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Home > Publications > 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.
Showing 1-5 of 1866 Abstracts search results
October 1, 2022
Gianni Blasi, Daniele Perrone, and Maria Antonietta Aiello
The damage to infill walls caused by earthquakes often represents a major safety issue in reinforced concrete buildings. For this reason, masonry infill retrofit is increasingly adopted in high seismic hazard countries to increase the in-plane capacity of the walls and to avoid out-of-plane failure modes. On the other hand, the infill strengthening might significantly modify the seismic performance of the buildings, influencing the failure modes and the global ductility. Recent studies assessed that the enhancement of the in-plane strength of the infill can cause brittle failure in lightly shear reinforced columns. In this study, non-linear analyses are performed on reinforced concrete framed buildings to investigate the influence of the infill strengthening and column shear reinforcement on seismic performance. A three-dimensional numerical model is developed to assess the seismic capacity and the failure modes depending on the frame’s and infill’s details. The proposed study aims to encourage a smart design of the infill retrofit, geared toward a global performance enhancement rather than the mere strengthening of the single infill wall.
Wael Zatar, Hai Nguyen, and Hien Nghiem
Fiber-reinforced polymer (FRP) materials provide an excellent alternative for shear, flexure, and confinement retrofitting of deteriorated infrastructure. Despite the advanced technology employed in fabricating FRP materials, the monitoring and quality control of the FRP installation still present a challenge. For externally bonded FRP-rehabilitated structures, the existence of undesirable defects, including surface voids and debonding, on the concrete surface should be evaluated, as these defects would adversely affect the durability and capacity of the FRP-rehabilitated structures. Nondestructive testing has the potential to provide a fast and precise means to assess these FRP rehabilitated structures. This paper presents an experimental and theoretical investigation of the use of ground-penetrating radar (GPR) and infrared tomography (IRT) methods to evaluate reinforced-concrete (RC) slabs externally bonded with glass fiber-reinforced polymer (GFRP). Four externally bonded GFRP RC slab specimens were fabricated. Surface voids, interfacial debonding, and vertical cracks were artificially created on the concrete surface of the RC slabs. Test variables include the location and size of surface voids, interfacial debonding, and diameter of steel reinforcement. Improved two-dimensional and three-dimensional image reconstruction method, using the synthetic aperture focusing technique (SAFT), was established to effectively interpret the GPR test data. The results showed that an in-house developed software, that employed the enhanced image reconstruction technique, provided sharp and high-resolution images of the GFRP-retrofitted RC slabs in comparison to those images obtained from the device’s original software. The data suggests that the GPR testing could effectively be employed to accurately determine the size and location of the artificial voids as well as the spacing of the steel reinforcement. The GPR, however, could not well predict the debonding and concrete cracking, as the GPR signals were corrupted because of the direct wave and coupling effect of the antennae and background noise. Results obtained from the IRT testing showed that this technique can detect and locate near-surface defects including surface voids, interfacial debonding, and cracking with acceptable accuracy. The study suggests the combined use of the GPR and IRT imaging to accurately detect possible internal defects of FRP-rehabilitated concrete structures.
Mahmut Ekenel, Hossein Roghani, Francisco De Caso y Basalo, and Antonio Nanni
Advances in technology have opened doors for building construction with new materials that are lightweight, efficient, noncorrosive, and reliable in terms of durability without a sacrifice in strength and performance. One of these technologies is the use of FRP bars and meshes in concrete members as internal reinforcement. Although FRP bars as structural reinforcement in concrete members have been successfully utilized in building and bridge projects (i.e., slabs, beams, etc.) for the past three decades; recently, there has been an interest in using FRP bars and meshes as secondary reinforcement for non-structural concrete members such as plain concrete footings, concrete slabs-on-ground, and plain concrete walls in lieu of code-compliant conventional temperature and shrinkage steel reinforcement. Because the use of FRP bars and meshes as secondary reinforcement is not within the provisions of the International Building Code (IBC), the predominant building code in the United States, an acceptance criterion (AC521) has been developed under IBC Section 104.11. This paper explains the requirements of AC521, and how FRP bars and meshes as secondary reinforcement of nonstructural concrete members are evaluated to show compliance with the provisions of the IBC.
Fadi Oudah and Adam Hassan
The use of fiber-reinforced polymer (FRP) in structural engineering applications is challenged by the need for increasing the market competitiveness of FRP as compared with conventional reinforcing materials. The market competitiveness of FRP can be enhanced by optimizing the design provisions of FRP-reinforced concrete elements in relevant design codes and standards using structural reliability methods. The objectives of this research are to (1) evaluate and compare the reliability of compression-controlled flexural concrete members reinforced internally using FRP and designed using the Canadian Highway Bridge Design Code (CSA-S6-19), the Design and Construction of Building Structures with Fibre-reinforced Polymers Standard (CSA-S806-17), and Design and Construction of Structural Concrete Reinforced with FRP bars Guideline (ACI440.1R-15); and (2) recommend FRP material resistance factor and strength reduction factor for the respective codes/standards based on a unified target reliability approach. Reliability analysis using Monte Carlo simulation indicates that the reliability index associated with a flexural design using ACI440.1R-15 is about 20% greater than the average reliability index of similar beam and slab sections designed using CSA S6-19 and CSA S806-17 (equates to 150 times greater probability of failure for sections designed using CSA S6 and CSA S806). The recommended material resistance factors for CSA S6 and CSA S806 and the strength reduction factor for ACI 440.1R based on the reliability analysis conducted in this research are 0.80, 0.85, and 0.75, respectively, for a unified target reliability indexes of 4.0 and 3.1 for beams and slabs, respectively. Structural designs based on the recommended values yield consistent reliability indexes among the three codes/standards.
July 1, 2022
The use of recycled concrete aggregate, as a component of the new concrete mixture, implies a thorough understanding of its basic properties, considering that they may significantly differ from the properties of natural aggregates. It is believed that its performance can be enhanced by improving the surface properties of RCA. Coating RCA grains within a triple mixing process represents one of the promising methods. This principle has been adopted by several researchers who report a significant improvement in concrete properties compared to standard mixing, especially through improved ITZ parameters. In the paper, the triple mixing process of concrete with coarse RCA was studied, while the method of applying the mineral powdery materials (cement, fly ash, and fine particles of RCA) to the pre-moistened aggregate was used. A comparison of positive/negative effects of three-stage mixing on the set of six properties of concrete, comparing standard mixing is presented. It was found that three-stage mixing has no different effect on samples prepared after prolonged mixing than on samples prepared immediately after mixing, nor on samples cured for 90 days than on samples cured 28-days. Cement as a coating material gave the best results in the presented range of testing while RCA powder showed promising potential.
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