Artikler, rapporter og annet (datateknologi og beregningsorienterte ingeniørfag)https://hdl.handle.net/10037/83742019-06-17T22:53:44Z2019-06-17T22:53:44ZAtomized feedback, an approach to automatic formative assessmentSteen, ArildMovik, Hans Richardhttps://hdl.handle.net/10037/152622019-05-07T12:45:31Z2017-11-01T00:00:00ZSteen, Arild; Movik, Hans Richard<br />
In this article, we describe an approach to give automatic formative evaluation by atomizing the
feedback. The mechanics in this approach is a large number of multiple-choice tests. The multiplechoice tests are used as voluntary assignments and gives controlled progression by releasing the
tests in an order. Instruction is in the spirit of flipped classroom with short video lectures accompanied
by one to several above-mentioned assignments. The preliminary results show reduced dropout,
higher student satisfaction, and less fail on final exam.
The background for this approach submerged from a multi-campus/online course with 300+ students.
The aim was to create the same environment for learning for all categories of students, on campus,
remote campus and online students.
Atomized formative evaluation is achieved by giving feedback down to each individual multiple-choice
answer. The multiple-choice questions are in the nature of practical tasks where students are
expected to use external tools, calculations and simulation to find answers. The multiple-choice test
collects the students’ findings. The number of correct answer gives a summative evaluation. After
turning in the test, answers are available together with feedback for each answer. Correct answers
explain why this is correct and a wrong answer explains why this is wrong in addition to how and why
the student should go by finding the correct answer. The questions are designed with no “dummy”
answer, so when choosing a wrong answer, it is a plausible answer, and an explanation for this is
given as feedback.
The goal is to encourage the student to try again both to improve the summative score and to fill the
gap in knowledge. When forming the feedback, one must consider both the type of question and the
choices made available.
Using atomized feedback improves the formative evaluation greatly by being instant, continuous, to
the point and informative. This is evaluation for learning that both guides and encourage the student.
In addition, since instructors/TA do not use time to evaluate results on assignments, they can guide /
tutor individual students who need follow up.
Student performance is evaluated by achieved grade, student satisfaction, progression, and the
number of assignments compared to grade. The preliminary findings compared with earlier student
performance in the same course but without atomized formative feedback show a reduced number of
dropouts and reduced number of students failing the final exam.<br />
Accepted manuscript version, published version available at:<a href=http://dx.doi.org/10.21125/iceri.2017.1368>http://dx.doi.org/10.21125/iceri.2017.1368</a><br />
2017-11-01T00:00:00ZAtomized feedback, an approach to automatic formative assessmentSteen, ArildMovik, Hans RichardIn this article, we describe an approach to give automatic formative evaluation by atomizing the
feedback. The mechanics in this approach is a large number of multiple-choice tests. The multiplechoice tests are used as voluntary assignments and gives controlled progression by releasing the
tests in an order. Instruction is in the spirit of flipped classroom with short video lectures accompanied
by one to several above-mentioned assignments. The preliminary results show reduced dropout,
higher student satisfaction, and less fail on final exam.
The background for this approach submerged from a multi-campus/online course with 300+ students.
The aim was to create the same environment for learning for all categories of students, on campus,
remote campus and online students.
Atomized formative evaluation is achieved by giving feedback down to each individual multiple-choice
answer. The multiple-choice questions are in the nature of practical tasks where students are
expected to use external tools, calculations and simulation to find answers. The multiple-choice test
collects the students’ findings. The number of correct answer gives a summative evaluation. After
turning in the test, answers are available together with feedback for each answer. Correct answers
explain why this is correct and a wrong answer explains why this is wrong in addition to how and why
the student should go by finding the correct answer. The questions are designed with no “dummy”
answer, so when choosing a wrong answer, it is a plausible answer, and an explanation for this is
given as feedback.
The goal is to encourage the student to try again both to improve the summative score and to fill the
gap in knowledge. When forming the feedback, one must consider both the type of question and the
choices made available.
Using atomized feedback improves the formative evaluation greatly by being instant, continuous, to
the point and informative. This is evaluation for learning that both guides and encourage the student.
In addition, since instructors/TA do not use time to evaluate results on assignments, they can guide /
tutor individual students who need follow up.
Student performance is evaluated by achieved grade, student satisfaction, progression, and the
number of assignments compared to grade. The preliminary findings compared with earlier student
performance in the same course but without atomized formative feedback show a reduced number of
dropouts and reduced number of students failing the final exam.IATED (International Academy of Technology, Education and Development)Peer reviewedChapterSteen, A., Movik, H.R. (2017) Atomized feedback, an approach to automatic formative assessment. I L. Gómez Chova, A. López Martínez & I. Candel Torres (red). <i> Proceedings of ICERI 2017 Conference.</i> (s. 5206-5214). Sevilla : The International Academy of Technology, Education and Development. http://dx.doi.org/10.21125/iceri.2017.1368Rescue of stranded persons. C18. Rescue of stranded passengers in the ArcticMeidell, AnnetteOlsen, Stevehttps://hdl.handle.net/10037/152512019-05-03T12:00:31Z2018-12-01T00:00:00ZMeidell, Annette; Olsen, Steve<br />
Since we (the authors) could not be a part of the whole SARex 3 exercise this year, we joined the
expedition later than the rest of the participants. We gladly accepted the invitation from the Governor
of Svalbard, Kjerstin Askholt, and her staff in Longyearbyen to join their service vessel, MS Polarsyssel,
to meet The Norwegian Coast Guard’s vessel, (NOCGV) Svalbard, at the location where the last part
of the SARex expedition would take place. MS Polarsyssel and the Governor of Svalbard’s staff would
this year participate in this last part of the SARex 3 exercise with the aim to prepare and handle the
situation of a large number of stranded passengers in the Arctic. In this part of SARex 3 exercise, the
rescue group from Longyearbyen Red Cross would also participate and practice in this search and rescue
(SAR) exercise; see [1]. The governor of Svalbard is both the chief of police and accorded the same
authority as a county governor on the mainland. Rescue service is one of the governor’s tasks, and the
governor normally leads all rescue missions in Svalbard. The Joint Rescue Coordination Center (JRCC)
North in Bodø has the overall operational responsibility during search and rescue operations north of
65 degrees north. The operations are coordinated either directly from JRCC North or through the
Governor of Svalbard. For more information concerning this, see [2].
This report will focus on the search and rescue (SAR) exercise from the point of view of the “late
arrivers” (as we were called throughout the rest of the SARex 3 expedition)<br />
Published version, available at <a href= http://hdl.handle.net/11250/2578301>http://hdl.handle.net/11250/2578301</a><br />
2018-12-01T00:00:00ZRescue of stranded persons. C18. Rescue of stranded passengers in the ArcticMeidell, AnnetteOlsen, SteveSince we (the authors) could not be a part of the whole SARex 3 exercise this year, we joined the
expedition later than the rest of the participants. We gladly accepted the invitation from the Governor
of Svalbard, Kjerstin Askholt, and her staff in Longyearbyen to join their service vessel, MS Polarsyssel,
to meet The Norwegian Coast Guard’s vessel, (NOCGV) Svalbard, at the location where the last part
of the SARex expedition would take place. MS Polarsyssel and the Governor of Svalbard’s staff would
this year participate in this last part of the SARex 3 exercise with the aim to prepare and handle the
situation of a large number of stranded passengers in the Arctic. In this part of SARex 3 exercise, the
rescue group from Longyearbyen Red Cross would also participate and practice in this search and rescue
(SAR) exercise; see [1]. The governor of Svalbard is both the chief of police and accorded the same
authority as a county governor on the mainland. Rescue service is one of the governor’s tasks, and the
governor normally leads all rescue missions in Svalbard. The Joint Rescue Coordination Center (JRCC)
North in Bodø has the overall operational responsibility during search and rescue operations north of
65 degrees north. The operations are coordinated either directly from JRCC North or through the
Governor of Svalbard. For more information concerning this, see [2].
This report will focus on the search and rescue (SAR) exercise from the point of view of the “late
arrivers” (as we were called throughout the rest of the SARex 3 expedition)Universitetet i StavangerForskningsrapportChapterMeidell, A.; Olsen,S. (2018) Rescue of stranded persons. C18. Rescue of stranded passengers in the Arctic. I Solberg, K.E.; Gudmestad, O.T. (red) <i> SARex3: Evacuation to shore, survival and rescue, 2018</i>, (203-214). Stavanger : Universitetet i Stavanger.On geometric construction of some power meansHøibakk, RalphLukkassen, DagPersson, Lars ErikMeidell, Annettehttps://hdl.handle.net/10037/152492019-05-16T13:30:39Z2018-11-27T00:00:00ZHøibakk, Ralph; Lukkassen, Dag; Persson, Lars Erik; Meidell, Annette<br />
In the homogenization theory, there are many examples where the effective conductivities of composite structures are power means of the local conductivities. The main aim of this paper is to initiate research concerning geometric construction of some power means of three or more variables. We contribute by giving methods for the geometric construction of the harmonic mean $ P_{-1} $ and the arithmetic mean $P_{1}$ of three variables $a,b$ and $c$<br />
Submitted manuscript version. Published version available at: <a href=http://www.nonlinearstudies.com/index.php/nonlinear/article/view/1811>http://www.nonlinearstudies.com/index.php/nonlinear/article/view/1811</a><br />
2018-11-27T00:00:00ZOn geometric construction of some power meansHøibakk, RalphLukkassen, DagPersson, Lars ErikMeidell, AnnetteIn the homogenization theory, there are many examples where the effective conductivities of composite structures are power means of the local conductivities. The main aim of this paper is to initiate research concerning geometric construction of some power means of three or more variables. We contribute by giving methods for the geometric construction of the harmonic mean $ P_{-1} $ and the arithmetic mean $P_{1}$ of three variables $a,b$ and $c$Cambridge ScientificJournal articlePeer reviewedHøibakk, R,; Lukkassen D.; Persson, L.E.; Meidell, A. (2018) On geometric construction of some power means. <i>Nonlinear Studies, 25</i>(4), 921-932. Hentet fra http://www.nonlinearstudies.com/index.php/nonlinear/article/view/1811Nonlinear StudiesA sharp boundedness result for restricted maximal operators of Vilenkin-Fourier series on martingale Hardy spacesBlahota, IstvanNagy, KarolyPersson, Lars ErikTephnadze, Georgehttps://hdl.handle.net/10037/151832019-04-09T13:31:07Z2018-09-20T00:00:00ZBlahota, Istvan; Nagy, Karoly; Persson, Lars Erik; Tephnadze, George<br />
The restricted maximal operators of partial sums with respect to bounded Vilenkin systems are investigated. We derive the maximal subspace of positive numbers, for which this operator is bounded from the Hardy space
H
p
to the Lebesgue space
L
p
for all
0<p≤1
. We also prove that the result is sharp in a particular sense.<br />
Accepted manuscript file, 12 months embargo. Published version available at: <a href=https://doi.org/10.1515/gmj-2018-0045>https://doi.org/10.1515/gmj-2018-0045</a><br />
2018-09-20T00:00:00ZA sharp boundedness result for restricted maximal operators of Vilenkin-Fourier series on martingale Hardy spacesBlahota, IstvanNagy, KarolyPersson, Lars ErikTephnadze, GeorgeThe restricted maximal operators of partial sums with respect to bounded Vilenkin systems are investigated. We derive the maximal subspace of positive numbers, for which this operator is bounded from the Hardy space
H
p
to the Lebesgue space
L
p
for all
0<p≤1
. We also prove that the result is sharp in a particular sense.De GruyterJournal articlePeer reviewedBlahota, I., Nagy,K., Persson, L.E., Tephnadze, G. A sharp boundedness result for restricted maximal operators of Vilenkin-Fourier series on martingale Hardy spaces. <i>Georgian Mathematical Journal, 2018,</i> 10 s. https://doi.org/10.1515/gmj-2018-0045.Georgian Mathematical JournalResolvent bounds for jump generatorsKondratiev, YuriMolchanov, StanislavPiatnitski, AndreyZhizhina, Elenahttps://hdl.handle.net/10037/150172019-03-19T11:59:30Z2016-12-02T00:00:00ZKondratiev, Yuri; Molchanov, Stanislav; Piatnitski, Andrey; Zhizhina, Elena<br />
The paper deals with jump generators with a convolution kernel. Assuming that the kernel decays either exponentially or polynomially, we prove a number of lower and upper bounds for the resolvent of such operators. In particular we focus on sharp estimates of the resolvent kernel for small values of the spectral parameter. We consider two applications of these results. First we obtain pointwise estimates for principal eigenfunction of jump generators perturbed by a compactly supported potential (so-called nonlocal Schrödinger operators). Then we consider the Cauchy problem for the corresponding inhomogeneous evolution equations and study the behaviourofitssolutions.<br />
This is an Accepted Manuscript of an article published by Taylor & Francis in <i>Applicable Analysis</i> on 02/12/2016, available online: <a href= https://doi.org/10.1080/00036811.2016.1263838> https://doi.org/10.1080/00036811.2016.1263838.</a><br />
2016-12-02T00:00:00ZResolvent bounds for jump generatorsKondratiev, YuriMolchanov, StanislavPiatnitski, AndreyZhizhina, ElenaThe paper deals with jump generators with a convolution kernel. Assuming that the kernel decays either exponentially or polynomially, we prove a number of lower and upper bounds for the resolvent of such operators. In particular we focus on sharp estimates of the resolvent kernel for small values of the spectral parameter. We consider two applications of these results. First we obtain pointwise estimates for principal eigenfunction of jump generators perturbed by a compactly supported potential (so-called nonlocal Schrödinger operators). Then we consider the Cauchy problem for the corresponding inhomogeneous evolution equations and study the behaviourofitssolutions.Taylor & Francis GroupJournal articlePeer reviewedTidsskriftartikkelKondratiev, Y., Molchanov, S., Piatnitski, A. & Zhizhina, E. (2018). Resolvent bounds for jump generators. <i>Applicable Analysis, 97</i>(3), 323-336. <p>https://doi.org/10.1080/00036811.2016.1263838Applicable AnalysisHomogenization of nonisothermal immiscible incompressible two-phase flow in porous mediaAmaziane, BrahimJurak, MuratPankratov, LeonidPiatnitski, Andreyhttps://hdl.handle.net/10037/149952019-03-18T09:31:08Z2018-03-15T00:00:00ZAmaziane, Brahim; Jurak, Murat; Pankratov, Leonid; Piatnitski, Andrey<br />
In this paper, we consider nonisothermal two-phase flows through heterogeneous porous media with periodic microstructure. Examples of such models appear in gas migration through engineered and geological barriers for a deep repository for radioactive waste, thermally enhanced oil recovery and geothermal systems. The mathematical model is given by a coupled system of two-phase flow equations, and an energy balance equation. The model consists of the usual equations derived from the mass conservation of both fluids along with the Darcy–Muskat and the capillary pressure laws. The problem is written in terms of the phase formulation, i.e. the saturation of one phase, the pressure of the second phase and the temperature are primary unknowns. The major difficulties related to this model are in the nonlinear degenerate structure of the equations, as well as in the coupling in the system. As fluid properties are defined as a function of temperature and pressure, there is a strong coupling between the mass balance and energy balance equations. Under some realistic assumptions on the data, we obtain a nonlinear homogenized coupled system of three coupled partial differential equations with effective coefficients (porosity, permeability, thermal conductivity, heat capacity) which are computed via solving cell problems. We give a rigorous mathematical derivation of the upscaled model by means of the two-scale convergence.<br />
Accepted manuscript version, 24 months embargo. Published version at: <a href=https://doi.org/10.1016/j.nonrwa.2018.02.012>https://doi.org/10.1016/j.nonrwa.2018.02.012</a><p>This manuscript version is made available under the <a href=http://creativecommons.org/licenses/by-nc-nd/4.0/>CC-BY-NC-ND 4.0 license</a><br />
2018-03-15T00:00:00ZHomogenization of nonisothermal immiscible incompressible two-phase flow in porous mediaAmaziane, BrahimJurak, MuratPankratov, LeonidPiatnitski, AndreyIn this paper, we consider nonisothermal two-phase flows through heterogeneous porous media with periodic microstructure. Examples of such models appear in gas migration through engineered and geological barriers for a deep repository for radioactive waste, thermally enhanced oil recovery and geothermal systems. The mathematical model is given by a coupled system of two-phase flow equations, and an energy balance equation. The model consists of the usual equations derived from the mass conservation of both fluids along with the Darcy–Muskat and the capillary pressure laws. The problem is written in terms of the phase formulation, i.e. the saturation of one phase, the pressure of the second phase and the temperature are primary unknowns. The major difficulties related to this model are in the nonlinear degenerate structure of the equations, as well as in the coupling in the system. As fluid properties are defined as a function of temperature and pressure, there is a strong coupling between the mass balance and energy balance equations. Under some realistic assumptions on the data, we obtain a nonlinear homogenized coupled system of three coupled partial differential equations with effective coefficients (porosity, permeability, thermal conductivity, heat capacity) which are computed via solving cell problems. We give a rigorous mathematical derivation of the upscaled model by means of the two-scale convergence.ElsevierJournal articlePeer reviewedAmaziane, B., Jurak, M., Pankratov, L., Piatnitski, A. (2018) Homogenization of nonisothermal immiscible incompressible two-phase flow in porous media.<i>Nonlinear Analysis: Real world applications. 43</i> October,192-212. https://doi.org/10.1016/j.nonrwa.2018.02.012Nonlinear Analysis: Real world applicationshttps://www.sciencedirect.com/science/article/pii/S1468121818301688?via%3DihubAsymptotic Behaviour of Ground States for Mixtures of Ferromagnetic and Antiferromagnetic Interactions in a Dilute RegimeBraides, AndreaCausin, AndreaPiatnitski, AndreySolci, Margheritahttps://hdl.handle.net/10037/149892019-03-19T12:15:27Z2018-04-30T00:00:00ZBraides, Andrea; Causin, Andrea; Piatnitski, Andrey; Solci, Margherita<br />
We consider randomly distributed mixtures of bonds of ferromagnetic and antiferromagnetic type in a two-dimensional square lattice with probability
1−p
1−p
and p, respectively, according to an i.i.d. random variable. We study minimizers of the corresponding nearest-neighbour spin energy on large domains in
Z
2
Z2
. We prove that there exists
p
0
p0
such that for
p≤
p
0
p≤p0
such minimizers are characterized by a majority phase; i.e., they take identically the value 1 or
−1
−1
except for small disconnected sets. A deterministic analogue is also proved.<br />
Accepted manuscript version, 12 months embargo. Published version at: <a href=https://doi.org/10.1007/s10955-018-2051-8>https://doi.org/10.1007/s10955-018-2051-8</a><br />
2018-04-30T00:00:00ZAsymptotic Behaviour of Ground States for Mixtures of Ferromagnetic and Antiferromagnetic Interactions in a Dilute RegimeBraides, AndreaCausin, AndreaPiatnitski, AndreySolci, MargheritaWe consider randomly distributed mixtures of bonds of ferromagnetic and antiferromagnetic type in a two-dimensional square lattice with probability
1−p
1−p
and p, respectively, according to an i.i.d. random variable. We study minimizers of the corresponding nearest-neighbour spin energy on large domains in
Z
2
Z2
. We prove that there exists
p
0
p0
such that for
p≤
p
0
p≤p0
such minimizers are characterized by a majority phase; i.e., they take identically the value 1 or
−1
−1
except for small disconnected sets. A deterministic analogue is also proved.Springer NatureJournal articlePeer reviewedBraides A., Causin,A., Piatnitski, A, Solci, M.(2018) Asymptotic Behaviour of Ground States for Mixtures of Ferromagnetic and Antiferromagnetic Interactions in a Dilute Regime.<i> Journal of statistical physics,171</i>(6),1096-1111. https://doi.org/10.1007/s10955-018-2051-8Journal of statistical physicsSteady States, Fluctuation-Dissipation Theorems and Homogenization for Reversible Diffusions in a Random EnvironmentMathieu, PPiatnitski, Ahttps://hdl.handle.net/10037/149882019-03-19T12:21:34Z2018-04-02T00:00:00ZMathieu, P; Piatnitski, A<br />
Prolongating our previous paper on the Einstein relation, we study the motion of a particle diffusing in a random reversible environment when subject to a small external forcing. In order to describe the long time behavior of the particle, we introduce the notions of steady state and weak steady state. We establish the continuity of weak steady states for an ergodic and uniformly elliptic environment. When the environment has finite range of dependence, we prove the existence of the steady state and weak steady state and compute its derivative at a vanishing force. Thus we obtain a complete ‘fluctuation–dissipation Theorem’ in this context as well as the continuity of the effective variance.<br />
Accepted manuscript version. Published version available at <a href=https://doi.org/10.1007/s00205-018-1245-1>https://doi.org/10.1007/s00205-018-1245-1.</a><br />
2018-04-02T00:00:00ZSteady States, Fluctuation-Dissipation Theorems and Homogenization for Reversible Diffusions in a Random EnvironmentMathieu, PPiatnitski, AProlongating our previous paper on the Einstein relation, we study the motion of a particle diffusing in a random reversible environment when subject to a small external forcing. In order to describe the long time behavior of the particle, we introduce the notions of steady state and weak steady state. We establish the continuity of weak steady states for an ergodic and uniformly elliptic environment. When the environment has finite range of dependence, we prove the existence of the steady state and weak steady state and compute its derivative at a vanishing force. Thus we obtain a complete ‘fluctuation–dissipation Theorem’ in this context as well as the continuity of the effective variance.Springer NatureJournal articlePeer reviewedTidsskriftartikkelMathieu, P. & Piatnitski, A. (2018). Steady States, Fluctuation-Dissipation Theorems and Homogenization for Reversible Diffusions in a Random Environment. <i>Archive for Rational Mechanics and Analysis, 230</i>(1), 277-320. http://dx.doi.org/10.1007/s00205-018-1245-1Archive for Rational Mechanics and Analysishttps://link.springer.com/article/10.1007%2Fs00205-018-1245-1Pointwise estimates for heat kernels of convolution-type operatorsGrigor'yan, AlexanderKondratiev, YuriPiatnitski, AndreyZhizhina, Elenahttps://hdl.handle.net/10037/149672019-03-19T12:31:07Z2018-04-16T00:00:00ZGrigor'yan, Alexander; Kondratiev, Yuri; Piatnitski, Andrey; Zhizhina, Elena<br />
We study the large‐time behaviour of the fundamental solution of parabolic equations with an elliptic part being non‐local convolution‐type operator. We assume that this operator is a generator of a Markov jump process, and that its convolution kernel decays at least exponentially at infinity. The fundamental solution shows rather different asymptotic behaviour depending on whether | x | ≲ t , or t ≪ | x | ≪ t , or | x | ∼ t , or | x | ≫ t . In each of these regions we obtain sharp pointwise estimates for the fundamental solution.<br />
Accepted manuscript version, Published version at: <a href=https://doi.org/10.1112/plms.12144>https://doi.org/10.1112/plms.12144. </a><br />
2018-04-16T00:00:00ZPointwise estimates for heat kernels of convolution-type operatorsGrigor'yan, AlexanderKondratiev, YuriPiatnitski, AndreyZhizhina, ElenaWe study the large‐time behaviour of the fundamental solution of parabolic equations with an elliptic part being non‐local convolution‐type operator. We assume that this operator is a generator of a Markov jump process, and that its convolution kernel decays at least exponentially at infinity. The fundamental solution shows rather different asymptotic behaviour depending on whether | x | ≲ t , or t ≪ | x | ≪ t , or | x | ∼ t , or | x | ≫ t . In each of these regions we obtain sharp pointwise estimates for the fundamental solution.London Mathematical SocietyJournal articlePeer reviewedTidsskriftartikkelGrigor'yan, A., Kondratiev, Y., Piatnitski A. & Zhizhina, E. (2018). Pointwise estimates for heat kernels of convolution-type operators. <i>Proceedings of the London Mathematical Society, 117</i>(4), 849-880. https://doi.org/10.1112/plms.12144>https://doi.org/10.1112/plms.12144 </a>Proceedings of the London Mathematical SocietyDynamic plastic response of beams subjected to localised pulse loadsThil, NicolasMehreganian, NavidMoatamedi, MojtabaLouca, Luke A.Soleiman Fallah, Arashhttps://hdl.handle.net/10037/149542019-03-12T13:31:10Z2018-10-31T00:00:00ZThil, Nicolas; Mehreganian, Navid; Moatamedi, Mojtaba; Louca, Luke A.; Soleiman Fallah, Arash<br />
Localised blast loads give rise to high gradients of overpressure detrimental to structural elements as beams and plates. This article presents an analytical study on the dynamic plastic response of beams made of a ductile metallic material due to close-in pulse pressure loading. The close-in pressure load is characterised by a spatially varying function constant over a central region and exponentially decaying beyond it. The temporal pulse shape is assumed to take different forms. The exact static plastic collapse load was obtained for the characteristic load using the framework of plastic limit analysis, whereby the analysis was then extended to the dynamic case by considering the appropriate yield surface and inclusion of inertia forces. The yield surfaces considered were representative of pure bending, the interactions between the bending moment and transverse shear, and bending moment and membrane force, each corresponding to a special case depending on the geometry of the beam. A time-dependent, kinematically admissible velocity profile was assumed to treat the dynamic formulations in interaction of each phenomenon. A study on the strain-rate sensitivity was also presented, and existence of a critical pressure triggering the apparition of travelling plastic hinges was hence highlighted. For blast loads of high magnitude, the expressions for normalised deflection were furnished in terms of the impulsive velocity. The analytical models were validated by performing a parametric study on the two-dimensional representative of the beam model in commercial finite element software ABAQUS 6.14. The numerical results show a good correlation with the analytical results in each case.<br />
Published version, 6 months embargo. Source at: <a href=https://doi.org/10.1177/2041419618807721>https://doi.org/10.1177/2041419618807721</a><br />
2018-10-31T00:00:00ZDynamic plastic response of beams subjected to localised pulse loadsThil, NicolasMehreganian, NavidMoatamedi, MojtabaLouca, Luke A.Soleiman Fallah, ArashLocalised blast loads give rise to high gradients of overpressure detrimental to structural elements as beams and plates. This article presents an analytical study on the dynamic plastic response of beams made of a ductile metallic material due to close-in pulse pressure loading. The close-in pressure load is characterised by a spatially varying function constant over a central region and exponentially decaying beyond it. The temporal pulse shape is assumed to take different forms. The exact static plastic collapse load was obtained for the characteristic load using the framework of plastic limit analysis, whereby the analysis was then extended to the dynamic case by considering the appropriate yield surface and inclusion of inertia forces. The yield surfaces considered were representative of pure bending, the interactions between the bending moment and transverse shear, and bending moment and membrane force, each corresponding to a special case depending on the geometry of the beam. A time-dependent, kinematically admissible velocity profile was assumed to treat the dynamic formulations in interaction of each phenomenon. A study on the strain-rate sensitivity was also presented, and existence of a critical pressure triggering the apparition of travelling plastic hinges was hence highlighted. For blast loads of high magnitude, the expressions for normalised deflection were furnished in terms of the impulsive velocity. The analytical models were validated by performing a parametric study on the two-dimensional representative of the beam model in commercial finite element software ABAQUS 6.14. The numerical results show a good correlation with the analytical results in each case.Multi-Science PublishingJournal articlePeer reviewedThil, N., Mehreganian, N., Moatamedi, M., Louca, L.A, Soleiman Fallah, A. Dynamic plastic response of beams subjected to localised pulse loads. I <i>International Journal of Protective Structures. 2018</i>,1-31.https://doi.org/10.1177/2041419618807721International Journal of Protective Structures