Fiber Element Analysis Research Articles

Shear Test and Nonlinear Finite Element Analysis of Hybrid Fiber Reinforced HPC Deep Beams

The shear behavior of 18 different groups of hybrid fiber (steel fiber and polypropylene fiber) reinforced HPC deep beams and 2 groups of HPC deep beams without fiber were discussed through experimental study and nonlinear finite element analysis. The shear tests were made under the static load and the finite element analysis software ABAQUS was used in numerical simulation. Results illuminate that hybrid fiber can significantly increase the diagonal cracking load and the ultimate shear load of deep beams although it can not change the brittleness of shear damage. Good agreement are found between test results and simulative results, including failure mode of hybrid fiber reinforced HPC deep beams, load-displacement curves, stress distribution of steel bars and concrete, etc.

Finite Element Analysis of Glass Fiber Reinforced Plastic Hyperbolic Natural Draft Cooling Tower

Applicating the finite element analysis software Ansys to do finite element analysis of a glass fiber reinforced plastic hyperbolic natural draft cooling tower .Under the working condition of gravity and wind load, to contrast the two models of the presence or absence of abdominal rod displacement, stress and unit axial force, and check the stability of compressive bar, and structural optimization. Analysis results can provide reference for the structural design of hyperbolic cooling tower.

일정축력하에 고온을 받는 고강도 콘크리트 충전강관 기둥의 구조적 거동에 관한 연구

Fire-resistant (FR) test data for a square concrete-filled steel tube (CFT) columns consisting of high-strength steel (fy>650MPa) and high strength concrete (fck>100MPa) under axial loads are insufficient. The FR behavior of square high-strength CFT members was investigated experimentally for two specimens having with two axial load cases (5,000kN and 2,500kN). The results show that the FR performance of the high-strength CFT was rapidly decreased at earlier time (much earlier at high axial load) than expected due to high strength concrete spalling and cracks. In addition, a fiber element analysis (FEA) model was proposed and used to simulate the fiber behaviour of the columns. For steel and concrete, the mechanical and thermal properties recommended in EN 1994-1-2 are adopted. Test results were compared to those of numerical analyses considering a combination of temperature and axial compression. The numerical model can reasonably predict the time-axial deformation relationship.

Nonlinear Finite Element Analysis of Steel Fiber Reinforced Concrete Deep Beams With and Without Opening

This paper presents a nonlinear finite element modeling and analysis of steel fiber reinforced concrete (SFRC) deep beams with and without openings in web subjected to two- point loading. In this study, the beams were modeled using ANSYS nonlinear finite element software. The percentage of steel fiber was varied from 0 to 1.0%.The influence of fiber content in the concrete deep beams has been studied by measuring the deflection of the deep beams at mid- span and marking the cracking patterns, compute the failure loads for each deep beam, and also study the shearing and first principal stresses for the deep beams with and without openings and with different steel fiber ratios. The above study indicates that the location of openings and the amount steel fiber are affects to the behavior and strength of deep beams. And also when the results of the experiments taken from the literature were compared with the results obtained from the beam modeled with ANSYS finite element program, it was shown that the results of computer model gave similar results to the experimental behavior.

Prediction of hysteretic behavior of high-strength square concrete-filled steel tubular columns subjected to eccentric loading

This study aimed at predicting the structural behavior of high-strength square CFT (concrete-filled steel tube) columns. First, the material models of the existing steel tube and concrete were compared, and a nonlinear fiber element analysis method was proposed. To verify the proposed fiber element analysis method, the behavior of CFT columns made from high-strength materials was investigated experimentally. CFT members consisted of high-strength steel tubes (yield strength; fy=913MPa) and high-strength concrete (fck=91.3 MPa). The moment-rotation relationships for hollow and concrete-filled steel tubes were compared. In addition, the P-M interaction diagrams for the experiment result and AISC-LRFD code provisions were compared. Finally, the result of the fiber element analyses was compared with the test results.

Eccentric load behavior of L-shaped CFT stub columns with binding bars

This paper is concerned with the eccentric load behavior of L-shaped concrete-filled steel tubular (CFT) stub columns with binding bars. Eight specimens with binding bars and one without binding bars were tested to examine the effects of horizontal spacing and diameter of binding bars, load eccentricity ratio, and load angle on the failure modes, bearing capacity and ductility of L-shaped CFT stub columns. Experimental results demonstrate that the local buckling of the steel tube can be postponed by setting binding bars, and the bearing capacity and curvature ductility of the L-shaped CFT stub columns are at most 1.04 and 3.31 times those without binding bars, respectively, and the plane section assumption can also be satisfied. Based on a modified stress–strain relationship of confined concrete, the fiber element analysis is applied to predict the bearing capacity of the specimens, and the predicted results agree well with the experimental ones. Then the parametric studies using the proposed theoretical model are carried out to further study the fundamental behavior of eccentrically loaded L-shaped CFT stub columns with various steel yield strengths, sectional steel ratios, cube strengths of concrete, confinement coefficients of binding bars, sectional aspect ratios and load angles. Finally, simplified interaction formulas are put forward to predict the Mx/Mx′–My/My′ curves for the L-shaped CFT stub columns with or without binding bars subjected to biaxial eccentric load, and the theoretical results predicted by the simplified formulas agree well with those predicted by the fiber element analysis program.

Local Buckling Analysis of Longitudinal Reinforcing Bars

The local buckling behavior of longitudinal reinforcing steel, which occurs between two transverse hoops, is examined using rational mechanics, taking into account the full plastic behavior of the steel and the effects of true stress and strain. A computational fiber element analysis is used to compute the coupled effect of axial compression and lateral buckling. The results of the computational analysis are then used to develop a simple model for the compressive behavior of longitudinal reinforcing steel in engineering stress-strain coordinates. Although several models exist that are capable of predicting compressive behavior with a moderate degree of precision, these models are generally computationally intensive and therefore of little practical use to structural designers. Other existing simple models either have a high degree of built-in empiricism or are based on overly simplified assumptions about the plastic behavior of the steel. The minimalist model developed in this study is compared with available experimental results. A statistical study shows favorable correlation between the proposed analytical model and experimental results.

Behaviour of Filled Rectangular Steel HSS Composite Columns under Bi-Axial Bending

The purpose of this study was to investigate the behaviour of concrete-filled rectangular steel hollow structural section (HSS) columns formed by slender plates with large depth-to-width ratio subjected to bi-axial bending. As part of this study, four large concrete-filled thin-walled rib-stiffened rectangular HSS columns have been tested. Their steel tubes possess a depth-to-width ratio of 2.38 and a depth-to-thickness ratio of 175. Rib stiffeners were welded to the plate walls such that the stiffened plate width-to-thickness ratio (= 45) was less than that specified (= 60) in the Chinese design code. The results showed that local buckling of steel plate appeared after the specimen reached the ultimate capacity. Also, the fiber element analysis method is adapted to analyze the behaviour of specimen, in which the change of neutral axis position is considered. At last, the experimental results are compared with the values calculated from design codes, namely EC4, LRFD, CECS and DBJ. The results show that all codes provide safe ultimate capacities. Among them, the capacities calculated from DBJ yield results closest to the experimental ones and the other three design codes produce safety over 20%.

A Simple Transversely Isotropic Hyperelastic Constitutive Model Suitable for Finite Element Analysis of Fiber Reinforced Elastomers

A transversely isotropic fiber reinforced elastomer’s hyperelasticity is characterized using a series of constitutive tests (uniaxial tension, uniaxial compression, simple shear, and constrained compression test). A suitable transversely isotropic hyperelastic invariant based strain energy function is proposed and methods for determining the material coefficients are shown. This material model is implemented in a finite element analysis by creating a user subroutine for a commercial finite element code and then used to analyze the material tests. A useful set of constitutive material data for multiple modes of deformation is given. The proposed strain energy function fits the experimental data reasonably well over the strain region of interest. Finite element analysis of the material tests reveals further insight into the materials constitutive nature. The proposed strain energy function is suitable for finite element use by the practicing engineer for small to moderate strains. The necessary material coefficients can be determined from a few simple laboratory tests.

The finite element analysis of square-lattice multi-core photonic crystal fiber

Based on the Helmholtz equations, the full-vector finite element method accompanied by the shifted iteration algorithm was used to analyze in-phase supermode field of square-lattice multi-core photonic crystal fiber. For a five cores photonic crystal fiber, a detailed analysis of the influences of the wavelength, air duty in cladding and diameters of air holes on in-phase supermode field was carried out. The results show that the form of fiber structure plays a key role on mode shape between fiber cores. At last by optimizing diameters of different air holes between fiber cores, the in-phase supermode shapes which have the same amplitude in each core have been obtained for a multi-core photonic crystal fiber.

Calculation of Ductility of Square CFT Stub Columns with Binding Bars Subjected to Eccentric Load

Based on the equivalent uniaxial stress-strain relationship for the encased concrete in the square steel tube with binding bars, the fiber element analysis technique is used to conduct the load versus curvature curves for the square concrete-filled steel tubular (CFT) stub columns with binding bars subjected to eccentric load, and the results predicted by the program agree well with the experimental ones. The fiber element analysis program developed is then used to investigate the effects of varied parameters on the curvature ductility of square CFT stub columns with binding bars subjected to uniaxial or biaxial eccentric load, and the corresponding simplified formulas to predict the curvature ductility of the columns are put forward, respectively. The results predicted by the simplified formulas agree well with those predicted by the program.

High strength circular concrete-filled steel tubular slender beam–columns, Part I: Numerical analysis

High strength circular concrete-filled steel tubular (CFST) slender beam–columns are frequently used in high-rise composite buildings because they possess higher strength and stiffness than normal strength ones. Most nonlinear inelastic methods of analysis for circular CFST slender beam–columns have not considered the effects of high strength materials and concrete confinement that significantly increases the strength and ductility of the concrete core. As a result, these methods produce computational solutions that deviate considerably from experimental results. This paper presents a new numerical model for predicting the nonlinear inelastic behavior of high strength circular CFST slender beam–columns under axial load and bending. The numerical model developed not only accounts for confinement effects on the concrete core and circular steel tubes but also incorporates initial geometric imperfections of beam–columns. Axial load–moment–curvature relationships obtained from the fiber element analysis of column cross-sections are utilized to determine the equilibrium states in the inelastic stability analysis of slender beam–columns. Computational algorithms are developed for determining the axial load–deflection and axial load–moment interaction curves for slender beam–columns. The numerical model is implemented in a computer program, which is shown to be an efficient and accurate simulation tool that can be used to investigate the fundamental behavior of high strength circular CFST slender beam–columns. The verification and applications of the numerical model are given in a companion paper.

Forensic Identification of Trunk Mat by Trace Element Analysis of Single Fiber with Laser Ablation ICP-MS

犯罪捜査で重要な証拠物件となるポリエステル単繊維について，レーザーアブレーション（LA）－誘導結合プラズマ質量分析法（ICP-MS）によって検出された微量不純物を指標とした異同識別法の検討を行った．213 nmのNd : YAGレーザーを搭載したLA装置を最適化し，試料中にppmレベルで存在するCu，Sb，Baなどの微量元素を定量するための測定条件を検討した．自動車製造メーカー7社の23車種から得られたトランクマット単繊維31試料を試料として用いた．直径20 μm程度の単繊維試料について，Li，Mg，Al，P，Ca，Ti，Co，Cu，Ge，Nb，Sb，Pbの定量が可能であった．顕微FT-IRとSEM-EDSを用いる従来法と組み合わせると，31試料すべての識別が可能であった．このようにLA-ICP-MS法は，他のいかなる組成分析法より，試料前処理が迅速で極微小な試料の高感度分析が可能であった．本研究により，本法は自動車のトランクマットの単繊維の実用的な法科学分析法としてきわめて有用であることが初めて実証された．

Fatigue Modeling of Concrete-Filled Fiber-Reinforced Polymer Tubes

Field applications and laboratory research have shown the feasibility of concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) in bridges. Yet, their widespread applications require developing appropriate design and analysis tools for different types of loading, particularly fatigue loads. An analytical tool is developed to trace the response of CFFTs under fatigue loading. The FRP material models are calibrated against fatigue and creep coupon tests. Material models are cast into a fiber element analysis, with an algorithm to simulate strain profile, moment-curvature and residual bending strength at any given time or after any number of fatigue cycles in a single or multiple stages of loading. Comparisons with available test data show good agreement with model predictions. A detailed parametric study shows that fatigue response of CFFT beams can improve by either increasing the reinforcement index or the effective modulus of FRP tube in the longitudinal direction. Higher load ranges may drastically reduce fatigue life. Therefore, it is important to limit the load level on CFFTs for a reliable and predictable member performance. The study also recommends reducing fiber orientation in angle plies with respect to the axis of the beam to improve fatigue performance of the CFFT member.

Analysis of Carbon Fiber Sheet-Retrofitted RC Bridge Columns Under Lateral Cyclic Loading

In recent years, the use of carbon fiber sheet (CFS) to provide lateral confinement for enhanced ductility and strength of reinforced concrete bridge columns has been increasing. While the monotonic behavior of CFS-confined concrete has been studied extensively, its cyclic response has not been fully understood. Most of the available studies are experimental investigations, hence there is a need to develop an analytical model to simulate the experimental results. Analysis of the hysteretic behavior of CFS-retrofitted circular columns is presented in this article using the fiber element that is based on cyclic constitutive models of longitudinal reinforcement and concrete confined by both CFS and tie reinforcement. The analysis was verified based on available cyclic test data and the analysis provides good agreement with the experimental results. Results show that flexural strength and ductility of columns wrapped with CFS increases as CFS ratio increases. However, as tie reinforcement ratio increases, there is no much difference on the hysteretic response for low tie reinforcement ratios. Using the fiber element analysis, the effect of CFS retrofit on the seismic response of a 7.5 m tall prototype pier built in the 1970s to 1980s is also clarified.

주철근 겹침이음 비율에 따른 RC교각의 연성능력 평가

국내외의 실험을 통해 알려진 바와 같이 RC교각의 연성능력은 소성힌지구간에 위치한 주철근 겹침이음 비율 및 횡방향 구속철근이 보유한 횡구속력에 따라 차이를 보이고 있다. 내진설계가 반영되지 못한 기존 교각의 경우 소성힌지구간의 겹침이음 비율에 따라 강도 및 연성능력의 저하에 미치는 영향이 크다. 우리나라에서는1992년 내진설계가 도입된 이후 철근콘크리트 교각의 주철근 겹침 이음에 대한 규정은 없었으나, 2005년 도로교 설계기준에서 주철근 겹침이음을 50% 이내에서 허용하고 있다. 기존 교량의 내진성능 평가 요령에 있어서도 이를 반영하여 교각의 연성능력을 평가하고 있지만 주철근 겹침이음 비율을 단순 유 무에 따라서 구분하여 평가하고 있고 평가기법 또한 명확하게 정립되어 있지 못하다. 따라서 본 연구에서는 비내진 교각의 겹침이음 비율별 연성능력평가를 위하여 현재까지 국내에서 수행된 연구실험결과를 분석하고, 교각의 비선형성 및 주철근의 겹침이음을 고려하기 위하여 섬유요소를 이용한 단면해석으로 RC교각의 연성능력을 산정시 적절한 콘크리트의 극한변형률을 제시하였다. As internal and external seismic experiment results, the seismic performance of RC bridge piers is largely dependent on the ratio of lap-spliced bars to all longitudinal reinforcing bars in plastic hinge regions, and confining effects of transverse reinforcements. Capacity and displacement ductility of non-seismically designed existing RC piers are reduced by lap splices in plastic hinge regions. The provision for the lap splice of longitudinal reinforcing bars was not specified in KBDS (Korean Bridge Design Specifications) before the implementation of 1992 seismic design code, but the ratio of lap-spliced bars to all longitudinal reinforcing bars in plastic hinge regions is restricted to 50% in the 2005 version of KBDS. This paper presents a seismic assessment of RC piers at lap-splicing ratios of 0%, 50%, and 100%. Through a comparison of experimental and analytic results of RC piers, we introduce an appropriate ultimate strain of confined concrete in plastic hinge regions with lap-splices, and propose a method for estimating displacement ductility ratios of non-seismically designed existing RC piers using fiber element analysis.

Nonlinear finite element analysis of steel fiber reinforced concrete deep beams

By the nonlinear finite element analysis (FEA) method, the mechanical properties of the steel fiber reinforced concrete (SFRC) deep beams were discussed in terms of the crack load and ultimate bearing capacity. In the simulation process, the ANSYS parametric design language (APDL) was used to set up the finite element model; the model of bond stress-slip relationship between steel bar and concrete was established. The nonlinear FEA results and test results demonstrated that the steel fiber can not only significantly improve the cracking load and ultimate bearing capacity of the concrete but also repress the development of the cracks. Meanwhile, good agreement was found between the experimental data and FEA results, if the unit type, the parameter model and the failure criterion are selected reasonably.

Nonlinear Finite Element Analysis of High Strength Fiber Reinforced Concrete Corbels

Nonlinear Finite Element Analysis of High Strength Fiber Reinforced Concrete Corbels

Nonlinear analysis of short concrete-filled steel tubular beam–columns under axial load and biaxial bending

This paper presents a nonlinear fiber element analysis method for determining the axial load–moment strength interaction diagrams for short concrete-filled steel tubular (CFST) beam–columns under axial load and biaxial bending. Nonlinear constitutive models for confined concrete and structural steel are considered in the fiber element analysis. Efficient secant algorithms are developed to iterate the depth and orientation of the neutral axis in a composite section to satisfy equilibrium conditions. The accuracy of the fiber element analysis program is verified by comparisons of fiber analysis results with experimental data and existing solutions. The fiber element analysis program developed is employed to study the effects of steel ratios, concrete compressive strengths and steel yield strengths on axial load–moment interaction diagrams and the C -ratio of CFST beam–columns. The proposed fiber element analysis technique is shown to be efficient and accurate and can be used directly in the design of CFST beam–columns and implemented in advanced analysis programs for the nonlinear analysis of composite columns and frames.

Delamination of laminated fiber reinforced plastic composites under multiple cylindrical impact

In the present paper a 3D finite element analysis has been performed for assessing delamination at the interfaces of graphite/epoxy laminated fiber reinforced plastic composites subjected to low velocity impact of multiple cylindrical impactors. Eight nodded layered solid elements have been used for the finite element analysis of fiber reinforced plastic laminates. Newmark-β method along with Hertzian contact law has been used for transient dynamic finite element analysis and an algorithm has been developed for determining the response of the laminated plate under the multiple impacts at different time. Appropriate delamination criterion has been used to assess the location and extent of delamination due to multiple impacts. A study has been carried out to observe the effects of important parameters on the impact response of the laminate and the delamination induced at the interfaces. It has been observed that the contact force magnitude as well as delamination at the interface are greatly influenced by the time interval between successive multiple impacts.