Fibre reinforced polymer (FRP) materials have been a material of interest in the field of structural engineering due to their superior mechanical properties such as high strength to weight ratios and resistance to environmental degradation and corrosion. Even though research has established the material to be a viable option for construction they are highly susceptible to elevated temperatures. There are several systems available on the market and a great deal of research needs to be conducted to investigate the change in properties and different behaviour at elevated temperature to serve as a better basis for design. The main objective of this project and the experimental program presented in this thesis is to study the thermo mechanical properties of the available systems on the market. A summary of the previous research done in the area covering other materials is presented providing an introduction to the behaviour of different systems under elevated temperature. Then, two different experimental programs are presented. The first considers the glass transition temperature and thermal decomposition of the different systems and the second examines the tensile strength of the different systems under different temperature regimes. The results of both experimental programs are presented and then a connection between the thermo mechanical properties of the resins and the overall strength of the system is established. The research demonstrates that the glass transition temperature of the resin used for an FRP strengthening system is the main determinant of the performance at high temperatures. / Thesis (Master, Civil Engineering) -- Queen's University, 2011-06-16 09:21:32.228

The synthesis and characterization of phosphorus containing poly(arylene ether)s were investigated to determine the effect of phosphorus upon the thermal stability, mechanical strength, and fire resistance of thermoplastics. Phosphorus containing activated aromatic dihalides and bisphenols were synthesized in high purity. These monomers were successfully polymerized via nucleophilic aromatic substitution to afford high molecular weight polymers. It was determined that by incorporating the phosphine oxide moiety into the polymer backbone certain properties of the resulting poly(arylene ether)s were substantially improved, such as an increase in T_g, thermal stability in air, modulus, and char yield, compared with control poly(arylene ether sulfone)s. The high char yields obtained for these polymers in air, along with observed intumescence indicates that these materials have improved fire resistance. Preliminary cone calorimetry measurements support this conclusion. In addition, the phosphine oxide group in the backbone was reduced to a phosphine and successfully converted to a phosphonium bromide ionomer. The resulting system was further chemically modified to ionically bond second-order nonlinear optical chromophores to the backbone of selected poly(arylene ether)s. Initial results on corona poling of cast film at low temperature produced stable second harmonic generation in these materials, indicating that they may have promise in nonlinear optical applications. / Ph. D.

Until recently, investigations on the fire resistance of steel joints have been neglected by structural engineers under the arguments that the design resistance of connections at room temperature is usually higher than the resistance of the connected members and that the temperature increases more slowly in the joint zone (high concentration of mass, low exposure to radiative fluxes) than in the adjacent beams and columns. However, brittle failures of connection components have been observed especially during the cooling phase of real fires for two main reasons: the high sensitive and nonreversible character of the resistance of bolts and welds at elevated temperatures and the development of high tensile thrusts. The present thesis is a contribution to the understanding of the thermomechanical behaviour of simple connections in steel beam-to-column joints subjected to natural fire conditions, with a special attention to the behaviour of these connections during the cooling phase. The distribution of temperature in joints has been analysed by use of numerical models built in SAFIR software. The simplified methods presently mentioned in the Eurocodes are discussed and new methods, calibrated on the results of numerical simulations, are proposed in the present work to predict the temperature profile in steel beams and joints covered by a flat concrete slab under fire. An existing method aimed at evaluating the distribution of internal forces in restrained steel beams (and by extension, in joints) under natural fire has been analysed in detail. Several modifications have been added in order to improve his method and to extend its field of application. The final version of this analytical method has been implemented and validated against numerical results. An experimental programme aimed at characterising the mechanical behaviour of bolts and welds under heating and subsequent cooling is described in the present thesis. The properties of the tested specimens, the thermal loading applied to these specimens, the test set-ups and the results of the tests are reported in detail. Mechanical models for bolts loaded in tension or in shear have been calibrated on the experimental results. The loss of resistance of bolts and welds due to their non-reversible behaviour under heating and subsequent cooling has been quantified. Finally, a large part of the thesis is dedicated to the development of component-based models representing the action of common simple connections under natural fire conditions and to the analysis of the behaviour of these connections as a part of a sub-structure or large-scale structure. These simple models can be used for parametric analyses because it conciliate a reasonable time of definition of the data, an acceptable time of simulation and a good degree of accuracy of the results. Recommendations for the design of connections have been defined. The ductility of connections has a major influence on the occurrence of connection failures and classes of ductility for connections, dependant of the fire loading, have been defined in this work. / Jusque très récemment, la recherche sur la résistance au feu des assemblages métalliques a été délaissée par les ingénieurs sous le prétexte que la résistance de calcul des assemblages à froid est habituellement supérieure à celle des éléments connectés et que léchauffement est plus lent dans la zone dassemblage que dans les poutres et colonnes adjacentes (grande concentration de matière, exposition réduite aux flux radiatifs). Toutefois, les ruptures fragiles de composants dassemblages sont observées, notamment durant la phase de refroidissement pour deux raisons principales : caractère sensible et non-réversible des boulons et des soudures aux élévations de température et apparition defforts de traction importants. La présente thèse sinscrit comme une contribution à la compréhension des phénomènes gouvernant le comportement des assemblages simples poutre-poteau sous conditions de feu naturel. Une attention spéciale est portée au comportement de ces assemblages durant la phase de refroidissement. La distribution de température dans les assemblages a été analysée grâce à des modèles numériques mis au point dans le programme SAFIR. Les méthodes simplifiées actuellement mentionées dans les Eurocodes actuels sont discutées et de nouvelles méthodes, calibrées sur les résultats numériques, sont proposées dans ce travail pour prédire le profil de température dans les poutres et assemblages métalliques couverts dune dalle en béton sous feu. Une méthode existante destinée à évaluer la distribution des efforts internes dans les poutres en acier restraintes (et par extension, dans les assemblages) sous feu naturel a été analysée en détail. Plusieurs modifications ont été proposées pour améliorer cette méthode et étendre son champ dapplication. La version finale de cette méthode analytique a été implémentée et validée avec des résultats numériques. Une série de tests expérimentaux destinée à caractériser le comportement mécanique des boulons et des soudures sous échauffement et refroidissement est décrite dans cette présente thèse. Les propriétés des spécimens testés, le traitement thermique qui leur est appliqué, le montage des essais et les résultats obtenus sont rapportés en détail. Des modèles mécaniques pour les boulons soumis à traction ou cisaillement sont calibrés sur les mesures expérimentales. La perte de résistance des boulons et des soudures causée par leur comportement non-réversible sous échauffement et refroidissement a été quantifiée. Finalement, une large part de la thèse a été dédiée au développement de modèles basés sur la méthode des Composantes pour représenter laction des assemblages simples courants sous feu naturel et lanalyse de leur comportement dans une sous-structure ou une structure complète. Ces modèles simples permettent de concilier un temps de définition des données raisonnable, un temps de calcul acceptable et un bon niveau de précision des résultats. Des recommandations pour le dimensionnement des assemblages ont été énoncées. Il est démontré que la ductilité des connections a une influence majeure sur lapparition de ruptures dans les assemblages et des classes de ductilité, dépendant du chargement au feu, ont été définies dans ce travail.

The fire resistance of timber connections is relatively unknown in the construction and design industries even though they are widely used. This research focuses on the fire resistance of nailed, screwed, bolted and self-drilling doweled connections in laminated veneer lumber (LVL) timber. These connections have been found to have high strength under cold or normal temperature but hardly achieved 30 minutes fire rating in the furnace tests. To establish the performance of connections, an investigation was carried out on the compressive strength of connections by having compressive tests using an Instron Testing Machine. Similar connections were tested at simulated fire conditions under constant load in a custom-built furnace. The different fasteners used and the arrangement of the connections gave different connection strengths at ambient and elevated temperature.

Construction with composite materials has become increasingly popular in contemporary structural design for multi-storey residential, commercial, and industrial buildings. As a composite structure, pre-stressed heavy timber buildings offer sustainable, environmentally-friendly advantages over competing construction technologies utilising structural steel and concrete components. Research at the University of Canterbury is continually investigating the performance and behaviour of this composite heavy timber construction assembly. The following research report provides a fire resistance analysis for pre-stressed heavy timber structures that includes: • A comprehensive literature review detailing the fire resistance for pre-stressed heavy timber structural components and typical connections; and • A four-phase series of experiments with epoxy grouted steel threaded rods and proprietary mechanical fasteners to determine the fire resistance properties of steel to wood connections. Laboratory experimentation includes cold testing to determine connection performance at ambient temperature, oven testing to evaluate heating effects on steel to wood connections, cooled testing to determine the residual strength of connections in minor fires and, finally, furnace testing to generate fire resistance design and analysis equations to be utilised for steel to wood connections. Recommendations for the fire performance of connections in pre-stressed heavy timber structures are included in the report.

In predicting the likely behaviour of precast prestressed concrete flooring systems in fire using advanced finite element methods, an improved numerical model using the non-linear finite element program SAFIR has been developed in order to investigate the effects and the interaction of the surrounding structures and has been used extensively throughout this thesis. Note that fire induced spalling is not included in the analysis. In the numerical investigation of the new model, the reinforced concrete topping is modelled as part of the beam elements in order to predict the behaviour of single hollowcore concrete slabs, with various support conditions, under a Standard ISO fire. It is shown that the current approach using tendons that are anchored into the supporting beams leads to a major problem for precast prestressed flooring systems. In order to resolve this problem, a multi-spring connection model has been developed to include the old and new connection systems corresponding to the New Zealand Concrete Standard NZS 3101. The connection model with hollowcore slabs is validated against a published fire test. The investigation on restrained hollowcore floors is performed with various parameters and boundary support conditions. Numerical studies on various boundary support conditions show that the behaviour of hollowcore floors in fire is very sensitive to the existence of side beams. Further investigations on the effects of fire emergency beams, which reduce the transverse curvature of floors to improve fire resistance, are made on 4x1 multi-bay hollowcore floors with different arrangements of theses beams. The numerical studies show that fire emergency beams significantly increase the fire resistance. Code based equations which can calculate the shear resistance and splitting resistance are then introduced. The Eurocode equation can be modified with high temperature material properties to estimate the shear capacity of a hollowcore slab. The modified Eurocode equation which is fit to fire situations validated against the published literature with respect to shear tests in fire. The structural behaviour of single tee slabs having different axial restraint stiffness as well as the variation of axial thrust in fire is then studied. SAFIR analyses of single tee slabs show that fire performance can increase when a web support type is used that has high axial restraint stiffness. A series of test results on prestressed flat slabs conducted in United States are used to validate a simply supported numerical model. The application of multi-spring connection elements is also investigated in order to examine the feasibility of continuity.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Performance based -- structural steel -- fire conditions. Includes bibliographical references (p. 138-141).

I den här kandidatuppsatsen har vi undersökt om korslimmat massivträs brandegenskaper kan förbättrats med rätt sorts lim och med användandet av skyddsskivor. Det senaste årtiondet har byggbranschen blivit mer miljömedvetna och viljan att bygga miljö- och klimatsmart har ökat, detta har medfört ett ökat användande av olika typer av trämaterial. Korslimmat massivträ har utvecklats som ett resultat av detta. Eftersom det är ett nytt byggnadsmaterial finns det mycket forskning kvar att göra, vilket intresserade oss. För att få svar på våra frågor har vi gjort en litteraturstudie för att inhämta kunskap och resultat från tidigare rapporter och artiklar som finns i ämnet. Det vi har kunnat se är att så länge som de individuella lagrena i det korslimmade massivträet inte lossnar ifrån varandra har det i princip samma brandegenskaper som homogent massivträ. Men så fort som det lossnar ifrån varandra stiger förkolningstakten och brandegenskaperna försämras. Det går att förhindra och begränsa dessa försämringar med rätt val av lim och skyddsskivor.  Detta är fördjupningsdelen i ett arbete som också innefattar projektering och dimensionering av ett småhus.

Post-tensioned timber frames have recently been undergoing heavy research and development at the University of Canterbury. The recently developed post-tensioned timber system utilises engineering wood products such as Laminated Veneer Lumber (LVL) and glue laminated timber (Glulam), which are formed into box sections and post-tensioned with high strength steel tendons made from stranded steel wire or solid steel bars. The post-tensioning serves to counteract some of the bending actions imposed on the timber beam from loading through a variety of mechanisms. Previous research has focused on the seismic performance and gravity frame performance of post-tensioned timber, both of which yielded promising results. There is however a commonly perceived increase in fire risk with timber building, particularly multi-storey timber buildings, and the fire performance of post-tensioned timber had not previously been investigated. Therefore, the focus of this research was to investigate the fire performance of post-tensioned timber beams. This was completed through a series of full-scale furnace tests, and the development of a fire resistance design method. Three 4.36m span post-tensioned timber beams were exposed to the ISO 834 standard fire. Each of the test beams were glued box beams made from 63mm LVL and were of varying external dimensions. Each beam was intended to demonstrate a specific failure mechanism at approximately 60 minutes of fire exposure. The failure mechanisms demonstrated were a shear failure in the lower corner of due to corner rounding, and a combined bending and compression failure at the end of the beam. These failure mechanisms are unique to post-tensioned timber in fire. The results of the experimental testing were used to validate and refine the proposed fire resistance calculation. Also tested during the full-scale testing were five different forms of anchorage fire protection. These were tested as a secondary objective, but useful thermal data was collected. Through the full-scale testing and the calculation method development it was found that it is important to consider shear during fire design. The post-tensioning increases the bending capacity of a beam but doesn’t affect its shear capacity, therefore when more loading is applied to utilise the increased bending capacity the shear action is increased which leads to shear governing the design in many cases. It is also important to consider shear not only in the webs at the centroid where the shear flow is greatest but also in the lower corners, which can become much thinner than the webs. Without calculation it is not possible to determine where the shear stress will be greatest and therefore both the web and the lower corners need to be checked. It was also found that as the timber section chars on three sides the post-tensioning eccentricity increases which can lead to the moment at the end of the beam becoming critical. Other failure mechanisms which need to be checked include, combined bending and compression at mid span, and tension in the bottom most fibre at mid span. It was found that the proposed calculation method, when used with a char rate of 0.72mm/min and an additional allowance of 7mm for temperature-affected timber beneath the char layer, provided good predictions of the failure times for the full-scale experiments.

The ability to predict the temperatures in protected steel structures is of vital importance for the progress of fire safety engineering. Existing methods are limited in several respects, typically being computationally restricted and limited to examination of the performance of specific components. This thesis investigates a generalised CFDbased methodology for thermal analysis of structural members in fire, developed to overcome these limitations. A novel methodology has been developed, known as GeniSTELA (Generalised Solid ThErmal Analysis), which computes a “steel temperature field” parameter in each computational cell. The approach is based on a simplified 1D model for heat transfer, together with appropriate corrections for 2D and 3D effects, to provide a quasi- 3D solution with a reasonable computational cost. GeniSTELA has been implemented as a submodel within the SOFIE RANS CFD code. The basic operation of the model has been verified and results compared to the empirical methods in EC3, indicating a satisfactory performance. The role of the surface temperature prediction has been examined and demonstrated to be important for certain cases, justifying its inclusion in the generalised method. Validation of the model is undertaken with respect to standard testing in fire resistance furnaces, examining the fire ratings of different practical protection systems, and the BRE large compartment fire tests, which looked at protected steel indicatives in full-scale post-flashover fires; in both cases, a satisfactory agreement is achieved. Model sensitivities are reported which reveal the expected strong dependencies on certain properties of thermal protection materials.