Source Selection Among Information Seekers: Ideals and Realities

In a study examining the information behavior of 9 individuals over 10 weeks in daily life contexts, participants were asked to identify ideal sources of help for the questions and issues they faced. The data show how people’s expectation of the usefulness of information sources varies by the information seeker’s gender, and source characteristics such as accessibility, trustworthiness, and reliability. Usefulness of sources has both cognitive and affective aspects. Further, discrepancies between participants\u27 stated ideals, and the sources actually used, are analyzed. The study results suggest ways to encourage use of formal information systems and services

Intra-individual Information Behaviour in Daily Life

This study addresses the lack of attention in the literature paid to detailed analysis of individuals information behavior in daily life contexts. In particular, the study characterizes one individuals information behavior across different daily life situations, to seek behavioral patterns that might be associated with various aspects of each information seeking situation. Data was collected through participant diaries, and subsequent oral interviews. This study reports on source selection, and influence of various aspects of the situations described. These aspects were identified from analysis of the interview transcripts, and include time constraints and pressures, motivation for the information need, context of the information need, type of initiating event, location of information seeking activities, intended application of the information found, and source type

Thermo-mechanical properties of commercially available epoxy resins for structural applications

Externally bonded (EB) or Near-Surface-Mounted (NSM) composite reinforcements are often bonded to a cementitious substrate by means of commercially available epoxies. These twocomponent- resins are generally ‘cold-curing’ (at room temperature), having however the ability to cure faster under elevated temperatures. One application requesting such an accelerated curing process is the gradient anchorage for strengthening of concrete structures with prestressed CFRP laminates, based on a purely concrete/epoxy/CFRP connection without any mechanical devices. This paper resumes the investigation on several crucial thermo-mechanical parameters of different epoxy resins, such as glass-transition temperatures, directional tensile strength and elastic modulus. It is for instance demonstrated that an accelerated curing process or an increasing specimen age implicate a higher glass transition temperature. Strength and stiffness development is faster in case high temperatures are applied; the final values with growing age however are below the ones for specimens cured only at room temperature. Initial mixing under vacuum on the other hand induces higher strength and stiffness values. Eventually, it is shown that an accelerated curing of a cold-curing epoxy increases the porosity of the latter, possibly implying durability issues

Structural strengthening with prestressed CFRP strips with gradient anchorage

ManuscriptThis paper presents the principle and the application of an innovative anchorage technique for prestressed carbon fiber–reinforced polymer (CFRP) strips in structural strengthening. Additionally, large-scale static loading tests of retrofitted concrete beams are shown. The gradient anchorage, based on the adhesive’s ability to undergo accelerated curing at high temperatures, consists of a purely concrete-adhesive strip connection without any mechanical devices, such as bolts or plates. In a first step, this study summarizes anchorage techniques presented in the literature and introduces the basic principles of the new method as well as the necessary components. In a second step, an application on a full-scale RC beam is explained in detail. A commercially-available CFRP strip is prestressed up to 0.6% prestrain and subsequently anchored by sequential epoxy-curing and force-releasing steps at both strip ends. Furthermore, uniaxial tensile tests on the epoxy adhesive and the CFRP strip are used for material characterization and to demonstrate the reinforcing materials’ integrity after the heating process. It appeared that prestress losses during the anchoring phase are negligible. The method allows much faster installation than conventional mechanical techniques and increases durability because no permanent steel elements are necessary. The material tests indicate no damage in the reinforcing CFRP strip as well as a sufficiently fast strength development of the adhesive after accelerated curing. Static loading tests on strengthened large-scale RC beams are presented and show the efficiency of a prestressed CFRP strip with gradient anchorage as a retrofitting technique. Finally, first long-term measurements over 13 years on a prestressed strip bonded to a concrete plate revealed small prestrain losses.The authors want to thank the Swiss innovation promotion agency (CTI project No. 10493.2 PFIW-IW) as well as the industrial partner S&P Clever Reinforcement from Switzerland for their financial support. Furthermore, the staff of the Structural Engineering Testing Laboratory at Empa as well as from University of Minho is kindly thanked for their contributions to the experimental investigations. Particular acknowledgements are expressed to Milos Dimic for the CAD Inventor drawings as well as Professor Fernando Castro from the Department of Mechanical Engineering of the University of Minho for the SEM images. The second author would like to thank the Fundaao para a Ciencia e a Tecnologia (Foundation for the Science and Technology/Portugal), grant SFRH/BSAB/1220/2011 for providing financial support in the context of his sabbatical year

Preliminary study on the influence of fibre orientation in fibre reinforced mortars

U radu se obrađuje utjecaj čeličnih vlakana u mikroarmiranim mortovima. Uzorci morta u svježem stanju, s nasumično raspoređenim vlaknima su smješteni u spiralnu zavojnicu i izloženi elektromagnetskskom polju u cilju postizanja usmjerenosti vlakana. Lokacija i orijentacija vlakana je određena rengenskom snimkom. Provedena su ispitivanja čvrstoće na savijanje uz kontrolu progiba ISC sustavom (engl. Digital Image Correlation System - ICS). S obzirom na orijentaciju vlakana, rezultati su pokazali poboljšanu disipaciju energije i veću energiju pri lomu kod uzoraka s usmjerenim vlaknima.The influence of steel fibres in fibre reinforced mortars is considered in the paper. Fresh mortar samples with randomly distributed fibres are placed in a spiral coil and exposed to electromagnetic filed so as to achieve orientation of fibres. The location and orientation of fibres is defined by x-ray images. The bending strength testing with deflection checking using the ICS system (Digital Image Correlation System) is conducted. Considering the fibre orientation and load applied, the results exhibit better energy dissipation and greater energy at fracture in case of samples with oriented fibres

Flexural strengthening of RC slabs with prestressed CFRP strips: serviceability and ultimate load state behavior

O presente trabalho pretende contribuir para o conhecimento da técnica EBR (Externally Bonded Reinforcement) usando laminados de CFRP (Carbon Fiber-Reinforced Polymer) pré-esforçados no reforço à flexão de estruturas de betão, sob condições de serviço (SLS) e estado limite último (ULS). Para tal, foi desenvolvido um programa experimental composto por 8 lajes ensaiadas até à rotura. Duas lajes foram usadas como de referência; 5 reforçadas com laminados de EBR/CFRP pré-esforçados; finalmente, 1 laje reforçada com um laminado EBR/CFRP. Dois sistemas distintos de ancoragem foram estudados: MA (Mechanical Anchorage) e GA (Gradient Anchorage). O efeito da largura e espessura do laminado foi também estudado. A performance dos protótipos é criticamente analisada ao nível dos SLS e ULS.The present work intends to contribute to the knowledge of Externally Bonded Reinforcement (EBR) technique using prestressed Carbon Fiber-Reinforced Polymer laminates (CFRP) to strengthen concrete structures in flexure, at both serviceability (SLS) and ultimate load levels (ULS). For that purpose, an experimental program was carried out with 8 slabs monotonically tested under displacement control up to failure. Two slabs were used as reference specimens (unstrengthened); 5 slabs were strengthened with prestressed EBR CFRP laminates; finally, 1 slab was strengthened EBR CFRP laminates without being prestressed. To fix the ends of the prestressed CFRP laminates two different anchorage systems were used: Mechanical Anchorage (MA) and Gradient Anchorage (GA). The effect of the width and thickness of the CFRP laminate were also studied. The observed performance of the tested slabs is critically analyzed in terms of SLS and ULS aspects

Short and long-term behaviour of RC slabs strengthened with prestressed CFRP laminate strips

In the context of strengthening reinforced concrete (RC) structures with fiber reinforced polymer (FRP) materials, the externally bonded reinforcement (EBR) technique is the most widely used strategy. By prestressing the FRP materials attached to the concrete substrate, the advantages of external prestressing and of the EBR technique are combined. The solutions adopting carbon FRP (CFRP) laminates have been mostly used. Special end-anchorage systems are required at the ends of the prestressed CFRP laminate to transfer the high shear stresses developed from the FRP to concrete, in order to avoid a premature FRP peeling-off failure. From all the proposed systems, two of them have been prevailed, mainly: the mechanical anchorage (MA) fixed to the ends of the FRP reinforcement and the gradient anchorage (GA). The present work investigates the short and long-term behaviour, including the durability issues, of reinforced concrete (RC) slabs strengthened with prestressed CFRP strips according the EBR technique. Two different anchorage systems were studied: (i) MA and (ii) GA. The experimental program carried out included of the effects of environmental actions such as water, water with chlorides and wet-dry cycles on the global performance of these slabs. This paper presents the general description of the experimental program, the analysis of the main results, as well as the retained conclusions.This work is supported by FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects FRPreDur - FCOMP 01-0124-FEDER-028865 (PTDC/ECMEST/2424/2012) and FRPLongDur - POCI-01-0145- FEDER-016900 (FCT PTDC/ECM-EST/1282/2014) and partly financed by the project POCI-01-0145- FEDER-007633. The authors thank all the companies that supported and contributed for the development of this study, mainly: S&P Clever Reinforcement Ibérica, S&P Clever Reinforcement Company (Switzerland), Tecnipor, Vialam, Hilti, Artcanter and Nova Europa. The second author also wishes to acknowledge the grant SFRH/BD/99309/2013 provided by FCT. Finally, this paper is dedicated to Tiago Teixeira (1988–2015), former doctoral student at the ISISE R&D Research Centre at the University of Minho and team member of the project FRPreDur.info:eu-repo/semantics/publishedVersio

Flexural strengthening of RC slabs with prestressed CFRP strips using different anchorage systems

In the field of flexural strengthening of concrete structures the Externally Bonded Reinforcement (EBR) technique using carbon fiber-reinforced polymers (CFRP) is commonly used. This technique offers several structural advantages when the CFRP material is prestressed. One of the critical aspects of a prestressing technique is the type of end anchorage. Two systems are investigated in the present paper: the metallic anchorage elements fixed to the ends of the FRP reinforcement and the gradient anchorage. In order to assess the performance of these two systems, an experimental program was carried out. In addition to the anchorage systems, the cross-section geometry of the CFRP strip was also included in this study. Eight slabs were monotonically tested under displacement control up to failure by using a four-point bending test configuration. The observed performance of the tested slabs is critically analyzed.Fundação para a Ciência e a Tecnologia (FCT

Reforço à flexão de lajes de betão armado com laminados de CFRP pré-esforçados usando distintos métodos de ancoragem

A utilização de laminados de CFRP (Carbon Fiber-Reinforced Polymers) segundo a técnica EBR (Externally Bonded Reinforcement) tem vindo a constituir uma prática comum no reforço de estruturas de betão armado à flexão devido às enumeras vantagens que os materiais compósitos apresentam. O uso de CFRP pré-esforçados acumula as vantagens da técnica EBR com as do pré-esforço externo. Neste contexto, o presente trabalho tem como objetivo principal contribuir para o conhecimento de dois sistemas de ancoragem de laminados de CFRP pré-esforçados: (i) o sistema com recurso a ancoragens mecânicas e (ii) o sistema de ancoragem do gradiente da força. Para o efeito, foi realizado um programa experimental composto por doze lajes reforçadas à flexão com CFRP. Além do tipo de sistema de ancoragem, foram também estudados outros fatores que influenciam o sistema de reforço, tais como: sistema passivo vs. ativo, a largura (50 mm e 80 mm) e a espessura (1.2 mm e 1.4 mm) do laminado de CFRP e a influência da geometria da laje (2600 mm e 2200 mm de comprimento). O programa experimental é descrito em detalhe e os resultados obtidos são apresentados e analisados de forma detalhada.Este trabalho é apoiado pelo FEDER, através do Programa Operacional Fatores de Competividade – COMPETE e fundos nacionais, através da FCT – Fundação para a Ciência e Tecnologia sob o projeto FRPreDur - PTDC/ECM-EST/2424/2012. Os autores gostariam também de agradecer a todas as empresas que estão envolvidas e têm contribuído para o desenvolvimento do projeto FRPreDur, nomeadamente: S&P Clever Reinforcement Ibérica Lda, S&P Clever Reinforcement Company (Switzerland), Tecnipor - Gomes & Taveira Lda., Vialam – Indústrias Metalúrgicas e Metalomecânicas, Lda., Hilti Portugal - Produtos e Serviços, Lda. O primeiro autor deseja também agradecer a bolsa SFRH/BD/98309/2013, atribuída pela FCT. Este trabalho é dedicado a Tiago Teixeira (1988-2015), antigo aluno de doutoramento da Unidade de Investigação ISISE e membro do projeto FRPreDur.info:eu-repo/semantics/publishedVersio

Mechanical performance of cold-curing epoxy adhesives after different mixing and curing procedures

This paper presents strength, stiffness, and porosity characteristics of commercially available cold-curing epoxy adhesives for structural engineering applications in the field of externally bonded and/or near-surface mounted composite strip reinforcements. Depending on specific requirements, accelerated curing of the adhesive under high temperatures might be necessary. Experimental investigations aimed at assessing the possible differences in strength and stiffness between samples cured at elevated temperatures for a defined time span and the ones cured at room temperature. It could be demonstrated that for the same specimen age, nominal tensile strength and stiffness are lower after an initial accelerated curing process at elevated temperatures. Furthermore, it could be shown that the specimens after an accelerated curing at elevated temperatures exhibited an increased porosity. The development of a numerical code for image analysis allowed a detailed inspection of several fracture surfaces and subsequently to assess the level of decrease in available cross-section due to an increased overall porosity. Cross-section area losses in the range of 10–15% compared to the reference specimens could be deduced. The subsequent derivation of the actual tensile strength exhibits smaller differences between the room and high temperature exposed specimens while curing. Regardless of the short-term material strength, the observed porosity might be subject of important durability issues on a long-term and needs further investigation.FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects FRPreDur FCOMP- 01-0124-FEDER-028865 (FCT no. PTDC/ECM-EST/2424/2012)The authors want to express their gratitude to Max Heusser and Milos Dimic (Empa, CH) for their assistance in the experimental investigation. Marcel Rees, Iurii Burda and Andrea Battisti (Empa, CH) are kindly acknowledged for their assistance with the vacuum mixer and the sample preparation for porosity assessment. Eventually, Esther Strub (Empa, CH) is acknowledged for the instructions about the miscroscope utilization. Distributors S&P Clever Reinforcement AG (CH) and Sika (CH) are also acknowledged for their material provision. This work is also supported by FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects FRPreDur FCOMP- 01-0124-FEDER-028865 (FCT no. PTDC/ECM-EST/2424/2012)