Ioannis Katsivalis | University of Limerick (original) (raw)

articles by Ioannis Katsivalis

Glass/steel adhesive joints are being used increasingly in the construction industry as they offe... more Glass/steel adhesive joints are being used increasingly in the construction industry as they offer significant structural advantages. While humidity and elevated temperatures are known to lead to the degradation of both the bulk adhesive materials and the bonded interfaces, quantification and prediction of the degradation effects are currently lacking. In this paper, the effects of elevated temperatures and humidity were determined and predicted by employing a combined experimental and numerical methodology. Bulk material and interface characterisation tests were performed to quantify the degradation of the bulk material properties and the glass/steel interfaces. Two numerical methodologies were devised and compared based on their ability to predict failure of glass/steel adhesive joints following environmental exposure, namely a continuum mechanics approach based on the bulk properties of the adhesive, and a cohesive zone modelling approach that assesses damage and failure based on the glass/steel interface properties. The results highlight the significantly different relative contributions of bulk property and interface degradation depending on the type of adhesive used.

Mild steel/tempered glass adhesive joints are becoming a common occurrence in the construction in... more Mild steel/tempered glass adhesive joints are becoming a common occurrence in the construction industry. A numerical parametric study for adhesive property optimisation is conducted and determines strength and ductility as the main parameters affecting the joint performance. Numerical simulations include adhesive pressure-sensitivity, plasticity and failure modelling and are also used to further investigate onset and progression of damage leading to failure of the joints. Following this, the market of structural adhesives is scanned, resulting in the identification of an adhesive system that aligns with the ‘optimal’ strength and ductility parameters identified from the parametric study. The chosen adhesive system is experimentally compared and benchmarked against a brittle and a ductile adhesive in steel/glass adhesive joints subjected to four different load-cases. It is demonstrated that the proposed modelling methodology yields accurate predictions of the adhesive and adherend stress states and failure behaviour for the four different load-cases, thus highlighting the model’s ability to predict the response and failure of all three adhesives and tempered glass.

This paper investigates the use of bolted and brittle/ductile adhesive connections in glass struc... more This paper investigates the use of bolted and brittle/ductile adhesive connections in glass structures. Two benchmark designs of shear connections are introduced and tested experimentally in quasi-static tensile tests. The designs consist of tempered glass and aluminium substrates while steel splices are used for the load application. In addition, material characterisation testing for the glass and the adhesive is performed and the outputs are used for the numerical simulation of the same joints. Pressure-sensitive, plasticity and failure models are introduced and calibrated to accurately capture the behaviour of the adhesives. Good agreement between the experimental observations and numerical predictions is achieved. The results show that both types of adhesive joints outperform bolted joints while counter-intuitively the lower strength ductile adhesive achieves consistently higher joint strength compared to the brittle adhesive. The numerical analyses highlight that while brittle adhesive joints fail once the fracture strain of the adhesive has been reached, while for ductile adhesives an extensive plastic zone develops near the areas of stress concentrations thereby delaying the damage initiation.

Glass/steel adhesive joints are being used increasingly in the construction industry as they offe... more Glass/steel adhesive joints are being used increasingly in the construction industry as they offer significant structural advantages. While humidity and elevated temperatures are known to lead to the degradation of both the bulk adhesive materials and the bonded interfaces, quantification and prediction of the degradation effects are currently lacking. In this paper, the effects of elevated temperatures and humidity were determined and predicted by employing a combined experimental and numerical methodology. Bulk material and interface characterisation tests were performed to quantify the degradation of the bulk material properties and the glass/steel interfaces. Two numerical methodologies were devised and compared based on their ability to predict failure of glass/steel adhesive joints following environmental exposure, namely a continuum mechanics approach based on the bulk properties of the adhesive, and a cohesive zone modelling approach that assesses damage and failure based on the glass/steel interface properties. The results highlight the significantly different relative contributions of bulk property and interface degradation depending on the type of adhesive used.

Mild steel/tempered glass adhesive joints are becoming a common occurrence in the construction in... more Mild steel/tempered glass adhesive joints are becoming a common occurrence in the construction industry. A numerical parametric study for adhesive property optimisation is conducted and determines strength and ductility as the main parameters affecting the joint performance. Numerical simulations include adhesive pressure-sensitivity, plasticity and failure modelling and are also used to further investigate onset and progression of damage leading to failure of the joints. Following this, the market of structural adhesives is scanned, resulting in the identification of an adhesive system that aligns with the ‘optimal’ strength and ductility parameters identified from the parametric study. The chosen adhesive system is experimentally compared and benchmarked against a brittle and a ductile adhesive in steel/glass adhesive joints subjected to four different load-cases. It is demonstrated that the proposed modelling methodology yields accurate predictions of the adhesive and adherend stress states and failure behaviour for the four different load-cases, thus highlighting the model’s ability to predict the response and failure of all three adhesives and tempered glass.

This paper investigates the use of bolted and brittle/ductile adhesive connections in glass struc... more This paper investigates the use of bolted and brittle/ductile adhesive connections in glass structures. Two benchmark designs of shear connections are introduced and tested experimentally in quasi-static tensile tests. The designs consist of tempered glass and aluminium substrates while steel splices are used for the load application. In addition, material characterisation testing for the glass and the adhesive is performed and the outputs are used for the numerical simulation of the same joints. Pressure-sensitive, plasticity and failure models are introduced and calibrated to accurately capture the behaviour of the adhesives. Good agreement between the experimental observations and numerical predictions is achieved. The results show that both types of adhesive joints outperform bolted joints while counter-intuitively the lower strength ductile adhesive achieves consistently higher joint strength compared to the brittle adhesive. The numerical analyses highlight that while brittle adhesive joints fail once the fracture strain of the adhesive has been reached, while for ductile adhesives an extensive plastic zone develops near the areas of stress concentrations thereby delaying the damage initiation.