Comparison of Shear Capacity of T-Beams Using Strut and Tie Analysis

Abstract

The objective of this research was to study the shear strength of continuous lightly reinforced concrete beams which are widely used in practice in North America. In 1990 six two-span T-beams were tested at the University of Kansas. The research was focused on the primary variables of longitudinal reinforcement ratio and nominal stirrup strength. The tests indicated that the shear provisions of ACI 318-89 overpredicted the concrete shear capacity of lightly reinforced beams in negative moment regions, and underestimated the stirrup contribution to shear strength which increases with higher flexural reinforcement ratios. These experimental results were reevaluated and analyzed with the shear provisions obtained from existing codes and theories from Europe and Canada including EC 2, DIN I 045, CEB Model Code 1990, ACI 318-95, and Modified Compression Field Theory. In addition a Strut and Tie analysis for these tests also was conducted. The study indicates that the shear strength may be determined by Strut and Tie approaches with variable inclination e of the compression field based on the theory of plasticity to derive the interaction between bending moment and shear . The comparison shows that the shear capacity based on a clear truss model and the theory of plasticity gives results that correspond to the experimental results and lead to an economic design. Moreover, the results of this study also reveal the limitation of the present ACI provisions and show that codes formulated on a rigorous theoretical foundation provides excellent results when compared the test data.