Some solutions to obtain very efficient separations in isocratic and gradient modes using small particles size and ultra-high pressure.

The UHPLC strategy which combines sub-2 microm porous particles and ultra-high pressure (>1000 bar) was investigated considering very high resolution criteria in both isocratic and gradient modes, with mobile phase temperatures between 30 and 90 degrees C. In isocratic mode, experimental conditions to reach the maximal efficiency were determined using the kinetic plot representation for DeltaP(max)=1000 bar. It has been first confirmed that the molecular weight of the compounds (MW) was a critical parameter which should be considered in the construction of such curves. With a MW around 1000 g mol(-1), efficiencies as high as 300,000 plates could be theoretically attained using UHPLC at 30 degrees C. By limiting the column length to 450 mm, the maximal plate count was around 100,000. In gradient mode, the longest column does not provide the maximal peak capacity for a given analysis time in UHPLC. This was attributed to the fact that peak capacity is not only related to the plate number but also to column dead time. Therefore, a compromise should be found and a 150 mm column should be preferentially selected for gradient lengths up to 60 min at 30 degrees C, while the columns coupled in series (3x 150 mm) were attractive only for t(grad)>250 min. Compared to 30 degrees C, peak capacities were increased by about 20-30% for a constant gradient length at 90 degrees C and gradient time decreased by 2-fold for an identical peak capacity.

Precast Concrete Elements for Accelerated Bridge Construction Final Report Volume 3. Laboratory Testing, Field Testing, and Evaluation of a Precast Concrete Bridge: Black Hawk County,v January 2009

The importance of rapid construction technologies has been recognized by the Federal Highway Administration (FHWA) and the Iowa DOT Office of Bridges and Structures. Black Hawk County (BHC) has developed a precast modified beam-in-slab bridge (PMBISB) system for use with accelerated construction. A typical PMBISB is comprised of five to six precast MBISB panels and is used on low volume roads, on short spans, and is installed and fabricated by county forces. Precast abutment caps and a precast abutment backwall were also developed by BHC for use with the PMBISB. The objective of the research was to gain knowledge of the global behavior of the bridge system in the field, to quantify the strength and behavior of the individual precast components, and to develop a more time efficient panel-to-panel field connection. Precast components tested in the laboratory include two precast abutment caps, three different types of deck panel connections, and a precast abutment backwall. The abutment caps and backwall were tested for behavior and strength. The three panel-to-panel connections were tested in the lab for strength and were evaluated based on cost and constructability. Two PMBISB were tested in the field to determine stresses, lateral distribution characteristics, and overall global behavior.

Two thermal methods to measure the energy fluence of a brief exposure of diagnostic x rays

This paper describes two simple thermal methods for measuring the energy fluence in J/cm 2 from a diagnostic x-ray exposure. Both detectors absorb essentially 100% of the radiation and give a signal that is directly proportional to the energy fluence of the x-ray beam. One detector measures the thermal effect when a pulse of x rays is totally absorbed in the pyroelectric detector of lead-zirconium-titanate (PZT). The other detector measures the expansion of a gas surrounding a lead disk detector in a photoacoustic chamber. The increased pressure of the gas is transmitted through a 1-mm duct to a sensitive microphone. Both detectors have previously been used to measure the energy fluence rate of continuous x-ray beams in the same energy region using a chopped beam and a lock-in amplifier. Measurement of the energy fluence of a pulse of radiation eliminates the need for the beam chopper and lock-in amplifier and results in a simple, rugged, and inexpensive dosimeter. Either method can be combined with the area of the beam to give an estimate of the imparted energy to the patient from a diagnostic x-ray exposure.

Análise experimental de lajes lisas unidirecionais de concreto armado ao puncionamento simétrico ou assimétrico

O puncionamento é normalmente uma situação crítica no projeto de lajes lisas de concreto armado. Segundo várias normas de projeto, o puncionamento se desenvolve de maneira ainda mais desfavorável nos casos onde o carregamento atua de forma assimétrica, graças a momentos desbalanceados na ligação laje-pilar. Visando avaliar as recomendações normativas para estas situações, foram ensaiadas 12 lajes lisas unidirecionais de concreto armado ( c f ' entre 36 e 58 MPa) submetidas a puncionamento simétrico ou assimétrico. As lajes apresentavam dimensões de (1.800 x 1.800 x 110) mm com carregamento sendo aplicado através de uma chapa metálica simulando um pilar quadrado com (85 x 85 x 50) mm. O trabalho teve como variáveis, além da posição de carregamento, a taxa de armadura na direção transversal, objetivando avaliar a influência destas armaduras na resistência última ao puncionamento de lajes lisas unidirecionais. São apresentados e analisados os resultados dos deslocamentos verticais, deformações na superfície de concreto e nas armaduras de flexão, mapas de fissuração, cargas últimas e modos de ruptura observados. Apresentam-se ainda os resultados da avaliação das recomendações de 6 normas de projeto, sendo 3 européias e 1 norte americana, além das versões de 1978 e 2003 da norma brasileira para projeto de estruturas de concreto. Foi realizada também uma análise numérica utilizando o Método dos Elementos Finitos para idealizar o comportamento das lajes, comparando-se os resultados desta análise elástica com aqueles verificados experimentalmente. Os resultados indicaram que, ao contrário do que as normas prescrevem, a resistência ao puncionamento não diminui de forma linear com o aumento da excentricidade do carregamento, com a flexão influenciando significativamente na resistência última ao puncionamento. Os resultados indicam também que, mesmo em lajes unidirecionais, a taxa de armadura transversal apresenta influência significativa na distribuição dos esforços na laje, interferindo na resistência à punção.

Artificial Immune Systems with Negative Selection Applied to Health Monitoring of Aeronautical Structures

In this paper we present a system for aircraft structural health monitoring based on artificial immune systems with negative selection. Inspired by a biological process, the principle of discrimination proper/non-proper, identifies and characterizes the signs of structural failure. The main application of this method is to assist in the inspection of aircraft structures, to detect and characterize flaws and decision making in order to avoid disasters. We proposed a model of an aluminum beam to perform the tests of the method. The results obtained by this method are excellent, showing robustness and accuracy.

Nonlinear ball and beam control system identification

The Ball and Beam system is a common didactical experiment in control laboratories that can be used to illustrate many different closed-loop control techniques. The plant itself is subjected to many nonlinear effects, which the most common comes from the relative motion between the ball and the beam. The modeling process normally uses the lagrangean formulation. However, many other nonlinear effects, such as non-viscous friction, beam flexibility, ball slip, actuator elasticity, collisions at the end of the beam, to name a few, are present. Besides that, the system is naturally unstable. In this work, we analyze a subset of these characteristics, in which the ball rolls with slipping and the friction force between the ball and the beam is non-viscous (Coulomb friction). Also, we consider collisions at the ends of the beam, the actuator consists of a (rubber made) belt attached at the free ends of the beam and connected to a DC motor. The model becomes, with those nonlinearities, a differential inclusion system. The elastic coefficients of the belt are experimentally identified, as well as the collision coefficients. The nonlinear behavior of the system is studied and a control strategy is proposed.

Implants with Original and Non-Original Abutment Connections

AIM: To test in vitro the mechanical resistance, rotational misfit and failure mode of three original implant-abutment connections and to compare them to two connections between non-original abutments connected to one of the original implants. MATERIAL AND METHODS: Three different implants with small diameters (3.3 mm for Straumann Roxolid, 3.5 mm for Nobel Biocare Replace and Astra Tech Osseospeed TX) were connected with individualized titanium abutments. Twelve implants from each system were connected to their original abutments (Straumann CARES, Nobel Biocare Procera, Astra Tech Atlantis). Twenty-four Roxolid implants were connected with non-original abutments using CAD/CAM procedures from the other two manufacturers (12 Nobel Biocare Procera and 12 Astra Tech Atlantis). For the critical bending test, a Zwick/Roell 1475 machine and the Xpert Zwick/Roell software were used. RESULTS: The rotational misfit varied when comparing the different interfaces. The use of non-original grade V titanium abutments on Roxolid implants increased the force needed for deformation. The fracture mode was different with one of the original connections. CONCLUSIONS: Non-original abutments differ in design of the connecting surfaces and material and demonstrate higher rotational misfit. These differences may result in unexpected failure modes.

Optimal beam forming for laser beam propagation through random media

Focusing optical beams on a target through random propagation media is very important in many applications such as free space optical communica- tions and laser weapons. Random media effects such as beam spread and scintillation can degrade the optical system's performance severely. Compensation schemes are needed in these applications to overcome these random media effcts. In this research, we investigated the optimal beams for two different optimization criteria: one is to maximize the concentrated received intensity and the other is to minimize the scintillation index at the target plane. In the study of the optimal beam to maximize the weighted integrated intensity, we derive a similarity relationship between pupil-plane phase screen and extended Huygens-Fresnel model, and demonstrate the limited utility of maximizing the average integrated intensity. In the study ofthe optimal beam to minimize the scintillation index, we derive the first- and second-order moments for the integrated intensity of multiple coherent modes. Hermite-Gaussian and Laguerre-Gaussian modes are used as the coherent modes to synthesize an optimal partially coherent beam. The optimal beams demonstrate evident reduction of scintillation index, and prove to be insensitive to the aperture averaging effect.

A LAPLACE TRANSFORM PAIR MODEL TO DETERMINE BREMSSTRAHLUNG SPECTRA FROM ATTENUATION DATA (RADIATION, X-RAY, SPECTRAL MODELING)

Every x-ray attenuation curve inherently contains all the information necessary to extract the complete energy spectrum of a beam. To date, attempts to obtain accurate spectral information from attenuation data have been inadequate.^ This investigation presents a mathematical pair model, grounded in physical reality by the Laplace Transformation, to describe the attenuation of a photon beam and the corresponding bremsstrahlung spectral distribution. In addition the Laplace model has been mathematically extended to include characteristic radiation in a physically meaningful way. A method to determine the fraction of characteristic radiation in any diagnostic x-ray beam was introduced for use with the extended model.^ This work has examined the reconstructive capability of the Laplace pair model for a photon beam range of from 50 kVp to 25 MV, using both theoretical and experimental methods.^ In the diagnostic region, excellent agreement between a wide variety of experimental spectra and those reconstructed with the Laplace model was obtained when the atomic composition of the attenuators was accurately known. The model successfully reproduced a 2 MV spectrum but demonstrated difficulty in accurately reconstructing orthovoltage and 6 MV spectra. The 25 MV spectrum was successfully reconstructed although poor agreement with the spectrum obtained by Levy was found.^ The analysis of errors, performed with diagnostic energy data, demonstrated the relative insensitivity of the model to typical experimental errors and confirmed that the model can be successfully used to theoretically derive accurate spectral information from experimental attenuation data. ^

Physics potential of a long-baseline neutrino oscillation experiment using a J-PARC neutrino beam and Hyper-Kamiokande

Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of HyperKamiokande is the study of CP asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5 MW × 10⁷ s integrated proton beam power (corresponding to 1.56 × 10²² protons on target with a 30 GeV proton beam) to a 2.5-degree off-axis neutrino beam, it is expected that the leptonic CP phase δCP can be determined to better than 19 degrees for all possible values of δCP , and CP violation can be established with a statistical significance of more than 3 σ (5 σ) for 76% (58%) of the δCP parameter space. Using both νe appearance and νµ disappearance data, the expected 1σ uncertainty of sin²θ₂₃ is 0.015(0.006) for sin²θ₂₃ = 0.5(0.45).

Experimental study on the effective width of flat slab structures under dynamic seismic loading

This paper investigates the effective width of reinforced concrete flat slab structures subjected to seismic loading on the basis of dynamic shaking table tests. The study is focussed on the behavior of corner slab? column connections with structural steel I- or channel-shaped sections (shearheads) as shear punching reinforcement. To this end, a 1/2 scale test model consisting of a flat slab supported on four box-type steel columns was subjected to several seismic simulations of increasing intensity. It is found from the test results that the effective width tends to increase with the intensity of the seismic simulation, and this increase is limited by the degradation of adherence between reinforcing steel and concrete induced by the strain reversals caused by the earthquake. Also, significant differences are found between the effective width obtained from the tests and the values predicted by formula proposed in the literature. These differences are attributed to the stiffening effect provided by the steel profiles that constitute the punching shear reinforcement.

Space Debris Removal with an Ion Beam Shepherd Satellite: target-plasma interaction

A novel concept for active space debris removal known as Ion Beam Shepherd (IBS) which has been recently presented by our group is investigated. The concept makes use of a highly collimated ion beam to exert the necessary force on a generic debris to modify its orbit and/or attitude from a safe distance in a controlled manner, without the need of docking. After describing the main characteristics of the IBS system, some of the key aspects of thruster plasma and its interaction with the debris are studied, namely, (1) the modeling of the expansion of an plasma beam, based on the quasi-selfsimilarity exhibited by hypersonic plumes, (2) the characterization of the force and torque exerted upon the target debris, and (3) a preliminary evaluation of other plasma-body interactions.

Guiding functional connectivity estimation by structural connectivity in MEG: an application to discrimination of mild cognitive impaired conditions

Whole brain resting state connectivity is a promising biomarker that might help to obtain an early diagnosis in many neurological diseases, such as dementia. Inferring resting-state connectivity is often based on correlations, which are sensitive to indirect connections, leading to an inaccurate representation of the real backbone of the network. The precision matrix is a better representation for whole brain connectivity, as it considers only direct connections. The network structure can be estimated using the graphical lasso (GL), which achieves sparsity through l1-regularization on the precision matrix. In this paper, we propose a structural connectivity adaptive version of the GL, where weaker anatomical connections are represented as stronger penalties on the corre- sponding functional connections. We applied beamformer source reconstruction to the resting state MEG record- ings of 81 subjects, where 29 were healthy controls, 22 were single-domain amnestic Mild Cognitive Impaired (MCI), and 30 were multiple-domain amnestic MCI. An atlas-based anatomical parcellation of 66 regions was ob- tained for each subject, and time series were assigned to each of the regions. The fiber densities between the re- gions, obtained with deterministic tractography from diffusion-weighted MRI, were used to define the anatomical connectivity. Precision matrices were obtained with the region specific time series in five different frequency bands. We compared our method with the traditional GL and a functional adaptive version of the GL, in terms of log-likelihood and classification accuracies between the three groups. We conclude that introduc- ing an anatomical prior improves the expressivity of the model and, in most cases, leads to a better classification between groups.

Análisis del comportamiento de uniones metálicas viga-soporte mediante modelo de elementos finitos y comparación de resultados con el modelo de nudos y barras

Para el proyecto y cálculo de estructuras metálicas, fundamentalmente pórticos y celosías de cubierta, la herramienta más comúnmente utilizada son los programas informáticos de nudos y barras. En estos programas se define la geometría y sección de las barras, cuyas características mecánicas son perfectamente conocidas, y sobre las cuales obtenemos unos resultados de cálculo concretos en cuanto a estados tensionales y de deformación. Sin embargo el otro componente del modelo, los nudos, presenta mucha mayor complejidad a la hora de establecer sus propiedades mecánicas, fundamentalmente su rigidez al giro, así como de obtener unos resultados de estados tensionales y de deformación en los mismos. Esta “ignorancia” sobre el comportamiento real de los nudos, se salva generalmente asimilando a los nudos del modelo la condición de rígidos o articulados. Si bien los programas de cálculo ofrecen la posibilidad de introducir nudos con una rigidez intermedia (nudos semirrígidos), la rigidez de cada nudo dependerá de la geometría real de la unión, lo cual, dada la gran variedad de geometrías de uniones que en cualquier proyecto se nos presentan, hace prácticamente inviable introducir los coeficientes correspondientes a cada nudo en los modelos de nudos y barras. Tanto el Eurocódigo como el CTE, establecen que cada unión tendrá asociada una curva momento-rotación característica, que deberá ser determinada por los proyectistas mediante herramientas de cálculo o procedimientos experimentales. No obstante, este es un planteamiento difícil de llevar a cabo para cada proyecto. La consecuencia de esto es, que en la práctica, se realizan extensas comprobaciones y justificaciones de cálculo para las barras de las estructuras, dejando en manos de la práctica común la solución y puesta en obra de las uniones, quedando sin justificar ni comprobar la seguridad y el comportamiento real de estas. Otro aspecto que conlleva la falta de caracterización de las uniones, es que desconocemos como afecta el comportamiento real de éstas en los estados tensionales y de deformación de las barras que acometen a ellas, dudas que con frecuencia nos asaltan, no sólo en la fase de proyecto, sino también a la hora de resolver los problemas de ejecución que inevitablemente se nos presentan en el desarrollo de las obras. El cálculo mediante el método de los elementos finitos, es una herramienta que nos permite introducir la geometría real de perfiles y uniones, y nos permite por tanto abordar el comportamiento real de las uniones, y que está condicionado por su geometría. Por ejemplo, un caso típico es el de la unión de una viga a una placa o a un soporte soldando sólo el alma. Es habitual asimilar esta unión a una articulación. Sin embargo, el modelo por elementos finitos nos ofrece su comportamiento real, que es intermedio entre articulado y empotrado, ya que se transmite un momento y el giro es menor que el del apoyo simple. No obstante, la aplicación del modelo de elementos finitos, introduciendo la geometría de todos los elementos estructurales de un entramado metálico, tampoco resulta en general viable desde un punto de vista práctico, dado que requiere invertir mucho tiempo en comparación con el aumento de precisión que obtenemos respecto a los programas de nudos y barras, mucho más rápidos en la fase de modelización de la estructura. En esta tesis se ha abordado, mediante la modelización por elementos finitos, la resolución de una serie de casos tipo representativos de las uniones más comúnmente ejecutadas en obras de edificación, como son las uniones viga-pilar, estableciendo el comportamiento de estas uniones en función de las variables que comúnmente se presentan, y que son: •Ejecución de uniones viga-pilar soldando solo por el alma (unión por el alma), o bien soldando la viga al pilar por todo su perímetro (unión total). •Disposición o no de rigidizadores en los pilares •Uso de pilares de sección 2UPN en cajón o de tipo HEB, que son los tipos de soporte utilizados en casi el 100% de los casos en edificación. Para establecer la influencia de estas variables en el comportamiento de las uniones, y su repercusión en las vigas, se ha realizado un análisis comparativo entre las variables de resultado de los casos estudiados:•Estados tensionales en vigas y uniones. •Momentos en extremo de vigas •Giros totales y relativos en nudos. •Flechas. Otro de los aspectos que nos permite analizar la casuística planteada, es la valoración, desde un punto de vista de costos de ejecución, de la realización de uniones por todo el perímetro frente a las uniones por el alma, o de la disposición o no de rigidizadores en las uniones por todo el perímetro. Los resultados a este respecto, son estrictamente desde un punto de vista económico, sin perjuicio de que la seguridad o las preferencias de los proyectistas aconsejen una solución determinada. Finalmente, un tercer aspecto que nos ha permitido abordar el estudio planteado, es la comparación de resultados que se obtienen por el método de los elementos finitos, más próximos a la realidad, ya que se tiene en cuenta los giros relativos en las uniones, frente a los resultados obtenidos con programas de nudos y barras. De esta forma, podemos seguir usando el modelo de nudos y barras, más versátil y rápido, pero conociendo cuáles son sus limitaciones, y en qué aspectos y en qué medida, debemos ponderar sus resultados. En el último apartado de la tesis se apuntan una serie de temas sobre los que sería interesante profundizar en posteriores estudios, mediante modelos de elementos finitos, con el objeto de conocer mejor el comportamiento de las uniones estructurales metálicas, en aspectos que no se pueden abordar con los programas de nudos y barras. For the project and calculation of steel structures, mainly building frames and cover lattices, the tool more commonly used are the node and bars model computer programs. In these programs we define the geometry and section of the bars, whose mechanical characteristics are perfectly known, and from which we obtain the all calculation results of stresses and displacements. Nevertheless, the other component of the model, the nodes, are much more difficulty for establishing their mechanical properties, mainly the rotation fixity coefficients, as well as the stresses and displacements. This "ignorance" about the real performance of the nodes, is commonly saved by assimilating to them the condition of fixed or articulated. Though the calculation programs offer the possibility to introducing nodes with an intermediate fixity (half-fixed nodes), the fixity of every node will depend on the real connection’s geometry, which, given the great variety of connections geometries that in a project exist, makes practically unviable to introduce the coefficients corresponding to every node in the models of nodes and bars. Both Eurocode and the CTE, establish that every connection will have a typical moment-rotation associated curve, which will have to be determined for the designers by calculation tools or experimental procedures. Nevertheless, this one is an exposition difficult to carry out for each project. The consequence of this, is that in the practice, in projects are extensive checking and calculation reports about the bars of the structures, trusting in hands of the common practice the solution and execution of the connections, resulting without justification and verification their safety and their real behaviour. Another aspect that carries the lack of the connections characterization, is that we don´t know how affects the connections real behaviour in the stresses and displacements of the bars that attack them, doubts that often assault us, not only in the project phase, but also at the moment of solving the execution problems that inevitably happen in the development of the construction works. The calculation by finite element model is a tool that allows us to introduce the real profiles and connections geometry, and allows us to know about the real behaviour of the connections, which is determined by their geometry. Typical example is a beam-plate or beam-support connection welding only by the web. It is usual to assimilate this connection to an articulation or simple support. Nevertheless, the finite element model determines its real performance, which is between articulated and fixed, since a moment is transmitted and the relative rotation is less than the articulation’s rotation. Nevertheless, the application of the finite element model, introducing the geometry of all the structural elements of a metallic structure, does not also turn out to be viable from a practical point of view, provided that it needs to invest a lot of time in comparison with the precision increase that we obtain opposite the node and bars programs, which are much more faster in the structure modelling phase. In this thesis it has been approached, by finite element modelling, the resolution of a representative type cases of the connections commonly used in works of building, since are the beam-support connections, establishing the performance of these connections depending on the variables that commonly are present, which are: •Execution of beam-support connections welding only the web, or welding the beam to the support for the whole perimeter. •Disposition of stiffeners in the supports •Use 2UPN in box section or HEB section, which are the support types used in almost 100% building cases. To establish the influence of these variables in the connections performance, and the repercussion in the beams, a comparative analyse has been made with the resulting variables of the studied cases: •Stresses states in beams and connections. •Bending moments in beam ends. •Total and relative rotations in nodes. •Deflections in beams. Another aspect that the study allows us to analyze, is the valuation, from a costs point of view, of the execution of connections for the whole perimeter opposite to the web connections, or the execution of stiffeners. The results of this analyse, are strictly from an economic point of view, without prejudice that the safety or the preferences of the designers advise a certain solution. Finally, the third aspect that the study has allowed us to approach, is the comparison of the results that are obtained by the finite element model, nearer to the real behaviour, since the relative rotations in the connections are known, opposite to the results obtained with nodes and bars programs. So that, we can use the nodes and bars models, more versatile and quick, but knowing which are its limitations, and in which aspects and measures, we must weight the results. In the last part of the tesis, are relationated some of the topics on which it would be interesting to approach in later studies, with finite elements models, in order to know better the behaviour of the structural steel connections, in aspects that cannot be approached by the nodes and bars programs.

Structural behaviour of glass reinforced plastics

The aim of this research is to promote the use of G.R.P. as a structural material. In the past, the use of G.R.P. has been confined to non-load carrying applications. Such uses are still rapidly increasing but in addition significant changes have been made during the last decade in the development of semi-structural and now even fully structural applications. Glass-reinforced plastic is characterized by a high strength but a relatively low modulus of elasticity. For this reasona G.R.P. structure can expect to show large deformations as a result of which the individual structural members will fail under load due to a loss of stability rather than approaching the ultimate strength of the material. For this reason the selection of the geometrical shapes of G.R.P. structural elements is considered to be an important factor in designing G.R.P. structures. The first chapter of this thesis deals with a general review of the theoretical and experimental methods used to describe the structural properties of G.R.P. The research programme includes five stages dealing with the structural behaviour of G.R.P. The first stage (Chapter 2) begins with selecting and designing an optimum box beam cross-section which gives the maximum flexural and torsional rigidity. The second stage of investigation (Chapter 3) deals with beam to beam connections. A joint was designed and manufactured with different types of fasteners used to connect two beam units. A suitable fastener was selected and the research extended to cover the behaviour of long span beams using multiple joints. The third part of the investigation includes a study of the behaviour of box beams subjected to combined bending, shear and torsion. A special torque rig was developed to perform the tests. Creep deformation of 6 m span G.R.P. was investigated as the fourth stage under a range of loading conditions. As a result of the phenomenon of post buckling behaviour exhibited in the compression flange during testing of box beams during earlier stages of the investigation it was decided to consider this phenomenon in more detail in the final stage of the investigation. G.R.P. plates with different fibre orientation were subjected to uniaxial compression and tested up to failure. In all stages of the investigation theoretical predictions and experimental results were compared and generally good correlation between theory and experimental data was observed.