A fibre model to simulate the cross-sectional behaviour of reinforced concrete columns under multi-directional earthquake loading

The sense of direction and the magnitude of horizontal ground accelerations due to earthquakes are not constant, but are variables within the duration of an earthquake. Furthermore, varying vertical ground accelerations appear. As a result, columns of reinforced concrete space-frame structures suffer multi-directional and time-variable excitations during earthquakes. To analyse the structural response to those excitations more accurately, a fibre model describing the nonlinear behaviour of reinforced concrete cross-sections under multi-directional actions is presented. Diagrams showing yield force couples and corresponding plastic curvature capacity as well as a computer program to calculate ε,κy,κz↔N,My,Mz interaction for free force- and displacement-combinations are developed.