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 603 Abstracts search results

Document: 

SP344

Date: 

October 21, 2020

Publication:

Symposium Papers

Volume:

344

Abstract:

The design and analysis of structural concrete elements is a topic of practical interest. While sometimes the effect of torsion is only addressed based on simple examples, practicing engineers are faced with the need to include the effects of torsion in their designs of a variety of structures and load arrangements. This Special Publication (SP) contains papers about the design of reinforced and prestressed concrete elements for torsion. The focus of the SP is on practical design examples according to different concrete bridge and building codes. In addition to the design examples, papers dealing with the current state of the art on torsion in structural concrete, as well as recent advances in the analysis and design of concrete elements failing in torsion, are added. The objectives of this SP are to provide practicing engineers with the tools necessary to better understand and design concrete elements for torsion. The need for this SP arose after the development of the State-of-the-Art Report on Torsion of Joint ACI-ASCE Committee 445 “Shear and Torsion” and Subcommittee 445-E “Torsion”. Usually, the attention that is paid to torsion in engineering education is limited to simplified textbook examples. The examples in this SP show applications in bridges and buildings, where the torsion design is combined with the design for flexure and shear. Additionally, the examples in this SP give insight on the different outcomes when using different bridge and building codes. Finally, the papers that include theoretical considerations give practicing engineers a deeper understanding and background on torsion in structural concrete. The views from an international group of authors are included in this SP, subsequently representing a variety of building and bridge codes the engineer may encounter in practice. In particular, authors from the United States, Canada, Ecuador, the Netherlands, Italy, Greece, and the Czech Republic contributed to the papers in this SP. Views from academia and the industry are included. To exchange experience in the design of torsion-critical structures as well as new research insights on torsion, Joint ACI-ASCE Committee 445 and Subcommittee 445-E organized two sessions titled “Examples for the Design of Reinforced and Prestressed Concrete Members under Torsion” at the ACI Fall Convention 2020. This SP contains several technical papers from experts who presented their work at these sessions, in addition to papers submitted for publication only. In summary, this SP addresses numerous practical examples of structural elements under torsion in bridges and buildings, as well as insights from recent research applied to practical cases of elements under torsion. The co-editors of this SP are grateful for the contributions of the authors and sincerely value the time and effort they invested in preparing the papers in this volume, as well as the contributions of the reviewers of the manuscripts.


Document: 

SP-344_04

Date: 

October 1, 2020

Author(s):

Allan Kuan, Edvard P.G. Bruun, Evan C. Bentz, and Michael P. Collins

Publication:

Symposium Papers

Volume:

344

Abstract:

Although the torsion design procedures in ACI 318-19 are simple and broadly applicable, the resulting designs tend to be conservative. To address this, clause 9.5.4.6 in ACI 318-19 permits the use of an alternative design procedure when designing members with an aspect ratio ≥ 3 for torsion, provided that the alternative procedure has been shown to agree with the results of comprehensive tests. This paper evaluates and compares the torsion design procedures in CSA A23.3:19 and the PCI Design Handbook 8th edition with those in ACI 318-19. Each of the three methods are found to show good agreement with 282 tests found in the literature. A comparison of the three concludes that the designs obtained using the ACI method generally require the most reinforcement. More economical designs for members subjected to relatively low and high torques can be obtained by using the PCI and CSA methods respectively. A design example of a spandrel beam using the three methods is presented, and then further conclusions are stated to guide practicing engineers on the relative strengths and weaknesses of each procedure.


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-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_20

Date: 

October 1, 2020

Author(s):

Massicotte, B.; Cordoni, N.

Publication:

Symposium Papers

Volume:

343

Abstract:

Accelerated bridge construction is becoming a subject of major importance and, combined use of steel fibre reinforced concrete (SFRC) and prestressing, this construction technique offers a unique opportunity to fulfill the demand of more sustainable infrastructure with enhanced durability and life-cycle cost reduction. Research projects carried out at Polytechnique Montreal in the past 20 years have demonstrated that the combined use of prestressing, SFRC, prefabrication and ultra-high performance fibre reinforced concrete (UHPFRC) allows developing more economical and durable bridges. A project on precast Tgirders was initiated with the aim of developing a new set of prestressed girders for new bridges in the 10 to 30 m span range using conventional prestressing and shear reinforcement, reduced top flange transverse reinforcement and field-cast UHPFC longitudinal joints between girders. It is anticipated that bridge built with this concept will only require minimum maintenance over a 75-year service life in harsh environmental conditions.


12345...>>

Results Per Page 




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