Joaquim A.O. Barros

• PhD
• Professor (Full) at University of Minho

The rehabilitation of fire-damaged concrete structures often presents a challenge, leading to costly demolition and reconstruction. This study explores the potential of fiber-reinforced polymer (FRP) passive confinement systems, specifically full, partial, and hybrid configurations, as effective solutions for restoring the compressive strength of h...

Given the magnitude of investigations conducted on axially-loaded FRP-confined concrete columns in the past two decades, the focus of these studies was mainly given on FRP-confined concrete with a full strain hardening behavior, categorized as Type A. Nonetheless, for a reliable design of FRP confinement arrangements imposed to concrete, it is esse...

Traditional hard engineering solutions have shown weaknesses in mitigating erosion processes in vulnerable coastal areas, contributing in some cases to their aggravation, which makes it necessary to study innovative nature-based engineering solutions. This research deals with an in-depth analysis of hydro-morphodynamic modelling results for optimiz...

This study investigates the effectiveness of a hybrid solution that combines carbon fiber-reinforced polymer (CFRP) systems for the flexural and shear strengthening of T-cross section reinforced concrete (RC) beams. The hybrid solution consists of near-surface mounted CFRP laminates for flexural enhancement and externally bonded U-shaped CFRP strip...

Despite several confinement models available in the literature to calculate the axial behavior of fiber-reinforced-polymer (FRP) confined concrete columns at ambient conditions, a reliable design-oriented model to obtain the behavior of heat-damaged concrete columns post-confined with FRP is still lacking. This study aims to address this research g...

This study aims to evaluate the flexural behavior of I-shaped cross-sectional steel-fiber-reinforced concrete (SFRC) beams that are reinforced with prestressed glass fiber reinforced polymer (GFRP) and steel rebars (hybrid reinforcement, HR). The results obtained in the experimental tests on these SFRC beams are compared with those of reinforced co...

This paper describes the 3rd Blind Simulation Competition (BSC) organized by the fib WP 2.4.1 which aims to assess the predictive performance of models based on the finite element method (FEM) for analysis and design of fiber reinforced concrete (FRC) structures submitted to loading and support conditions that promote punching failure mode. Fiber r...

Even though many experimental studies have evidenced that fiber-reinforced polymer (FRP)-confined concrete columns under compression might exhibit a post-peak strain softening response, followed by a hardening behavior (a stress reduction-recovery response), most existing models are only applicable to confined columns developing full hardening beha...

Coastal erosion poses significant challenges to shoreline management, exacerbated by rising sea levels and changing climate patterns. This study investigates the influence of gap spacing between semicircular coastal defence structures on shoreline dynamics during storm events. The innovative design of these structures aims to induce a drift reversa...

Masonry structures are susceptible to damage and collapse due to seismic actions, a problem in many urban areas. To address this issue, researchers are studying the use of fibre-reinforced mortars as overlay strengthening systems. This study assessed the use of synthetic polyacrylonitrile (PAN) fibres as reinforcement of natural hydraulic lime mort...

Many research studies have been conducted to evaluate confinement-induced enhancements on the mechanical properties of FRP (fiber-reinforced polymers)-confined plain concrete elements subjected to axial compressive loading, leading to the development of extensive predictive models. Nevertheless, experimental stress-strain results for FRP-confined R...

The behaviour of reinforced concrete (RC) beams shear strengthened with fibre-reinforced polymer (FRP) has been extensively studied. Numerous analytical models have been proposed to predict the shear contribution of externally applied FRP to RC beams. Due to the continuous increase of experimental data, it is fundamental to assess the predictive pe...

By performing an experimental program, the performance of a hybrid solution using carbon fiber reinforced polymer (CFRP) systems for the simultaneous flexural and shear strengthening of T-cross section RC beams is assessed. In this solution, CFRP laminates are applied according to the near surface mounted technique for the flexural strengthening, w...

This article explores the application of the global resistance methods (GRMs) on the design of hybrid glass fiber-reinforced polymer (GFRP) and steel fiber-reinforced concrete (SFRC) beams. Addressing challenges posed by GFRP-reinforced beams, this study aims to assess the impact of material uncertainties on the behavior of such hybrid beams. The i...

The fib WP 2.4.1 is a technical committee of the fib organization (https://www.fib-international.org/commissions/com2-analysis-design.html) dedicated to the development of methodologies for the design of fibre reinforced concrete (FRC) structures using computer programs based, mainly, on the finite element method (FEM). For taking advantage of the...

This research work presents nature-based innovative structures for addressing coastal erosion mitigation, based on the observation of alongshore drift reversal phenomena. Hydro-morphodynamics and wave climate predictions for storm conditions near the Iberian Peninsula shoreline were analysed for defining an optimized maritime structure geometry. Fu...

Even though several stress-strain models have been proposed for FRP-confined concrete columns subjected to axial compressive loading, very few models are able to predict an axial response featuring post-peak strain softening behavior. Furthermore, the reliability of most of these models are limited only to a certain concrete strength class (either...

Determination of fiber-reinforced polymer (FRP) confinement-induced improvements in the mechanical properties of concrete columns under compression is a current concern, particularly if partial confinement applied on a noncircular cross-sectional shape is to be considered. Although several design-oriented predictive formulations have been proposed...

This paper investigates a hybrid strengthening technique that combines the near-surface-mounted (NSM) technique for flexural strengthening with the embedded through section (ETS) technique for shear strengthening using innovative stick-shaped CFRP rebars. The study focuses on the mechanical properties and bond behavior of 7 mm square-sectioned, 30°...

Strengthening of reinforced concrete (RC) structures has been always a great engineering deal. Nowadays, with the global awareness of the environmental impacts of construction industry, and specially the considerable share of this sector in CO2 emission and global warming, it is of a great importance to increase the service life of existing structu...

An experimental and numerical investigation on the behavior of a new replaceable steel device (RSD), is presented in this paper. The RSD consists of a steel pipe with two circular steel plates that close the ends of the tube, four stiffeners, and an added damping and stiffness (ADAS)-type steel plate that functions as a fuse element. This RSD is ch...

Although there are several confinement models to obtain analytically the axial stress-strain response (fc-ec) of concrete columns wrapped with fiber-reinforced-polymer (FRP) jacket at ambient conditions, a reliable design-oriented model to determine the fc-ec of heat-damaged concrete columns post-confined with FRP is still lacking in the literature...

The compressive behavior of steel-fiber-reinforced-concrete (SFRC) is dependent on the loading rate. This research investigates, experimentally and analytically, the effect of loading rate on the compressive behavior of SFRC designed to be used in prefabricated urban protective furniture. For this purpose, cylinder SFRC specimens were subjected to...

As soluções tradicionais de engenharia têm demonstrado fragilidades na mitigação dos processos erosivos em zonas litorais vulneráveis, contribuindo, em alguns casos, para o seu agravamento. No presente trabalho, apresentam-se resultados de modelação hidro-morfodinâmica de um estudo comparativo do desempenho de uma estrutura marítima inovadora com o...

This paper is dedicated to the development of a new analysis-oriented model to simulate the axial and dilation behavior of FRP confined heat-damaged concrete columns under axial compressive loading. The model’s calibration has considered the experimental results from concrete circular/square cross-section specimens submitted to a certain level of h...

This article describes the second blind simulation competition (BSC) organized by the fib WG 2.4.1, which aims to assess the predictive performance of models based on the finite element method (FEM) for the analysis and design of fiber reinforced concrete (FRC) structures. Slabs supported on columns or piles have becoming competitive applications f...

The present work describes the analysis of a long and jointless concrete foundation reinforced with conventional steel meshes and discrete polypropylene fibers. A thermo-mechanical nonlinear transient simulation is performed to assess the cracking risk and magnitude of the fiber reinforced concrete (FRC) due to the heat development generated from t...

Although a variety of analytical modeling approaches have been developed to simulate the axial response of Fiber-Reinforced Polymer (FRP) confined concrete columns, little effort has been dedicated to the development of simple but robust predictive models for heat-damaged concrete columns with FRP confinement. This study aims to present a new unifi...

Even though analysis-oriented models exist to simulate the axial and dilation behavior of reinforced concrete (RC) columns strengthened with fiber-reinforced-polymer (FRP) full confinement arrangements, a reliable model developed/calibrated for FRP partially imposed confinements is not yet available, identified as a research gap. Therefore, this pa...

Experimental research on the direct shear behavior of fiber-reinforced concrete is often carried out using prisms molded with specific dimensions for a standardized test. However, the flow of fresh concrete in these molds can be different than in the case of a full-scale structural element. This is important considering that the flow direction high...

Even though analysis-oriented models exist to simulate the axial and dilation behavior of reinforced concrete (RC) columns strengthened with fiber-reinforced-polymer (FRP) full confinement arrangements, a reliable model developed/calibrated for FRP partially imposed confinements is not yet available, identified as a research gap. Therefore, this pa...

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 advantages on the stabilization and securing of rock and soil systems in underground tunnels through the fibre reinforced shotcrete (FRS) t...

This study is a systematic effort focused on the development of feasible self-sensing braided composite rods (BCRs) for structural reinforcement and damage monitoring. In this route, BCRs were produced and reinforced with different carbon-based conductive fillers, including hybrid carbon nanotubes (CNTs)/graphene nanoplatelets (GNPs), chopped carbo...

Despite the many axial confinement models already proposed for the determination of the peak compressive strength of Fiber-Reinforced Polymer (FRP) confined concrete columns, they are, in general, applicable only to concrete columns of circular or square cross-section, with full or partial confinement arrangements. In this study, by proposing a cro...

Although steel and concrete composite floors are generally constructed with hot‐rolled steel, there are several benefits of using cold‐formed steel (CFS) in these structures, such as lightness and less susceptibility to corrosion. The main disadvantage of using CFS in the steel beams is its connection to concrete, since the CFS members are thin and...

Some reinforced concrete (RC) structures requiring strengthening intervention are subjected to cyclic loads during their lifetime. To evaluate the effect of this kind of loading on the behavior of flexurally strengthened RC slabs with prestressed near‐surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminates, an experimental program fo...

This paper presents a new pre-fabricated lightweight slab system where the relatively high post-cracking tensile capacity of steel fibre reinforced concrete (SFRC) is combined with the high ductility and tensile strength of optimized shape profiles made by cold formed steel sheets for a synergetic result in terms of structural performance. The SFRC...

La investigación experimental ha demostrado el extraordinario potencial de la adición de fibras cortas a los materiales cementiceos, ya que mejoran significativamente el comportamiento de estructuras de hormigón en los estados límite de servicio y último. Para la simulación del comportamiento no lineal del material en estructuras de hormigón reforz...

Steel fibre-reinforced concrete (SFRC) is an emerging class of composite for construction. However, a reliable method to assess the flexural behaviour of SFRC structural member is in lack. An analytical technique is proposed for determining the moment-curvature response of concrete beams reinforced with steel fibres and longitudinal bars (R/SFRC me...

Even though the usage of Fiber-reinforced polymer (FRP) full confinement arrangement is a more reliable and efficient strengthening technique than a partially confining strategy, it might not be cost-effective in real cases of strengthening. Experimental researches have demonstrated that the confinement strengthening strategy is more effective for...

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 o...

Steel-fibre-reinforced concrete (SFRC) is a strain rate sensitive material and, therefore, its dynamic and static compressive behaviour can be significantly different. In the present study, the effect of loading rate on the compressive behaviour of SFRC with 1% hooked end steel fibres is experimentally investigated. During impact loading, an inerti...

Conventional concrete material shows relatively low ductility and energy dissipation capacity under high strain rate tensile loads. The use of steel fibers into concrete can significantly improve the tensile behavior of concrete subjected to high strain rate loads by fibers bridging the concrete crack surfaces, resulting in a high impact resistance...

The present study is dedicated to develop a new axial stress-strain model for FRP-based confinement strategies in case of FRP fully/partially confined circular concrete columns under axial compressive loading. For calculating axial stress versus axial strain curve, a new formulation as a function of concrete dilation response was suggested based on...

An analytical model to predict the torsional moment capacity and the type of failure of thin walled tubular reinforced concrete elements strengthened with near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminates is proposed. The model implements the thin walled space truss analogy, which forms the basis of current design codes, a...

Near surface mounted (NSM) strengthening technique, using fiber reinforced polymer (FRP) composite materials, is one of the most promising solutions for dealing with the deterioration problems of current reinforced concrete (RC) structures. However, intense research is still ongoing to keep improving this technique in the cases where its applicatio...

The present work has been developed in the scope of the research project ‘‘Easyfloor – Development of composite sandwich panels for building floor rehabilitation”. This project aims at developing a hybrid sandwich panel, constituting an alternative construction system to conventional floor solutions, mainly for buildings rehabilitation. The develop...

Coastal areas are an apprized environment by society that will continue to expand rapidly. Traditional coastal protection structures are commonly deployed to protect coastal areas endangered by natural extreme weather events. However, due to their limited efficiency and very high costs, more efficient and sustainable strategies to deal with coastal...

A exposição de estruturas de betão a temperaturas elevadas, como no caso de incêndio, conduz, entre outros, a uma degradação das propriedades mecânicas do material. Dependendo da temperatura e do tempo de exposição, esta ocorrência acidental potencia a ocorrência de fissuração e destacamento do betão – spalling (por vezes de forma explosiva), poden...

The use of recycled materials and industrial by-products as sustainable constituents of cement-based materials could be an environmentally and technically promising solution for application to structural elements. In the present work, the technical and environmental impact of using recycled steel fibers as an alternative to industrial steel fibers...

The present work assesses the potentialities of a new carbon fibre reinforced polymer (CFRP) bar, applied according to a hybrid technique for the flexural strengthening of cantilever type reinforced concrete (RC) structures, such as the case of RC balconies. The CFRP bar is formed by an inclined extremity that is inserted into a hole according to t...

In this paper, a new approach is proposed for predicting reaction force in simply supported steel fiber reinforced concrete (SFRC) beams under impact loading (drop weight test) considering the energy conservation approach. If SFRC beams completely fail under impact load, it can be found that the total reaction force is equal to force capacity of SF...

The superb performance of carbon fiber reinforced polymer (CFRP) composites as near surface mounted (NSM) reinforcement in strengthening solutions for structures is already well recognized. Due to their deficiencies in fire conditions, cement-based adhesives as an alternative to polymeric matrices are recently suggested as a solution in these syste...

The present work describes an integrated approach that leads to the development of a new model capable of describing the tensile behavior (mode I) of fiber reinforced concrete (FRC), considering the orientation of the fibers, the fibers segregation along the cross-section of the FRC members and the pullout constitutive model of each fiber bridging...

The strengthening intervention of RC structures often involves already cracked concrete. To evaluate the effect of the level of damage prior to the strengthening (pre-cracks) on the behavior of the flexurally strengthened RC slabs with prestressed NSM CFRP laminates, an experimental research was carried out. Two pre-cracking levels of damage were a...

Experimental research has confirmed that the usage of fiber reinforced polymer (FRP) composite materials can be a reliable solution to substantially improve axial and dilation behavior of confined concrete columns. In this regard, FRP partial confinement system is a good compromise from the cost competitiveness point of the view, while the applicat...

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...

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 wate...

In general, steel and concrete composite floors tend to present a reduced functional performance (considering thermal and acoustic conditions), due to their low mass and to the high conductivity of the steel elements. By including components with high thermal insulation capacity in these structural systems, it is possible to maintain the structure...

In recent past, the authors developed an innovative modular system for low rise building made by structural sandwich panels. This system was conceived with the focus on the rationalization of the construction process and on the thermal efficiency of the building. Thus, the precast panels comprise two outer Steel Fibre Reinforced Self-Compacting Con...

This paper presents a new technique based on dynamic X-ray radiography that can be used to assess fibre orientation during pouring of steel fibre reinforced cementitious composites. Synthetic examples were used to assess the suitability and robustness of the technique, which was shown to provide reliable measurements of fibre orientation even when...

This study is dedicated to the development of a generalized confinement model applicable to circular concrete columns confined by FRP full and partial confinement arrangements. To simulate the axial stress versus strain curve, a new strength model is proposed addressing the relation of axial stress and confinement pressure during axial loading, who...

Extreme wave value analysis under uncertainty scenarios was developed to estimate wave climate characteristics at 17 stations in southwestern European coast off the Iberian Peninsula. A comprehensive wave dataset downscaled with the Wave Watch III (WWIII) model by Meteogalicia under MarRisk Project was used considering results of models from the Co...

The main purpose of the present work is to study the mechanical behavior and durability performance of recycled steel fiber reinforced concrete (RSFRC) under a chloride environment. To this end, the effect of chloride attack on the load-carrying capacity of pre-cracked RSFRC round panels is investigated by performing round panel tests supported on...

A avaliação de soluções convencionais de defesa costeira ou a definição de soluções inovadoras requer a disponibilização de um conjunto de ferramentas que incluem a simulação da hidrodinâmica e morfodinâmica costeira e meios para a avaliação experimental. Contudo, todos os modelos de simulação destes fenómenos apresentam simplificações e limitações...

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...

This paper presents an experimental and numerical study aiming at 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. The sandwich panel, which was designed for the structural, thermal and acoustic refurbishment of building facade...

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...

An experimental program was carried out for assessing the performance of a hybrid solution composed by CFRP systems for the simultaneous flexural and shear strengthening of RC beams. CFRP laminates, applied according to NSM technique, are used for the flexural strengthening, while U-shape CFRP discrete strips of wet lay-up sheet, applied according...

The creation of new openings in masonry walls is a frequent intervention in existing buildings. Depending on their size and position, these interventions may cause a significant decrease of the wall's original in-plane strength and stiffness, thus compromising the building seismic resistance. Therefore, in masonry buildings, strengthening technique...

In this study, compression, bending and shear properties of the dry fibre reinforced concrete (FRC) were experimentally characterized at its early age. Considering the application of the developed FRC in prefabricated prestressed beams, three-point notched beam bending tests were executed to analyse the post-cracking flexural behaviour, and direct...

Concrete is a strain-rate sensitive material and shows relatively low ductility and energy dissipation capacity under high strain rate loads (HSRL) such as blast and impact, representative of terrorist attacks and accidents. Experimental research in the literature has evidenced that introducing steel fibers, into the concrete mixtures can significa...

Nowadays, existing masonry buildings are frequently modified to satisfy living demands. These modifications may require the addition of new windows or doors in walls of structural functionality. In engineering practice, such modifications are generally designed and verified for vertical loads while, for seismic loads, the changes in the walls’ stru...

This book gathers peer-reviewed contributions presented at the 3rd RILEM Spring Convention and Conference, held at Guimarães and hosted by the University of Minho, Portugal, on March 9-14, 2020. The theme of the Conference was “Ambitioning a Sustainable Future for Built Environment: comprehensive strategies for unprecedented challenges”, which was...

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 ded...

Experimental research has shown the extraordinary potential of the addition of short fibers to cement‐based materials by improving significantly the behavior of concrete structures for serviceability and ultimate limit states. Software based on the finite element method has been used for the simulation of the material nonlinear behavior of fiber‐re...

Despite the key role of thin-walled tubular reinforced concrete (RC) members in major critical infrastructure projects, for example, bridges, their torsional performance is still not well understood and the effectiveness of strengthening systems cannot be easily assessed, especially when using innovative strengthening materials. With a large part o...