• Journal of Dental Rehabilitation and Applied Science
• /
• v.18 no.3
• /
• pp.145-155
• /
• 2002

The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.979-984
• /
• 2001

Poor water-proofing integrity is related to many factors : site procedure, workmanship, weather. substrate conditions, installation(including asphalt application) conditions. The evaluation of adhesive properties tested by concrete surface moisture and asphalt application was based on laboratory test and observations. This report describes the pull-off test results of waterproofing systems currently used for installing and reparing for concrete bridge decks. The test results showed that the moisture condition fully affected the adhesive properties of sheet membranes and sealer but partially for liquid membranes.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1994.03a
• /
• pp.19-30
• /
• 1994

This paper reports a case study of aboutment displacement and pavement settlement observed at the construction site for highway bridges. The emphasis was on quantifying the horizontal deflections of about and pavement settlement on the backfill surface. It is shown that in soft clay, bridge aboutments on pile foundations are subjected to lateral earth pressures due to lateral soil movement. Based on the results analyzed, the earth pressure was predicted by deflection shape of piles based on the results of a numerical analysis and an analytical study. Also, the long term settlement of soil below pavement was estimated.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2011.05a
• /
• pp.51-54
• /
• 2011

In this study, It has the purpose to evaluate the insulation of the curtain wall of a building on the construction from 1990 to 2011 by measuring the inside and outside surface temperature of the curtain wall. The outside frame surface(mullion bar or spandrel bar) temperature of the curtain wall is 6℃~10℃ higher than that of the surface of glasses or insulation panel of curtain wall in winter. Furthermore the outside surface of frame anchor unit is 2℃~3℃ higher than section of other frame, so it was verified lossing lots of heating.

• Ocean Systems Engineering
• /
• v.14 no.1
• /
• pp.53-72
• /
• 2024

The interaction of the blade of surface-piercing propellers (SPPs) with the water/air surface is a physical phenomenon that is difficult to model mathematically, so that such propellers are usually designed using empirical approaches. In this paper, a newly developed mechanism for measuring the torque of SPPs in an open water circuit is presented. The mechanism includes a single-component load cell and a deformable torque sensor to detect the forces exerted on the propeller. Deformations in the sensor elements lead to changes in the strain gauge resistance, which are converted into voltage using a Wheatstone bridge. The amplified signal is then recorded by a 16-channel data recording system. The mechanism is calibrated using a 6-DoF calibration system and a Box-Behnken design, achieving 99% accuracy through multivariate regression and ANOVA. Finally, the results of performance tests on a 4-blade propeller were presented in the form of changes in the torque coefficient as a function of feed rate. The results show that the new mechanism is 8% more accurate than conventional empirical methods.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.104-112
• /
• 2015

Non-contact surface wave transmission (SWT) measurements are used to evaluate the depth of a surface-breaking crack in concrete slabs. The author propose a measurement model that includes an appropriate configuration of the source and receivers, and a transmission function for the given configuration. A series of numerical simulations using a 3D finite element model is used to obtain the transmission function. Then, validity of a proposed model is verified through experimental studies. Two air-coupled sensors are used to measured surface waves across surface-breaking cracks with varying depths from 0mm to 100mm with intervals of 10mm in a concrete slab ($1500{\times}1500{\times}180mm^3$) in laboratory. As a result, the proposed method is demonstrated as to be effective for charactering the depth of a surface-breaking crack in concrete bridge deck with an average error of 10%. A discussion on practical applications of the proposed method is also included in this article.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.65-66
• /
• 2002

One aspect of the stiction problem may be explained by the action of capillary forces in conjunction with surface elasticity. In the present work, the interaction between two elastic half-spaces separated by a small liquid bridge is investigated. By minimizing the total free energy stored in the interface (including elastic energy and surface energy), the equilibrium interface geometry is determined analytically in the case where there is no solid-solid contact. A non-dimensional number, $N_c=299\frac{{\gamma}^2_{LA}cos^2{\theta}V_o}{E^{'2}H^5}$ is found to govern the structure stability. When $N_c{\ge}1$, the two surfaces jump into solid-solid contact and, once this occurs, the contact area will continue to expand until the two surfaces are in full contact.

• International Journal of Concrete Structures and Materials
• /
• v.6 no.3
• /
• pp.199-207
• /
• 2012

Concrete is an economical construction material and for that reason it is widely used in buildings and infrastructures. The use of deicing salts, expansion joint failure, and freeze-thaw cycles have led to concrete bridge girders experiencing corrosion of steel reinforcement and becoming unsafe for driving. The goal of this research is to assess the effectiveness of current and possible repair techniques for the end region of damaged prestressed concrete girders. To do this, three American Association of State Highway and Transportation prestressed concrete girders were tested to failure, repaired, and retested. Three different repair materials were tested including carbon fiber, glass fiber, and surface mounted rods. Each different repair material was also tested with and without injected epoxy. Comparisons were then made to determine if injecting epoxy had a positive effect on stiffness and strength recovery as well as which repair type regained the largest percentage of original strength.

• Steel and Composite Structures
• /
• v.9 no.5
• /
• pp.445-455
• /
• 2009

This study proposes a system identification technique for a fiber-reinforced polymer deck with neural networks. Neural networks are trained for system identification and the identified structure gives training data in return. This process is repeated until the identified parameters converge. Hence, the proposed algorithm is called an iterative neural network scheme. The proposed algorithm also relies on recent developments in the experimental design of the response surface method. The proposed strategy is verified with known systems and applied to a fiber-reinforced polymer bridge deck with experimental data.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.199-204
• /
• 2001

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.