275 results found
Boyez A, Sadowski AJ, Izzuddin BA, 2018, A ‘boundary layer’ finite element for thin multi-strake conical shells, Thin-Walled Structures, Vol: 130, Pages: 535-549, ISSN: 0263-8231
© 2018 Elsevier Ltd Multi-strake cylindrical and conical shells of revolution are complex but commonplace industrial structures which are composed of multiple segments of varying wall thickness. They find application as tanks, silos, circular hollow sections, aerospace structures and wind turbine support towers, amongst others. The modelling of such structures with classical finite elements interpolated using low order polynomial shape functions presents a particular challenge, because many elements must be sacrificed solely in order to accurately represent the regions of local compatibility bending, so-called ‘boundary layers’, near shell boundaries, changes of wall thickness and at other discontinuities. Partitioning schemes must be applied to localise mesh refinement within the boundary layers and avoid excessive model runtimes, a particular concern in incremental nonlinear analyses of large models where matrix systems are handled repeatedly. In a previous paper, the authors introduced a novel axisymmetric cylindrical shell finite element that was enriched with transcendental shape functions to capture the bending boundary layer exactly, permitting significant economies in the element and degrees of freedom count, mesh design and model generation effort. One element is sufficient per wall strake. This paper extends this work to conical geometries, where axisymmetric elements enriched with Bessel functions accurately capture the bending boundary layer for both 'shallow’ and 'steep’ conical strakes, which are characterised by interacting and independent boundary layers, respectively. The bending shape functions are integrated numerically, with several integration schemes investigated for accuracy and efficiency. The potential of the element is illustrated through a stress analysis of a real 22-strake metal wind turbine support tower under self-weight. The work is part of a wider project to design a general three-dimensional ‘bound
Chisari C, Macorini L, Amadio C, et al., 2018, Identification of mesoscale model parameters for brick-masonry, International Journal of Solids and Structures, Vol: 146, Pages: 224-240, ISSN: 0020-7683
© 2018 Realistic assessment of existing masonry structures requires the use of detailed nonlinear numerical descriptions with accurate model material parameters. In this work, a novel numerical-experimental strategy for the identification of the main material parameters of a detailed nonlinear brick-masonry mesoscale model is presented. According to the proposed strategy, elastic material parameters are obtained from the results of diagonal compression tests, while a flat-jack test, purposely designed for in-situ investigations, is used to determine the material parameters governing the nonlinear behaviour. The identification procedure involves: a) the definition of a detailed finite element (FE) description for the tests; b) the development and validation of an efficient metamodel; c) the global sensitivity analysis for parameter reduction; and d) the minimisation of a functional representing the discrepancy between experimental and numerical data. The results obtained by applying the proposed strategy in laboratory tests are discussed in the paper. These results confirm the accuracy of the developed approach for material parameter identification, which can be used also in combination with in-situ tests for assessing existing structures. Practical and theoretical aspects related to the proposed flat-jack test, the experimental data to be considered in the process and the post-processing methodology are critically discussed.
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, A 3D mesoscale damage-plasticity approach for masonry structures under cyclic loading, MECCANICA, Vol: 53, Pages: 1591-1611, ISSN: 0025-6455
Minga E, Macorini L, Izzuddin BA, 2018, Enhanced mesoscale partitioned modelling of heterogeneous masonry structures, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Vol: 113, Pages: 1950-1971, ISSN: 0029-5981
Tubaldi E, Macorini L, Izzuddin BA, 2018, Three-dimensional mesoscale modelling of multi-span masonry arch bridges subjected to scour, ENGINEERING STRUCTURES, Vol: 165, Pages: 486-500, ISSN: 0141-0296
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
Zhang Y, Tubaldi E, Macorini L, et al., 2018, Mesoscale partitioned modelling of masonry bridges allowing for arch-backfill interaction, CONSTRUCTION AND BUILDING MATERIALS, Vol: 173, Pages: 820-842, ISSN: 0950-0618
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
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
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