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Farmington Hills, MI, United States

The American Concrete Institute is a non-profit technical society and standard developing organization . ACI was founded in 1904 and its headquarters are currently located in Farmington Hills, Michigan, USA. ACI's mission is "ACI develops and disseminates consensus-based knowledge on concrete and its uses." Wikipedia.

Zadeh H.J.,University of Miami | Nanni A.,University of Miami | Nanni A.,American Concrete Institute
ACI Structural Journal

By employing the concept of reliability index, an interim index of "comparative reliability" is proposed that bypasses the loading variables and weighs the resistances of two structural elements with the same ultimate limit state directly against each other. The comparative reliability index is then related to the conventional target reliability to allow a simple calculation method of the strength reduction factor for elements whose safety factor is yet to be calibrated. This is achieved by comparing a pair of elements that experience the same failure mode and yet only one holds a validated level of safety (that is, strength reduction factor and reliability index). This concept is put into practice by calculating flexural and shear-strength reduction factors for fiber-reinforced polymer (FRP) reinforced concrete (RC) members by comparison with conventional steel-reinforced concrete beams possessing the same ultimate capacity. As a result, a revised set of strength reduction factors and deign provisions are proposed for use in FRP design guidelines for shear and flexure. Copyright © 2013 American Concrete Institute. Source

Kesner K.,American Concrete Institute
Forensic Engineering 2015: Performance of the Built Environment - Proceedings of the 7th Congress on Forensic Engineering

Evaluation and/or repair of existing concrete buildings can be challenging to design professionals, owners, building officials, and contractors. Difficulties arise due to a myriad of questions pertaining to the necessary extent of repairs, responsibilities during the project, and uncertainties regarding the governing code requirements. The concept of a building code for repair of existing concrete structures has been discussed for nearly thirty years. However, a major obstacle to the development of a concrete repair code was how it would interact with existing codes, such as ACI 318, general building codes and the International Building Code (IBC) that were developed primarily for the use during new construction. The development of the International Existing Building Code (IEBC) has provided design professionals a pathway delineating code requirements for repair and alterations of existing structures. ACI 562 was developed to work both with the IEBC and as a stand-alone code to provide design professionals a code for the repair of existing concrete buildings. © 2016 ASCE. Source

Sonebi M.,Queens University of Belfast | Sonebi M.,American Concrete Institute | Malinov S.,Queens University of Belfast
ACI Materials Journal

The development of artificial neural network (ANN) models to predict the rheological behavior of grouts is described is this paper and the sensitivity of such parameters to the variation in mixture ingredients is also evaluated. The input parameters of the neural network were the mixture ingredients influencing the rheological behavior of grouts, namely the cement content, fly ash, ground-granulated blast-furnace slag, limestone powder, silica fume, water-binder ratio (w/b)), high-range water-reducing admixture, and viscosity-modifying agent (welan gum). The six outputs of the ANN models were the mini-slump, the apparent viscosity at low shear, and the yield stress and plastic viscosity values of the Bingham and modified Bingham models, respectively. The model is based on a multi-layer feed-forward neural network. The details of the proposed ANN with its architecture, training, and validation are presented in this paper. A database of 186 mixtures from eight different studies was developed to train and test the ANN model. The effectiveness of the trained ANN model is evaluated by comparing its responses with the experimental data that were used in the training process. The results show that the ANN model can accurately predict the mini-slump, the apparent viscosity at low shear, the yield stress, and the plastic viscosity values of the Bingham and modified Bingham models of the pseudo-plastic grouts used in the training process. The results can also predict these properties of new mixtures within the practical range of the input variables used in the training with an absolute error of 2%, 0.5%, 8%, 4%, 2%, and 1.6%, respectively. The sensitivity of the ANN model showed that the trend data obtained by the models were in good agreement with the actual experimental results, demonstrating the effect of mixture ingredients on fluidity and the rheological parameters with both the Bingham and modified Bingham models. Copyright © 2011, American Concrete Institute. All rights reserved. Source

Collepardi M.,American Concrete Institute
American Concrete Institute, ACI Special Publication

Ground bottom ash (GBA) from Municipal Solid Wastes Incinerators (MSWI) does not perform as well as other mineral additions -such as silica fume or fly ash produced by coal burning- due to the presence of aluminium metal particles which react with the lime formed by the hydration of portland cement and produce significant volume of hydrogen in form of gas bubbles which increase the porosity of concrete and reduce its strength. Due to this drawback, a new process was developed to separate the aluminium metal particles through a mechanical removal of metals and a wet grinding of bottom ashes. At the end of the process, GBA was used as aqueous slurry to replace portland cement. In the present work GBA with a maximum size of 1.7 μm (0.07 μin) was used to replace about 10% of portland cement in self-compacting concretes (SCC). Mixtures with shrinkage-reducing admixture (SRA) and a CaO-based expansive agent were also manufactured to reduce the drying shrinkage and the related cracks. Moreover, an alternative way to reduce both number and length of cracks was adopted by using SRA combined with polyvinyl alcohol (PVA) macrosynthetic fibres. Corresponding mixtures with silica fume or fly ash were also manufactured. GBA performed as well as silica fume in terms of mechanical properties, durability and crack behavior, and much better than fly ash. Source

Mihaylov B.I.,University of Toronto | Bentz E.C.,University of Toronto | Bentz E.C.,American Concrete Institute | Collins M.P.,University of Toronto
ACI Structural Journal

While anchor heads are particularly useful in the case of large bars, which require significant development lengths, the ACI Code provides design guidance for bars No. 11 or smaller. This paper presents a test of a large deep beam reinforced with a single No. 18 headed bar. The behavior of the beam is evaluated in comparison to the behavior of a specimen with more conventional reinforcement of six No. 8 headed bars, and to the behavior of a specimen with lap-spliced anchor hooks. Despite the extreme detailing of the specimen with a single No. 18 bar, the beam had the same strength as the specimen with six No. 8 bars. The compressive stress in front of the anchor head reached approximately 1.5 times the compressive strength of the concrete, and the stress in the No. 18 bar reached approximately 414 MPa (60 ksi) before the beam failed in shear along a diagonal crack away from the anchorage zone. Shear strength calculations according to Appendix A of the ACI Code showed that the current strut-and-tie provisions can overestimate the shear strength of deep beams by as much as 23%. Copyright © 2013 American Concrete Institute. Source

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