Abstract
The effectiveness of post-tensioning in enhancing the fracture resistance of glass beams depends on the level of compressive pre-stress introduced at the glass edge surface that will in service be exposed to tensile stresses induced by bending. Maximum pre-load that can be applied in a post-tensioned glass beam system, yielding maximum compressive pre-stress, is limited by various failure mechanisms which might occur during post-tensioning. In this paper, failure mechanisms are identified for a post-tensioned glass beam system with a flat stainless steel tendon adhesively bonded at the bottom glass edge, including the rupture of the tendon, glass failure in tension and adhesive/glass failure in the load introduction zone. Special attention is given to the load introduction failure given that the transparent nature of glass limits the use of vertical confinement usually applied in concrete. An analytical model for determination of the allowable pre-load in post-tensioned glass beams is proposed, based on the model applied for externally post-tensioned concrete beams. The model is verified with the results of a numerical model, showing good correlation, and applied in a parametric study to determine the influence of various beam parameters on the effectiveness of post-tensioning glass beams.
Highlights
Post-tensioned glass beams are hybrid structural components in which a ductile tendon is applied on a standard glass section to enhance its in-plane bending behaviour
Numerical verification of the proposed analytical model has shown that the model can be applied with sufficient accuracy for the prediction of short-term mechanical behaviour of post-tensioned glass beams, in terms of stress distribution in the tendon and the adhesive, and determination of the maximum compressive pre-stress that can be achieved in the glass without causing premature failure at pre-load introduction
The effectiveness of post-tensioning in enhancing the inplane bending behaviour of a laminated glass beam with an adhesively bonded flat stainless steel tendon has been discussed taking into account the failure mechanisms that may cause premature failure of the system during post-tensioning or upon release of the applied pre-load from the posttensioning set-up. Certain failure mechanisms, such as the rupture of the tendon and glass failure at the top glass edge, can be avoided with adequate detailing and simple structural verifications
Summary
Post-tensioned glass beams are hybrid structural components in which a ductile tendon is applied on a standard glass section to enhance its in-plane bending behaviour. Present study focuses on the effectiveness of post-tensioning in enhancing the fracture resistance of glass beams which depends on the level of compressive pre-stress introduced at the glass edge surface that will in service be exposed to tensile stresses induced by bending. Where Aeq is the equivalent cross-sectional area of the beam, e is the eccentricity of the applied pre-load P from the neutral axis, Ic is the moment of inertia of the composite section, and zg,t is the distance of the top glass edge from the neutral axis. Failure mechanisms which may occur at this stage are the following: (1) rupture of the tendon, (2) glass fracture in tension due to the eccentricity of the pre-load, i.e. the hogging bending moment, (3) adhesive failure and (4) glass fracture caused by stress peaks in the load introduction zone at beam ends. The transparent nature of glass limits the use of special anchorage which would provide vertical confinement in order to avoid this type of failure; the design of the end zones requires special attention
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