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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 1043 Abstracts search results

Document: 

SP343

Date: 

November 3, 2020

Author(s):

fib and ACI

Publication:

Symposium Papers

Volume:

343

Abstract:

The first international FRC workshop supported by RILEM and ACI was held in Bergamo (Italy) in 2004. At that time, a lack of specific building codes and standards was identified as the main inhibitor to the application of this technology in engineering practice. The workshop aim was placed on the identification of applications, guidelines, and research needs in order for this advanced technology to be transferred to professional practice. The second international FRC workshop, held in Montreal (Canada) in 2014, was the first ACI-fib joint technical event. Many of the objectives identified in 2004 had been achieved by various groups of researchers who shared a common interest in extending the application of FRC materials into the realm of structural engineering and design. The aim of the workshop was to provide the State-of-the-Art on the recent progress that had been made in term of specifications and actual applications for buildings, underground structures, and bridge projects worldwide. The rapid development of codes, the introduction of new materials and the growing interest of the construction industry suggested presenting this forum at closer intervals. In this context, the third international FRC workshop was held in Desenzano (Italy), four years after Montreal. In this first ACI-fib-RILEM joint technical event, the maturity gained through the recent technological developments and large-scale applications were used to show the acceptability of the concrete design using various fibre compositions. The growing interests of civil infrastructure owners in ultra-high-performance fibre-reinforced concrete (UHPFRC) and synthetic fibres in structural applications bring new challenges in terms of concrete technology and design recommendations. In such a short period of time, we have witnessed the proliferation of the use of fibres as structural reinforcement in various applications such as industrial floors, elevated slabs, precast tunnel lining sections, foundations, as well as bridge decks. We are now moving towards addressing many durability-based design requirements by the use of fibres, as well as the general serviceability-based design. However, the possibility of having a residual tensile strength after cracking of the concrete matrix requires a new conceptual approach for a proper design of FRC structural elements. With such a perspective in mind, the aim of FRC2018 workshop was to provide the State-of-the-Art on the recent progress in terms of specifications development, actual applications, and to expose users and researchers to the challenges in the design and construction of a wide variety of structural applications. Considering that at the time of the first workshop, in 2004, no structural codes were available on FRC, we have to recognize the enormous work done by researchers all over the world, who have presented at many FRC events, and convinced code bodies to include FRC among the reliable alternatives for structural applications. This will allow engineers to increasingly utilize FRC with confidence for designing safe and durable structures. Many presentations also clearly showed that FRC is a promising material for efficient rehabilitation of existing infrastructure in a broad spectrum of repair applications. These cases range from sustained gravity loads to harsh environmental conditions and seismic applications, which are some of the broadest ranges of applications in Civil Engineering. The workshop was attended by researchers, designers, owner and government representatives as well as participants from the construction and fibre industries. The presence of people with different expertise provided a unique opportunity to share knowledge and promote collaborative efforts. These interactions are essential for the common goal of making better and sustainable constructions in the near future. The workshop was attended by about 150 participants coming from 30 countries. Researchers from all the continents participated in the workshop, including 24 Ph.D. students, who brought their enthusiasm in FRC structural applications. For this reason, the workshop Co-chairs sincerely thank all the enterprises that sponsored this event. They also extend their appreciation for the support provided by the industry over the last 30 years which allowed research centers to study FRC materials and their properties, and develop applications to making its use more routine and accepted throughout the world. Their important contribution has been essential for moving the knowledge base forward. Finally, we appreciate the enormous support received from all three sponsoring organizations of ACI, fib and Rilem and look forward to paving the path for future collaborations in various areas of common interest so that the developmental work and implementation of new specifications and design procedures can be expedited internationally. June 2018 Bruno Massicotte, Fausto Minelli, Barzin Mobasher, Giovanni Plizzari


Document: 

SP-343_13

Date: 

October 1, 2020

Author(s):

De Smedt, M.; De Wilder, K.; Anastasopoulos, D.; Reynders, E. ; De Roeck, G.; Vandewalle, L.

Publication:

Symposium Papers

Volume:

343

Abstract:

This paper presents the experimental results of prestressed steel fibre reinforced concrete (SFRC) beams and it compares analytical model predictions with these results. Six beams were subjected to a force-controlled four-point bending test until failure. The three investigated parameters were the fibre dosage, the amount of prestressing force and the presence of shear reinforcement. During the test, failure mode and load, as well as deformations, displacements and cracking pattern properties were observed by means of conventional measurement devices and advanced optical techniques, including Bragg grated optical fibres and digital image correlation technique. Additionally, material properties were determined according to standardized European tests. The experimental results were compared to analytical predictions according to shear design equations in Model Code 2010. For the six beams, an average experimental-to-predicted failure load ratio of 1.43 was found with a coefficient of variation of 7.2%. Furthermore, four other analytical models for shear design of SFRC are investigated, namely DRAMIX Guideline, RILEM TC 162-TDF sigmaepsilon method, CNR-DT 204/2006 model and a model proposed by Soetens. All models underestimate the shear capacity of prestressed SFRC beams. The underestimation increases for a higher prestress level, whereas the correlation with the fibre dosage varies within the models.


Document: 

SP-343_12

Date: 

October 1, 2020

Author(s):

Barros, J.A.O.; Foster, S.J.

Publication:

Symposium Papers

Volume:

343

Abstract:

For the development of reliable physical-mechanical models for predicting the behaviour of fibre reinforced concrete structures at service and strength limit conditions, constitutive models simulating comprehensibly the governing phenomena must be used. In this context, simulating the post-cracking mechanisms of the fibres, and their symbiotic relationship with the cementitious matrix that surrounds them, is required for the development of realistic modelling approaches that accurately represent empirical observations. Several experimental test setups and inverse analysis procedures have been proposed to derive the fundamental stress-crack width ( –w) law, but a consensus still does not exists on the best strategy for its determination. In structures governed by shear, fibre reinforcement increases the stiffness and shear stress transfer across a crack, but a methodology to capture the contribution of fibres in this regards is challenging. To overcome this, a clear strategy is needed in deriving relationships that simulate fibre reinforcement mechanisms in the mobilized fracture modes and, also, develop design approaches capable of capturing the relevant contributions of the fibres. This study firstly reviews current inverse analysis models used to describe the tensile (Model I fracture) relationship for FRC and, secondly, discusses a newly proposed model, referred to as the integrated shear model (ISM). The ISM is developed from mesoscale observations from gamma- and X-ray imaging on FRC elements under Modes I and II fracture conditions. The resulting model is compared to test data reported in the literature and a good correlation is observed.


Document: 

SP-343_10

Date: 

October 1, 2020

Author(s):

Ortiz-Navas, F.; Scaroni, L.; Navarro-Gregori, J.; Serna-Ros, P.

Publication:

Symposium Papers

Volume:

343

Abstract:

Shear transfer mechanisms in fibre-reinforced concrete (FRC) have been studied by many authors based on push-off specimens. However, only few studies have used pre-cracked pushoff specimens to examine the real shear and normal stresses transferred through the crack. In this paper it is presented the experimental results of twenty-one pre-cracked push-off specimens tested under direct shear. Specimens were manufactured using plain concrete (PC), polypropylene fibre-reinforced concrete (PFRC), and steel fibre reinforced concrete (SFRC). In PFRC and SFRC specimens, fibre was dosed in 10kg/m3 and 30kg/m3 respectively. Nevertheless, both types of dosages were selected in order to provide similar post-cracking behaviour to the specimens. Five types of pre-crack openings were set up (W = 0, 0.25, 0.50, 0.75 and 1.0 mm) by an external steel frame system that confined the specimens during the tests. Afterwards, pre-cracked specimens were tested under direct shear where the crack kinematic (opening and slip displacements) as well as stresses (shear and normal) were recording during the tests. Finally, a comparison of behaviour between PC, SFRC and PFRC is done. Experimental results show the ability of both fibres to increase shear stress as well as shear stiffness in FRC specimens compared to PC ones. Moreover, it is evidenced that both type of fibres provided similar shear improvements despite of being different in material and shape.


Document: 

SP-343_08

Date: 

October 1, 2020

Author(s):

Chelha, F.; Alam, S. Y.; Bendimerad, A.Z.; Loukili, A.

Publication:

Symposium Papers

Volume:

343

Abstract:

Self-compacting mortars and concretes for horizontal structures are cementitious mixtures that are both fluid and homogeneous, with the particularity of flowing under the effect of their own weight. Thanks to their homogeneous texture they offer the possibility of achieving good quality of finishing and many such advantages become the reason for their applications especially in slabs and floors. However, self-compacting mortars or concretes show considerable shrinkage and cracking problems when used in floors and slabs (Weiss et al., 1998). Because of their large moisture exchange surfaces, the floor screeds are subjected to significant drying effects and in particular plastic shrinkage. If the movements are restrained, the risk of cracking is high. In this respect the use of fibers is a good alternative to using reinforcement bars and welded wire mesh. Indeed on site a clear decrease in cracking caused mainly by the shrinkage can be observed as soon as the fibers are incorporated in the screed. This study is conducted to demonstrate the effectiveness and the effects of glass fibers on the control of cracking phenomena due to shrinkage by determining their mechanisms of action at young age. The study is carried out in two parts: Firstly, free shrinkage behavior is analyzed in the fiber reinforced floor screed. Secondly, the restrained behavior at young ages using recently developed uni-axial tensile testing machine is investigated.


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