Composite Beams with Partial Interaction under Sustained Loads

Abstract

The paper presents the derivation of a theoretical model for the time‐dependent response of simply supported steel‐concrete composite beams. The concrete is modeled on a computer using the age‐adjusted effective modulus method, and slip at the steel‐concrete interface is included. The theory is compared with test results reported elsewhere, and the agreement is shown to be good. The comparison is for deflections up to 250 days from loading, and for section strains that include interfacial slip. Slip strains are calculated in the time‐dependent domain using the computer model. It is shown that the slip strains are increased by the interaction of creep, shrinkage, and connector modulus, but their absolute values are still reasonably small at service loads. The computer model forms a basis for deriving design rules, and lends itself to extension to continuous composite beams and slabs. The analysis is presented in a form that may be applied to other models for predicting the time‐dependent response of the concrete.