• Structural Engineering and Mechanics
• /
• v.47 no.5
• /
• pp.643-660
• /
• 2013

In the present work, the capacity ratings of steel truss bridges have been carried out incorporating dynamic effect of moving vehicles and its accumulating effect as fatigue. Further, corrosion in the steel members has been taken into account to examine the rating factor. Dynamic effect has been considered in the rating procedure making use of impact factors obtained from simulation studies as well as from codal guidelines. A steel truss bridge has been considered to illustrate the approach. Two levels of capacity ratings- the upper load level capacity rating (called operating rating) and the lower load level capacity rating (called inventory rating) were found out using Load and Resistance Factor Design (LRFD) method and a proposal has been made which incorporates fatigue in the rating formula. Random nature of corrosion on the steel member has been taken into account in the rating by considering reduced member strength. Partial safety factor for each truss member has been obtained from the fatigue reliability index considering random variables on the fatigue parameters, traffic growth rate and accumulated number of stress cycle using appropriate probability density function. The bridge has been modeled using Finite Element software. Regressions of rating factor versus vehicle gross weight have been obtained. Results show that rating factor decreases when the impact factor other than those in the codal provisions are considered. The consideration of fatigue and member corrosion gives a lower value of rating factor compared to those when both the effects are ignored. In addition to this, the study reveals that rating factor decreases when the vehicle gross weight is increased.

• Journal of the Korean Society of Safety
• /
• v.18 no.1
• /
• pp.81-88
• /
• 2003

Recently, pile foundations were constructed in rough or soft ground than ground of well condition thus it is important that prediction of ultimate bearing capacity and calculation of proper safety factor applied pile foundation design. This study were performed to dynamic loading tests for the thirty two piles at four different construction sites and selected pile at three site were performed to static loading tests and then compare with measured value and value of static and dynamic loading tests. The load-settlement curve form the dynamic loading tests by CAPWAP was very similar to the results obtained from the static load tests. Based on dynamic and static loading tests, the reliability of pile-driving formula were analyzed and then suggested with proper safety factor for prediction of allowable bearing capacity in this paper.

• Magazine of the Korea Concrete Institute
• /
• v.4 no.4
• /
• pp.135-147
• /
• 1992

본 연구는 기존의 이론을 배경으로 전단키에 영향을 미치는 전달전달의 요소가 포함된 기본식을 산정하여, 접합부의 유형에 따라 구체적으로 전단강도를 예측하는 방법을 제안하였다. 접합부 콘크리트와 횡보강철근의 강도 및 장부호과를 고려한 프리캐스트 콘크리트 전단키 접합부의 기본극한강도식은 수정 Mohor-Coulomb의 파괴기준과 항복선의 도입에 의하여 전개하였고, 극한전단능력의 근사해는 상하계법에 의한 극치해석의 수법을 이용하여 구하고 여기에 재료의 유효강도계수를 도입하였다. 또한, 지존의 실험결과와 비교하여 그 적용성을 고찰하였다.

• Plant Journal
• /
• v.7 no.1
• /
• pp.40-48
• /
• 2011

This study shows the comparison between expected and actual capacity factors of a wind farm through wind resource analyzation. The expected capacity factor comes from an 'automatic weather system' run by the Korean national weather service and a 'meteorological mast' run by a project owner. Based on this comparison and analysis, the importance of meteorological mast micro-siting and selection of wind turbine class and type, will be studied along with presenting important implications for wind farm expansion and development.

• Journal of The Korean Association For Science Education
• /
• v.16 no.2
• /
• pp.134-145
• /
• 1996

The purpose of this study was to investigate effects of mental capacity and mental demand on problem solving. Two kinds of tests were used for this study. One was FIT 752 test which required general knowledge, the other was Ohm's law test which required domain specific knowledge. The items of each test had the same logical structure and content knowledge but had different sizes of mental demand. The results of the study were summarized as follows: As mental demand of the items increased, the success rates decreased. The analysis of the hierarchical relation among items was that items with large mental demand were higher than those with small demand or at least the same level. According to the results, mental of an item was a significant factor affecting solving the problem. Effect of mental capacity on problem solving was different according to the kind of required knowledge to solve. Mental capacity was a significant factor affecting solving the FIT 752 task which required general knowledge. On the contary, solving the task which required domain specific knowledge, the results were different depending on subjects' chunk size. The results of problem solving of the groups which had small chunk size were that mental capacity was appeared a significant factor. However, results of problem solving of groups which had large chunk size were that mental capacity was not.

• Computers and Concrete
• /
• v.31 no.5
• /
• pp.443-455
• /
• 2023

This is a research analyses on the bearing capacity at a pile tip embedded in rock. The aim is to propose a shape coefficient for an analytical solution and to investigate the influence of the plastic flow law on the problem. For this purpose, the finite difference method is used to analyze the bearing capacity of various types and states of rock masses, assuming the Hoek & Brown failure criterion, by considering both plane strain and an axisymmetric model. Different geometrical configurations were adopted for this analysis. First, the axisymmetric numerical results were compared with those obtained from the plane strain analytical solution. Then the pile shape influence on the bearing capacity was studied. A shape factor is now proposed. Furthermore, an evaluation was done on the influence of the plastic flow law on the pile tip bearing capacity. Associative flow and non-associative flow with null dilatancy were considered, resulting in a proposed correlation. A total of 324 cases were simulated, performing a sensitivity analysis on the results and using the graphic output of vertical displacement and maximum principal stress to understand how the failure mechanism occurs in the numerical model.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.11
• /
• pp.2149-2154
• /
• 2009

Electric power quality in power transmission/distribution systems has considerably been deteriorated with the increase in the capacity of distributed generators (DGs). It is because inverters, connecting DGs to conventional power grids, tend to generate harmonic current and voltage. For harmonic mitigation, a large amount of research has been done on passive and active filters, which have been operating successfully in many countries. This paper, therefore, presents how to adopt the filters to an inverter-based DG, with considering a system consisting of both inverter-based DG and harmonic filters. In particular, this paper describes the simulation results using the PSCAD/EMTDC: firstly, the relationship between total harmonic distortion(THD) of current and output power of DG: secondly, the harmonic mitigation ability of passive and active filters. The system, furthermore, is obliged to satisfy the regulations made by Korean Electric Power Corporation(KEPCO). In the regulations, power factor should be maintained between 0.9 and 1 in a grid-connected mode. Thus, this paper suggests two methods for the system to control its power factor. First, the inverter of DG should control power factor rather than an active filter because it brings dramatic decrease in the capacity of the active filter. Second, DG should absorb reactive power only in the range of low output power in order to prevent useless capacity increase of the inverter. This method is expected to result in the variable power factor of the system according to its output power.

• Earthquakes and Structures
• /
• v.14 no.6
• /
• pp.537-549
• /
• 2018

Using vertical links in eccentric braced frames is one of the best passive structural control approaches due to its effectiveness and practicality advantages. However, in spite of the subject importance there are limited studies which evaluate the seismic reliability and response reduction factor (R-factor) in this system. Therefore, the present study has been conducted to improve the current understanding about failure mechanism in the structural systems equipped with vertical links. For this purpose, following definition of demand and capacity response reduction factors, these parameters are computed for three different buildings (4, 8 and 12 stories) equipped with this system. In this regards, pushover and incremental dynamic analysis have been employed, and seismic reliability as well as multi-level response reduction factor according to the seismic demand and capacity of the frames have been derived. Based on the results, this system demonstrates high ductility and seismic energy dissipation capacity, and using the response reduction factor as high as 8 also provides acceptable reliability for the frame in the moderate and high earthquake intensities. This system can be used in original buildings as lateral load resisting system in addition to seismic rehabilitation of the existing buildings.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.6
• /
• pp.1-6
• /
• 2008

Anchors have been commonly used to as foundation systems of the structures that require the uplift resistance. Recently anchors have been used in ocean sediment for mooring systems to stabilizeoffshore structures. In the saturated clayey soil however suction developed between the soil and andchor and affects the uplift capacity of anchor. To estimate the uplift capacity of the andchor accurately, the failure mechanisms of the andchor by the uplift force should also be correctly assumed. The uplift capacity is usually expressed in terms of breakout factors with respect to embedment ratio. In this paper, a two-dimensional plane strain numerical investigation into the vertical uplift capacity of a plate andchor in a clayey soil is described. The breakout factor against their corresponding values of embedment ratio was calculated and plotted along a single curve. The modes of failure mechanism at shallow and deep andchors are also presented.

• Journal of Korean Society of Transportation
• /
• v.1 no.1
• /
• pp.56-63
• /
• 1983

Intersection control has dual-purposes; increasing capacity and reducing delay. The primary concern of efficient intersection control under oversaturated condition as in Korea is to increase capacity. Prevailing intersection operation technique permits thru traffic to utilize left turn lane, because the intersection without left turn pocket has left turn signal interval. In this situation, it seems not to be valid to calculate capacity, delay, and signal timings by conventional methods. By critical lane technique, capacity increases as cycle length increases. However, when thru traffic utilize LT lane, the capacity varies according to LT volume, LT interval as well as cycle length, which implies that specific cycle length and LT interval exist to maximize capacity for given LT volume. The study is designed is designed to calculate utilization factors of LT lane for thru traffic and capacities, and identify signal timings to yield maximum capacity. The experimental design involved has 3 variables; 1)LT volumes at each approach(20-300 vph), 2)cycle lengths (60-220 sec), and 3)LT intervals(2.6-42 sec) for one scenario of isolated intersection crossing two 6-lanes streets. For LT volume of 50-150 vph, capacity calculated by using the utilization factor is about 25% higher than that by critical lane method. The range of optimum cycle length to yield maximum capapcity for LT volume less than 120 vph is 140-180 sec, and increases as LT volume increases. The optimum LT interval to yield maximum capacity is longer than the intrval necessary to accommodate LT volume at saturation flow rate.