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International Concrete Abstracts Portal

Showing 1-5 of 15 Abstracts search results

Document: 

SP272

Date: 

October 1, 2010

Author(s):

Editors: Gustavo J. Parra-Montesinos and Perumalsamy Balaguru / Sponsored by: ACI Committee 544 and ACI Committee 549 and Joint ACI-ASCE Committee 423

Publication:

Symposium Papers

Volume:

272

Abstract:

This Symposium Publication contains 14 papers that were presented at technical sessions sponsored by ACI Committees 544 and 549, and Joint ACI-ASCE Committee 423 at the 2008 ACI Spring Convention in Los Angeles, CA. Topics covered in these papers include development, mechanical behavior, modeling and structural applications of fiber- reinforced concrete and thin laminate composites; repair and rehabilitation of reinforced and prestressed concrete members; and new developments in prestressed concrete bridges. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-272

DOI:

10.14359/51664007


Document: 

SP272-12

Date: 

October 1, 2010

Author(s):

M.H. Harajli, F.K. Dagher, and A.M. ElSouri

Publication:

Symposium Papers

Volume:

272

Abstract:

This paper presents the results of an experimental investigation under-taken for evaluating the cyclic lateral load-drift response of rectangular reinforced concrete (RC) columns which were damaged due to large drift reversals, but then repaired for upgrading the bond strength of the spliced reinforcement within the critical hinging region. The original specimens consisted of full-scale unconfined and fiber-reinforced polymer (FRP) confined columns having a relatively high section aspect ratio of 2.0. These original specimens were subjected to large drift reversals until complete bond degradation of the spliced reinforcement within the hinging zone and complete loss of flexural strength of the columns8. The repair procedure consisted of removing the deteriorated concrete within the damaged/splice zone and casting new concrete. Two types of concrete confine-ment for improving the bond strength and flexural capacity were investigated and compared, namely, internal confinement by transverse steel ties and external confinement using carbon fiber-reinforced polymer (CFRP) jackets. It was found that repairing the bond-damaged zone through concrete confinement leads to substantial regain of flexural strength up to or exceeding the strength of the original specimens, lower structural damage associated with concrete fracturing and bond degradation, and considerable improvement of the energy dissipation capacity under cyclic loading. Confinement by external FRP jackets was relatively more effective than confinement by internal steel ties. However, unlike columns with continuous reinforcement, columns with spliced reinforcement within the hinging region experienced significant bond and strength degradation beyond drift ratios between 3 and 4%, irrespective of the type and amount of confinement used. The experimental results are discussed, and a design expression for estimating the thickness of the FRP jacket required for seismic bond strengthening is presented and compared with the test data.

DOI:

10.14359/51664094


Document: 

SP272-10

Date: 

October 1, 2010

Author(s):

J.W. Nam, M.P. Abell, Y.M. Lim, and J.E. Bolander

Publication:

Symposium Papers

Volume:

272

Abstract:

Short-fiber reinforcement is commonly added to cement-based materials to improve various aspects of their durability and life-cycle performance. Effective designs of Fiber Reinforced Cement Composites (FRCC) depend not only on material composition, but also on their methods of processing. In particular, the distribution of fibers within a structural component can significantly affect its resistance to cracking and, therefore, its durability when exposed to severe environments. Probability-based analyses can be used to accommodate such factors in life-cycle performance evaluation, in which the relevant performance measures are described by probability distributions and their evolution over time. This paper concerns the simulation of FRCC materials using lattice models, in which the individual fibers are explicitly modeled within the material domain. This approach facilitates the study of non-uniform fiber dispersions and their potential effects on structural performance.

DOI:

10.14359/51664092


Document: 

SP272-06

Date: 

October 1, 2010

Author(s):

S.P. Shah, L. Ferrara, and S.H. Kwon

Publication:

Symposium Papers

Volume:

272

Abstract:

The synergy between self-consolidating concrete (SCC) and steel fiber-reinforced concrete (SFRC) technologies may yield, besides the well known and assessed characteristics of each single technology, several interesting peculiar advantages that can be fruitfully exploited by the construction industry, mainly in the field of precast construction. Better controlled fiber dispersion, improved fiber-matrix bond, and enhanced durability due to the higher compactness of the SCC matrix are among the most relevant issues to which the largest part of research efforts were dedicated in the very last decade. The robustness of self-consolidating steel fiber-reinforced concrete (SCSFRC), which relies on sound mix-design methodology and on effective dedicated quality control procedures, has been demonstrated to be crucial in order to achieve the above recalled advantages. This paper summarizes the most significant results of the research activity carried out by the authors in this field, furthermore underlying the outcomes with reference to structural applications.

DOI:

10.14359/51664088


Document: 

SP272-05

Date: 

October 1, 2010

Author(s):

J. Giancaspro, P. Balaguru, and C.G. Papakonstantinou

Publication:

Symposium Papers

Volume:

272

Abstract:

There are a limited number of experimental results available on the retrofit of prestressed concrete structural elements. In addition, there is a lack of analytical models dealing with the flexural performance of such elements. This study addresses the latter problem by presenting a methodology for analysis and design of prestressed concrete flexural elements strengthened with externally bonded, fiber reinforced composites. The method provides systematic suggestions on the analysis and design of strengthened prestressed concrete beams with both bonded and unbonded tendons. The method can be used to determine the flexural capacity and to compute stresses and strains in concrete, tendons, and externally bonded fiber reinforcement. Compared to existing experimental data on carbon strengthened beams, the model provides very good prediction of the flexural performance of strengthened prestressed beams. The equations are also applicable to other fiber types including glass, steel, and aramid.

DOI:

10.14359/51664087


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