This paper presents a new triangular flat shell element for composite and reinforced concrete slabs of complex planar configuration subjected to extreme loading. The element is developed within a co-rotational framework, and it incorporates the effects of geometric as well as material nonlinearities. To improve the approximation of the solution and deal with shear locking, additional hierarchic parameters are introduced within the local system of the element, providing an option to activate higher-order quadratic approximation for the element shape functions. The element formulation allows for composite action between different layers under the assumption of perfect bond between the slab concrete material, the reinforcement layers and the steel deck for composite slabs. To account for floor slabs of irregular geometric configurations, due allowance is made for uniaxial reinforcement to be oriented arbitrarily within the slab plane. Furthermore, an algorithm for automatic rebar orientation is developed for irregular slabs with realistic reinforcement distributions. The paper briefly describes the element formulation followed by several numerical verification examples. The applicability of the element to modelling concrete slabs is demonstrated via several validation studies against existing experimental results. The versatility of the element is further exemplified with a realistic large-scale floor slab model subjected to extreme loading scenarios. It is shown that the developed element provides a good balance between accuracy and efficiency in the modelling of irregular floor slabs subject to extreme loading conditions.
A substantial part of the underline bridges that belong to the asset collection of the main railway and roadway infrastructure operators in the UK and Europe have the structural shape of arches, typically constructed from brick/stone masonry. Current assessment methods, which consider two-dimensional descriptions, do not enable an accurate representation of the typical three-dimensional response, and often they do not provide realistic predictions of the development of damage in the various components including arches, piers and spandrel walls. In this paper, two alternative 3D finite-element modelling strategies offering different balance between sophistication and computational efficiency are presented. The first approach is based on a detailed mesoscale masonry model, where a distinction is made between constituents allowing for an accurate description of masonry under various bond conditions. The second approach is based on a macroscale representation, where a homogeneous description of masonry is assumed. In both approaches, the interactions between the spandrel walls and the backfill and arches, as well as between the backfill and the arches’ extrados, are explicitly incorporated into the model. This interaction effect is investigated with the two approaches, and comparisons are made between the respective simulations to illustrate the relative benefits of mesoscale and macroscale modelling.
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