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International Concrete Abstracts Portal

Showing 1-5 of 29 Abstracts search results

Document: 

SP238-02

Date: 

October 1, 2006

Author(s):

J.P. Moehle and D.E. Lehman

Publication:

Symposium Papers

Volume:

238

Abstract:

A current focus in earthquake engineering research and practice is the development of seismic design procedures whose aim is to achieve a specified performance. To implement such procedures, engineers require methods to define damage in terms of engineering criteria. Previous experimental research on bridge columns has focused on component failure, with relatively little attention to other damage states. A research program was undertaken to assess the seismic performance of well-confined, circular-cross-section, reinforced concrete bridge columns at a range of damage states. The test variables included aspect ratio, longitudinal reinforcement ratio, spiral reinforcement ratio, axial load ratio, and the length of the well-confined region adjacent to the zone where plastic hinging is anticipated. The experimental results are used to identify important damage states and to link those states to engineering parameters.

DOI:

10.14359/18262


Document: 

SP238-05

Date: 

October 1, 2006

Author(s):

S.K. Kunnath

Publication:

Symposium Papers

Volume:

238

Abstract:

Concepts in ductile design have led to an increased interest in understanding the role of confinement in improving the seismic performance of reinforced concrete members. While transverse reinforcement is regarded as a form of passive confinement in RC members, the observed increase in the strength of confined concrete is typically a function of the axial strain levels. Confinement models have been developed by numerous researchers to describe the stress-strain behavior of concrete as a function of certain key parameters that are related to the amount and type of transverse reinforcement. Accurate constitutive models of confined concrete are necessary for direct use in fiber-model based discretization of RC components or for indirect use in hysteresis based phenomenological models. This paper examines the relevance and importance of accurate confinement modeling in predicting the inelastic behavior of well-confined concrete columns. In particular, the influence of incorporating confinement effects in predicting the monotonic and cyclic response of RC columns is investigated. It is analytically demonstrated that the role of the longitudinal reinforcing bars play a more significant role in determining the overall force-deformation behavior of RC components. Detailed fiber-based discretizations that rely entirely on constitutive models are incapable of reproducing post-yield softening and deterioration because of their inability to incorporate complex large deformation behavior of both the longitudinal and the confining reinforcement. Approximate phenomenological models will continue to see widespread use in inelastic analysis of RC structures until these limitations of constitutive-based element models are overcome.

DOI:

10.14359/18265


Document: 

SP238-24

Date: 

October 1, 2006

Author(s):

W.-J. Yi, Q.-l. Xian, H.-T. Ding, and H.-y. Zhang

Publication:

Symposium Papers

Volume:

238

Abstract:

The objective of this research project is to conduct an experimental study of the behavior of carbon fiber-reinforced polymer (CFRP) materials for strengthening reinforced concrete structures. The test program consisted of 23 reinforced concrete columns strengthened with CFRP sheets under static eccentric compressive loading. It is shown that under large eccentric compression loading, ultimate capacity of the columns can be effectively increased with the longitudinal CFRP sheets, and the ductility factors of the columns can be increased with the transverse CFRP sheets. It was observed that the material strength utilization of transverse CFRP sheets was more sufficient than that of longitudinal CFRP. The transverse CFRP sheets were broken at failure of a column, but the maximum measured strain in the longitudinal CFRP was only about 5000µe at peak load.

DOI:

10.14359/18284


Document: 

SP238-20

Date: 

October 1, 2006

Author(s):

J.G. Teng and L. Lam

Publication:

Symposium Papers

Volume:

238

Abstract:

Over the past decade, fibre-reinforced polymer (FRP) composites have found wide applications in civil engineering, particularly in the retrofit of structures. One important application of FRP composites in the retrofit of reinforced concrete (RC) structures is to provide confinement to columns for enhanced strength and ductility. As a result, a large number of studies have been carried out on the compressive behaviour of FRP-confined concrete. This paper provides a state-of-the-art review of existing studies on this subject, with the emphasis being on the revelation of the fundamental behaviour of FRP-confined concrete and the modelling of this behaviour. Both monotonic loading and cyclic loading are covered, although only a limited amount of work is available on the latter. The paper is explicitly limited to concrete confined with FRP jackets, in which the fibres are oriented only or predominantly in the hoop direction, but many of the observations made in this paper are also relevant to concrete confined with FRP jackets with a significant axial stiffness, as found in concrete-filled FRP tubes as new columns.

DOI:

10.14359/18280


Document: 

SP238-21

Date: 

October 1, 2006

Author(s):

J.F. Stanton and L.M. Owen

Publication:

Symposium Papers

Volume:

238

Abstract:

This paper describes a series of tests on concrete cylinders confined by carbon fiber jackets. The primary variables in the investigation were the thickness of the jackets (and therefore the lateral confinement stress), the size of the cylinders, the loading speed, and the loading type (monotonic vs. cyclic), and the jacket type (individual layers or continuous wrap). Of these parameters, the lateral confining stress was found to have the greatest influence, but the coefficient for the concrete used was found to be slightly lower than the 4.1 that is implicit in ACI318-02. The cylinder size, the loading speed and the cyclic loading regimes were found to have essentially no influence on stress and strain at failure. The continuously wound jackets were found to initiate failure by delamination, rather than fracture of the fiber, and to lower the stress and strain at failure.

DOI:

10.14359/18281


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