Bond shear stress-slip relationships for FRP-NSM systems at elevated temperature

In the last years Near Surface Mounted (NSM) reinforcement has mainly been applied at ambient temperature, to strengthen reinforced concrete (RC) beams with FRP (fibre reinforced polymer) materials. Thereby, FRP bars/strips are embedded inside the concrete section by means of grooves filled with adhesive. The behaviour of FRP-NSM strengthening systems at elevated temperature is signicantly influenced by the type of adhesive (e.g. cementitious grout is usually more stable than epoxy resin at high temperature). To characterize the FRP-NSM behaviour two steps are needed: 1) shear tests performed in order to determine the FRP-concrete interaction via bond stress-slip curves and 2) constitutive bond stress-slip relationships for use in structural design (analytical and numerical). Hereby, the bond behaviour is to be considered temperature dependent. During two experimental campaigns, double bond shear tests were performed in order to study the behaviour of FRP-NSM systems at elevated temperature using different types of adhesive, epoxy resin and cementitious grout respectively. The bond shear stress-slip curves are discussed including the effect of different types of adhesive. Simplified bond stress-slip relationships are proposed to model the FRP-concrete interaction at high temperature

Literature review on reinforced concrete members strengthened with FRP at room and elevated temperature

In the last 30 years, composite materials have been successfully applied as structural reinforcement to strengthen existing structures. The success of applying FRPs (Fibre Reinforced Polymers) for strengthening is due to their excellent mechanical properties and durability, their ease of application and the versatility of FRP strengthening systems. In particular Near Surface Mounted (NSM) reinforcement offers an interesting technology in terms of protection of the FRP from external influences compared to the Externally Bonded Reinforcement method (EBR). Based on a literature review, this paper discusses the structural performance in terms of FRP to concrete bond behaviour at room and elevated temperature. To understand and characterize the bond interaction, researchers conducted bond shear tests, though the lack of a standard test methodology makes comparison of results not always straight forward. As such, this study looks into bond influencing factors such as concrete type, adhesive type, FRP roughness, groove dimensions, glass transition temperature and coefficient of thermal expansion

Influence of bond stress-slip relationship on bond strength prediction

The study of the bond stress-slip relationship of FRP (fibre reinforced polymer) adhered to concrete has been a key point to understand the bond behaviour of externally bonded reinforcement (EBR) and near surface mounted (NSM) systems. Researchers have made an effort to determine bond-slip relationships through experimental and analytical/numerical methods, although they have not obtained univocal results. The area under the bond stress-slip relationship, representing the fracture energy, is one of the main parameters to make bond strength predictions. The fracture energy may be divided in two parts: elastic and softening contribution. These parts act both in a different way in predicting the failure load and the effective transfer length. In this paper the influence of the shape of the bond stress-slip relationship on the prediction of the bond strength and transfer length is investigated. Hereby, a comparison is made between the bilinear bond stress-slip relationship (linear elastic ascending branch-linear softening branch) and the elastic-exponential bond stress-slip relationship (linear elastic ascending branch-exponential softening branch)

Introduction to durability, sustainability and life cycle assessment of concrete structures : lecture notes of the DuRSAAM training course held September 2020

Concrete is one of the most popular building materials, making it also of concern when considering the environmental impact of the construction sector and the associated built environment. For example, the construction sector is responsible for over 35% of the EU’s waste generation, buildings account for 40% of energy consumed, construction activities require a vast amount of resources and cement, being a major component of concrete, accounts for 5 to 8% of the carbon emissions. Although concrete performs quite well in terms of environmental impact compared to other construction materials, its wide use makes sustainability of concrete crucial in minimizing the environmental impact, as can be characterized from life cycle assessments. Eco-friendly or circular concrete solutions are investigated widely in view of lowering environmental impact, while keeping the high technical performance expected from contemporary building solutions. The durability, sustainability and life cycle assessment of such emerging solutions is of considerable importance in the framework of the Green Deal or similar visions, and highlights the need for engineers skilled in these subjects. This also formed the motivation in organizing an introductory training course on durability, sustainability and life cycle assessment of concrete structures, which is at the basis of this eBook

Introduction to AAM technology : lecture notes of the DuRSAAM training course

This eBook has been made in the framework of the European Training Network on Durable, Reliable and Sustainable Structures with Alkali-Activated Materials (DuRSAAM), which organized a training course on AAM technology held at Karlsruhe Institute of Technology 27-29 January 2020. This open source book collects the lecture notes by the teachers of this training course and provides building professionals and stakeholders new insights on alkali-activated concrete as an emerging building technology

Development of a heavy metal sensing boat for automatic analysis in natural waters utilizing anodic stripping voltammetry

Altres ajuts: CERCA Programme/Generalitat de CatalunyaDetermination of the levels of heavy metal ions would support assessment of sources and pathways of water pollution. However, traditional spatial assessment by manual sampling and off-site detection in the laboratory is expensive and time-consuming and requires trained personnel. Aiming to fill the gap between on-site automatic approaches and laboratory techniques, we developed an autonomous sensing boat for on-site heavy metal detection using square-wave anodic stripping voltammetry. A fluidic sensing system was developed to integrate into the boat as the critical sensing component and could detect ≤1 μg/L Pb, ≤6 μg/L Cu, and ≤71 μg/L Cd simultaneously in the laboratory. Once its integration was completed, the autonomous sensing boat was tested in the field, demonstrating its ability to distinguish the highest concentration of Pb in an effluent of a galena-enriched mine compared to those at other sites in the stream (Osor Stream, Girona, Spain)

Identification and characterization of mature β-hexosaminidases associated with human placenta lysosomal membrane

International audienceβ-Hexosaminidase is a soluble glycohydrolase involved in glycoconjugate degradation into lysosomes, nevertheless its localization has also been described in cytosol and plasma membrane. Recently we demonstrated the presence of Hex associated to human fibroblast plasma membrane as mature form and functionally active towards GM2 ganglioside. In this study Hex was analysed in lysosomal membrane-enriched fraction, obtained by purification from highly purified human placenta lysosomes. Results demonstrate the presence of mature Hex associated to lysosomal membrane and displaying, as the plasma membrane (PM) associated form, an acidic optimum pH. When subjected to carbonate extraction, the enzyme behave as a peripheral membrane protein, while Triton X-114 phase separation confirmed its partial hydrophilic nature, characteristics that are in common with the PM-associated Hex. Moreover 2D electrophoresis indicated a slight difference in pI of β-subunits in the membrane and the soluble forms of the lysosomal Hex. These data reveal a new aspect of the Hex biology and suggest that a fully processed membrane-associated form of Hex is translocated from the lysosomal to the plasma membrane by an as yet unknown mechanism. We present a testable hypothesis that at the cell surface Hex changes the composition of glycoconjugates that are known to be involved in intercellular communication and signaling