A high fiber reinforced concrete prototype for reciprocal structures of demountable building

Abstract

Spatial Reciprocal Frames (S.R.F) are three dimensional structures created with beams that hold each other up through simple support bindings. The construction principle is antique in origin and citations to its use have been found in the manuscripts of medieval treatise writers, such as Villard de Honnecourt, and in the documents of renaissance architects including those of Sebastiano Serlio and Leonardo da Vinci's Atlantic Code. This building concept allows the dismantling of the framework and its subsequent reassembly into different forms. Moreover, these geometrical and functional flexibilities consent the S.R.F. to meet ecological building standards of environmental regulations. The irregular arrangement of their modular support points and their ability to be dismantled make them suitable even in unusual situations; for example, to provide the covering an exposition pavilion as well as archaeological field with a temporary roof. Their use today appears to present particular interest for the planning of temporary buildings that can be dismantled and their materials recuperated. What is more, they hold specific implications for ecosustainable building systems; in particular, for their potential reuse in the creation of both large and small structures that can be repeatedly readapted for changing uses. In such cases, the resulting constructions may be of distinct forms and dimensions, there need not be waste of the previously used materials, or the consumption of additional ones. Indeed, a key characteristic of these structures is that they are able to reform junctions with different geometries that can then be dismantled and reformed again using differently positioned support points that are not necessarily coplanar. The same elements (i.e. the beams) can then be used to create junctions formed of three, four, five or even more connecting beams with a static system equilibrium that changes depending upon the variation of the stipulated heights of the base support points. This geometrical and structural flexibility also renders the S.R.F. subject to particular interest with regards to the LEED (Leadership in Energy and Environmental Design) certification, in which protocols are assigned a higher value of ecosustainability when the structure can be reused at the end of its functional life in such a way that it can be reassembled into alternative forms and compositions for purposes that differ to its initial use. The structure lends itself as being particularly well suited for the covering of large spaces and can be built using highly diverse materials, including, steel, lamellar wood and even reinforced concrete that can be readily employed. Such flexibility makes it appealing when special solutions are required, as is the case when creating of temporary and reversible protections for archaeological excavations sites, where the ability to dismantle the system is of particular importance, as is the ability to stipulate the position of the base support points with total geometrical flexibility, both in the horizontal and in the vertical plane, in a way that the structure does not interfere with the historical remains. A renowned company from Bergamo, a world leader in the production of cement, also contributed to the project. They gave us the possibility to make and test some prototypes of demountable elements for the creation of temporary roofs and buildings. As the sponsor Italcementi produces concrete, we built the model using a high resistance concrete of reinforced fibre (HRC). The prototype was of an appropriate dimension and weight such that it could easily be positioned during the trials. The cases reported here are essentially the studies and laboratory prototypes that have been perfected through the course of the research conducted within the Faculty of Engineering at the University of Bergamo between 2006 and today; the results of which have permitted the elaboration of a project that has been submitted to the competition for the construction of the Italian Pavilion at the Shanghai 2010 World Expo. This paper summarises the geometrical research carried out at the University of Bergamo on the S.R.F. and describes the setting-up of a physical Finished Elements Model (FEM) created to test the structural potential of the system. The results of the research have permitted the elaboration of a project that has been submitted to the competition for the construction of the Italian Pavilion at the Shanghai 2010 World Expo and demonstrates the practical and viable use of S.R.F. in a contemporary architectural context. Finally, this paper will now summarise some concepts in order to demonstrate the preliminary results of our studies and their possible outlook and future development on the way of a necessary continuity between reciprocal structures and tensegral structures.