ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • 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 485 Abstracts search results

Document: 

SP-348_06

Date: 

March 1, 2021

Author(s):

Ping (Philip) Jiang, Ron McDonel

Publication:

Symposium Papers

Volume:

348

Abstract:

A more than 50-year old Steam Turbine/Generator (STG) table-top concrete foundation was retrofitted to support a new STG/Condenser unit. This new machine unit is set on a sub skid with spring/damper assemblies underneath and located on existing concrete table top columns. This paper presents a case study of the seismic design and evaluations of the existing foundation structure that were performed to assess and qualify the structure’s service and strength capabilities. Based on these evaluations, modifications to the existing STG foundation were minimized allowing the cost effective reuse of the existing foundation resulting in significant savings for the overall installed cost of the project.


Document: 

SP-345_06

Date: 

February 1, 2021

Author(s):

Marco Carlo Rampini, Giulio Zani, Matteo Colombo and Marco di Prisco

Publication:

Symposium Papers

Volume:

345

Abstract:

Fabric-reinforced cementitious matrix (FRCM) composites are promising structural materials representing the extension of textile reinforced concrete (TRC) technology to repairing applications. Recent experiences have proven the ability of FRCMs to increase the mechanical performances of existing elements, ensuring economic and environmental sustainability. Since FRCM composites are generally employed in the form of thin externally bonded layers, one of the main advantages is the ability to improve the overall energy absorption capacity, weakly impacting the structural dead weights and the structural stiffness and, as a direct consequence, the inertial force distributions activated by seismic events. In the framework of new regulatory initiatives, the paper aims at proposing simplified numerical approaches for the structural design of retrofitting interventions on existing reinforced concrete structures. To this purpose, the research is addressed at two main levels: i) the material level is investigated on the uniaxial tensile response of FRCM composites, modeled by means of well-established numerical approaches; and ii) the macro-scale level is evaluated and modeled on a double edge wedge splitting (DEWS) specimen, consisting of an under-reinforced concrete substrate retrofitted with two outer FRCM composites. This novel experimental technique, originally introduced to investigate the fracture behavior of fiber-reinforced concrete, allows transferring substrate tensile stresses to the retrofitting layers by means of the sole chemo-mechanical adhesion, allowing to investigate the FRCM delamination and cracking phenomena occurring in the notched ligament zone. It is believed that the analysis of the experimental results, assisted by simplified and advanced non-linear numerical approaches, may represent an effective starting point for the derivation of robust design-oriented models.


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_47

Date: 

October 1, 2020

Author(s):

Lucchini, S.S.; Facconi, L.; Minelli, F.; Plizzari, G.A.

Publication:

Symposium Papers

Volume:

343

Abstract:

The use of mortar coating reinforced only with randomly diffused steel fibers represents an effective technique for seismic retrofitting of masonry buildings. The present work aims at proving the effectiveness of that technique by testing a full-scale two-story hollow clay block masonry building subjected to a quasi-static cyclic lateral loading. The experimental program includes two tests involving the same building. The first test performed on the building without coating is carried out to pre-damage masonry in order to simulate the effects of a seismic action significant for ultimate conditions. The second test is performed to assess the behavior of the pre-damaged building after retrofitting. The paper presents the main properties and details of both the test building and the proposed retrofitting technique. As the test on the retrofitted specimen is still ongoing, only the main results concerning the unstrengthened building are reported and discussed. To predict the response of the two experimental tests, 3D non-linear finite element simulations have been carried out and presented in the last section of the paper. The latter includes the comparison between the numerical prediction and the available experimental results.


Document: 

SP-343_33

Date: 

October 1, 2020

Author(s):

Ranjbarian, M.; Mechtcherine, V.

Publication:

Symposium Papers

Volume:

343

Abstract:

The structures subject to dynamic loading demand more ductile materials to prevent catastrophic failure. The results of investigations on strain-hardening cement-based composites (SHCCs) distinguished this group of materials – due to their highly ductile behaviour – as a suitable alternative for structures with high resistance against seismic, impact and cyclic loadings. While mechanical properties of SHCC are determined mostly by bridging behaviour of dispersed fibres crossing cracks and properties of fibre-matrix interface, the dependency of these mechanisms on the loading regime is pronounced. Specifically, under cyclic loading, the number of cycles to failure decreases dramatically when SHCC is subject to alternating tension-compression regime. Degradation of fibres compressed between the crack faces and deterioration of their bridging capacity are responsible for such early failure and necessitate further investigations at the micro level. The article at hand presents the influence of loading history in cyclic tension-compression regime on the bridging capacity of the single PVA microfibre embedded in cementitious matrix. A novel double-sided single fibre pull-out setup is used for the experimental investigations. First the test setup, material composition and testing procedure are explained. Next, the results of double-sided pull-out specimens, tested under monotonic and cyclic tension-compression regimes, are discussed. It is shown that the deterioration of fibre bridging capacity can be assessed by applying cyclic loading in post-cracking stage, followed by pulling the fibre out of the matrix. Possibility of a change in pull-out behaviour of PVA microfibre from “fibre rupture” to “fibre pullout”, also a change of behaviour in post debonding regime from “hardening” to “softening” are also observed. Eventually, the results of microscopic analysis are presented and discussed, which show the specific phenomena responsible for changes in pull-out behaviour.


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.