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Panot Chobsilprakob,Songsak Suthasupradit,김기두 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2
A time domain approach for predicting the flutter response of long-span bridges was presented. The unsteady aerodynamic forces were presented by the indicial functions through a convolution integral, whereas the nonlinear least square method was used to calculate the aerodynamic indicial parameters. The nonlinear dynamic analysis which includes both the geometric and material nonlinearities due to the unsteady self excited aerodynamics force was considered. Numerical analyses were then performed using three dimensional finite element model of the suspension bridge. The results show that the geometric and material nonlinearities have a significant influence on the critical velocity and the response of long-span bridges.
Panot Chobsilprakob,김기두,Songsak Suthasupradit,Anaphat Manovachirasan 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.1
The design of cable supported bridge with long span is challenging due to the sensitivity of the dynamic excitation. Theaerodynamic instability caused by fluttering can severely affect the safe operation. An application of indicial function to the flutteranalysis in time domain is applied to the Great belt East Bridge for both completed and erection stage. The nonlinear least squaremethod was used to extract the aerodynamic indicial parameters for flutter analysis in time domain. The geometric nonlinearityis considered through the nonlinear dynamic analysis. The results showed the good agreement with the wind tunnel test and thevalidity of the indicial function as well as the important role of the geometrically nonlinear analysis during deck erection.
A nonlinear Co-rotational Quasi-Conforming 4-node Shell Element Using Ivanov-Ilyushin Yield Criteria
파노트 송삭 프라민,김기두,Panot, Songsak Pramin,Kim, Ki Du Korean Society of Steel Construction 2008 韓國鋼構造學會 論文集 Vol.20 No.3
율리신-이바노브 항복 조건을 이용하여 4절점 순수변위 준적합 쉘요소의 정식화를 제안하였다. 기하강성 행렬은 그린 변형률 텐서를 이용하여 휨변형률 및 전단변형률도 기하강성행렬에 고려되었다. 그 결과 접선강성행렬의 해석적인 적분으로 비선형 해석시 매우 효율적으로 계산이 되고 있다. 이 정식은 변형률 경화의 이바노브-유리신 항복조건을 이용하여 재료 비선형 해석시에도 쉽게 적분이 된다. 즉 두께 방향의 적층 적분을 하지 않는 율리신-이바노브의 정식은 대규모의 쉘 구조에도 계산상 아주 적합하다. 검증된 수치 예제에서 만족스러운 결과를 보여주고 있다. A co-rotational quasi-conforming formulation of four- node stress resultant shell elements using Ivanov-Ilyushin yield criteria are presented for the nonlinear analysis of plate and shell structure. The formulation of the geometrical stiffness is defined by the full definition of the Green strain tensor and it is efficient for analyzing stability problems of moderately thick plates and shells as it incorporates the bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. This formulation also integrates the elasto-plastic material behaviour using Ivanov Ilyushin yield condition with isotropic strain hardening and its asocia ted flow rules. The Ivanov Ilyushin plasticity, which avoids multi-layer integration, is computationally efficient in large-scale modeling of elasto-plastic shell structures. The numerical examples herein illustrate a satisfactory concordance with test ed and published references.