Accuracy of AISC Methods in Predicting Flexural Strength of Concrete-Encased Members

This paper investigated the accuracy of the AISC analysis methods in determining flexural strength of concrete-encased members. Analytical results from analyses performed using the AISC methods and a proposed method were compared with test data for 32 specimens. Results from this study showed that the method of superposition of elastic stresses and method of plastic stress distribution on the steel section alone overly underestimated flexural strength of the concrete encased composite members studied herein. On the other hand, the method of plastic stress distribution on the composite section, the method of strain compatibility, and the proposed method well predicted flexural strength of the encased composite members including members without shear anchors, suggesting that composite action can be developed in encased composite members without shear anchors when sufficient confinement is provided by transverse reinforcement. In addition, studies of effects of longitudinal and transverse reinforcement on flexural behavior of encased composite members were conducted to identify crucial parameters. The parameters examined herein included reinforcement ratio, steel flange area, steel shape depth, and transverse reinforcement spacing. Implications and recommendations drawn from the studies are discussed.