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International Concrete Abstracts Portal

Showing 1-5 of 29 Abstracts search results

Document: 

SP238-18

Date: 

October 1, 2006

Author(s):

H. Nakahara and K. Sakino

Publication:

Symposium Papers

Volume:

238

Abstract:

In order to evaluate the load carrying capacity and ductility of hinging zone ofthe concrete filled steel tubular (CFT) columns, tests are carried out on 12 circular speci-mens and 18 square specimens subjected to uniform bending under a constant axial load.The experimental parameters are: 1) depth to thickness ratio (D/t ratio) and width to thick-ness ratio (B/t ratio) of steel tube; 2) axial load ratio; 3) material strength; 4) deformationhistory and 5) annealing. One of the features of the test is the wide range of D/t and B/tratio. The range of D/t ratio of the circular CFT columns are 40.5-160 and the range of B/t ratio of the square CFT columns are 32.8-98.0, respectively. The experimental load-de-formation relations are compared with those of the elasto-plastic analysis based on theproposed stress-strain relationships established for the filled concrete and for the steel tube.The analytical results show good agreement with the test results for all specimens. Thisimplies that the proposed stress-strain relationships for CFT columns are useful to predictthe characteristics of the filled concrete and the steel tube.

DOI:

10.14359/18278


Document: 

SP238-04

Date: 

October 1, 2006

Author(s):

F. Watanabe

Publication:

Symposium Papers

Volume:

238

Abstract:

A key of seismic design of ductile frame is to provide the adequate flexural ductility to potential plastic hinge regions. This is realized by limiting the amount of tension reinforcement index, providing transverse reinforcement and others. For columns, the application of transverse reinforcement to potential plastic hinge region is essential, that is, the compressive ductility of concrete is improved and results in larger flexural ductility. In the 1980s, a new RC project was carried out as a Japanese National Project to establish the design and construction guidelines for high-rise buildings up to 200 meters high. For columns at the lower part of high-rise buildings, the use of high-strength concrete (HSC) is required. However, HSC fails in brittle manner and results in small flexural ductility of potential plastic hinges. Therefore the new RC project gave an opportunity to re-recognize the importance of lateral confinement to concrete. This paper presents the recent research works on confined concrete in Japan, mainly for HSC. Some experimental works and idealizations of stress-strain curve of confined concrete are introduced. Maximum compressive strength covered in this paper is 176 MPa.

DOI:

10.14359/18264


Document: 

SP238-03

Date: 

October 1, 2006

Author(s):

S. Bae and O. Bayrak

Publication:

Symposium Papers

Volume:

238

Abstract:

In performance-based seismic design, evaluation of the deformation capacity of reinforced concrete columns is of paramount importance. The deformation capacity of a column can be expressed in several different ways: (1) curvature ductility, (2) displacement ductility, or (3) drift. Even though several performance-based confining reinforcement design procedures have been proposed, the relationship between different ductility factors is not clearly understood. The effect of concrete strength, longitudinal reinforcement ratio, volumetric ratio of confining reinforcement, shear span-to-depth ratio, and axial load level on the relationship between different ductility factors was studied. Finally, the confinement reinforcement design requirements of current design codes and recently proposed performance-based design methods were compared and critically examined.

DOI:

10.14359/18263


Document: 

SP238-27

Date: 

October 1, 2006

Author(s):

S.P. Shang, L.M. Jiang, M.X. Zhang, and L.H. Zeng

Publication:

Symposium Papers

Volume:

238

Abstract:

Eleven approximate full-size specimens including nine eccentrically compressed columns of monotonic loading and two axially compressed columns of laterally cyclic loading were tested. By a series of comparison experiment of specimens strengthened using a kind of composite mortar laminates reinforced by mesh reinforcements (CMMR laminates) and no strengthened specimens, it was found that the RC columns strengthened with attached CMMR laminates demonstrated greater degree of improving in load-bearing capacity, in which the carrying capacity increment of the strengthened eccentrically compressed columns with lesser eccentricity was greater than that of the same type of columns with bigger eccentricity under the same strengthening conditions; the strengthening effects of the specimens with lower concrete grade are better than that of those ones with higher concrete grade; the ductility and the deformation capacity and energy dissipation ability of the strengthened columns were remarkably increased. In this paper, the test results is described, the principle and regularity that this category of strengthening laminate improved the ultimate load-bearing capacity, ductility, cracking behavior and mode of failure etc. of the RC columns are analyzed. The studying results proved that this strengthening measure for RC columns is superior to make the strengthening effect notable, working behavior of strengthened column excellent, strengthening construction easy and economical.

DOI:

10.14359/18287


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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