THE USE OF STEEL FIBRE CONCRETE IN SEISMIC DESIGN OF FRAMES

This is the second and final part of a paper published in the 1982 October issue of the New Zealand concrete construction. Tests made on two-beam column assemblies, and two beams of different lengths were designed to simulate very severe earthquake loading. Details are given of the tests and instrumentation used. Results with the conventionally reinforced concrete beam-column assembly demonstrated the need for adequate shear reinforcement. It was shown that fibre reinforcement within the beam-column joints significantly improved the shear resistance by increasing toughness and ductility. However there appears to be a need for some additional conventional shear reinforcement in a joint core to withstand intense cyclic loading. The inclusion of fibre in the joint core restricts inclined tension cracking to the joint core diagonals. The load carrying capacity of the column through the joint core is maintained. Steel fibres in the plastic hinge regions of reinforced concrete beams improves the ductile performance at ultimate load. Shear-induced diagonal tension cracking in beams can be almost eliminated with adequate fibre reinforcement. However, conventional beam stirrups may be needed to prevent splitting of the concrete along vertical cracks which might occur after tensile yielding of the main reinforcement. (TRRL)