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Earthquakes and Structures
  Volume 8, Number 1, January 2015 , pages 185-204
DOI: https://doi.org/10.12989/eas.2015.8.1.185
 


Influence of ground motion selection methods on seismic directionality effects
Cristina Cantagallo, Guido Camataa and Enrico Spaconeb

 
Abstract
    This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.
 
Key Words
    directionality; ground motion; nonlinear time history analysis; angle of incidence; reinforced concrete structures; ground motion scaling
 
Address
Cristina Cantagallo, Guido Camataa and Enrico Spaconeb: Engineering and Geology Department, University
 

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