3D FE modelling of composite box Girder Bridge

The complexity nature of composite box girder bridges makes it difficult to accurately predict their structural response under loading. However, that difficulty in the analysis and design of composite box girder bridges can be handled by the use of the digital computers in the design. An intricate geometry such as that of composite box girder bridges can be facilely modelled using the FE technique. The method is also capable of dealing with different material properties, relationships between structural components, boundary conditions, as well as statically or dynamically applied loads. The linear and nonlinear structural response of such bridges can be predicted with good accuracy using this method. A major interest in this paper is to perform three-dimensional FE analyses of composite box girder bridge to simulate the actual bridge behaviour. ANSYS FE package is used to develop the models which offer different element types and physical contact conditions between concrete deck and steel girder. Predictions of several FE models are assessed against the results acquired from a field test. Several factors are considered, and confirmed through experiments especially full shear connections which are obviously essential in composite box girder. Numerical predictions of both vertical displacements and normal stresses at critical sections fit fairly well with those evaluated experimentally. The agreement between the FE models and the experimental models show that the FE model can aid engineers in design practices of box girder bridges

Virtual testing against experiment for post-buckling behaviour of coldformed steel columns

Cold-formed steel has already started to replace hot rolled companions in some structural applications. Advantages of cold-formed steel originate from its high strength over weight ratio and ease of manufacturing and construction compared to hot rolled heavy sections. Moreover, cold-formed columns have significant post-buckling reserve which has the potential to be exploited in design process. Therefore, it is essential to predict the response of cold-formed columns by means of high fidelity engineering techniques. Herein an in depth study which links experimental testing and non-linear computational capabilities is undertaken to address the failure behaviour of cold-formed columns. Experimental program comprises coupon tests to specify material properties and compression testing of fixed end cold-formed columns. Thereafter, measured material properties are utilized to generate a stress-strain curve for finite element models. Boundary conditions imposed into simulation models in such a way that would represent test conditions. Creating a suitable mesh for different cross sectional dimensions, different shapes of initial imperfections are introduced into models to compare contributions to performance of columns. Predicted collapse loads and modes via finite element models are assessed against test results. Mesh and initial imperfection sensitivities on failure characteristics are discussed. Finally a general assessment is made for the deployed testing and simulation to generate knowledge for the design evaluation of cold-formed steel columns. Key findings and discussions of present study have the potential to lead to develop promising cold-formed steel column virtual test models

Tailoring Compression Performance of Cold-Formed Steel Columns

Since thin-walled structural analysis and design procedures are utilized for cold-formed steel columns, it is first necessary to understand thin plate behavior to employ proper cross sections which will serve under compression actions. As is well known, thin plates without any longitudinally and/or laterally stiffening elements usually are not present in structural applications. These stiffening elements significantly improve local buckling and collapse characteristics of plates, providing optimized solutions in terms of strength and cost. In cold-formed steel industry there exist some tailoring methods for columns to use the cross-section material more effectively. Designing lipped channels instead of plain ones or deploying rack sections can be shown as examples of stiffening and enhancing flange compression performance. Present study offers a novel tailoring technique which has the potential to improve collapse performance of cold-formed steel columns. Considering the manner of stiffening for thin plates, present work assesses cold-formed steel columns which are manufactured using stiffened sheets. Used stiffened sheets are called as checkered sheets which contain small stiffeners on thin plates in a shape of diamond pattern and are generally used to cover stairs and decks in outdoor environments to prevent slip. Aiming at investigating contributions of small stiffeners on compression performance of cold-formed steel columns, an experimental study was undertaken and column specimens were tested to failure. Plain channel test specimens were manufactured using press braking method and boundary conditions of specimens were designed in such a way that would represent fixed ends. Accompanying the experimental program, non-linear finite element simulation works and AISI-2007 method were employed for manufactured columns using equivalent thickness approach. Results imply that with the proper geometrical configurations, reserve of cold-formed steel columns manufactured using checkered sheets offer structural efficiency in satisfying greater compression loadings compared to that of columns manufactured using plain sheets of equivalent thickness. This stiffened sheets concept has the potential to be facilitated in cold-formed steel commercial and residential structures. More efficient sections also can be acquired for design purposes by optimizing those stiffener configurations under compression loadings

LRFD and Eurocode-3 Specifications for Ultimate Load Carrying Capacity Evaluation of Steel Columns and Effects of Imperfections

In this study main attention is focused on axial load carrying capacity of steel columns. Towards this aim, employing nonlinear geometric and material properties Finite Element models are generated using ANSYS program. In simulations due to its advantages Arc-Length method is utilized for determination of axial load capacity of columns. Computational study consists of four phases. In the first one nonlinear bucking loads of IPE 200 section are evaluated for different slenderness ratios (L/ry). Obtained results for different slenderness ratios are assessed against LRFD and Eurocode-3 specifications. In the second section geometrical imperfections are incorporated into column models in a systematic manner and capacity changes are evaluated. Effects of eccentric compression loadings on the axial load carrying capacity are studied in third section. Fourth section introduces the effects of combined geometrical imperfections and eccentric loadings

Flexural Performance of PVA Reinforced ECC Beams: Numerical and Parametric Studies

Engineered cementitious composite (ECC) refers to the group of cementitious mixtures possessing the strainhardening and crack control abilities. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of aggregate size and amount, by employing nonlinear finite element method. The validity of the models were verified with the experimental results of the ECC beams under monotonic loading. Based on the numerical analysis method,nonlinear parametric study was then conducted to evaluate the influences of various parameters on the flexural stress and flexural deflection of ECC beams. A new models that accounts for the ECC aggregate content (AC), ECC compressive strength (fECC), and maximum aggregate size (Dmax) parameters are proposed. The analytical results obtained from the proposed models were compared with experimental results obtained from 57 ECC beam tests previously published. The simulation results indicated that when increase the aggregate size and content no definite trend in flexural strength is observed and the ductility of ECC is negatively influenced by the increase of aggregate size and content. Also, the ECC beams revealed enhancement in terms of flexural stress, strain, and midspan deflection when compared with the reference beam (microsilica MSC), where, the average improvement percentage of the specimens were 45%, 1242%, and 1427.15%,respectively. These results are quite similar to that of the experimental results, which provides that the finite element model is in accordance with the desirable flexural behaviour of the ECC beams. Furthermore, the proposed models can be used to predict the flexural behaviour of ECC beams with great accuracy

Flexural behavior of concrete beams reinforced with different types of fibers

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams