• Structural Engineering and Mechanics
• /
• 제51권4호
• /
• pp.601-625
• /
• 2014

Based on continuum mechanics and the principle of virtual displacements, incremental total Lagrangian formulation (T.L.) and incremental updated Lagrangian formulation (U.L.) were presented. Both T.L. and U.L. considered the large displacement stiffness matrix, which was modified to be symmetrical matrix. According to the incremental updated Lagrangian formulation, small strain, large displacement, finite rotation of three dimensional Timoshenko fiber beam element tangent stiffness matrix was developed. Considering large displacement and finite rotation, a new type of tangent stiffness matrix of the beam element was developed. According to the basic assumption of plane section, the displacement field of an arbitrary fiber was presented in terms of nodal displacement of centroid of cross-area. In addition, shear deformation effect was taken account. Furthermore, a nonlinear finite element method program has been developed and several examples were tested to demonstrate the accuracy and generality of the three dimensional beam element.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2007년도 정기 학술대회 논문집
• /
• pp.283-288
• /
• 2007

This paper presents an analytical prediction of Nonlinear characteristics of prestressed concrete bridges by strengthened of externally tendon considering the work sequence, using beam-column element based on flexibility method and tendon element. The beam-column element was developed with reinforced concrete material nonlinearities which are based on the smeared crack concept. The fiber hysteresis rule of beam-column element is derived from the uniaxial constitutive relations of concrete and reinforcing steel fibers. The tendon element represent the bonded tendon and unbonded tendon behaviors. Beam-column element and tendon element was be subroutine A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of RC and PSC structures was used. The proposed numerical method for prestressed concrete structures by strengthened of externally tendon is verified by comparison with reliable experimental results.

• Structural Engineering and Mechanics
• /
• 제82권2호
• /
• pp.173-189
• /
• 2022

This study presents an experimental and numerically study about the effects of fiber reinforcement ratio on the behavior of concrete-filled steel tubes (CFST) under dynamic impact loading. In literature have examined the behavior of GFRP and FRP wrapped strengthened CFST elements impact loads. However, since the direction of potential impact force isn't too exact, there is always the probability of not being matched the impact force of the area where the reinforced. Therefore, instead of the fiber textile wrapping method which strengthens only a particular area of CFST element, we used fiber-added concrete-filled elements which allow strengthening the whole element. Thus, the effect of fiber-addition in concrete on the behavior of CFST elements under impact loads was examined. To do so, six simply supported CFST beams were constructed with none fiber, 2% fiber and 10% fiber reinforcement ratio on the concrete part of the CFST beam. CFST beams were examined under two different impact loads (75 kg and 225 kg). The impactors hit the beam from a 2000 mm free fall during the experimental study. Numerical models of the specimens were created using ABAQUS finite element software and validated with experimental data. The obtained results such as; mid-span displacement, acceleration, failure modes and energies from experimental and numerical studies were compared and discussed. Furthermore, the Von Misses stress distribution of the CFST beams with different ratio of fiber reinforcements were investigated numerically. To sum up, there is an optimum amount limit of the fiber reinforcement on CFST beams. Up to this limit, the fiber reinforcement increases the structural performances of the beam, beyond that limit the fiber reinforcement decreases the performances of the CFST beam under transverse impact loadings.

• Structural Engineering and Mechanics
• /
• 제51권1호
• /
• pp.89-110
• /
• 2014

In this study, two beam-column elements based on the Elasto-Fiber element theory for reinforced concrete (RC) element have been developed and compared with each other. The first element is based on Elasto Fiber Approach (EFA) was initially developed for steel structures and this theory was applied for RC element in there and the second element is called as Fiber & Bernoulli-Euler element approach (FBEA). In this element, Cubic Hermitian polynomials are used for obtaining stiffness matrix. The beams or columns element in both approaches are divided into a sub-element called the segment for obtaining element stiffness matrix. The internal freedoms of this segment are dynamically condensed to the external freedoms at the ends of the element by using a dynamic substructure technique. Thus, nonlinear dynamic analysis of high RC building can be obtained within short times. In addition to, external loads of the segment are assumed to be distributed along to element. Therefore, damages can be taken account of along to element and redistributions of the loading for solutions. Bossak-${\alpha}$ integration with predicted-corrected method is used for the nonlinear seismic analysis of RC frames. For numerical application, seismic damage analyses for a 4-story frame and an 8-story RC frame with soft-story are obtained to comparisons of RC element according to both approaches. Damages evaluation and propagation in the frame elements are studied and response quantities from obtained both approaches are investigated in the detail.

• Steel and Composite Structures
• /
• 제32권5호
• /
• pp.657-670
• /
• 2019

This paper proposes a one-dimensional fiber beam element model taking account of materially non-linear behavior, benefiting the highly efficient elastic-plastic analysis of girders with shear-lag effects. Based on the displacement-based fiber beam-column element, two additional degrees of freedom (DOFs) are added into the proposed model to consider the shear-lag warping deformations of the slabs. The new finite element (FE) formulations of the tangent stiffness matrix and resisting force vector are deduced with the variational principle of the minimum potential energy. Then the proposed element is implemented in the OpenSees computational framework as a newly developed element, and the full Newton iteration method is adopted for an iterative solution. The typical materially non-linear behaviors, including the cracking and crushing of concrete, as well as the plasticity of the reinforcement and steel girder, are all considered in the model. The proposed model is applied to several test cases under elastic or plastic loading states and compared with the solutions of theoretical models, tests, and shell/solid refined FE models. The results of these comparisons indicate the accuracy and applicability of the proposed model for the analysis of both concrete box girders and steel-concrete composite girders, under either elastic or plastic states.

• 대한토목학회논문집
• /
• 제26권4A호
• /
• pp.577-585
• /
• 2006

본 연구에서는 비선형 전단변형을 고려할 수 있는 Timoshenko보 이론을 정식화 하였다. 제안된 모델은 전단변형을 고려하므로서 짧은 기둥이나 전단 지배 기둥에서 일반적인 Bernoulli보 이론 보다 합리적인 결과를 보여준다. 단면은 층상화 모델을 이용하였으며, 층상화 단면 모델은 단면을 분활하여 소성화 진행과정을 관찰할 수 있으며 축력과 모멘트의 상호작용을 알 수 있다. 정식화한 요소는 일반적인 철근 콘크리트 부재의 해석을 위해 유한요소 프로그램에 적용하였다. 철근콘크리트 기둥의 해석을 실험결과와 비교하였고, 철근콘크리트 기둥에 대한 거동특성을 분석하였다.

• Steel and Composite Structures
• /
• 제27권5호
• /
• pp.567-576
• /
• 2018

The objective of this work is to analyze large deflections of a fiber reinforced composite cantilever beam under point loads. In the solution of the problem, finite element method is used in conjunction with two dimensional (2-D) continuum model. It is known that large deflection problems are geometrically nonlinear problems. The considered non-linear problem is solved considering the total Lagrangian approach with Newton-Raphson iteration method. In the numerical results, the effects of the volume fraction and orientation angles of the fibre on the large deflections of the composite beam are examined and discussed. Also, the difference between the geometrically linear and nonlinear analysis of fiber reinforced composite beam is investigated in detail.

• Journal of Mechanical Science and Technology
• /
• 제18권2호
• /
• pp.221-229
• /
• 2004

In this work, an elastic-plastic stress analysis has been conducted for silicon carbide fiber reinforced magnesium metal matrix composite beam. The composite beam has a rectangular cross section. The beam is cantilevered and is loaded by a single force at its free end. In solution, the composite beam is assumed perfectly plastic to simplify the investigation. An analytical solution is presented for the elastic-plastic regions. In order to verify the analytic solution results were compared with the finite element method. An rectangular element with nine nodes has been choosen. Composite plate is meshed into 48 elements and 228 nodes with simply supported and in-plane loading condations. Predictions of the stress distributions of the beam using finite elements were overall in good agreement with analytic values. Stress distributions of the composite beam are calculated with respect to its fiber orientation. Orientation angles of the fiber are chosen as $0^{circ},\;30^{circ},\;45^{circ},\;60^{circ}\;and\;90^{circ}$. The plastic zone expands more at the upper side of the composite beam than at the lower side for $30^{circ},\;45^{circ}\;and\;60^{circ}$ orientation angles. Residual stress components of ${\sigma}_{x}\;and \;{\tau}_{xy}$ are also found in the section of the composite beam.

• Structural Engineering and Mechanics
• /
• 제82권1호
• /
• pp.81-92
• /
• 2022

Ultra-high performance fiber reinforced concrete (UHPFRC) is a composite building material with high ductility, fatigue resistance, fracture toughness, durability, and energy absorption capacity. The aim of this study is to develop a nonlinear finite element model that can simulate the response of the UHPFRC beam exposed to impact loads. A nonlinear finite element model was developed in ABAQUS to simulate the real response of UHPFRC beams. The numerical results showed that the model was highly successful to capture the experimental results of selected beams from the literature. A parametric study was carried out to investigate the effects of reinforcement ratio and impact velocity on the response of the UHPFRC beam in terms of midpoint displacement, impact load value, and residual load-carrying capacity. In the parametric study, the nonlinear analysis was performed in two steps for 12 different finite element models. In the first step, dynamic analysis was performed to monitor the response of the UHPFRC beam under impact loads. In the second step, static analysis was conducted to determine the residual load-carrying capacity of the beams. The parametric study has shown that the reinforcement ratio and the impact velocity affect maximum and residual displacement value substantially.

• 한국강구조학회 논문집
• /
• 제22권6호
• /
• pp.543-551
• /
• 2010

층고 감소, 내력 증대 등의 장점을 가지고 있는 기존 합성보의 특징 뿐만 아니라 사용 강재량의 감소까지 기대할 수 있는 단부 보강한 합성보(Eco-girder) 시스템이 개발되었다. Eco-girder 시스템의 개념은 효율적인 합성보의 설계를 위해 최대 모멘트가 발생하는 양단부만을 강판을 이용하여 보강하고, 중앙부 모멘트에 의하여 철골보 크기를 결정하는 구조시스템이다. 본 연구에서는 반복 휨하중을 받는 단부보강 합성보의 이력거동을 예측하기 위해 정밀한 FEM(Finite Element Method)보다는 간단한 표현과 동시에 원리에 충실한 수치적분에 의한 면내수치해석방법(Fiber Element Analysis)을 이용하였으며, 선행 연구된 실험 결과와의 비교를 통해 수치해석방법의 타당성을 검증하였다. 또한 기존 합성보와의 이력거동을 비교 분석하였다.