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  • 1.
    Bouckaert, Igor
    et al.
    UCLouvain, Belgium.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Almeida, Joao
    UCLouvain, Belgium.
    Large-displacement response of unreinforced masonry structures: comparison between analytical solutions and DEM models including open-source software2021Conference paper (Refereed)
  • 2.
    Bouckaert, Igor
    et al.
    UCLouvain, Belgium.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Pacheco de Almeida, Joao
    UCLouvain, Belgium.
    A strategy for generating pushover curves of block assemblies including post-peak branch using the discrete element method2022In: Proceedings of 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY., 2022, p. 839-Conference paper (Refereed)
    Abstract [en]

    Pushover analyses are often used to evaluate the seismic performance of a structure. They give an estimate of the ultimate displacement a structure can undergo, as well as of the residual resisting forces in the post-peak response. When modelling masonry structures composed of multiple blocks, obtaining the post-peak branch of the pushover curve can be difficult with a classic displacement-control strategy. This paper describes a strategy designed to compute this branch for multi-block systems subjected to a given pattern of forces, without the need to apply a displacement-control algorithm. The strategy is general, therefore straightforwardly implementable in different software tools and applicable to complex block assemblies. In the present work, it is implemented in two different DEM software, namely LMCG90 and UDEC, and tested on a benchmark problem for evaluating the in-plane response of masonry walls.

  • 3.
    Bouckaert, Igor
    et al.
    UCLouvain, Belgium.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Pacheco de Almeida, Joao
    UCLouvain, Belgium.
    MODELING OF FRAMES WITH HYBRIDFEM, A PSEUDO-DISCRETE-FINITE MODEL INCLUDING NONLINEAR GEOMETRIC EFFECTS AND NONLINEAR MATERIALS2023Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel numerical method for strucural analysis, called the Hybrid Discrete-Finite Element Method (HybriDFEM), is presented. In this method, a structure is modeled as an assembly of rigid blocks in contact. All the deformation is concentrated at the interfaces, which are modeled as series of distributed nonlinear multidirectional springs. The method shares similarities with the Discrete Element Methods (DEM) in its ability to account for contact interfaces and/or block deformability, and with the Applied Element Method (AEM) in the representation of interfaces as a series of normal and shear springs. However, it is close to the FEM in the way it is formulated, which offers the possibility to readily link both methods for potential hybrid applications. This paper focuses on the modeling of continuous and discontinuous frames with the HybriDFEM. It is shown how the model can do so with a nonlinear material model, and considering (or not) nonlinear geometric effects through large nodal displacements. Different nonlinear solution procedures implemented in HybriDFEM are demonstrated, such as load-control and various displacement-controlled methods. This model is able to simulate contacts between rigid or deformable units, an important feature when it comes to the modeling of, e.g., unreinforced masonry structures, with a reasonable computational cost and a formulation that is cast within the framework of the classical FEM.

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  • 4.
    Bouckaert, Igor
    et al.
    UCLouvain, Belgium.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Pacheco de Almeida, João
    UCLouvain, Belgium.
    A Hybrid Discrete-Finite Element method for continuous and discontinuous beam-like members including nonlinear geometric and material effects2024In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 294, article id 112770Article in journal (Other academic)
    Abstract [en]

    This paper introduces a novel formulation, called Hybrid Discrete-Finite Element (HybriDFEM) method, for modeling one-directional continuous and discontinuous planar beam-like members, including nonlinear geometric and material effects. In this method, the structure is modeled as a series of distinct rigid blocks, connected to each other through contact pairs distributed along the interfaces. Each of those contact pairs are composed of two nonlinear multidirectional springs in series, which can represent either the deformation of the blocks themselves, or the deformation of their interface. Unlike the Applied Element Method, in which contact pairs are composed of one single spring, the current approach allows capturing phenomena such as sectional deformations or relative deformations between two blocks composed of different materials. This method shares similarities with the Discrete Element Methods in its ability to model contact interfaces between rigid or deformable units, but does not require a numerical time-domain integration scheme. More importantly, its formulation resembles that of the classical Finite Elements Method, allowing one to easily couple the latter with HybriDFEM. Following the presentation of its formulation, the method is benchmarked against analytical solutions selected from the literature, ranging from the linear-elastic response of a cantilever beam to the buckling and rocking response of continuous flexible columns, and rigid block stackings. One final example showcases the coupling of a HybriDFEM element with a linear beam finite element.

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  • 5.
    Gagliardo, Raffaele
    et al.
    University of Naples Federico II, Italy.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Cascini, Lucrezia
    University of Naples Federico II, Italy.
    Portioli, Francesco
    University of Naples Federico II, Italy.
    Landolfo, Raffaele
    University of Naples Federico II, Italy.
    Vulnerability assessment of monumental artworks using contact time-history analysis2021Conference paper (Refereed)
  • 6.
    Gagliardo, Raffaele
    et al.
    University of Naples “Federico II”, Italy.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Portioli, Francesco
    University of Naples “Federico II”, Italy.
    Landolfo, Raffaele
    University of Naples “Federico II”, Italy.
    Rigid block modelling approach for the prediction of seismic performance of adjacent interacting masonry structures2022In: Proceedings of 3rd EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING & SEISMOLOGY., 2022, p. 3245-Conference paper (Refereed)
    Abstract [en]

    The current paper discusses the contents of the work completed for the project “SERA AIMS – BLIND PREDICTION COMPETITION”. The competition was focused on the prediction of the response of a masonry building composed of two adjacent interacting structural units under earthquake excitation. This research investigates the response of the experimental mock-up by using a numerical model based on the rigid block limit analysis and mathematical programming. The results of the analysis, namely, the failure modes and the corresponding collapse load multipliers, are related to base shear and peak ground accelerations observed for the damage and ultimate limit states using code provisions for the assessment of failure mechanisms in existing masonry structures. Finally, a preliminary comparison of numerical and experiemental results is presented.

  • 7.
    Gagliardo, Raffaele
    et al.
    University of Naples Federico II, Italy.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Portioli, Francesco P. A.
    University of Naples Federico II, Italy.
    Landolfo, Raffaele
    University of Naples Federico II, Italy.
    Seismic analysis of failure mechanisms in adjacent interacting stone masonry buildings via rigid block modeling2023In: Bulletin of Earthquake Engineering, ISSN 1570-761X, E-ISSN 1573-1456Article in journal (Refereed)
    Abstract [en]

    Groups of contiguous unreinforced stone masonry buildings are a common type of housing seen in old European downtowns. However, assessing their response to earthquakes poses several challenges to the analysts, especially when the housing units are laid out in compact configurations. In fact, in those circumstances a modeling technique that allows for the dynamic interaction of the units is required. The numerical study carried out in this paper makes use of a rigid block modeling approach implemented into in-house software tools to simulate the static behavior and dynamic response of an aggregate stone masonry building. Said approach is used to reproduce the results of bi-axial shake-table tests that were performed on a building prototype as part of the activities organized within the Adjacent Interacting Masonry Structures project, sponsored by the Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe. The experimental mock-up consisted of two adjacent interacting units with matching layout but different height. Two rigid block models are used to investigate the seismic response of the mock-up: a 3D model allowing for the limit analysis of the building on one hand, and a 2D model allowing for the non-linear static pushover and time-history analysis on the other. The 3D model was built for the blind prediction of the test results, as part of a competition organized to test different modeling approaches that are nowadays available to the analysts. The 2D model was implemented once the experimental data were made available, to deepen the investigation by non-linear static pushover and time-history analysis. In both models, the stonework is idealized into an assemblage of rigid blocks interacting via no-tension frictional interfaces, and mathematical programming is utilized to solve the optimization problems associated to the different types of analysis. Differences between numerical and experimental failure mechanisms, base shears, peak ground accelerations, and displacement histories are discussed. Potentialities and limitations of the adopted rigid block models for limit, pushover and time-history analyses are pointed out on the basis of their comparisons with the experimental results.

  • 8.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Williams Portal, Natalie
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements2023In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509Article in journal (Refereed)
    Abstract [en]

    Unreinforced brick masonry makes up today a significant piece of the European built environment, including not only residential buildings but also strategically important structures that are not designed to withstand blasts and impacts. Yet, it is difficult to accurately estimate the response of these structures and the extent of damage they sustain during such extreme loading conditions. This paper presents the implementation and discusses the results of laboratory impact tests conducted on natural-scale double-wythe unreinforced brick masonry walls, a typology that is frequently found in Northern Europe. The walls were spanning vertically between two reinforced concrete slabs and were subjected to low-velocity drop-weight pendulum tests in which they were repeatedly hit until the opening of a breach in the center of the wall. The tests were instrumented with both hard-wired and optical measurements, the latter consisting of high-speed cameras and digital image correlation techniques, to face the difficulty of observing cracks and determining the deflections of the walls with adequate accuracy at the time of the impact. Investigated in these tests were the out-of-plane response of the walls and their capacity to resist the impacts. The axial load applied on the top of the walls was varied for two wall configurations and monitored throughout the tests to study the effect of arching on the failure mechanism produced and number of repeated hits needed to open the breach. Of interest was also the evidence of cracking, more specifically the way it initiated on the undamaged walls and next propagated upon consecutive hits. The data generated from these tests are made available to support further investigations on unreinforced masonry structures subjected to extreme actions.

  • 9.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Williams Portal, Natalie
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements2023In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 178, article id 104597Article in journal (Refereed)
    Abstract [en]

    Unreinforced brick masonry makes up today a significant piece of the European built environment, including not only residential buildings but also strategically important structures that are not designed to withstand blasts and impacts. Yet, it is difficult to accurately estimate the response of these structures and the extent of damage they sustain during such extreme loading conditions. This paper presents the implementation and discusses the results of laboratory impact tests conducted on natural-scale double-wythe unreinforced brick masonry walls, a typology that is frequently found in Northern Europe. The walls were spanning vertically between two reinforced concrete slabs and were subjected to low-velocity drop-weight pendulum tests in which they were repeatedly hit until the opening of a breach in the centre of the wall. The tests were instrumented with both hard-wired and optical measurements, the latter consisting of high-speed cameras and digital image correlation techniques, to face the difficulty of observing cracks and determining the deflections of the walls with adequate accuracy at the time of the impact. Investigated in these tests were the out-of-plane response of the walls and their capacity to resist the impacts. The axial load applied on the top of the walls was varied for two wall configurations and monitored throughout the tests to study the effect of arching on the failure mechanism produced and number of repeated hits needed to open the breach. Of interest was also the evidence of cracking, more specifically the way it initiated on the undamaged walls and next propagated upon consecutive hits. The data generated from these tests are made available to support further investigations on masonry structures subjected to extreme actions.

  • 10.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Williams Portal, Natalie
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Single- and double-wythe brick masonry walls subjected to four-point bending tests under different support conditions: Simply supported, rigid, non-rigid2023In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 404, article id 132544Article in journal (Refereed)
    Abstract [en]

    Out-of-plane actions cause confined unreinforced masonry walls (URM) to develop what is known as an arching action. The role of arching is central in the resisting mechanisms of a wall; it contributes significantly to its loadbearing capacity as long as the wall’s deflections are minor, but gradually loses effect with increasing deflections, until collapse occurs. To date, limited experimental data is available on how arching develops in relation to the out-of-plane behaviour of the wall. This study brings new experimental evidence to this aspect. Quasi-static monotonic four-point bending tests were conducted on eleven brick wall strips, with reinforced concrete (RC) slabs affixed below and over the walls to simulate contact conditions of a typical construction system. The walls were tested vis-à-vis three different support conditions: simply supported, rigid, and non-rigid. The influence of these support conditions on the out-of-plane behaviour of the walls was studied on specimens with varying thickness – single and double wythe – and subjected to different levels of axial compression (or overload). While the former support condition was designed not to yield any arching inside the wall (unconfined masonry), the intermediate and latter solutions generated an arching action that was proportional respectively to the elongation of the wall (partially confined masonry), and its deflection (confined masonry). The walls were tested inside a bi-axial test setup that allowed not only the out-of-plane force but also the arching action to be measured, corroborating its central role in the development of the out-of-plane capacity of the walls. To support the observations, deformation characteristics and crack distributions were determined using two optical measurement systems placed in front and to the side of the walls, making use of the Digital Image Correlation (DIC) technique. The results of the tests are discussed in terms of failure mechanism as well as force and displacement capacity of the walls in relation to the investigated parameters. The test data is collected and made available to help with future research on the out-of-plane capacity of URM walls.

  • 11.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Experimental study on the hydromechanical behaviour of a natural unperturbed fracture under normal loading: Derivation of the equivalent hydraulic aperture and its digital reconstruction2024Report (Other academic)
    Abstract [en]

    This report describes the laboratory work undertaken to characterize the hydromechanical behaviour of a natural rock fracture under varying normal loading. The hydraulic transmissivity of a granite specimen with a sealed (unopened) quasi-planar natural fracture of length 200 mm and width 200 mm was measured. The transmissivity measurements were conducted in the two perpendicular directions of the fracture, repeating them at five different normal compression stress levels, namely, ~0, 1, 2, 4, and 8 MPa, and flow gradients. The fracture was mechanically opened, and the measurements were repeated to investigate the effect of opening the fracture on its hydraulic transmissivity and hydromechanical behaviour. For one direction, the change in transmissivity was explored for high normal compression stress levels, up to ~40 MPa. Laminar flow conditions were ensured at every stage of the experimental campaign by working at very low Reynolds numbers (<1). The equivalent hydraulic aperture of the fracture was derived by resorting to the parallel-plate model theory. The hydraulic aperture was compared to the mechanical aperture, which was obtained by measuring the deformation of the specimen. In addition to the transmissivity tests, the geometry of the lateral walls and surfaces of the fracture was documented and measured by a series of tools, namely, digital scans, high-resolution pictures, optical readings by a stand microscope, and contact pressure-sheet measurements. The results achieved in this campaign shed light on the hydraulic transmissivity of sealed (unopened) and consequently opened natural fractures, and its dependency to the applied normal compression stress at low to very-low flow rates.

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  • 12.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Jacobsson, Lars
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Laboratory low-transmissivity tests on natural rock fracture under varying normal load2022In: Programme of Geological Society of Sweden 150 year Anniversary meeting., 2022Conference paper (Other academic)
    Abstract [en]

    There is limited available data on natural rock fractures with low hydraulic transmissivity. In this study, we measured the transmissivity of a granite specimen with a 200×200 mm naturally-induced closed fracture under varying normal load. We repeated the measurements after opening the fracture to investigate how this affects its transmissivity. At each stage, we ensured laminar flows by setting Reynolds numbers << 1. Finally, we resorted to the parallel-plate theory to obtain the equivalent hydraulic aperture, that we compared to the mechanical aperture derived from the observed deformation.

  • 13.
    Godio, Michele
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Williams Portal, Natalie
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Magnusson, Johan
    Swedish Fortifications Agency, Sweden.
    Byggnevi, Magnus
    Swedish Fortifications Agency, Sweden.
    Experimental and numerical approaches to investigate the out-of-plane response of unreinforced masonry walls subjected to free far-field blasts2021In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 239, article id 112328Article, review/survey (Refereed)
    Abstract [en]

    Masonry walls are bulky and heavy and have therefore the potential to act naturally as a protective system to blasts. Yet, they are known to have a limited flexural and torsional capacity, particularly when unreinforced. When exposed to shockwaves, they experience out-of-plane failure mechanisms which may affect the overall stability of the building and engender flying debris inside the building. The out-of-plane response of unreinforced masonry walls to blasts depends on many factors characterizing both the wall and blast action, making any sort of prediction difficult. In this context, experimental tests and numerical models become key tools that can be used to study the wall’s response on a case-by-case basis. This review covers the major experimental and numerical approaches to assess the out-of-plane response of unreinforced masonry walls subjected to blasts. A methodological appraisal is used for the test methods, focusing on the preparation of the test items and test setup, the boundary conditions and failure mechanisms investigated, as well as the commonly employed measurement techniques. The survey on the modelling approaches includes key topics such as level of detail and cost, and reports strategies to model the wall and blast scenario. The review provides a thematic analysis of the available literature, aimed to assist the analyst in selecting a suitable tool for the investigation of masonry in the field of blast engineering. Furthermore, the findings presented herein can support amendments of existing codes and guidelines pertaining to the design of protective masonry structures.

  • 14.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Measuring the hydraulic transmissivity of a rock joint under varying normal load2022Conference paper (Refereed)
  • 15.
    Jacobsson, Lars
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Measuring the hydraulic transmissivity of a rock joint under varying normal load2023In: IOP Conference Series: Earth and Environmental Science, Institute of Physics , 2023, no 1Conference paper (Refereed)
    Abstract [en]

    The water flow rate through a rectangular granite specimen with a tight unopened natural induced joint of dimensions 200×200 mm was measured in two perpendicular directions. The measurements were conducted at five different levels of stress corresponding to loading from 0 to 8 MPa and unloading back to 0 MPa. The flow was measured at different hydraulic gradients in the range of 10 to 25. The results showed a joint transmissivity between 0.002-0.03 mm2/s and a hydraulic aperture of 8-32 μm. It was shown that the measurements performed in the second orientation displayed smaller transmissivity and hydraulic aperture as compared to those in the first orientation, showing a residual compaction after the first load cycle. The Reynolds number was less than one in all the measurements yielding laminar flow conditions. Deviations from the linear regime relationship were observed for the lowest flow rates (Re &lt; 0.1). A transitory regime was observed when varying the hydraulic gradient. This regime was observed to be longer at the lowest flow rates. © 2023 Institute of Physics Publishing. All rights reserved.

  • 16.
    Portioli, Francesco
    et al.
    University of Naples Federico II, Italy.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Calderini, Chiara
    University of Genoa, Italy.
    Lourenço, Paulo
    University of Minho, Portugal.
    A variational rigid-block modeling approach to nonlinear elastic and kinematic analysis of failure mechanisms in historic masonry structures subjected to lateral loads2021In: Earthquake engineering & structural dynamics (Print), ISSN 0098-8847, E-ISSN 1096-9845, Vol. 50, no 12, p. 3332-Article in journal (Refereed)
    Abstract [en]

    Displacement-based methods contained in recent standards for seismic safety assessment require the determination of the full nonlinear pushover curve for local failure mechanisms in historic masonry structures. This curve should reflect both the initial elastic behavior and the rigid body behavior after the activation of rocking. In this work, a rigid block model is proposed for the displacement-based seismic assessment of local collapse mechanisms of these structures. Masonry is modeled as an assemblage of two-dimensional rigid blocks in contact through frictional interfaces. Two types of contact models are formulated to capture, respectively, the pre and postpeak branches of the pushover curve: a unilateral elastic contact model, capturing the initial nonlinear behavior up to the force capacity of the structure, corresponding to the activation of the collapse mechanism, and a rigid contact model with finite friction and compressive strength, which describes the rigid-body rocking behavior up to the attainment of the displacement capacity of the structure. Tension-only elements are also implemented to model strengthening interventions with tie-rods. The contact problems associated with the elastic and rigid contact models are formulated using mathematical programming. For both models, a sequential solution procedure is implemented to capture the variation of the load multiplier with the increasing deformation of the structure (P–Δ effect). The accuracy of the modeling approach in reproducing the pushover curve of masonry panels subjected to horizontal seismic loads is evaluated on selected case studies. The solution is first tested against hand calculations, existing analytical models, and distinct element simulations. Then, comparisons against experimental tests follow. As a final application, the failure mechanism and pushover curve of a triumphal masonry arch are predicted by the model and its seismic assessment is performed according to codified force- and displacement-based methods, demonstrating the adequacy of the proposed tool for practice. © 2021 The Authors.

  • 17.
    Rezaie, Amir
    et al.
    EPFL Ecole Polythecnique Federale de Lausanne, Switzerland.
    Achanta, Radhakrishna
    Swiss Data Science Center, Switzerland; ETH Zurich, Switzerland.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Beyer, Katrin
    EPFL Ecole Polythecnique Federale de Lausanne, Switzerland.
    Comparison of crack segmentation using digital image correlation measurements and deep learning2020In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 261, article id 120474Article in journal (Refereed)
    Abstract [en]

    Reliable methods for detecting pixels that represent cracks from laboratory images taken for digital image correlation (DIC) are required for two main reasons. Firstly, the segmented crack maps are used as an input for some DIC methods that are based on discontinuous fields. Secondly, detected crack patterns can serve as inputs for predictive empirical models to obtain the level of damage to a body. The aim of this paper is to compare the performance of two approaches for crack segmentation on grayscale images acquired from two experimental campaigns on stone masonry walls. In the first approach, a threshold is applied to the maximum principal strain map calculated using post-processed DIC results. In the second approach, a deep convolutional neural network is used. The two methods are compared in terms of standard segmentation criteria, namely precision, dice coefficient and sensitivity. It is shown that the precision and dice coefficient obtained from the deep learning approach are much higher than those obtained from the threshold method (by almost 47% and 34%, respectively). However, the sensitivity computed from the deep learning method is slightly (~4%) lower than the threshold method. These results show that the deep learning method can bet-ter preserve the geometry of detected crack patterns, and the prediction in terms of pixels belonging to a crack is finally more accurate than the threshold method.

  • 18.
    Rezaie, Amir
    et al.
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Achanta, Radhakrishna
    EPFL, Switzerland; ETH Zurich, Switzerland.
    Beyer, Katrin
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Machine-learning for damage assessment of rubble stone masonry piers based on crack patterns2022In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 140, article id 104313Article in journal (Refereed)
    Abstract [en]

    Under seismic actions, stone masonry buildings are prone to damage. To assess the severity of damaged masonry buildings and their failure modes, engineers connect these problems to surface crack features, such as the crack width and the extent of cracking. We aim to further these assessments in this study, wherein we propose using simple machine learning models to predict: 1) three ratios encoding the degradation of stiffness, strength, and displacement capacity of damaged rubble stone masonry piers as a function of the observed crack features and the applied axial load and shear span ratio; and 2) the pre-peak vs. post-peak regime, based on the crack features. When predicting the stiffness, force, and drift ratios, the prediction error is significantly reduced when the axial load and shear span ratio are included in the feature vector. Furthermore, when predicting the pre-peak vs. post-peak regime, simple machine learning models such as the k-nearest neighbor and the logistic regression result in remarkable accuracy. The obtained results have significant implications on the automated post-earthquake assessment of masonry buildings using image data. It is shown based on documented laboratory test data, that, by selecting proper crack features and incorporating information about the kinematic and static boundary conditions, even simple machine learning models can predict accurately the damage level caused to a rubble masonry pier. The three crack features used in this study are the maximum crack width, length density, and complexity dimension. The pipeline developed in this paper is general enough and is applicable to other masonry typologies and elements upon new evaluation of crack features and image data.

  • 19.
    Rezaie, Amir
    et al.
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Beyer, Katrin
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Investigating the cracking of plastered stone masonry walls under shear–compression loading2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 306, article id 124831Article in journal (Refereed)
    Abstract [en]

    Cracks are the most important source of information about the damage that occurs to unreinforced masonry piers under seismic actions. To predict the structural state of unreinforced masonry piers after an earthquake, research models have been developed to quantify important features of crack patterns. One of the most used crack features is the width, but this can be influenced by several parameters such as the axial load ratio, the shear span ratio, and the loading protocol, which have not been fully studied in previous research studies. In this study, we use experimental data to investigate the evolution of cracking in stone masonry piers during the application of cyclic shear–compression loading. The data consists of gray-scale images taken during quasi-static shear–compression tests performed on six plastered rubble-stone masonry walls subjected to constant axial force and cycles of increasing drift demand. Through the combined use of digital image correlation and a pre-trained deep learning model, crack pixels are identified, post-processed, and quantified based on their width. The dependency of the crack width on the axial load ratio, the shear span ratio, and the loading protocol at the peak force and ultimate drift limit states of the piers is clarified by a displacement vector field analysis, histogram of the crack width, and the concentration of deformation in the cracks. We show that, as opposed to flexural cracks, diagonal shear cracks do not fully close when moving from the applied drift demand to the residual drift measured upon removal of the lateral load. Furthermore, we provide the maximum residual crack width at peak force and ultimate drift limit states. This study will improve the decision making abilities of future models used to quantify earthquake-induced damage to stone masonry buildings. 

  • 20.
    Romano, Luigi
    et al.
    Chalmers University of Technology, Sweden.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Johannesson, Pär
    RISE Research Institutes of Sweden, Materials and Production, Corrosion.
    Bruzelius, Fredrik
    Chalmers University of Technology, Sweden.
    Ghandriz, Toheed
    Volvo AB, Sweden.
    Jacobson, Bengt
    Chalmers University of Technology, Sweden.
    Development of the Vastra Gotaland operating cycle for long-haul heavy-duty vehicles2023In: IEEE Access, E-ISSN 2169-3536Article in journal (Refereed)
    Abstract [en]

    In this paper, a complete operating cycle (OC) description is developed for heavy-duty vehicles traveling long distances in the region of V&#x00E4;stra G&#x00F6;taland, Sweden. Variation amongst road transport missions is accounted for using a collection of stochastic models. These are parametrized from log data for all the influential road parameters that may affect the energy performance of heavy trucks, including topography, curvature, speed limits, and stop signs. The statistical properties of the developed OC description are investigated numerically by considering some composite variables, condensing the salient information about the road characteristics, and inspired by two existing classification systems. Two examples are adduced to illustrate the potential of the OC format, which enables ease of classification and detailed simulation of energy efficiency for individual vehicles, with application in vehicle design optimization and selection, production planning, and predictive maintenance. In particular, for the track used in the first example, a Volvo FH13 equipped with a diesel engine, simulation results indicate mean CO2 emissions of around 1700 g km-1, with a standard deviation of 360 g km-1; in the second example, dealing with electrical fleet sizing, the optimal proportion shows a predominance of tractor-semitrailer vehicles (70%) equipping 4 motors and 11 battery packs.

  • 21.
    Tomic, Igor
    et al.
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Oliver, Stuart
    Holmes Consulting LP, New Zealand.
    Seismic testing of adjacent interacting masonry structures – shake table test and blind prediction competition2022In: Proceedings of Third European Conferenceon Earthquake Engineering and Seismology, 2022, p. 3224-Conference paper (Refereed)
    Abstract [en]

    Across historical centres in Europe, stone masonry buildings form building aggregates that developed as the layout of the city or village was densified. In these aggregates, adjacent buildings can share structural walls with an older and a newer unit connected either by interlocking stones or by a layer of mortar. Observations after for example the recent Central Italy earthquakes showed that joints between the buildings were often the first elements to be damaged, leading to a complex interaction between the units. The analysis of such building aggregates is difficult due to the lack of guidelines, as the advances were impeded by the scarce experimental data. Therefore, the objective of the project AIMS (Seismic Testing of Adjacent Interacting Masonry Structures), included in the H2020 project SERA, was to provide such data by testing an aggregate of two double-leaf stone masonry buildings under two horizontal components of dynamic excitation. The test units were constructed at half-scale, with a two-storey building and a one-storey building. The buildings shared one common wall, while only a layer of mortar connected the façade walls. The floors were at different heights and had different beam orientations. Prior to the test, a blind prediction competition was organized with twelve participants from academia and industry that were provided with all the geometrical and material data, construction details, and the seismic input. The participants were asked to report results in terms of damage mechanisms, recorded displacements and base shear values. Results of the shaketable campaign are reported, together with a comparison with the blind predictions. Large scatter in terms of reported predictions highlights the impact of modelling uncertainties and the need for further tests.

  • 22.
    Tomić, I.
    et al.
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Penna, A.
    University of Pavia, Italy.
    DeJong, M.
    McGill University, Canada.
    Butenweg, C.
    RWTH Aachen University, Germany.
    Correia, A. A.
    National Laboratory for Civil Engineering, Portugal.
    Candeias, P. X.
    National Laboratory for Civil Engineering, Portugal.
    Senaldi, I.
    EUCENTRE European Centre for Training and Research in Earthquake Engineering, Italy.
    Guerrini, G.
    EUCENTRE European Centre for Training and Research in Earthquake Engineering, Italy; University of Pavia, Italy.
    Malomo, D.
    McGill University, Canada.
    Wilding, B.
    Basler & Hofmann AG, Switzerland.
    Pettinga, D.
    Holmes Consulting LP, New Zealand.
    Spanenburg, M.
    BAM Advies & Engineering, Netherlands.
    Galanakis, N.
    BAM Advies & Engineering, Netherlands.
    Oliver, S.
    Holmes Consulting LP, New Zealand.
    Parisse, F.
    University of Minho, Portugal.
    Marques, R.
    University of Minho, Portugal.
    Cattari, S.
    University of Genoa, Italy.
    Lourenço, P. B.
    University of Genoa, Italy.
    Galvez, F.
    University of Auckland, New Zealand.
    Dizhur, D.
    University of Auckland, New Zealand.
    Ingham, J. M.
    University of Auckland, New Zealand.
    Ramaglia, G.
    University of Naples “Federico II”, Italy.
    Lignola, G. P.
    University of Naples “Federico II”, Italy.
    Prota, A.
    University of Naples “Federico II”, Italy.
    AlShawa, O.
    Sapienza University of Rome, Italy.
    Liberatore, D.
    Sapienza University of Rome, Italy.
    Sorrentino, L.
    Sapienza University of Rome, Italy.
    Gagliardo, R.
    University of Naples “Federico II”, Italy.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Portioli, F.
    University of Naples “Federico II”, Italy.
    Landolfo, R.
    University of Naples “Federico II”, Italy.
    Solarino, F.
    University of Minho, Portugal.
    Bianchini, N.
    University of Minho, Portugal.
    Ciocci, M. P.
    University of Minho, Portugal.
    Romanazzi, A.
    University of Minho, Portugal.
    Aşıkoğlu, A.
    University of Minho, Portugal.
    D’Anna, J.
    University of Minho, Portugal.
    Ramirez, R.
    University of Minho, Portugal.
    Romis, F.
    University of Minho, Portugal.
    Marinković, M.
    University of Belgrade, Serbia.
    Đorđević, F.
    University of Belgrade, Serbia.
    Beyer, K.
    École Polytechnique Fédérale de Lausanne, Switzerland.
    Shake-table testing of a stone masonry building aggregate: overview of blind prediction study2023In: Bulletin of Earthquake Engineering, ISSN 1570-761X, E-ISSN 1573-1456Article in journal (Refereed)
    Abstract [en]

    City centres of Europe are often composed of unreinforced masonry structural aggregates, whose seismic response is challenging to predict. To advance the state of the art on the seismic response of these aggregates, the Adjacent Interacting Masonry Structures (AIMS) subproject from Horizon 2020 project Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) provides shake-table test data of a two-unit, double-leaf stone masonry aggregate subjected to two horizontal components of dynamic excitation. A blind prediction was organized with participants from academia and industry to test modelling approaches and assumptions and to learn about the extent of uncertainty in modelling for such masonry aggregates. The participants were provided with the full set of material and geometrical data, construction details and original seismic input and asked to predict prior to the test the expected seismic response in terms of damage mechanisms, base-shear forces, and roof displacements. The modelling approaches used differ significantly in the level of detail and the modelling assumptions. This paper provides an overview of the adopted modelling approaches and their subsequent predictions. It further discusses the range of assumptions made when modelling masonry walls, floors and connections, and aims at discovering how the common solutions regarding modelling masonry in general, and masonry aggregates in particular, affect the results. The results are evaluated both in terms of damage mechanisms, base shear forces, displacements and interface openings in both directions, and then compared with the experimental results. The modelling approaches featuring Discrete Element Method (DEM) led to the best predictions in terms of displacements, while a submission using rigid block limit analysis led to the best prediction in terms of damage mechanisms. Large coefficients of variation of predicted displacements and general underestimation of displacements in comparison with experimental results, except for DEM models, highlight the need for further consensus building on suitable modelling assumptions for such masonry aggregates.

  • 23.
    Williams Portal, Natalie
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Godio, Michele
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Byggnevi, Magnus
    Swedish Fortification Agency, Sweden.
    Magnusson, Johan
    Swedish Fortification Agency, Sweden.
    Quasi-static out-of-plane testing of unreinforced masonry walls instrumented with optical measurements2021Conference paper (Refereed)
    Abstract [en]

    Masonry buildings have existed in Sweden since the Middle Ages. The use of brick masonry as a construction material was pivotal until the beginning of the 20th century. Unreinforced masonry walls (URM) are massive and act as a protective system, yet they have limited capacity against explosions. When exposed to blasts, they experience out-of-plane failure, which engenders flying debris inside the building and may affect the stability of the building. Knowledge pertaining to the design and strengthening of URM walls against blasts has been identified as insufficient, on a Swedish context, to answer the current threats. In this paper, the results from quasi-static out-ofplane tests performed on URM walls made of clay bricks and lime-based mortar are presented. The tests were performed at RISE Research Institutes of Sweden by applying an incremental outof-plane displacement, while applying an axial load at the wall’s top edge. RC slabs were affixed over and below the walls to simulate the contact condition of a typical system. Two different types of support were tested for the upper slab: a) where the slab could slide along the vertical direction, and b) where this was prevented, leading to an arching action inside the wall. The results were generated as a part of an initial experimental stage of a project investigating URM walls loaded laterally by static and blast loads with optical measurements. Ultimately, the results will be used to verify existing models and/or develop a new model for the load-deformation relationship.

1 - 23 of 23
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