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Publications (10 of 23) Show all publications
Bouckaert, I., Godio, M. & Pacheco de Almeida, J. (2024). A Hybrid Discrete-Finite Element method for continuous and discontinuous beam-like members including nonlinear geometric and material effects. International Journal of Solids and Structures, 294, Article ID 112770.
Open this publication in new window or tab >>A Hybrid Discrete-Finite Element method for continuous and discontinuous beam-like members including nonlinear geometric and material effects
2024 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 294, article id 112770Article in journal (Other academic) Published
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.

Keywords
Discontinuities, Discrete Element Methods, Contact, Applied Element Method, Nonlinear geometry, Nonlinear material
National Category
Computational Mathematics
Identifiers
urn:nbn:se:ri:diva-72336 (URN)10.1016/j.ijsolstr.2024.112770 (DOI)
Note

The first author is thankful for the financial support given by UCLouvain.

Available from: 2024-03-18 Created: 2024-03-18 Last updated: 2024-03-22Bibliographically approved
Godio, M. & Jacobsson, L. (2024). Experimental study on the hydromechanical behaviour of a natural unperturbed fracture under normal loading: Derivation of the equivalent hydraulic aperture and its digital reconstruction.
Open this publication in new window or tab >>Experimental study on the hydromechanical behaviour of a natural unperturbed fracture under normal loading: Derivation of the equivalent hydraulic aperture and its digital reconstruction
2024 (English)Report (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.

Publisher
p. 85
Series
RISE Rapport ; 2024:8
Keywords
Natural rock fracture, Hydro-mechanical behaviour, Transmissivity, Normal load, Coupled stress-flow test, Laminar flow
National Category
Materials Engineering
Identifiers
urn:nbn:se:ri:diva-71540 (URN)978-91-89896-49-9 (ISBN)
Note

The experimental work was funded by Svensk Kärnbränslehantering AB (SKB) and is a part of the international project, TASK 10, of the SKB Task Force on Modelling of Groundwater Flow and Transport of Solutes (GWFTS) which involves several international nuclear waste management organisations.

Available from: 2024-01-31 Created: 2024-01-31 Last updated: 2024-05-01Bibliographically approved
Romano, L., Godio, M., Johannesson, P., Bruzelius, F., Ghandriz, T. & Jacobson, B. (2023). Development of the Vastra Gotaland operating cycle for long-haul heavy-duty vehicles. IEEE Access
Open this publication in new window or tab >>Development of the Vastra Gotaland operating cycle for long-haul heavy-duty vehicles
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2023 (English)In: IEEE Access, E-ISSN 2169-3536Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2023
Keywords
autoregressive models, Autoregressive processes, Generators, Kinematics, Markov models, Markov processes, mission classification, Operating cycle, Random variables, road transport mission, Roads, Standards, stochastic modeling, Stochastic processes, Surfaces, Diesel engines, Energy efficiency, Fleet operations, Production control, Roads and streets, Stochastic models, Stochastic systems, Vehicles, Auto regressive process, Autoregressive modelling, Generator, Markov modeling, Road, Road transports, Stochastic-modeling, Classification (of information)
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:ri:diva-65748 (URN)10.1109/ACCESS.2023.3295989 (DOI)2-s2.0-85165273811 (Scopus ID)
Available from: 2023-08-07 Created: 2023-08-07 Last updated: 2023-08-07Bibliographically approved
Godio, M., Flansbjer, M. & Williams Portal, N. (2023). Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements. International Journal of Impact Engineering
Open this publication in new window or tab >>Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements
2023 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509Article in journal (Refereed) Epub ahead of print
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.

Keywords
Impacts, Masonry, Out-of-plane, Arching, Digital Image Correlation (DIC), High-speed cameras
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-64282 (URN)10.1016/j.ijimpeng.2023.104597 (DOI)
Note

This study was funded by the ÅForsk Foundation, through the ‘Young researcher’ granting scheme, grant agreement n. 20-335.

Available from: 2023-04-06 Created: 2023-04-06 Last updated: 2023-05-26Bibliographically approved
Godio, M., Flansbjer, M. & Williams Portal, N. (2023). Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements. International Journal of Impact Engineering, 178, Article ID 104597.
Open this publication in new window or tab >>Low-velocity out-of-plane impact tests on double-wythe unreinforced brick masonry walls instrumented with optical measurements
2023 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 178, article id 104597Article in journal (Refereed) Published
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.

Keywords
Impacts, Masonry, Out-of-plane, Arching, Digital image correlation (DIC), High-speed cameras
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-64373 (URN)10.1016/j.ijimpeng.2023.104597 (DOI)2-s2.0-85152227379& (Scopus ID)
Note

This study was funded by the ÅForsk Foundation, through the ‘Young researcher’ granting scheme, grant agreement n. 20-335.

Available from: 2023-04-25 Created: 2023-04-25 Last updated: 2023-05-26Bibliographically approved
Jacobsson, L. & Godio, M. (2023). Measuring the hydraulic transmissivity of a rock joint under varying normal load. In: IOP Conference Series: Earth and Environmental Science. Paper presented at Eurock 2022 Symposium: Rock and Fracture Mechanics in Rock Engineering and Mining, 11 September 2022 through 15 September 2022. Institute of Physics (1)
Open this publication in new window or tab >>Measuring the hydraulic transmissivity of a rock joint under varying normal load
2023 (English)In: IOP Conference Series: Earth and Environmental Science, Institute of Physics , 2023, no 1Conference paper, Published 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.

Place, publisher, year, edition, pages
Institute of Physics, 2023
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-65344 (URN)10.1088/1755-1315/1124/1/012050 (DOI)2-s2.0-85146617420 (Scopus ID)
Conference
Eurock 2022 Symposium: Rock and Fracture Mechanics in Rock Engineering and Mining, 11 September 2022 through 15 September 2022
Note

Funding details: TASK10; Funding text 1: The experimental work was funded by Swedish Nuclear Waste and Management Co, Sweden (SKB) and is a part of the international project, TASK10, on Groundwater Flow and Transport of Solutes (GWFTS) which involves several nuclear waste management companies.

Available from: 2023-06-15 Created: 2023-06-15 Last updated: 2023-06-15Bibliographically approved
Bouckaert, I., Godio, M. & Pacheco de Almeida, J. (2023). MODELING OF FRAMES WITH HYBRIDFEM, A PSEUDO-DISCRETE-FINITE MODEL INCLUDING NONLINEAR GEOMETRIC EFFECTS AND NONLINEAR MATERIALS. In: : . Paper presented at COMPDYN 2023 9th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. Athens, Greece, 12-–14 June 2023.
Open this publication in new window or tab >>MODELING OF FRAMES WITH HYBRIDFEM, A PSEUDO-DISCRETE-FINITE MODEL INCLUDING NONLINEAR GEOMETRIC EFFECTS AND NONLINEAR MATERIALS
2023 (English)Conference paper, Published 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.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:ri:diva-65528 (URN)
Conference
COMPDYN 2023 9th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. Athens, Greece, 12-–14 June 2023
Available from: 2023-06-22 Created: 2023-06-22 Last updated: 2023-06-22Bibliographically approved
Gagliardo, R., Godio, M., Portioli, F. P. A. & Landolfo, R. (2023). Seismic analysis of failure mechanisms in adjacent interacting stone masonry buildings via rigid block modeling. Bulletin of Earthquake Engineering
Open this publication in new window or tab >>Seismic analysis of failure mechanisms in adjacent interacting stone masonry buildings via rigid block modeling
2023 (English)In: Bulletin of Earthquake Engineering, ISSN 1570-761X, E-ISSN 1573-1456Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Geophysics
Identifiers
urn:nbn:se:ri:diva-64278 (URN)10.1007/s10518-023-01659-1 (DOI)
Note

The financial support of the research project DPC-ReLUIS: Work Package 5 ‘Integrated and low-impact strengthening interventions’ (2022–2024) funded by the Civil Protection Department IT (Grant no. 897-01/04/2022) is acknowledged.

Available from: 2023-03-27 Created: 2023-03-27 Last updated: 2023-07-06Bibliographically approved
Tomić, I., Penna, A., DeJong, M., Butenweg, C., Correia, A. A., Candeias, P. X., . . . Beyer, K. (2023). Shake-table testing of a stone masonry building aggregate: overview of blind prediction study. Bulletin of Earthquake Engineering
Open this publication in new window or tab >>Shake-table testing of a stone masonry building aggregate: overview of blind prediction study
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2023 (English)In: Bulletin of Earthquake Engineering, ISSN 1570-761X, E-ISSN 1573-1456Article in journal (Refereed) Epub ahead of print
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.

National Category
Geophysics
Identifiers
urn:nbn:se:ri:diva-64277 (URN)10.1007/s10518-022-01582-x (DOI)
Note

The project leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730900.

Available from: 2023-03-27 Created: 2023-03-27 Last updated: 2023-07-07Bibliographically approved
Godio, M., Flansbjer, M. & Williams Portal, N. (2023). Single- and double-wythe brick masonry walls subjected to four-point bending tests under different support conditions: Simply supported, rigid, non-rigid. Construction and Building Materials, 404, Article ID 132544.
Open this publication in new window or tab >>Single- and double-wythe brick masonry walls subjected to four-point bending tests under different support conditions: Simply supported, rigid, non-rigid
2023 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 404, article id 132544Article in journal (Refereed) Published
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.

Keywords
Unreinforced masonry (URM), Out-of-plane, Arching, Digital Image Correlation (DIC), Bending, Shear failure
National Category
Building Technologies
Identifiers
urn:nbn:se:ri:diva-66705 (URN)10.1016/j.conbuildmat.2023.132544 (DOI)
Note

This study was made possible with the support of RISE Research Institutes of Sweden (RISE) and Swedish Fortifications Agency (FORTV), working jointly in the Centre of excellence for fortifications (Centrum for fortifikatorisk kompetens, CFORT). 

Available from: 2023-09-07 Created: 2023-09-07 Last updated: 2023-09-07Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9586-8667

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