Shear strengthening of reinforced concrete beams with hybrid composite plates

The effectiveness of Hybrid Composite Plates (HCPs) for the shear strengthening of the Reinforced Concrete (RC) beams was assessed by an experimental program. HCP is a thin plate of Strain Hardening Cementitious Composite (SHCC) reinforced with Carbon Fiber Reinforced Polymer (CFRP) laminates. Due to the excellent bond conditions between SHCC and CFRP laminates, these reinforcements provide the necessary tensile strength capacity to the HCP. Two HCPs with different inclination of CFRP laminates (45º and 90º) were adopted for the shear strengthening of RC beams by bonding these HCPs to the lateral faces of the beam with an epoxy adhesive. The results showed that these HCPs have assured a significant increase in terms of load carrying capacity, mainly those with inclined laminates. The SHCC surrounding the CFRP laminates in the HCP has offered effective resistance to the degeneration of micro-cracks on macro-cracks, which has avoided the occurrence of premature mixed shallow semi-pyramid-plus-debonding failure modes registered currently when using the NSM-CFRP technique. Advanced numerical simulations were performed by using a FEM-based computer program, whose predictive performance was demonstrated by simulating the experimental tests carried out. In this context a parametric study was executed to evaluate the shear strengthening efficiency of the arrangement and percentage of CFRP laminates in HCPs, as well as the influence of using mechanical anchors to avoid premature detachment of the HCPs.“PrePam –Pre-fabricated thin panels by using 17 advanced materials for structural rehabilitation” with reference number of PTDC/ECM/114511/200

Assessing the applicability of a smeared crack approach for simulating the behaviour of concrete beams flexurally reinforced with GFRP bars and failing in shear

Numerical simulation of beams failing in shear is still a challenge. With the scope of verifying the applicability of smeared crack approaches to simulate the behavior of reinforced concrete (RC) beams failing in shear, a set of concrete beams reinforced with longitudinal glass fiber reinforced polymer (GFRP) bars, experimentally tested up to their failure, and comprehensibly monitored, are numerically simulated. The simulations are carried out with a multi-directional fixed smeared crack model available in the FEMIX computer program that has several options for modeling the crack shear stress transfer, which is a critical aspect when simulating RC elements failing in shear. The predictive performance of the numerical simulations is assessed in term of load vs deflection, crack pattern at failure, concrete strains in critical shear regions, and moment–curvature relationship. The influence on the predictive performance of the following modeling aspects is also investigated: finite element mesh refinement; simulation of the crack shear stress transfer by using the classical shear retention factor and a crack shear-softening diagram; bond conditions between flexural reinforcement and surrounding concrete. The simulations carried out demonstrate that small dependence of the results on the finite element mesh refinement and adequate crack patterns can be obtained with refinement levels suitable for design purposes and taking into account the actual computer performances, as long as a crack shear-softening diagram is used. However, the predictive performance of the simulations depends significantly on the values adopted for the parameters that define this diagram, as demonstrated by the performed parametric studies.The first author aims to acknowledge the support provided by FCT through the research project ICoSyTec -Innovative construction system for a new generation of high performance buildings, with reference: POCI-01-0145-FEDER-027990

A new basic creep model coupled with a thermomechanical model for the numerical simulation of the time-dependent behaviour of concrete structures

This work is dedicated to the description of a new basic creep model that was developed and integrated in a thermo-mechanical model already available in a FEM-based software – FEMIX. The basic creep model is based on the Dirichlet series expansion of the Double Power Law (DPL) approach, and is capable of predicting the aging creep behaviour of cement based materials (CBM) since early ages. Based on experimental results, the model resorts to a non-linear least square datafitting operation to various loading ages creep compliance curves, and determines a set of model defining coefficients to simulate the aging viscoelastic properties of any CBM. This model was integrated with a thermo-mechanical model capable of simulating maturation, shrinkage and cracking phenomena of CBM. The good predictive performance of the implemented model is appraised by simulating experimental tests at material and structural scale.The authors acknowledge the support provided by FEDER funds through the Operational Programme for Competitiveness and Internationalization - COMPETE and by national funds through FCT (Portuguese Foundation for Science and Technology) within the scope of the project InOlicTower, POCI-01- 0145-FEDER-016905 (PTDC/ECMEST/2635/2014). The first Author would like to acknowledge the grant SFRH/BDE/96381/2013 co-funded by CiviTest and by FCT

Nonlinear analysis of offshore wind towers in prefabricated segments of prestressed fibre reinforced concrete

This paper presents the nonlinear finite element analysis of a new concept of offshore wind tower made by prefabricated prestressed fibre reinforced concrete (FRC) segments that are assembled to form the final structure. Fibre reinforcement aims to eliminate conventional passive steel reinforcement in order to avoid corrosion concerns and decrease the thickness of the segments. The first stage of the design approach consists on an analytical model that optimizes the geometry of the eolic tower by considering the relevant loading cases, the properties of the developed FRC, the resisting stress levels of the constituent materials and the frequency and lateral deformability of the tower. By determining the thickness and radius along with the height of the tower, this model can provide the solution of minimum FRC volume for the eolic tower. In the second stage of the design approach, the optimum solution from the previous design stage is simulated by a finite element approach that considers the geometric and material nonlinear features. This paper describes the main relevant aspects of this design methodology.This work was supported by FEDER funds through the Operational Programme for Competitiveness and Internationalization - COMPETE and by national funds through FCT - Portuguese Foundation for Science and Technology within the scope of the project InOlicTower - Innovative structural system based on advanced materials for lightweight and durable Offshore Wind Towers, POCI-01-0145-FEDER-016905 (PTDC/ECM-EST/2635/2014)

A numerical finite element study on connections of SFRC offshore wind towers with prestressed CFRP reinforcement and steel connectors

The growing need for sustainable production of electricity highlights the importance and the necessity of having higher number and more effective offshore wind towers. The rapid growth of offshore wind towers is estimated to produce 4% of electricity demands in Europe by the end of 2020. The research described in this paper is part of a project dedicated for the development of innovative structural system using advanced materials for lightweight and durable offshore towers. Specifically, it discusses the nonlinear finite element modelling of the connection between representative prefabricated rings of offshore wind tower made by steel fibre reinforced concrete (SFRC), and prestressed by a hybrid system of carbon fibre reinforced polymers (CFRP) bars and steel strands. This connection is assured by post-tension high steel strength cables and concrete-concrete shear friction width an idealized geometric configuration of the faces in contact. The model takes into account the loads from the rotor, wind and water currents, by considering the critical loading conditions for the safety verifications of serviceability and ultimate limit states. The material nonlinear analyses are carried out with FEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The parametric analyses involve the influence on the relevant results of the SFRC fracture parameters, pre-stress level of the reinforcements, shape of interlock mechanism, friction angle and interface cohesion.FEDER funds through the Operational 392 Programme for Competitiveness and Internationalization - COMPETE and by national funds 393 through FCT (Portuguese Foundation for Science and Technology) within the scope of the 394 project InOlicTower, POCI-01-0145-FEDER-016905 (PTDC/ECM-EST/2635/2014

Numerical analyses of the connections between representative SFRC prestressed rings of off-shore wind towers

Off-shore wind towers are the wind farms used to harvest wind energy to generate electricity on water bodies. With the growing need of sustainable production for electricity, off shore wind towers are finding a rapid growth in application. In fact, 4% of European electricity demands will be generated by offshore wind towers by 2020 in European waters. The current project concentrates on development of an innovative structural system using advanced materials for lightweight and durable offshore towers. The present paper discusses the nonlinear finite element modelling of the connections between representative prefabricated rings of off-shore wind towers made by steel fibre reinforced concrete (SFRC) and prestressed by a hybrid system formed by carbon fibre reinforced polymers (CFRP) bars and steel strands. The connection between these two rings are assured by post-tension high steel strength cables and concrete-concrete shear friction of treated surfaces. The model takes into account different types of loads and moments originating from rotor, wind and water currents considering the critical loading conditions. The material nonlinear analyses were carried out inFEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The SFRC rings are modelled by solid elements, and the longitudinal CFRP bars and steel strands by 3D embedded cables. Parametric studies are carried out in order to assess the influence of different fracture parameters of the SFRC and post-tension level in the cables (steel and CFRP) on the performance of the connection between the two rings.The authors acknowledge the support provided by FEDER funds through the Operational Programme for Competitiveness and Internationalization - COMPETE and by national funds through FCT (Portuguese Foundation for Science and Technology) within the scope of the project InOlicTower, POCI-01-0145-FEDER-016905 (PTDC/ECM-EST/2635/2014)

SARS-CoV-2 introductions and early dynamics of the epidemic in Portugal

Genomic surveillance of SARS-CoV-2 in Portugal was rapidly implemented by the National Institute of Health in the early stages of the COVID-19 epidemic, in collaboration with more than 50 laboratories distributed nationwide. Methods By applying recent phylodynamic models that allow integration of individual-based travel history, we reconstructed and characterized the spatio-temporal dynamics of SARSCoV-2 introductions and early dissemination in Portugal. Results We detected at least 277 independent SARS-CoV-2 introductions, mostly from European countries (namely the United Kingdom, Spain, France, Italy, and Switzerland), which were consistent with the countries with the highest connectivity with Portugal. Although most introductions were estimated to have occurred during early March 2020, it is likely that SARS-CoV-2 was silently circulating in Portugal throughout February, before the first cases were confirmed. Conclusions Here we conclude that the earlier implementation of measures could have minimized the number of introductions and subsequent virus expansion in Portugal. This study lays the foundation for genomic epidemiology of SARS-CoV-2 in Portugal, and highlights the need for systematic and geographically-representative genomic surveillance.We gratefully acknowledge to Sara Hill and Nuno Faria (University of Oxford) and Joshua Quick and Nick Loman (University of Birmingham) for kindly providing us with the initial sets of Artic Network primers for NGS; Rafael Mamede (MRamirez team, IMM, Lisbon) for developing and sharing a bioinformatics script for sequence curation (https://github.com/rfm-targa/BioinfUtils); Philippe Lemey (KU Leuven) for providing guidance on the implementation of the phylodynamic models; Joshua L. Cherry (National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health) for providing guidance with the subsampling strategies; and all authors, originating and submitting laboratories who have contributed genome data on GISAID (https://www.gisaid.org/) on which part of this research is based. The opinions expressed in this article are those of the authors and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government. This study is co-funded by Fundação para a Ciência e Tecnologia and Agência de Investigação Clínica e Inovação Biomédica (234_596874175) on behalf of the Research 4 COVID-19 call. Some infrastructural resources used in this study come from the GenomePT project (POCI-01-0145-FEDER-022184), supported by COMPETE 2020 - Operational Programme for Competitiveness and Internationalisation (POCI), Lisboa Portugal Regional Operational Programme (Lisboa2020), Algarve Portugal Regional Operational Programme (CRESC Algarve2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and by Fundação para a Ciência e a Tecnologia (FCT).info:eu-repo/semantics/publishedVersio

Numerical assessment of the potential of fibre reinforced shotcrete for structural strengthening of underground masonry tunnels

Strengthening and rehabilitation of underground tunnels are frequently an inseparable part of upgrading the railway network. Short fibres have been replacing pre-installed steel mesh with technical and economic ad vantages on the stabilization and securing of rock and soil systems in underground tunnels through the fibre reinforced shotcrete (FRS) technology. The strengthening efficiency of this technology can be even increased by shotcreting suitable arrangements of strain-softening and strain-hardening fibre reinforced concrete (SSFRC and SHFRC), despite requiring technological developments in terms of mix compositions and shotcrete equipment. The potential of combining SSFRC and SHFRC for the strengthening of underground tunnels is explored in this paper through numerical simulations based on the finite element method. The predictive performance of the adopted material nonlinear constitutive models is initially validated by simulating experimental tests where SSFRC and SHFRC were used for the strengthening of masonry elements or for the prefabrication of tunnel segments. By using a layered curved shell model, the potential of various strengthening configurations is assessed for a typical Portuguese underground tunnel by demonstrating the gains in terms of stiffness and load carrying capacity when proper use of SSFRC and SHFRC is adopted. It is revealed that, by using a shotcrete technology capable of placing SSFRC and SHFRC in layers according to the outputs of advanced numerical analysis, an efficient strengthening system with a significant reduction of consumed materials can be achieved.This study is a part of the project ‘‘IN2TRACK3 – Research into optimised and future railway infrastructure (Shift2Rail)’’, Contract No. H2020-S2RJU-CFM-2020, supported by EU and coordinated by the Swedish Transport Administration (Trafikverket). The first author acknowledge the research grant provided by this project

A new inverse analysis approach for predicting the fracture mode I parameters of fibre reinforced concrete

This paper describes the development of a new inverse analysis approach to derive the fracture mode I parameters of fibre reinforced concrete (FRC) by using the experimental data obtained from three-point notched beam bending tests (3PNBBT) and round panel tests supported on three points (RPT-3PS). The approach is based on a global fitting strategy, in which the numerical response is simulated by means of analytical models, and fitted to the experimental results by modifying the variables that govern the tensile behaviour of FRC. The fitting procedure relies on a bounded multi-variable nonlinear least squares fitting algorithm, coupled with an automatic updating procedure of the input parameters based on the force deviation error between numerical and experimental results. The performance and predictive potential of the proposed approach are assessed by means of experimental results from 3PNBBT and RPT-3PS retrieved from the literature. Also, the robustness of the implemented methodology is also investigated by evaluating the impact of the initial guess of the input variables in the derived fracture parameters. Finally, the developed tool is applied within the context of the analysis of a real-scale FRC beam, where the mode I fracture parameters were derived using the newly proposed methodology.The first author acknowledges the financial support provided by Fundação para Ciência e Tecnologia (FCT), Portugal through the grant PD/BD/135174/2017. The FCT, Portugal support from the project POCI-01-0145-FEDER-027990 (PTDC/ECI-CON/27990/2017) is also acknowledged

Experimental and Numerical Simulation of a Radiant Floor System: The Impact of Different Screed Mortars and Floor Finishings

The radiant floor system market is growing rapidly because Europe is moving toward a low-carbon economy and increased awareness about environmental sustainability and energy efficiency, stimulated by the ambitious EU Energy Efficient Directive and nZEB challenge. The high growth rate of the market share is due to the involvement of homeowners in the specifications of their living commodities, so they are thus willing to invest more at the initial stage to obtain long-term benefits and lower energy exploration costs. We performed an experimental campaign over three slabs with a hydronic radiant floor system of equal dimensions, shape, and pipe pitch with different screed mortar formulations to assess their performance throughout a heating/cooling cycle. The temperature at different heights within the interior of the screed mortars and at the surface were monitored. The results revealed that an improved screed mortar has a relevant impact on the efficiency of the system. Moreover, a three-dimensional transient heat transfer model was validated using the experimental data. The model was used to evaluate the impact of different finishing materials, namely wood, cork, ceramic, and linoleum, on the floor surface temperatures. The results showed differences of 15% in the surface temperature when using different floor finishing solutions