145 results found
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.
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
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
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
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.
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.
Abu-Salma D, Vollum R, Macorini L, 2021, Design of biaxially loaded external slab column connections, Engineering Structures, Vol: 249, Pages: 1-16, ISSN: 0141-0296
The paper investigates the influence of biaxial loading on punching resistance at square and elongated edge columns of flat slabs which is virtually neglected in the literature. In the absence of experimental data, the influence of biaxial loading is determined using nonlinear finite element analysis (NLFEA) with 3D solid elements. The resulting baseline punching resistances are compared with the predictions of various implementations of the Critical Shear Crack Theory (CSCT) including a Joint Shell Punching Model (JSPME) in which punching failure is simulated using nonlinear joint elements inserted between the nodes of nonlinear shell elements located around the punching control perimeter. The failure criterion of the JSPME, which is most suited for structural assessment, implicitly accounts for the effect of biaxial loading unlike the original (classic) and closed form versions of the CSCT. The classic CSCT indirectly accounts for loading eccentricity by reducing the punching control perimeter by a multiple ke which is determined in this paper using shear field analysis. Conversely, the closed form CSCT, which is adopted in the draft for the next generation of Eurocode 2 (EC2), enhances the design shear force by a multiple β. The paper uses experimental data to determine an expression for β for edge column connections subject to inwards eccentricity normal to the slab edge. Subsequently, shear field analysis on representative flat slab to edge column connections is used to extend this expression for β to edge column connections subject to biaxial eccentricity. NLFEA simulations with 3D solid elements are used to validate the predictions of the JSPME, the shear field methodology used to determine ke in the classic CSCT and the proposed expression for β in the closed form CSCT. Reasonable agreement is achieved between all these analysis methods. The main advantage of the JSPME over NLFEA with 3D solid elements is its increased computational effic
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.
Abu-Salma D, Vollum RL, Macorini L, 2021, Modelling punching shear failure at edge slab-column connections by means of nonlinear joint elements, Structures, Vol: 34, Pages: 630-652, ISSN: 2352-0124
This paper is concerned with the modelling of punching shear failure at edge columns of flat slabs without shear reinforcement. Punching failure at edge columns is much less researched than at interior columns despite typical buildings having more edge than interior columns. The paper uses nonlinear finite element analysis (NLFEA) to study the influence on punching resistance of parameters including column aspect ratio and loading eccentricity. The NLFEA is carried out using both 3D solid elements and a Joint Shell Punching Model (JSPM) which combines nonlinear shell elements with nonlinear joint elements that incorporate the failure criterion of the Critical Shear Crack Theory (CSCT). Both constant and varying loading eccentricities are investigated since near failure eccentricity at edge column connections typically reduces below that calculated with elastic analysis due to moment being redistributed from the support to span. This reduction in eccentricity is beneficial since punching resistance is shown to depend on the final loading eccentricity. Consequently, designing for punching on the basis of elastic edge column moments is overly conservative.
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.
Panto B, Chisari C, Macorini L, et al., 2021, A macroscale modelling approach for nonlinear analysis of masonry arch bridges, SAHC 2020/2021, Publisher: International Centre for NumericalMethods in Engineering (CIMNE), Pages: 1724-1735
Masonry arches represent the most important structural components of masonry arch bridges. Their response is strongly affected by material nonlinearity which is associated with the masonry texture. For this reason, the use of mesoscale models, where units and mortar joints are individually represented, enables accurate response predictions under different loading conditions. However, these detailed models can be very computationally demanding and unsuitable for practical assessments of large structures. In this regard, the use of macro-models, based on simplified homogenised continuum representations for masonry, can be preferable as it leads to a drastic reduction of the computational burden. On the other hand, the latter modelling approach requires accurate calibration of the model parameters to correctly allow for masonry bond. In the present paper, a simplified macro-modelling strategy, particularly suitable for nonlinear analysis of multi-ring brick-masonry arches, is proposed and validated. A numerical calibration procedure, based on genetic algorithms, is used to evaluate the macro-model parameters from the results of meso-scale “virtual” tests. The proposed macroscale description and the calibration procedure are applied to simulate the nonlinear behaviour up to collapse of two multi-ring arches previously tested in laboratory and then to predict the response of masonry arches interacting with backfill material. The numerical results confirm the ability of the proposed modelling strategy for masonry arches to predict the actual nonlinear response and complex failure mechanisms, also induced by ring separation, with a reduced computational cost compared to detailed mesoscale models.
Grosman S, Bilbao AB, Macorini L, et al., 2021, Numerical modelling of three-dimensional masonry arch bridge structures, Proceedings of the Institution of Civil Engineers - Engineering and Computational Mechanics, Vol: 174, Pages: 96-113, ISSN: 1755-0777
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 2D descriptions for masonry bridges, do not enable an accurate representation of the typical 3D response, and often they do not provide realistic predictions of the development of damage in the various bridge components including arches, piers and spandrel walls. In this paper, two alternative 3D FE modelling strategies offering different balance between sophistication and computational efficiency are presented. The first approach is based upon a detailed mesoscale masonry model, where a distinction is made between constituents allowing for an accurate description of masonry under various bond conditions. Alongside elastic solid elements representing the bricks, nonlinear interface elements are used to model the mortar joints and the potential cracks across the brick bulk. The second approach is based on macroscale representation, where a homogeneous description of masonry is assumed employing elasto-plastic solid elements with damage to represent the masonry components of arch bridges. In both approaches, backfill is modelled by elasto-platic solid elements and the interactions between the spandrel walls and the backfill and arches, as well as between the backfill and the arches’ extrados, are explicitly incorporated to 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.
Abu-Salma D, Vollum R, Macorini L, 2021, Punching shear in edge slab-column connections, fib Symposium Lisbon, ISSN: 2617-4820
Chisari C, Macorini L, Izzuddin B, et al., 2021, Analysis of the stress and deformation states in the vertical flat jack test, International Journal of Masonry Research and Innovation, Vol: 6, Pages: 21-44, ISSN: 2056-9459
Performing a realistic assessment of unreinforced masonry structures involves designing and executing appropriate experimental tests on masonrycomponentsfor determining the material model parameters to be used in structural analysis. Consideringrecent developmentsin which inverse analysis was used as calibration framework, a vertical flat-jack testis investigated in this paper. Two simplified models are describedfor the analysisof the stress state in the masonry due to the pressure transferred by the flat-jack. Furthermore, with the aim of designing the sensor setup for the test, aPOD analysis on the deformation state of the structure is carried out, highlighting the basic deformation modes which govern the response. The results show that high stresses and local modes can occur in the proximity of the flat-jack,and thus local use of FRP reinforcement is recommended to avoid undesired brittle crack propagationwhich may prevent accurate calibration of mortar joint mechanical characteristics.
Tubaldi E, Minga E, Macorini L, et al., 2020, Mesoscale analysis of multi-span masonry arch bridges, Engineering Structures, Vol: 225, Pages: 1-16, ISSN: 0141-0296
Masonry arch bridges often include multiple spans, where adjacent arches and piers interact with each other giving rise to a complex response under traffic loading. Thus, the assumption commonly used in practical assessment that multi-span masonry viaducts behave as a series of independent single-span structures, may not be realistic for many configurations. While several experimental and numerical studies have been conducted to investigate single-span masonry arches and bridges,only limited research has been devoted to the analysis of the response of multi-span masonry bridges. This study investigates numerically masonry arch bridges with multiple spans subjected to vertical loading. For this purpose, an advanced finite element description,which is based upon a mesoscale representation for masonry and accounts for both material and geometric nonlinearities, is employed to shed some light on the actual behaviour of these structural systems. A validation study is first carried out to confirm that the adopted modelling strategy is capable to accurately simulate previous experimental results.Then, the influence of some critical geometrical and mechanical parameters that affect the bridge response is evaluated through a parametric study.The effects of pier settlements and brickwork defects are also investigated, as well as the interaction between adjacent spans through comparisons against the response of single-span counterparts.
Chisari C, Macorini L, Izzuddin B, 2020, Mesoscale modelling of a masonry building subjected to earthquake loading, Journal of Structural Engineering, Vol: 147, Pages: 04020294-1-04020294-14, ISSN: 0733-9445
Masonry structures constitute an important part of the built environment and architectural heritage in seismic areas. A large number of these old structures showed inadequate performance and suffered substantial damage under past earthquakes. Realistic numerical models are required for accurate response predictions and for addressing the implementation of effective strengthening solutions. A comprehensive mesoscale modeling strategy explicitly allowing for masonry bond is presented in this paper. It is based on advanced nonlinear material models for interface elements simulating cracks in mortar joints and brick/block units under cyclic loading. Moreover, domain decomposition and mesh tying techniques are used to enhance computational efficiency in detailed nonlinear simulations. The potential of this approach is shown with reference to a case study of a full-scale unreinforced masonry building previously tested in laboratory under pseudodynamic loading. The results obtained confirm that the proposed modeling strategy for brick/block-masonry structures leads to accurate representations of the seismic response of three-dimensional (3D) building structures, both at the local and global levels. The numerical-experimental comparisons show that this detailed modeling approach enables remarkably accurate predictions of the actual dynamic characteristics, along with the main resisting mechanisms and crack patterns.
Minga E, Macorini L, Izzuddin B, et al., 2020, 3D macroelement approach for nonlinear FE analysis of URM components subjected to in-plane and out-of-plane cyclic loading, Engineering Structures, Vol: 220, Pages: 1-22, ISSN: 0141-0296
The paper presents a novel 3D macroelement approach for efficient and accurate nonlinear analysis of unreinforced masonry components subjected to in-plane and out-of-plane cyclic loading. A macroscopic description for masonry is employed, where macroelements, consisting of deformable blocks interacting through cohesive interfaces, are used to represent large portions of masonry walls, enhancing computational efficiency. Enriched kinematic characteristics are adopted for the homogeneous blocks, where in-plane shear and out-of-planebending modes are described by two independent Lagrangian parameters. Moreover, a detailed material model for the nonlinear interfaces connecting adjacent elements enables an accurate representation of complex failure modes and cracking patterns in masonry walls. As a result, the proposed FE strategy can be employed for accurate response predictions of large masonry structures subjected to cyclic loading conditions. The accuracy of the macroelement approach is validated through comparisons against results of experimental tests of solid and perforated masonry walls under in-plane and out-of-plane loading.
Setiawan A, Vollum RL, Macorini L, et al., 2020, Punching of RC slabs without transverse reinforcement supported on elongated columns, Structures, Vol: 27, Pages: 2048-2068, ISSN: 2352-0124
The paper investigates the influence of support elongation on punching resistance at internal slab column connections without shear reinforcement. Nonlinear finite element analysis (NLFEA) with 3-D solid elements is used to study the influence of column elongation on stress and strain in the slab around the column. Punching failure is shown to be triggered by localised peaks in shear stress around the corners of the support. Significantly, one-way shear is shown to increase the shear resistance of slabs supported on columns with cross sectional dimensions greater than around six times the slab effective depth (d). The common laboratory practice of supporting slabs in punching tests on elongated plates rather than columns is investigated numerically and is found to be reasonable despite uplift occurring in the central region of elongated plates. NLFEA with solid elements gives useful insights into punching failure but nonlinear shell elements are better suited to the practical assessment of slabs in building structures. The disadvantage of conventional nonlinear shell elements is that shear failure can only be detected through post processing of results. To circumvent this, the authors have previously developed a novel modelling approach in which 3-D joint elements are used to connect shell elements located to either side of a punching control perimeter positioned at 0.5 from the column face. The joint shear resistance is calculated using the Critical Shear Crack Theory (CSCT) in which punching resistance is related to slab rotation. Based on insights gained using the solid element modelling, this paper extends the use of the joint model to the modelling of punching failure at elongated supports by including one-way joints to model linear shear.
Abu-Salma D, Vollum R, Macorini L, 2020, Punching Shear at Slab-Edge Column Connections, 13th fib International PhD-Symposium in Civil Engineering
Setiawan A, Vollum RL, Macorini L, et al., 2020, Punching shear design of RC flat slabs supported on wall corners, Structural Concrete, Vol: 21, Pages: 859-874, ISSN: 1464-4177
Reinforced concrete buildings are typically braced with shear walls positioned around lift shafts and stairs. Vertical transfer of load from slab to walls leads to a concentration of shear stress in the slab at wall ends and corners, which needs to be considered in punching shear design. This issue is not addressed in EN 1992 (2004) and only partially addressed in fib Model Code 2010 leaving engineers to resort to their own judgment. Consequently, consideration of punching shear at wall corners can be overlooked entirely or not properly addressed through lack of knowledge. The paper addresses this issue by proposing a method for calculating the design shear stress at wall corners for use in conjunction with the Critical Shear Crack Theory. The method is initially validated against test results for slabs supported on elongated columns as well as numerical simulations. Subsequently, the method is extended to the punching design of a slab supported by a wall corner. The proposed analysis of the slab‐wall corner junction is validated against the predictions of nonlinear finite element analysis (NLFEA) employing 3‐D solid elements as well as the joint‐shell punching model (JSPM) previously developed by the authors.
Fieber A, Gardner L, Macorini L, 2020, Structural steel design using second-order inelastic analysis with strain limits, Journal of Constructional Steel Research, Vol: 168, Pages: 1-19, ISSN: 0143-974X
Steel framed structures are affected, to greater or lesser extent, by (i) geometrical nonlinearity associated with the change in geometry of the structure under load and (ii) material nonlinearity related to the onset and spread of plasticity. In traditional design approaches, the design forces and moments within structural members are usually determined from simplified structural analyses (e.g. first or second-order elastic analysis), after which member design checks are performed to assess the strength and stability of the individual members. The extent to which the strength and deformation capacity of cross-sections is affected by local buckling is typically assessed through the concept of cross-section classification. For example, only compact (Class 1) cross-sections are considered to possess sufficient rotation capacity for plastic hinges to develop and for inelastic analysis methods to be used. This approach results in step-wise capacity predictions and is considered to be overly simplistic. Since the structural analysis of steel framed structures is typically performed using beam finite elements, which are unable to explicitly capture local buckling, a more sophisticated treatment of the available deformation capacity is required if inelastic analysis methods are to be used for all cross-section classes. A novel method of design by advanced inelastic analysis has recently been developed (Gardner et al., 2019a; Fieber et al., 2019a, 2018a, 2018b [, , , ]), in which strain limits are employed to represent the effects of local buckling in beam finite element models and thereby control the spread of plasticity and level of force/moment redistribution within a structure. It is thus possible to use a consistent advanced analysis framework to design structures composed of cross-sections of any class. In the present paper, application of the proposed design method to continuous beams and planar frames is illustrated and assessed. Ultimate load capacity p
Chisari C, Macorini L, Izzuddin B, 2020, Multiscale model calibration by inverse analysis for nonlinear simulation of masonry structures under earthquake loading, International Journal for Multiscale Computational Engineering, Vol: 18, Pages: 241-263, ISSN: 1543-1649
The prediction of the structural response of masonry structures under extreme loading conditions, including earthquakes,requiresthe use of advanced material descriptionsto represent the nonlinear behaviour of masonry. In general, micro-and mesoscale approaches are very computationally demanding, thus at present they are used mainly for detailed analysis of small masonry components. Conversely macroscale models, where masonry is assumed as a homogeneous material, aremore efficient and suitable for nonlinear analysis of realistic masonry structures. However, the calibration of the material parameters for such models, which is generally basedon physical testing of entire masonry components, remains an open issue. In this paper, a multiscale approach is proposed, in which an accuratemesoscale modelaccounting for the specific masonry bond is utilised invirtual tests for the calibration of a more efficient macroscale representation assumingenergy equivalence between the two scales. Since the calibration is performed offlineat the beginning of the analysis, the method is computationally attractive compared to alternativehomogenisation techniques. The proposed methodologyis applied to a case study consideringthe results obtained in previous experimental testson masonry components subjected to cyclic loading, and on a masonry building under pseudo-dynamic conditions representingearthquake loading.The results confirmthepotential of the proposedapproach and highlight somecritical issues, such asthe importance of selecting appropriatevirtual tests for model calibration,which can significantlyinfluence accuracy and robustness.
Abu-Salma D, Vollum R, Macorini L, 2020, Punching shear at slab-edge column connections, Pages: 216-223, ISSN: 2617-4820
This paper is concerned with modelling punching shear failure at edge columns of flat slabs. Punching failure at edge columns is much less researched than at interior columns despite typical buildings having more edge than interior columns. The paper uses nonlinear finite element analysis (NLFEA) to study the influence of column aspect ratio and loading eccentricity on punching resistance at edge columns subject to inwards eccentricity. The analysis is carried out using 3D solid elements as well as a Joint Shell Punching Model (JSPM) in which nonlinear joint elements are combined with nonlinear shell elements. The JSPM uses joint elements incorporating the Critical Shear Crack Theory (CSCT) failure criterion to model punching failure. The joint elements are placed around the punching shear control perimeter which is located at 0.5d from the column face where d is the slab effective depth. The paper focusses on the analysis of punching shear at elongated columns orientated with the long side normal to the slab edge. This column arrangement is commonly used in residential buildings since it enables the column to be hidden within partition walls. Shear stress around the control perimeter is shown to concentrate towards the ends of elongated columns placed normal to the slab edge. Strength predictions obtained with the JSPM are shown to compare favourably with laboratory tests and numerical studies carried out with NLFEA with 3D solid elements.
Occhipinti G, Izzuddin B, Macorini L, et al., 2020, Realistic seismic assessment of RC buildings with masonry infills using 3D high-fidelity simulations, Pages: 1234-1245
This paper presents a high fidelity nonlinear modelling strategy for accurate response predictions of reinforced concrete (RC) framed buildings subjected to earthquakes. The proposed numerical approach is employed to investigate the seismic performance of a 10-storey building, which is representative of many existing RC structures designed with no consideration of earthquake loading by following design strategies typically used in Italy before the introduction of the first seismic regulations. The seismic response of the representative building is investigated through detailed nonlinear dynamic simulations using ADAPTIC, an advanced finite element code for nonlinear analysis of structures under extreme loading. The analysed structure is described by 3D models, where beam-column and shell elements, both allowing for geometric and material nonlinearity, are employed to represent RC beams, columns and floor slabs respectively. Furthermore, in order to model the influence of non-structural components interacting with the main frame elements, masonry infill panels are described using a novel 2D discrete macro-element representation, which has been purposely developed within a FE framework and implemented in ADAPTIC. The nonlinear dynamic simulations are performed considering sets of natural accelerograms acting simultaneously along the two main horizontal and the vertical directions and compatible with the design spectrum for the Near Collapse Limit State (NCLS). To improve computational efficiency, which is critical when investigating the nonlinear dynamic response of large structures, a partitioning approach, previously developed at Imperial College, has been adopted. The numerical results, obtained from the accurate 3D nonlinear dynamic simulations, have shown an extremely poor seismic performance of the building, for which collapse is predicted for seismic events characterized by lower magnitude compared to the expected more catastrophic earthquake. The comparison of
Abu-Salma D, Vollum R, Macorini L, et al., 2020, Punching shear at slab-edge column connections, Pages: 622-630
This paper is concerned with punching shear design at edge column connections of flat slabs. Significantly, punching failure is much less researched at edge columns of flat slabs than at interior connections despite typical buildings having more edge than interior columns. In both cases, punching failure is undesirable since it can result in progressive collapse owing to load being redistributed from the failing connection to the surrounding connections. The paper considers the influence of eccentricity of loading and column aspect ratio on punching shear resistance at edge columns. Finite element analysis (FEA) shows that shear stress in the slab is concentrated towards the ends of elongated columns which are commonly found in residential buildings. This problem has not been widely researched either experimentally or numerically. Elastic shear field analysis is used to study the influence of column aspect ratio and loading eccentricity on the shear stress distribution around a punching control perimeter positioned at 0.5d from the column face where d is the slab effective depth. Comparisons are made with shear stress distributions obtained with nonlinear finite element analysis (NLFEA) using 3D-solid elements as well as linear and nonlinear shell elements. The NLFEA with solid elements is initially calibrated using experimental data. Subsequently, it is used to carry out parametric studies which consider the effect of varying: 1) the column cross-section dimensions and 2) loading eccentricity. The results of the NLFEA are used to assess two alternative methods for calculating punching shear resistance at edge columns using the Critical Shear Crack Theory (CSCT). The paper presents a refined method based on shear field analysis for calculating the punching shear resistance of flat slabs supported on elongated edge columns.
Fieber AC, Gardner L, Macorini L, 2020, Advanced analysis with strain limits for the design of steel structures
Structural analysis of steel frames is typically performed using beam finite elements. These elements cannot capture local buckling explicitly and hence limitations on the local strength and rotation capacity of members are required for design purposes. Traditionally, this is achieved by classifying cross-sections and defining class-specific restrictions on the analysis type (i.e. elastic or plastic design) and cross-section design resistance (i.e. plastic, elastic or effective bending capacity). This approach is however considered to be overly simplistic and creates artificial 'steps' in the capacity predictions of structural systems. A more consistent approach is proposed herein, whereby a second order global plastic analysis is performed with strain limits accounting for the effects of local buckling and controlling the deformation capacity of each cross-section. The strain limits are obtained from the Continuous Strength Method. Strains are averaged over a characteristic length to exploit the beneficial effects of moment gradients. The proposed method is applied to members, continuous beams and frames and is shown to be more consistent and user-friendly than current structural steel design methods.
Demirci C, Malaga Chuquitaype C, Macorini L, 2019, Seismic shear and acceleration demands in multi-storey cross-laminated timber buildings, Engineering Structures, Vol: 198, ISSN: 0141-0296
A realistic estimation of seismic shear demands is essential for the design and assessment of multi-storey buildings and for ensuring the activation of ductile failure modes during strong ground-motion. Likewise, the evaluation of seismic floor accelerations is fundamental to the appraisal of damage to non-structural elements and building contents. Given the relative novelty of tall timber buildings and their increasing popularity, a rigorous evaluation of their shear and acceleration demands is all the more critical and timely. For this purpose, this paper investigates the scaling of seismic shear and acceleration demands in multi- storey cross-laminated timber (CLT) buildings and its dependency on various structural properties. Special attention is given to the influence of the frequency content of the ground-motion. A set of 60 CLT buildings of varying heights representative of a wide range of structural configurations is subjected to a large dataset of 1656 real earthquake records. It is demonstrated that the mean period (Tm) of the ground-motion together with salient structural parameters such as building aspect ratio (λ), design force reduction factor (q) and panel subdivision (β) influence strongly the variation of base shear, storey shears and acceleration demands. Besides, robust regression models are used to assess and quantify the distribution of force and acceleration demands on CLT buildings. Finally, practical expressions for the estimation of base shears, inter-storey shears and peak floor accelerations are offered.
Fieber A, Gardner L, Macorini L, 2019, Design of structural steel members by advanced inelastic analysis with strain limits, Engineering Structures, Vol: 199, Pages: 1-21, ISSN: 0141-0296
Structural steel design is traditionally a two step process: first, the internal forces and moments in the structure are determined from a structural analysis. Then, a series of design checks are carried out to assess the strength and stability of individual members. The structural analysis is typically performed using beam finite elements, which are usually not able to capture local buckling explicitly. Instead, the assessment of local buckling and rotation capacity is made through the concept of cross-section classification, which places class-specific restrictions on the analysis type (i.e. plastic or elastic) and defines the cross-section resistance based on idealised stress distributions (e.g. the plastic, elastic or effective moment capacity in bending). This approach is however considered to be overly simplistic and creates artificial steps in the capacity predictions of structural members. A more consistent approach is proposed herein, whereby a second-order inelastic analysis of the structure or structural component is performed using beam finite elements, and strain limits are employed to mimic the effects of local buckling, control the spread of plasticity and ultimately define the structural resistance. The strain limits are obtained from the continuous strength method. It is shown that not only can local buckling be accurately represented in members experiencing uniform cross-sectional deformations along the length, but, by applying the strain limits to strains that are averaged over a defined characteristic length, the beneficial effects of local moment gradients can also be exploited. The proposed method is assessed against benchmark shell finite element results on isolated members subjected to bending, compression and combined loading. Compared to conventional steel design provisions and even to existing advanced design approaches utilising second-order elastic analysis, the proposed design approach provides consistently more accurate capacity predic
Setiawan A, Vollum R, Macorini L, et al., 2019, Efficient 3D modelling of punching shear failure at slab-column connections by means of nonlinear joint elements, Engineering Structures, Vol: 197, Pages: 1-19, ISSN: 0141-0296
Failures of isolated slab-column connections can be classified as either flexural or punching. Flexural failure is typically preceded by large deformation, owing to flexural reinforcement yield, unlike punching failure which occurs suddenly with little if any warning. This paper proposes a novel numerical strategy for modelling punching failure in which nonlinear joint elements are combined with nonlinear reinforced concrete (RC) shell elements. The joint elements are employed to model punching failure which limits force transfer from slabs to supporting columns. The shear resistance of individual joint elements is calculated using the critical shear crack theory (CSCT) which relates shear resistance to slab rotation. Unlike other similar models reported in the literature, the joint strength is continually updated throughout the analysis as the slab rotation changes. The approach is presented for slabs without shear reinforcement but could be easily extended to include shear reinforcement. The adequacy of the proposed methodology is verified using experimental test data from isolated internal RC slab-column connections tested to failure under various loading arrangements and slab edge boundary conditions. Comparisons are also made with the predictions of nonlinear finite element analysis using 3-D solid elements, where the proposed methodology is shown to compare favourably whilst requiring significantly less computation time. Additionally, the proposed methodology enables simple calculation of the relative contributions of flexure, torsion and eccentric shear to moment transfer between slab and column. This information is pertinent to the development of improved codified design methods for calculating the critical design shear stress at eccentrically loaded columns.
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