• 한국구조물진단유지관리공학회 논문집
• /
• 제6권3호
• /
• pp.129-138
• /
• 2002

The purpose of this study is to propose the nonlinear analysis method which combines the nonlinear incremental method with the layered method to solve the problems due to the geometric and the material nonlinearities. As numerical analysis models, the reinforced concrete simple beam and the steel arch frame are used to verify the algorithm of the proposed nonlinear method. The results are gotten from the computation procedures. According to the results of this study, the fracture pattern of the beam according to the ratio of tensile steel and the strength of the concrete and the steel can be estimated by the proposed method. Therefore, the load-deflection curve of structure can be, exactly, depicted by the proposed method. Also, the rupture load, the site and the depth of crack of the beam can analytically be checked by the proposed method. In this respect, the proposed method contributes for the solving the stability problem of the actual structure.

• 콘크리트학회지
• /
• 제8권6호
• /
• pp.223-234
• /
• 1996

본 논문에서는 단조증가하중을 받는 철근 및 프리스트레스트 콘크리트 슬래브의 비선형거동, 즉 탄성, 비탄성, 극한영역에 이르기까지의 모든 하중이력에 대한 응력-변형도 관계와 균열의 진행 및 철근 및 텐던과 콘트리트의 응력과 변형도 등을 정확히 해석할 수 잇는 해석법의 제시를 목적으로 한다. 이러한 목적을 위하여 본 연구에서는 재료적 및 기하학적 비선형성을 고려하였다. 기하학적 비선형성은 Von Karman의 가정에 기본을 둔 total Lagrangian formulation에 의해 고려하였으며 재료적 비선형성에 대해서는 균열콘크리트에대한 인장, 압축, 전단모델과 콘크리트 중에 있는 철근 및 텐던모델을 조합하여 고려하였다. 이에 대한 콘크리트의 균열모델로서는 분산균열모델을 사용하였으며, 철근 및 텐던에 대해서는 1축 응력상태로 가정하여 등가의 분산분포된 철근 및 텐던층으로 모델화하였다. 본 논문에서 제안한 해석방법의 타당성을 검증하기 위하여 몇 개의 실험치를 해석치와 비교.검토한 결과, 본 논문의 해석방법에 의하면 철근 및 프리스트레스트 콘크리트 슬래브의 비선형거동을 보다 정확하게 예측할 수 있었다.

• Wind and Structures
• /
• 제20권2호
• /
• pp.249-274
• /
• 2015

Long-span cable-stayed bridges exhibit some features which are more critical than typical long span bridges such as geometric and aerodynamic nonlinearities, higher probability of the presence of multiple vehicles on the bridge, and more significant influence of wind loads acting on the ultra high pylon and super long cables. A three-dimensional nonlinear fully-coupled analytical model is developed in this study to improve the dynamic performance prediction of long cable-stayed bridges under combined traffic and wind loads. The modified spectral representation method is introduced to simulate the fluctuating wind field of all the components of the whole bridge simultaneously with high accuracy and efficiency. Then, the aerostatic and aerodynamic wind forces acting on the whole bridge including the bridge deck, pylon, cables and even piers are all derived. The cellular automation method is applied to simulate the stochastic traffic flow which can reflect the real traffic properties on the long span bridge such as lane changing, acceleration, or deceleration. The dynamic interaction between vehicles and the bridge depends on both the geometrical and mechanical relationships between the wheels of vehicles and the contact points on the bridge deck. Nonlinear properties such as geometric nonlinearity and aerodynamic nonlinearity are fully considered. The equations of motion of the coupled wind-traffic-bridge system are derived and solved with a nonlinear separate iteration method which can considerably improve the calculation efficiency. A long cable-stayed bridge, Sutong Bridge across the Yangze River in China, is selected as a numerical example to demonstrate the dynamic interaction of the coupled system. The influences of the whole bridge wind field as well as the geometric and aerodynamic nonlinearities on the responses of the wind-traffic-bridge system are discussed.

• Structural Engineering and Mechanics
• /
• 제20권6호
• /
• pp.609-630
• /
• 2005

A reliability analysis method is proposed in this paper through a combination of the advantages of the response surface method (RSM), finite element method (FEM), first order reliability method (FORM) and the importance sampling updating method. The accuracy and efficiency of the method is demonstrated through several numerical examples. Then the method is used to estimate the serviceability reliability of cable-stayed bridges. Effects of geometric nonlinearity, randomness in loading, material, and geometry are considered. The example cable-stayed bridge is the Second Nanjing Bridge with a main span length of 628 m built in China. The results show that the cable sag that is part of the geometric nonlinearities of cable-stayed bridges has a major effect on the reliability of cable-stayed bridge. Finally, the most influential random variables on the reliability of cable-stayed bridges are identified by using a sensitivity analysis.

• Computers and Concrete
• /
• 제14권6호
• /
• pp.657-674
• /
• 2014

The purpose of this paper is to present a numerical procedure to analyse reinforced concrete columns subjected to combined axial loads and bending that rigorously considers nonlinear material and nonlinear geometric characteristics. Column design and stability analysis are simultaneously regarded. A finite element method is used for calculating displacements and the material and geometric nonlinearities are taken into account using an iterative process. A computer program is developed from the proposed numerical procedure, and the efficiency of the program is verified against available experimental data. The model applies to constant rectangular cross sectional columns with symmetric reinforcement distribution.

• Wind and Structures
• /
• 제23권6호
• /
• pp.485-503
• /
• 2016

To investigate the nonlinear aerostatic stability of the Hutong cable-stayed rail-cum-road bridge with ultra-kilometer main span, a FEM bridge model is established. The tri-component wind loads and geometric nonlinearity are taken into consideration and discussed for the influence of nonlinear parameters and factors on bridge resistant capacity of aerostatic instability. The results show that the effect of initial wind attack-angle is significant for the aerostatic stability analysis of the bridge. The geometric nonlinearities of the bridge are of considerable importance in the analysis, especially the effect of cable sag. The instable mechanism of the Hutong Bridge with a steel truss girder is the spatial combination of vertical bending and torsion with large lateral bending displacement. The design wind velocity is much lower than the static instability wind velocity, and the structural aerostatic resistance capacity can meet the requirement.

• Structural Engineering and Mechanics
• /
• 제5권5호
• /
• pp.541-552
• /
• 1997

In this paper the ultimate strength of the R/C cooling towers, which have initial imperfection and pre-cracked elements, is analyzed. The initial geometric imperfections arise from the unavoidable inaccuracies under the construction and the pre-cracks are assumed to be produced by the temperature stress gradients or cyclic loading under wind pressure and/or earthquake load. Both effects are strongly influenced on the strength of the R/C cooling tower shell structures. The reinforcing ratio is also the important factor to evaluate the ultimate strength of the R/C cooling tower shells. However we could not analyze these structures experimentally because of their large, analyses are the powerful schemes to evaluate the safety and reliability of these structures. The analyzed model is Port Gibson cooling tower shell. In the numerical analysis the geometric and material nonlinearities are taken into account.

• Structural Engineering and Mechanics
• /
• 제54권4호
• /
• pp.809-827
• /
• 2015

In this paper, seismic energy response of inelastic steel structures under earthquake excitations is investigated. For this purpose, a numerical procedure based on nonlinear dynamic analysis is developed by considering material, geometric and connection nonlinearities. Material nonlinearity is modeled by the inversion of Ramberg-Osgood equation. Nonlinearity caused by the interaction between the axial force and bending moment is also defined considering stability functions, while the geometric nonlinearity caused by axial forces is described using geometric stiffness matrix. Cyclic behaviour of steel connections is taken into account by employing independent hardening model. Dynamic equation of motion is solved by Newmark's constant acceleration method in the time history domain. Energy response analysis of space frames is performed by using this proposed numerical method. Finally, for the first time, the distribution of the different energy types versus time at the duration of the earthquake ground motion is obtained where in addition error analysis for the numerical solutions is carried out and plotted depending on the relative error calculated as a function of energy balance versus time.

• 대한토목학회논문집
• /
• 제11권1호
• /
• pp.79-87
• /
• 1991

본 논문에서는 단조증가하중을 받는 철근콘크리트 쉘구조의 탄성, 비탄성, 극한영역등 모든 응력상태에 대한 재료적(材料的), 기하학적(幾何學的) 비선형(非線形) 해석(解析)을 위해서 유한요소법에 의한 수치해법(數値解法)을 개발하였다. 유한요소로서는 면회전단변형을 고려하여 Degeneration 방법에 의해 유도된 8절점 Serendipity 등매개변수 요소를 사용하였으며, 두께방향에 대한 철근과 콘크리트의 재료성질을 고려하기 위하여 층상화기법(層狀化技法)을 도입하였다. 기하학적(幾何學的) 비선형성(非線形性)은 Von Karman의 가정에 기본을 둔 total Lagrangian formulation에 의해 고려하였으며, 재료적(材料的) 비선형성(非線形性)에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 중에 있는 철근모델을 조합하여 고려하였다. 이에 대한 콘크리트의 균열모델로서는 분산균열모델을 사용했으며, 철근에 대해서는 1축 응력상태로 가정하여 등가의 분산분포된 철근량으로 모델화하였다. 차후 논문( )의 수치예제를 통하여 본 논문의 해석방법이 기하학적(幾何學的), 재료적(材料的) 비선형성(非線形性)을 고려한 임의형상의 철근콘크리트 쉘구조의 해석에 적합한 방법임을 입증하고자 한다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
• /
• pp.181-182
• /
• 2009

본 연구에서는 축력과 2축 휨을 받는 철근콘크리트 장주의 장기 저항능력을 산정할 수 있는 비선형 해석 모델을 제안하였다. 제안된 모델에서는 콘크리트의 장기 거동에 의해 발생하는 비역학적 변형 및 P- $\Delta$효과로 인한 기하 비선형 뿐 만 아니라 콘크리트의 균열 및 철근의 항복 등 재료 비선형성이 고려되었다. 다른 연구자들의 실험 결과와의 비교를 통하여 제안된 모델을 검증 하였다.