08.46: Local buckling of thin‐walled tubes encased in concrete

Abstract

Local buckling of concrete-filled tubes has been studied by several researchers these recent years, due to the evidence that the limits provided by the Eurocode for considering local buckling in steel tubular sections are non-conservative, especially when taking the confinement effect of concrete into account. In CFT (concrete-filled tube) sections, lateral pressure provided by concrete when loading both components at the same time leads to a reduction of stability of the cylindrical shell in terms of local buckling, since it is subjected to a vertical and lateral pressure. However, this phenomenon has exactly the opposite effect when the encased component is the steel tube; this is the case of concrete-encased tubes, a very interesting typology for its mechanical and fire response. In these sections, the encased tube is subjected to a uniform compressive pressure from outside that clearly enhances the stability of the shell; this study presents a numerical and analytical approach to local buckling in these sections, by using a complex numerical model calibrated with real thin and thick-walled previous experiments. The conclusions of this text pretend to describe the efficiency of these sections in terms of local buckling, and to fix the base for a wide experimental and numerical campaign to determine how each parameter may influence to the global response.