• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.2
• /
• pp.231-240
• /
• 1988

An investigation is carried out for the load capacity characteristics of the externally pressurized air lubricated journal bearings both theoretically and experimentally. Theoretical analysis is made using the incremental method and the finite element method, and the discharge coefficient is considered. The experiments are performed for five bearings which are produced according to the rows of supply holes and the presence of poket or step. The results are compared with the numerical results. The present numerical results are in better agreement with the available experimental results than any other earlier numerical results for the bearings having one row and two rows of supply holes with pocket. The present numerical and experimental results show that the bearing with step has larger load capacity than that without step and that the load capacity increases as the clearance ratio increases.

• Membrane and Water Treatment
• /
• v.11 no.2
• /
• pp.131-139
• /
• 2020

The current study focused on the preparation of low-cost PVC-based adsorbing membrane. Metakaolin, as available adsorbent, was embedded into the PVC matrix via solution blending method. The as-prepared PVC/metakaolin mixed matrix membranes were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), pure water permeability and contact angle measurements. The results confirmed the improvement of PWP and hydrophilicity due to the presence of metakaolin in the PVC matrix. Additionally the structure of PVC membrane was changed due to the incorporation of metakaolin in the polymer matrix. The static adsorption capacity of all samples was determined through dye removal. The effect of metakaolin dosage (0-7%) and pH (4, 8, 12) on dye adsorption capacity was investigated. The results depicted that the highest adsorption capacity was achieved at pH of 4 for all samples. Additionally, adsorption data were fitted on Langmuir, Freundlich, and Temkin models to determine the appropriate governing isotherm model. Finally, the dynamic adsorption capacity of the optimum PVC/metakaolin membrane was studied using dead-end filtration cell. The dye removal efficiency was determined for pure PVC and PVC/metakaolin membrane. The results demonstrated that PVC/metakaolin mixed matrix membrane had a high adsorption capacity for dye removal from aqueous solution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.7
• /
• pp.418-426
• /
• 2013

With advantages of open spaces and existing HVAC facilities, subway station, if unexpected disastrous situation happens on the ground, can be used as a temporary safe place for evacuees. The main objective of this study is to establish a guideline on estimating evacuation capacity of the subway station and evaluating levels of service of evacuation for officials to control the situation. This guideline includes available spaces of the station, capacity of sanitary fixtures, and total number of passengers, etc. In this paper, we first analyzed the number of passengers of SMRT (Line 5~Line 8) during AM peak hour and then evaluated the number of passengers using toilets at that time. In addition, we calculated the seating capacity of subway stations on SMRT using the difference between the actual number of toilets and the estimated number of ones from the occupancy time of each toilet.

• Steel and Composite Structures
• /
• v.11 no.1
• /
• pp.1-19
• /
• 2011

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

• Earthquakes and Structures
• /
• v.8 no.3
• /
• pp.591-617
• /
• 2015

Standards for seismic assessment and retrofitting of buildings provide deformation limit states for structural members and connections. However, in order to perform fully consistent performance-based seismic analyses of soil-structure systems; deformation limit states must also be available for foundations that are vulnerable to nonlinear actions. Because such limit states have never been established in the past, a laboratory testing program was conducted to study the rotational capacity of small-scale foundation models under combined axial load and moment. Fourteen displacement-controlled monotonic and cyclic tests were performed using a cohesionless soil contained in a $2.0{\times}2.0{\times}1.2m$ container box. It was found that the foundation models exhibited a stable hysteretic behavior for imposed rotations exceeding 0.06 rad and that the measured foundation moment capacity complied well with Meyerhof's equivalent width concept. Simplified code-based soil-structure analyses of an 8-story building under an array of strong ground motions were also conducted to preliminary evaluate the implication of finite rotational capacity of vulnerable foundations. It was found that for the same soil as that of the experimental program foundations would have a deformation capacity that far exceeds the imposed rotational demands under the lateral load resisting members so yielding of the soil may constitute a reliable source of energy dissipation for the system.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.5
• /
• pp.43-51
• /
• 2008

This study examines shear capacity performance and structural characteristics of reinforced concrete beam using carbon fiber sheet(CFS), g)ass fiber sheet(GFS), glass fiber steel plate(GSP) and carbon fiber bar CB) which are reinforcing materials for reinforced concrete beam in order to produce similar condition to repair and reinforce actual structure and aims to provide data available In designing and constructing reinforced concrete structures under the structural damage. This study obtains the following conclusions. After considering the shear experiment results. it was indicated that the CB reinforced test object was the best in the shear capacity improvement and ductility capacity as it was contained in the concrete and was all operated, Also, GFS reinforced test object indicated the reduced flexural capacity but good shear capacity. GSP reinforced test object had bigger reinforcing strength than other reinforcing test objects. On the other hand, it showed the lowest reinforcement effect as compared section thickness of reinforced material because it showed the bigger relativity a section thickness of reinforced material. If the adherence to the concrete is improved, it will seem to show bigger reinforcement effect.

• Computers and Concrete
• /
• v.24 no.1
• /
• pp.37-49
• /
• 2019

In this study, the shear behaviour of reinforced concrete (RC) beams that were retrofitted using precast panels of ultra-high performance fiber reinforced concrete (UHPFRC) is presented. The precast UHPFRC panels were glued to the side surfaces of RC beams using epoxy adhesive in two different configurations: (i) retrofitting two sides, and (ii) retrofitting three sides. Experimental tests on the adhesive bond were conducted to estimate the bond capacity between the UHPFRC and normal concrete. All the specimens were tested in shear under varying levels of shear span-to-depth ratio (a/d=1.0; 1.5). For both types of configuration, the retrofitted specimens exhibited a significant improvement in terms of stiffness, load carrying capacity and failure mode. In addition, the UHPFRC retrofitting panels glued in three-sides shifted the failure from brittle shear to a more ductile flexural failure with enhancing the shear capacity up to 70%. This was more noticeable in beams that were tested with a/d=1.5. An approach for the approximation of the failure capacity of the retrofitted RC beams was evolved using a multi-level regression of the data obtained from the experimental work. The predicted values of strength have been validated by comparing them with the available test data. In addition, a 3-D finite element model (FEM) was developed to estimate the failure load and overall behaviour of the retrofitted beams. The FEM of the retrofitted beams was conducted using the non-linear finite element software ABAQUS.

• Journal of Industrial Technology
• /
• v.21 no.B
• /
• pp.205-212
• /
• 2001

This paper is experimental and numerical research about the sliding behavior of cantilever retaining walls resisting surcharge loads. In experimental research, centrifuge model tests at the lg and 40 g-level were performed by changing the location of model footing and its width. Bearing capacity of model footing and characteristics of load-settlement and load-lateral displacement of retaining wall were investigated. Test results of bearing capacity were compared with modified jarquio method, based on the limit equilibrium method with elasticity theory. For the numerical analysis, the commericially available program of FLAC was used by implementing the hyperbolic constitutive relationships to compare with test result about load-settlement and load-displacement of retaining wall, bearing capacity of strip footing.

• Tribology and Lubricants
• /
• v.25 no.5
• /
• pp.292-297
• /
• 2009

Air foil thrust bearings are the critical components available on high-efficiency turbomachinery which need an ability to endure the large axial force. Air foil bearings are self-acting hydrodynamic bearings that use ambient air as their lubricant. Since the air is squeezed by the edge of compliance-surface of bearing, hydrodynamic force is generated. In this study, we measured the air film thickness and obtained the minimum film thickness experimentally. To increase the maximum load capacity, compliance of sub-structure was controlled. From numerical analyses, it is seen that, if the air film thickness is distributed more uniformly by variable compliance, the thrust bearings can take more axial load.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.845-850
• /
• 2001

The primary objective of this study is to develop the new equation that can predict the flexural strength of irregular walls by applying the concept of the effective width which is used in current codes. Results obtained from this data analysis are as follows : 1. It is conservative to use PCI provision and ACI code as the effective width for evaluating the flexural capacity of irregular walls 2. The result of this study shows that the Paulay & Priestley's proposition is available for more exactly and safely predicting flexural capacity of irregular walls throughout a reduction factor.