This paper presents theoretical descriptions of the key phenomena that govern the behaviour of composite framed structures in fire. These descriptions have been developed in parallel with large scale computational work undertaken as a part of a research project (The DETR-PIT Project, Behaviour of steel framed structures under fire conditions) to model the full-scale fire tests on a composite steel framed structure at Cardington (UK). Behaviour of composite structures in fire has long been understood to be dominated by the effects of strength loss caused by thermal degradation, and that large deflections and runaway resulting from the action of imposed loading on a 'weakened' structure. Thus 'strength' and 'loads' are quite generally believed to be the key factors determining structural response (fundamentally no different from ambient behaviour). The new understanding produced from the aforementioned project is that, composite framed structures of the type tested at Cardington possess enormous reserves of strength through adopting large displacement configurations. Furthermore, it is the thermally induced forces and displacements, and not material degradation that govern the structural response in fire. Degradation (such as steel yielding and buckling) can even be helpful in developing the large displacement load carrying modes safely. This, of course, is only true until just before failure when material degradation and loads begin to dominate the behaviour once again. However, because no clear failures of composite structures such as the Cardington frame have been seen, it is not clear how far these structures are from failure in a given fire. This paper attempts to lay down some of the most important and fundamental principles that govern the behaviour of composite frame structures in fire in a simple and comprehensible manner. This is based upon the analysis of the response of single structural elements under a combination of thermal actions and end restraints representing the surrounding structure. r

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We study the effects of phase behavior on the evaporative drying of droplets of a suspension of hard-sphere colloidal particles and nonadsorbing polymer. The presence of the polymer induces a depletion attraction between the colloidal particles. As drying (evaporation of solvent) progresses, the concentrations of both colloid and polymer increase, so that the droplet's average composition traces out a “drying line” across the composition diagram. We find that drying behavior can be broadly classified according to the initial composition of the suspension, into three regions on a “drying behavior diagram”. We relate these three regions to the bulk phase diagram of the system and show how drying behavior and final residue properties such as homogeneity can be understood by considering the orientation of the “drying line” with respect to the equilibrium and nonequilibrium boundaries in the bulk phase diagram. Our findings have relevance for predicting the sensitivity of droplet and film residue properties to initial suspension composition, in the case of technologically important systems such as detergents, coatings, ceramics, and paints, as well as being an interesting example of the response of a model soft matter system continuously driven across its phase diagram toward a shifting “target” equilibrium.

Keywords:Modelling masonry Surface-based cohesive behaviour XFEM Crack propagation In-plane load Out of plane load Cyclic in-plane load a b s t r a c tIn this paper, a simplified micro-model approach utilising a combination of plasticity-based constitutive models and the extended finite element method (XFEM) is proposed. The approach is shown to be an efficient means of simulating the three-dimensional non-linear behaviour of masonry under monotonic in-plane, out of plane and cyclic loads. The constitutive models include surface-based cohesive behaviour to capture the elastic and plastic behaviour of masonry joints and a Drucker Prager (DP) plasticity model to simulate crushing of masonry under compression. The novel use of XFEM in simulating crack propagation within masonry units without initial definition of crack location is detailed. Analysis is conducted using standard finite element software (Abaqus 6.13) following a Newton Raphson algorithm solution without employing user-defined subroutines. The capability of the model in terms of capturing nonlinear behaviour and failure modes of masonry under vertical and horizontal loads is demonstrated via comparison with a number of published experimental studies.