Strength of hollow circular steel sections filled with fibre-reinforced concrete

Abstract

The strength of hollow circular steel sections filled with normal-strength plain concrete and fibre-reinforced concrete (FRC) was evaluated. First, the case of centrally loaded composite members was considered and the bearing capacity of the columns was calculated using the methods proposed by a European code (EC4) and an American code (LRDF). Some expressions in these codes were validated for the case of FRC by adapting experimental data to introduce the mechanical properties of the FRC. To do this, experimental results of standard tests on FRC (compression and splitting tension) were used as well as data on circular steel columns filled with 2% FRC by volume with different types of fibres (steel, polyolefin). Second, the moment - axial force diagrams for composite members, taking into account the residual tensile strength of FRC, were calculated, showing the advantages of using FRC compared with plain concrete for filling hollow steel sections.Key words: fibre-reinforced concrete, hollow steel columns, composite members, steel fibres, polyolefin fibres.