11.27: Elastic buckling load and load resistance of core‐separated assembled BRB confined by two concrete‐infilled tubes

Abstract

This paper presents a novel type of the core-separated assembled BRB (CSA-BRB). It consists of two single BRBs confined by concrete-infilled tubes that are connected longitudinally by two continuous webs. This directly results in a sectional cavity of the CSA-BRB by spacing two independent BRBs, and significantly enhances its cross-sectional flexural stiffness and loadcarrying capacity. The two independent steel cores of the CSA-BRB are strengthened and connected at its end with a core stiffener to form a robust H-shaped sectional core, as a whole. The core stiffener is inserted into the restraining member by a distance, further remarkably improving the core strength and stiffness at un-restrained core projections of the CSA-BRB. The CSA-BRB is simulated approximately by "an equivalent framed model" and accordingly its elastic buckling load was obtained by using an equilibrium method. A number of numerical examples of CSA-BRBs were designed and investigated by using a large deflection elastic-plastic beam element model to predict the influence of the restraining ratios on their load-carrying capacities. An overall geometric imperfection with the amplitude of l/1000 at mid-span of the CSA-BRB is also involved in the analysis. The results obtained reveal that the CSA-BRBs could achieve required load-carrying capacity without overall failure, considering the strain hardening (for example 0.02E) of the core after its initial yielding, as well as the ultimate axial compressive strain of 2% applied to the core if the restraining ratio of CSA-BRBs is greater than around 3.0.