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The construction of free form building stagnated, due to the high construction cost of it. Double curved surfaces are only applied at projects with a high profile and projects above average budget during years. The problem with double curved surfaces is mainly the formwork. The present days used techniques to construct these formworks are statically. For example: wooden, steel or milled EPS formwork could only be used for one shaped elements. The lack of repetition and so the reusability of the formwork, which means that for a free form surface for every element a unique formwork is needed, makes the construction very expensive. A feasible way for mass production of unique shaped double curved elements could be achieved by a flexible formwork: a formwork that can be adjusted in every desired shape. It consists of a flexible layer that can be deformed into the desired curved surface by adjusting for example pistons, actuators or pins. Recently K. Huyghe and A. Schoofs have executed a series of experiments with a flexible formwork, build earlier by D. Rietbergen and Dr. Ir. K. Vollers. The purpose of this master thesis was to solve more aspects of the flexible formwork, and to make it a feasibly system. The main focus was the behavior of the flexible layer, at some places the flexible layer did not though the actuators. Predicting the behavior of the deformed flexible layer makes an accurate production possible. To be able to determine the behavior of the flexible layer some models are proposed. With these models the reaction forces at the supports could be determined, compression forces means that the flexible layer though the supports. The first model that is proposed, is for a single curved element. For the double curved mould surface two models are proposed, a plate model and a strip model. With tests at the Stevin Laboratory these models are verified, and some other aspects are tested, for example the flexible border of the formwork. Tests indicate that a plate is not suitable for the flexible layer, it buckles due to the plate stresses. The strip mould consists of two layers of strips, perpendicular to each other. The top layer of the strips is the mould surface. Tests showed that it is possible to produce double curved elements with the strip mould. Conclusions and recommendations. The models that are proposed in this thesis describe the behavior of the flexible layer well. A plate does not fulfil the function of a flexible layer. Tests have shown that it is possible to produce double curved elements with the strip mould as flexible layer. To cover the strips an additional layer is needed. In these tests polyether is used, as well for the borders. The protection of the polyether with sealant made the concrete element very rough. Another material has to be found as elastic layer, or to protect the polyether.

Interiors Graduationproject 'Center for Performing Arts' in Amsterdam NDSM wharf.

The manufacturing of double-curved precast concrete elements is still expensive, due to the high costs and limited possibilities for repetitive use of the moulds or formwork. The goal of the research described in this paper is to develop a production method that overcomes these difficulties by enabling the mould to be reused many times and by making the shape of the mould adjustable in a flexible way. First the paper gives an introduction of free-form architecture and the issues related to realizing complex geometry in concrete. Sequentially, the paper reports on the structural mechanics models that have been developed to accurately describe the behaviour of a flexible mould material. Finally laboratory experiments are reported, that are based on the concept of deforming an initially flat concrete element into a curved shape after a short initial hardening period. After this deformation process further hardening will take place in the final curved shape. The advantages of starting with an initial flat layer are that no contra-mould is needed, the element thickness can be controlled accurately and the casting process is relatively quick and simple.

Free form architecture with complex geometry brings along new challenges for manufacturers of building components. This paper describes the application of structural mechanics to predict the behaviour of an elastic mould surface, used as formwork for the manufacturing of double curved panels in precast concrete. Results are presented of laboratory experiments with a formwork to validate the model. The authors demonstrate that the model together with the mould prototype enable a flexible yet straightforward production method for curved concrete products that is applicable in many free form architecture projects nowadays.

Free form architecture with complex geometry brings along new challenges for manufacturers of building components. This paper describes the application of structural mechanics to predict the behaviour of an elastic mould surface, used as formwork for the manufacturing of double curved panels in precast concrete. Results are presented of laboratory experiments with a formwork to validate the model. The authors demonstrate that the model together with the mould prototype enable a flexible yet straightforward production method for curved concrete products that is applicable in many free form architecture projects nowadays.

This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired final shape; the deformation typically takes place in the first hour after casting. In this research thin double-curved precast shell or cladding elements are considered. The paper introduces the method used to support the flexible formwork and focuses on the concrete technology necessary to control the process of deformation after casting. Relevant parameters are discussed that influence the concrete’s behaviour shortly after casting. Rheological characteristics of the fresh concrete appear to be particularly important for the design of a suitable mixture. Since from traditional concrete research little experimental data on deformation after casting appeared to be available, experiments were carried out to test a number of prepositions. Results of these experiments are shown as well.

This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired final shape; the deformation typically takes place in the first hour after casting. In this research thin double-curved precast shell or cladding elements are considered. The paper introduces the method used to support the flexible formwork and focuses on the concrete technology necessary to control the process of deformation after casting. Relevant parameters are discussed that influence the concrete’s behaviour shortly after casting. Rheological characteristics of the fresh concrete appear to be particularly important for the design of a suitable mixture. Since from traditional concrete research little experimental data on deformation after casting appeared to be available, experiments were carried out to test a number of prepositions. Results of these experiments are shown as well.