title: Experimental study on the torsional mechanics of laminated structural glass beams
Creators: name: Uheida, Kal
Publisher: name: Edinburgh Napier University
Year: 2022

description: This thesis presents an experimental study on the torsional-mechanical behaviours of laminated structural glass beams. Glass structures are in increasing demand due to many favourable characteristics such as high compressive strength, flexibility, aesthetics, sustainability, and their positive effects on human mood and performance. However, monolithic glass is brittle in nature and fails instantaneously so laminated glass building elements are preferred, which have complex composite behaviours. An additional challenge is the lack of a finalised glass design code. This PhD study takes aim specifically at laminated glass beams and their torsional mechanics, which are crucial for supporting floor and roof plates, glass walls and other applications that enable fully transparent structures to be realised.

A concise concept for quantifying the torsional stiffness of laminated glass beam elements is introduced – the Equivalent-Sectional Shear Modulus (ESSM), which is directly measured from the torque and sectional-rotation correlation in non-destructive torsion experiments. This method is advantageous as it allows for the measurement of overall rotation to torque response of laminated glass beams compositely rather than their individual components, resultantly decreasing the uncertainties of commonly adopted analytical approximations. A tailor-made, non-contact displacement measurement system based on the principles of binocular stereo-vision was developed, tested, verified, and employed to the torsion test procedure to increase the accuracy of photogrammetric measurements to be acquired. This incorporates the use of dense displacement sample targets on the glass beam which are measured and extracted using basic machine vision techniques, providing flexible, accurate, and non-intrusive measurements.

Experimental torsion studies were performed on multiple samples of monolithic, two-layer, and three-layer polyvinyl butyral (PVB) and SentryGlas Plus (SGP) beams. The experimental setup, equipment, and procedures were continually improved and refined in a step-wise process throughout this work. The monolithic beams experimental ESSM results were validated against theoretical calculations from their elastic moduli relationship. Furthermore, the experimental ESSM results for two-layer and three-layer laminated beams were also compared with existing analytical solutions based on sandwich theory. Further experimental studies were also performed to evaluate the effects of ‘eccentric-torque’, where the effect of an eccentricated torsional load path on the overall torsional rigidity of the beam is studied, and on the effect of lengthened load-durations for SGP laminates. A variety of interesting and remarkable results were obtained regarding the composite torsional-mechanical behaviours of laminated structural glass beams and the optimisation of a first-of-its-kind glass beam torsion test approach. The results of this PhD thesis may help to support the further development of structural glass design codes and practices.