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.

Numerical modelling by the meshless method of smoothed-particle hydrodynamics can offer quantification of tsunami wave pressures at a greater level of detail and accuracy than existing empirical methods, enabling more effective design solutions to be derived. In this paper, smoothed-particle hydrodynamics modelling of tsunami wave and structure interaction is undertaken to derive the time histories of wave pressure distributions, which can then be used by way of finite-element software to evaluate the structural response. In a series of comparative studies with physical models, the numerical results show good agreement with the experimental data. The research in this paper forms part of a wider investigation that aims to address the issue of improving resilience of shore-based structures in tsunami events.

Abrasive wear of concrete in coastal structures can be a significant issue in areas where coarse or gravel sediments abound. In such environments, abrasion may be the governing factor for concrete specification in new construction. In the case of hard defences, concrete will constitute a major project cost, thus necessitating optimisation of mix design. This briefing paper explores some of the background to the problem and existing approaches in design codes. A case study of a major coast protection scheme in the UK is discussed, focussing on the approach to concrete specification through abrasion testing.

2 3A series of three-dimensional smoothed particle hydrodynamics (SPH) and finite-element (FE) models, with a domain in the form of a water tank, were undertaken to simulate tsunami-induced bore impact on a discrete onshore structure on a dry bed. The fluid motion was simulated using the SPH-based software DualSPHysics. The tsunami-like waves were represented by solitary waves with different characteristics generated by the numerical paddle wavemaker. Numerical probes were uniformly distributed on the structure's vertical surface providing detailed measures of the pressure distribution across the structure. The peak impact locations on the structure's surface were specifically determined and the associated peak pressures then compared with the prediction of existing commonly used design equations. Using the pressure-time histories from the SPH model, FE analysis was conducted with Abaqus to model the dynamic response of a representative timber structure. The results show that the equations used to estimate the associated pressure for design purposes can be highly non-conservative. By gaining a detailed insight into the impact pressures and structure response, engineers have the potential means to optimise the design of structures under tsunami impact loads and improve survivability. Notation

In both building and civil engineering structures, the occurrence of impact loading to column elements can be a significant issue, particularly in regard to disproportionate collapse. For existing structures vulnerable to impacts, the development of appropriate strengthening techniques is key to extending service life and improving robustness. In the case of structural steelwork, composites such as carbon fibre reinforced polymer (CFRP) offer a promising means of retrofitting and improving performance under impact. Towards this, the present study experimentally investigated a total of 12 square hollow section (SHS) columns under impact loads. The test series included both unstrengthened and CFRP strengthened samples with different fibre orientations with a view to finding the optimum CFRP configuration. As a means of simulating lateral impact on axially loaded elements, a purpose-built test rig was manufactured to apply a compressive preload to the samples prior to impact. Different preloading levels were applied to the samples before they were impacted transversely. The results show that the strengthening effectiveness increased with higher preloading level. The average reduction in the transverse displacement for the strengthened columns tested under 70% preloading level was around 32% compared to the unstrengthened column while this value was about 22% for the columns tested without compressive preload.