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Efficient and objective modeling of strain localization using transient gradient-enhanced damage models
No full textFaculteit Industriële ingenieurswetenschappen master in de industriële wetenschappen: bouwkunde Masterthesis Efficient and objective modeling of strain localization using transient gradient-enhanced damage models 2019•2020 PROMOTOR : Prof. dr. ing. Bram VANDOREN Tine Engelen Scriptie ingediend tot het behalen van de graad van master in de industriële wetenschappen: bouwkunde Confidentieel Gezamenlijke opleiding UHasselt en KU Leuve
Mechanical characterisation and structural design of hybrid timber- glass diaphragms with integrated photovoltaics
No full textThis study investigates the structural performance of hybrid timber-glass frame
walls designed to enhance horizontal stability, the so-called racking resistance
in façade structures. An important additional challenge is the integration
of photovoltaic solar cells within structural glass elements, while maintaining
structural integrity.
Lightweight timber structures are an increasingly important field in construction
engineering since these structures have a lower environmental impact than
traditional steel or concrete structures. In parallel, recent developments in the
architectural design of buildings favour open spaces. When such a building has
fewer inner structural walls, the stability and stiffness of the façade become more
important. The timber buildings’ racking resistance is of particular concern. The
racking resistance of a timber frame can be increased by using sheathing panels
(creating diaphragm walls), wind bracings or stiff timber connections between
studs and rails. However, current calculation methods (Eurocode 5) do not
account for the structural contribution of panels with window openings. This
raises problems regarding the in-plane stiffness (racking resistance) of buildings
with large surfaces of glass windows. One solution is to increase the number of
diaphragms in the timber frame building’s façade by structurally activating the
glass panels.
In order for the glass to contribute structurally to the façade, a structural
bond between the timber and the glass can be employed. In this thesis, the
mechanical performance of bonded timber-glass connections is examined through
experimental tensile and shear tests. Four two-component silicone adhesives and
one one-component polyurethane adhesive are evaluated. Special attention is
given to the failure behaviour of the adhesives, where both cohesive failure and
loss of adhesion are identified. The nonlinear stress-strain behaviour of these
adhesives is evaluated and used to assess different hyperelastic material models.
Two calibration methods are used to determine the model parameters of the
hyperelastic material models. The first method, assuming theoretical stress states,
is inadequate for the performed tensile tests, whereas the second method, using an
inverse parameter fitting method, yields good results. Additionally, a phase-field
damage model is developed to predict adhesive failure loads. These findings can
be used to model bonded timber-glass connections in larger structures. The structural performance of structural glass elements with integrated
photovoltaics is also investigated using numerical modelling. The model predicts
stresses and strains in the glass and solar cells under various loading conditions.
To validate these simulations, experimental in- and out-of-plane bending tests are
performed on glass/glass photovoltaic (PV) modules. This combined numericalexperimental approach results in reliable models for designing structural timberglass façade elements with integrated photovoltaics.
The study further evaluates the effects of shear loads on the system’s
components. Eight diaphragm specimens (1.2 m × 1.2 m) are tested using two
different structural silicone adhesives, with and without a tie-down anchoring of the
leading stud. Various measurement techniques, including displacement sensors
(linear variable differential transformers or LVDTs), digital image correlation, fibre
Bragg gratings and strain gauges, are used to analyse component behaviour. The
specimens primarily failed due to adhesive rupture. Results show that anchoring
the wall with a tie-down increases the system’s racking stiffness by 30%. The
strains on the glass and solar cells are analysed during experimental in-plane shear
tests, confirming that the solar cells remain undamaged. Electroluminescence
testing verifies this finding.
Furthermore, an analytical design method based on Eurocode 5 (FprEN 1995-
1-1) and spring models is proposed and compared with the experimental results.
While this method tends to underestimate the wall elements’ stiffness, it accurately
predicts the minimum load-bearing capacity. Finally, a detailed finite element
model is developed and calibrated using small-scale connection tests. The
model closely matches experimental measurements in terms of strength and
stiffness. A parametric study assesses the influence of different aspect ratios,
glass thicknesses, adhesive bond dimensions, and other parameters.
Overall, this study demonstrates that glass can be structurally activated
to increase the stiffness of lightweight timber structures when bonded with
adhesives. This challenges the conventional assumption that glass openings
do not structurally contribute. Additionally, integrating photovoltaics into the
glass enables multifunctional façade elements. The findings confirm that, for
the tested specimens, standard solar cells withstand in-plane shear forces in
the glass without compromising structural performance. This research advances
the field by exploring innovative solutions to overcome current challenges in
timber frame design, offering a pathway toward more sustainable architecture
and structural engineering, and contributing to the development of next-generation
building systems that integrate both structural performance and renewable energy
generation
Mechanical characterisation and structural design of hybrid timber- glass diaphragms with integrated photovoltaics
No full textThis study investigates the structural performance of hybrid timber-glass frame
walls designed to enhance horizontal stability, the so-called racking resistance
in façade structures. An important additional challenge is the integration
of photovoltaic solar cells within structural glass elements, while maintaining
structural integrity.
Lightweight timber structures are an increasingly important field in construction
engineering since these structures have a lower environmental impact than
traditional steel or concrete structures. In parallel, recent developments in the
architectural design of buildings favour open spaces. When such a building has
fewer inner structural walls, the stability and stiffness of the façade become more
important. The timber buildings’ racking resistance is of particular concern. The
racking resistance of a timber frame can be increased by using sheathing panels
(creating diaphragm walls), wind bracings or stiff timber connections between
studs and rails. However, current calculation methods (Eurocode 5) do not
account for the structural contribution of panels with window openings. This
raises problems regarding the in-plane stiffness (racking resistance) of buildings
with large surfaces of glass windows. One solution is to increase the number of
diaphragms in the timber frame building’s façade by structurally activating the
glass panels.
In order for the glass to contribute structurally to the façade, a structural
bond between the timber and the glass can be employed. In this thesis, the
mechanical performance of bonded timber-glass connections is examined through
experimental tensile and shear tests. Four two-component silicone adhesives and
one one-component polyurethane adhesive are evaluated. Special attention is
given to the failure behaviour of the adhesives, where both cohesive failure and
loss of adhesion are identified. The nonlinear stress-strain behaviour of these
adhesives is evaluated and used to assess different hyperelastic material models.
Two calibration methods are used to determine the model parameters of the
hyperelastic material models. The first method, assuming theoretical stress states,
is inadequate for the performed tensile tests, whereas the second method, using an
inverse parameter fitting method, yields good results. Additionally, a phase-field
damage model is developed to predict adhesive failure loads. These findings can
be used to model bonded timber-glass connections in larger structures. The structural performance of structural glass elements with integrated
photovoltaics is also investigated using numerical modelling. The model predicts
stresses and strains in the glass and solar cells under various loading conditions.
To validate these simulations, experimental in- and out-of-plane bending tests are
performed on glass/glass photovoltaic (PV) modules. This combined numericalexperimental approach results in reliable models for designing structural timberglass façade elements with integrated photovoltaics.
The study further evaluates the effects of shear loads on the system’s
components. Eight diaphragm specimens (1.2 m × 1.2 m) are tested using two
different structural silicone adhesives, with and without a tie-down anchoring of the
leading stud. Various measurement techniques, including displacement sensors
(linear variable differential transformers or LVDTs), digital image correlation, fibre
Bragg gratings and strain gauges, are used to analyse component behaviour. The
specimens primarily failed due to adhesive rupture. Results show that anchoring
the wall with a tie-down increases the system’s racking stiffness by 30%. The
strains on the glass and solar cells are analysed during experimental in-plane shear
tests, confirming that the solar cells remain undamaged. Electroluminescence
testing verifies this finding.
Furthermore, an analytical design method based on Eurocode 5 (FprEN 1995-
1-1) and spring models is proposed and compared with the experimental results.
While this method tends to underestimate the wall elements’ stiffness, it accurately
predicts the minimum load-bearing capacity. Finally, a detailed finite element
model is developed and calibrated using small-scale connection tests. The
model closely matches experimental measurements in terms of strength and
stiffness. A parametric study assesses the influence of different aspect ratios,
glass thicknesses, adhesive bond dimensions, and other parameters.
Overall, this study demonstrates that glass can be structurally activated
to increase the stiffness of lightweight timber structures when bonded with
adhesives. This challenges the conventional assumption that glass openings
do not structurally contribute. Additionally, integrating photovoltaics into the
glass enables multifunctional façade elements. The findings confirm that, for
the tested specimens, standard solar cells withstand in-plane shear forces in
the glass without compromising structural performance. This research advances
the field by exploring innovative solutions to overcome current challenges in
timber frame design, offering a pathway toward more sustainable architecture
and structural engineering, and contributing to the development of next-generation
building systems that integrate both structural performance and renewable energy
generation
Experimental and analytical assessment of the combined in-plane bending-shear behavior of timber frame walls
No full textAs timber buildings grow taller, understanding the mechanical behavior and robustness of multi-story timber structures is increasingly important. In Europe, Eurocode 5 governs their design but offers little guidance for failure scenarios. In particular, it lacks provisions for diaphragm walls under combined bending and shear forces that can occur during events like wall loss. This study investigates the behavior of such walls through experimental and analytical methods. An experimental campaign was conducted using eleven timber frame walls with OSB sheathing, fastened with either screws or staples. Five walls underwent four-point bending tests, two were tested under shear, and four experienced combined bending-shear loading. In the latter, a vertical preload was applied before monotonic shear loading to failure. Walls fastened with staples showed ductile failure with significant yielding, whereas walls fastened with screws exhibited brittle failure via screw tear-out. Shear failures primarily occurred at sheathing-to-framing connections in the lower rail. Under combined loading, increased vertical preload reduced shear capacity, displacement at failure, and force at yielding. The experiments supported an analytical model developed to estimate in-plane bending strength and maximum allowable shear load in combined loading scenarios. The model conservatively predicted the behavior of walls fastened with screws in bending but overestimated the strength of walls fastened with staples. For combined loading, the model provided a conservative estimate of maximum shear resistance.The authors acknowledge the work of Jan Leuraers, Dan Dragan, and Ricky Pereira, who helped perform the experiments. Secondly, the authors gratefully thank the Special Research Fund (BOF) of Hasselt University, Belgium for supporting this research. BOF reference: BOF22OWB18
Experimental characterisation and calibration of hyperelastic material models for finite element modelling of timber-glass adhesive connections under shear and tensile loading
No full textThis work aims to characterise the behaviour of structural adhesives for timber-glass connections by performing experimental tests and calibrating numerical models. An adhesive bond between timber and glass can solve two conflicting requirements in timber frame structures.: (i) horizontal stability provided by shear walls/vertical diaphragms; (ii) large open spaces to maximize the flexibility of the building's use. One solution to this challenge is to increase the number of diaphragms in the timber frame building's façade, which can be achieved by structurally activating the glass panels. This, in turn, requires a strong structural bond between the timber and glass. Therefore, in this paper, experimental tensile and shear tests are performed on bonded timber-glass specimens comparing four two-component silicone and a one-component polyurethane adhesive. Special attention is put on the T. Engelen (B) · J. Henriques · B. Vandoren failure behaviour of the adhesives, where both cohesive failure and loss of adhesion were identified. The nonlinear stress-strain behaviour of these adhesives is evaluated and used to asses different hyperelastic material models. Two calibration methods are used to determine the model parameters of the hyperelastic material models. Simulations have shown that the first method, assuming uniaxial tension, was not suitable for the performed tensile tests. However, with the second method, using an inverse parameter fitting method, a better approximation was obtained. The results from this work can be used to model bonded timber-glass connections in larger structures more accurately.Funding This research is supported by the Special Research Fund (BOF) ofHasselt University with Project Number BOF21DOC17
Development and analysis of structural timber-glass façade systems with integrated photovoltaics
No full textThere is an increase in interest in timber as a material for the design of the load-bearing system of a building. At the same time, large glass façades are often desired in modern buildings. Additionally, the production of green energy is an increasingly important design principle for buildings. These three requirements can be combined in a structural timber-glass façade with integrated photovoltaics, which is the topic of this contribution. However, there is a lack of design rules for these systems. The timber-glass connection design is developed in this work to exploit the in-plane stiffness of the glass panel and increase the horizontal stability of the underlying timber structure. A detailed numerical model is validated with experimental tensile and shear tests on the connections. Additionally, the glass/glass photovoltaic elements are studied with a numerical model that predicts stresses and strains in the glass and the solar cells under various loading conditions. Experimental in-and out-of-plane bending tests are performed on glass/glass photovoltaic (PV) modules to validate the numerical results. With this combined numerical-experimental approach, reliable models are made that can be used for designing structural timber-glass façade elements with integrated photovoltaics
Experimental and analytical characterisation of hybrid timber-glass diaphragms with integrated photovoltaics
No full textThis study investigates the structural performance of hybrid timber-glass frame walls designed to enhance racking resistance in façades, with a specific focus on the integration of photovoltaic solar cells within structural glass elements. The effects of shear loads on the system’s components and the applicability of analytical design methods are evaluated. To achieve this, eight diaphragms (1.2 × 1.2 m) were tested under in-plane shear loading using two different structural silicone adhesives, with or without a tie-down anchoring of the leading stud. A variety of measurement techniques, including displacement sensors (LVDTs), digital image correlation, fibre Bragg gratings and strain gauges were simultaneously employed to analyse the behaviour of the different components. The specimens primarily failed due to adhesive rupture. It is shown that adding wall anchorage increases the system’s racking stiffness by 30%. This study offers insights into the strains measured on the glass and solar cells during mechanical in-plane shear load tests. Furthermore, an analytical design method based on the relevant Eurocode (prEN 1995-1-1) and spring models is proposed and compared with the experimental results. The findings reveal that while this method tends to underestimate the stiffness of the wall elements, it provides an accurate prediction of the minimum load-bearing capacity.The authors acknowledge the work of Dan Dragan and Niels Blocken who performed the experiments on the different diaphragm configurations. Secondly, the authors gratefully thank the Special Research Fund (BOF) of Hasselt University for supporting this research with project Number BOF21DOC17. Special thanks go to Dow Silicones Belgium SPRL, particularly Valerie Hayez and the involved laboratory members, for their assistance in specimen production and technical support. Appreciation is also extended to Kömmerling Chemische Fabrik GMBH, notably Christian Scherer and his colleagues, for their engaging discussions and assistance with specimen production. The authors are also thankful to Soltech NV and Tatjana Vavilkin for their contributions to solar panel production, along with DUPAC NV for providing the necessary timber. Additionally, they recognise the experimental efforts of Jasper van Berlo and Ruben Wagemans related to their master’s thesis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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