Civil Engineering - Theses
Permanent URI for this collection
Search Results
1 - 2 of 2
-
ItemFire performance of GFRP facade systems( 2015)Glass façades became preferable in contemporary architecture in last few decades due to its superiority in transmitting light and aesthetic appearance. In the recent past, more attention has been transformed to alternative “greener” materials like fibre reinforced polymer composites (FRPCs). Metallic materials require high amount of energy owing to their manufacture at extremely high temperature. Furthermore, FRPC has lighter weight than any type of aluminium and steel, which surpasses one advantage of aluminium and steel in buildings. Lower weight and higher strength are two critical key properties that make FRPC “greener” than aluminium and steel. However, the fire performance of FRPC facade systems has not been systematically investigated in recent research. Fire retardancy is an issue as FRPC is sensitive to elevated temperatures and the failure of the composite structure should be studied comprehensively to ensure the security for the occupants in fire incidents. Consequently, it is important to conduct a research which focuses on the performance of FRPC as a member of facade systems to identify the potential risks, to provide basic guidelines for appropriate FRPC in building application as well as to offer solutions for FRPC facades to meet the available standards for building materials. This thesis presents analytical, experimental and numerical investigations of fire performance of FRPC façades. Experimental testing is conducted to evaluate the performance of the material in accordance with safety codes and standards as well as to validate numerical simulation. Numerical simulation, in turn, accounts for evaluations where experimental testing is limited owing to cost and time commitment. The analytical study is conducted to provide the background theories required for the research and to design the experimental testing and support numerical simulation. These components are integrated in Chapter 3 – 7 to provide an understanding of the influence of flame retardants and generally the performance of GFRP composite façades subjected to fire conditions. These five main chapters consist of peer reviewed journal publications which have been either published or under review in international science and engineering journals. FRPCs enable the design of complex façade systems with low embodied energy, thus they have drawn substantial attention from façade designers worldwide. Nevertheless, there are many types of FRPCs with varying properties and manufacturing costs, resulting in some difficulty in selecting the suitable materials for the façade elements. Additionally, one of the key drawbacks of FRPCs is their relatively low fire resistance, which still requires comprehensive investigations in order to be applied in façade systems subjected to strict fire safety specifications. To address these concerns, the thesis explores the potential applications of FRPCs in modern façade systems, with a special focus on their fire performance. A case study of the fire performance of GFRPs is conducted numerically on a fire dynamic model established for glass fibre reinforced polyester, vinyl ester, epoxy and phenol composites without flame retardants in order to achieve a rapid assessment on the practicability of this configuration. A commercially available flame retardant, namely aluminium trihydroxide, is also tested and simulated comprehensively. The high concentration of conventional flame retardant triggers failure in the manufacture and deters other properties such as mechanical strength. Nanoclay is introduced in this study, as a novel flame retardant for glass fibre reinforced polymer (GFRP) composite. A comprehensive study covering types of thermosetting resins, types of nanoclay at different concentrations and methods to incorporate nanoclay into the composite is successfully conducted to predict the optimum combination. An analytical method using Taguchi design of experiment is employed with the newly proposed two-step GLM ANOVA. Resin and clay types are found to have significant effects on the ratio of peak of heat release rate (PHRR) to time to reach PHRR (Tp) as well as the total heat release (THR) responses of the composite. The fabrication procedure using ultrasonic agitation seems to yield better fire performance due to the better nanoclay distributions. Various challenges in the modelling include designing the accurate simulation of the combustion process for the multilayer and multi-materials composition such as the organoclay-composite. The proposed Component-layer model addresses the aim to capture very well the fire growth index (FGI) evolution and the FGI peak value. The validated analytical-numerical model is then applied in full-scale fire scenarios specified in ISO 9750-1:2013 and a selected case study (City Office building in Utretch, Netherlands). This building is one of the first buildings in the world integrated with GFRP façade and results have shown that the presence of nanoclay at 5% concentration prevents flash-over from happening and also the flame from spreading in the horizontal direction of the GFRP façade. Important parameters relevant to building members subjected to fire, in all the selected configurations of the City Office building are found to be well below the threshold to be used in building environment according to EN 13501-1:2007.
-
ItemPerformance of glass facade systems subjected to blast loads( 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.