Publications
151 results found
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
This paper deals with the accurate modelling of unreinforced masonry (URM) behaviour using a 3D mesoscale description consisting of quadratic solid elements for masonry units combined with zero-thickness interface elements, the latter representing in a unified way the mortar and brick–mortar interfaces. A new constitutive model for the unified joint interfaces under cyclic loading is proposed. The model is based upon the combination of plasticity and damage. A multi-surface yield criterion in the stress domain governs the development of permanent plastic strains. Both strength and stiffness degradation are captured through the evolution of an anisotropic damage tensor, which is coupled to the plastic work produced. The restitution of normal stiffness in compression is taken into account by employing two separate damage variables for tension and compression in the normal direction. A simplified plastic yield surface is considered and the coupling of plasticity and damage is implemented in an efficient step by step approach for increased robustness. The computational cost of simulations performed using the mesoscale masonry description is reduced by employing a partitioning framework for parallel computation, which enables the application of the model at structural scale. Numerical results are compared against experimental data on realistic masonry components and structures subjected to monotonic and cyclic loading to show the ability of the proposed strategy to accurately capture the behaviour of URM under different types of loading.
Fieber A, Gardner L, Macorini L, 2018, Design of steel structures using advanced analysis with strain limits, Eighth International Conference on Thin-Walled Structures, ICTWS 2018
Setiawan A, Vollum R, Macorini L, 2018, Implementation of the critical shear crack theory to predict punching failure in the analysis of RC layered-shells, 12th fib International PhD Symposium in Civil Engineering
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
Many masonry arch bridges cross waterways and are built on shallow foundations which are often submerged and exposed to the scouring action of the stream. The limited resistance of masonry arch bridges to foundation settlements makes them very vulnerable to scour and calls for the development of advanced tools for evaluating and improving the capacity against this flood-induced effect. This paper describes a novel three-dimensional modelling strategy for describing the behaviour of multi-span masonry arch bridges subjected to scour at the base of the pier shallow foundations. A mesoscale description is employed for representing the heterogeneous behaviour of masonry units, mortar joints and brick-mortar interfaces, whereas a domain partitioning approach allowing for parallel computation is used to achieve computational efficiency. The scouring process is described via a time-history analysis in which the elements representing the soil are progressively removed from the model according to a specific scour evolution. The proposed modelling approach is first employed to simulate available experimental tests on a dry masonry wall subjected to the settlement of the bearing system and on a reduced scale brick-masonry bridge specimen subjected to scour-induced pier settlements. Subsequently, a numerical example consisting of a multi-span arch bridge subjected to the scouring action is presented to illustrate the potential of the proposed modelling approach and its capabilities for evaluating the vulnerability and risk of masonry arch bridges under flood scenarios.
Minga E, Macorini L, Izzuddin B, 2018, Enhanced mesoscale partitioned modelling of heterogeneous masonry structures, International Journal for Numerical Methods in Engineering, Vol: 113, Pages: 1950-1971, ISSN: 0029-5981
This paper presents an accurate and efficient computational strategy for the 3‐dimensional simulation of heterogeneous structures with unreinforced masonry components. A mesoscale modelling approach is employed for the unreinforced masonry parts, whereas other material components are modelled independently with continuous meshes. The generally nonmatching meshes of the distinct domains are coupled with the use of a mesh tying method. The physical interaction between the components is captured with the use of zero‐thickness cohesive interface elements. This strategy enables the optimisation of the individual meshes leading to increased computational efficiency. Furthermore, the elimination of the mesh compatibility requirement allows the 3‐dimensional modelling of complex heterogeneous structures, ensuring accurate representation of each component's nonlinear behaviour and their interaction. Numerical examples, including a comparative analysis on the elastic and nonlinear response of a masonry bridge considering arch‐backfill interaction and the nonlinear simulation of a multileaf wall, are presented to show the unique features of the proposed strategy and its predictive power in comparison with experimental and numerical results found in the literature.
Setiawan A, Vollum R, Macorini L, 2018, NUMERICAL INVESTIGATION ON PUNCHING SHEAR OF SLAB-COLUMN CONNECTIONS SUBJECTED TO SEISMIC LOADING, 16th European Conference on Earthquake Engineering
Demirci C, Malaga Chuquitaype C, Macorini L, 2018, Drift response of tall cross-laminated timber buildings under realistic earthquake loads, 16th European Conference on Earthquake Engineering (16ECEE)
This paper examines the drift response of tall cross-laminated timber (CLT) buildings subjected to a large set of real strong ground motions. Particular focus is placed on the influence of ground-motion frequency content on the inelastic drift demands of multi-storey CLT building structures. A total of 68 CLT buildings with varying structural characteristics were modelled and subjected to a set of 1656 real acceleration records. The effect of the frequency content of ground-motion, characterised by its mean period, Tm, is found to be determinant on the inelastic deformation demands of CLT walled buildings. Furthermore, the evolution of drift demands as a function of tuning ratio reveals different trends for low and high-rise CLT buildings. Prediction models for the estimation of global and inter-storey drift response on low-, mid- and high-rise CLT buildings are developed by means of nonlinear regression analysis. Finally, a comparative study is performed with reference to Eurocode 8 equal displacement rule and recent assessment proposals is outlined
Setiawan A, Vollum R, Macorini L, 2018, Implementation of the critical shear crack theory to predict punching failure in the analysis of rc layered- shells, Pages: 665-672, ISSN: 2617-4820
This paper proposes a novel methodology for modelling punching failure in slabs without shear reinforcement in which joint elements are combined with RC layered-shell elements. The shear resistance of the joints is calculated using the failure criterion of the critical shear crack theory (CSCT). The predictions are verified using experimental test data from isolated RC punching specimens tested to failure under either concentric or eccentric loading. Comparisons are also made with the predictions of nonlinear finite element analysis with ATENA using 3D-solid elements. It is shown that the proposed methodology is not only computationally more efficient than solid element modelling but also capable of capturing the occurrence of punching failure accurately.
Tiberti S, Milani G, Macorini L, 2018, A Novel Pixel Limit Analysis Homogenization Model for Random Masonry, International Conference of Numerical Analysis and Applied Mathematics (ICNAAM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
Setiawan A, Vollum R, Macorini L, 2018, Nonlinear Finite Element Analysis of Reinforced Concrete Flat Slabs Subjected to Reversed-Cyclic Loading, Fib Symposium on High Tech Concrete - Where Technology and Engineering Meet, Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 814-822
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Demirci C, Malaga Chuquitaype C, Macorini L, 2017, Seismic drift demands in multi-storey cross-laminated timber buildings, Earthquake Engineering and Structural Dynamics, Vol: 47, Pages: 1014-1031, ISSN: 0098-8847
This paper investigates the seismic response of multi-storey cross-laminated timber (CLT) buildings and its relationship with salient ground-motion and building characteristics. Attention is given to the effects of earthquake frequency content on the inelastic deformation demands of platform CLT walled structures. The response of a set of 60 CLT buildings of varying number of storeys and panel fragmentation levels representative of a wide range of structural configurations subjected to 1656 real earthquake records is examined. It is shown that, besides salient structural parameters like panel aspect ratio, design behaviour factor and density of joints, the frequency content of the earthquake action as characterised by its mean period has a paramount importance on the level of nonlinear deformations attained by CLT structures. Moreover, the evolution of drifts as a function of building to ground-motion periods ratio is different for low and high-rise buildings. Accordingly, nonlinear regression models are developed for estimating the global and inter-storey drifts demands on multi- storey CLT buildings. Finally, the significance of the results is highlighted with reference to European seismic design procedures and recent assessment proposals.
Kucukler M, Gardner L, Macorini L, 2017, Design of web-tapered steel members through a stiffness reduction method, 8th European Conference on Steel and Composite Structures (Eurosteel 2017)
Tubaldi E, Macorini L, Izzuddin B, 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
Scouring at the base of bridge piers is the major cause of bridge collapses worldwide. Computing the scour risk of bridge foundations is therefore key for a correct management and allocation of resources for maintenance and scour mitigation works. Existing risk-assessment models compute the vulnerability of bridge foundations to scour by comparing the equilibrium scour depth associated with peak-flow discharges characterized by a given return period (usually of 100–200 years) with the critical foundation depth of the bridge. This approach neglects completely the history-dependent and time-dependent nature of scour. Yet, it is well known that bridge collapses can often be induced by the accumulation of scour during multiple flood events.This study aims at developing a novel probabilistic framework for the computation of bridge-pier vulnerability to scour using a Markovian approach to account for memory effects in scour development. The paper focuses on the case of local pier scour occurring in clear-water conditions whereby cumulative effects are significant, well understood and known to be the cause of recent reported bridge collapses.A simplified numerical example consisting of an idealised bridge pier in a canal is considered to clarify the application of the proposed framework and to shed light on the effects of some assumptions introduced to simplify the probabilistic scour assessment.
Zhang Y, Macorini L, Izzuddin B, 2017, Numerical investigation of arches in brick-masonry bridges, Structure and Infrastructure Engineering, Vol: 14, Pages: 14-32, ISSN: 1744-8980
A significant number of old masonry bridges are still in use and need to be assessed considering current traffic loading and safety requirements. Masonry bridges are complex heterogeneous systems, where masonry arches represent the main components. Thus arealistic modellingof archesis vital for accurate assessment of masonry bridges. The authors have previously proposed and validated a detailed mesoscale description for masonry arches allowing for the actual masonry bond and the specific arch geometry including the case of skew arches.In this paper,the proposed mesoscalemodelling strategy is used in a comprehensive numericalstudyto investigate the effects of various parameters,includingmasonry bond and defects in the brickwork, abutment stiffness and movements at the supports,which are usually disregarded in practical assessment of masonry arches and bridges.The results achieved show how these parameters affect the ultimate load capacity, failure mechanisms and initial stiffness of square and skew arches, where the used of detailed 3D mesoscale modelling is critical in providing accurate response predictionsunder a variety of loading conditions for which reduced models might provide incorrect results.
Bras Xavier F, Macorini L, Izzuddin B, et al., 2017, Pushdown tests on masonry infilled frames for assessment of building robustness, Journal of Structural Engineering, Vol: 143, ISSN: 1943-541X
The research presented in this paper addresses the influence of non-structural masonry infill on the resistance of multi-storey buildings to progressive collapse under sudden column loss scenarios. In particular, the structural response of infilled frames in peripheral bays is investigated within the scope of a design-oriented robustness assessment framework previously developed at Imperial College London. This allows due consideration of structural redundancy, ductility, strength, dynamic effects and energy absorption capabilities in a unified manner. The realistic contribution of masonry panels towards collapse arrest is examined considering the results from full-scale laboratory tests performed on different two-bay frames with brick-masonry infill subjected to incremental pushdown deformation, capturing the dominant deformation mode actually found following removal of an edge column. In these physical tests, it is observed that the failure mechanisms and damage patterns displayed by the infill panels under pushdowndeformation are similar to those activated by lateral pushover loading. Clear evidence of diagonal cracking and shear sliding, eventually culminating in crushing of the compressed corners, is noted. Different infill configurations are tested, including central openings and an initial gap between masonry and frame elements. Overall, a global stable response is observed even in the presence of severe damage in the masonry panels, delivering a monotonic supply of energy absorption with increasing downwards displacement. The outcome from this experimental research provides mechanically sound and quantifiable evidence that non-structural masonry infill panels in peripheral frames offer a reliable and efficient source of enhanced robustness under column loss events. Due to the widespread application of masonry inf
Setiawan A, Vollum RL, Macorini L, 2017, NONLINEAR FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE FLAT SLABS SUBJECTED TO REVERSED-CYCLIC LOADING, fib Symposium 2017
Demirci C, Malaga Chuquitaype C, Macorini L, 2017, Seismic behaviour and design of tall cross-laminated timber buildings, 16th World Conference on Earthquake Engineering
Occhipinti G, Izzuddin B, Calio I, et al., 2017, Realistic 3D nonlinear dynamic analysis of existing and retrofitted multi-storey RC buildings subject to earthquake loading, Pages: 1685-1699
This paper presents a high fidelity numerical model developed to investigate the seismic performance of an original and retrofitted 10-storey reinforced concrete (RC) framed building. The analysed structure represents a typical existing building in Catania, Italy, which was designed according to old standards to resist gravity and wind loading but not earthquakes. The proposed numerical description adopts beam-column elements for beams and columns and special purpose shell elements for modelling RC floor slabs, both allowing for geometric and material nonlinearity. In order to model the influence of masonry infill, a novel macro-element is developed within a FE framework based on a discrete formulation. 3D nonlinear dynamic simulations are performed considering sets of natural accelerograms acting simultaneously along the two 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 behaviour of large structures, the partitioning approach previously developed at Imperial College is adopted, enabling effective parallelisation on HPC systems. The numerical results obtained from the 3D nonlinear dynamic simulations are presented and discussed, focusing on the variation in time of the deformed shape, inter-storey drifts, plastic deformations and internal force distribution, considering or neglecting the infill panel contribution. The original structure showed a very poor seismic performance, where the consideration of the infill panel contribution leads to significant variation in the response. An effective strengthening solution utilising eccentric steel bracings with dissipative shear links is also illustrated and employed to retrofit the original structure. A detailed model of the retrofitting components is also proposed and implemented within the detailed model for the original building. The results of numeric
Tubaldi E, Macorini L, Izzuddin B, 2017, Flood risk assessment of masonry arch bridges, Pages: 140-153
Floods are one of the most common natural disasters in Europe, responsible for the damage and collapse of many masonry arch bridges built over rivers and canals. The accurate prediction of the safety of these bridges against flood-induced loading is a task of paramount importance for their preservation. This paper describes the framework developed by the authors for the flood risk assessment of masonry arch bridges, accounting for the specific characteristics of the analysed structures, the most critical types of loading associated with floods, and the various sources of uncertainty relevant to the problem. The proposed framework combines the results of flood hazard analysis and of structural vulnerability analysis to obtain the flood risk estimate. A case study consisting of a three-span bridge under scour is considered to illustrate the application of the proposed framework and to show the capabilities of the advanced modelling technique developed for evaluating the effects of flood actions on masonry arch bridges.
Lima C, Martinelli E, Macorini L, et al., 2016, Modelling beam-to-column joints in seismic analysis of RC frames, Earthquakes and Structures, ISSN: 2092-7614
Several theoretical and analytical formulations for the prediction of shear strength in reinforced concrete (RC) beam-to-column joints have been recently developed. Some of these predictive models are included in the most recent seismic codes and currently used in practical design.On the other hand, the influence of the stiffness and strength degradations in RC joints on the seismic performance of RC framed buildings has been only marginally studied, and it is generally neglected in practice-oriented seismic analysis. To investigate such influence, this paper proposes a numerical description for representing the cyclic response of RC exterior joints. This is then used in nonlinear numerical simulations of RC frames subjected to earthquake loading. According to the proposed strategy,RC joints are modelled using nonlinear rotational spring elements with strength and stiffness degradations and limited ductility under cyclic loading. The proposed joint model has been firstly calibrated against the results from experimental tests on 12 RC exterior joints. Subsequently, nonlinear static and dynamic analyses have been carried out on two-, three-and four-storey RC frames, which represent realistic existing structures designed according to old standards. The numerical results confirm that the global seismic response of the analysed RC frames is strongly affected by the hysteretic damage in the beam-to-column joints, which determines the failure mode of the frames. This highlights that neglecting the effects of joints damage may potentially lead to non-conservative seismic assessment of existing RC framed structures.
Zhang Y, Macorini L, Izzuddin BA, 2016, Mesoscale partitioned analysis of brick-masonry arches, Engineering Structures, Vol: 124, Pages: 142-166, ISSN: 1873-7323
Past research has shown that masonry mesoscale descriptions, where bricks and mortar joints are modelled separately, offer a realistic representation of the mechanical behaviour of masonry components. In the case of masonry arches, thus far the use of this approach has been restricted to 2D analysis mainly because of the significant computational effort required. However conventional 2D models may lead to a crude representation of the response of masonry arches which is inherently three-dimensional, and they cannot properly capture the actual response of masonry arches subjected to eccentric loading or the behaviour of arches with complex geometry (e.g. skew arches). In this paper, the nonlinear response of brick-masonry arches up to collapse is investigated using an accurate 3D mesoscale description utilising solid elements for representing brick units and 2D nonlinear interface elements for describing mortar joints and brick-mortar interfaces. The masonry mesoscale strategy is then combined with a domain partitioning approach allowing for parallel computation which guarantees computational efficiency. The accuracy and potential of the proposed numerical description are shown in numerical examples, including comparisons against experimental results on realistic square and skew brick-masonry arches.
Gardner L, Yun X, Macorini L, et al., 2016, Hot-rolled steel and steel-concrete composite design incorporating strain hardening, Structures, Vol: 9, Pages: 21-28, ISSN: 2352-0124
Current design codes for steel and steel-concrete composite structures are based on elastic, perfectly plastic material behaviour and can lead to overly conservative strength predictions due to the neglect of the beneficial influence of strain hardening, particularly in the case of stocky, bare steel cross-sections and composite beams under sagging bending moments. The Continuous Strength Method (CSM) is a deformation based design method that enables material strain hardening properties to be exploited, thus resulting in more accurate capacity predictions. In this paper, a strain hardening material model, which can closely represent the stress-strain response of hot-rolled steel, is introduced and incorporated into the CSM design framework. The CSM cross-section resistance functions, incorporating strain hardening, are derived for hot-rolled steel sections in compression and bending, as well as hot-rolled steel-concrete composite sections where their neutral axes lie within the concrete slab in bending. Comparisons of the capacity predictions with a range of experimental data from the literature and finite element data generated herein demonstrate the applicability and benefits of the proposed approach.
Kucukler M, Gardner L, Macorini L, 2016, Development and assessment of a practical stiffness reduction method for the in-plane design of steel frames, Journal of Constructional Steel Research, Vol: 126, Pages: 187-200, ISSN: 1873-5983
In this paper, the development and assessment of a stiffness reduction method for the in-plane design of steel frames is presented. The adopted stiffness reduction approach is implemented by reducing the flexural stiffnesses (EI) of the members of a steel frame by considering the first-order forces they are subjected to through the stiffness reduction functions and performing Geometrically Nonlinear Analysis (i.e. second-order elastic analysis). Since the presented approach uses stiffness reduction functions that fully take into account the deleterious influence of imperfections and the spread of plasticity on the structural response and member strengths, it obviates the need of using member design equations, and only requires cross-section strength checks. The accuracy of the presented approach is illustrated for individual steel members and non-redundant and redundant benchmark steel frames from the literature. In all the considered cases, the presented method is verified against the results obtained from nonlinear finite element modelling. A comparison of the presented approach against the notional load method of the European structural steel design code EN 1993-1-1 and the direct analysis method of the US structural steel design code AISC 360-10 is also provided.
Chisari C, Macorini L, Amadio C, et al., 2016, Optimal sensor placement for structural parameter identification, Structural and Multidisciplinary Optimization, Vol: 55, Pages: 647-662, ISSN: 1615-147X
The identification of model material parameters is often required when assessing existing structures, in damage analysis and structural health monitoring. A typical procedure considers a set of experimental data for a given problem and the use of a numerical or analytical model for the problem description, with the aim of finding the material characteristics which give a model response as close as possible to the experimental outcomes. Since experimental results are usually affected by errors and limited in number, it is important to specify sensor position(s) to obtain the most informative data. This work proposes a novel method for optimal sensor placement based on the definition of the representativeness of the data with respect to the global displacement field. The method employs an optimisation procedure based on Genetic Algorithms and allows for the assessment of any sensor layout independently from the actual inverse problem solution. Two numerical applications are presented, which show that the representativeness of the data is connected to the error in the inverse analysis solution. These also confirm that the proposed approach, where different practical constraints can be added to the optimisation procedure, can be effective in decreasing the instability of the parameter identification process.
Rinaldin G, Amadio C, Macorini L, 2016, A macro-model with nonlinear springs for seismic analysis of URM buildings, Earthquake Engineering & Structural Dynamics, Vol: 45, Pages: 2261-2281, ISSN: 0098-8847
Seismic assessment of existing unreinforced masonry buildings represents a current challenge in structural engineering. Many historical masonry buildings in earthquake regions were not designed to withstand seismic loading, thus these structures often do not meet the basic safety requirements recommended by current seismic codes and need to be strengthened considering the results from realistic structural analysis. This paper presents an efficient modelling strategy for representing the nonlinear response of unreinforced masonry components under in-plane cyclic loading which can be used for practical and accurate seismic assessment of masonry buildings. According to the proposed strategy, a generic masonry perforated walls is modelled using an equivalent frame approach, where each masonry component is described utilising multi-spring nonlinear elements connected by rigid links. When modelling piers and spandrels, nonlinear springs are placed at the two ends of the masonry element for describing the flexural behaviour, and in the middle for representing the response in shear. Specific hysteretic rules allowing for degradation of stiffness and strength are then used for modelling the member response under cyclic loading. The accuracy and the significant potential of the proposed modelling approach are shown in several numerical examples, including comparisons against experimental results and the nonlinear dynamic analysis of a building structure.
Tubaldi E, Macorini L, Izzuddin BA, 2016, SAFETY OF MASONRY ARCH BRIDGES AGAINST FLOOD HAZARD, ARCH'16 Conference
Xavier FB, Macorini L, Izzuddin BA, 2016, Contribution of masonry cladding for robustness enhancement of multi-storey buildings under sudden column loss, 16th International Brick and Block Masonry Conference
Gardner L, Kucukler M, Macorini L, 2016, Deformation-Based Design of Composite Beams, 7th International Conference on Composite Construction in Steel and Concrete, Publisher: AMER SOC CIVIL ENGINEERS, Pages: 131-145
Kucukler M, Gardner L, Macorini L, 2016, Stiffness reduction method for the in-plane design of steel frames, SDSS, Pages: 99-106
Copyright ©: SDSS'2016. A stiffness reduction method for the in-plane design of steel frames is proposed in this paper. The proposed method is performed by (i) reducing the flexural stiffnesses of the members of a frame on the basis of the first-order forces they withstand and (ii) carrying out Geometrically Nonlinear Analysis. The ultimate capacity of the structure is defined as the point at which the ultimate strength of the most heavily loaded cross-section is reached. Ow-ing to the full consideration of the deleterious influence of the spread of plasticity and imper-fections through stiffness reduction, the proposed approach eliminates the need of using member design equations or modelling member out-of-straightnesses; only cross-section strength checks are required. The verification of the proposed approach against results from the nonlinear finite element modelling of a series of benchmark frames is presented.
Xavier FB, Macorini L, Izzuddin BA, 2016, Contribution of masonry cladding for robustness enhancement of multi-storey buildings under sudden column loss, 16th International Brick and Block Masonry Conference (IBMAC), Publisher: CRC PRESS-BALKEMA, Pages: 1383-1390
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