Testing of a Full-Scale Composite Floor Plate

YesA full-scale composite floor plate was tested to investigate the flexural behavior and in-plane effects of the floor slab in a grillage of composite beams that reduces the tendency for longitudinal splitting of the concrete slab along the line of the primary beams. This is important in cases where the steel decking is discontinuous when it is orientated parallel to the beams. In this case, it is important to demonstrate that the amount of transverse reinforcement required to transfer local forces from the shear connectors can be reduced relative to the requirements of Eurocode 4. The mechanism under study involved in-plane compression forces being developed in the slab due to the restraining action of the floor plate, which was held in position by the peripheral composite beams; while the secondary beams acted as transverse ties to resist the forces in the floor plate that would otherwise lead to splitting of the slab along the line of the primary beams. The tendency for cracking along the center line of the primary beam and at the peripheral beams was closely monitored. This is the first large floor plate test that has been carried out under laboratory conditions since the Cardington tests in the early 1990s, although those tests were not carried out to failure. This floor plate test was designed so that the longitudinal force transferred by the primary beams was relatively high (i.e., it was designed for full shear connection), but the transverse reinforcement was taken as the minimum of 0.2% of the concrete area. The test confirmed that the primary beams reached their plastic bending resistance despite the discontinuous decking and transverse reinforcement at the minimum percentage given in Eurocode 4. Based on this test, a reduction factor due to shear connectors at edge beams without U-bars is proposed

Effects of thermal creep of prestressed steel on post-tensioned concrete slabs in and after fire

The effects of thermal creep of prestressing steel on post-tensioned concrete slabs in and after fire were investigated based on existing thermal creep model and calibrated parameters in this paper. A nonlinear finite element model was built up employing ABAQUS package, taking into account frictionless contact behaviour between prestressing steel tendons and surrounding concrete. The nonlinear material behaviour of concrete and prestressing steel at elevated temperatures was taken into account, where three material models for prestressing steel were adopted with or without considering thermal creep, and based on the model from EN 1992-1-2. The finite element model developed was verified against experimental results from the literature, showing that the model considering thermal creep was more accurate. Then the fire resistance period and responses of post-tensioned concrete slabs in and after fire were investigated based on the verified model. Ignoring thermal creep underestimated the fire resistance period but overestimated the residual tendon stresses. The model from EN 1992-1-2 achieved nearly the same effects as the model considering thermal creep in fire but might yield inaccurate evaluation of residual tendon stresses. The model considering thermal creep worked well under fire and in the post-fire conditions yielding reasonable predictions.postprin

Numerical study on the flexural behaviour of slim-floor beams with hollow core slabs at elevated temperature

[EN] Slim-floor beams are a novel typology of steel beams where the steel profile is fully embedded within the concrete floor depth. While the use of this system is increasing fast in the construction practice, the available investigations on its fire performance are still scarce. This paper focuses on analysing the fire behaviour of slim floor beams combined with hollow core slabs as flooring system. Two configurations are studied, namely Integrated Floor Beam (IFB) and Shallow Floor Beam (SFB). A finite element model is developed and validated by comparison with experimental results available in the literature as well as with thermal tests carried out by the authors. Subsequently, parametric studies are conducted with the aim of providing practical design recommendations. The influence of the composite beam configuration, concrete type, longitudinal reinforcement and steel plate thickness is studied. The conclusions drawn in this paper suggest that the SFB configuration may provide a significant enhancement in terms of fire resistance compared to IFB, provided that the appropriate combination of the parameters studied is used.The authors would like to express their sincere gratitude to the Spanish "Ministerio de Economia y Competitividad" for the help provided through the Project BIA2015-67192-R and to the European Union through the FEDER funds.Albero Gabarda, V.; Espinós Capilla, A.; Serra Mercé, E.; Romero, ML.; Hospitaler Pérez, A. (2019). Numerical study on the flexural behaviour of slim-floor beams with hollow core slabs at elevated temperature. Engineering Structures. 180:561-573. https://doi.org/10.1016/j.engstruct.2018.11.061S56157318

Post-fire Behaviour of Innovative Shear Connection for Steel-Concrete Composite Structures

YesSteel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three type of connectors were investigated. They are headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post fire condition of 200˚C, 400˚C and 600˚C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure

Stability of rectangular concrete-filled steel tubes

The paper deals with the theoretical analysis of the influence of imperfections on the stability and carrying capacity of axially compressed cold-formed rectangular steel tubes filled with concrete, which use as bearing structures in the structural engineering, bridges, underground subway systems and tunnels. The behavior of the mentioned above composite structures under load were presented by numerical modelling in software ABAQUS. The support conditions of loaded edges of the steel section were considered as clamped in the models. The results of the analysis were shown the influence of imperfections on the stability and carrying capacity of the composite 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

Combined web distortional and lateral-torsional buckling of partially restrained I-section beams

publisher: Elsevier articletitle: Combined web distortional and lateral-torsional buckling of partially restrained I-section beams journaltitle: International Journal of Mechanical Sciences articlelink: http://dx.doi.org/10.1016/j.ijmecsci.2017.06.057 content_type: article copyright: © 2017 Elsevier Ltd. All rights reserved

Material and local buckling response of ferritic stainless steel sections

Research Fund for Coal and Steel, Ministerio de Ciencia e Innovació

Axial behaviour of prestressed high strength steel tubular members

The axial behaviour of high strength steel tubular elements with internal prestress-ing cables, representing the chord members in prestressed trusses, is investigated herein. Ex-periments on tensile and compressive members were carried out, with the key variables exam-ined being the steel grade (S460 and S690), the initial prestress level and the presence of grout. FE models were developed to replicate the experiments and generate parametric results. The presence of cables was shown to enhance the tensile load-carrying capacity of the mem-bers while the application of prestress extended the elastic range. In compression, prestressing was detrimental, and a modified Perry-Robertson design approach was examined