Lorenzo Ruggero Piscitelli
Serviceability and post-failure behaviour of laminated glass structural elements [Tesi di dottorato]

Structural laminated glass elements are being used ever more frequently in the construction industry, following a growing architectural trend that looks for light and transparency. Nevertheless, an analysis of both regulatory and scientific state-of-the-art reveals several fields of inquiry which could benefit from deeper investigations. Namely, properties of plastics used as interlayer materials within the glass plies are scarcely investigated, professionals being far from unanimous on reliable techniques for comparing different materials on the same grounds. Yet, such knowledge is needed for reliable designs, especially in structural applications. This manuscript presents the results of a multi-scale experimental research on the mechanical response of three interlayers: PVB, SG and DG41. The former has been the standard in glass lamination industry, while the latter two are more recent and supposedly more performing from a mechanical point of view. The hyperelastic behaviour is studied with simple tensile tests on interlayer specimens; in the end, a novel generalized response model is proposed, which can be tuned to replicate the complex short-term and finite-strain response of any thermoplastic using few coefficients. Also, viscoelastic parameters of interlayers play an essential role in the global long-term laminated glass elements response. The temperature-dependent viscoelastic problem is investigated on a larger scale, using double-lap laminated glass joints under compressive loadings. Tests were performed on specimens made of three glass plies under long-term imposed actions in a temperature range between 0? and 60?. An existing procedure was further developed, to provide insight on both creep and relaxation properties. Finally, calibrated Prony series for viscoelastic models are provided together with Williams Landel Ferry coefficients for time-temperature superposition, allowing to model the viscoelastic responses of the three interlayer materials at arbitrary temperatures. Limits and reliability of such models are discussed; simplified and ready-to use tables are provided. An analysis on the correlation between mechanical actions and loss of adhesion is performed. The third-level of the experimental analyses investigates the mechanical behaviour of progressively damaged, full-scale laminated glass beams. Risk analyses followed by fail-safe designs are often mentioned by standards and technical documents, but few studies have been carried out on the post-failure performance and effects of laminated beams made with tempered glass plies. After partial failure, the load-bearing capacity depends on the interlayers ability to generate coupling effects among fractured and undamaged glass elements through adhesion and its own mechanical properties. Results from dynamic and static tests are compared and the tension stiffening effect of interlayers in partially damaged elements is investigated. An equivalent thermal expansion is proposed to model the mutual effects which are generated among broken and intact plies in the event of partial failure. Further tests have been carried out in fully damaged conditions, to evaluate the residual load-bearing capacity and the effects of ageing such conditions. Uniaxial tensile and compressive test on fully damaged laminated glass specimens are performed. Results are used to model the response of fully damaged beams. In the last part of the manuscript, examples of application of newly found results are used in possible laminated glass structural designs: applications are provided for cold-bending techniques and post-failure safety assessments.

diritti: info:eu-repo/semantics/openAccess
In relazione con info:eu-repo/semantics/altIdentifier/hdl/2158/1133153
Prof. Maurizio Orlando, Prof. Giovanna Ranocchiai, Prof. Harald Kloft

Tesi di dottorato. | Lingua: Inglese. | Paese: | BID: TD18037568