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International Concrete Abstracts Portal

Showing 1-5 of 76 Abstracts search results

Document: 

SP-340-13

Date: 

April 1, 2020

Author(s):

Patryk J. Wolert, Andrzej S. Nowak, and J. Michael Stallings

Publication:

Symposium Papers

Volume:

340

Abstract:

Existing road infrastructure and bridges gradually carry increasing in weight and number vehicular traffic. The objective of this study is to assess adequacy of a 100-year-old reinforced concrete framed bridge in Alabama expressed as reliability index. Geometric data about the structure was obtained using destructive and nondestructive testing methods. Material data was collected from field tests and available literature on evaluation of existing structures. Behavior of the structure was investigated during load tests performed. The most harmful load configuration for the particular bridge was established in a recent study on weigh-in-motion data for the State of Alabama. Using finite element numerical method, a three dimensional model of the bridge was developed, calibrated and used for reliability study. The statistical parameters of resistance of the bridge were obtained using Rosenblueth 2k+1 method. The reliability analysis was demonstrated on the one span structural system.


Document: 

SP333

Date: 

October 9, 2019

Author(s):

Yail J. Kim, John J. Myers, and Antonio Nanni

Publication:

Symposium Papers

Volume:

333

Abstract:

Concrete bridges play an important role in the efficiency and reliability of transportation civil infrastructure. Significant advancements have been made over the last decades to enhance the performance and durability of bridge elements at affordable costs. From an application perspective, novel analysis techniques and construction methods are particularly notable, which have led to the realization of more sustainable built-environments. As far as the evaluation and rehabilitation of constructed bridges are concerned, new nondestructive testing approaches provide accurate diagnosis and advanced composites, such as carbon fiber reinforced polymer (CFRP), have become an alternative to conventional materials. This Special Publication (SP) contains nine papers selected from two technical sessions held at The ACI Concrete Convention and Exposition – Spring 2018, in Salt Lake City, UT. The objective of the SP is to present technical contributions aimed to understand the state of the art of concrete bridges, identify and discuss challenges, and suggest effective solutions for both practitioners and government engineers. All manuscripts were reviewed in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance in the development of the SP.


Document: 

SP-332_02

Date: 

July 1, 2019

Author(s):

Pericles C. Stivaros

Publication:

Symposium Papers

Volume:

332

Abstract:

A successful concrete repair project requires a close coordination of efforts between the three major parties involved: the owner, the licensed design professional (LDP), and the contractor. Lack of coordination and clear understanding of the professional and contractual responsibilities, as well as the expectations, of each party involved in a concrete repair project, could result in long legal disputes to attempt to sort out the responsibilities of each party. The greatest victim of the dispute is usually the structure itself. The American Concrete Institute (ACI) has led the effort to develop responsibility guidelines in concrete construction. ACI 132 identifies and suggests the allocation of responsibilities to various parties involved in concrete construction. ACI 132 document is applicable to general concrete construction, and it does not consider the particularities of evaluating and repairing existing concrete structures. ACI 562 provides minimum requirements for assessment, repair and rehabilitation of existing distressed concrete structures, including a discussion on the responsibilities of the licensed design professional for the evaluation and repair of concrete structures. This paper discusses the responsibilities of the licensed design professional, the contractor, and the owner through a repair case study. The paper demonstrates the need to expand ACI 132 and/or ACI 562 to include responsibility guidelines for concrete repair projects.


Document: 

SP326-94

Date: 

August 10, 2018

Author(s):

Amde M. Amde, Richard A. Livingston, and John W. Newman

Publication:

Symposium Papers

Volume:

326

Abstract:

Laser shearography has shown a great potential for application in nondestructive testing (NDT) especially in the early detection of cracks in concrete. It records a sheared image of the speckle interferogram produced by illuminating an object with a laser. The objectives of the research were to evaluate the capability of laser shearography to detect fine early age cracks and to apply it to investigate possible differences in crack patterns between delayed ettringite formation (DEF) and freeze-thaw (FT) processes. It demonstrated that the laser shearography is capable of detecting fine cracks in early age concrete even when they are invisible to the naked eye (<10 μm). This provided quantitative information about trends in development of damage in concrete due to DEF or FT. The damage progressed over time by the propagation of the initial cracks rather than the appearance of new cracks which is consistent with the Holt and Janssen hypothesis. The density of cracks in the FT concrete specimens was greater than in those of the heat treated specimens and the rate of crack development was also faster, which is consistent with the Garboczi expansive stress model. Finally, increased potassium content accelerated the rate of crack development for both types of damage.


Document: 

SP298-07

Date: 

June 5, 2014

Author(s):

Angelique N. Lasseigne, Eric R. Giannini, and Joshua Jackson

Publication:

Symposium Papers

Volume:

298

Abstract:

Engineers currently lack the ability to non-destructively measure through-thickness elastic and plastic strain of steel reinforcement in reinforced concrete structures. This capability would be of considerable use in assessing structures damaged by extreme events, corrosion, or slower-acting expansive reactions in concrete such as ASR, DEF and sulfate attack. New non-contact electromagnetic sensors have been demonstrated for providing this capability on bridge girder sections. When steel is strained, the electronic properties of the metal are altered and there is a measurable change in the electromagnetic response of the metal. These changes in material properties can be used to measure strain in the steel reinforcement from outside the concrete. This paper describes the results of preliminary tests involving samples of exposed rebar, concrete-encased rebar, and a full-scale reinforced concrete beam. The rebar specimens were placed in tension while typical strain gauges and the non-contact electromagnetic stress measurements were simultaneously performed. The specimens were then loaded well in excess of the yield point, to ensure both elastic and plastic straining occurred. Electromagnetic sensors were positioned to monitor changes in strain in a stirrup and a longitudinal reinforcing bar during a flexural test of a full-scale beam that had previously undergone significant expansion from ASR and DEF. The results of these early tests indicate the eStress system can provide valuable insight into the strains in bridges and other structures, thus providing an improved method for maintenance and repair.


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