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International Concrete Abstracts Portal

Showing 1-5 of 249 Abstracts search results

Document: 

SP-344_02

Date: 

October 1, 2020

Author(s):

Giorgio T. Proestos, Evan C. Bentz, Michael P. Collins

Publication:

Symposium Papers

Volume:

344

Abstract:

The traditional approach in the design of reinforced and prestressed concrete building structures has been to design each of the two orthogonal directions independently. In calculating the distribution of moments in a structure, this two-dimensional approach neglects the effects of the intersecting members. That is, in the case of compatibility torsions, the torsional stiffness is neglected. This paper provides a summary of the progression of the ACI code and commentary pertaining to the zero torsional stiffness assumption and its origins. The paper then introduces a recently developed nonlinear finite element analysis tool, VAST II, capable of predicting the response of reinforced and prestressed concrete structures in three-dimensions. The tool, based on the Modified Compression Field Theory, is capable of modelling entire structures or large portions of structures in order to assess their performance in a manner that accounts for three-dimensional effects, such as compatibility torsions. VAST II is then used to model a case study transit center. The transit center is a post-tensioned concrete structure that was designed using the traditional approach of neglecting the effects of compatibility torsions. The results indicate that the traditional approach recommended by the ACI code and commentary, to neglect compatibility torsions, is appropriate and gives robust designs. The paper concludes by providing recommendations for future studies that could be conducted using three-dimensional nonlinear tools such as VAST II. Keywords:


Document: 

SP-343_48

Date: 

October 1, 2020

Author(s):

Redaelli, D.; Nseir, J.Y.

Publication:

Symposium Papers

Volume:

343

Abstract:

This paper presents the results of a numerical study carried out by the authors to better understand the structural behavior of prestressed beams with web openings and to identify numerical modelling techniques that allow to adequately predict such behavior. Ultra-High Performance Fibre Reinforced Concrete (UHPC) beams are considered, with a focus on shear-controlled failure modes. For all the beams considered in this study, prestressing is used to resist the main bending moment. However, no other reinforcement is added to the beams, in order to emphasize the structural contribution of the fibers and to focus on solutions that could be economically competitive for the precast industry. The results of non-linear simulations performed with existing finite elements codes are compared and validated against experimental results of tests carried out at the University of Applied Sciences of Western Switzerland. The main assumptions of the numerical simulations are discussed, as well as the results and the limits of the analysis.


Document: 

SP-343_32

Date: 

October 1, 2020

Author(s):

Antroula, G.; Stavroula, P.

Publication:

Symposium Papers

Volume:

343

Abstract:

With the advent of strain hardening fiber reinforced cementitious composites (SHFRCC) the development of a new generation of structural systems that benefit from the inherent ductility of concrete in tension in order to reduce the amounts of transverse reinforcement (stirrups), shear strength, and tension-force development capacity to the main reinforcement is possible. In this study a number of tests are conducted to explore the behavior of SHFRCC materials under cyclic loads, simulating seismic effects. The experimental responses of two half-scale interior beam column connections subjected to reversed cyclic loading are compared; one of the connections was constructed with a cementitious matrix without fibers, and was detailed according with the Eurocode provisions for ductility class M (moderate, μ=3.5). The other connection was constructed with a SHFRCC mix; (2% by volume of PVA fibers was used to reinforce the matrix and the minimum amount of shear reinforcement allowed by Eurocode 2 for non-seismic detailing was used in the specimens). Several supporting experiments were also conducted to support analysis of the cyclic behavior (uniaxial tension, compression, splitting tests). The behavior of the members under reversed cyclic displacement is also simulated with advanced nonlinear Finite Element Analysis, with results that are correlated with the experimental observations. The SHFRCC specimen with minimum detailing showed improved performance and enormous ductility suggesting new possibilities to the seismic design of structures.


Document: 

SP-343_17

Date: 

October 1, 2020

Author(s):

Juhasz, K.P.; Schaul, P.

Publication:

Symposium Papers

Volume:

343

Abstract:

In the past decade macro synthetic fibre reinforcement has become widely used for concrete track slabs including tramlines. By using macro synthetic fibres as a reinforcement in concrete slabs both the casting time and manual work will decrease, while the concrete’s ductility will increase. In addition the durability will be higher with using synthetic fibres, and the carbon footprint will be lower compared to steel mesh or fibre reinforcement. In most cases the steel reinforcement can be omitted entirely from the structures using macro synthetic fibres. The uniformly distributed fibres in the concrete can increase the residual flexural strength of the concrete independently from the location. This makes it possible to use the fibres in both cast in situ and precast elements used for tramlines. The calculation process for these structures always has to comprise of both the static load, the dynamic load and the effect of cyclic loading, i.e. fatigue. These load calculations can be handled using advanced finite element analysis software, which is specialized for concrete and fibre reinforced concrete structures. The paper will present the opportunities for using macro synthetic fibres together with the process of designing fibre reinforced concrete tramlines.


Document: 

SP342

Date: 

July 17, 2020

Publication:

Symposium Papers

Volume:

342

Abstract:

Sponsors: Sponsored by ACI Committees 342, Evaluation of Concrete and 343, Concrete Bridge Design (Joint ACI-ASCE) Editors: Benjamin Z. Dymond and Bruno Massicotte In recent years, both researchers and practicing engineers worldwide have been refining state-of-the-art and emerging technologies for the strength evaluation and design of concrete bridges using advanced computational analysis and load testing methods. Papers discussing the implementation of the following topics were considered for inclusion in this Special Publication: advanced nonlinear modeling and nonlinear finite element analysis (NLFEA), structural versus element rating, determination of structure specific reliability indices, load testing beyond the service level, load testing to failure, and use of continuous monitoring for detecting anomalies. To exchange international experiences among a global group of researchers, ACI Committees 342 and 343 organized two sessions entitled “Advanced Analysis and Testing Methods for Concrete Bridge Evaluation and Design” at the Spring 2019 ACI Convention in Québec City, Québec, Canada. This Special Publication contains the technical papers from experts who presented their work at these sessions. The first session was focused on field and laboratory testing and the second session was focused on analytical work and nonlinear finite element modeling. The technical papers in this Special Publication are organized in the order in which they were presented at the ACI Convention. Overall, in this Special Publication, authors from different backgrounds and geographical locations share their experiences and perspectives on the strength evaluation and design of concrete bridges using advanced computational analysis and load testing methods. Contributions were made from different regions of the world, including Canada, Italy, and the United States, and the technical papers were authored by experts at universities, government agencies, and private companies. The technical papers considered both advanced computational analysis and load testing methods for the strength evaluation and design of concrete bridges.


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