현수교(懸垂橋)의 비틀림진동(振動)에 관한 연구(硏究)

민창식,김생빈,손승요,Min, Chang Shik,Kim, Saeng Bin,Son, Seong Yo 대한토목학회 1983 대한토목학회논문집 Vol.3 No.3

본(本) 연구(硏究)는 경기도(京畿道) 설계심의회(設計審議會)에서 천마산(天馬山) 청소년(靑少年) 심신수련장(心身修練場) 현수교(懸垂橋) 설계심의시(設計審議時) 현수교(懸垂橋)의 동적(動的) 거동(擧動)에 대한 설계미비(設計未備)의 원인(原因)이 아직도 체계화(體系化)되지 못한 우리 나라 현수교(懸垂橋)의 설계자료(設計資料)와 지침(指針)의 불비(不備)함에 그 동기(動機)를 얻어, 유한요소법(有限要素法)을 적용(適用)하여 현수교(懸垂橋)의 비틀림진동(振動)에 대한 고유진동수(固有振動數)와 이에 상응(相應)하는 고유진동형(固有振動形)을 구(求)하였다. 실제(實際)로 현수교(懸垂橋)의 일반적(一般的) 거동(擧動)은 수직(垂直) 수평면(水平面) 내(內)에서의 연성(連成)된 운동(運動)으로 표시(表示)되지만 사용목적(使用目的)에 부합(附合)하여 그 진폭(振幅)을 미소(微小)하도록 제한(制限)하면 수직(垂直) 비틀림 진동(振動)은 단독(單獨)으로 비연성화(非連成化)할 수 있으며, 이에 따라 해석하였다. 1973년 6월에 개통된 Streamlined Box-Girder Type인 남해대교(南海大橋)와 Lateral Bracing으로 이루어진 단경간의 천마산(天馬山)의 현수교(懸垂橋)의 설계자료(設計資料)를 이용하여 수치해(數値解)를 얻었으며, 천마산(天馬山) 현수교(懸垂橋)의 경우(境遇) 보조(補助) 보강(補强)케이블의 유무(有無)에 따른 고유진동수(固有振動數)와 진동형(振動形)을 구(求)하여 비교(比較) 검토(檢討)하였다. 보강(補强)케이블의 유무(有無)에 따라 초기의 진동수(振動數) 등에서는 그 영향이 매우 뚜렷하였으나, 진동형(振動形)이 복잡해짐에 따라 보강(補强)케이블의 영향은 미약했거나 또는 오히려 역효과를 가져왔다. 남해대교(南海大橋)에 있어서 유한요소기법(有限要素技法)과 전자계산기에 의해 본(本) 연구(硏究)에서 구한 고유진동수(固有振動數)와 남해대교(南海大橋) 건설지(建設誌)에 있는 Frequency Equation으로 구한 값 또는 풍동실험(風洞實驗)에 의한 결과(結果) 등과 비교(比較) 검토(檢討)하였으며, 비교(比較) 결과(結果) 좋은 일치(一致)를 보여주었다. A method of dynamic analysis is developed for torsional free vibrations of elliptical-box girder type or stiffening truss system suspension bridge. In this study, the method based on a finite element technique using a digital computer, is illustrated by two numerical examples, the Namhae Bridge which is located in Kyungsang nam-do opened on June, 1973, and the Mt. Chunma Bridge is simple span pedestrian's suspension bridge with lateral bracing system in Mt. Chunma, Kyungki-do, are used. In general, dynamic modes of complex suspension bridges are three-dimensional in form, i.e., coupling between vertical and torsional motions. However, introduced that amplitudes of oscillation are infinitesimal for coincidence with the purpose of it's use, thereupon, the torsional vibration analyses are treated without coupling terms. A sufficient number of natural frequencies and mode shapes for torsional free vibration are presented in this paper. In the case of Mt. Chunma Bridge, the natural frequencies and periods are computed with and without reinforcement, respectively, and compared their discrepancies. The influence of the auxiliary reinforcing cables is prevailing in the first few modes, namely, 1st and 2nd in symmetric and 1st, 2nd and 3rd in antisymmetric vibration, and conspicuous in the symmetric compared with the antisymmetric motion, but in the higher modes, this kind of simple accessory elucidates rether converse effects. In the Namhae Bridge, the results are compared with the Manual's obtained by wind tunnel test. It reveals commendable agreement.

Ultimate Behavior of Reinforced Concrete Hyperbolic Cooling Tower

민창식,김생빈,Min, Chang Shik,Kim, Saeng Bin Korean Society of Civil Engeneers 1992 대한토목학회논문집 Vol.12 No.4

Inelastic nonlinear behavior of a hyperbolic cooling tower under wind loading is studied using a finite element program developed on a Cray Y-MP. Convergence studies for the elastic and inelastic analyses are performed using three mesh models. It is shown that the mesh convergence plays an important role in accurately predicting the inelastic behavior of a cooling tower. Even though the cooling tower resists the applied forces through membrane stresses, it is found that the bending stresses play an important role in the failure and behavior of the cooling tower. The present analysis gives a shape factor of 1.48, which indicates a significant redistribution of meridional stresses. It is further evidenced by the distribution of meridional reinforcement yielding which reaches up to $30^{\circ}$ from the windward meridian. The present practice of using elastic analysis for calculating the design stresses appears to be at least safe and conservative. A more comprehensive study should lead to conclusions that would allow use of a higher-than-one shape factor, thus requiring less meridional reinforcement than the present design method does.

Investigation on R/C Hyperbolic Paraboloid (HP) Saddle Shell Ultimate Behavior

민창식,김생빈,Min, Chang Shik,Kim, Saeng Bin Korean Society of Civil Engeneers 1993 대한토목학회논문집 Vol.13 No.2

Nonlinear inelastic behavior of an HP saddle shell has been examined by a finite element computer program developed on a Cray Y-MP. The mesh convergence is studied using three progressively refined finite element mesh models, $16{\times}16$, $32{\times}32$ and $64{\times}64$, for the elastic and inelastic analyses. It is shown that the $32{\times}32$ mesh model gives a solution that is very close to that given by the $64{\times}64$ mesh model, thus, showing a convergence. The inelastic analysis shows that the shell has a tremendous capacity to redistribute the stresses. At the ultimate, the concrete cracks and the reinforcement yieldings are spread out all over the shell, indicating that the stress distribution in the shell is approaching that given by the classical membrane theory. The present computer program provides a very useful tool for evaluating the nonlinear ultimate behavior of concrete shells during the design process.

철근콘크리트 쌍곡 '안장' 쉘의 설계 예와 극한거동

민창식,Min, Chang Shik,Gupta, Ajaya K. 대한토목학회 1994 대한토목학회논문집 Vol.14 No.4

One case of pointwise limit design is performed for a hyperbolic paraboloid saddle shell(originally used by the Lin-Scordelis) to check the design strength against a consistent design loads, therefore, to verify the adequacy of current design practice for reinforced concrete shells. The design method which was based on stresses from membrane analysis in conjunction with pointwise limit state design equations shows a good performance, which means that the design method gives a lower bound on the ultimate load. This shows the adequacy of the current practice at least for this saddle shell case studied. To generalize the conclusion many more designs-analyses are performed with different shell configurations.

보 및 1방향 슬래브의 균열제어

민창식(Chang-Shik Min) 한국콘크리트학회 2012 콘크리트학회논문집 Vol.24 No.4

철근콘크리트 쉴구조물의 극한거동에 대한 인장강성 효과

민창식 ( Min¸ Chang-shik ),김병진 ( Kim¸ Byoung-jin ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표회 논문집 Vol.4 No.2

After cracking, concrete tensile stresses drop to zero rapidly at the side of crack and the direction that normal to the crack. But the tensile stresses are transferred from the reinforcement to concrete through bond-slip between the reinforcement and the surrounding concrete. The concrete ability which still carries a part of the applied load, after cracking, is known as tension stiffening. Lin’s model and Izumo's model are used in this study for tension stiffening and implemented in a computer program developed by Min and Gupta. We choose a hyperbolic saddle shell problem originally used by Lin and Scordelis for comparing the performance of various tension stiffening models. The result of Lin’s model showed that the ultimate load and tip displacement are increasing as the tension stiffening parameter increase. The load-deflection curve with Izumo’s tension stiffening model showed the behavior of the curve and the calculated ultimate strength is quite close with r =15 case of Lin's model. In comparing this study's result with Mahmoud-Gupta’s result, it is showed that the results of ultimate load and tip displacement of Mahmoud-Gupta's program is about 8 ~ 18% higher than the result of present study. Mahmoud-Gupta considered the tension stiffening effect with unrealistic behavior as we recognized. It is considered that we need to study and analyze many more RC shell structures to develope appropriate tension stiffening model.

전단과 비틀림모멘트 설계의 조합

민창식(Chang-Shik Min) 한국콘크리트학회 2011 콘크리트학회논문집 Vol.23 No.1

직접인장실험에 의한 탄소섬유와 유리섬유의 하이브리드 조합분석

송형수(Song, Hyung Soo),민창식(Min, Chang Shik),이진용(Lee, Chin Yong) 한국구조물진단유지관리학회 2009 한국구조물진단학회 학술발표회논문집 Vol.2009 No.2

This study was undertaken to analyze the mechanical properties through an experiment by proposing the manufacturing method for the uniaxial tensile specimen following the combination of the high-tension carbon fiber and the E-glass fiber. The tensile strength of the HFRP-D specimen for which the ductile K-type epoxy was used came close to the tensile strength of the composite materials presented by Manders et al. only in the specimen(D10, D9, and D8) that showed its yielding point. In this specimen, the yielding point was close to the deformation rate when the CFRP was destroyed and when the hybrid performance was analyzed as it occurred.

프리스트레스트 프리캐스트 더블 티형보의 최적설계

유승룡(Yu, Sung-Yong),민창식(Min, Chang-Shik) 한국콘크리트학회 1999 콘크리트학회논문집 Vol.11 No.6

변단면 프리스트레스트 콘크리트 보의 최적화 설계에 관한 연구

최준(Choi Jun),민창식(Min Chang-Shik) 한국구조물진단유지관리학회 2001 한국구조물진단학회 학술발표회논문집 Vol.- No.-