F.A. Veer

Cable-stayed façade structure with welded borosilicate glass tubes

Structurally used tubular glass provides stunning possibilities for architectural applications, which have hardly been explored yet. Over the last decade, only a handful of experimental structures have been presented, such as a 3D lattice structure by the University of Stuttgart [1], a tensigrity structure [2] and columns in a pavilion by the TU Delft [3]. Just one project of significant size has been realized in practice: the hanging glass atrium facade of the Tower Place office building in London, UK, is horizontally supported by a field of glass tubes [4]. All these examples make use of geometrically relatively simple shapes, i.e. tubes. However, welding and hot shaping techniques for glass make it possible to produce much more complex shapes. The possibilities this offers on small scale design of mechanical joints have been explored in a case-study design for facade struts by Bos [5]. However, a glance in an average chemistry laboratory will give you a better impression of what could be possible. Little is known about glass welding for the building industry. Especially the bond strength is an important unknown as is the reliability. Other constraints such as which types of glass can be used and what shapes can be forged are also unknown. The existing projects have already shown the use of glass tubes introduces specific engineering problems compared to ordinary flat glass. They are normally only available in limited size, up to 1.5 m. Force transfer into a glass tube is also complicated as the geometry prohibits drilling holes and complicates adhesive joints. The potential of welding for structural applications of glass tubes has been explored by graduate student C. Giezen, by producing a case-study design alternative for the (existing) facade structure of a curtain facade of the Faculty of Architecture building. This paper is largely based on the results of that study. Theory on welding is reviewed and the practical possibilities of shaping by existing commercial firms explored. Experimental research, carried out on different welded specimens to investigate welded joint strength, is presented. Finally, a facade structure design based on 3D cross-shaped welded glass components, is presented. This study shows welding provides ample design possibilities without significantly compromising the component strength.