Yielding oscillator under triangular ground acceleration pulse

An analytical solution is presented for the response of a bilinear inelasti c simple oscillator to a symmetric triangular ground acceleration pulse. Th is type of motion is typical of near-fault recordings generated by source-d irectivity effects that may generate severe damage. Explicit closed-form ex pressions are derived for: (i) the inelastic response of the oscillator dur ing the rising and decaying phases of the excitation as well as the ensuing free oscillations; (ii) the time of structural yielding; (iii) the time of peak response; (iv) the associated ductility demand. It is shown that when the duration of the pulse is long relative to the elastic period of the st ructure and its amplitude is of the same order as the yielding seismic coef ficient, serious damage may occur if significant ductility cannot be suppli ed. The effect of post-yielding structural stiffness on ductility demand is also examined. Contrary to presently-used numerical algorithms, the propos ed analytical solution allows many key response parameters to be evaluated in closed-form expressions and insight to be gained on the response of inel astic structures to such motions. The model is evaluated against numerical results from actual near-field recorded motions. Illustrative examples are also presented.