348 results found
Lou T, Wang W, Izzuddin BA, 2023, A framework for performance-based assessment in post-earthquake fire: Methodology and case study, Engineering Structures, Vol: 294, ISSN: 0141-0296
Post-earthquake fire (PEF) is a threatening hazard triggered immediately after an earthquake, resulting in extensive destruction and casualties. It is important to evaluate structural performance in this typical cascading hazard to develop mitigation strategies and improve multi-hazard resilience. However, existing research mainly focuses on the structural response in PEF scenarios, while there is still a lack of knowledge on other critical parts of performance evaluation. In contrast, there has been a well-established methodology for performance-based assessment in earthquake engineering (PBEE), which can be regarded as the basis for extension to PEF scenarios. Based on that, a comprehensive framework has been proposed in this study for performance-based assessment in post-earthquake fire engineering (PB-PEF-E). To demonstrate the feasibility of the proposed methodology, an illustrative example of a realistic multi-storey steel frame is presented with specific details. The overall procedure considering the hazard, structure, damage, and loss domains is utilised for step-by-step PEF performance evaluation. Firstly, a dual-cause PEF ignition model is used to capture the probabilistic causation among the earthquake-fire sequence, considering ignition related to utility system damage and ignitable contents overturning. Then, structural demands with respect to both earthquake and fire intensities are obtained by a series of nonlinear analyses via numerical modelling, and uncertainties that significantly influence the responses are included. Finally, the structural capacity in different performance levels is estimated with PEF fragility development, and the consequences are measured using quantitative indicators for decision-making. The proposed methodology provides important benefits in evaluating the performance of alternative solutions thus facilitating robust decision-making in PEF scenarios, and it can be further extended to performance-based assessment in other mul
Grosman S, Macorini L, Izzuddin BA, 2023, Parametric nonlinear modelling of 3D masonry arch bridges, Advances in Engineering Software, Vol: 185, Pages: 1-12, ISSN: 0965-9978
Detailed modelling of masonry arch bridges and viaducts presents unique computational challenges. Not only do such structures exhibit complex nonlinear behaviour, but they are also difficult to describe within a consistent computational framework for high-fidelity simulations, due to the range of interactive components with varying geometric characteristics. This paper presents a novel parametric model design tool for the generation of detailed 3D FE meshes of realistic masonry arch bridges and viaducts. This tool has been developed according to a modular description as an add-on component within the Rhino – Grasshopper environment. It allows for modular complex bridge assemblages with independent definition of the key viaduct parts, including arch barrels, spandrel walls, piers as well as multi-layered fill. Moreover, new parts can be seamlessly introduced into the framework due to its modular nature. Notably, as all components are geometrically addressable, it is possible to further enhance the model generation tool by adding non-standard routines to create more complex geometry than that allowed by the current parametric definition. Importantly, the developed strategy enables variable fidelity model generation, where different segments of an analysed viaduct can be represented by meso‑ and/or macro-scale masonry descriptions at different levels of detail. This approach further enables the consideration of initial damage in the brick/blockwork, which is a very common feature of many existing masonry bridges and viaducts.
Lesiv H, Izzuddin BA, 2023, Consistency and misconceptions in co-rotational 3D continuum finite elements: A zero-macrospin approach, International Journal of Solids and Structures, Vol: 281, ISSN: 0020-7683
The seminal work of Crisfield on co-rotational finite elements came to a profound conclusion that the geometric stiffness matrix of 3D continuum finite elements is inherently asymmetric, though it becomes symmetric under equilibrium conditions. Contending that these outcomes are misconceptions, this paper presents a novel zero-macrospin co-rotational approach for 3D continuum elements in which the geometric stiffness matrix is always symmetric for work-conjugate conservative loads, suggesting that Crisfield's geometric stiffness is erroneously asymmetric and inconsistent. This contention is subsequently upheld by identifying crucial terms omitted in Crisfield's formulation which are responsible for the erroneous asymmetry, and the notion that symmetry is eventually recovered at equilibrium is shown to be a further misconception. Importantly, this critical appraisal of Crisfield's formulation, which has been adopted by numerous researchers, and the delineation of its underlying misconceptions exceed academic interest to real practical relevance. Several numerical examples are presented in the paper which highlight the superiority of the proposed approach, lending incontrovertible practical evidence that the consistent geometric stiffness matrix for co-rotational 3D continuum elements is always symmetric for work-conjugate conservative loads.
Wang J, Mo YL, Izzuddin B, et al., 2023, Exact Dirichlet boundary Physics-informed Neural Network EPINN for solid mechanics, Computer Methods in Applied Mechanics and Engineering, Vol: 414, ISSN: 0045-7825
Physics-informed neural networks (PINNs) have been rapidly developed for solving partial differential equations. The Exact Dirichlet boundary condition Physics-informed Neural Network (EPINN) is proposed to achieve efficient simulation of solid mechanics problems based on the principle of least work with notably reduced training time. There are five major building features in the EPINN framework. First, for the 1D solid mechanics problem, the neural networks are formulated to exactly replicate the shape function of linear or quadratic truss elements. Second, for 2D and 3D problems, the tensor decomposition was adopted to build the solution field without the need of generating the finite element mesh of complicated structures to reduce the number of trainable weights in the PINN framework. Third, the principle of least work was adopted to formulate the loss function. Fourth, the exact Dirichlet boundary condition (i.e., displacement boundary condition) was implemented. Finally, the meshless finite difference (MFD) was adopted to calculate gradient information efficiently. By minimizing the total energy of the system, the loss function is selected to be the same as the total work of the system, which is the total strain energy minus the external work done on the Neumann boundary conditions (i.e., force boundary conditions). The exact Dirichlet boundary condition was implemented as a hard constraint compared to the soft constraint (i.e., added as additional terms in the loss function), which exactly meets the requirement of the principle of least work. The EPINN framework is implemented in the Nvidia Modulus platform and GPU-based supercomputer and has achieved notably reduced training time compared to the conventional PINN framework for solid mechanics problems. Typical numerical examples are presented. The convergence of EPINN is reported and the training time of EPINN is compared to conventional PINN architecture and finite element solvers. Compared to conventional
El Khoury K, Ridley I, Vollum R, et al., 2023, Experimental assessment of crack prediction methods in international design codes for edge restrained walls, Structures, Vol: 55, Pages: 1447-1459, ISSN: 2352-0124
Through cracking resulting from external restraint of early-age thermal and long-term shrinkage strain is a significant issue in the construction industry as it causes leakage in water retaining and resisting structures. Concerningly, a recent field study found restraint induced crack widths to frequently exceed crack widths calculated in accordance with UK design practice (BS EN 1992-3 and CIRIA C766). Due to a lack of pertinent data, the reasons for this are uncertain. This paper compares measured and predicted crack widths in a series of 12 full-scale edge restrained walls constructed in the laboratory. The tests examine the influence on cracking of key parameters including concrete mix design, wall reinforcement ratio, wall aspect ratio and relative wall to base cross-sectional area. The measured and calculated crack widths are compared at first cracking and at the end of monitoring. Two types of behaviour were noted in the tests, dependent on when the first cracks formed. Cracking either occurred at early age, within 24 h of stripping the formwork, or later due to restraint of combined early age thermal contraction and shrinkage. The final crack widths were greatest, by a considerable margin, in walls where cracks formed at early age, despite the initial cracks being very narrow. BS EN 1992-3 gives the best estimates of crack width in the two walls that cracked at early age. Crack widths in these walls were significantly underestimated by C766. In the other 10 walls, which cracked later, C766 tends to give the best estimate of crack width.
Lou T, Wang W, Izzuddin BA, 2023, System-level analysis of a self-centring moment-resisting frame under post-earthquake fire, Engineering Structures, Vol: 289, Pages: 1-17, ISSN: 0141-0296
Post-earthquake fire is a multi-hazard combination with cascading effects, of which catastrophic consequences are not only caused by the earthquake but exacerbated by the triggered fire. Only a few studies focused on the system-level structural analysis in earthquake-fire sequence, mostly on the conventional moment-resisting frame. Despite the self-centring system being a novel structure with excellent seismic performance, its post-earthquake fire response is still unclear due to limited research. Accordingly, this study aims to investigate the system-level behaviour of a self-centring system under post-earthquake fire. A numerical model of the six-storey prototype frame is established, and a two-stage bilinear material model is proposed to reflect the combined effects of pre-induced damage and temperature on material properties. A total of 11 ground motions (DBE and MCE levels) followed by 3 fires on different storeys compose the post-earthquake fire scenarios. A welded moment-resisting frame with reduced beam sections (WR-MRF) is selected for comparison, with the DBE response designed the same as the self-centring frame (SC-MRF). Results show that the SC-MRF exhibits smaller responses to the preceding earthquake and subsequent fire than the WR-MRF. Post-earthquake fire mainly affects two inter-storey drift ratios in each scenario, while it has a negligible effect on others which remain unchanged from the residual status after the earthquake. An obvious increase in structural responses can be found from fire-only (FO) to post-MCE fire (P-MCE-F) scenarios, and deformation is slightly larger in multi-floor fires than in single-floor ones. The findings unveil the post-earthquake fire responses of a seismic-resilient system with self-centring mechanism and provide a comparative assessment against the conventional structure. The methodology, including the proposed material model, can be further extended for analysis on other systems to understand and enhance the compreh
Chen Y, Izzuddin BA, 2023, A simplified finite strain plasticity model for metallic applications, Engineering with Computers: an international journal for simulation-based engineering, Pages: 1-18, ISSN: 0177-0667
In this work, a finite strain elastoplastic model is proposed within a total Lagrangian framework based on multiplicative decomposition of the deformation gradient, with several simplifications aimed at facilitating more concise code implementation and enhancing computational efficiency. Pre- and post-processors are utilised for conversion between different stress and strain measures, sandwiching the core plastic flow algorithm which preserves the small strain form. Simplifications focus on the pre- and post-processor components by substituting certain arithmetic operations associated with high computational demands with simpler ones without compromising accuracy. These modifications are based on assumptions, which are valid for most metals, that the elastic strains are small compared to plastic strains, and that the incremental plastic deformations are small for each step. In addition, the consistent tangent modulus matrix is derived in a reduced form, both for the general full model and the new simplified model, facilitating more straightforward computations in both cases. The models are verified against two classical numerical examples where favourable comparisons are achieved. Overall, the simplified model is shown to provide a significant reduction in computational demand for the two considered numerical problems, with negligible deviation in the results compared to the full model, subject to fulfilling the underlying assumptions with the adoption of a sufficiently small step size.
Chisari C, Macorini L, Izzuddin B, 2023, An anisotropic plastic‐damage model for 3D nonlinear simulation of masonry structures, International Journal for Numerical Methods in Engineering, Vol: 124, Pages: 1253-1279, ISSN: 0029-5981
Predicting the structural response of masonry structures with acceptable accuracy is paramount to safeguard the historical heritage and build new constructions with safety margins adequate to modern standards. However, due to the heterogeneous nature and anisotropic response of masonry, such prediction is still difficult to achieve, where most current masonry representations are based upon homogeneous isotropic material models or even more simplified masonry macro-elements. In this article, a novel anisotropic constitutive model to be used in detailed 3D continuum FE representations is described. This is based upon the application of the transformed-tensor method to an isotropic uncoupled plastic-damage model, which is further enhanced by additional novel features enabling the proper definition of the shear behavior both in terms of yielding surface and damage evolution while increasing local computational robustness. Illustrative examples at different scales are presented, highlighting the characteristics and potential of the developed masonry material model. Focus is placed on the mechanical behavior under uniaxial and biaxial stress states considering pure compression on wallets with varying inclination of the material principal axes and the out-of-plane response of wall components. The numerical results confirm the ability of the proposed constitutive model to predict typical masonry anisotropic response characteristics, which cannot be accurately represented by standard isotropic representations commonly used in professional practice and research.
Shehzad MK, Forth JP, Nikitas N, et al., 2023, Predicting the influence of restraint on reinforced concrete panels using finite element models developed from experimental data, Mechanics of Advanced Materials and Structures, ISSN: 1537-6494
Externally restraining volume changes of concrete, that is, thermal effects and shrinkage, may result in tensile stresses and eventually cracking. Such cracking risk is controlled/mitigated by the provision of steel reinforcement, which presumes a correct understanding of the cracking patterns under different types of restraint conditions. Reinforced concrete (RC) members may be restrained at their edges or end, or in many cases a combination of the two. Existing guidance on the subject is mostly based on end restrained members, however, it is applied to predict the behavior under edge restraint too. Researchers have identified that the mechanisms of cracking associated with edge and end restraints are quite different. To this purpose, findings from an experimental investigation aiming to understand the behavior of edge restrained RC walls were utilized to validate a finite element (FE) model. Subsequently, this FE model was used to parametrically study walls having different aspect ratios and subjected to different forms of restraint. Cracking patterns, widths, and extent appeared to greatly depend on the type of restraint and wall aspect ratio. The influence of combined restraint, for instance, was found to be more significant in walls with aspect ratio less than 4. The study provides clear evidence on why similar studies, are needed to support engineers in designing against cracking due to restraints.
Soyemi AE, Izzuddin BA, 2022, Material damage integration approach for efficient modelling of high cycle fatigue, International Journal of Solids and Structures, Vol: 262-263, Pages: 1-22, ISSN: 0020-7683
The recognition of the risk of fatigue failure and its study, particularly fatigue crack growth (FCG) behaviour of engineering materials, is not neoteric, and the majority of approaches for investigating the problem are empirical and dated. With recent computational advances, the cohesive zone modelling (CZM) approach for FCG analysis has become popular especially amongst researchers owing to its flexibility of use particularly within the finite element framework. However, the use of the CZM for explicit cycle-by-cycle high cycle FCG analysis of real structural components is still largely computationally prohibitive. Thus, this study presents a novel material integration (MI) approach to accelerate fatigue crack propagation within the cyclic cohesive zone modelling (CCZM) framework. Using a bilinear cohesive law, the proposed technique is compared with the Linear Extrapolation (LE) technique and assessed for three models of different bulk-interface element discretisation and deformations. The results show that the MI technique offers a more consistent approximation to the accelerated fatigue damage computation and, more importantly, better convergence characteristics for the different models under tension, mixed mode and bending deformations. These outcomes underline the computational benefits of the proposed MI technique in assessing the FCG behaviour of real structural components within the CCZM framework.
Pantò B, Grosman S, Macorini L, et al., 2022, A macro-modelling continuum approach with embedded discontinuities for the assessment of masonry arch bridges under earthquake loading, Engineering Structures, Vol: 269, Pages: 1-21, ISSN: 0141-0296
The paper presents a novel effective macro-modelling approach for masonry arches and bridges under cyclic loading, including dynamic actions induced by earthquakes. It utilises an anisotropic material model with embedded discontinuities to represent masonry nonlinearities. Realistic numerical simulations of masonry arch bridges under static and dynamic loading require accurate models representing the anisotropic nature of masonry and material nonlinearity due to opening and closure of tensile cracks and shear sliding along mortar joints. The proposed 3D modelling approach allows for masonry bond via simple calibration, and enables the representation of tensile cracking, crushing and shear damage in the brickwork. A two-scale representation is adopted, where 3D continuum elements at the structural scale are linked to embedded nonlinear interfaces representing the meso-structure of the material. The potential and accuracy of the proposed approach are shown in numerical examples and comparisons against physical experiments on masonry arches and bridges under cyclic static and dynamic loading.
Santos L, Izzuddin BA, Macorini L, 2022, Gradient-based optimisation of rectangular honeycomb core sandwich panels, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, Vol: 65, ISSN: 1615-147X
El Ashri M, Grosman S, Macorini L, et al., 2022, Numerical Investigation of the 3D Response of Masonry Skew Arches and Bridges, Fourteenth International Conference on Computational Structures Technology, ISSN: 2753-3239
Soyemi A, Grosman S, Macorini L, et al., 2022, Numerical Modelling of Brick-mortar Masonry Structures under Fatigue Loading, Fourteenth International Conference on Computational Structures Technology, ISSN: 2753-3239
Pantò B, Chisari C, Macorini L, et al., 2022, A hybrid macro-modelling strategy with multi-objective calibration for accurate simulation of multi-ring masonry arches and bridges, Computers & Structures, Vol: 265, ISSN: 0045-7949
This paper presents an efficient hybrid continuum-discrete macro-modelling strategy with an enhanced multiscale calibration procedure for realistic simulations of brick/block-masonry bridges. The response of these structures is affected by the intrinsic nonlinearity of the masonry material, which in turn depends upon the mechanical properties of units and mortar joints and the bond characteristics. Finite element approaches based upon homogenised representations are widely employed to assess the nonlinear behaviour up to collapse, as they are generally associated with a limited computational demand. However, such models require an accurate calibration of model material parameters to properly allow for masonry bond. According to the proposed approach, the macroscale material parameters are determined by an advanced multi-objective strategy with genetic algorithms from the results of mesoscale “virtual” tests through the minimisation of appropriate functionals of the scale transition error. The developed continuum-discrete finite element macroscale description and the calibration procedure are applied to simulate the nonlinear behaviour up to collapse of multi-ring arch-bridge specimens focusing on the 2D planar response. The results obtained are compared to those achieved using detailed mesoscale models confirming the effectiveness and accuracy of the proposed approach for realistic nonlinear simulations of masonry arch bridges.
Riedel K, Vollum R, Vella JP, et al., 2022, Experimental testing of a novel D-Frame connection under sudden column removal, fib International Congress 2022 Oslo
Elwakeel A, Shehzad M, El Khoury K, et al., 2022, INDUCED CRACKING IN EDGE RESTRAINED WALLS – FEA PARAMETRIC STUDY, fib International Congress 2022
Ridley I, Shehzad M, Forth J, et al., 2022, Experimental assessment of crack width estimations in international design codes, SEMC 2022 International Conference: http://www.semc.uct.ac.za
Riedel K, Vollum R, Izzuddin B, et al., 2022, Design of precast concrete framing systems against disproportionate collapse using component-based methods, SEMC 2022 International Conference: http://www.semc.uct.ac.za
Liang Y, Izzuddin BA, 2022, Locking-free 6-noded triangular shell elements based on hierarchic optimisation, FINITE ELEMENTS IN ANALYSIS AND DESIGN, Vol: 204, ISSN: 0168-874X
Izzuddin BA, 2022, Rational Robustness Design of Multistory Building Structures, JOURNAL OF STRUCTURAL ENGINEERING, Vol: 148, ISSN: 0733-9445
Panto B, Macorini L, Izzuddin BA, 2022, A two-level macroscale continuum description with embedded discontinuities for nonlinear analysis of brick/block masonry, Computational Mechanics, Vol: 69, Pages: 865-890, ISSN: 0178-7675
A great proportion of the existing architectural heritage, including historical and monumental constructions, is made of brick/block masonry. This material shows a strong anisotropic behaviour resulting from the specific arrangement of units and mortar joints, which renders the accurate imulation of the masonry response a complex task. In general, mesoscale modelling approaches provide realistic predictions due to the explicit representation of the masonry bond characteristics. However, these detailed models are very computationally demanding and mostly unsuitable for practical assessment of large structures. Macroscale models are more efficient, but they require complex calibration procedures to evaluate model material parameters. This paper presents an advanced continuum macroscale model based on a two-scale nonlinear description for masonry material which requires only simple calibration at structural scale. A continuum strain field is considered at the macroscale level, while a 3D distribution of embedded internal layers allows for the anisotropic mesoscale features at the local level. A damage-plasticity constitutive model is employed to mechanically characterise each internal layer using different material properties along the two main directions on the plane of the masonry panel and along its thickness. The accuracy of the proposed acroscale model is assessed considering the response of structural walls previously tested under in-plane and out-of-plane loading and modelled using the more refined mesoscale strategy. The results achieved confirm the significant potential and the ability of the proposed macroscale description for brick/block masonry to provide accurate and efficient response predictions under different monotonic and cyclic loading conditions.
Martinelli P, Izzuddin BA, 2022, Validation and application of rational tying method for robustness design of post-and-beam timber buildings, WOOD MATERIAL SCIENCE & ENGINEERING, ISSN: 1748-0272
Elwakeel A, Shehzad M, El Khoury K, et al., 2022, Assessment of cracking performance in edge restrained RC walls, STRUCTURAL CONCRETE, Vol: 23, Pages: 1333-1352, ISSN: 1464-4177
Nordas AN, Izzuddin BA, 2022, Translational surface coupling along a line with non-conforming meshes, Computers & Structures, Vol: 260, Pages: 1-27, ISSN: 0045-7949
In the modelling of large-scale metal structures, comprising plated components intersecting along weld lines, the meshing efficiency and flexibility are limited by the requirements of nodal alignment and compliance of element size, shape and edge orientation throughout the domain. Such limitations necessitate the use of complex transitional meshes in intersection regions and result in highly complex global mesh configurations. This paper presents an original and systematic methodology for surface coupling along an arbitrary 1D interface, which is applicable to any type of 2D and 3D FEs, and which provides a systematic framework for: (i) geometric modelling of weld lines; (ii) coupling of regions with different levels of discretisation detail or element types within a system; and (iii) domain partitioning problems involving computationally heterogeneous partitions. The strategy is based upon a novel coupling element formulation, which uses the fundamental principles of the mortar method and an augmented Lagrangian Multiplier optimisation approach. Particular consideration is given to an element formulation that enforces rigid translational coupling, which has been implemented for employment with co-rotational Reissner-Mindlin shell elements. Various numerical examples are presented to demonstrate the accuracy, versatility and substantial computational benefits of the developed methodology for modelling large-scale metal structural systems.
Izzuddin BA, Sio J, 2022, Rational horizontal tying force method for practical robustness design of building structures, Engineering Structures, Vol: 252, Pages: 1-18, ISSN: 0141-0296
This paper presents a rational method for the horizontal tying of multi-storey building structures aimed at robustness design and the mitigation of progressive collapse. Unlike current prescriptive tying force approaches, the new method benefits from i) a rational association with local damage scenarios consisting of the sudden loss of a column or a load-bearing wall, ii) the explicit consideration of the system ductility limit and dynamic amplification, iii) the systematic combination of various types of loading and sources of tying, and iv) supplementary methods for assessing the interaction of the affected floor system with the surrounding structure. Importantly, these relative benefits are still realised within a practical application framework that is comparable in simplicity to prescriptive tying rules, making the proposed tying method suitable for codification and as a replacement for prescriptive tying force requirements in the next generation of robustness design codes. Following a detailed exposition of the method formulation and parameters, the paper presents several studies which demonstrate the effectiveness of the proposed tying force method, concluding with an example that illustrates its application to a typical reinforced concrete floor system.
Setiawan A, Vollum R, Macorini L, et al., 2021, Numerical modelling of punching shear failure of RC flat slabs with shear reinforcement, Magazine of Concrete Research, Vol: 73, Pages: 1205-1224, ISSN: 0024-9831
This paper utilises non-linear finite-element analysis with three-dimensional (3D) solid elements to gain insight into the role of shear reinforcement in increasing punching shear resistance at internal columns of flat slabs. The solid element analysis correctly captures the experimentally observed gradual decrease in concrete contribution to shear resistance with increasing slab rotation and the failure mode but is very computationally demanding. As an alternative, the paper presents a novel approach, in which 3D joint elements are combined with non-linear shell elements. Punching failure is modelled with joint elements positioned around a control perimeter located at 0.5d from the column face (where d is the slab effective depth). The joint elements connect the nodes of shell elements located to either side of the punching control perimeter. The punching resistance of the joints is related to the slab rotation using the failure criterion of the critical shear crack theory. The joint-shell punching model (JSPM) considers punching failure both within the shear-reinforced region and due to crushing of concrete struts near the support region. The JSPM is shown to accurately predict punching resistance while requiring significantly less computation time than 3D solid element modelling.
Ravasini S, Sio J, Franceschini L, et al., 2021, Validation of simplified tying force method for robustness assessment of RC framed structures, Engineering Structures, Vol: 249, Pages: 1-16, ISSN: 0141-0296
The robustness of reinforced concrete (RC) structures is an important ongoing research topic in the civil engineering community. Especially in the last decades, the need for structural robustness assessment methods has become urgent, and several design methods have been proposed in codes and guidelines to mitigate the progressive collapse risk of reinforced concrete structures. The most used approaches are the Tying Force and Alternate Load Path methods. The first is typically applied as an indirect and prescriptive method where the building is considered mechanically tied together and able to enhance continuity and the resistance to progressive collapse. The second is a direct method, where the capacity of the structure to sustain the applied loads is evaluated after the loss of a load-bearing element, most effectively using advanced nonlinear structural analysis methods. In the context of the Tying Force method, the Eurocode is recognised to underestimate the tie force demands required by building structures subject to the loss of a load bearing member, which are better reflected in the USA UFC Guidelines. A new Tying Force method has been proposed by Izzuddin & Sio (2021) for the next generation of the Eurocodes, which addresses the shortcomings of the present Eurocode guidance, and provides a more comprehensive treatment than considered in the UFC code. The present paper is aimed specifically at the validation of the new Simplified Tying Force method (Izzuddin & Sio, 2021) for reinforced concrete structures, considering grillage and combined beam/slab floor systems, and considering the rotational ductility of such structures, which is explicitly considered in the new method.
Li Z, Ji J, Vu-Quoc L, et al., 2021, A 3-node co-rotational triangular finite element for non-smooth, folded and multi-shell laminated composite structures, Computer Modeling in Engineering & Sciences, Vol: 129, Pages: 485-518, ISSN: 1526-1506
Based on the first-order shear deformation theory, a 3-node co-rotational triangular finite element formulation is developed for large deformation modeling of non-smooth, folded and multi-shell laminated composite structures. The two smaller components of the mid-surface normal vector of shell at a node are defined as nodal rotational variables in the co-rotational local coordinate system. In the global coordinate system, two smaller components of one vector, together with the smallest or second smallest component of another vector, of an orthogonal triad at a node on a non-smooth intersection of plates and/or shells are defined as rotational variables, whereas the two smaller components of the mid-surface normal vector at a node on the smooth part of the plate or shell (away from non-smooth intersections) are defined as rotational variables. All these vectorial rotational variables can be updated in an additive manner during an incremental solution procedure, and thus improve the computational efficiency in the nonlinear solution of these composite shell structures. Due to the commutativity of all nodal variables in calculating of the second derivatives of the local nodal variables with respect to global nodal variables, and the second derivatives of the strain energy functional with respect to local nodal variables, symmetric tangent stiffness matrices in local and global coordinate systems are obtained. To overcome shear locking, the assumed transverse shear strains obtained from the line-integration approach are employed. The reliability and computational accuracy of the present 3-node triangular shell finite element are verified through modeling two patch tests, several smooth and non-smooth laminated composite shells undergoing large displacements and large rotations.
Plavsic A, Panto B, Chisari C, et al., 2021, Nonlinear simulation of masonry vaults under earthquake loading, CompDyn 2021, Publisher: Institute of Structural Analysis and Antiseismic ResearchSchool of Civil Engineering, Pages: 595-606
Masonry vaults are present in a large number of historical structures and often used as floor-ing and roofing systems in monumental palaces and religious buildings, typically incorporat-ing no backfill. Many of these structures are located in seismic regions and have been shownto be particularly vulnerable during recent earthquakes, with a need for accurate modelling to avoid future losses. Masonry vaults are often analysed using limit analysis procedures un-der the hypotheses of no-tension material and absence of sliding along the masonry joints.However, this method can be inaccurate for barrel vaults found in buildings, which are typi-cally slender with no backfill. In this case, the masonry tensile strength and the progressive damage propagation play an important role in the nonlinear behaviour and ultimate strength of the vault. In this study, a detailed mesoscale finite element mesoscale approach is used to model slender unreinforced barrel vaults subjected to cyclic quasi-static and dynamic load-ing. According to this approach, 3D solid elements connected by 2D damage-plasticity inter-faces are used to represent the arrangement of bricks and mortar present in the masonry. Theproposed numerical description is first validated against the results from physical tests on a barrel vault under quasi-static cyclic loading. Subsequently, the shear response of a prototype vault is analysed by performing nonlinear simulations under prescribed horizontal displace-ments at the supports, considering also the influence of previous damage induced by earth-quakes with different magnitudes.
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