Harald Kloft

Digitally Fabricated Innovative Concrete Structures

This paper presents the general aim of the research at the Institute of Structural Design (ITE) at Braunschweig University of Technology to bring digital design and digital fabrication together to develop resource efficient construction elements, manufacturing processes and building systems. Basis of research at ITE is the so-called Digital Building Fabrication Laboratory (DBFL). The paper gives an overview of machine design, the technical parameters and its basic abilities of subtractive and additive processes e.g. milling, printing and scanning. Based on the combined use of these digital fabrication processes and in cooperation with highperformance materials such as ultra-high performance concrete (UHPC), different research projects are being performed at the ITE. To explain the possibilities of the DBFL, the paper will present the results of two different – additive and subtractive research projects to develop fabrication techniques for the building industry. The first project is dealing with the development of “digitally fabricated high precision Non-WasteWax-Formwork for innovative UHPC structures” and the second project is investigating “Additive manufacturing of free-form concrete elements using Shotcrete 3D Printing (SC3DP) technology”. Finally, the paper will highlight the possibilities of combining these technologies and transferring them

Development of a Shotcrete 3D-Printing (SC3DP) Technology for Additive Manufacturing of Reinforced Freeform Concrete Structures

In this paper, a novel Additive Manufacturing (AM) technique for robot-based fabrication of large-scale freeform reinforced concrete elements is presented. The AM technology, called Shotcrete 3D Printing (SC3DP), is based on an automated shotcreteing process and offers the ability to integrate structural reinforcement in both principal directions and enables printing of horizontal cantilevers onto vertical surfaces. Moreover, the SC3DP technique effectively addresses the problem of cold joints that is inherent to other 3D printing techniques. However, as controlling the process parameters of the SC3DP technique is significantly more complex than it is for conventional 3D concrete printing processes, several closed-loop online control routines were developed and integrated. The resulting gain of control for this adaptive fabrication process is demonstrated through a case study for the production of a complexes reinforced concrete component. Moreover, its conceptual implications are discussed and an outlook for future work is given.

Automated Additive Manufacturing of Concrete Structures without Formwork - Concept for Path Planning

At the Digital Building Fabrication Laboratory in Braunschweig, automated additive manufacturing of concrete structures without formwork is researched. The system consists of a six-axis robot and a three-axis milling machine, which are each connected to a three-axis portal. At the robot a shotcrete sprayer is installed to generate concrete structures. In this paper a first path planning concept for the robot is described. The given algorithm calculates from the CAD data of an object a path for the robot. A difficulty of path planning is that the shotcrete application depends on various parameters. Therefore, a simplified model for the shotcrete application is developed. For the purpose of error minimization while spraying, an online monitoring approach by using a laser scanner is presented.

Entwerfen von leichten Dachtragwerken aus Glas und Stahl

Die Leichtigkeit von Dachtragwerken wird nicht durch Minimierung der Masse erzielt. Auch die Verwendung der Werkstoffe Glas und Stahl ist per se noch kein Garant fur die filigrane Erscheinung einer Konstruktion. Der Entwurf von leichten Dachtragwerken aus Glas und Stahl gestaltet sich vielmehr als Optimierungsaufgabe von intelligenter Verteilung der Masse und gezielter Nutzung der Leistungsfahigkeit der beiden Werkstoffe. Wesentlicher Aspekt ist die Abstimmung des Tragwerksentwurfes auf die architektonische Entwurfsidee und die ortlichen Randbedingungen. Dies erfordert von Beginn an eine enge Zusammenarbeit von Architekt und Ingenieur. In dem Beitrag werden die Entwurfsprozesse von drei leichten Dachtragwerken aus Stahl und Glas vorgestellt und die Rolle des entwerfenden Ingenieurs diskutiert. Die Tragwerke wurden von Klaus Fath und Harald Kloft, als Inhaber des Ingenieurburos osd – office for structural design, Frankfurt/M., in Zusammenarbeit mit Viktor Wilhelm, Stuttgart, geplant. Designing lightweight roof structures of glass and steel. Lightness of roof structures does not mean to minimize the building mass. As well, the use of glass and steel will not guarantee a sophisticated appearance of a construction. Designing a lightweight, transparent structure is much more a task of optimization by intelligent arrangement of the building mass and by the defined use of the materials glass and steel. An essential aspect is the structural design in relation to the architectural idea and the urban context. All together, this needs a close cooperation of architect and engineer from the very beginning of a design process. In the following three lightweight roof structures are presented and the role of the engineers will be discussed. All projects are designed by Klaus Fath and Harald Kloft, the principals of the Frankfurt based engineering practice osd – office for structural design in close cooperation with Viktor Wilhelm from Stuttgart.