Title:
Behavior of Corbels with External Prestressing Bars—Experimental Study
Author(s):
Krystyna Nagrodzka-Godycka
Publication:
Structural Journal
Volume:
96
Issue:
6
Appears on pages(s):
1033-1039
Keywords:
corbels; external prestressing; strengthening; ultimate load.
DOI:
10.14359/780
Date:
11/1/1999
Abstract:
This study presents experimental data of the reinforced concrete corbels that, after cracking, were strengthened by external prestressing or passive (nonprestressing) steel bars. The purpose of the experimental tests was to recognize the influence of external bars on cracking and on the load carrying capacity of the tested specimens. Nine corbels with various shear span-effective depth ratio (a/d) were tested. The degree of prestress determined by the value of the prestressing force was assumed constant for all three tested prestressed specimens. To recognize the effect of prestressing, the test results of the prestressed corbels were compared with test results of the ultimate load and cracking of corbels without strengthening, and also with corbels strengthened by external bars—the same as the prestressing bars but without external prestressing. Such passive bars are often used to strengthen overloaded and cracked reinforced concrete (RC) corbels. It turned out that the effectiveness of external prestressing bars was significant, particularly for corbels with greater value ratio (a/d ª1.0). External prestressing is a useful solution for strengthening corbels and reducing their crack widths. Until now, there has been no recognition of crack morphology and the load carrying capacity of cracked corbels strengthened by external prestressing bars. The results of the experimental tests also show that the truss analogy, or shear-friction theory used for designing, in practice cannot be applied (without modification) to the proper determination of the ultimate load of the RC corbels strengthened by external bars.