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Recent disruptive technological advances, including wire arc additive manufacturing (WAAM) and the concept of digital twins, have the potential to fundamentally transform the way in which we design, build and manage structures. WAAM is a method of metal 3D printing that is well suited to the price-sensitive construction industry and has been used to manufacture the MX3D bridge – the world’s first metal additively manufactured bridge. The intricate geometry, undulating surface finish and particular material properties rendered the bridge outside the scope of any existing structural design standards; hence, physical testing and advanced numerical modelling were carried out for its safety assessment. The key features of the finite element model of the bridge, and its validation against in-situ structural tests, are described herein. Subsequent numerical studies undertaken to verify the structural performance of the bridge under various loading scenarios are presented, while the basis for the development of the smart digital twin of the bridge is also introduced. The presented research provides insight into the use of advanced computational simulations for the verification and ongoing assessment of structures produced using new methods of manufacture.

Copyright © 2022 The Author(s). An experimental and numerical study into the behaviour of concrete-filled double skin tubular (CFDST) stub columns is presented. A total of eight axial compression tests were carried out, four utilising conventional concrete and four with recycled aggregate concrete. The stub columns were circular in cross-section and each comprised an austenitic stainless steel outer tube and a carbon steel inner tube, of varying dimensions. Accordingly, hollow ratios of 0.67 and 0.55 were considered. The recycled coarse aggregate was made by crushing test specimens from a previous research project, and a replacement ratio of 50% was adopted. During the experiments, similar structural behaviour and failure modes were observed between the specimens with conventional and recycled aggregate concrete. To investigate the behaviour further, a finite element model was developed in ABAQUS; validation of the model against the experimental results from the current work as well as data available in the literature is described. The finite element model was employed to conduct a parametric study to examine the load-bearing contributions of the constituent components of CFDST sections and to assess the influence of the hollow ratio on the structural behaviour. The experimental and numerical ultimate loads are compared with the capacity predictions determined using available design procedures. Overall, the results show that CFDST stub columns with recycled aggregate concrete can achieve similar capacities to their conventional concrete counterparts, demonstrating the potential for the wider use of recycled aggregate concrete, towards more sustainable structural solutions. CNPq (305143/2015-8; 306042/2013-4; 305026/2017-8) and FAPERJ (E-26/202.789/2017; E-26/010.101216/2018; E-26/202.924/2019 and E-26/202.532/2018).

This paper presents an experimental and numerical investigation into the stability of normal and high strength steel circular hollow section (CHS) columns. Two cold-formed S700 CHS profiles – 139.7×4 and 139.7×5 (in mm), were studied in the experimental programme, and twelve column tests (six on each profile), together with accompanying material tests, were performed. The load-deformation histories and key results from the tests are reported. Following the physical testing, a numerical simulation campaign was conducted. The developed finite element (FE) models for CHS columns were initially validated against the test results. Parametric studies were then carried out, where 2000 additional buckling resistance data were numerically generated for hot-finished and cold-formed CHS columns, covering steel grades from S355 to S900. The obtained test and FE results, together with existing experimental data from the literature, were used to assess the current Eurocode 3 stability design rules. It was shown that the normalised performance of CHS columns is influenced by the yield strength, which is not fully captured by the EC3 design approach. The somewhat conservative Class 3 slenderness limit for compression further worsen the accuracy for those with slender cross-sections. Improvements to the EC3 design rules were proposed to address these shortcomings, including (a) modified Ayrton-Perry formulae enabling a continuous transition of buckling curves across the yield strength spectrum and (b) a new Class 3 limit for CHS in compression. The modified EC3 approach was assessed and shown to improve the accuracy and consistency of resistance predictions over the current EC3 approach, while meeting the Eurocode structural reliability requirements.

A stiffness-based method for the preliminary design of outrigger braced skyscrapers is proposed. The method is founded on the concept of uniform distribution of deformation. This approach originates from the minimum-compliance optimization, in which the stiffest layout for the structure is sought for a given amount of material. Design variables include: the flexural stiffness of the core structure, the outrigger-belt elevation, and the peripheral column dimensions. These parameters are specified by requiring the curvature to be kept constant, yet minimum, as long as the allowable stress and displacement constraints are imposed. The resulting procedure is presented through a simplified hand-calculation algorithmic framework, which may be used during the preliminary design stage to estimate the size of elements and to give an initial assessment of the structural behavior. In order to show the practical application of the proposed method, a structure equipped with one outrigger is designed using the proposed algorithm. The comparative analysis of the results reveals that the presented method provides a rather high degree of accuracy in practice.

The material and connection behaviour in sheathed cold-formed steel wall systems are investigated in the present paper through experimentation. A total of 103 material and component tests was performed, including six cold-formed steel tensile coupon tests, nine tests on screws in tension, nine tests on screws in shear, 36 material tests on plasterboard and orientated strand board (OSB), 25 pull-through connection tests and 18 push-out (shear) connection tests. The plasterboard and oriented strand board were tested in both compression and tension, as well as both longitudinally and transversely to the production direction of the board. The main objective of the study was to measure and characterise the nonlinear response of all the materials and sheathing-to-steel connection components that are used in typical cold-formed steel wall systems, to support the ongoing and future development of accurate numerical simulations and structural design provisions for such systems. The present paper focuses on the experimental investigation and the collection of existing test data from the literature; a description of all the tests performed and a discussion of the results obtained are provided. The companion paper focuses on the establishment and assessment of predictive models to describe the responses of the material and connection components.

The paper investigates the influence of support elongation on punching resistance at internal slab column connections without shear reinforcement. Nonlinear finite element analysis (NLFEA) with 3-D solid elements is used to study the influence of column elongation on stress and strain in the slab around the column. Punching failure is shown to be triggered by localised peaks in shear stress around the corners of the support. Significantly, one-way shear is shown to increase the shear resistance of slabs supported on columns with cross sectional dimensions greater than around six times the slab effective depth ( d ). The common laboratory practice of supporting slabs in punching tests on elongated plates rather than columns is investigated numerically and is found to be reasonable despite uplift occurring in the central region of elongated plates. NLFEA with solid elements gives useful insights into punching failure but nonlinear shell elements are better suited to the practical assessment of slabs in building structures. The disadvantage of conventional nonlinear shell elements is that shear failure can only be detected through post processing of results. To circumvent this, the authors have previously developed a novel modelling approach in which 3-D joint elements are used to connect shell elements located to either side of a punching control perimeter positioned at 0.5 d from the column face. The joint shear resistance is calculated using the Critical Shear Crack Theory (CSCT) in which punching resistance is related to slab rotation. Based on insights gained using the solid element modelling, this paper extends the use of the joint model to the modelling of punching failure at elongated supports by including one-way joints to model linear shear.

An experimental investigation into the behaviour of connections between cold-formed steel and timber components, formed with inclined screws, is presented. A series of material tests was firstly carried out to assess the behaviour and limitations of each component of the system under investigation. These were supplemented by three types of interaction test: timber embedment, screw head pull-through and screw thread withdrawal, all aimed at developing a better understanding of the behaviour of the different components of the connection. The slip modulus and peak load-carrying capacity of twelve connection configurations were determined through a series of push-out tests. The results obtained were compared to the typical benchmark arrangement in which the screws were driven in perpendicular to the steel-timber interface. Component variations included the type of timber – particle board and plywood, the thickness of the steel – 1.5 mm and 2.4 mm thick, the inclination of the screws – 0° and 45°, and the presence or not of wings on the screws. The results showed that non-winged screws inclined at 45° gave up to about a 30% increase in peak load-carrying capacity and about a 140% increase in slip modulus when compared to the reference specimen.