@inproceedings{RauschLeiseEdereretal.2016, author = {Rausch, Lea and Leise, Philipp and Ederer, Thorsten and Altherr, Lena and Pelz, Peter F.}, title = {A comparison of MILP and MINLP solver performance on the example of a drinking water supply system design problem}, series = {ECCOMAS Congress 2016 VII European Congress on Computational Methods in Applied Sciences and Engineering}, booktitle = {ECCOMAS Congress 2016 VII European Congress on Computational Methods in Applied Sciences and Engineering}, editor = {Papadrakakis, M. and Ppadopoulos, V. and Stefanou, G. and Plevris, V.}, isbn = {978-618-82844-0-1}, pages = {8509 -- 8527}, year = {2016}, abstract = {Finding a good system topology with more than a handful of components is a highly non-trivial task. The system needs to be able to fulfil all expected load cases, but at the same time the components should interact in an energy-efficient way. An example for a system design problem is the layout of the drinking water supply of a residential building. It may be reasonable to choose a design of spatially distributed pumps which are connected by pipes in at least two dimensions. This leads to a large variety of possible system topologies. To solve such problems in a reasonable time frame, the nonlinear technical characteristics must be modelled as simple as possible, while still achieving a sufficiently good representation of reality. The aim of this paper is to compare the speed and reliability of a selection of leading mathematical programming solvers on a set of varying model formulations. This gives us empirical evidence on what combinations of model formulations and solver packages are the means of choice with the current state of the art.}, language = {en} } @inproceedings{RajanHoltschoppenDalgueretal.2016, author = {Rajan, Sreelakshmy and Holtschoppen, B. and Dalguer, L. A. and Klinkel, S. and Butenweg, Christoph}, title = {Seismic fragility analysis of a non-conventional reinforced concrete structure considering different uncertainties}, series = {Proceedings of ISMA2016, International Conference on Noise and Vibration Engineering/USD2016, International Conference on Uncertainty in Structural Dynamics, / ISMA 2016, USD 2016}, booktitle = {Proceedings of ISMA2016, International Conference on Noise and Vibration Engineering/USD2016, International Conference on Uncertainty in Structural Dynamics, / ISMA 2016, USD 2016}, editor = {Sas, P.}, publisher = {KU Leuven}, address = {Leuven}, pages = {4213 -- 4225}, year = {2016}, language = {en} } @inproceedings{KubalskiMarinkovićButenweg2016, author = {Kubalski, T. and Marinković, Marko and Butenweg, Christoph}, title = {Numerical investigation of masonry infilled R.C. frames}, series = {Brick and Block Masonry. Proceedings of the 16th International Brick and Block Masonry Conference, Padova, Italy, 26-30 June 2016}, booktitle = {Brick and Block Masonry. Proceedings of the 16th International Brick and Block Masonry Conference, Padova, Italy, 26-30 June 2016}, editor = {Modena, Claudio}, publisher = {CRC Press}, address = {Leiden}, isbn = {9781315374963}, pages = {1219 -- 1226}, year = {2016}, language = {en} } @article{ButenwegMarinkovicKubalskietal.2016, author = {Butenweg, Christoph and Marinkovic, Marko and Kubalski, Thomas and Klinkel, Sven}, title = {Masonry infilled reinforced concrete frames under horizontal loading}, series = {Mauerwerk}, volume = {20}, journal = {Mauerwerk}, number = {4}, publisher = {Ernst \& Sohn}, address = {Berlin}, issn = {1437-1022}, doi = {10.1002/dama.201600703}, pages = {305 -- 312}, year = {2016}, abstract = {The behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non-linear after a certain limit, which makes their analysis quite difficult. The non-linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall-frame interface. In order to investigate this non-linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non-linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non-linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto-plastically. Each brick is modelled individually and connected taking into account the non-linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures.}, language = {en} } @article{RosinButenwegKlinkel2016, author = {Rosin, Julia and Butenweg, Christoph and Klinkel, Sven}, title = {Stabilit{\"a}tsnachweis f{\"u}r seismisch beanspruchte Tankbauwerke nach dem LBA/MNA-Konzept}, series = {Bauingenieur}, volume = {91}, journal = {Bauingenieur}, number = {12}, publisher = {VDI Fachmedien}, address = {D{\"u}sseldorf}, issn = {0005-6650}, doi = {10.37544/0005-6650-2016-12-74}, pages = {518 -- 526}, year = {2016}, abstract = {Eine seismische Anregung verursacht in einem Fl{\"u}ssigkeitstank einen kombinierten Spannungszustand, was zu einem Stabilit{\"a}tsversagen der h{\"a}ufig sehr d{\"u}nnwandigen Konstruktionen f{\"u}hren kann. F{\"u}r die Durchf{\"u}hrung von Stabilit{\"a}tsnachweisen stehen verschiedene Verfahren zur Verf{\"u}gung. {\"U}blicherweise werden aus Gr{\"u}nden der Einfachheit spannungsbasierte Verfahren angewendet. Diese sind f{\"u}r Einheitslastf{\"a}lle experimentell abgesichert, wobei eine {\"U}bertragung auf kombinierte Spannungszust{\"a}nde wie im Erdbebenfall nur begrenzt m{\"o}glich ist. Alternativ kann ein globales, numerisches Konzept, das LBA/MNA-Verfahren, angewendet werden. Das Verfahren kombiniert eine materiell nichtlineare Berechnung (MNA) mit einer linearen Beulanalyse (LBA) und erfasst die Interaktion verschiedener gleichzeitig auftretender Beanspruchungen implizit im Nachweis. Dieser Beitrag demonstriert die Anwendung der Verfahren am Beispiel verschiedener Tankgeometrien mit H{\"o}he/Radius-Verh{\"a}ltnissen zwischen 1 ≤ H/R ≤ 2 und Radius/Tankwand-Verh{\"a}ltnissen zwischen 500 ≤ R/t ≤ 1000 und diskutiert zus{\"a}tzlich die Defizite der spannungsbasierten Nachweisverfahren.}, language = {de} } @incollection{ButenwegKubalskiMarinkovicetal.2016, author = {Butenweg, Christoph and Kubalski, Thomas and Marinkovic, Marko and Pfetzing, Thomas and Ismail, Mohammed and Fehling, Ekkehard}, title = {Ausfachungen aus Ziegelmauerwerk}, series = {Mauerwerk-Kalender 2016: Baustoffe, Sanierung, Eurocode-Praxis}, booktitle = {Mauerwerk-Kalender 2016: Baustoffe, Sanierung, Eurocode-Praxis}, publisher = {Ernst \& Sohn}, address = {Berlin}, isbn = {978-3-433-03131-5}, year = {2016}, language = {de} } @article{HarishWriggersJungketal.2016, author = {Harish, Ajay B. and Wriggers, Peter and Jungk, Juliane and Hojdis, Nils and Recker, Carla}, title = {Mesoscale Constitutive Modeling of Non-Crystallizing Filled Elastomers}, series = {Computational Mechanics}, volume = {57}, journal = {Computational Mechanics}, publisher = {Springer}, address = {Berlin}, issn = {1432-0924}, doi = {10.1007/s00466-015-1251-1}, pages = {653 -- 677}, year = {2016}, abstract = {Elastomers are exceptional materials owing to their ability to undergo large deformations before failure. However, due to their very low stiffness, they are not always suitable for industrial applications. Addition of filler particles provides reinforcing effects and thus enhances the material properties that render them more versatile for applications like tyres etc. However, deformation behavior of filled polymers is accompanied by several nonlinear effects like Mullins and Payne effect. To this day, the physical and chemical changes resulting in such nonlinear effect remain an active area of research. In this work, we develop a heterogeneous (or multiphase) constitutive model at the mesoscale explicitly considering filler particle aggregates, elastomeric matrix and their mechanical interaction through an approximate interface layer. The developed constitutive model is used to demonstrate cluster breakage, also, as one of the possible sources for Mullins effect observed in non-crystallizing filled elastomers.}, language = {en} } @article{SchwabHojdisLacayoetal.2016, author = {Schwab, Lukas and Hojdis, Nils and Lacayo, Jorge and Wilhelm, Manfred}, title = {Fourier-Transform Rheology of Unvulcanized, Carbon Black Filled Styrene Butadiene Rubber}, series = {Macromolecular Materials and Engineering}, volume = {301}, journal = {Macromolecular Materials and Engineering}, number = {4}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-2054}, doi = {10.1002/mame.201500356}, pages = {457 -- 468}, year = {2016}, abstract = {Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ0 < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ0 = 0.32). The addition of up to 70 phr CB leads to an increase of I3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I3/1 is pronounced for CB levels above the percolation threshold.}, language = {en} } @article{SvaneborgKarimiVarzanehHojdisetal.2016, author = {Svaneborg, Carsten and Karimi-Varzaneh, Hossein Ali and Hojdis, Nils and Fleck, Franz and Everaers, Ralf}, title = {Multiscale approach to equilibrating model polymer melts}, series = {Physical Review E}, volume = {94}, journal = {Physical Review E}, number = {032502}, publisher = {AIP Publishing}, address = {Melville, NY}, issn = {2470-0053}, doi = {10.1103/PhysRevE.94.032502}, year = {2016}, abstract = {We present an effective and simple multiscale method for equilibrating Kremer Grest model polymer melts of varying stiffness. In our approach, we progressively equilibrate the melt structure above the tube scale, inside the tube and finally at the monomeric scale. We make use of models designed to be computationally effective at each scale. Density fluctuations in the melt structure above the tube scale are minimized through a Monte Carlo simulated annealing of a lattice polymer model. Subsequently the melt structure below the tube scale is equilibrated via the Rouse dynamics of a force-capped Kremer-Grest model that allows chains to partially interpenetrate. Finally the Kremer-Grest force field is introduced to freeze the topological state and enforce correct monomer packing. We generate 15 melts of 500 chains of 10.000 beads for varying chain stiffness as well as a number of melts with 1.000 chains of 15.000 monomers. To validate the equilibration process we study the time evolution of bulk, collective, and single-chain observables at the monomeric, mesoscopic, and macroscopic length scales. Extension of the present method to longer, branched, or polydisperse chains, and/or larger system sizes is straightforward.}, language = {en} } @article{WeberArentMuenchetal.2016, author = {Weber, Tobias and Arent, Jan-Christoph and M{\"u}nch, Lukas and Duhovic, Miro and Balvers, Johannes M.}, title = {A fast method for the generation of boundary conditions for thermal autoclave simulation}, series = {Composites Part A}, volume = {88}, journal = {Composites Part A}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1359-835X}, doi = {10.1016/j.compositesa.2016.05.036}, pages = {216 -- 225}, year = {2016}, abstract = {Manufacturing process simulation enables the evaluation and improvement of autoclave mold concepts early in the design phase. To achieve a high part quality at low cycle times, the thermal behavior of the autoclave mold can be investigated by means of simulations. Most challenging for such a simulation is the generation of necessary boundary conditions. Heat-up and temperature distribution in an autoclave mold are governed by flow phenomena, tooling material and shape, position within the autoclave, and the chosen autoclave cycle. This paper identifies and summarizes the most important factors influencing mold heat-up and how they can be introduced into a thermal simulation. Thermal measurements are used to quantify the impact of the various parameters. Finally, the gained knowledge is applied to develop a semi-empirical approach for boundary condition estimation that enables a simple and fast thermal simulation of the autoclave curing process with reasonably high accuracy for tooling optimization.}, language = {en} }