• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.515-526
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• 2007

In this study, the models and methods for the safety assessment of Steel-Concrete Hybrid Cable-Stayed Bridge, which consists of steel composite girder and concrete girder erected by the FCM(Free Cantilever Method) and FSM(Full Staging Method) are proposed for the assurance of structural safety and the prevention against bridge collapse during construction. By the structural reliability approach that reasonably considers the uncertainties associated with the resistance and the load effect, the resistance and the load distribution characteristics of Steel-Concrete Hybrid Cable-Stayed Bridgeare defined and the strength limit state equations of permanent structures and temporary structures during construction are suggested. An AFOSM algorithm and MCS technique are used for the reliability analysis of cables, pylons, girders, steel-concrete conjunction part and temporary bents. Also, component reliability analyses are performed at the construction stages based on the structural system model. To demonstrate their rationality and practicality, the proposed models and approaches are applied to a real bridge. The sensitivity analyses of main parameters are performed in order to identify the critical factors that control the safety of similar bridges. As a result, it may be stated that the proposed models could be implemented as a rational and practical approach for the safety assessment of Steel-Concrete Hybrid Cable-stayed bridges erected by FCM and FSM during construction.

• Journal of Korean Society of Transportation
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• v.27 no.5
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• pp.209-221
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• 2009

Travel time estimation under given traffic conditions is important for providing drivers with travel time prediction information. But the present expressway travel time estimation process cannot calculate a reliable travel time. The objective of this study is to estimate the path travel time spent in a through lane between origin tollgates and destination tollgates on an expressway as a prerequisite result to offer reliable prediction information. Useful and abundant toll collection system (TCS) data were used. When estimating the path travel time, the path travel time is estimated combining the link travel time obtained through a preprocessing process. In the case of a lack of TCS data, the TCS travel time for previous intervals is referenced using the linear interpolation method after analyzing the increase pattern for the travel time. When the TCS data are absent over a long-term period, the dynamic travel time using the VDS time space diagram is estimated. The travel time estimated by the model proposed can be validated statistically when compared to the travel time obtained from vehicles traveling the path directly. The results show that the proposed model can be utilized for estimating a reliable travel time for a long-distance path in which there are a variaty of travel times from the same departure time, the intervals are large and the change in the representative travel time is irregular for a short period.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.43-49
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• 2017

In recent years, the use of BIM in domestic construction has been increasing, but it is used mainly for internal and external visualization rather than for BIM design including drawings. For this reason, several studies have highlighted the lack of libraries and economic problems for BIM design. In other words, for the most economically small domestic design offices, activating the BIM design is a negative factor because it is difficult to invest the necessary manpower and cost to produce and use the required BIM library. The BIM design can be more applicable if the library can be supplied economically, easily, and quickly. In this study, BIM library business model and consideration factors that can provide BIM library service economically, easily, and quickly by considering the existing building material selection task and BIM library are presented. The proposed business model will increase the number of suppliers of BIM libraries, which are lacking in Korea, and will enable an effective BIM design at low cost and effort. If a service that reflects the business model proposed in this study is made, an integrated database that can consistently share information in the design, construction, and maintenance stages will be constructed. This can monitor the changes in material and equipment information during the life cycle of the building. The database can be used to monitor any changes in material and equipment information throughout the life cycle of a building, so that it can be used as historical data for effective design and maintenance as well as for material and equipment upgrades.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.67-77
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• 2008

Seismic isolation has been studied continuously as a solution of the seismic engineering to reduce the sectional forces and the damages of structures caused by earthquakes. To certify reliable design and installation of the seismic isolation systems, seismic isolation bearings should be fabricated under well planned quality control process, and proper evaluation tests for their seismic performance should be followed. In this study, shear property evaluation tests for the lead rubber bearings(LRB) and the rubber bearings(RB) were implemented and the temperature dependency tests were also implemented to evaluate the changes of shear properties according to the changes of temperature. After evaluation tests, the measured shear properties were compared to their design values and their deviation was analyzed comparing with the allowable error ranges specified in Highway Bridge Design Specifications. These results showed that a considerable number of isolation bearings have so large deviations from their design values that their error ranges were over or very close to the allowable ranges. And the test results for temperature dependency showed that the shear properties of isolation bearings would be changed in great degree by the change of temperature during their service period. If these two types of changes in their shear properties are superposed, it would possible that the changes of shear properties from their original design values are over than 50%.

• Korean Journal of Construction Engineering and Management
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• v.19 no.5
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• pp.70-80
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• 2018

Recently, the construction industry has lively utilized system forms to improve the work productivity and safety of form work, and the beam table form is one of them. However, the beam table form is used limitedly for the construction of buildings where the same beam size is applied to every floor. To make it possible to apply the beam table form to a building where different beam sizes are designed according to the uses of floors, it was analyzed that among the components of the beam table form, the beam bracket, should be able to flexible adjust the size of the beam form only with simple operation. Therefore, the purpose of this study is to propose the conceptual design of "an adjustable beam bracket for beam table form" that allows the adjustment of beam form size with simple operation and has excellent applicability to construction sites as well. In case this study's conceptual design of adjustable beam bracket for beam table form is fabricated into a real thing, it is expected that the beam table form will be applicable to even buildings where different beam sizes are designed according to the uses of floors, thereby contributing to the improvement in the work productivity and safety of form work.

• Journal of Digital Convergence
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• v.19 no.9
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• pp.189-199
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• 2021

In order to increase the self-reliance rate of new and renewable energy in order to respond to the mandatory domestic zero-energy buildings, the taller the building, the more limited the site area, and installing PV modules on the roof is not enough. Therefore, BIPV (Building integrated photovoltaic, hereinafter BIPV) is the industry receiving the most attention as a core energy source that can realize zero-energy buildings. Therefore, this study conducted a survey on the problems of the BIPV industry in a self-discussing method for experts with more than 10 years of experience of designers, builders, product manufacturers, and maintainers in order to suggest the right direction and revitalize the BIPV industry. Industrial problems of BIPV adjustment are drawn extention range of standard and certification for products, range improvement for current small condition of various kind productions, need to revise standards for capable of accomodating roof-type, color-module and louver-module, necessary of barrier in flow of foreign modules into korea through domestic certification mandatory, difficulty in obtaining BIPV information, request to prevent confusion among participants by exact guidelime about architectural application part of BIPV, and lack of the BIPV definition clearness, support policy, etc. Based on the improvements needed for the elements, giving change and competitiveness impacts aims to present and propose counter measures and direction.

• Journal of Wetlands Research
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• v.23 no.2
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• pp.189-200
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• 2021

To improve the water quality of agricultural reservoirs, constructed wetlands are applied in many places. These are technologies that establish ecosystems and important design factors include water depth distribution, inflow and outflow, water flow distribution, hydraulic residence time, water quality treatment efficiency, aspect ratio, and the distribution of open water and covered water surfaces. For high efficiency during the operation of a constructed wetland, the design needs to be optimized and this requires consideration of the different types and length of the intake dam as well as the type and connection of wetland cells. Therefore, this study was conducted to investigate and suggest factors that needs to be considered during the design and for efficient operation measures through field surveys of 23 constructed wetlands that have been established and operated in agricultural reservoirs. Results of the field investigation shows that several sites were being operated improperly due to the malfunctioning or failure of the water level sensors, sedimentation in the intake dam, and clogging of the mechanical sluice frames. In addition, it was found that as the length of the inlet channel increases, the ecological disconnection between the intake dam upstream and the wetland outlet downstream also increases and was identified as a problem. Most of the wetlands are composed of 2 to 5 cells which can result to poor hydraulic efficiency and difficulty in management if they are too large. Moreover, it was found that the flow through a small wetland can be inadequate when there are too many cells due to excessive amounts of headloss.

• Journal of the Korean Society of Earth Science Education
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• v.14 no.3
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• pp.248-256
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• 2021

The purpose of this study is to investigate the perception of pre-service elementary teachers on the educational approach to metaverse. Questions about metaverse were asked to 71 pre-service elementary teachers who were taking the course 'Study of Textbooks in Elementary Science II'. The results of analyzing the contents of the questions are as follows. The results and conclusions were presented through numerical analysis and static analysis based on the responses to questions presented using the university's LMS system. First, the level of understanding of the metaverse of pre-service elementary teachers is very high. Pre-service elementary teachers, as the MZ generation, are already living in a very fast IT environment that can be the basis of the metaverse, so it would have been helpful to understand the metaverse. Second, the need for the metaverse of pre-service elementary teachers is very high. There was a tendency to think that the perception of pre-service elementary teachers is because the metaverse has many factors that can provide higher quality education beyond the current educational environment. Third, in the question of applicability exploration in the 'Earth and Space' domain of Pre-service elementary teachers, there have been few cases in which instructional design was planned based on instructional design principles. Based on these results, if the possibility of metaverse application is proposed in the 'Earth and Space' domain, educational contents using virtual space that can transcend time and space will be very necessary. Based on these results, suggestions are made as follows. First, educational content incorporating the metaverse technique based on instructional design should be developed and utilized. Second, financial support should be provided so that the metaverse can be implemented in the educational environment. Third, it is necessary to provide training opportunities for teachers (including Pre-service elementary teachers) to give lectures on metaverse.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.7-17
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• 2022

The ratios of water and controlled low-strength materials (CLSM) were selected as 1:0.4, 1:0.6, 1:0.8, 1:1.0, and 1:1.2 to minimize the construction and long-term decrease in uniaxial compressive strength due to dry shrinkage through the combination of water, CLSM, and expansion agent. Approximately 2% and 5% of the expansion agent were added for each blending condition. As a result, it was found that the compressive strength decreased and the expandability increased as the specific gravity of the water increased. In addition, it was confirmed that the compressive strength increased rapidly up to 15 days of age compared to the CLSM used in the field. However, the compressive strength decreased compared to the 15 days of the age as of the 28 days of the age. It showed engineering characteristics similar to CLSM generally used in the field. Therefore, the water and the CLSM were mixed at a ratio of 1:0.8, and the field test was performed by adding 5% of an expansion agent. As a result, 28 days after age, the cavity waveform was observed using the handy GPR exploration system, and it was found that cavity waveform was relaxed or disappeared.

• Journal of the Korean Geosynthetics Society
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• v.22 no.2
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• pp.35-45
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• 2023

In accordance with the urban development project, cases of constructing temporary wall structures for ground excavation in the vicinity of railway structures are increasing. In addition, the complaints about train vibration are also increasing from people living in large buildings newly built after installing the temporary wall structures. In order to solve this problem, a method for reducing train vibration is considered from the design stage of the building, and a vibration reduction system is installed on the structure when the building is newly constructed. However, the vibration reduction method established at the structure design stage can be determined through the results of field measurements or dynamic numerical analysis for a specific area, and there is a limit to evaluating whether the established vibration reduction method is appropriate due to the lack of objective research data. Therefore, in order to provide objective basic data when establishing a vibration reduction method, this study performed the dynamic numerical analysis for a operating train with a speed 80km/h by applying differently the depths of railway structures, the distances between railways and temporary wall structures, and ground conditions. It was found that the range of influence of a train operating at 80 km/h was within 4.5D of the lateral distance from the railway structure in the case of the condition where the temporary wall was installed.