1,721,200 research outputs found
Performance-based adaptive steplength control of path-following methods for solving quasi-static problems
No full textIn a quasi-static nonlinear structural problem, the complete solution curve with all snapbacks and snap-throughs is usually of interest. Path-following methods are powerful and
widely used numerical tools to robustly find this curve. Essentially, the method adds an
extra equation, called a constraint function, to the system of equilibrium equations in
order to control the solution procedure. This function needs a step-length to be specified
once before an analysis starts or in each analysis increment. The latter one is called
an adaptive step-length which requires a law for its evolution. Conventionally, the ratio
between a desired number of iterations per increment over a previously converged one is
used for the adaptation [1, 2]. We have firstly defined criteria to assess the performance
of the path-following method and secondly proposed an adaptation law based on them.
Two example problems of damage analysis of structures are solved by the new as well
as the mentioned conventional law. The results show that the proposed adaptation law
performs better than the conventional one in terms of the performance criteria
Experimental and analytical assessment of the racking behavior of timber frame walls with single-sided double-layered sheathing panels
No full textIn lightweight timber frame buildings, the horizontal stability against, for instance, wind loads is mainly ensured by shear diaphragms. These shear walls are typically constructed using a timber frame and a load- bearing sheathing layer on one or both sides of the framework. An atypical construction method uses double sheathing panels on top of each other, e.g. because of acoustic or fire safety reasons. However, no design rules are provided for such structures: the respective current and upcoming European standard (Eurocode 5 part 1-1) does not consider the structural contribution of both sheathing panel layers. Therefore, in this study, an experimental campaign is performed to enhance the knowledge of such double-sheathed shear walls, and two analytical calculation methods are proposed. The experimental campaign tests eight full-scale configurations through a racking resistance test with monotonic loading. Sheathing materials include load-bearing and non- load-bearing gypsum plasterboards and resinoid-bonded particle boards. All sheathing panels are connected to the fully anchored frames using staples. Results demonstrate that adding a second sheathing layer of the same material, with the same fastener disposition as the inner layer does not fully double the racking capacity and racking stiffness. Secondly, using a non-load-bearing gypsum plate as the inner layer creates a long plateau phase at the post-peak loading response, producing a less brittle failure behavior. The experiments are used as a benchmark to develop an analytical model based on Bla ss and Gebhardt's method for calculating the shear capacity of dowel-type connections with an interlayer. The proposed method introduces an interaction factor that takes into account that the connections of the outer sheathing layer, which pass through the inner sheathing layer, also contribute to the sheathing-to-framing connection of the latter. A simplified model is also presented, using a combination factor that aligns with the current Eurocode 5 design method for walls with sheathing panels on both sides of the framing. Different values for the respective interaction and combination factors are verified to determine a safe value for each tested configuration.The authors acknowledge the work of Jan Leuraers, Dan Dragan, and Frederick Truyers, who performed the experiments on the different wall configurations. Secondly, the authors gratefully thank VLAIO (Flanders Innovation & Entrepreneurship) for financing this research and Special Research Fund (BOF) of Hasselt University for supporting this research. VLAIO reference: HBC.2020.2098; BOF reference: BOF22OWB18
Mesoscopic modelling of masonry using weak discontinuities in the partition of unity framework
No full textModelling of masonry has been a popular topic within computational mechanics for some years now. Three major groups of modelling approaches exist: macroscopic, mesoscopic and microscopic. In this contribution a two dimensional mesoscopic model will be developed, in which mortar joints are modelled by embedded discontinuities using the partition of unity property of the finite element shape functions.
Unlike classical mesoscopic models, where joints are modelled using strong discontinuities (i.e. jumps in the displacement field), the model developed in this PhD research uses weak discontinuities. A weak discontinuity introduces a jump in the strain field, allowing for failure to localise in a zone with finite width. The thickness of this failure is in this case linked to the joint thickness. An advantage of this weak discontinuity approach is that the constitutive modelling can be performed in the general stress and strain spaces.
A local damage model is used to describe the non-linear behaviour of the discontinuities. The global equilibrium path is traced using an energy release constraint function. Both governing equations and algorithmic aspects will be discussed. The performance of the developed masonry model will be demonstrated by the simulation and validation of three-point-bending tests and shear wall analysis
Efficiency and accuracy of a multiscale domain activation approach for modeling masonry failure
No full textMasonry is a composite consisting of two very different materials, which results in complex structural behavior. There exist accurate models in which both constituents are modeled explicitly, such as microscale and mesoscale models, but they require a great amount of computational resources. A faster, alternative, strategy to model masonry structures is the use of macroscale models, where homogenized elements are used which condense constituent behavior into one composite material. This approach also removes the upper bound on finite element sizes, which can lead to a reduction in element numbers. However, using one single material type makes it hard to capture the inherent nonlinear behavior when simulating masonry failure. In order to find a compromise between accuracy and computational efficiency one can use a scale embedding multiscale model where both macro- and microscale elements come into play, combining the advantages both have to offer. In this work a finite element based framework that formulates an adaptive scale embedding multiscale technique is presented, with the goal of both accurately and efficiently simulating large masonry structures. This theory is tested and compared to show its accuracy to rival a fully microscale model, while at the same time comparatively having a higher computational efficiency. In this work, the developed multiscale model is compared to its underlying microscale model using a couple example structures, ranging from small to large scale 2D unreinforced masonry walls with openings, including an application related to failure due to soil settlement, showing a potential for the application of this type of modeling
Earthquake resisting potential of an innovative HCW system with laser-cut open-to-CHS connections
No full textAlthough conventional reinforced concrete (RC) or hybrid coupled wall (HCW) structures have been used for a number of years as seismic resistant system thanks to their lateral strength, stiffness, and energy dissipation characteristics, some drawbacks such as expensive detailing, costly foundations, heavy superstructure, difficult restoration works etc. have limited their potential from a structural and an economic perspective. To minimize these drawbacks and make further advancement, an innovative HCW system is proposed in this study consisting of a single RC wall coupled with two steel circular hollow section (CHS) columns via steel coupling links. The RC wall carries almost all the horizontal shear force while the overturning moments are partially resisted by an axial compression-tension couple developed by the two CHS columns rather than by the individual flexural action of the wall alone. The primary objective in designing this system is ensuring a "fuse"-like behaviour of the steel coupling links, i.e. concentrating the seismic damage in the coupling links while avoiding any damage in the RC wall as well as in the connections between the links and the primary vertical elements (RC wall and CHS column). Multiple case studies with varying coupling ratios are investigated through nonlinear pushover analyses to verify the above-mentioned design objective. Different configurations are proposed to achieve an efficient link-to-RC wall composite connection, which can ensure the "fuse"-like behaviour of the coupling link. The steel coupling links are connected to a steel profile either partly embedded in the RC wall or passing through it. The connection zone is designed in such a way that the damage always occurs in the steel links (fuses) prior to any damage in the RC wall in general and in the connection zone in particular. Case studies have therefore been designed based on the force demands obtained from the global structure and further examined through detailed pushover analyses to highlight their applicability in the HCW systems. A suitable link-to-CHS column connection is also necessary to ensure the "fuse"-like behaviour of the coupling links. However, the conventional open-to-CHS column connections, with beams (or links) directly welded on the tube, are often prone to severe local distortion of the CHS column surface, premature flange fractures and excessive welding quantity. To avoid such limitations, this paper introduces different types of innovative I-beam-to-CHS-column "passing-through" connections. These connections consist of coupling links connected to an I-beam stub (or vertical and horizontal plates) entering the CHS column through laser-cut slots. Standard design guidelines have been developed in accordance with Eurocode provisions for gravitational and seismic loading scenarios to calculate the ultimate joint resistances. Case studies have therefore been designed based on the global demands and further examined through detailed pushover analyses in order to validate their compatibility to the HCW systems. Based on the design case studies, the primary design objective was achieved in both cases-the global and local perspective. Yielding was attained in the coupling links prior to any damage in the RC wall, CHS columns, and the connections. Encouraging validations are therefore presented regarding the earthquake resistant potential of the HCW system and the applicability of the innovative connections
Impacts of load distribution and lane width on pavement rutting performance for automated vehicles
No full textOver the recent years, considerable attention has been drawn to intelligent driving technologies and particularly to automated vehicles (AVs). The deployment of AVs would provide the opportunity to have more control over the dynamics of the vehicle, including its lateral movement, which can affect the pavement’s long-term rutting performance. The controlled lateral movement of the AVs may also imply a reduced lane width. This paper evaluates the impacts of dedicating a reduced lane width to AVs on pavement rutting performance, considering two lateral movement modes for AVs; zero wander and uniform-wander. A finite element model was developed using ABAQUS software. The rutting simulation results of this study showed that the abrupt changes in the loading schemes of the zero- and uniform-wander modes cause considerable accumulated rutting in the edges of the loading areas. This is significantly greater than the total rutting induced by the human-driven vehicles (HDVs) following the normal-wander mode, which causes a compensated rutting behaviour by a gradual increase in loading time. Furthermore, the comparison between rutting depths in different lane widths reveals that when dedicating the narrower lane for AVs with a uniform-wander distribution, the pavement’s total rutting depth would remarkably increase compared to the wider lanes.This study was supported by the Special Research Fund (BOF) of Hasselt University with the BOF number of “BOF19OWB26”
Comparison of equivalent beam models and refined approaches for the modelling of masonry portal frames
No full textThe recent evolutions in the analysis and design of masonry structures tend to let consider these structures at the same level as the more traditionally engineered materials, namely steel and concrete, as far as it comes to the refinement of the analysis and of the control of the failure modes in the framework of a limit-state design approach. Such an evolution comes together with the development of reliable analysis tools. In this context, the most promising approach whose use could reasonably be generalized in regular design offices for the analysis of full buildings is the use of equivalent beams to model walls and spandrels, resulting in a global frame modelling approach of entire structures. Such models need however to be properly calibrated regarding a large number of aspects such as deformation properties, resistance models, behaviour of the nodes, lintels, spandrels... The proposed paper aims at illustrating such a calibration process. It starts from experimental results achieved at the University of Liege on small clay masonry structures made of two walls connected by a spandrel, with a RC lintel over the door opening and a RC beam emulating the presence of a concrete slab at the first floor level. The tests specimens are then modelled using a refined finite element approach and compared with a frame modelling considering the vertical and horizontal structural elements as equivalent columns and beams
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
Time-dependent mesoscopic modelling of masonry using embedded weak discontinuities
No full textIn this contribution, a rate-dependent mesoscopic masonry model is presented
in which the mortar joints are incorporated by embedded weak discontinuities based on
partitions of unity. Within the discontinuities, both an isotropic damage and a Perzyna
viscoplastic model are used to describe joint degradation. The elastic domain of the joint
behaviour is bounded by a modi ed Drucker-Prager yield function. The performance of
the developed masonry model is demonstrated by the simulation of a three-point bending
test and a shear wall test.BOF-DOC Hasselt Universit
Time-dependent mesoscopic modelling of masonry using embedded weak discontinuities
No full textIn this contribution, a rate-dependent mesoscopic masonry model is presented
in which the mortar joints are incorporated by embedded weak discontinuities based on
partitions of unity. Within the discontinuities, both an isotropic damage and a Perzyna
viscoplastic model are used to describe joint degradation. The elastic domain of the joint
behaviour is bounded by a modi ed Drucker-Prager yield function. The performance of
the developed masonry model is demonstrated by the simulation of a three-point bending
test and a shear wall test.BOF-DOC Hasselt Universit
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