271 results found
Jiang B, Li G-Q, Li L, et al., 2018, Experimental Studies on Progressive Collapse Resistance of Steel Moment Frames under Localized Furnace Loading, JOURNAL OF STRUCTURAL ENGINEERING, Vol: 144, ISSN: 0733-9445
Minga E, Macorini L, Izzuddin BA, 2018, Enhanced mesoscale partitioned modelling of heterogeneous masonry structures, International Journal for Numerical Methods in Engineering, ISSN: 0029-5981
© 2018 John Wiley & Sons, Ltd. This paper presents an accurate and efficient computational strategy for the 3-dimensional simulation of heterogeneous structures with unreinforced masonry components. A mesoscale modelling approach is employed for the unreinforced masonry parts, whereas other material components are modelled independently with continuous meshes. The generally nonmatching meshes of the distinct domains are coupled with the use of a mesh tying method. The physical interaction between the components is captured with the use of zero-thickness cohesive interface elements. This strategy enables the optimisation of the individual meshes leading to increased computational efficiency. Furthermore, the elimination of the mesh compatibility requirement allows the 3-dimensional modelling of complex heterogeneous structures, ensuring accurate representation of each component's nonlinear behaviour and their interaction. Numerical examples, including a comparative analysis on the elastic and nonlinear response of a masonry bridge considering arch-backfill interaction and the nonlinear simulation of a multileaf wall, are presented to show the unique features of the proposed strategy and its predictive power in comparison with experimental and numerical results found in the literature.
Zhang Y, Macorini L, Izzuddin BA, 2018, Numerical investigation of arches in brick-masonry bridges, STRUCTURE AND INFRASTRUCTURE ENGINEERING, Vol: 14, Pages: 14-32, ISSN: 1573-2479
Abidin ARZ, Izzuddin BA, Lancaster F, 2017, A meshfree unit-cell method for effective planar analysis of cellular beams, COMPUTERS & STRUCTURES, Vol: 182, Pages: 368-391, ISSN: 0045-7949
Boyez A, Sadowski AJ, Izzuddin BA, 2017, A novel 'boundary layer' finite element for the efficient analysis of thin cylindrical shells, COMPUTERS & STRUCTURES, Vol: 182, Pages: 573-587, ISSN: 0045-7949
Chisari C, Macorini L, Amadio C, et al., 2017, Optimal sensor placement for structural parameter identification, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, Vol: 55, Pages: 647-662, ISSN: 1615-147X
Izzuddin BA, Jokhio GA, 2017, Mixed-Dimensional Coupling for Parallel Partitioned Nonlinear Finite-Element Analysis, JOURNAL OF COMPUTING IN CIVIL ENGINEERING, Vol: 31, ISSN: 0887-3801
Izzuddin BA, Liang Y, 2017, A hierarchic optimisation approach towards locking-free shell finite elements, Computers and Structures, ISSN: 0045-7949
© 2017 Elsevier Ltd. A hierarchic optimisation approach is presented for relieving inaccuracies in conforming shell elements arising from locking phenomena. This approach introduces two sets of strain modes: (i) objective strain modes, defined in the physical coordinate system, and (ii) corrective strain modes, representing conforming strains enhanced with hierarchic strain modes. This leads to two alternative families of element, objective and corrective, both arising from minimising the difference between objective and corrective strains. Importantly, the proposed approach not only alleviates shear and membrane locking, but it also addresses locking arising from element distortion. The application of the proposed optimisation approach is demonstrated for a 9-noded quadrilateral Lagrangian shell element, where the membrane, bending and transverse shear strains are separately optimised, all within a local co-rotational framework that extends the element application to geometric nonlinear analysis. Several numerical examples, including cases with geometric and material nonlinearity, are finally presented to illustrate the effectiveness of the optimised 9-noded shell element in relieving the various sources of locking.
Jiang B, Li GQ, Li L, et al., 2017, Simulations on progressive collapse resistance of steel moment frames under localized fire, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 138, Pages: 380-388, ISSN: 0143-974X
Li Z, Izzuddin BA, Vu-Quoc L, et al., 2017, A 3-NODE CO-ROTATIONAL TRIANGULAR ELASTO-PLASTIC SHELL ELEMENT USING VECTORIAL ROTATIONAL VARIABLES, ADVANCED STEEL CONSTRUCTION, Vol: 13, Pages: 206-240, ISSN: 1816-112X
Lima C, Martinelli E, Macorini L, et al., 2017, Modelling beam-to-column joints in seismic analysis of RC frames, EARTHQUAKES AND STRUCTURES, Vol: 12, Pages: 119-133, ISSN: 2092-7614
Micallef M, Vollum RL, Izzuddin BA, 2017, Investigating the need for long laps in reinforced concrete elements, Pages: 1549-1557
© Springer International Publishing AG 2018. The current Eurocode 2 (EN 1992-1-1) detailing rules can lead to considerably greater lap and anchorage lengths than previous design recommendations such as the superseded British Standard BS 8110-1. Moreover, fib Model Code 2010 (MC 2010) requires even longer laps than EN 1992-1-1. This research is motivated by complaints from industry that designing to the current EN 1992-1-1 detailing rules leads to numerous construction issues such as reinforcement congestion, as well as cost and sustainability implications, with no apparent justification. This paper presents the experimental programme which was conducted by the authors with a view to justifying reduced lap lengths more commensurate with previously proven UK experience. To this end, a series of three point bending (3PB) and four point bending (4PB) tests were designed and tested in the Structures Laboratory at Imperial College London to investigate bond stress distributions along laps of different lengths consisting of lapped reinforcing bars of the same or different bar diameters. In particular, experiments were aimed at quantifying the effectiveness of very long laps in transferring forces between two lapped bars. The 3PB tests were aimed at investigating whether anchorage capacity of laps is enhanced at high shear locations.
Micallef M, Vollum RL, Izzuddin BA, 2017, Crack development in transverse loaded base-restrained reinforced concrete walls, ENGINEERING STRUCTURES, Vol: 143, Pages: 522-539, ISSN: 0141-0296
Micallef M, Vollum RL, Izzuddin BA, 2017, Cracking in walls with combined base and end restraint, MAGAZINE OF CONCRETE RESEARCH, Vol: 69, Pages: 1170-1188, ISSN: 0024-9831
Minga E, Macorini L, Izzuddin BA, 2017, A 3D mesoscale damage-plasticity approach for masonry structures under cyclic loading, Meccanica, Pages: 1-21, ISSN: 0025-6455
© 2017 Springer Science+Business Media B.V., part of Springer Nature This paper deals with the accurate modelling of unreinforced masonry (URM) behaviour using a 3D mesoscale description consisting of quadratic solid elements for masonry units combined with zero-thickness interface elements, the latter representing in a unified way the mortar and brick–mortar interfaces. A new constitutive model for the unified joint interfaces under cyclic loading is proposed. The model is based upon the combination of plasticity and damage. A multi-surface yield criterion in the stress domain governs the development of permanent plastic strains. Both strength and stiffness degradation are captured through the evolution of an anisotropic damage tensor, which is coupled to the plastic work produced. The restitution of normal stiffness in compression is taken into account by employing two separate damage variables for tension and compression in the normal direction. A simplified plastic yield surface is considered and the coupling of plasticity and damage is implemented in an efficient step by step approach for increased robustness. The computational cost of simulations performed using the mesoscale masonry description is reduced by employing a partitioning framework for parallel computation, which enables the application of the model at structural scale. Numerical results are compared against experimental data on realistic masonry components and structures subjected to monotonic and cyclic loading to show the ability of the proposed strategy to accurately capture the behaviour of URM under different types of loading.
Tubaldi E, Macorini L, Izzuddin BA, et al., 2017, A framework for probabilistic assessment of clear-water scour around bridge piers, STRUCTURAL SAFETY, Vol: 69, Pages: 11-22, ISSN: 0167-4730
Xavier FB, Macorini L, Izzuddin BA, et al., 2017, Pushdown Tests on Masonry Infilled Frames for Assessment of Building Robustness, JOURNAL OF STRUCTURAL ENGINEERING, Vol: 143, ISSN: 0733-9445
Guo L, Xiang J, Latham JP, et al., 2016, A numerical investigation of mesh sensitivity for a new three-dimensional fracture model within the combined finite-discrete element method, Engineering Fracture Mechanics, Vol: 151, Pages: 70-91, ISSN: 0013-7944
© 2015 The Authors. Recently a new three-dimensional fracture model has been developed in the context of the combined finite-discrete element method. In order to provide quantitative guidance for engineering applications, mesh size and orientation sensitivity are investigated by specially designed numerical tests. The mesh size sensitivity is analysed by modelling a single tensile fracture propagation problem and three-point bending tests using a series of models with the same geometry but different structured mesh sizes. The mesh orientation sensitivity is investigated by diametrically compressing a disc specimen of unstructured meshes from different angles. The computational efficiency of the three-dimensional fracture model is also studied.
Izzuddin BA, Liang Y, 2016, Bisector and zero-macrospin co-rotational systems for shell elements, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Vol: 105, Pages: 286-320, ISSN: 0029-5981
Jiang B, Li G-Q, Izzuddin BA, 2016, Dynamic performance of axially and rotationally restrained steel columns under fire, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 122, Pages: 308-315, ISSN: 0143-974X
Li ZX, Zheng T, Vu-Quoc L, et al., 2016, A 4-Node Co-Rotational Quadrilateral Composite Shell Element, INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS, Vol: 16, ISSN: 0219-4554
Liang Y, Izzuddin BA, 2016, Large displacement analysis of sandwich plates and shells with symmetric/asymmetric lamination, COMPUTERS & STRUCTURES, Vol: 166, Pages: 11-32, ISSN: 0045-7949
Liang Y, Izzuddin BA, 2016, An optimisation approach towards locking-free isotropic shell elements, Pages: 491-497
© 2016 Taylor & Francis Group, London. The locking phenomena in finite elements is characterised by degraded element performance, principally owing to the inability of the finite element to generate lower-order strain modes. An optimisation approach was previously established to overcome locking, which remedies locking by enriching conforming strain terms with a set of hierarchic terms, and optimising the enriched strains towards an objective low-order strain distribution via mathematical optimisation. In this paper, a J2 invariant-based optimisation function is proposed, which ensures the improved strain tensor to be invariant to the choice of local coordinates and nodal ordering. The modified optimisation approach provides a systematic way of eliminating locking in shell elements for both quadrilateral and triangular elements. Its application to 6-noded and 9-noded shell elements is presented, within the context of large displacement analysis. Linear and geometrically nonlinear numerical examples are finally provided to demonstrate the effectiveness of the proposed shell elements.
Liang Y, Lancaster F, Izzuddin BA, 2016, Effective modelling of structural glass with laminated shell elements, COMPOSITE STRUCTURES, Vol: 156, Pages: 47-62, ISSN: 0263-8223
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2016, Robustness assessment of frame structures using simplified beam and grillage models, ENGINEERING STRUCTURES, Vol: 115, Pages: 78-95, ISSN: 0141-0296
Stylianidis PM, Nethercot DA, Izzuddin BA, et al., 2016, Study of the mechanics of progressive collapse with simplified beam models, ENGINEERING STRUCTURES, Vol: 117, Pages: 287-304, ISSN: 0141-0296
Xavier FB, Macorini L, Izzuddin BA, 2016, Contribution of masonry cladding for robustness enhancement of multi-storey buildings under sudden column loss, Pages: 1383-1391
© 2016 Taylor & Francis Group, London. This work addresses the influence of non-structural masonry infill on the resistance of multi-storey buildings to progressive collapse under sudden column loss scenarios. The realistic contribution of masonry panels towards collapse arrest is examined considering the results from full-scale laboratory tests and accurate numerical simulations. Novel real-scale tests are performed on different two-bay frames with brick-masonry infill subjected to incremental pushdown deformation, capturing the dominant deformation mode actually found following removal of an edge column. Different infill configurations are tested, including central openings and initial gaps between masonry and frame elements. Overall, a global stable response is found leading to monotonic energy absorption with increasing vertical deflections. This translates into considerable robustness reserve associated with the confined infill walls. Subsequently, advanced mesoscale finite element simulations are employed to capture the complex frameinfill interaction in the early stages of pushdown response. This modelling strategy is then used on a case study considering a realistic multi-storey frame building with masonry infill. The energy-based robustness assessment framework previously developed at Imperial College London is applied enabling a critical comparison between the collapse resistance arising from different mechanisms typically considered in this context (such as floor membrane and beam catenary effects) and that related to the presence of masonry infill. While the former mechanisms are quite effective at relatively large deformations, the latter is shown to add substantial contribution at small displacements. Given the widespread application of masonry infill, the conclusions in this work are particularly relevant within the context of retrofitting operations for robustness enhancement of existing structures, in view of the growing demand for upgrad
Zhang Y, Macorini L, Izzuddin BA, 2016, Mesoscale partitioned analysis of brick-masonry arches, ENGINEERING STRUCTURES, Vol: 124, Pages: 142-166, ISSN: 0141-0296
Bilbao A, Izzuddin BA, Vollum RL, 2015, Enhanced nonlinear analysis of three-dimensional concrete structures using damage plasticity modelling, ISSN: 1759-3433
© Civil-Comp Press, 2015. This paper presents an improved numerical procedure for the nonlinear analysis of three-dimensional continuum concrete structures employing damage-plasticity constitutive modelling. Previous convergence difficulties when performing singlestep return mappings for larger strain increments necessitated resorting to substepping methods, at the cost of a greater computational expense when calculating the consistent algorithmic tangent stiffness. Quadratic convergence rate at the global level while maintaining the single-step return scheme for the constitutive model is achieved here with a potential reduction in the number of simultaneous equations and with the utilisation of a basic line search technique for particular cases. Initial singularity of the Jacobian matrix is thereby avoided, ensuring a reduction in the convergence measure towards the converged solution. The improved robustness of the enhanced algorithm is confirmed, and its performance at larger scale is demonstrated through two benchmark application examples.
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