A structural concept for a demountable glass column

Abstract

The high compressive strength of the material glass in combination with its transparency, make it an attractive material to use for a column. Though different types and configurations of glass columns have been subject of academic research, a demountable glass column made from laminated components remains unexplored. This structural concept allows for modular and temporary structures with incorporated structural safety. Assembly and demounting is quick and the smaller, laminated components give the column sufficient redundancy.

Glass however, is notorious for its low tensile strength and brittle failure. Also, a column made from interlocking components introduces stability problems. A comprehensive understanding of this new type of glass column is necessary before application in the built environment is possible. So far, no numerical analysis has been conducted on columns made up of interlocking laminated elements, while this analysis can help understand the stability, force distribution and stress concentrations of such a system.

The main objective of this research is to obtain a feasible all-glass column design. This is achieved by using a Finite Element Analysis(FEA) to investigate: stability, force distribution and stress concentrations. Furthermore, a variety of design aspects and trade-offs are discussed in detail. These structural and design considerations are used to iterate the column design and to propose a combination of parameters that leads to a feasible design.

The FEA investigates the following structural parameters: component dimension, roof ballast load, façade stiffness and interlayer thickness. Different combinations of investigated parameters lead to a feasible, functioning column designs. The column is able to horizontally displace up to 9,1mm before becoming unstable. The heavier ballast load of 1,2kN/m2 is desired over the minimal value of 0,6kN/m2. The column is unable to take up a significant amount of the total horizontal case study load for all investigated component widths. It can take up up to 39% of the vertically applied load when a minimal amount of soft interlayers is used. The tensile stress concentrations stay within the allowable limits.

The different design aspects investigated include: material constraints, fabrication limitations, safety and redundancy and assembly. Each laminated component is made of up 3x15mm thick annealed float glass plates, and is fit with a sacrificial layer on either side for protection. The glass plates are water jet cut into the desired shape and then laminated together to form the component. The shape of the interlock is gradual end rounded in order to prevent (tensile) peak stresses. The risk of damage has been minimised. Moreover, the glass column has sufficient redundancy because the laminated components retain sufficient bearing capacity in case of damage. Also, the structural glass façade serves as secondary loading path in the case of severe damage.

This research serves as a starting point for future research and possible real-life application of a novel type of interlocking glass column. This type of column can be applied in demountable structures. Combinations of parameters have been proposed that result in a feasible, functioning column. Recommendations have been set up to improve future iterations of columns with a similar design.