• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.2
• /
• pp.136-143
• /
• 2011

The oversized and slotted holes are frequently required for the built-up in construction sites. The foreign provisions specify the reduction of the slip load subjected to the size of bolt holes and the direction of load. There are no domestic building codes and researches on the bolt holes. Therefore, it is necessary to evaluate a change of joint strength quantitatively according to the bolt-hole size and surface condition by means of experiment. This study was conducted to evaluate the slip load subjected to the size of bolt holes, and measured on a change of clamping force of high strength bolts during 168 and 800 hours to analyze the trend of relaxation after fastening bolts. Torque shear bolts defined on KS B 2819 was used for the specimen. Test results exhibit that the variation on the slip load of the others was below 10% by contrast with the standard hole and the highest rate of relaxation was 2.66% of the initial clamping force at the case of the long-slotted hole of 2.5D.

• Journal of Bio-Environment Control
• /
• v.12 no.3
• /
• pp.114-120
• /
• 2003

In order to provide fundamental data for development of controlled environment facilities in Korean ginseng (Panax ginseng C.A. Meyer) cultivation, field survey and analysis of structural and environmental engineering characteristics on the shading structures in ginseng fields (the ginseng houses) were carried out. In this study shading structures for ginseng cultivation were classified according to their structural materials, connection types, and detailed structures. That is they were classified into wood or steel frames, single or multi spans, and frame or cable types. As a result of the investigation, standardization of structural materials, fabrication and construction methods arc required. And it was considered that a reinforced design and a countermeasure for heavy snow are the most important matters for structural improvement. In parts of the environmental management, researches for setting up the irrigation standard are required in the first place. And it was investigated that an installation of the shading structures is a work being the most hard, taking a lot of time, and having need for automation. So controlled environment ginseng houses, with a low cost, a structural safety and a satisfactory workability, should be developed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.4
• /
• pp.369-376
• /
• 2003

In this paper, Ka-Band NRD guide band pass filter with newly designed inductive post structure is proposed and analyzed with its test results. Generally, millimeter-wave filters are very sensitive in their physical dimensions, hence, it is requires extreme precisions of several micron so as to get the designed performance. In case of common NRD Guide filter with air gap coupled structure, it is fabricated with dielectric blocks coupled via air gap. In these structures, however, it was not easy to fabricate and to process of each NRD guide dielectric resonator blocks using PTFE, so it was almost impossible to assemble with several microns in precision. In this our research, however, each dielectric resonators are coupled with a pair of inductive metal post, so all resonators are located in a single NRD Guide. The dielectric parts between two pairs of posts are operated as resonators of each stage, and the positions of the post decide the couplings between resonators. The structure we suggested is suitable fur mass production, because it is very simple and easy to process. As a result of measurements, designed NRD guide inductive post filter has a superior performance. The center frequency is 39.475 GHz with 350 MHz bandwidth, insertion loss is less than 1.8 dB, and the return loss is below than -18 dB.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• 2008.11a
• /
• pp.197-201
• /
• 2008

Conceptual cost estimates for domestic highway projects have generally been conducted using governmental unit-price references. Inaccuracies in governmental unit-price data has repeatedly addressed in the Korean construction industry which often lead to poor decision making and cost management practices. Thus, needs for developing a better way of conceptual cost estimating has been widely recognized. This research is considered as the first step in developing such model using real-world cost data based on actual construction activities. The data analyzed in this paper includes 41 P.S.C (Prestressed Concrete) Box bridges which broke into 4 categories based on construction methods such as I.L.M(Incremental Launching Method), M.S.S(Movable Scaffolding System), F.S.M(Full Staging Method), and F.C.M(Free Cantilever Method). Actual design documents; including actual cost estimating documents, drawings and specifications were carefully reviewed to effectively break down cost structures for PSC girder bridges. Among more than 40 cost categories for each P.S.C girder bridge type, 7 of them were identified which accounted for more than 95% of total construction cost (ILM: 99.47%, MSS: 99.22%, FSM: 98.18%, and FCM: 98.12%). In order to validate the clustering of cost categories, the variation of each cost category has been investigated which resulted in between -1.16 % and 0.59%.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.1
• /
• pp.104-111
• /
• 2016

The steel frame modular housing of which the research and development has been actively carried out recently cannot be constructed through monolithic placement like the reinforced concrete deck of general structure due to the characteristics of construction method of production in the factory and assembly on the site. And floor vertical vibration and deflection caused by inhabitants' activities may become an important issue in the aspect of usability evaluation due to a decrease in the section size of member, a decrease in weight, and so on. Therefore, this study evaluated the vibration performance of deck by using formula of AISC Design Guide 11(hereinafter AISC formula) which was practically used in general for modules where a stud was and wasn't installed at the center of beam in the longitudinal direction in the modular housing to be studied, and examined the applicability of AISC formula through comparison with the results of analysis using a general-purpose analysis program. On the basis of this, a structural cause for an error to occur between analysis result and AISC formula in the deck of module in which a stud was installed was analysed, and measures for considering this were suggested. Besides, an analysis model with the variables of measures for improving the floor vibration performance of modular housing to be studied was established. And measures having excellent vibration performance and economic feasibility were suggested through vibration response analysis and economic evaluation.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.6
• /
• pp.34-42
• /
• 2002

In this paper, we propose a temperature independent the detective voltage source in voltage detector. The value of a detective voltage source is designed to become m times of silicon bandgap voltage at zero absolute temperature. By properly choosing the temperature coefficient of diode, the temperature coefficient of a concave voltage nonlinearities generated by the ${\Delta}V_{BE}$ section of diode between base and emitter of transistors with a different area can be summed with convex nonlinearities the $V_{BE}$ voltage to achieve the near zero temperature coefficient of the detective voltage source. We designed that the value of a detective voltage can be varied by ${\Delta}V_{BE}$, the $V_{BE}$multiplier circuit and resistor. In order to verify the performance of a proposed detective voltage source, we manufactured the voltage detector IC for 1.9V which is fabricated in $6{\mu}m$ Bipolar technology and measured the operating characteristics, the temperature coefficient of a detective voltage. To reduce the deviation of a detective voltage in the IC process step, we introduced a trimming technology, ion implantation and an isotropic etching. In manufactured IC, the detective voltage source could achieve the stable temperature coefficient of 29ppm/$^{\circ}C$ over the temperature range of -30$^{\circ}C$ to 70$^{\circ}C$. The current consumption of a voltage detector constituted by the proposed detective voltage source is $10{\mu}A$ from 1.9V-supply voltage at room temperature.

• Journal of the Korea Concrete Institute
• /
• v.23 no.3
• /
• pp.281-287
• /
• 2011

Recently, bridge construction technology has made great progress from development of high performance materials and new bridge types. However, most technology are based on methods of cast-in-place and material cost saving. The method of cast-in-place concrete causes environmental damages and costumer complaints. Especially, under bad weather conditions, the construction can not proceed. To overcome these disadvantages, new construction methods were developed to reduce construction time. These methods are called precast method. Most prefabricated methods have been applied to superstructure constructions of bridges, but very minutely applied to substructure constructions. The most important agendas on precast method are light weight and transportability of the precasted members, because very strict transporting specifications exist for road transportation of the precasted members. For example, the weight and length of coping members may be larger than the available transporting vehicles. Although column is constructed by precast method to save construction time, if coping member is constructed by cast-in-place method, then the column construction time reduction becomes meaningless. Therefore, in this study, a new precast coping member and a connecting system of column-coping member are proposed. The proposed method is verified by analyzing their ultimate performance through analysis and experimental study.

• Journal of Navigation and Port Research
• /
• v.33 no.5
• /
• pp.315-321
• /
• 2009

The Very Large Marine Structure has been widely used new method of ocean space instead of method for reclamation Therefore, VLFS is proposed to coincide on such request. It can be established regardless of nature of soil and height of water, and stream of flow exists under the floating structure, there is seldom effect in natural environment. Fuertherrnore, it can do easily to do assembly and taking to pieces due to expansion or removal. Based on the regulation by class, VLFS have to possess more than enough structural strength against severe wave loading induced by green sea condition Therefore, There are performed structural simulation as well as experimental test about expected loading scenario in order to examine the safety of structure. Up to now, various examinations based on the strength limit value of the main structural material have been done based on the elasticity response analysis. However, there is little finding about the collapse behavior and the safety when the load that exceeds the collapse of the material acts. In the present study, we investigated the collapse behavior based on the ultimate limit state calculated by FE-analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.4
• /
• pp.304-312
• /
• 2011

Grain size analysis was conducted for a total of 402 surface sediments collected from 67 sites along three (upper, middle, and lower) transects corresponding to the high-, mid-, and low-intertidal zone of beach on the Sinjado, Nakdong River estuary in Nov. 2005 and May 2006. Sinja-do beach sediments showed uni-modal grain size distributions, in which the mode of $3.0{\phi}$ was dominant in 2005 whereas the mode of $2.5{\phi}$ in 2006. This coarsening trend was more remarkable in the western side of beach as well as in the mid- and low-intertidal zone. In this study, we focused on investigating characteristics of sediment size changes on the basis of transect data that differ in tidal elevation. For this purpose, a statistical test was applied for transect by transect comparison of grain size parameters such as mean, sorting, and skewness. Mean values between middle and lower transect, sorting values between upper and lower transect, and skewness values over the beach reflected statistically significant temporal changes. Also, mean and skewness parameters showed an inverse relationship which was more stronger in 2006 than in 2005. Temporal changes in Sinja-do beach sediments resulted in decrease of mean and sorting values but increase of skewness values, intensifying the inverse relationship between mean and skewness parameters.

• Journal of Conservation Science
• /
• v.31 no.1
• /
• pp.47-64
• /
• 2015

The excavated potteries and raw clays of the Bronze Age from the archaeological sites in the Cheonan-Asan area were studied on material scientific characteristics and homogeneity. Under the microscope, grainsize of the tempers in the potteries were distributed from less than 1mm to 10mm. Microtexture of the potteries showed various shapes and sizes of pores. In addition to the main minerals such as quartz, feldspar, mica, hornblende, chlorite and talc were found from the X-ray diffraction analysis of potteries, while talc was not found in the raw clay. Therefore, it was considered as an artificially added mineral. Firing temperature of the potteries, which did not contain chlorite, are assumed that they were baked below $850^{\circ}C$. On the other hand, the potteries which had mica and talc, are assumed that they were fired below $900^{\circ}C$. The geochemical characteristics of the potteries and raw clays showed very similar patterns, that means the potteries were produced by using the raw clay sources from each site.