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This paper presents an experimental investigation about the effect of elevated temperature on the mechanical properties of two polyurethane (PUR) foams, with densities of 40 kg/m3 and 93 kg/m3. The experimental campaign included shear and compressive tests over a temperature range of 20°C–200°C, performed to assess the degradation of the mechanical properties of the PUR foams with temperature. To validate the diagonal tension shear test method adopted in this investigation, a numerical study was also performed, namely to assess the (shear) stress state developed within the foam. The results obtained validated the adopted test procedures, showing that the compressive and shear responses are strongly affected by elevated temperature, due to the softening of the polymeric material when it undergoes the glass transition process. For the temperature range considered in this study, both strength and modulus in shear and compression present an approximately linear reduction with temperature.

A 61-year-old man was diagnosed with an exudative pleural effusion with raised amylase and bilirubin levels. The patient had no previous history of acute pancreatitis or trauma and no clinical or radiological signs of chronic pancreatitis. On thoracoabdominal computed tomography, a pancreatic pseudocyst with a pancreaticopleural fistula was identified. Endoscopic retrograde cholangiopancreatography identified a ductal disruption site in the body of the pancreas. Pancreatic sphincterotomy and stent placement in the duct of Wirsung, combined with medical management, allowed fistula closure, pseudocyst reabsorption, and no relapse of the pleural effusion. The relevance of this case lies not only in its rarity but also as it highlights the importance of a multidisciplinary approach in such uncommon conditions. Optimal management of this condition is debatable due to the absence of prospective studies comparing medical, endoscopic, and surgical approaches.

A sandwich wall-panel solution based on Cross-Laminated Timber (CLT) has been recently developed aiming to rationalize the wood volume and combine it with a low-density core layer for improved thermal insulation and reduced weight. Such panel, named Cross-Insulated Timber (CIT), was previously optimized to fulfil structural and thermal requirements with a minimum production cost. The layout of the new panel is similar to the one of a five-layer CLT panel, but the inner layer is made of polyurethane rigid foam instead of timber. Besides its technical and economical benefit, it is also of interest to assess its environmental impact. This paper presents a study about the environmental impact assessment through Life-Cycle Analysis (LCA) of this new type of wood-based sandwich wall panel. A cradle-to-gate LCA with consideration of different end-of-life scenarios is performed in order to identify the processes that contribute the most to the environmental impact of the CIT panel solution proposed during its life cycle, namely during manufacturing. The LCA includes also the comparative assessment of: (i) varying the thickness of the wood layers, with respect to the optimized CIT panel; (ii) using an alternative core material, namely insulation cork board (ICB), and (iii) applying structurally equivalent three-layered CLT solutions, with alternative core materials. The results obtained show that the manufacturing process of the CIT panel, namely the polyurethane foam production and the press and curing processes during the panels assembly are the ones that produce the highest impacts. It was also found out that varying the thickness of the wood layers compared to the optimized solution leads, in general, to an increase in all impact categories. This means that the optimized solution in terms of economic costs is also the one which presents the lowest environmental impacts. Compared to equivalent CIT panels with ICB core and CLT solutions, the environmental performance of the panel proposed was better for some impact categories, while it was worse in others.

The aim of this study is to quantify and compare the environmental impact from cradle-to-gate of different systems for building floor rehabilitation. The Life Cycle Assessment (LCA) method was used for the evaluation of the potential environmental impact of the production of each floor system in eight categories and a monetisation method was used for the weighting of the results and for their expression into one single indicator. Five functionally equivalent (from a structural standpoint) systems were assessed, including: (i) traditional solutions, such as timber floors and reinforced concrete (RC) slabs; (ii) less conventional solutions, such as beam-and-block and steel–concrete composite slab systems; and (iii) an innovative glass fibre reinforced polymer (GFRP) sandwich panel system. The environmental impacts of these systems are compared in this paper for the first time. It was found out that timber is the most environmentally friendly solution, since it presents the lowest total values in all environmental impact categories (under 1% of the impact of the solution with highest impact in each category, RC or GFRP), except for primary renewable energy consumption, for which the RC solution presents the least consumption. On the other hand, it was found out that: the steel–concrete composite floor is the least environmentally friendly solution in abiotic resource depletion; the RC solution is the least performing option in terms of global warming potential and ozone depletion potential; and the GFRP system presents the worst behaviour in five environmental impact categories – non-renewable energy consumption, photochemical ozone formation potential, acidification potential, eutrophication potential and Eco-costs. However, if the most important inefficiencies identified during the production of the latter floor system are at least partly amended, its impacts would be substantially reduced, particularly regarding the Eco-costs indicator, which considers four environmental categories at once – in that case, the RC solution would become the worst solution and GFRP sandwich panels would have an aggregated result of 80% of the RC. The final part of the paper presents a qualitative assessment of the gate-to-grave performance of the different solutions.

Balsa wood is increasingly considered as a core material in sandwich panels for applications in several industries. However, there is still very limited information about its mechanical behaviour at elevated temperature. This article presents an experimental and analytical study about the effects of elevated temperature on the shear behaviour of end-grain balsa with nominal density of 109 kg/m3. The Iosipescu/V-notch test method was used to investigate the shear behaviour of balsa specimens extracted along the two material directions that are relevant for core materials subjected to shear: (i) transverse to the wood grain and (ii) parallel to the wood grain. The shear tests were conducted under steady-state conditions for temperatures between room temperature and 240°C. For the various temperatures, the stress vs. strain behaviour in shear was non-linear, with such non-linearity becoming more accentuated at higher temperatures. The shear modulus and strength presented a linear and comparable reduction with increasing temperature, and the residual properties at 240°C dropped to less than 20% of the room temperature properties. In the final part of the article, four alternative analytical models available in the literature were assessed regarding their ability to describe the reduction with temperature of the shear properties of balsa. All models were able to successfully fit the test data.

The ability to numerically predict the ultimate strength of fibre reinforced polymer (FRP) structures is fundamental in order to enable design methodologies not resorting exclusively to experimental tests. In the last few decades, several authors have proposed failure initiation criteria for FRP materials. However, most of the proposed models are either limited in their application range (e.g. valid for unidirectional composites) or require layer-by-layer input data from experimental results that are very difficult to obtain (e.g. strength under biaxial loading). On the other hand, strength predictions based on first ply failure are overly conservative, especially for complex structures where local damage can occur without causing the overall structural collapse. Thereafter, in order to estimate the strength of FRP structures, damage progression models have been associated to failure initiation models. Some authors have adapted damage progression models developed for concrete materials, based on fracture energy. However, owing to the anisotropy and brittle nature of FRP materials, these models require extensive input data from various experimental tests, the values of which may vary widely for different FRP materials. Moreover, finite elements (FE) modelling of damage progression of FRP elements often involves layering the laminates and high computational costs. These limitations lead to the necessity of developing damage progression models able to capture the complex failure behaviour of FRPs while modeling the material as homogenous in order to reduce computational costs. In this paper, a new progressive failure model is proposed for the mesoscale modelling of homogenized FRP composites, considering failure initiation and damage evolution. The quadratic failure initiation model proposed uses two failure indexes, one for in-plane and the other for out-of-plane failure. The damage evolution model can be divided in two stages: (i) gradual stiffness loss, and (ii) final failure. In the first stage, the Matzenmiller-Lubliner-Taylor (MLT) exponential damage model is used, attributing different parameters for each elastic and shear moduli. In the second stage, a residual strength is attributed to each direction beyond a limit strain. The progressive failure model was implemented in the FE commercial package ABAQUS through a user material subroutine (UMAT). The results show that the proposed model is able to accurately predict the strength and failure modes of pultruded FRP structures under different loadings, by modeling the laminates as homogeneous orthotropic materials.

Research concerning the long-term behaviour of fibre reinforced polymer (FRP) composites in civil engineering applications is increasing, as key actors in this industry recognize the existence of many knowledge “gaps” that still need to be fulfilled. Several competing mechanisms may affect the durability of FRPs during exposure to hygrothermal ageing conditions, and in the specific case of pultruded glass-fibre reinforced polymer (GFRP) profiles, comprehensive and validated data on their durability is still limited. The typically long service lives required for most structures together with the low frequency of routine inspection and maintenance operations in civil infrastructure enhance the importance of having reliable durability data and suitable prediction models for the long-term performance of these materials. This study presents results of an experimental and analytical study designed to investigate the effects of hygrothermal ageing on the durability and long-term performance of two commercial GFRP profiles made of two alternative resin systems – unsaturated polyester (UP) and vinylester (VE), both comprising the same fibre content and architecture. Test specimens of the two types of profiles were subjected to different ageing environments, namely immersion in demineralised and salt water at three different temperatures (20 ℃, 40 ℃, and 60 ℃) and continuous condensation at 40 ℃ for up to two years, and were tested after a desorption period, thus including the potential property recovery after drying to constant mass due to the reversible nature of some of the physical degradation mechanisms. The performance of both profiles was analysed and compared regarding their mechanical response in tension and flexure after being subjected to hygrothermal ageing. The experimental data thus gathered were subsequently used to derive analytical models for the prediction of long-term effects and service life of pultruded GFRP profiles based on the Arrhenius law. This provided estimates for the retention of strength and moduli in tension and flexure, for both UP and VE pultruded GFRP profiles when exposed to different hygrothermal environments.

Part 1 [1] of this two-part paper presented an experimental study of the cyclic behaviour of a novel beam-to-column sleeve connection system for pultruded glass fibre reinforced polymer (GFRP) tubular profiles, and the numerical simulation of such behaviour. This Part 2 presents an experimental and numerical study on the sway behaviour of full-scale GFRP plane frames comprising the same tubular profiles and the aforementioned connection system. The GFRP frames were tested under quasi-static monotonic and cyclic loading, with and without infill walls, materialized by composite sandwich panels. The results of the tests show that high-load carrying capacity infill walls have a remarkable effect on the frames’ structural behaviour, significantly increasing their stiffness and load carrying capacity, as well as their cyclic performance, namely regarding energy dissipation. On the other hand, such improvement involved extensive damage in the frame elements, particularly in the beams, which at some point compromised their structural integrity. The numerical study included the simulation of the cyclic tests of the unfilled walls, by means of relatively simple finite element (FE) models, comprising frame elements and spring joints simulating the behaviour of the connections, in which the Pivot hysteresis model calibrated in Part 1 [1] was used. The comparison between experimental and numerical results shows that these simple and design-oriented FE models can provide an effective (and conservative) tool for the simulation of pultruded GFRP frames under horizontal cyclic loads.

Pultruded glass fibre reinforced polymer (GFRP) profiles have low weight, high strength and corrosion resistance, but their brittle failure raises concerns about their use in seismic regions. Moreover, although their static monotonic response is reasonably well understood, the cyclic and hysteretic behaviour of GFRP frame structures and their beam-to-column connections have not yet been comprehensively investigated. This paper presents experimental and numerical investigations on the cyclic behaviour of a novel tubular GFRP beam-to-column sleeve connection system, comprising internal metallic parts. Four series of the connection system were tested, with varying number and position of the beam connection bolts, namely with: (i) one bolt in the webs (W1); (ii) two bolts in the flanges (F2); (iii) four bolts in the flanges (F4); and (iv) two bolts in the flanges with larger edge distance (F2S). The results show that series W1 presents the worst overall cyclic behaviour. On the other hand, the addition of bolt rows (F4 vs. F2) did not improve the cyclic response of the connection system. Conversely, increasing the edge distance (F2S vs. F2) led to significant improvements of the hysteretic behaviour, namely in the capacity to dissipate energy. Using the Pivot hysteresis model in the numerical study, a design-oriented model comprising frame and link elements was developed to simulate the response of the best performing series (F2S). In spite of its simplicity, the numerical simulation provided good agreement with the experimental results. In a companion paper, the behaviour of full-scale frames comprising F2S connections under monotonic and cyclic quasi-static sway tests was experimentally assessed. Numerical models of these tests were also developed to simulate the cyclic behaviour of the frames, using the parameters of the Pivot hysteresis model calibrated herein.

This paper presents an experimental study about the bonding quality of Maritime pine (Pinus pinaster Ait.) cross-layered wood elements glued with one-component polyurethane adhesive. The experiments comprised shear and delamination tests according to standard EN 16351 focusing on the influence of the following parameters: bonding pressure, adhesive spread rate, pre-treatment with primer and layer thickness. The results obtained show that increasing bonding pressure increases significantly the wood failure percentage after delamination or shear tests, while the delamination and the shear strength are not significantly affected. Moreover, it was found that the use of primer enhances significantly the bonding quality; nevertheless, EN 16351 requirements are fulfilled even for the lower bonding pressure and adhesive spread rate recommended by the manufacturer of the adhesive used in the experiments. The layer thickness, for the tested range, had no influence on the delamination and shear results and limited one on the wood failure percentage after shear or delamination tests. No relevant influence was found for the adhesive spread rate. In the experiments the combination of gluing Maritime pine with Australian blackwood (Acacia melanoxylon R.Br.) was also investigated and, for this combination, the standard requirements were successfully fulfilled.

The use of glass fibre reinforced polymer (GFRP) bars as internal reinforcement of concrete structures has been growing, mainly due to the advantages they present over steel reinforcement, namely their low weight, high strength and corrosion resistance. However, at moderately elevated temperatures, especially when approaching the glass transition temperature (Tg) of the polymeric matrix (usually between 65 and 150 °C), the stiffness, strength and bond properties of these rebars are known to be significantly degraded. The first part of this paper presents an experimental investigation comprising tensile and pull-out tests on sand coated GFRP rebars at elevated temperatures under steady-state conditions; the tensile tests were carried out up to 300 °C, whereas the pull-out tests were performed up to 140 °C (measured at the GFRP-concrete interface); two embedment lengths of the rebars were considered. The obtained results confirmed that the stiffness and strength of the GFRP-concrete interface are significantly reduced with temperature increase, especially when the Tg of the GFRP rebars is approached and exceeded. In the second part of the paper, analytical bond vs. slip relations for the GFRP-concrete interface are proposed for each of the tested temperatures; the defining parameters of these local laws were calibrated with the experimental data from the pull-out tests. Moreover, the accuracy of two empirical (relaxation) models in predicting the GFRP-concrete bond strength reduction with temperature was also assessed.

This paper presents the manufacturing and the mechanical and thermomechanical properties of a bio-based glass fibre-reinforced polymer (GFRP) composite, produced by vacuum infusion, using an in-house high-performance bio-based unsaturated polyester resin (UPR) with more than 50 wt% of its content derived from renewable raw materials. Specimens were successfully produced, and their mechanical and thermomechanical properties was compared to an equivalent GFRP composite produced with conventional petroleum-based UPR and the same fibre architecture. The bio-based GFRP composite presented 538 MPa, 210 MPa, and 52 MPa of tensile, compressive, and shear strengths; 20 GPa, 24 GPa, and 2.5 GPa of tensile, compressive, and shear moduli; and 3.0%, 0.8%, and 14.8% of tensile, compressive, and shear strain at failure, meeting or exceeding the mechanical properties of the conventional counterpart. Furthermore, the bio-based GFRP composite presented a T-g of 64 degrees C (defined from onset of the storage modulus decay), enabling its outdoors use.

This paper proposes, for the first time, a design methodology against the web-crippling failure of pultruded glass fiber–reinforced polymer (GFRP) I-section beams, based on the direct stre...

This paper summarizes the work of CAMEPP, the IST Commission that was charged in 2018 with the analysis of pedagogical practice at IST, as well as of the curricula of its first and second cycle degrees. As a consequence of this work, IST changed significantly the curricular structure of its degrees and pedagogical methods, with a new design that will begin its implementation in 2021/22.

The authors report an unusual case of gastrointestinal bleeding with a challenging diagnosis, associated with a Bochdalek hernia. This clinical case highlights the role of capsule endoscopy both as a first-line exam in obscure gastrointestinal bleeding and as an alternative exam in cases of incomplete colonoscopy. .

Fiber-reinforced polymer (FRP) composites are being increasingly used in the construction sector, especially in corrosion-prone applications. However, there is still a lack of knowledge abo...

This paper presents an experimental study about the transverse tensile fracture properties of several off-the-shelf pultruded glass fiber-reinforced polymer (GFRP) materials, with differen...

Sandwich structures comprising glass-fibre reinforced polymer faces and low-density core constitute an efficient and versatile constructive system for civil and ocean engineering structures. However, being multilayered with relatively soft core materials, they are particularly susceptible to damage under concentrated loads. Whilst numerous studies exist on the indentation and impact behaviour of sandwich composites, the great majority considers the thin-skinned laminates used by the aeronautical industry. To mitigate the lack of studies on the significantly thicker and more robust civil and ocean engineering sandwich laminates, the quasi-static indentation and low-velocity impact behaviour of such panels is experimentally studied. Three types of core materials (polyurethane and polyethylene terephthalate foams and end-grain balsa) and five different indenters, of varying shape (hemispherical versus flat) and diameter (10, 20 and 30 mm), are considered. Flat and larger indenters required higher loads and energies for first damage and perforation. The first damage and peak resistance values of the polyethylene terephthalate panels were, respectively, 15 and 8% higher than in the polyurethane panels; for the balsa panels, such figures were 20 and 10%. The polyurethane panels showed the highest energy absorption capacity. Predictions of first damage resistance given by two analytical models (for flat and hemispherical indenters) were assessed against the gathered experimental data. The obtained predictions were reasonably accurate, but indicate a need for further calibration, mainly concerning the effects of core material.

This paper presents a numerical investigation on the fire resistance of pultruded GFRP columns with tubular cross-section, both unprotected and protected with a passive fire protection. Three-dimensional finite element models were developed and they considered the thermo-mechanical behaviour of GFRP material (temperature-dependent mechanical properties) and the temperature distributions previously obtained through heat transfer analyses and fluid dynamics inside the tube cavity. The numerical results presented include the time evolution of axial and flexural deformations of the GFRP columns, as well as the stress distributions in both longitudinal and transversal directions of the unprotected column under one-side fire exposure and axially compressed (designated as reference column). In comparison with this reference column, the paper focuses on the evaluation of the several effects, such as the use of fire protection system, the imposition of different fire exposure conditions and the application of distinct load levels. The Tsai-Hill criterion is used to identify the initial failure of GFRP columns and assess the evolution of failure index with fire exposure time, while the Hashin criterion is used to obtain an estimate of column strength and collapse mode. It is concluded that the proposed models are able to qualitatively capture the general trend of the experimental results, despite the quantitative differences not yet overcome. With the consideration of creep, delamination effects and fracture, the authors are confident that these models will soon correctly predict the complex mechanical behaviour and the fire resistance of GFRP columns.

This paper presents experimental and numerical investigations about the effects of thermal cycles on adhesively bonded joints between pultruded glass fibre reinforced polymer – unsaturated polyester (GFRP) adherends used in civil engineering structural applications. Single lap bonded joints were produced with two commercial polymeric adhesives – epoxy (EP) and polyurethane (PUR) – and exposed to a mild (Mediterranean) range of thermal variations (−5 °C–40 °C) for up to 350 cycles in a dry condition. The mechanical performance of the adhesively bonded joints was assessed by means of single lap shear tests . Regardless of the inherent differences between both adhesives, results obtained show that the global effect of thermal cycles on the load vs. displacement response of EP-GFRP and PUR-GFRP joints was similar. For both adhesives, thermal cycles caused considerable reduction of joint stiffness and strength, with maximum reductions of 18% and 22% for EP-GFRP joints, respectively, and 19% and 11% for PUR-GFRP joints. The degradation of performance was influenced by post-curing effects, more relevant in the PUR adhesive. Before exposure to thermal cycles, both types of specimens exhibited similar failure mechanisms, which generally (80–90% of cases) involved light fibre tear and fibre tear modes, attesting the effectiveness of the adhesion process and material compatibility. Exposure to thermal cycles did not influence the failure modes of the PUR-GFRP joints; however, EP-GFRP joints became more prone to adhesive failure after being subjected to thermal cycles. Three-dimensional finite element models were used to estimate the magnitude of the internal stresses developed during the thermal cycles. For both types of bonded joints, the numerical results showed a relatively low magnitude of both shear and normal stresses developed due to the mismatch of the coefficients of thermal expansion (CTE) of the adherends and the adhesives. Overall, the results obtained indicate that thermal cycles degrade bonded joints between pultruded GFRP adherends and this degradation seems to be due mostly to detrimental effects on the constituent materials, namely the adhesives; however, for the conditions used in this study, this degradation seems to be compatible with the structural use of this type of joints in civil infrastructure.

This paper presents an experimental study about the effects of hygrothermal and outdoor ageing on a polyurethane (PUR) adhesive used in civil engineering applications. Small-scale adhesive coupons were exposed to different types of ageing environments for up to two years: (i) immersion in demineralised water at 20 and 40 °C, (ii) immersion in salt water at 20 and 40 °C, (iii) continuous condensation environment at 40 °C, and (iv) outdoor ageing in Lisbon, Portugal. At predetermined times, after a desorption period until constant mass, the effects of such exposure on the physical and mechanical responses of the PUR adhesive was investigated using the following techniques: (i) water sorption, (ii) dynamic mechanical analyses (DMA); (iii) flexural; and (iv) in-plane shear tests. The diffusion mechanisms observed were not purely Fickian; a long relaxation period was noticed, with water molecules being continuously incorporated in the adhesive until the end of the experiments; two alternative analytical modelling approaches were successfully used to simulate the diffusion processes. After immersion in water and salt water for two years, the viscoelastic behaviour of the adhesive showed signs of post-curing phenomena, and some of the physical degradation was found to be reversible due to drying, although it was not explicitly quantified; accordingly, the Tg showed increasing trends (11-14%). The mechanical properties of the adhesive showed signs of irreversible degradation mechanisms, more relevant on the in-plane shear properties, with reductions up to 26% in strength and 44% in modulus under the harsher conditions. Flexural properties also exhibited irreversible degradation, with maximum reductions up to 30% in strength and 36% in modulus. Increased temperature did not have a significant effect in the flexural and shear strength, but caused higher degradation in the corresponding moduli. The degradation caused by salt water immersion and continuous condensation was comparable to that in demineralized water immersion (at the same temperature).

In order to overcome the main mechanical drawbacks of GFRP profiles, namely their high deformability and proneness to instability phenomena, several GFRP-concrete hybrid solutions comprising bonded connections with epoxy adhesive have been proposed. Although being able to provide almost full interaction at the GFRP-concrete interface(s) (at least in the short-term), there is very little information about the durability of such connection systems, which raises concerns about the long-term performance of hybrid structural solutions. This paper presents experimental and numerical investigations on the durability of adhesively bonded connections between pultruded GFRP profiles and steel fibre reinforced self-compacting concrete (SFRSCC). GFRP-SFRSCC specimens were first subjected to accelerated ageing, involving thermal and wet-dry cycles, and then subjected to push-out tests. The accelerated ageing did not have significant influence on the strength of the GFRP-SFRSCC connection; however, it had a very deleterious effect on its stiffness. The numerical study included the development of finite element models of the specimens tested. Using bi-linear bond-slip laws, it was possible to simulate the test results with good accuracy. In the final part of the paper, the influence of the interface stiffness reduction on the deformability of a real hybrid structure (the Sao Silvestre footbridge) is analysed. Although the stiffness of the GFRP-SFRSCC interface is considerably reduced by the ageing processes, this results in a very small increase of the overall mid-span deflections of the footbridge.

This paper presents and discusses the numerical performance of a set of physically non-linear models applied together with Carrera’s Unified Formulation (CUF) for the analysis of beams. The main objective of this work is to assess the numerical efficiency of CUF when non-linear material analysis is applied to 1D elements using the equivalent single layer (ESL) formulation. To model material behaviour this work considers three different alternative approaches: (i) the classical isotropic plasticity with no hardening, (ii) the Mazars isotropic concrete damage model, and (iii) the composite orthotropic Hashin damage model. To validate the models proposed, the numerical solutions are compared both with analytical results and experimental data. The results obtained show that it is possible to provide accurate results with CUF when physically non-linear analysis is performed, even when considering approximations involving a small number of degrees of freedom.

Fibre Reinforced Polymer (FRP) composites have been the source of an increasing interest in the field of rehabilitation, namely for repair and strengthening of reinforced concrete (RC) structures. One of the most effective techniques comprises externally bonded FRP composites, in which the efficacy of rehabilitation depends considerably on the integrity and durability of the bond established between the FRP and the substrate, which is provided by a structural adhesive. This paper presents a concise review of critical durability issues associated with the structural bond between FRP and concrete for rehabilitation purposes. A number of factors determining the durability of FRP-concrete bonded joints have been identified and grouped into the following categories: materials – adhesive and adherends, joint characteristics and in-service conditions. For each of those factors, the main findings obtained in previous studies are summarized and the aspects that need further investigation are outlined.

This paper presents a numerical study about the thermal behaviour of pultruded GFRP profiles with square tubular cross-section exposed to fire. Two-dimensional and three-dimensional numerical models of previous fire tests of GFRP profiles were developed using the commercial software ANSYS Fluent 14.5. The efficacy of using different fire protection systems (passive and active) and the influence of the number of sides exposed to fire (one or three) in the thermal response of the GFRP profiles was studied. The models developed consider the heat exchanges by means of conduction, internal radiation and convection of the air and/or water enclosed in the cavity of the GFRP tubular profiles. A general good agreement was obtained between numerical temperatures and test data. The results obtained highlight (i) the relative efficiency of the different fire protection systems and (ii) the remarkable influence of exposing GFRP profiles to fire in three sides, and (iii) show the importance of the heat exchanges due to internal radiation and convection inside the cavity of the GFRP cross-section in this type of thermal simulations. The thermal models were further validated through the simulation of previous fire resistance experiments on multicellular slab panels.

This two-part paper presents a numerical study about the fire resistance behaviour of pultruded GFRP profiles with square tubular cross-section subjected to bending and the ISO 834 time-temperature curve. The first paper deals with the development of numerical and analytical models and the discussion of relevant kinematic issues, including the evolution of beam deflection and position of neutral axis with the fire exposure time. The second part [1] reports an in-depth investigation on the side of static issues, which include the evolution of stress distributions and failure initiation with the fire exposure time. In the present paper, three–dimensional finite element models were developed to simulate fire resistance tests previously conducted by the authors on GFRP beams, in which different degradation curves were considered for compressive, tensile and shear moduli , based on experimental data. In these numerical simulations, both effects of varying the assignment of material properties (depending on the position of neutral axis) and of considering different thermal expansion coefficients were taken into account, and some conclusions were drawn on their influence on mid-span deflection evolutions. Since no failure criterion was implemented, both models were not able to reproduce the failure of the beams, but the overall tendency of the numerical results was consistent with the experimental data. Alongside the numerical study, analytical models based on Timoshenko beam theory were also developed and allowed obtaining accurate predictions of the mid-span deflection evolution of the GFRP beams; the analytical results were in close agreement with the numerical ones and also with the experimental data.

This two-part paper presents a numerical study on the fire resistance behaviour of pultruded GFRP profiles with square tubular cross-section simultaneously subjected to four-point bending and the standard fire of ISO 834. The first part [1] presented the numerical models and results focused on the most relevant kinematic issues (deflections and strains), while this second part (present paper) reports numerical results associated to the static issues, particularly the evolution of stress distributions and failure initiation with fire exposure time. The paper first presents and discusses the evolution of stress distributions in both longitudinal and transversal directions of an unprotected GFRP beam under one-side fire exposure (reference beam). Next, the influence of using a fire protection system and exposing the beams to fire in three sides is assessed by comparison with the case of reference beam. Additionally, the Tsai-Hill failure (initiation) criterion was used to identify the zones (sections and points) of GFRP beams that are most sensitive to failure due to high temperatures. The numerical results obtained show that (i) longitudinal stresses across the section become highly nonlinear as a result of temperature increase; (ii) shear stress diagram is severely affected by fire exposure in three sides; (iii) transversal stresses are negligible compared to the longitudinal and shear ones; and (iv) the collapse of beams (considering Tsai-Hill failure analysis) occurs due to top flange and web (top part) failure, which generally agrees with experimental observations.

This paper presents some numerical investigations related to the use of a new approximation function to be applied in Carrera's Unified Formulation (CUF). The main objective is to study and assess the efficiency of the CUF, when Legendre approximation functions are used at the section level, on 1D element, using an equivalent single layer (ESL) formulation. Previous experimental and analytical results, obtained in the case of GFRP composite bridge decks and sandwich panels, are used to further validate the numerical results being reported. 3D finite elements are also used, in order to compare and validate the numerical structural outputs. The main conclusion is that the classical Legendre polynomial functions are suitable and provide accurate results. The use of this type of functions does not require any stabilization procedure of the resulting governing system for the case of 1D elements, in clear contrast to what typically happens when other approximation functions are used with an equivalent single layer formulation.

This paper presents a numerical study on the web-crippling failure of pultruded glass fibre reinforced polymer (GFRP) profiles, under external-two-flange (ETF) and internal-two-flange (ITF) configurations. The numerical study is validated through experimental tests recently conducted by the authors on four I-section profiles and one U-section profile, obtained from four different suppliers. These web-crippling tests were simulated through shell finite element (FE) models where the transverse compressive fracture toughness of each GFRP material was implemented as a damage evolution parameter. In order to quantify the influence of material damage and instability effects on the web-crippling failure, three different analyses were implemented, accounting for (i) material damage, (ii) instability, and (iii) both effects. The results obtained through the analysis accounting for both material damage and instability effects showed a good agreement with experimental results, in terms of stiffness, failure modes and ultimate loads; moreover, the transverse compressive strain distributions obtained from the numerical models also agreed well with experimental results. Finally, the transverse compressive stresses were found to influence web-crippling the most, regarding both damage initiation and ultimate load stages.

This paper presents an experimental study about the fire behaviour of reinforced concrete (RC) slabs strengthened with carbon fibre reinforced polymer (CFRP) strips, applied according to three different techniques: externally bonded reinforcement (EBR); near-surface mounted (NSM), and continuous reinforcement embedded at the ends (CREatE), a new technique that prevents premature CFRP debonding. The main goals of this study were three-fold: to understand and compare the fire behaviour of the strengthening techniques, namely the CREatE technique (yet to be studied); to assess the efficiency of the fire protection schemes (constant thickness vs. increased thickness at the CFRP anchorage zones) in extending the fire resistance of the CFRP systems; and, based on the experimental results and data available in the literature, to propose “critical” temperatures for the fire design of CFRP-strengthened RC members. The results obtained show that: (i) without protection, the CREatE technique presented higher fire resistance than the alternative NSM and EBR techniques (24 min vs. 16 min and 2 min); (ii) with fire protection, regardless of its geometry, the NSM and CREatE techniques presented a similar fire resistance (both above 120 min), higher than the EBR technique (less than 60 min); and (iii) the “critical” temperatures for each technique were defined as 1.0Tg, 2.5Tg and 3.0Tg for EBR, NSM and CREatE, respectively, with Tg being the glass transition temperature of the adhesive, defined based on the onset of the storage modulus curve decay from dynamic mechanical analysis.

This paper presents an experimental study about the monotonic and cyclic behaviour of beam-to-column connections between pultruded GFRP profiles with I-section, joined by means of stainless steel cuff connection parts. This study pursues a previous investigation by the authors in which custom stainless steel cuff parts were proposed for beam-to-column connections between pultruded tubular GFRP profiles, which presented very satisfactory performance under both monotonic and cyclic loading. A similar concept is now investigated for joining profiles with I-section shapes, which are more often used in civil engineering applications. Four series of full-scale beam-to-column connections were tested under monotonic loading, using stainless steel cuffs of two different plate thicknesses and lengths. The results show that higher cuff thickness and length provided higher initial stiffness and strength, with the cuff thickness being the most influential parameter. Conversely, the ductility of the connections decreased with increasing cuff thickness: the series with thinnest cuff parts presented the highest ductility. The series with the most ductile cuff part was also tested under cyclic loading and presented significant capacity to dissipate energy, but showed marked pinching. These results were compared to those of a stainless steel flange cleated connection system previously tested using the same GFRP I-section profiles: the connections using cuff parts presented worst mechanical behaviour than the cleated connections. This indicates that the cuff connection system is more efficient to join tubular sections than open sections, such as I-sections.