Optimisation of Novel Elliptically-Based Web Opening Shapes of Perforated Steel Beams

A new study was carried out and presented herein, on the optimisation of novel elliptically-based web opening shapes which enhance the structural behaviour of the perforated beams as well as lead to economic design in terms of both manufacture and usage. The finite element (FE) model used in the study was validated against experimental work conducted by the authors and the results of the comprehensive study are presented in this research paper. For ease of comparison, the yield patterns and deflected shapes of the perforated beams are presented at three characteristic load level points. Finally, shear-moment interaction FEM curves are presented for six different web opening shapes to allow for easy use of the empirical design formulas that have previously been proposed by the authors in a complementary research paper. An overall study of many standard and non-standard web opening shapes, it was shown that perforated beams with vertical and inclined classic elliptical web openings (3:4 width to depth ratio) behave more effectively compared to perforated beams with conventional circular and hexagonal web openings, mainly in terms of stress distribution and local deflection. Therefore, perforated steel beams with large novel elliptically-based web openings with short critical opening length at the top and bottom tee-section as well as straight-line edges are presented for first time and examined in the current research programme

A FE parametric study of RWS beam-to-column bolted connections with cellular beams

In recent years, researchers study alternative connection designs for steel seismic-resistant frames by reducing the beam section in different ways including that of creating an opening in its web (RWS connections). A similar design is applied in the fabrication of perforated (i.e. cellular and castellated) beams mostly used to support the service integration, as well as the significant mass reduction in steel frames. This paper presents a comprehensive finite element (FE) analysis of extended end-plate beam-to-column connections, with both single and multiple circular web openings introduced along the length of the beam while subjected to the cyclic loading proposed by the SAC protocol from FEMA 350 (2000). The three-dimensional (3D) FE solid model was validated against FE and experimental results and the chosen configuration was capable of representing the structural behaviour of a partially restrained connection, without the necessity to be idealised as fully fixed. The study focuses in the interaction of such connections and the mobilisation of stresses from the column to the perforated beam. The parameters introduced were the distance from the face of the column, S, and the web opening spacing, So, with closely and widely spaced web openings. It is found that RWS connections with cellular beams behave in a satisfactory manner and provide enhanced performance in terms of the stress distribution when subjected to cyclic loading. The design of partially restrained RWS connections should be primarily based on the distance of the first opening from the face of the column

Deterioration of Basic Properties of the Materials in FRP-Strengthening RC Structures under Ultraviolet Exposure

This paper presents an experimental study of the basic properties of the main materials found in reinforced concrete (RC) structures strengthened by fibre reinforced polymer (FRP) sheets with scope to investigate the effect of ultraviolet (UV) exposure on the degradation of FRP, resin adhesive materials and concrete. The comparison studies focused on the physical change and mechanical properties of FRP sheet, and resin adhesive materials and concrete before and after UV exposure. However, the degradation mechanisms of the materials under UV exposure were not analyzed. The results show that the ultimate tensile strength and modulus of FRP sheets decrease with UV exposure time and the main degradation of FRP-strengthened RC structures is dependent on the degradation of resin adhesive materials. The increase in the number of FRP layers cannot help to reduce the effect of UV exposure on the performance of these materials. However, it was verified that carbon FRP materials have a relatively stable strength and elastic modulus, and the improvement of the compression strength of concrete was also observed after UV exposure

Behaviour of Circular Fiber-Reinforced Polymer-Steel-Confined Concrete Columns Subjected to Reversed Cyclic Loads: Experimental Studies and FE Analysis

This paper studies experimentally the behaviour of circular FRP-steel-confined columns subjected to reversed cyclic loads. The influence of main structural factors on the cyclic behaviour of the columns is discussed. Test results show the outstanding seismic performance of FRP-steel confined reinforced concrete (RC) and steel-reinforced concrete (SRC) column. The lateral confinement effectiveness of FRP materials is verified in the steel tube confined RC columns. A simplified finite element method (FEM) model supported by OpenSees is developed to simulate the experimental results of the test columns. Based on the proposed FEM model, a parametric analysis is conducted for investigating the effects of several main factors on the reversed cyclic behaviour of GFRP-steel confined RC columns. Based on the test and numerical analyses, the study discusses the influence of variables such as the lateral confinement on the plastic hinge region and peak drift ratio of the studied concrete columns under reversed cyclic loads. Results indicate that the lateral confinement significantly affects the height of plastic hinge region of circular confined columns without H-steel. Based on the analysies of test data from the study and literature, the paper suggests a simple model to predict the peak drift ratio of the confined RC columns

Elastic and inelastic buckling of steel cellular beams under strong-axis bending

This paper presents an extensive parametric study of elastic and inelastic buckling of cellular beams subjected to strong axis bending in order to investigate the effect of a variety of geometric parameters, and further generate mass data to validate and train a neural network-based formula. Python was employed to automate mass finite element (FE) analyses and reliably examine the influence of the parameters. Overall, 102,060 FE analyses were performed. The effects of the initial geometric imperfection, material nonlinearity, manufacture-introduced residual stresses, web opening diameter, web-post width, web height, flange width, web and flange thickness, end web-post width, and span of the beams and their combinations were thoroughly examined. The results are also compared with the current state-of-the-art design guidelines used in the UK. It was concluded that the critical elastic buckling load of perforated beams corresponds to the lateral movement of the compression flange while the most critical parameters are the web thickness and the geometry of the flange. However, from the inelastic analysis, the geometry and position of the web opening influence the collapse load capacity in a similar fashion to the geometry of the flange and thickness of the web. It was also concluded that the effect of the initial conditions was insignificant

Application of structural topology optimisation in aluminium cross-sectional design

Aluminium is lightweight and corrosion-resistant; however, its low Young's Modulus predisposes the need for better material distribution across its section to increase stiffness. This paper studies a holistic design optimisation approach with the power of structural topology optimisation aiming to develop novel structural aluminium beam and column profiles. The optimisation methodology includes forty standard loading combinations while the optimisation results were combined through an X-ray overlay technique. This design optimisation approach is referred here to as the Sectional Optimisation Method (SOM). SOM is supported by engineering intuition as well as the collaboration of 2D and 3D approaches with a focus on post-processing and manufacturability through a morphogenesis process. Ten optimised cross-sectional profiles for beams and columns are presented. The shape of one of the best performing optimised sections was simplified by providing cross-section elements with a uniform thickness and using curved elements of constant radius. A second level heuristic shape optimisation was done by creating new section shapes based on the original optimised design. The paper also carries out stub column tests using finite element analysis (FEA) to determine the loacl buckling behaviour of the above-optimised aluminium profiles under compression and to investigate the effectiveness of using the existing classification methods according to codified provisions of Eurocode 9. The herein presented work aims to integrate topology optimisation aspects in cross-sectional design of aluminium alloy element building applications, providing thus a new concept in design procedures of lightweight aluminium structures

Assessment of perforated steel beam-to-column connections subjected to cyclic loading

This paper presents a study of welded perforated beam-to-column connections, forming the so-called RWS systems. The effect of using non-standard novel web opening configurations of variable depths and positions is investigated. The ease of manufacturing process together with the improvements on the structural behaviour foreshadows the enhancements gained using these perforated members. It is concluded that using large perforations is an effective way of improving the behaviour of connections enhancing their ductility and their energy dissipation capacity. The connections with novel openings outperform the conventional ones; hence they can be suitably used in the aseismic design of steel frames

Application of structural topology optimisation to perforated steel beams

This paper focuses on the application of structural topology optimisation technique to design steel perforated I-sections as a first attempt to replace the traditional cellular beams and better understand the mechanisms involved when subjected to bending and shear actions. An optimum web opening configuration is suggested based on the results of parametric studies. A FE analysis is further employed to determine the performance of the optimised beam in comparison to the conventional widely used cellular type beam. It is found that the optimised beam overperforms in terms of load carrying capacities, deformations, and stress intensities. Barriers to the implementation of the topology optimisation technique to the routine design of beam web are highlighted

Experimental and computational study of the vertial shear behaviour of partially encased perforated steel beams

A comprehensive study has been undertaken by the authors to conduct advanced analysis and enable design tools for innovative Ultra Shallow Floor Beams (USFB) in buildings. In the USFB, the concrete slab lies within the steel flanges and is connected to the slab through the web opening, providing enhanced longitudinal and vertical shear resistance. There are additional benefits in providing increased fire and buckling resistance to the steel beam. In this study four specimens of symmetric steel-concrete composite beams with large circular web openings in the steel section and low concrete grade were tested under static monotonic loading. One of the specimens was from a lower quality of concrete and was tested in order to further investigate the failure mechanism and the actual behaviour of the concrete confinement. The load carrying capacity of the perforated bare steel beam is also presented for direct comparison. For the computational approach to the problem, a three-dimensional (3D) Finite Element (FE) model was created, employing solid elements with material, geometrical and interfacial non-linearity. Two-dimensional (2D) FE contact models using shell elements were established to examine the steel-concrete interface condition. The results show that the FE models are able to satisfactorily predict the load carrying capacities and the crack patterns of these new composite beams against the Vierendeel failure mechanism. A sensitivity study of material models and contact strengths using various constitutive models from the literature and the dominant parameters which affect the structural behaviour of the USFBs, are presented and discussed. Furthermore, the FE models provide detailed information on the structural behaviour of the confined concrete between the flanges and the section of concrete that passes through the web openings, as this is of paramount importance for the load carrying capacity and the failure mode of the USFBs. The comparison between the experimental and computational results leads to useful conclusions. The results for the composite beams show a significant increase in vertical shear resistance, even though mechanical shear connectors were not used. A previous design method is presented and modified to be able to be used for the load carrying capacity prediction of this new composite structural system. The results compare very well and the shear enhancement demonstrated in this study is now used in design practice

Investigation into the mechanical properties of structural lightweight concrete reinforced with waste steel wires

The study of concrete incorporating different waste fibres has started to increase rapidly due to economic reasons and positive environmental effects. In the study reported here, waste steel wires from steel reinforcement and used formworks were blended with structural lightweight concrete, with the aim of replacing commercial steel fibres of controlled quality with recycled fibres. Compression, tensile, flexural and impact tests were performed to assess the mechanical properties of 28 d old concrete specimens reinforced with mixed waste steel wires, mixed steel fibres as well as plain concrete. The percentages of fibres examined in the fibre reinforced concrete (FRC) specimens were 0·25%, 0·50% and 0·75% (volume fraction of the concrete). With varying fibre contents, similar trends were observed in all the types of FRCs studied. It was thus concluded that waste steel wires could be used as a suitable alternative to industrial steel fibres for structural lightweight concrete applications