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초고층 건물의 기둥 축소량 계측 결과를 통한 기존 제안식 평가

Title
초고층 건물의 기둥 축소량 계측 결과를 통한 기존 제안식 평가
Other Titles
Evaluation of Equations Predicting Column Shortening Using Column Shortening Data Obtained From Field Measurement
Author
추헌필
Alternative Author(s)
Chu, Heon-Pil
Advisor(s)
한상환
Issue Date
2007-08
Publisher
한양대학교
Degree
Master
Abstract
국가 경제의 성장과 국민소득의 향상으로 우리나라에서도 초고층 건물이 증가함에 따라 이에 관한 연구가 활발하게 진행되고 있다. 일반적으로 초고층 건물은 폭과 높이 비 즉, 세장비가 1:5 이상인 50층 정도 이상을 정의하고 있다. 이러한 초고층 건축에 있어서 가장 중요하게 인식하고 해결해야 할 과제는 건물의 구조적 안전성과 사용성의 향상이라고 할 수 있다. 초고층 건물의 구조적 특징을 둘로 요약하면 지진, 풍하중 등 수평 외력에 저항할 전단내력벽이 필요하다는 것과 층수가 높아짐으로 인하여 큰 압축력을 받게 되는 수직부재의 길이가 줄어든다는 점이다. 언급한 두 가지 문제 중 전자는 그 설계방법이 정착단계에 이르렀으나, 후자는 1960년대 말 미국에서 시작된 이래 각국에서 다수의 제안과 연구가 이루어졌음에도 그 이론적 체계를 입증할 현장의 경험적 자료가 충분하지 못하였다. 이것이 이 분야에 있어서 산학 공동 협력을 기반으로 한 심층적인 연구와 예측에 관한 기술 개발을 필요로 하는 이유이다. 따라서 본 연구에서는 기둥 축소량 예측에 관한 Mark Fintel 등의 기존 이론식들을 조사하여 고찰하고, 부산 온천동에 소재한 SK 허브 스카이 49층 타워동을 대상으로 측정한 현장 계측결과를 해석값과 비교분석하여 기존 제안식의 타당성을 검증 평가하였다. 비교 결과, 공사 초기에는 두 데이터가 잘 일치하다가 지상 18층 이후부터 계측값의 추이에 현저한 변화가 발생하였다. 그 원인은 철근콘크리트 라멘구조의 골조효과로 인한 영향으로 일반 구조해석과 시공 단계를 고려한 구조해석에 의하여 검증되었다. 따라서 현장 계측과 시공 단계를 고려한 정밀한 구조해석을 통하여 기존 제안식의 개선이 필요하다는 결론을 얻을 수 있었다.
Recently, the construction of high-rise buildings has been increasing in the urban center of large cities to meet changes in the needs of social living trends, or as an alternative for efficient land development. There are two outstanding structural aspects for such tall buildings. One of them is that they require vertical diaphragm walls to resist lateral pressure and forces like wind and seismic loads. Another, is that vertical members, like columns, shorten, therefore the shortening has to be controlled and compensated properly during construction. This study concentrates on the structural analysis of columns to predict shortening values and the field observations required to verify these predictions. Columns shortening of tall buildings should be carefully considered due to its impact not only on the safety due to structural stresses caused between adjacent columns and the core wall but also due to the deflection of finishing works, such as the exterior curtain wall, interior partitions and mechanical plumbing joints with elevator rails. For the purpose of the abovementioned structural solution, at first, theoretical equations proposed for the prediction of column shortening were reviewed. Secondly, field observations are proposed on a tall structure as an example. The objective project is a two 49-story residential towers and commercial building complex, SK Hub Sky, which is located in Oncheon-dong, Dongnae-gu, Busan city. The structural system designed for the towers is a beams and columns reinforced concrete frame with a shear core wall. The construction started in January 2003, and was completed in October 2006, which progressed in 5 to 6 actual working days for typical floors in structure. 102 numbers of vibrating wire strain gauges were placed in specific vertical members. To calculate preliminary prediction of column shortening, PCA model equations proposed by Mark Fintel, S.K. Ghosh and Iyengar were adopted together with relevant sections of the ACI Code. Calculated shortening amounts were compensated on lumped floors for the relevant structural members and finishing details were improved to absorb deflection subsequent to construction. The column shortening phenomenon is caused by elastic displacement due to initial load increment depending on the modulus of elasticity and inelastic strain of concrete shrinkage and creep. Especially, creep and drying shrinkage are time-dependent parameters that behave in shortening for many years. For the actual property input and probable prediction, not only laboratory and field tests with field observation should be conducted, but ambient environment conditions like relative humidity and rates of construction should be considered according to the stepped progress of construction. Analytical prediction has been done to three steps such as preliminary, basic and revised tasks, and the final results have been compared with measured values through embedded instruments for cause and effect analysis. Significant differences between the two sets of data were found by frame action effect to transfer load and stress between connected frames by work progress. The trends of strain on core wall and columns appeared reversed to each other above the 18th floor. Measurement values at the core wall showed more shortening, while columns shortened less than the calculated amounts. The cause was verified under comparison by structural analysis of individual vertical members and considered the behavior by the progressive load increments. Bending moment diagrams show two different values induced by transferred load among the structural members of connected frames. In conclusion, the two data of strain measurements from the field and as analyzed by the proposed equations matched up to the 18th floors, which occurred 232 days after casting concrete at column A6 and core wall on the 1st floor , but the strains measurements on floors above the 18th floor do not equalize to the preliminary predicted strain curves. Therefore column shortening in reinforced concrete systems of high rise buildings should be calculated by progressive structural analysis considered for the frame action. In this regard, field observations with instruments and experimental laboratory tests are required for verifying prediction value obtained from the proposed equations as closely as structures move substantially. Further to this study for the future, firstly material properties of concrete such as volume fraction related with its composition should be researched and studied deeply in order to obtain less shortening. Secondly, an effective program with analytical equations to be reflected on progressive loading effect should be also studied and developed accordingly. Also, reinforcing ratio, loading ratio, stress ratio of structural members, and the shapes of core wall and columns should be initially designed in order to maintain structural balance for the purpose of minimizing columns shortening.
URI
https://repository.hanyang.ac.kr/handle/20.500.11754/149123http://hanyang.dcollection.net/common/orgView/200000407645
Appears in Collections:
GRADUATE SCHOOL OF ENGINEERING[S](공학대학원) > ARCHITECTURAL ENGINEERING(건축공학과) > Theses(Master)
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