Experimental and numerical analysis of traditional wooden glass windows subject to extraordinary dynamic loads

Abstract

Traditional wooden windows are still prominently present today among the glass parts of older, still-used buildings. Increasingly often, they must withstand extraordinary dynamic loads such as explosions, bird collisions or various natural disasters. From a mechanical standpoint, their resistance is a significant drawback, especially when under the dynamic impact loads to which they are subjected in these extreme situations. To increase the resistance of glass window infills, various safety features are currently in use. One of them is polyethylene terephthalate-based safety foil (PET). However, its effect on the load-bearing capacity of glass is questionable. In terms of the background of the research, it can be stated that a number of research teams around the world have addressed the partial issues of window system resistance in depth. A more comprehensive connection of individual analyses and a focus on “traditional wooden windows” in relation to explosion, impact and additional foil reinforcement has not yet been performed. The aim of this paper is to compare the resistance of the glass infills of traditional wooden windows subjected to extraordinary dynamic load in both cases – before and after their reinforcement with safety foil. In the experimental phase, both tested samples are subjected to hardbody impact and explosion. An essential part of research in multiple branches of dynamics is currently the linking of experimental and numerical methods. The methodology used to achieve the research objective consists of two fundamental approaches: an in-lab experiment correlated with analytical tools in order to tune the inputs for the Finite Element Method (FEM) model, and an in-situ experiment compared with the tuned FEM model to derive conclusions for practice and further research. The paper provides a verification of the experimentally obtained parameters by numerical modeling based on the finite element method in the ANSYS Workbench system interface. One of the main results of the research presented in this paper was a tuned computational model of a traditional wooden window in terms of its behavior towards explosion and hard body impact, which clearly identifies the problems and challenges of modelling its individual structural parts. One of the main conclusions of the paper is the minimal effectiveness of the PET foil for the static load-bearing capacity of the traditional wooden window, its slightly increased damping in dynamic response to extreme impact loads and its high effectiveness in protecting against shattering glass fragments at the collapse of the glass infill. These conclusions are supported by detailed analyses of a series of 7 pendulum test measurements under laboratory conditions, 6 explosion measurements of two different explosives, and the identification of 6 natural modes and natural frequencies of vibration.