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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.

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.

Composite sandwich panels are being increasingly considered for civil engineering structural applications, offering high versatility in constituent materials and their geometrical arrangement. This translates to a high number of design variables, in addition to a potentially large number of design requirements and objectives related to the panels’ functions. This paper presents an optimization study of a composite sandwich panel system for building floor rehabilitation, using the Direct MultiSearch (DMS) method. Pultruded multicellular panels with a polyurethane (PUR) foam core and carbon- or glass-fibre reinforced polymer (C/GFRPF) faces and ribs/webs are considered. The panel architecture was defined using 3 geometrical variables and 14 material related variables. In addition, 8 competing objective functions were studied, related to aspects such as structural serviceability and resistance, thermal insulation, acoustic performance, cost minimization, and environmental performance. The results are presented in the form of Pareto optimal sets, from which several conclusions are drawn regarding common design-related options. The influence of core material density, of the number of ribs/webs, or of the type of fibre reinforcement and its respective layup on the different objective functions are addressed. Optimal solutions for meeting different design purposes are presented, providing useful insights for structural designers and sandwich panel manufacturers.

This paper presents a numerical study about the flexural behaviour of rectangular composite glass-GFRP beams, comprising annealed glass and GFRP pultruded profiles bonded with two different adhesives: (soft) polyurethane and (stiff) epoxy. The main objectives of this study were: (i) to fully characterize the non-linear behaviour of glass using the smeared crack approach; and (ii) to assess the applicability of different options to simulate adhesively bonded glass-GFRP joints. An extensive parametric study was developed to evaluate the influence of five parameters on the glass post-cracking non-linear behaviour: (i) glass fracture energy, Gf, (ii) crack band width, h, (iii) glass tensile strength, fg,t, (iv) shape of the tension-softening diagram, and (v) shear retention factor, β. The wide range of the joints’ shear stiffness was simulated by either (i) assuming a perfect bond between glass and GFRP (i.e., neglecting the presence of the adhesive), or (ii) explicitly considering the adhesive, by means of using (ii.1) plane stress elements, or (ii.2) interface elements. For the beams analysed in this paper, the following material model for glass provided a good agreement with experimental results: Gf in the range of 3 to 300 N/m, h equal to the square root of the finite element area, fg,t = 50 MPa, linear softening diagram and β according to a power law. It was also shown that the hypothesis of perfect bond at the GFRP-glass interfaces allows for an accurate simulation of joints with high levels of interaction (epoxy), while calibrated interface elements are needed for joints with low level of interaction (polyurethane)., The authors wish to acknowledge FCT, ICIST/CERIS and ISISE for funding the research, and companies SIKA, Guardian and ALTO for supplying the adhesives, the glass panes and the GFRP pultruded profiles used in the experiments. The first author also wishes to thank FCT for the financial support through his PhD scholarship SFRH/BD/80234/2011.

A three-year research project (Pontalumis) was carried out for the development of an innovative simply supported hybrid footbridge, with 11 m of length and 2 m of width. The footbridge is composed of two pultruded I-shaped glass fibre reinforced polymer (GFRP) girders (400×200(×15) mm2) bonded and bolted to a 37.5 mm thick deck in steel fibre reinforced self-compacting concrete (SFRSCC). The present paper describes the material/structural concept of this footbridge, its design and construction process, and summarizes the response of the prototype when submitted to static short and long-term load tests, and dynamic load tests. The prototype was simple and fast to execute, presenting a reduced dead-weight of only about 3 tonf. The static and dynamic behaviour of the prototype as well as its long-term deflection fulfil standards’ requirements for footbridge structures and are in good agreement with conventional analytical and numerical design tools., ADI

Flat roofs in current buildings include a waterproofing system, often made of bituminous membranes with a self-protection constituted by mineral granules. These granules constitute the barrier against the fundamental environmental agent of degradation, the UV radiation. Therefore it is of paramount importance to understand the long-term performance of the self-protection layer, namely its adhesion to the coatings of bituminous membranes. This paper presents an experimental study on the behaviour of the self-protection granule of bituminous membranes when subjected to environmental agents of degradation. Different types of atactic polypropylene (APP) and styrene–butadiene–styrene (SBS) modified bituminous membranes, comprising different finishing systems, were exposed to the effects of elevated temperature and water for up to 24 weeks and 4 weeks, respectively. Following accelerated ageing, specimens of the different types of membranes were subjected to brushing tests, carried out according to EN 12039, in order to evaluate the adhesion of the self-protection granules. The results obtained in this study, which are compared with performance limits recommended by UEAtc directives, show that the higher loss of self-protection granule of bituminous membranes occurs in membranes modified by APP polymers. In addition, it was concluded that the effect of water is much more severe than that of elevated temperature.

Presently, mechanically fastened waterproofing systems are widely used in large roofs, mostly in industrial and commercial buildings. This paper presents a study of this constructive system that included the analysis of the mechanisms of response to wind loads and the effects of the different components on the system’s wind resistance. Wind up lift tests were performed on mechanically fastened waterproofing systems, according to the guideline for European technical approval (ETAG 006), in order to evaluate the influence of both the thermal insulation thickness (from 40 mm to 100 mm) and the characteristics of the atactic polypropylene (APP) modified bitumen waterproofing membranes (different constitutions, single/double layer) on the resistance to wind up lift. All tested mock-ups failed due to peeling of the overlapping membranes. Within the range of analysed systems, the thickness of the thermal insulation and the characteristics of the waterproofing membranes did not present a noticeable effect on the resistance of the tested mock-ups. Results obtained in the experimental tests were compared to other results gathered from European technical approvals. Additionally, results were used to define the field of application of the tested systems to a National level, based on the wind loads defined in the Portuguese code and the design procedure presented in Eurocode 1 and ETAG 006.

This paper presents an experimental and analytical study about the effect of temperature on the flexural creep of GFRP laminates produced by vacuum infusion. Such laminates are considered for use in the faces of sandwich panels for building floor application. Flexural creep tests were carried out in a three point bending configuration for stress levels of 15%, 25% and 35% of the laminate's flexural strength, and temperatures of 20 degrees C, 24 degrees C and 28 degrees C (a range likely to be found in the envisaged application), with durations between 1000 h and 2215 h. The creep response was observed to increase both with temperature and stress level. Findley's power law was used to model the experimental results, and extended to include an Arrhenius equation for temperature dependence of the creep response. The proposed model provided a good fit to the experimental creep curves, and was used to derive a set of practical design equations for the time-temperature dependent (i) flexural modulus, (ii) creep coefficient, and (iii) flexural modulus reduction factor. Finally, the time-temperature-stress superposition principle (TTSSP) and the time-stress superposition principle (TSSP) were used to obtain "master curves" that compared well with the proposed model's predictions. (C) 2016 Elsevier Ltd. All rights reserved.

Composite sandwich panels comprising fibre reinforced polymer (FRP) skins and lightweight material cores are being increasingly used in civil engineering. In several applications, such as fa ades, roof structures and bridge decks, these panels may experience a wide range of in-service temperatures. This paper presents experimental and analytical investigations about the effects of elevated temperature on the shear response of polyethylene terephthalate (PET) and polyurethane (PUR) foams used in composite sandwich panels. The experimental programme included (i) DMA and DSC/TGA tests, aimed at assessing the glass transition and decomposition processes underwent by those foams; and (ii) Iosipescu tests for temperatures ranging from -20 degrees C to 120 degrees C, in order to characterise their shear response. The analytical study comprised the assessment of the accuracy of different empirical (relaxation) models in describing the shear modulus reduction with temperature of those polymeric foams. Results obtained show that with increasing temperature, the shear responses of PET and PUR foams become more markedly non-linear. In addition, the shear moduli of these foams suffer considerable reductions, particularly for the PET foam; although at ambient temperature (similar to 20 degrees C) the PET foam is 3 times stiffer than the PUR foam, at 80 degrees C their shear moduli become similar, being respectively 24% and 66% of those at ambient temperature. All relaxation models assessed in this study were able to simulate with good accuracy the variation of the shear modulus of both foams with temperature. (C) 2014 Elsevier Ltd. All rights reserved.

The use of advanced composites for building rehabilitation presents several advantages when compared with traditional construction materials. When degraded building floors need to be replaced, composite sandwich panels are a potentially interesting solution, namely for buildings with load-bearing rubble masonry walls. In this paper, connection systems between composite sandwich floors and load-bearing walls are proposed, and their behaviour under vertical loading is investigated. The systems comprise steel angles anchored to the walls, serving as main supports of the sandwich panels, which are then adhesively bonded and/or bolted to the angles. These connection systems are experimentally assessed using sandwich panels made of glass-fibre reinforced polymer (GFRP) face sheets and cores of either polyurethane (PUR) foam or balsa wood, by means of flexural tests on cantilevers, which are also simulated using non-linear finite element models. The structural response of the connection systems is determined, including the rotational stiffness conferred to the floors, the strength and the failure modes. Moment-rotation relationships are obtained for the connection systems and sandwich panel types considered, which provide a wide range of rotational stiffness values, from 60 to 10,856 kNm/rad per unit width (m). These are then used to analytically estimate the short-term mid-span deflections of floors with semi-rigid connections and spans ranging between 2 m and 5 m. It is shown that some of the proposed connections allow significant floor stiffness increases compared with simply supported conditions, with reductions in total mid-span deflection of up to 65% being achieved for a span of 4 m. The results obtained for the proposed connections highlight (i) their potential benefits for fulfilling serviceability limit states and (ii) the importance of considering an adequate structural model when designing sandwich floor panels. (C) 2015 Elsevier Ltd. All rights reserved.

A connection system between adjacent sandwich panels for use in building floor rehabilitation, consisting of an adhesively (epoxy) bonded Z-joint, is proposed and studied. Experimental and numerical investigations were carried out to assess the joints' behaviour under vertical loads, their effect on the overall mechanical response of the sandwich floor panels, and the stress distributions within the various panel components. Their behaviour along the transverse and longitudinal (main span) directions was studied for panels made of glass-fibre reinforced polymer (GFRP) faces and two types of cores: polyurethane (PUR) foam and balsa wood. The joints' failure along the transverse direction occurred in the GFRP elements due to excessive through-thickness tensile stresses failure in the adhesive layer was not observed. In the longitudinal direction, joint failure did not occur. The developed FE models were able to simulate the behaviour of the connections and jointed panels, providing reasonably accurate predictions for the deformations and failure modes experimentally observed. The joints significantly increased the panels' shear stiffness, but showed limited influence on their bending stiffness. Although the flexural stiffness of the PUR foam and balsa wood cored panels was similar, the balsa wood core absorbed a significantly higher portion of shear force. (C) 2015 Elsevier Ltd. All rights reserved.

Pultruded glass fibre reinforced polymer (GFRP) profiles are finding increasing applications in civil engineering structures, owing to the several advantages they offer over traditional materials. However, due to the combustible nature of their polymer matrix, there are well-founded concerns about their behaviour at elevated temperature and under exposure to fire. These concerns are hindering the widespread acceptance of GFRP profiles, particularly in buildings, which need to comply with relatively strict requirements in terms of fire reaction and fire resistance behaviour. This paper presents a review about the fire performance of pultruded GFRP profiles. It first addresses the effect of elevated temperature on the thermophysical and thermomechanical properties of the pultruded GFRP material. Then the fire reaction properties of pultruded GFRP profiles and the effects of different fire protection measures on those properties are discussed. Next comes a section reviewing previous experimental and modelling studies about the fire resistance behaviour of different types of GFRP structural members. The final part of the paper provides a summary of the design guidance set out in the most relevant guidelines and codes applicable to pultruded GFRP structures. The most pertinent research needs for the various fire behaviour aspects addressed are also identified. (C) 2015 Elsevier Ltd. All rights reserved.

Silicate-based impregnations are often used to protect concrete against aggressive external actions. However, the understanding of several aspects concerning this type of impregnations is still rather Iimited, incIuding the influence of the concrete substrate on their performance. This paper presents reslllts of an experimental study about O) the efficacy of silicate-based impregnations to protect concrete elements, and (ii) the inflllence of the concrete substrate's characteristics on the performance of such superficial protection. Concrete specimens with two different water/cement ratios (0.40 and 0.70) were produced and, prior to the application of the impregnation, were prepared following different procedllres that created O) three different surface roughnesses (no surface preparation, 160 bar water jet and needle scalers) and (ii) three different moisture contents (3.0%, 4.5% and 6.0%). The performance ofunprotected and protected concrete specimens was assessed by means of the following procedures, indicated in EN 1504-2 standard: O) product penetration depth; (ii) water absorption by immersion; (iii) abrasion resistance; Ov) impact resistance; and (v) bond strength. Results obtained show that the silicate-based impregnation was effective in improving the resistance to water penetration and abrasion resistance, but did not improve the resistance to impacto The surface roughness and the moisture content at the instant of the application of the surface protection proved to influence the performance of the impregnation product, however such influence was dependent on the property at stake. 191-200pp Vol 70 (2014) DM/NMO Construction and Building Materials