Infoscience

Thesis

Laminated Connections for Structural Glass Applications

The demand for architectural transparency has drastically increased structural use of glass in buildings and constructions. Connections between structural glass components represent one of the main critical aspects of glass engineering. In the last years, the use of adhesive connections in structural applications has been considered promising because avoids the drilling process and the high contact stress intensifications of bolted connections. This work focuses on a novel typology of adhesive connections known as laminated adhesive connections. Two transparent adhesive materials are used: the ionomer SentryGlas® (SG) from Kuraray and the Transparent Structural Silicon Adhesive (TSSA) from Dow Corning. In this work, the mechanical behaviour of laminated connections at varying temperature, strain rate and loading condition is studied by experimental, analytical and numerical investigations. The mechanical behaviour of laminated connections under shear loading is firstly experimentally investigated at varying strain rate and temperature. A variational approach is proposed to analytically describe the non-linear stress field distribution in the adhesive. Numerical analyses are then performed to quantify stress peaks and the non-linear the stress field distribution in the connection over the three dimensions. Prediction models are proposed for the computation of the shear resistance of laminated connections. The mechanical behaviour of laminated connections under tensile loading is then experimentally investigated at varying strain rate and temperature. An analytical study is performed to derive the effect of the confinement state on the stress state of the adhesive, with particular attention to the hydrostatic component of the stress tensor. FEM analyses are then used to compute the 3D temperature-dependent stress field distribution, the deviatoric and hydrostatic components of the stress tensor and to quantify the stress peaks in the adhesive. Prediction models are proposed for the computation of the tensile resistance of laminated connections. The analytical development of a new generalized failure criterion is then presented. In this study, a novel four-dimensional model that account for a generic stress state is derived. The governing equation is expressed as a function of the three-dimensional stress tensor, the temperature and the strain rate. Both deviatoric and hydrostatic energetic components are taken into consideration by means of a non-linear function of the two contributions. The proposed model is defined over four independent dimensions: the equivalent stress, the hydrostatic stress, the strain rate and the temperature. At varying strain rate and temperature, the surface evolves as a function of the strain rate and temperature values, following either a linear or logarithmic or hyperbolic-tangent law depending on the material. Additional experimental investigations are also performed by tensile-torsion tests to validate the proposed model at varying value of triaxiality. The mechanical behaviour of embedded laminated connections under pull-out force is finally experimentally investigated at different temperatures. Numerical finite element analyses are carried out and the results compared to the varying failure mode and failure location at different temperatures. A new prototype of a glass components with embedded laminated connections is proposed, focusing on post-breakage behaviour and redundancy.

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