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ItemModelling damage to glazing and aluminium facades by flying objectsPathirana, Mahil ( 2018)Impact by flying debris in windstorms conditions has been a major contributor to damage to aluminium, glass and other types of building facades. However, no codified design guidelines are currently available to quantify the required impact resistance of an aluminium or glazing panel for a given impact action. This research presents the development of an analytical model for assessing impact induced damage (permanent deformation or perforation) to an aluminium panel for given mass of the projectile (debris) object, velocity of impact, and importantly, parameters characterising the stiffness properties of the windborne impactor object. Stochastic methodology is developed to simulate the risk of fracture of the glass panel when subject to the transient action of point contact that can be generated by the impact of hailstones or windborne solid debris particles. The introduced simulation methodologies are able to predict the impact resistance capacity of glazing and aluminium panels without conducting impact experiments. The aim of introducing the proposed simulation model is bringing about significant savings by waiving away the need of conducting repetitive physical experimentation on panels of different dimensions, and at different rates of loading.
ItemPerformance of glass facade systems subjected to blast loadsLumantarna, Raymond ( 2014)The first function of a façade system is to provide protection from external hazards to building occupants. However, under extreme external hazards such as blast load, the façade system would be the weakest link of the building, whereby failure would lead to extensive injuries due to projectiles and blast pressure ingress into the building. Although extensive literature and a formal design guideline for structures to resist blast pressures (UFC 3-340-02) are available, provisions are limited because they are based only on panel resistance rather than the overall façade system, which would lead to over-design or under-design in some cases. The performance of an actual façade system as opposed to a façade panel component has not been investigated in detail. This thesis presents the first study to investigate the behaviour of glass façades under blast pressures as a whole system. The research is divided into four major components; i) development of a performance assessment framework for façade components; ii) quantification of blast loading parameters and their variabilities; iii) dynamic behaviour of façade system when subjected to blast pressures; and iv) establishment of the influence of practical engineering design parameters on the performance of the glazing façade system. Quantification of the blast loading parameters was carried out to establish the blast parameters to be applied to the façade system. This quantification stage included data analysis of full-scale blast trials and pre-existing data. The results from the blast trials were used to carry out an extensive assessment of the reliability of numerical approaches and standardised charts provided in UFC 3-340-02. The UFC 3-340-02 charts have enabled engineers to establish blast parameters to be applied on structural components. However, a lack of understanding of the experiments behind the UFC 3-340-02 approach has led to the misconception that the approach would lead to an accurate and precise value as opposed to best estimates. This component of the thesis aims to systematically take into account the uncertainties in blast parameter predictions into the performance assessment of façade systems. One of the main issues surrounding blast performance analysis is that it is always approached exclusively from one angle. Analyses are often carried out with a deterministic approach without consideration of the reliability component of the phenomenon. On the other hand, the risk assessment approach often neglects the subtle nuances of the detailed response of the structural component. In this thesis, a performance assessment framework, which is capable of systematically incorporating the reliabilities of blast data and material properties into performance indicators in the form of pressure-impulse curves, is developed. In design practice, blast parameters are often simplified to fit uniform pressure, with a triangular load time history in the standardised design method. Similarly, the structural response of a façade component is generally simplified into a single degree of freedom (SDOF) analysis approach of a glazing panel. These simplifications may lead to inaccurate results in dynamic response analysis. Blast pressure parameters, such as blast wave non-planarity and negative phase of the blast, would generally be neglected, whilst frame interaction with the glass panel and stress concentration due to higher mode response would also generally be ignored in the simplified analysis. The comparison between the results of the simplified analysis approach and the detailed numerical simulation of the façade system response to blast pressures shows that the simplified approach will lead to under-design in the impulsive response region, whilst the simplified approach appears to be adequate for the quasi-static response region. In the development of the pressure-impulse curve, a strong relationship between the time component of blast pressure and the natural frequency of the structure can be observed. A better understanding of the relationship between the frequency content of blast pressure waves and the response of a structure can be established by correlating the frequency content of the blast wave to the natural frequency of vibration of the structure. The findings of the investigation indicate that a common spectral content can be defined, and that the information can be extrapolated to partially establish the pressure-impulse curve. This is the first time the spectral analysis approach is used to define the pressure-impulse curve. Numerical analyses and parametric studies were carried out to establish the critical engineering design parameters that influence the performance of a glass façade system. The findings of the analysis suggest that the use of a simplified analysis approach may lead to ‘unsafe’ design under the impulsive loading condition, whilst the simplified approach appears to be suitable for quasi-static loading condition. The analysis also indicates that the flexibility of the framing system has a significant influence on the performance of the façade as a system. The findings of the investigation indicate that a flexible framing system improves the blast resistance of the façade system to an extent, whilst a framing system, which is too flexible, leads to a reduction of the blast resistance of the façade system. This highlights the need to consider the influence of the framing system in design.