Importance of spatial variability of seismic ground motion effects on long beams response

Nourredine Mezouer¹*, Kamel Silhadi² and Hamid Afra³

¹National Earthquake Engineering Research Centre (CGS) 01, Rue Kaddour Rahim, BP 252, Hussein Dey, Algiers, Algeria.

²Ecole Nationale Polytechnique, 10 Avenue Hassan Badi, BP 182 El harrach 16200 Algiers, Algeria.

³Centre National d’Etudes et de Recherches Intégrées du Bâtiment Cité El Mokrani, Souidania, Algiers, Algeria.

*Corresponding author. E-mail: mezouer_n@yahoo.fr. Tel: 00 213 771 910 654.
Fax: 00 213 21 495 536.

Accepted 16 November, 2009

    Abstract

Rigorous seismic analysis of long structures requires a complete description of the free field ground motion. At a given site, the recorded motions at distinct points are different; this may induced by loss of seismic wave’s coherency, wave passage effect, site response effect and attenuation of seismic waves. In this paper, the effects spatial variability of ground motion (SVGM) on the stochastic response of structures subjected to this phenomenon (wave propagation and incoherence), using response spectrum method are analysed. The responses are evaluated along a two-span beam. After detecting the critical sections, the responses at these sections are studied in more details according to the fundamental period of the beam. SVGM have beneficial effects on displacement of structure founded on stiff soil and unbeneficial effects in presence of soft soil. The interplay between dynamic and pseudo-static responses may either control how the spatial variability ground motion excitation effects are favourable or not depending on different sections along the two spans beam and the rigidity of the soil.

Key words: Spatial variability, mean maximum response, two-span beam, soil, fundamental period.