Finite Element Investigation on Web-Post Buckling of Perforated Steel Beams with Various Web Opening Shapes subjected under different shear-moment interaction

The current method of assessment is based on FE models which still lack computational efficiency and are restricted by a number of limitations. Therefore, this work aims at the feasibility of developing FE models which are applicable to deformation and strength prediction of full scale perforated steel beams. The main area of interest is the stability of the web-post under the combined effect of shear and compression, especially at the edge of the web openings, where the stabilizing effect of tension field action is less than that at the centre of the web-post

Experimental Study of Ultra Shallow Floor Beams (USFB) with Perforated Steel Sections

ABSTRACT: In modern building construction design, floor spans are becoming longer. Hence, steel framed structures have become more competitive when compared with traditional reinforced concrete framed buildings. In order to minimise the structural section of the composite sections, and for economic reasons, steel perforated beams are designed to act compositely with the floor slab. When the concrete slab lies within the steel flanges, as in the Ultra Shallow Floor Beam (USFB), there is an additional benefit when considering fire resistance. The aim of this study is to investigate the contribution of the concrete in composite cellular beams in the case where the concrete slab lies between the beam flanges of a steel section, when resisting vertical shear forces. The concrete between the flanges enhances the load-carrying capacity by providing a load path to transfer the shear force. Four specimens of steel-concrete composite beams with web openings in the steel section were tested in this study. One bare steel section with web openings was also tested as a comparison. This is the first such investigation of the failure mode under shear resistance (Vierendeel action) of the Ultra Shallow Floor Beam. In the test specimens, the web opening diameter is 76% of the beam depth, which is the largest currently available. This represents the worst case in terms of Vierendeel bending forces generated in the vicinity of the web openings. The smaller the hole is, the easier it is for the trapped concrete between the flanges to transfer shear across the opening. The results from the composite beam tests show a significant increase in shear resistance. The percentage of the shear capacity improvement of the particular case is presented herein as well as the failure mode of the composite beams. The shear enhancement demonstrated in this study has been utilised software that is used in design practice

FE Investigation of Perforated Sections with Standard and Non-Standard Web Opening Configurations and Sizes

The objective of this work is to investigate and compare, through an analytical study, the behaviour of perforated steel beams with different shape configurations and sizes of web openings. In this investigation the ‘Vierendeel’ failure mechanisms of steel beams with web openings are examined through a Finite Element study. The shear and flexural failures of standard perforated sections are controlled mainly by the size (i.e. depth) of the web openings, whilst the ‘Vierendeel’ mechanism is primarily controlled by the critical length of the web openings. Three main categories of web opening shape configurations and sizes are considered in this work. Standard, non-standard and elongated web opening configurations are examined, each with three different opening sizes. Four Advanced UB beams are used in the investigation in order to cover a range of sections and demonstrate the main differences in behaviour. The results of this comprehensive FE study are presented and include the position of plastic hinges, the critical opening length of perforated steel sections and the ‘Vierendeel’ parameters. The yield patterns and the failure modes do not differ dramatically. The results of this study are considered as relevant for practical applications as: (i) the reduction of the moment capacities of the tee-sections due to combination of axial and shear forces is smaller compared to the previous conservative linear interaction formula, and (ii) the formation of the initial plastic hinges at the low moment side (LMS) of the top tee-sections of the web openings does not usually cause failure, meaning that the beams can continue to carry additional load until all four plastic hinges are formed in the vicinity of the web openings and a ‘Vierendeel’ mechanism is fully established

Applications of topology optimisation in structural engineering: high-rise buildings & steel components

This study introduces applications of structural topology optimization to buildings and civil engineering structures. Topology optimization problems utilize the firmest mathematical basis, to account for improved weight-to-stiffness ratio and perceived aesthetic appeal of specific structural forms, enabling the solid isotropic material with penalization (SIMP) technique. Structural topology optimization is a technique for finding the optimum number, location and shape of “openings” within a given continuum subject to a series of loads and boundary conditions. Aerospace and automotive engineers routinely employ topology optimization and have reported significant structural performance gains as a result. Recently, designers of buildings and structures have also started investigating the use of topology optimization, for the design of efficient and aesthetically pleasing developments. This paper examines two examples of where topology optimization may be a useful design tool in civil/structural engineering in order to overcome the frontiers between civil engineers and engineers from other disciplines. The first example presents the optimized structural design of a geometrically complex high-rise structure and the optimal design of its architectural building shape. The second one focuses on the optimization and design of a perforated steel I-section beam, since such structural members are widely used nowadays in the vast majority of steel buildings and structures while they provide numerous advances. Conclusions are drawn regarding the potential benefits to the more widespread implementation of topology optimization within the civil/structural engineering industr

Derivation of dynamic properties of steel perforated Ultra Shallow Floor Beams (USFBTD) via Finite Element modal analysis and experimental verification

In recent years, the incorporation of asymmetric perforated ultra shallow floor beams (USFBs) constructed from advanced UB and UC profile beams in various composite floor systems has been extensively considered in practice. To date, limited research effort has been devoted to the detailed investigation of the dynamic properties of USFBs. In this paper, modal analyses of detailed FE models of various USFBs commonly used in composite floor systems developed in ANSYS are conducted to extract their dynamical properties (i.e. natural frequencies and mode shapes). Furthermore, experimental data pertaining to the standard impact test is also considered to validate the accuracy of the aforementioned FE results. In particular, a six meter long USFB beam is subject to impulsive excitation by means of an appropriately instrumented hammer. The dynamic properties obtained by processing the recorded response signals compare well vis-a-vis the corresponding results from the FE modal analysis. Finally, effective properties of USFBs which can be readily used in the definition of beam elements of constant cross-section along their longitudinal direction are derived. This constitutes an important step to facilitate the analysis and design of USFBs against dynamic loads at the serviceability limit state using standard commercial structural analysis software

Experimental study and analytical study of push-out shear tests in Ultra Shallow Floor Beams

The Ultra Shallow Floor Beam is a new type of composite floor beam fabricated by welding two highly asymmetric cellular tees together along the web and incorporating a concrete slab between the top and bottom flanges. The unique features of this system are circular and elongated web openings that allow tie-bars, building services and ducts passing through the structural depth of the beam. For the composite beam in bending, the longitudinal shear force is transferred by a unique shear mechanism which results from the special configuration of the beam, and shear connectors, if they are present. The work reported in this paper includes a total of 16 full-scale push-out tests aimed at investigating the longitudinal shear behaviour of these beams and the effects of additional shear connectors. A theoretical analysis was also performed to investigate the failure mechanism of the system

Shear Capacity of Perforated Concrete-Steel Ultra Shallow Floor Beams (USFB)

ABSTRACT : In modern building construction floor spans are becoming longer and one way of achieving this is to use composite beams. In order to minimize the structural depth of the composite sections, and to produce lighter members for economy reasons, steel perforated beams are designed to act compositely with the floor slab in an Ultra Shallow Floor Beam (USFB). In the USFB the concrete slab lies within the steel flanges and is connected through the web opening, providing enhanced longitudinal and vertical shear resistance. There is an additional benefit in increased fire resistance. The aim of this project is to investigate, through finite element simulations and suitable tests, the contribution of concrete in composite cellular beams in resisting vertical shear when the concrete slab lies between the flanges of the steel section. The concrete between the flanges provides the load path to transfer the shear force. For the computational approach to the problem, a three-dimensional Finite Element (FE) model was created, in which contact elements were implemented at the interface of the concrete and steel. In an earlier experimental study, four specimens of composite beams of similar concrete strength were tested under monotonic loading in order to produce reliable results. One specimen was from a lower grade of concrete and was tested in order to calibrate the shear resistance and the failure mode. One bare steel perforated section with web openings was also tested as a comparison. The comparison between the experimental and the computational results leads to useful conclusions. The results for the composite beams show a significant increase in shear resistance. The shear enhancement demonstrated in this study can now be used in design practice

Applications of topology optimization in structural engineering: High-rise buildings and steel components

This study introduces applications of structural topology optimization to buildings and civil engineering structures. Topology optimization problems utilize the firmest mathematical basis, to account for improved weight-to-stiffness ratio and perceived aesthetic appeal of specific structural forms, enabling the solid isotropic material with penalization (SIMP) technique. Structural topology optimization is a technique for finding the optimum number, location and shape of “openings” within a given continuum subject to a series of loads and boundary conditions. Aerospace and automotive engineers routinely employ topology optimization and have reported significant structural performance gains as a result. Recently, designers of buildings and structures have also started investigating the use of topology optimization, for the design of efficient and aesthetically pleasing developments. This paper examines two examples of where topology optimization may be a useful design tool in civil/structural engineering in order to overcome the frontiers between civil engineers and engineers from other disciplines. The first example presents the optimized structural design of a geometrically complex high-rise structure and the optimal design of its architectural building shape. The second one focuses on the optimization and design of a perforated steel I-section beam, since such structural members are widely used nowadays in the vast majority of steel buildings and structures while they provide numerous advances. Conclusions are drawn regarding the potential benefits to the more widespread implementation of topology optimization within the civil/structural engineering industry

Structural performance of perforated steel beams with novel web openings and with partial concrete encasement

The research covered in this thesis is concerned with the effects of the behaviour and load carrying capacities of classes of steel beam structures with various shapes of web openings. A comprehensive investigation on non-composite and partially concrete encased perforated steel Isections with large web openings positioned along the centre-line of the beams was undertaken. This thesis enhances the current knowledge on these classes of perforated beams, as previous research has shown that these beams are susceptible to various failure modes, due to the existence of large web openings. Currently, perforated steel beams with large web openings are utilised in most engineering applications such as infrastructure, ship building and aeronautical engineering. The most significant benefits of using such beams are the achievement of reductions in weight and accommodation of services within their structural depth of floor systems. Specifically, in building applications, service integration eliminates the internal columns and supports, produces lighter structures which leading to reduced construction and installation time and results in cost effective structural forms and uses. However, many uncertainties are associated with perforated beams as well as non-standard methodology is used for their assessment. Perforated beams with standard circular, hexagonal and elongated web openings are most widely used nowadays, whilst various non-standard web opening shapes, such as `elliptical', are introduced through this thesis for first time. These new pioneering web opening shapes improve the structural performance of the perforated beams when examined under two critical failure modes (i. e. shear-'Vierendeel' mechanism and web-post buckling). Moreover, the manufacturing procedure of the `elliptical' web openings show great advantage in comparison with the manufacturing way of the more popular perforated beams with circular web openings (i. e. cellular beams). Also, other web opening shapes are reported and examined in this thesis. Furthermore, the novelty of the work seems to consist of the treatment of web openings of somewhat greater web opening depth than those usually considered and the introduction of a new class of composite concrete-steel beam. Despite the abundant experimental work on perforated steel beams that has been conducted by researchers throughout the years, the results are not comprehensive, due to the complexity of the beam configuration and the large number of variable parameters. Therefore, using commercially available finite element (FE) software, numerical analyses were verified by comparison to a new experimental programme designed to test each of the new structural forms. The numerical programme was then used to undertake extensive parametric studies to isolate some of the geometric and material properties that influence the failure modes associated with each of the new forms of structural systems. The main parameters under consideration are the web opening depth (noted usually as diameter), the critical opening length of the top and bottom tee-sections, the web opening spacing, the steel flange and web thicknesses, the concrete strength and contact properties between the steel and concrete of the newly formed composite beams. Detailed study of plastic hinges formation (i. e. high stress concentrations) was also employed in the vicinity of the web openings, by conducting both experimental and finite element (FE) investigation. This research study should now lead to better management of the use of perforated beams with large web openings as the profound difference between the novel and the conventional perforated beams is demonstrated. Useful practical applications of the so-called structural forms would be of particular interest in the general engineering, not just because of their superior structural performance, but also because of their low cost in manufacturing and usage. Another contribution is the investigation of the partial steel encasement with the concrete in-fill, on the percentage of enhancement of the steel perforated beams with web openings under high shear forces as well as on the distinction which is drawn between the conventional and the new composite beams. Finally, a further indirect outcome of this research thesis is the excellent agreement between the experimental and FE analyses as well as the data that can be used by future researchers to widen the above research to various engineering applications

Application of Topology Optimisation to Steel Node-Connections and Additive Manufacturing

Structural Topology Optimisation (STO) is a prevalent optimisation technique used nowadays to reach desired weight-to-stiffness ratios via highly complex and efficient designs unable to achieve otherwise. Additive manufacturing (AM) is widely known in the manufacturing industry and provides designers with a higher degree of freedom in realising highly optimised designs through a layer-based fabrication process. This paper focuses on reticulated structures and proposes using STO and AM to design and fabricate alternative connection designs with outstanding bespoke performance and drastically reduced weight. It studies the optimisation of a conventional node-connection found in reticulated timber structures under four loading cases, to producing state-of-the-art optimised connection designs, each capable of withstanding one of the four selected loading cases. The results are compared with the conventional node-connection, and the optimised configurations achieved up to 46.9% weight reduction. A selection of the highly bespoke scaled-down designs was additively manufactured in two different materials (metallic and polymer) as a proof of concept for the capacity of the technologies available for future testing