• Earthquakes and Structures
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• 제11권6호
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• pp.1061-1076
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• 2016

Prefabricated Modular Buildings are increasingly becoming popular in the construction industry as a method to achieve financially economical buildings in a very short construction time. This increasing demand for modular construction has expanded into multi-storey applications where the effect of lateral loads such as seismic loads becomes critical. However, there is a lack of detailed scientific research that has explored the behaviour of modular buildings and their connection systems against seismic loads. This paper will therefore present the nonlinear time history analysis of a multi-storey modular building against several ground motion records. The critical elements that need special attention in designing a modular building in similar seismic conditions is discussed with a deeper explanation of the behaviour of the overall system.

• Structural Engineering and Mechanics
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• 제12권4호
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• pp.397-408
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• 2001

Bolted connections are used commonly in the precast reinforced concrete structures. In such structures, to perform structural analysis, behaviour of connections must be determined. In this study, elastic rotation stiffness of semi-rigid bolted beam connections, applied in industrial precast structures, are determined by finite element methods. The results obtained from numerical solutions are compared with an experimental study carried out for the same connections. Furthermore, stress distributions of the connection zone are determined and a reinforcement scheme is proposed. Thus, a more appropriate reinforcement arrangement for the connection zone is enabled. The connection joint of the prefabricated frame is described as rigid, hinged or elastic, and a static analysis of the frame system is performed for each case. Values of bending moments and displacements obtained from the three solutions are compared and the effects of elastic connection are discussed.

• Smart Structures and Systems
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• 제32권2호
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• pp.111-121
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• 2023

This study proposes an automated assembly performance evaluation method for prefabricated steel structures (PSSs) using machine learning methods. Assembly component images were segmented using a modified version of the receptive field pyramid. By factorizing channel modulation and the receptive field exploration layers of the convolution pyramid, highly accurate segmentation results were obtained. After completing segmentation, the positions of the bolt holes were calculated using various image processing techniques, such as fuzzy-based edge detection, Hough's line detection, and image perspective transformation. By calculating the distance ratio between bolt holes, the assembly performance of the PSS was estimated using the k-nearest neighbors (kNN) algorithm. The effectiveness of the proposed framework was validated using a 3D PSS printing model and a field test. The results indicated that this approach could recognize assembly components with an intersection over union (IoU) of 95% and evaluate assembly performance with an error of less than 5%.

• 국제학술발표논문집
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• The 7th International Conference on Construction Engineering and Project Management Summit Forum on Sustainable Construction and Management
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• pp.271-280
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• 2017

Small islands in humid and hot climates have received less attention development due to lack of resources and difficulties for in-situ construction. This paper addresses this problem by presenting a modular system for sustainable construction of a resort hotel in accordance with the international tourism standards, in addition to, minimizing undesirable effects on nature. This has been achieved by review of literature in the scope of off-site construction and identification of the natural geographical features of Herndurabi Island. According to the information acquired, a feasibility study and design practice have been conducted to achieve a reasonable solution to equip Hendurabi Island as a sample with a self-sufficient prefabricate resort hotel. Findings indicate that the volumetric prefabricated modules would be a solution to devising a framework for design and construction in remote regions.

• Imaging Science in Dentistry
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• 제44권1호
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• pp.37-41
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• 2014

Purpose: The aim of this study was to investigate the accuracy of cone-beam computed tomography (CBCT) in the diagnosis of vertical root fractures in a tooth with gutta-percha and prefabricated posts. Materials and Methods: This study selected 96 extracted molar and premolar teeth of the mandible. These teeth were divided into six groups as follows: Groups A, B, and C consisted of teeth with vertical root fractures, and groups D, E, and F had teeth without vertical root fractures; groups A and D had teeth with gutta-percha and prefabricated posts; groups B and E had teeth with gutta-percha but without prefabricated posts, and groups C and F had teeth without gutta-percha or prefabricated posts. Then, the CBCT scans were obtained and examined by three oral and maxillofacial radiologists in order to determine the presence of vertical root fractures. The data were analyzed using IBM SPSS 20.0 (IBM Corp., Armonk, NY, USA). Results: The kappa coefficient was $0.875{\pm}0.049$. Groups A and D showed a sensitivity of 81% and a specificity of 100%; groups E and B, a sensitivity of 94% and a specificity of 100%; and groups C and F, a sensitivity of 88% and a specificity of 100%. Conclusion: The CBCT scans revealed a high accuracy in the diagnosis of vertical root fractures; the accuracy did not decrease in the presence of gutta-percha. The presence of prefabricated posts also had little effect on the accuracy of the system, which was, of course, not statistically significant.

• 대한치과보철학회지
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• 제54권2호
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• pp.93-102
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• 2016

목적: 본 연구의 목적은 내부육각 연결형 임플란트에서 두 가지 지르코니아 지대주와 티타늄 지대주의 변연 및 내면 적합도를 비교하고자 하였다. 재료 및 방법: 티타늄 지대주와 두 종류의 지르코니아 지대주를 내부육각연결 구조형 임플란트(TSV, Zimmer)에 체결하였다. 기성 티타늄 지대주(Hex-Lock, Zimmer)를 대조군으로 하여, 기성 지르코니아 지대주(ZirAce, Acucera)와 copy milling 시스템(Zirkonzahn Max, Zirkonzahn)으로 제작한 맞춤형 지르코니아 지대주를 비교하였다. 임플란트 고정체에 30 Ncm의 토크로 지대주를 연결하였으며, 각 실험군 당 8개의 시편을 제작하였다. 아크릴 레진에 포매하여 절단시편을 제작한 후 주사전자현미경으로 고정체-임플란트 계면에서 변연간극과 내부육각 내면간극을 측정하고, 지대주 나사와 지대주 나사받침 사이 계면에서 수직 및 수평간극을 측정했다. 측정치는 일원배치분산분석과 Scheffe test로 통계 처리하였다(${\alpha}=0.05$). 결과: 맞춤형 지르코니아 지대주의 변연 간극은 두 가지 기성 지대주에 비해 컸다. 내부육각 내면간극은 맞춤형 지르코니아 지대주와 기성 지르코니아 지대주 사이에 유의차를 보이지 않았고 기성 티타늄 지대주보다 컸다. 기성 지르코니아 지대주의 지대주 나사 수직간극과 수평간극은 기성 티타늄 지대주보다 컸다. 맞춤형 지르코니아 지대주의 경우. 지대주 나사 수평간극은 두 가지 기성 지대주보다 컸으며, 지대주 나사 수직간극을 측정할 수 없었다. 기성 지르코니아 지대주는 나사받침이 명확하게 형성되어 있었으나, 나사받침의 형태가 지대주 나사와 조화되지 않았다. 맞춤형 지르코니아 지대주의 경우에는 나사받침이 명확하게 형성되어 있지 않았다. 결론: 내부육각 연결형 임플란트에서 기성 티타늄 지대주가 두 종류의 지르코니아 지대주보다 적합도가 좋았다. 맞춤형 지르코니아 지대주는 두가지 기성 지대주에 비해 변연간극이 크고 나사와 나사받침 사이의 적합도가 낮았다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1400-1407
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• 2005

There are a number of approaches to in situ remediation that are used at contaminated sites for removing contaminants from the contaminated zone without excavating the soil. These include soil flushing, dual phase extraction, and soil vapor extraction. Of these techniques, soil flushing is the focus of the investigation in this paper. The concept of using prefabricated vertical drains(PVDs) for remediation of contaminated sites with fine-grained soils is examined. The PVD system is used to shorten the drainage path or the groundwater flow and promote subsurface liquid movement expediting the soil flushing process. The use of PVDs in the current state of practice has been limited to soil improvement. The use of PVDs under vacuum conditions is investigated using sample soil consisting of silty sand.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4322-4327
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• 2015

하수관거 시설은 현장 시공시 다짐 불량 및 뒤채움재의 품질관리 미흡으로 인해 하수관거의 이격 및 부등침하가 발생되고, 이음부나 관의 손상이 심화되는 경우 누수가 발생된다. 노후화로 인해 유지 및 보수, 신설 비용은 매년 증가하고, 누수로 인한 인접 매립시설물 및 지하수로의 유입으로 인해 오염사례가 보고된 바 있으며, 최근에는 싱크홀의 문제를 야기하여 사회적 관심이 증대되었다. 따라서 많은 연구자들에 의해 하수관거의 기초에 대한 채움재관련 연구가 오랫동안 연구되어 왔으며, 신재생재료에 대한 관심 수요가 증가하여 재생재료를 활용한 연구들도 활발히 진행되고 있다. 본 연구에서는 하수관거를 지지하는 기초의 안전성과 경제성을 동시에 지닌 재활용재료를 활용한 조립식 하수관거 기초에 대해 연구를 진행하였으며, 사후처방방식이 아닌, 시공단계에서 사전예방하기 위해 관경 600mm, 700mm, 800mm의 대형 하수관거를 선정하여 적절한 설계 하중을 산출하고 매립 심도별 안전성에 관한 연구를 수행하였다. 본 연구결과는 신형식 하수관거 기초의 유사연구에 널리 활용 될 수 있을 것이다.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.605-610
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• 2011

간척지나 해안지역과 같은 연약지반에 건축 및 토목공사를 위해서는 지반의 강도를 높이기 위한 연약지반개량공사가 필수적이다. 연약지반 개량 공법은 여러 가지가 있으나 우리나라를 비롯해 세계적으로 연직배수공법을 주로 사용하고 있다. 연직배수공법은 연약한 점성토 지반 내에 인공적으로 연직 배수재를 다수 설치하여 배수거리를 단축시킴으로써 압밀을 촉진시키고, 그에 따른 강도증가 효과를 얻을 수 있는 공법이다. 연직배수재로는 경제성과 시공성이 우수한 PBD가 널리 사용되고 있다. PBD 시공품질은 시공 깊이, 압력, 수직도 등에 영향을 받게 된다. 본 논문에서는 PBD 시공시 배수재의 시공 심도, 압력, 수직도를 자동측정하여 작업자가 실시간으로 모니터링 할 수 있고 시공결과를 자동 저장하는 시스템을 개발하였다. 개발된 시스템은 시공 불량 요인이 발생시 자동 경고하여 불량률을 줄일 수 있고, 장비의 이상 발생시 자동 제어시스템을 가동하여 작업의 안전성을 확보하도록 하였다.

• Computers and Concrete
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• 제22권3호
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• pp.327-336
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• 2018

Increase in population and its daily increasing in our today society results in an increase in housing demand while traditional methods are not applicable. The project preparation and realization processes, based on theoretical and empirical studies, a creation of goods, services, and technologies, are the most important human activities. Selection of effective technological systems in construction is a complex multi-criteria decision-making task. Many decision-makers refuse innovations once faced with similar difficulties. Therefore, using modern materials and methods in this industry is necessary. Modern methods increase quality and construction speed in addition to decrease energy consumption and costs. One of the problems in the way of any project is selecting construction system compatible with the project needs and characteristics. In the present research, different concrete structures such as common reinforced concrete (RC) structure, prefabricated, Insulating Concrete Formwork (ICF), 3D Panel and Tunnel Concrete Formwork (TCF) for buildings with limited floors in Iran are studied and compared from the viewpoint of different criteria like cost, time, applicability and technical characteristics with industrialization approach. Therefore, some questionnaires filled out by construction industry experts in order to compare criteria and sub-criteria in addition to evaluation of optimized structural systems. Then, results of the questionnaires ranked by Analytic Hierarchy Process (AHP) and the most effective alternative selected. The AHP results show that 3D Panel system 36.5%, ICF 21.7%, TCF 19.03%, prefabricated system 13.3% and common RC system 9.3% are the most and the least efficient systems respectively.