998 research outputs found
Flexible mould for production of double-curved concrete elements
No full textThis thesis focuses on the consequences of deforming a flexible mould surface. Based on the findings a new mould design was developed in order research the deformation of the mould. Also a method was developed to obtain an accurate geometry of the mould surface.Structural DesignStructural EngineeringCivil Engineering and Geoscience
Innovative Ways of Dealing with Existing Problems: How to reliably Assess the Cause of Damage of Masonry Structures in an Area with Man-induced Earthquakes?
No full textGroningen, a province in the northern part of the Netherlands, suffers from earthquakes because of gas drilling. The residential building stock in Groningen was not designed for these loads. Over the years a lot of smaller and larger damage has developed, possibly - but not necessarily - caused by the effects of gas drilling. Delft University of Technology was asked by the Dutch government to come up with a method to reliably assess the cause of damage of masonry structures in Groningen. This paper discusses the developed approach for reliably assessing the causes of failure of masonry structures in earthquake-prone areas and the way innovative monitoring techniques were applied.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Mechanic
Efficient material use through smart flexible formwork method
No full textConcrete is an excellent material for application in free-form architecture as a result of its initial fluid state. Double-curved building shapes have been realized in various fibre-reinforced mixtures, using advanced CNC-milled formwork systems. However, a substantial reduction of material use is still possible on two ends: by using a flexible formwork very thin and structurally efficient elements can be manufactured, reinforced with fibres or textiles. Moreover, the reusability of the flexible formwork considerably limits the waste material that was always remaining after the use of milled formwork systems. This paper discusses experiments with both formwork and mixtures in a PhD-study of the first author, demonstrating the ecological potential of this innovative production method.Structural EngineeringCivil Engineering and Geoscience
Frei geformte Betonbauteile: Finden einer Fertigungsmethode
No full textDue to the complexity of the freeform shapes it is often not possible to distinguish any repetitive elements in freeform buildings at all. Most freeform building designs consist of many single or double curved surfaces which require complex shapes for the mould and element edges. Since the costs of the moulds (formwork) for precast concrete make up a significant percentage of the final price per element or per square meter, the feasibility of freeform buildings in precast concrete is still far from optimal. The PhD research carried out at Delft University of Technology, Faculty ofCivil Engineering, aims to improve the applicability of precast concrete through the development of a flexible mould. At the end of the research the design specifications of vital parts of the flexible mould should be described, and supported by theoretical and experimental study as a proof of concept.Structural EngineeringCivil Engineering and Geoscience
ПРОИЗВОДСТВО БЕТОННЫХ ЭЛЕМЕНТОВ С ДВУМЯ КРИВОЛИНЕЙНЫМИ КОНТУРАМИ - ПРИМЕНЕНИЕ ПЕРЕДОВЫХ ПРОИЗВОДСТВЕННЫХ МЕТОДОВ В СОЗДАНИИ СВОБОДНЫХ АРХИТЕКТУРНЫХ ФОРМ Manufacturing of Double-Curved Concrete Elements: Enabling free-form architecture through advanced manufacturing methods
No full textВ современных архитектурных решениях широко используется криволинейность свободных форм. Именно поэтому изогнутые элементы из сборного бетона могут быть потенциальным рын- ком для производителей. В прошлом не существовало просто- го способа для производства таких компонентов. Исследования, проводимые в докторантуре Дельфтского Технического универ- ситета, направлены на разработку такого метода. Как теорети- ческие исследования, так и испытания, показывают, что новый метод, при котором сначала происходит заливка бетона, а потом его изгиб в гибкой опалубке, является практически возможным и обладает конкретными преимуществами, как то: при его при- менении относительно легко регулировать толщину элемента, нет необходимости использовать контрформу, гибкая опалуб- ка позволяет свободно и многократно изменять форму опалуб- ки и поэтому использовать ее повторно раз за разом. Оптими- зация бетонных смесей позволяет сократить цикл. Планирует- ся провести больше испытаний в ближайшем будущем в целях дальнейшей разработки самого метода и оборудования. При- глашаем партнеров из промышленных и академических кругов к участию в проекте для совместной работы по разным темам, необходимой для успешного полномасштабного применения этой технологии на практике. Current architectural designs make extensive use of curvature in free-form shapes. Curved elements in precast concrete therefor form a potential market for concrete manufacturers. A simple method to produce this type of elements was not available in the past. A PhD research at TU Delft aims to develop such a method. The theoretical research and the tests demonstrate that a new technique of first casting and later deforming concrete in a flexible mould is feasible and has several advantages: it is a relatively easy way to control element thickness, there is no need for a contra mould, the flexible mould gives freedom to adjust the shape of the mould multiple times and thus reuse it time after time. By optimizing the concrete mixture, a short cycle time can be reached. In the near future more tests are planned to further develop and improve the method and equipment. Industrial or academic partners are invited to participate in the project, to work together on the different topics necessary to make this technology ready for full scale application in practice.Design and ConstructionCivil Engineering and Geoscience
Double-curved precast concrete elements: Research into technical viability of the flexible mould method
No full textThe production of precast, concrete elements with complex, double-curved geometry is expensive due to the high costcosts of the necessary moulds and the limited possibilities for mould reuse. Currently, CNC-milled foam moulds are the solution applied mostly in projects, offering good aesthetic performance, but also resulting in waste of material, relatively low production speed and fairly high costs per element. The flexible mould method aims to offer an economic alternative for this state of art technology by allowing repeated reuse of the same mould, and if necessary, reuse in adapted shape. A patent and literature review and comparison of state-of-art formwork methods reveals that, although the idea of a flexible formwork already dates from the mid-20th century, in building industry it has not yet found widespread application, and is still experimental to a large extent. In other industries, such as aerospace and automotive, flexible moulds are occasionally used for rapid prototyping purposes, mostly for the forming of thin metal sheets. The understanding of the flexible mould principle in terms of mechanics is still in development. In combination with concrete, the flexible mould has been industrially applied only on occasion. Deliberately imposed deformation of concrete after casting allows the use of only one single-sided flexible mould, but - being a method quite alien to normal precast concrete production - has hardly been investigated. Therefore, models are needed both for the flexible layer as well as it's use in combination with concrete. By analysing a number of architectural cases in terms of geometrical aspects, more information is gathered about building size, element thickness, curvature radius and number and type of elements. This information is used to define the type of shapes for which the flexible mould method would be suitable. Through the last 80 years, the shape of curved architecture has changed; whereas the early famous shell designers such as Isler and Torroja aimed for structurally optimized and material-efficient shapes, nowadays these shapes have mostly made place for free-form curves, in which parametric design or sculptural influences are leading. For larger projects, several hundreds to even thousands of uniquely curved elements are manufactured, varying in curvature radius in a range between 0.75 m and 45 m. Furthermore the contours and edge position can vary from element to element. Prediction of each element's edge position is non-trivial for the flexible mould method, especially not for elements with strong curvature. The deformation process can be described mathematically by analysing thecurvature parameters. An important and meaningful parameter is the Gaussian curvature. Depending on the change in Gaussian curvature, the imposed deformation of the mould surface and the concrete results in certain amounts of bending action (B) and in-plane surface stretching (S). Bending tensile strains in the still plastic concrete can be in the range of 25 to 50\u89 for an element with 50 mm thickness, which is far more than the values normally encountered in concrete after casting. The application of in-plane shear deformation appears to be helpful to deform the mould from flat to double-curved. The exact positioning of the element edges can be determined from this in-plane shear deformation. The shape of the mould, in the present research, is controlled by a grid of actuators - extendible support points that follow the intended architectural shape. As mould surface, a thin rubber layer can be used, that, however, has to be supported by a material that is capable of carrying the weight of the concrete without visible deflection between the actuators. Various solutions are investigated for this support material, of which the strip mould offers the most accurate results and predictability. As said, the concrete in this method is deliberately deformed after casting in an open, single-sided mould. This requires control over both the fluidity and strain capacity of the fresh concrete: if the concrete is too fluid, it will flow out of the mould after deformation due to the slope of the mould, if it is already too stiff, cracks may occur. Various experiments are conducted to investigate the viability of the principle as well as the parameters that influence the risk of either flow or cracking. It appears that the use of a self-compacting concrete with thixotropic properties reduces both the risks: as a result of quick stabilisation after casting, the yield strength build-up will prevent flow once the mould is deformed and put at a certain slope. Thanks to it's plastic strain capacity, this type of concrete will be able to undergo the imposed deformation without cracking. An important measure to prevent this cracking is the curing of the concrete directly after casting and a deformation that takes place before initial setting time. Thin steel rebar, glass-fibre textiles or mixed fibres are all applicable as reinforcement, the latter two giving the best results. For the measurement of yield strength development of the concrete mixture before and after casting, various methods are investigated. Literature research and experiments demonstrate that, once the rheological behaviour of a mixture has been determined with a viscometer accompanied with slump (flow) tests, the correct moment of deformation of the flexible mould can later be determined from repeated slump (flow) tests with sufficient reliability. However, as soon as the mixture constituents will be adapted, new viscometer measurements have to be carried out again. The flexible mould method has been successfully tested on single- and double-curved precast concrete elements with a radius down to 1.50 m and an element thickness up to 50 mm. Until this moment, the maximum element size tested was approximately 2 x 1 m2, but larger elements are expected to be feasible. An integrated design-to-production process is required: due to the complex geometry and the impact of this geometry on all aspects of the manufacturing, all parties involved should cooperate to make the use of this method possible. Computational skills are needed to determine design parameters and control the manufacturing process. Several new questions were identified during the research, but at this moment, implementation of the flexible mould method in an industrial environment in cooperation with a concrete product manufacturer is the best way to determine the priorities for further research. From the full research it is concluded that the flexible mould method is viable for the production of double-curved concrete elements.Structural EngineeringCivil Engineering and Geoscience
Feasibility of Concrete Shells using Flexible Mould Prefabricated Concrete Elements
No full textShell structures appear quite often in our daily life. From aircraft fuselages to storage silos and boat hulls, these structures are employed for their structural efficiency and the aesthetics they provide. They are characterised by a small thickness in comparison to their other dimensions and by curvature in their unstressed state. Despite their structural efficiency transferring loads in their plane, thin concrete shells are not employed quite often. The traditional construction method is a labour intensive process which includes the fabrication of a formwork system, usually made out of plywood, on which concrete is cast. The necessary reinforcement in the form of bars although it is quickly placed, it has the drawback of requiring frequent joints and overlapping. Its bending and assembling is also considered difficult for curved shapes like shells. As it can be seen, great costs emerge from this process and this was a trigger factor for the formation of the research question. A different approach for the construction of shells employs prefabricated elements which are connected on site and create the complete thickness of the concrete shell. Although high construction speed and high quality are achieved with this method, significant reduction of costs is still not feasible, as the formwork is very expensive and re-use of it, is only occasionally possible. However, an adjustable mould can produce elements of different dimensions, shape and curvature, decreasing substantially the formwork costs which comprise large part of the total shell construction costs. The flexible mould method and the principle of deformation after casting that were introduced by Prof. R.H. Schipper find application in this project. This project aims to answer whether it is possible to construct a concrete shell using the flexible mould prefabricated elements, without putting aat risk the stability of the structure. A comparison between the structural feasibility of a monolithic shell and the one of a segmented prefabricated shell is the method that will be utilised to answer the research question.Civil Engineering | Building Engineerin
Self-supporting sandwich element for freeform building envelopes
No full textDesign for a custom CNC wire-cut sandwich element from EPS and fibre glass reinforced epoxy. Algoritmic model for generation of custom elements.computation and performance designBuilding TechnologyArchitectur
Een nieuwe kijk op funderingsherstel
No full textFunderingsproblemen bij panden op houten palen hebben voornamelijk in het westen van Nederland een grote omvang. Geschat wordt dat ruim 250.000 panden op dit moment te maken hebben met deze problemen. Men verwacht dat dit aantal in de toekomst nog flink zal stijgen (CURNET/SBR Rotterdam, 2012). Gezien het feit dat het herstellen van een fundering nogal kostbaar is, zijn de verschillende conventionele hersteltechnieken onderzocht. Deze zijn vervolgens kort samengevat in dit rapport. Op basis van deze kennis en een aantal kostenramingen van de conventionele herstelmethoden is gezocht naar de grootste kostenpost bij het herstellen van een fundering. Niet geheel onverwachts blijken de grootste kosten te zitten in nieuw in te brengen palen en in het betonwerk. De verschillende paalsoorten die bij het herstel kunnen worden gebruikt zijn vervolgens uiteengezet. Hierbij blijken slechts een beperkt aantal paalsoorten in aanmerking te komen, namelijk palen die trillingsarm zijn en niet grond-verwijderend. Bij het heien aan de buitenzijde van het pand kan men gebruik maken van stalenbuis palen. Dit is de meest praktische paal aangezien er voldoende variabiliteit is in de diameter van deze buis. Er kan dus een verscheidenheid aan belastingen worden opgenomen. Voor inwendig heien moet de paal in te brengen zijn bij beperkte werkhoogte. Ook hier zijn maar enkele paalsystemen voor te gebruiken. De kosten voor de verschillende paalsystemen blijken al jaren constant en nieuwe methoden zijn nog niet beschikbaar (Everts, 2012). In dit onderzoek is daarom gekozen om besparingen te zoeken in het betonwerk. Bij de methode met voorspanbalken blijken de kosten voor het betonwerk hoger te zijn dan de palenkosten. Daarbij ondervinden de bewoners bij deze methode weinig hinder, aangezien er geen beganegrondvloer hoeft te worden verwijderd. Dit gaf de aanleiding om te onderzoeken of bij deze methode een besparing kan worden gevonden in een alternatief. Voor dit alternatief is onderzocht of het gebruik van (ultra) hoog sterkte beton en het plaatsen van voorspankabels buiten de betonbalk, een besparing kan opleveren bij het herstel. Er is naar aanleiding van bovenstaande onderzoek gedaan naar de betonmortelprijzen. Aangezien deze niet bekend waren voor C100/115 en C200/215 is er een extrapolatie gedaan van de bekende prijzen. Theoretisch blijkt het te kunnen om de balk zodanig slank de dimensioneren dat nog steeds aan de veiligheidseisen wordt voldaan. Als de kabels een bepaalde kromming en kracht hebben, kan dit namelijk worden gezien als opwaartse qSlast. Van dit principe is gebruik gemaakt bij de berekening. Er valt dus wel degelijk te besparen op de betonkosten. Verder onderzoek zal wel moeten worden gedaan naar het inleiden van de voorspankracht bij het anker en de inleiding over de lengte van de balk. De voorspankabels moeten op dusdanige manier met de balk zijn verbonden, dat deze zijn kracht kan overdragen op de betonbalk. Tevens is er onderzoek gedaan naar het effect van meer terreinonderzoek. Een duidelijke conclusie die hieruit volgt is dat een gedegen grondonderzoek, gezien de geringe kosten per sondering, bijna altijd voordelen heeft. Zowel in de berekening van de draagkracht, als bij het verkrijgen van een beter beeld van de ondergrond. Op basis van deze kennis weten de ingenieurs beter wat zich in de ondergrond bevindt en kan mogelijk een betere oplossingen voor het probleem worden gevonden, en waar mogelijk wellicht ook een kostenbesparing.Structural and Building EngineeringStructural EngineeringCivil Engineering and Geoscience
Verloren bekistingen met blijvende waarde: Hoe verloren geïsoleerde bekistingen functioneren in de Nederlandse bouwpraktijk
No full textVoordelen ICF - Monoliete constructie - Bouwfysische voordelen bij ICF als concept - Hoge verwerkbaarheid door lage dichtheid EPS Nadelen ICF - Wanddikte niet flexibel - Lage warmteweerstand EPS - Risico op condensatieStructural and Building EngineeringStructural EngineeringCivil Engineering and Geoscience
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