Special Issue "Fiber Reinforced Polymers for Structural Strengthening"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: 3 July 2020.

Special Issue Editor

Assoc. Prof. Jose Sena-Cruz
Website
Guest Editor
Department of Civil Engineering, University of Minho, Portual
Interests: FRP materials and structures; durability and long-term behavior; testing; finite element analysis

Special Issue Information

Dear Colleagues,

The use of fiber reinforced polymers (FRP) in the construction sector mostly started in 1970–1980s, with several applications in all-composite and hybrid structures, internal reinforcement of new structures and internal/external strengthening of existing structures. Among different sectors, such aerospace, automotive, wind energy, marine and sporting goods, construction continues to be second largest market for composite materials. This achievement is intrinsically related to the research developed by different institutions and researchers worldwide. In spite of that, innovative structural solutions and unprecedented insights on the existing subjects are continually proposed for the composites construction sector. This Special Issue is mostly devoted to these subjects.

Assoc. Prof. Jose Sena-Cruz
Guest Editor

Manuscript Submission Information

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Keywords

  • FRP materials and structures
  • Struyctural Applications
  • Innovative solutions
  • Disruptive ideas/advanced contributions on the existing knowledge
  • Testing
  • Finite Element Analysis

Published Papers (4 papers)

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Research

Open AccessArticle
Post-Fire Characteristics of Concrete Beams Reinforced with Hybrid FRP Bars
Materials 2020, 13(5), 1248; https://doi.org/10.3390/ma13051248 - 10 Mar 2020
Abstract
One of the main concerns of experimental and numerical investigations regarding the behavior of fiber-reinforced polymer reinforced concrete (FRP-RC) members is their fire resistance to elevated temperatures and structural performance at and after fire exposure. However, the data currently available on the behavior [...] Read more.
One of the main concerns of experimental and numerical investigations regarding the behavior of fiber-reinforced polymer reinforced concrete (FRP-RC) members is their fire resistance to elevated temperatures and structural performance at and after fire exposure. However, the data currently available on the behavior of fiber-reinforced polymer (FRP) reinforced members related to elevated temperatures are scarce, specifically relating to the strength capacity of beams after being subjected to elevated temperatures. This paper investigates the residual strength capacity of beams strengthened internally with various (FRP) reinforcement types after being subjected to high temperatures, reflecting the conditions of a fire. The testing was made for concrete beams reinforced with three different types of FRP bars: (i) basalt-FRP (BFRP), (ii) hybrid FRP with carbon and basalt fibers (HFRP) and (iii) nano-hybrid FRP (nHFRP), with modification of the epoxy matrix of the rebar. Tested beams were first loaded at 50% of their ultimate strength capacity, then unloaded before being heated in a furnace and allowed to cool, and finally reloaded flexurally until failure. The results show an atypical behavior observed for HFRP bars and nHFRP bars reinforced beams, where after a certain temperature threshold the deflection began to decrease. The authors suggest that this phenomenon is connected with the thermal expansion coefficient of the carbon fibers present in HFRP and nHFRP bars and therefore creep can appear in those fibers, which causes an effect of “prestressing” of the beams. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers for Structural Strengthening)
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Open AccessArticle
Prediction of Deflection of Reinforced Concrete Beams Strengthened with Fiber Reinforced Polymer
Materials 2019, 12(9), 1367; https://doi.org/10.3390/ma12091367 - 26 Apr 2019
Cited by 2
Abstract
The article analyses the calculation of the deflection of reinforced concrete beams strengthened with fiber reinforced polymer. This paper specifically focuses on estimating deflection when the yielding of reinforcement is reached. The article proposes a simple method for calculating deflection that was compared [...] Read more.
The article analyses the calculation of the deflection of reinforced concrete beams strengthened with fiber reinforced polymer. This paper specifically focuses on estimating deflection when the yielding of reinforcement is reached. The article proposes a simple method for calculating deflection that was compared with the experimentally predicted deflection. The carried out comparison has showed that the proposed method is suitable not only for the strengthened beams but also for the reinforced concrete beams with a varying reinforcement ratio. The suggested calculation method is based on the effective moment of inertia, such as the one introduced in the ACI Committee 318 Building Code Requirement for Structural Concrete (ACI318). The development of deflection was divided into three stages, and equations for the effective moment of inertia were proposed considering separate stages. In addition, the put forward equations were modified attaching additional relative coefficients evaluating a change in the depth of the neutral axis. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers for Structural Strengthening)
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Open AccessFeature PaperArticle
Unified Theory for Flexural Strengthening of Masonry with Composites
Materials 2019, 12(4), 680; https://doi.org/10.3390/ma12040680 - 25 Feb 2019
Cited by 3
Abstract
Recent calamitous events have shown the fragility of the existing masonry buildings. Many of them are heritage structures, such as churches and monumental buildings. Therefore, optimized strengthening strategies are necessary. Experimental studies performed on masonry elements strengthened with composite systems have shown the [...] Read more.
Recent calamitous events have shown the fragility of the existing masonry buildings. Many of them are heritage structures, such as churches and monumental buildings. Therefore, optimized strengthening strategies are necessary. Experimental studies performed on masonry elements strengthened with composite systems have shown the performance of these materials. However, further development is necessary to optimize the intervention strategies. In fact, due to the lack of general validity models, the design is usually based on prescriptive approaches according to manufacturers’ broad instructions, often producing systems with low efficiency and overestimations of the amount of reinforcement. In this paper a generalized approach is proposed to assess the flexural behavior of masonry sections strengthened with composites. The proposed theory has allowed performance of a sensitivity analysis assessing the impact both of the mechanical parameters of masonry and of the strengthening system. In particular, the impact of several constitutive relationships of composites (linear, bilinear, or trilinear) have been evaluated in terms of ultimate behavior of the strengthened masonry. For strengthening systems more compatible with the masonry substrate, the form of the stress–strain relationship becomes a key aspect. For such cases, the modeling of the reinforcement plays a fundamental role and the form of the relationship is strongly correlated to the type of reinforcement selected, e.g., organic versus inorganic matrix. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers for Structural Strengthening)
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Open AccessFeature PaperArticle
Influence of Surface Preparation Method on the Bond Behavior of Externally Bonded CFRP Reinforcements in Concrete
Materials 2019, 12(3), 414; https://doi.org/10.3390/ma12030414 - 29 Jan 2019
Cited by 2
Abstract
In last decades significant investigation has been carried out in order to predict the bond strength of externally bonded reinforcement (EBR) systems with carbon fiber reinforced polymer (CFRP) materials in concrete and, as consequence of that, many analytical expressions can be found in [...] Read more.
In last decades significant investigation has been carried out in order to predict the bond strength of externally bonded reinforcement (EBR) systems with carbon fiber reinforced polymer (CFRP) materials in concrete and, as consequence of that, many analytical expressions can be found in the literature, including in standards. However, these expressions do not account for the influence of several parameters on bond behavior such as the type of surface preparation which is a mandatory and critical task in the strengthening application. The present work gives contributions to reduce this lack of knowledge. For this purpose, an experimental program composed of single-lap shear tests was carried out, the main parameters studied being: (i) the type of concrete surface preparation (i.e., grinding and sandblasting) and (ii) the bond length. Prior to the application of the EBR CFRP system, the roughness level provided by the different methods of surface preparation was characterized by a laser sensor. Test results revealed that sandblasting concrete surface preparation yielded higher values, in terms of maximum shear force and fracture energy. Finally, existing expressions in standards were upgraded in order to account for the concrete surface roughness level in the estimation of the bond strength. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers for Structural Strengthening)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Author:Christoph Czaderski
Affiliation:Empa - Swiss Federal Laboratories for Materials Science and Technology

Author: Gianpiero Lignola
Affiliation:University of Naples "Federico II", Italy

Author: João Ramôa Correia
Affiliation: Instituto Superior Técnico, Portugal

Author: Jose Sena-Cruz
Affiliation:University of Minho, Portugal

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