• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2540-2545
• /
• 2007

A computational study of BLDC motor is presented to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet and the inflow rates are predicted more at the front-side inlet than at the rear-side, which can be ascribed to the different pressure distribution. Recirculation zone appears in the tiny interfaces between windings, however, showing the enhanced cooling performance due to the higher velocity distribution near the rotor wall. In contrast, flow separation and incline angle of bearing groove, and relatively slower velocity distribution cause poor cooling performance and therefore the redesign of the bearing groove is significantly required.

• Earthquakes and Structures
• /
• v.6 no.2
• /
• pp.181-199
• /
• 2014

The infill walls, whose contribution to the earthquake resistance of a structure is generally ignored due to their limited lateral rigidities, constitute a part of the lateral load bearing system of an RC frame structure. A common method for improving the earthquake behavior of RC frame structures is increasing the contribution of the infill walls to the overall lateral rigidity by strengthening them through different techniques. The present study investigates the influence of externally bonded perforated steel plates on the load capacities, rigidities, and ductilities of hollow brick infill walls. For this purpose, a reference (unstrengthened) and twelve strengthened specimens were subjected to monotonic diagonal compression. The experiments indicated that the spacing of the bolts, connecting the plates to the wall, have a more profound effect on the behavior of a brick wall compared to the thickness of the strengthening plates. Furthermore, an increase in the plate thickness was shown to result in a considerable improvement in the behavior of the wall only if the plates are connected to the wall with closely-spaced bolts. This strengthening technique was found to increase the energy absorption capacities of the walls between 4 and 14 times the capacity of the reference wall. The strengthened walls reached ultimate loads 30-160% greater than the reference wall and all strengthened walls remained intact till the end of the test.

• Geotechnical Engineering
• /
• v.4 no.2
• /
• pp.15-24
• /
• 1988

To identify the stability of cantilever retaining wall in safe state by the deterministic method, these potential modes of such geotechnical failures as bearing capacity, horizontal sliding and overturning are analysed using Advanced First Order Second Moment (AFOSM) method. All design variables are assumed of the normal distribution and to be statistically independent. Considering the correlations between the single modes, structural system reliability index is 2. 05. Even if the safety factors are larger than the required value in the codes' by the conventional deterministic method, the system reliability of this structure may not be Judged to be safe state since the system reliability index is much lower than general value of 3.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.12 no.1
• /
• pp.81-88
• /
• 2012

According to the survey results of the Ministry of Land, Transport and Maritime Affairs in the end of December 2011, the residential buildings was reported as 67.3% of 4,529,464 buildings. Reflected in the national energy policy, the residential building is expected that greater energy savings. To have realized the Passive House Project used the Autoclaved Lightweight Concrete(ALC) material on exterior wall, we take advantage of a very large energy savings. Therefore, this study investigate the patent documents of three major companies, SUMITOMO, CLION, ASAHI KASEI, in Japan. and analyze technical flow and benchmarking patent. As a result, the Sliding method or the Rocking method of ALC panels how to install is to be superior to high-performance drift and safety by a earthquake. And the embedded anchor in panel needs to improve the shape and the strength of bearing. Thus installation technology of the ALC exterior wall investigated in japanese patent documents is expected to the fastening units and anchors.

• Structural Engineering and Mechanics
• /
• v.26 no.3
• /
• pp.277-295
• /
• 2007

3-D wall panels are used in construction of exterior and interior bearing and non-load bearing walls and floors of building of all types of construction. Fast construction, thermal insulation, reduced labor expense and weight saving are the most well pronounced advantage of such precast system. When the structural performance is concerned, the main disadvantage of 3D panel, when used as floor slab, is their brittleness in flexure. The current study focuses on upgrading ductility and load carrying capacity of 3D slabs in two different ways; using additional tension reinforcement, and inserting a longitudinal concentrated beam. The research is carried on both experimentally and numerically. The structural performance in terms of load carrying capacity and flexural ductility are discussed in details. The obtained results could give better understanding and design consideration of such prefabricated system.

• Journal of Mechanical Science and Technology
• /
• v.17 no.6
• /
• pp.844-853
• /
• 2003

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gumbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.

• Journal of the Korean Society of Safety
• /
• v.16 no.3
• /
• pp.89-98
• /
• 2001

There have been a lot of studies about repair & strengthening of the concrete structure. But there has almost not been my study on section damage effect due to holes drilled out for installing additional facilities or equipment, such as rack on the wall of building or underground culvert system, plumbing system through the column or wall of it, after being occupied. This study is to find out how much the section loss due to holes will give loss of section strength. We cm determine if we repair or reinforce it completely or not, using strength loss from the hole. Hole size of diameter 3cm, 2cm, lcm, depth of 3cm, 5cm, 10cm, and position of each hole has been considered as variables of this study. It is concluded that section loss 30% results in 53% of strength damage.

• Computers and Concrete
• /
• v.22 no.3
• /
• pp.279-289
• /
• 2018

Shear walls are one of the important structural elements for bearing loads imposed on buildings due to winds and earthquakes. Composite shear walls with high lateral resistance, and high energy dissipation capacity are considered as a lateral load system in such buildings. In this paper, a composite shear wall consisting of steel faceplates, infill concrete and tie bars which tied steel faceplates together, and concrete filled steel tubular (CFST) as boundary columns, was modeled numerically. Test results were compared with the existing experimental results in order to validate the proposed numerical model. Then, the effects of some parameters on the behavior of the composite shear wall were studied; so, the diameter and spacing of tie bars, thickness and compressive strength of infill concrete, thickness of steel faceplates, and the effect of strengthening the bottom region of the wall were considered. The seismic behavior of the modeled composite shear wall was evaluated in terms of stiffness, ductility, lateral strength, and energy dissipation capacity. The results of the study showed that the diameter of tie bars had a trivial effect on the performance of the composite shear wall, but increasing the tie bars spacing decreased ductility. Studying the effect of infill concrete thickness, concrete compressive strength, and thickness of steel faceplates also showed that the main role of infill concrete was to prevent buckling of steel faceplates. Also, by strengthening the bottom region of the wall, as long as the strengthened part did not provide a support performance for the upper part, the behavior of the composite shear wall was improved; otherwise, ductility of the wall could be reduced severely.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.1001-1009
• /
• 2005

The usefulness of walls in the structural planning of multistory buildings has long been recognized. When walls are situated in advantageous positions in a buildings, they can be very efficient in resisting lateral load. Specially coupled shear wall system is the primary lateral load resisting system of buildings. It is customary to refer to such walls as being 'coupled' by coupling beams. The coupling beams must exhibit excellent strength, stiffness ductility and energy dissipation capacity. To achieve these demands for steel coupling beam, steel coupling beam with Face Bearing Plate(FBP) embedded in the reinforced concrete walls is proposed. A comprehensive experimental test involving 2 steel coupling beam with and without FBP has been performed. Through experimental study, the evaluation of the advantage of that was establish and proposed the failure mode.

• Structural Engineering and Mechanics
• /
• v.40 no.6
• /
• pp.763-782
• /
• 2011

Results from nonlinear time-history analyses of wall-frame structural models indicate that the condition of vulnerable foundations -for which uplifting and reaching the bearing capacity of the supporting soil can occur before yielding at the base of the shear walls- may not be necessarily detrimental to the drift response of buildings under strong ground motions. Analyses also show that a soil-foundation system can inherently have deformation capacity well in excess of the demand and thus act as a source of energy dissipation that protects the structural integrity of the shear walls.