The Earthquake Engineering Online Archive

Cyclic behavior of three reinforced concrete flexural members with high shear

Popov, Egor P.; Bertero, Vitelmo V.; Krawinkler, Helmut

UCB/EERC-72/05, Earthquake Engineering Research Center, University of California, Berkeley, 1972-10, 78 pages (530/P65/1972)

The behavior of three large reinforced concrete cantilever beams is discussed in this report. The beams were 15 in. by 29 in. in cross-section and all had six #9 deformed bars for longitudinal reinforcement at the top and bottom. The shear reinforcement differed in size and spacing for each specimen. With heavy longitudinal reinforcement and small cantilever length (78 in.), high shearing forces were transmitted simultaneously with the bending moments. The principal objective of this investigation was to study the effects of the high shear forces on deformation, strength, stiffness and energy dissipation capacity of flexural members. The nominal shear stress at ultimate load was approximately equal to 6 square root f prime subscript c for all three specimens. The specimens failed in shear; and in the post-yielding range, shear-type deformations contributed significantly to the tip deflection of the cantilevers. These shear-type deformations led to a deterioration of the initial loading stiffness and consequently to a pronounced pinching of the hysteresis loops. The experiments showed that repeated reversed loading of flexural members leads to a deterioration in shear resistance. If the shear forces are high, this deterioration may lead to a shear failure at rather low flexural ductilities. For earthquake-resistant design, a reevaluation of the current ACI Code (1971) design equations for shear reinforcement (Section 11.6) seems, therefore, necessary.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-72-05.pdf (13 MB)