Benchmarking for the inclusion of shear studs in finite element models

There are many aspects of shear stud behaviour that may affect a heated steel-concrete composite structure in fire such as stud layout, ductility and strength; heated material behaviour; loss of composite action through the failure of multiple studs; and so on. This paper attempts to understand the role of shear studs on full structural behaviour in fire during both heating and cooling. Predictions of stud behaviour at ambient temperature using numerical models are first compared to experimental work to benchmark the modelling approach. A good correlation is found. This is followed by the analysis of full structural behaviour in fire where shear stud properties are varied parametrically. Individual shear studs are modelled so it is possible to identify which studs fail and at what point in the fire. The results demonstrate the importance of ensuring continued composite action in fire

Modelling progressive failure of steel moment frames exposed to localised fire

This paper presents modelling of the progressive failure of steel moment frames subjected to localised fire. A finite element approach using the software ABAQUS has been developed to analyse the structure. An explicit-dynamic solution was adopted to solve the non-convergence problems caused by element buckling. A series of validation analyses were carried out to ensure that the results were within an acceptable level of accuracy. The analysis results are shown to match well with the previous experimental data and analysis. This modelling approach allows detailed insights to be obtained into the structural robustness of such frames in fire situations

CFRP Strengthening of Steel Beams with Web Openings

Integration of services via web-openings in steel floor beams is often unavoidable in modern frame buildings. Such web-openings can significantly reduce the shear and bending strength capacity of the beams. Traditionally, the welding of additional steel plates to the opening areas is adopted as a means of strengthening and stiffening. This not only presents practical difficulties but can induce residual stresses which weaken fatigue performance of the section. This study explores the use of externally bonded carbon fibre reinforced polymer composites (CFRP) as an alternative means of strengthening. Using a non-linear finite element approach, the effect of strengthening arrangement is investigated with a view to finding the most structurally efficient layout. For the series studied significant enhancements of strength comparable to those achieved by welded plates, have been predicted

Progressive collapse analysis of composite steel frames subject to fire following earthquake

This paper presents three-dimensional progressive collapse analyses of composite steel frames exposed to fire following earthquake. The scenarios of heating columns located in various different fire compartments (internal, edge and corner bay) are first studied to investigate load redistribution paths and members’ interactions within the composite frame. The results show that the loads previously supported by the heated columns are redistributed to adjacent columns along two horizontal directions, a phenomenon which cannot be captured in a 2D model. Then, the 3D model is adopted to investigate the effect of residual deformation after an earthquake on the progressive collapse behaviour of the composite building. It is found that neither the load redistribution path nor the fire resistance of the building is considerably affected by the residual deformation. A series of progressive collapse analyses subjected to travelling fires resulting from fire compartment damage is also performed. It is concluded that the survival of the building can be greatly affected by the spatial nature of the travelling fire as well as the inter-zone time delay

Experimental investigation of CFRP-strengthened steel beams with web openings

The introduction of web openings in existing steel floor beams is a common occurrence in practice. Such modifications are often necessary to accommodate additional services driven by a change of building use, thus extending the service life of the structure. Depending on their size and location, openings in the web can present a major challenge to the strength and stiffness of the beam. Strengthening around an opening is often necessary to maintain the required performance of the floor beam, traditionally this is affected via application of additional steel plate, either bolted or welded. This paper focusses on the novel application of carbon fibre reinforced polymer (CFRP) to the problem of strengthening web openings, taking advantage of the material's ease of handling, superior strength-to-weight ratio and corrosion resistance. An experimental study involving 4 full scale universal beams was conducted in order to investigate the ability of CFRP to recover the strength and stiffness of beams following the introduction of web openings. All the specimens were tested under 6-point bending in the experiments. For further comparison, the equivalent test series without the addition of strengthening was modelled numerically via finite element analysis.. The effectiveness of the strengthening technique was demonstrated with increases in the load carrying capacity over the un-altered beam of between 5 and 20% being achieved

Interaction Diagrams for Ambient and Heated Concrete Sections

Bending moment axial force interaction diagrams are a commonly used tool in any design office. When designing for fire conditions, the large axial forces which develop place an additional importance on the consideration of the interplay between axial forces and moments. This paper presents a new method for calculating the biaxial bending moment/axial force capacity for a general section through the use of the sectional tangent stiffness. A beam-column section subject to fire is assessed, and comparisons made with simplified design tools. It is concluded that derivation of the interaction surface from the tangent stiffness matrix is possible, and that current simplified methods for fire design cannot be assumed conservative