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Verification of Shear Live-load Distribution Factor Equations for I-Girder Bridges
Nakin Suksawang,Hani Nassif,Dan Su 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.3
The “S-over” Load Distribution Factor (LDF) has been used for many years for determining the distributed moments and shear forces of a girder. Only until recently after the adaptation of the AASHTO LRFD Bridge Design Specification, new LDF equations are proposed using power functions. Although these new equations can more accurately predict the distributed moments and shear forces similar to both field and finite element analysis results, they are complex and they do not represent the fundamental background of LDF but rather based on regression analysis. Therefore, a more fundamental equation such as the S-over LDF is needed for the engineer to have a better understanding of the relationship between the girder sizes and spacing. The primary objective of this study is to develop a simplified S-over LDF for shear for steel and prestressed concrete I-girder bridges. Actual field testing of seven I-girder bridges were evaluated and validated to the developed Finite Element Analysis (FEA) model. A parametric study of bridges with various girder spacing and length were performed to develop the proposed equations. Results show that the proposed equations have excellent correlation with the more exact FEA model as well as the computer-based analysis.
Assessment of Concrete Structures Using Structural Health Monitoring (Shm)
Hani Nassif,Nakin Suksawang,Joseph Davis 한국콘크리트학회 2011 한국콘크리트학회 학술대회 논문집 Vol.2011 No.5
Structural Health Monitoring (SHM) of structures during construction, as well as over its service life, has recently become more attractive to owners and consulting engineers. With the introduction of new materials and construction methods, various types of structures are being instrumented with monitoring devices to determine their performance as well as their response to various loading conditions. Among many other objectives, this includes monitoring concrete cracking behavior, measuring time-dependent deformations such as creep and shrinkage, camber and deflection, and validation of new design or construction provisions. This paper highlights various types of instrumentation techniques used to monitor and test concrete structures during construction in New Jersey. For each case study, various types of sensors are installed on the structure for field-testing and long-term monitoring. These sensors consist of strain transducers, accelerometers, geophones, vibrating wire strain gages, settlement sensors, pressure cells, and weigh in motion (WIM) system. This paper also provides an overview how data from various sensors could be processed to assess the actual behavior of the structure at various stages. Results of research work are employed to enable New Jersey Department of Transportation (NJDOT) to successfully update their design provisions.
Ridge and field tile aerodynamics for a low-rise building: a full-scale study
Tecle, Amanuel,Bitsuamlak, Girma T.,Suskawang, Nakin,Chowdury, Arindam Gan,Fuez, Serge Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.16 No.4
Recent major post-hurricane damage assessments in the United States have reported that the most common damages result from the loss of building roof coverings and subsequent wind driven rain intrusion. In an effort to look further into this problem, this paper presents a full-scale (Wall of Wind --WoW--) investigation of external and underneath wind pressures on roof tiles installed on a low-rise building model with various gable roofs. The optimal dimensions for the low-rise building that was tested with the WOW are 2.74 m (9 ft) long, 2.13 m (7 ft) wide, and 2.13 m (7 ft) high. The building is tested with interchangeable gable roofs at three different slopes (2:12; 5:12 and 7:12). The field tiles of these gable roofs are considered with three different tile profiles namely high (HP), medium (MP), and low profiles (LP) in accordance with Florida practice. For the ridge, two different types namely rounded and three-sided tiles were considered. The effect of weather block on the "underneath" pressure that develops between the tiles and the roof deck was also examined. These tests revealed the following: high pressure coefficients for the ridge tile compared to the field tiles, including those located at the corners; considerably higher pressure on the gable end ridge tiles compared to ridge tiles at the middle of the ridge line; and marginally higher pressure on barrel type tiles compared to the three-sided ridge tiles. The weather blocking of clay tiles, while useful in preventing water intrusion, it doesn't have significant effect on the wind loads of the field tiles. The case with weather blocking produces positive mean underneath pressure on the field tiles on the windward side thus reducing the net pressures on the windward surface of the roof. On the leeward side, reductions in net pressure to a non-significant level were observed due to the opposite direction of the internal and external pressures. The effect of the weather blocking on the external pressure on the ridge tile was negligible.
권태석(Taesuk Kwon),이학준(Hakjoon Lee),이준환(Joonhwan Lee),설승기(Seungki Sul),이선우(Seonwoo Lee),박철규(Cheolgyu Park),김낙인(Nakin Kim) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
본 논문에서는 복합형 하이브리드 굴삭기의 전력 변환 장치의 구조 및 제어 방법을 제안한다. 제안된 전력 변환 장치는 엔진 다이나모 장치를 이용하여 그 타당성을 입증하였으며, 제한된 실험 환경 내에서도 기존의 유압식 굴삭기와 비교하였을 때, 약 8% 정도의 연비 향상의 효과를 얻을 수 있었다. 현재 실제 굴삭기에 장착하여 성능과 연비 측정을 위한 실험이 진행 중이다.