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Dimensioning adhesively bonded joints remains a challenging task. Their diversity in geometry and material (including combinations thereof), characteristic stress peaks, scatter and brittleness are aspects few practitioners are prepared to handle for dimensioning purposes. As developed in the first part of this two-part paper, direct stress based methods, despite diverse fudging techniques, proved to be unsuitable. This left the field open for fracture mechanics, which, however, departed very much from the engineering reality leading to only lukewarm acceptance from practitioners. Almost unnoticed, probabilistic methods, much closer to classical mechanics, may offer an alternative. Based upon the presentation, in the first part of this series, of the concepts, the authors suggested an implementation in terms of design procedure. The second part of this two-part paper, is dedicated to the presentation of several examples, from available literature, of adhesively bonded joints involving a large variety of typologies (single and double-lap, tubular, and hybrid joints) and materials (fibre-reinforced polymers, steel, wood). The focus therein is set on practitioner oriented aspects, in particular on techniques for implementation.

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.

This paper presents an experimental study about the development of a sustainable and multifunctional composite sandwich panel for the rehabilitation of reinforced concrete (RC) buildings from the 1960s to the mid-1980s. For this purpose, the cyclic behaviour of representative RC frames was assessed by performing in-plane quasi-static cyclic tests on three different specimens: (i) a bare RC frame (individual behaviour of the frame); (ii) an RC frame with masonry infill wall (representative of target buildings); and (iii) an RC frame strengthened with an innovative sandwich panel formed by outer wythes in recycled steel fibre reinforced micro-concrete and polystyrene core layer. The results show that, in comparison with the traditional masonry infill wall solution, the proposed rehabilitation solution significantly improved the cyclic performance of the RC frame, reaching higher levels of load carrying capacity (395% vs. 349% increase) and energy dissipation (700% vs. 524% increase). Moreover, the sandwich panel has maintained its structural integrity with low level of damage in its internal load-bearing layer for high values of lateral drift (up to 2.1%)., The first author wishes to acknowledge the financial support provided by the Portuguese Foundation for Science and Technology (FCT) and the Eco-Construction and Rehabilitation (EcoCoRe) Doctoral Program through the research grant PD/BD/52657/2014. The authors would like to thank the collaboration and support of the following companies for supplying/producing different components: (i) Twincon (RSF); (ii) Tecnipor (RC-frames); (iii) CiviTest (sandwich panel prototype); (iv) BVT–Rausch and PreConTech (functional GFRP connectors); (v) Sch¨ock Bauteile GmbH (structural GFRP connectors); (vi) Hilti (mechanical and adhesive anchoring systems); and (vii) Danosa/Eurofoam (extruded polystyrene plates). The authors also wish to thank the Structural Laboratory from University of Minho.

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.

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...

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.

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 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.

The use of glass fibre reinforced polymer (GFRP) composites in civil engineering structures has seen considerable growth in recent years due to their high strength, low self-weight, and corrosion resistance, namely when compared to traditional materials, such as steel and reinforced concrete. To enable the structural use of GFRP composite materials in civil engineering applications, especially in footbridges, it is necessary to gather knowledge on their structural behaviour, particularly under dynamic loads, and to evaluate the ability of current design tools to predict their response. In fact, excessive vibration has a major influence on the in-service performance (comfort) of slender structures as well on their service life. The use of composite materials that combine high damping capacity with relatively high stiffness and low mass can provide functional and economic benefits, especially for footbridges. This paper aims to investigate the dynamic behaviour of GFRP free-supported beams to evaluate their modal characteristics (frequency, damping, and modal shape). To assess the benefits of using a structure made of pultruded GFRP rather than a conventional material—steel, a comparative analysis between the dynamic characteristics of GFRP and steel beams is performed. To specifically address material damping and to minimize the interference of the boundary conditions, the beams are tested in a free condition, resting on a low-density foam base. The results show that the damping capacity of GFRP is much higher than that of steel, as the measured damping factor of GFRP is five times higher than that of steel for the same boundary conditions and similar geometry. Furthermore, the fact that the frequencies of the tested specimens resemble for the two different materials highlights the perceived damping qualities of the polymer-based composite material. Finally, an energy method for evaluating the influence of the scale factor on material damping is applied, which made it possible to infer that the damping varies as a function of frequency but is not explicitly affected by the length of the specimens.

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.

This paper presents a novel approach concerning the development of an orthotropic damage model for composite materials, based on the original plane stress Tsai–Wu failure criterion. In its original formulation, the Tsai–Wu is a mode-independent criterion only capable of acknowledging the existence of damage in a certain point of a composite material. It is not capable of identifying if the damage is located in the fibre, matrix or interlaminar zone. This study aims at filling this gap in knowledge by providing a simple method, based on equivalent stresses and strains, that identifies the relevant failure modes when the Tsai–Wu failure criterion is at the onset of damage. Using this novel methodology, it is possible to implement classical damage evolution constitutive laws based on the fracture energy regularization. At present, the proposed damage formulation is based on the consideration of a plane stress space and Mode I fracture, but its generalization to a full 3D damage model is expected to be defined in the near future. The damage model is implemented in the commercial finite element software ABAQUS through a user-defined material (UMAT) subroutine, and all numerical models are compared with experimental results available in the literature.

This two-part paper proposes a resistance format and partial factors for the global buckling of FRP profiles based on reliability analysis and partial factor calibration. Most current recommendations for the design of structural members made with FRP materials are not grounded on reliability concepts and this poses questions concerning safety and economy. Part 1 of this paper presents the resistance format proposed, the approach to the variability of material properties, the resistance models, and the design equations for the following global buckling modes: (i) flexural, (ii) flexural-torsional, and (iii) lateral-torsional; all of them refer to well-known formulations available in the literature. Probability distributions for the model uncertainties of the resistance models are defined based on all trustworthy experiments collected by the authors from the literature. In general, the three resistance models proposed provide estimates of the critical buckling stress with good accuracy when compared to the observed (tested) buckling resistance, resulting in an average bias close to one. The coefficient of variation of the model uncertainties varies between 11% (flexural buckling) and 19% (flexural-torsional buckling). Preliminary partial factors are proposed in this part and their reliability-based calibration is presented in Part 2.

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. .

Understanding and modeling the viscoelastic behavior of polymers and polymer-based materials for a wide range of quasistatic and high strain rates is of great interest for applications in which they are subjected to mechanical loads over a long time of operation, such as the self-weight or other static loads. The creep compliance and relaxation functions used in the characterization of the mechanical response of linear viscoelastic solids are traditionally determined by conducting two separate experiments&mdash, creep tests and relaxation tests. This paper first reviews the steps involved in conducting the interconversion between creep compliance and relaxation modulus in the time domain, illustrating that the relaxation modulus can be obtained from the creep compliance. This enables the determination of the relaxation modulus from the results of creep tests, which can be easily performed in pneumatic equipment or simple compression devices and are less costly than direct relaxation tests. Some existing methods of interconversion between the creep compliance and the relaxation modulus for linear viscoelastic materials are also presented. Then, a new approximate interconversion scheme is introduced using a convenient Laplace transform and an approximated Gamma function to convert the measured creep compliance to the relaxation modulus. To demonstrate the accuracy of the fittings obtained with the method proposed, as well as its ease of implementation and general applicability, different experimental data from the literature are used.

The accurate analysis of the behaviour of a polymeric composite structure, including the determination of its deformation over time and also the evaluation of its dynamic behaviour under service conditions, demands the characterisation of the viscoelastic properties of the constituent materials. Linear viscoelastic materials should be experimentally characterised under (i) constant static load and/or (ii) harmonic load. In the first load case, the viscoelastic behaviour is characterised through the creep compliance or the relaxation modulus. In the second load case, the viscoelastic behaviour is characterised by the complex modulus, E*, and the loss factor, &eta, In the present paper, a powerful and simple implementing technique is proposed for the processing and analysis of dynamic mechanical data. The idea is to obtain the dynamic moduli expressions from the Exponential-Power Law Method (EPL) of the creep compliance and the relaxation modulus functions, by applying the Carson and Laplace transform functions and their relationship to the Fourier transform, and the Theorem of Moivre. Reciprocally, once the complex moduli have been obtained from a dynamic test, it becomes advantageous to use mathematical interconversion techniques to obtain the time-domain function of the relaxation modulus, E(t), and the creep compliance, D(t). This paper demonstrates the advantages of the EPL method, namely its simplicity and straightforwardness in performing the desirable interconversion between quasi-static and dynamic behaviour of polymeric and polymer-composite materials. The EPL approximate interconversion scheme to convert the measured creep compliance to relaxation modulus is derived to obtain the complex moduli. Finally, the EPL Method is successfully assessed using experimental data from the literature.

Background and aims As the COVID-19 pandemic emerged, departments had to adapt their activities, jeopardizing patient's best interests. Our aim is to evaluate the patient's perspective to the implementation of SARS-CoV-2 measures in a gastroenterology department in a Portuguese Hospital. Methods A survey with 13 questions was created and available to patients with at least one gastroenterology appointment at our center in the year 2019. Results Nine hundred seventy-three patients completed the survey, 51.6% (n = 502) females, and 82.6% (n = 804) with less than 65 years of age. 50.7% of 962 patients were not working. 49.5% had an appointment for monitoring a suspected or established inflammatory bowel disease (IBD). 76.8% and 69.6% subjects agreed in postponing endoscopic and non-endoscopic procedures, respectively. 93.6%, 94.3% and 95.7% patients declared to be worried about the postponing of endoscopic procedures, non-endoscopic procedures and medical visits, respectively. 88.8% supported remote consultations and 77.3% were satisfied with this type of appointment, independently of the age group (P = 0.66). 80.9% of IBD patients treated with immunosuppression or biologics were concerned about a severe infection by COVID-19. Conclusion A great part of our respondents belong to IBD appointments. The majority of our patients agreed in postponing procedures, although they feel concerned. Almost all patients supported remote consultations and most patients found them positive.

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...

Thermal mortars incorporating insulating aggregates are a possible solution to ensure good thermal performance and thermal comfort in buildings due to their low thermal conductivity coefficient. Under some circumstances, namely for particular in-service conditions in industrial applications and/or accidental actions (such as fire), it is important to quantify the retention of their properties after exposure to elevated temperatures, however this information is not yet available in the literature. This study aims to characterize the physical and mechanical behavior of thermal mortars incorporating expanded clay, granulated expanded cork and silica aerogel as aggregates after exposure to elevated temperatures. To this end, five types of mortars were produced in laboratory conditions&mdash, three thermal mortars, one reference sand mortar and one sand mortar with admixtures&mdash, and then exposed to different elevated temperatures (from 20 &deg, C to 250 &deg, C) in a thermal chamber. After thermal exposure, the following properties were assessed: bulk density, ultrasonic pulse velocity, dynamic elasticity modulus, dynamic shear modulus, Poisson coefficient, compressive strength, and thermal conductivity. The results obtained show that residual properties present a very high dependence on the reactions that take place in the cement paste when the mortars are exposed to elevated temperatures. After such exposure, all mortars with thermal insulating aggregates were able to maintain their insulating characteristics, but experienced internal damage and degradation of their mechanical properties. Results obtained also showed that insulating aggregates allowed to produce mortars with higher aggregate-cement paste compatibility at elevated temperatures compared to conventional mortars, resulting in less micro-cracking of the mortar, and leading to lower reductions in thermal conductivity with increasing temperature.

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.