Correlation Between Seismic Energy Demand and Damage Potential Under Pulse-Like Ground Motions

An energy-based perspective can provide a more rationalway for quantifying the damage potential in structures subjected to strong ground shakings as compared to traditional displacement-based methods. This is basically due to the possibility of accounting for maximum deformation and cumulative damage simultaneously. Unlike typical far-field ground motions, where the input energy is progressively accumulated over time, near-fault records often impart sudden and intense energy demands to the structural systems by means of distinctive velocity pulses. These abrupt energy spikes force the structures to dissipate the input energy through few large plastic cycles, thereby imposing high values of the deformation demand within a short time window. Since most of the structural damage in this case is related to the seismic demands during this short duration, viscous and hysteretic energies accumulated at the end of the ground motion mainly depend on the contribution of a few significative peaks occurring in the early phase of the response. This paper thus introduces new energy-based intensity measures for pulse-like seismic ground motions. Consistent correlations are presented between the proposed intensity measures, the ground motion characteristics, and a representative engineering demand parameter (i.e., the maximum inter-storey drift). Towards this objective, an extensive database of nonlinear dynamic analyses is compiled for a set of sixty near-fault records to simulate the seismic response of reinforced concrete structures representative of the Italian residential buildings portfolio ranging from two to ten storeys in bare frame configurations. Machine learning techniques are finally implemented to find general, yet accurate and robust, correlations between a suite of seismic intensity measures and demand potential.