Keywords: near-fault ground motions, artificial excitation functions, inter-plate and intra-plate earthquakes.

Near-fault ground motions are characterised in the case of inter-plate earthquakes, by pulse actions with large periods and velocities, and moderate ones in the case of intra-plate earthquakes. Examining the velocity records of many near-fault earthquakes, the ground velocity and pulse period are connected on the basis of the formula of Krawinkler et al. [1] with some corrections for small pulse periods. Firstly the pulse period depends on the earthquake magnitude. The same relationship exists between ground motion velocities and pulse periods.

Using the main characteristics of near-fault ground motions, some researchers have proposed simple models of pulse shapes that describe these ground motions. The velocity function was performed by Menun and Fu [2], but calculating the displacement and acceleration functions from it, we find some problem in them. Therefore we suggested the new possibility of modelling the velocity pulses to use algebraic functions [3], which have the same maximum of velocity and the same period as the function of Menun and Fu, but the displacement and acceleration functions are compatible with the velocity function.

We calculated the acceleration response spectra from our artificial excitation functions of the case of different magnitudes. The magnitudes were changing between 5.5 and 8.0. The large differences were in the values in the time of the motion (5.25 s and 0.88 s) and maximum of the velocities (605 and 14.1 cm/s). The maximum of the ground accelerations were 1.0 g and 0.15 g. We found that the period when the maximum of the spectrum is larger than the Eurocode value, depends on the magnitude. The ratio of the maximum acceleration and the zero period acceleration is also larger than in the Eurocode (3.46 > 2.5). It is very interesting that there are periods, when the values of the spectra at a smaller magnitude are larger than in the case of the larger magnitude.

The results obtained for structure response, when this is subjected to the near-fault ground motions, show important differences in comparison with the code provisions, especially in the case of inter-plate earthquakes, characterized by large velocities and long pulse periods.

1

H. Krawinkler, R. Medina, B. Alavi, "Seismicity drift and ductility demands and there dependence on ground motion", US-Japan Seminar on Advance Stability and Seismicity Concepts for Performance-Based Design of Steel and Composite Structures, 2001.

2

C. Menun, Q. Fu, "An analytical model for near/fault ground motions and the response of SDOF system", Seven U.S. National Conferences on Earthquake Engineering, Boston, 2002.

3

J. Györgyi, V. Gioncu, M. Mosoarca, "Behaviour of steel MRFs subjected to near-fault ground motions", In F.M. Mazzolani, A. Wada, (Editors), "STESSA 2006, Behaviour of Steel Structures in Seismic Areas", 129-136, Yokohama, Japan, 2006.

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