Characteristics of Horizontal and Vertical Near-Field Ground Motions and Investigation of Their Effects on the Dynamic Response of Bridges

Abstract

Recently, concerning failure of structures due to earthquakes, special investigations of near fault ground motions have been noticed. Hence, in this paper, characteristics of near field ground motions have been considered in horizontal and vertical directions. In this consideration, the record averages have been compared with Uniform Building Code and Eurocode8 spectra in two levels. In addition, the ratio of vertical to horizontal spectra has been computed and compared with the assumed value of two thirds in some code provisions. Finally, the response of near field records on five artificial bridges that have covered all 0.5-2.5 seconds periods, have been investigated for comparing the ratio of responses in near field to far field, and forward to backward directivity effects. In addition, the results of the response spectrum analyses of six different bridges subjected to vertical excitations are presented.

Keywords

• horizontal spectrum
• vertical spectrum
• near field
• forward directivity effect, filing step, ubc 97, eurocode 8