Influence of boundary conditions and geometric imperfections on lateral–torsional buckling resistance of a pultruded FRP I-beam by FEA

Presented are results from geometric non-linear finite element analyses to examine the lateral torsional buckling (LTB) resistance of a Pultruded fibre reinforced polymer (FRP) I-beam when initial geometric imperfections associated with the LTB mode shape are introduced. A data reduction method is proposed to define the limiting buckling load and the method is used to present strength results for a range of beam slendernesses and geometric imperfections. Prior to reporting on these non-linear analyses, Eigenvalue FE analyses are used to establish the influence on resistance of changing load height or displacement boundary conditions. By comparing predictions for the beam with either FRP or steel elastic constants it is found that the former has a relatively larger effect on buckling strength with changes in load height and end warping fixity. The developed finite element modelling methodology will enable parametric studies to be performed for the development of closed form formulae that will be reliable for the design of FRP beams against LTB failure

Online measurement of optical fibre geometry during manufacturing

Online measurement of diameters and concentricities of optical fibre layers, and the coating layer in particular, is one of the challenges in fibre manufacturing. Currently available instruments can measure concentricity and diameter of layers offline, and are not suitable for precise monitoring or control of the manufacturing process in real time. In this work, we use two laser beams, positioned orthogonally to illuminate the fibre from two sides, and calculate deviations from the expected geometry by analysing the scattering pattern. To measure the diffraction pattern we use two 8K linear array detectors, with the scattered light incident directly on the sensors. Each detector is capturing approximately 90 degree angular range directly behind the fibre. The two measurement channels are positioned at different heights. The scattered pattern is modelled mathematically with finite-element and Fourier-modal methods, with various diameter and concentricity deviations. The sensitivities of the changes in the scattering pattern are identified in respect to these deviations. Since calculations are computationally intensive, the sensitivities are pre-calculated in advance, and the real-time measurement is based on pattern recognition. The symmetry of the pattern is used to differentiate between diameter and concentricity variations. We performed online measurements with the prototype instrument in production conditions, and show that this method is sensitive enough to measure deviations of under 1 {\mu}m in diameter and concentricity of the coating layer.Comment: Proceedings article, SPIE conference "Fiber Lasers and Glass Photonics: Materials through Applications

Stresses In The End Zones Of Precast Inverted T-Beams With Tapered Webs

Short to medium span composite bridges constructed with adjacent precast inverted T-beams and cast-in-place topping are intended to provide more resiliency against reflective cracking and time dependent effects compared to voided slabs and adjacent box girder systems. This thesis investigates the stresses in the end zones of such a uniquely shaped precast element. The transfer of prestressing force creates vertical and horizontal tensile stresses in the end zones of the girder. A series of 3-D finite element analyses were performed to investigate the magnitude of these tensile stresses. Hoyer effect is captured by modelling the strands as solid elements and defining the interaction between strands and concrete in the tangential and normal behavior using friction coefficient and hard contact, respectively. The modelling protocol captures spalling, splitting, and bursting stresses. It was found that, stresses in the end zones of precast inverted T-beams with tapered webs are not likely to cause any significant cracking if the beam is reinforced based on AASHTO’s provisions for pretensioned anchorage zones. Various modeling techniques were evaluated, and it was found that linear elastic models with truss elements are adequate for design purposes in terms of mapping where the end zone reinforcing needs to be located. However, if such modeling capabilities are not available AASHTO’s provisions suffice in terms of reinforcing the critical areas in the end zones

Amalan keselamatan bengkel dalam kalangan pelajar Kolej Vokasional Temerloh

Amalan keselamatan merupakan perkara penting yang perlu ditekankan semasa melakukan kerja amali di bengkel. Oleh itu, penekanan terhadapnya perlu dipupuk kepada setiap pelajar supaya menjadi budaya ketika berada di bengkel. Sehubungan itu, kajian ini adalah untuk mengenalpasti tahap pengetahuan, tahap kesedaran dan tahap penerimaan amalan keselamatan dalam kalangan pelajar. Kajian ini juga mengenalpasti perhubungan di antara tahap kesedaran dan tahap penerimaan pelajar terhadap amalan keselamatan yang dikaji. Lokasi kajian ini ialah Kolej Vokasional Temerloh (KVT), Pahang. Responden seramai 296 orang merupakan pelajar daripada enam program utama di KVT yang menggunakan bengkel iaitu Teknologi Automotif, Teknologi Penyejukbekuan & Penyamanan Udara, Teknologi Kimpalan, Teknologi Binaan, Teknologi Elektrik dan Teknologi Elektronik. Instrumen kajian kajian yang digunakan adalah borang soal selidik. Sebanyak 45 item soalan telah dibina untuk menjawab setiap persoalan kajian. Data dianalisis secara kaedah Purata Indeks dan Analisis Ujian Spearman’s rho yang menggunakan perisian “Statistical Package for the Social Science (SPSS)” Versi 18. Dapatan kajian menunjukkan nilai purata min bagi tahap pengetahuan (4.66), tahap kesedaran (4.54) dan tahap penerimaan (4.51) pelajar terhadap perlaksanaan amalan keselamatan bengkel adalah tinggi. Kajian ini juga mendapati wujudnya perhubungan secara statistik di antara tahap kesedaran dan tahap penerimaan amalan keselamatan bengkel. Pengkaji juga mencadangkan supaya kajian ini dapat dilakukan di institusi kemahiran yang lain agar dapat digeneralisasikan dapatannya. Kesimpulan yang diperolehi daripada kajian ini didapati tahap amalan keselamatan dalam kalangan pelajar KVT adalah pada tahap yang tinggi

Finite Element Analysis on Reinforced Concrete Columns Strengthened by ECC Jacketing under Eccentric Compressive Load

Engineered cementitious composite (ECC) can be used for strengthening of concrete columns due to its similar structure and suitable connection to normal concrete and its special tension behavior. In this study, to analyse the columns, finite element (FE) method was used after verification by experimental results. Reference column was strengthened by normal concrete and ECC jacketing. The effects of type of jacket material, longitudinal reinforcement, compressive stress and ultimate tensile strain of ECC on variations of eccentric load-bending moment (P-M) interaction curves were investigated. Results showed that the use of ECC instead of normal concrete can increase load carrying capacity of strengthened column, due to tensile strain hardening behavior of this material. It was found that, amount of this increase depends on eccentricity of eccentric load and varying from 0.4-23%. In ECC jacketing, tensile cracks are continuous, but in concrete jacketing, there were discrete cracks and more quantity of damages. Due to higher load carrying capacity and better distribution of tensile cracks in ECC jacketing than normal concrete jacketing, the use of ECC is suitable for strengthening of reinforced concrete columns. Load carrying capacity of columns under concentric load and pure bending moment were calculated by theoretical method and the results were compared with FE

Behaviour and design of composite beams subjected to negative bending and compression

This paper investigates the behaviour of steel–concrete composite beams subjected to the combined effects of negative bending and axial compression. Six full-scale tests were conducted on composite beams subjected to negative moment while compression was applied simultaneously. Following the tests, a nonlinear finite element model was developed and calibrated against the experimental results. The model was found to be capable of predicting the nonlinear response and the ultimate failure modes of the tested beams. The developed finite element model was further used to carry out a series of parametric analyses on a range of composite sections commonly used in practice. It was found that, when a compressive load acts in the composite section, the negative moment capacity of a composite beam is significantly reduced and local buckling in the steel beam is more pronounced, compromising the ductility of the section. Rigid plastic analysis based on sectional equilibrium can reasonably predict the combined strength of a composite section and, thus, can be used conservatively in the design practice. Based on the experimental outcomes and the finite element analyses a simplified design model is proposed for use in engineering practice

The flexibility matrix o timber composite beams with a discrete connection system

This work presents a method for the analysis of timber composite beams which considers the slip in the connection system, based on assembling the flexibility matrix of the whole structure. This method is based on one proposed by Tommola and Jutila (2001). This paper extends the method to the case of a gap between two pieces with an arbitrary location at the first connector, which notably broadens its practical application. The addition of the gap makes it possible to model a cracked zone in concrete topping, as well as the case in which forming produces the gap. The consideration of induced stresses due to changes in temperature and moisture content is also described, while the concept of equivalent eccentricity is generalized. This method has important advantages in connection with the current European Standard EN 1995-1-1: 2004, as it is able to deal with any type of load, variable section, discrete and non-regular connection systems, a gap between the two pieces, and variations in temperature and moisture content. Although it could be applied to any structural system, it is specially suited for the case of simple supported and continuous beams. Working examples are presented at the end, showing that the arrangement of the connection notably modifies shear force distribution. A first interpretation of the results is made on the basis of the strut and tie theory. The examples prove that the use of EC-5 is unsafe when, as a rule of thumb, the strut or compression field between the support and the first connector is at an angle with the axis of the beam of less than 60º

The use of continuum models for analyzing adobe structures

As it is known, the adobe structures have a high seismic vulnerability principally due to the low material strength and sometimes due to the inadequate structural configuration. One way for understanding the seismic behaviour of these structures is by experimental tests. However, those are costly and sometimes not easy to make. An alternative for this is the analysis of adobe structures by numerical tools with the possibility to make parametric studies for understanding the behaviour of different geometrical configurations. In a previous work, some adobe material parameters have been calibrated based on a cyclic in-plane test. In this paper, that work was extended to a numerical modelling of the non-linear dynamic behaviour of an adobe module experimentally tested at the Pontificia Universidad Católica del Perú. For this, a continuum model in the finite element program Abaqus/Explicit, was used to represent the adobe masonry as a homogeneous and isotropic material