with previous LDV data obtained at much higher Reynolds number shows a fairly good agreement each other. It turns out that the effect of Reynolds number diminishes as increasing Reynolds number, which is a well-known feature of a sharp-edged bluff body wake. The streamwise variation of turbulence intensities are compared with those from a circular cylinder along the centerline at the same Reynolds number. The overall magnitudes and the decay rates of turbulence intensities are quite similar, but some differences are noticeble especially in the transverse intensity variation.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.127-131
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• 2004

Package reliability test was conducted to investigate the effect of solder composition on the ball fatigue strength for BGA (Ball Grid Array) packaging. The test pieces are assembled using eutectic composition 63Sn/37Pb, 62Sn/36Pb/2Ag, and 63Sn/34.4Pb/2Ag/0.5Sb solder after pre-conditioning at MRT Lv 3 (Moisture Resistance Test Level) and then conducted under T/C (Temperature Cycle test). For each case, the ball shear strength was obtained and micro structure photos were taken. SEM (scanning electron microscope) and EDX (Energy Dispersive X-ray) were used to the analyze failure mechanism. The growth rate of Au-Sn intermetallic compound in Sn63Pb34.5Ag2Sb0.5 solder was slow when compared to 63Sn/37Pb solder and 62Sn/36Pb/2Ag solder. The degradation of shear strength of solder balls caused by solder composition was discussed.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.153-160
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• 2015

This article is aimed to study the effects of resistance spot welding (RSW) on the lap joint properties between AA1100 aluminum alloy and SGACD zinc coated steel and its properties. The summarized experimental results are as follows. The summarized experimental results are as follows. The optimum welding parameters that produced maximum tensile shear strength of 2200 N was a welding current of 95 kA, a holding time of 10 cycles, and a welding pressure of 0.10 MPa. Increasing of welding current, increased the tensile shear strength of the joint and also increased the amount of aluminum dispersion at the joint interface. The lap joint of steel over the aluminum (Type I) showed the higher joint tensile shear strength than a lap joint of aluminum over the steel (Type II). The indentation depth and the ratio of the indentation depth to the plate thickness decreased when the welding current was increased in the type I lap joint and also decreased when the welding current was decreased in the type II lap joint. The interface structure showed the formation of the brittle $FeAl_3$ intermetallic compound that deteriorated the joint strength.

• Steel and Composite Structures
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• v.19 no.6
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• pp.1403-1419
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• 2015

When precast concrete infill panels are connected to steel frames at discrete locations, interaction at the structural interface is neither complete nor absent. The contribution of precast concrete infill panels to the lateral stiffness and strength of steel frames can be significant depending on the quality, quantity and location of the discrete interface connections. This paper presents preliminary experimental and finite element results of an investigation into the composite behaviour of a square steel frame with a precast concrete infill panel subject to lateral loading. The panel is connected at the corners to the ends of the top and bottom beams. The Frame-to-Panel-Connection, FPC4 between steel beam and concrete panel consists of two parts. A T-section with five achor bars welded to the top of the flange is cast in at the panel corner at a forty five degree angle. The triangularly shaped web of the T-section is reinforced against local buckling with a stiffener plate. The second part consists of a triangular gusset plate which is welded to the beam flange. Two bolts acting in shear connect the gusset plate to the web of the T-section. This way the connection can act in tension or compression. Experimental pull-out tests on individual connections allowed their load deflection characteristics to be established. A full scale experiment was performed on a one-storey one-bay 3 by 3 m infilled frame structure which was horizontally loaded at the top. With the characteristics of the frame-to-panel connections obtained from the experiments on individual connections, finite element analyses were performed on the infilled frame structures taking geometric and material non-linear behaviour of the structural components into account. The finite element model yields reasonably accurate results. This allows the model to be used for further parametric studies.