Angelidakis V (2014)
Publication Language: Greek
Publication Type: Thesis
Publication year: 2014
Publisher: National Technical University of Athens
City/Town: University repository
The ground motions at near fault sites are of great interest for the structural engineer, as they may put extreme inelastic demands on structures. Near the fault, the ground motions are influenced by the rupture mechanism and the so called directivity phenomena. In this undergraduate thesis are investigated the effects of near fault directivity to the inelastic response of reinforced concrete frame structures. At first, the phenomenon of near fault directivity is described, along with geometric parameters of the rupture mechanism and the magnitude of the seismic event that have been correlated to the dominant periods of the significant pulses of the ground motion. The characteristics of the velocity pulses that may be inherent in a ground motion are of interest, so that one can describe their shape and classify the ground motion as “pulse like” or “non pulse like”, accordingly to its “pulse like” content. For that purpose, the quantitative classification method of Baker (2007) is described, in which the significant pulses of a ground motion are identified and extracted through wavelet analysis. Next, is described the classification method that is used in this thesis, as it is introduced by the researchers P. Mimoglou, I. Psycharis, I. Taflampas (2014), in which the significant pulses of a ground motion are extracted through wavelet analysis and the pulse periods Tp are determined by the peaks of the convolution spectrum Sd×Sv, for 5% damping, while the mathematical presentation of the pulse is described by the wavelet used by Mavroeidis and Papageorgiou (2003). Another method for the classification of near fault ground motions to “pulse like” and “non pulse like” is described, as it is introduced by the researchers V. Kardoutsou, I. Taflampas, I. Psycharis (2014), in which the “pulse like” content of a ground motion is correlated to the ratio Sd,0(Tp)/CAD, where Sd,0(Tp) corresponds to the value of the elastic response spectrum of the displacement for the dominant pulse period Tp and 5% damping, while CAD corresponds to the recently introduced Cumulative Absolute Displacement (Taflampas et al. 2009), for a part of the ground motion and the pulse period Tp is determined by the peak of the convolution spectrum as well.Then, the classification of 314 records is implemented, using the aforementioned method of Mimoglou et al. (2014). This set of records is found in the NGA (Next Generation Attenuation project) database of strong ground motions and corresponds to the earthquake of Northridge (1994). The classification is performed using the first dominant pulse of each record and one is classified as “pulse like” if the correlation coefficient of the pulse with the original motion is over 0.65 and the peak ground velocity of the original motion is PGV > 30cm/s. Remarks are given concerning the sites and the directions at which “pulse like” motions occur. The “pulse like” content of the records that are categorized as “pulse like” is then confirmed using the method proposed by Kardoutsou et al. (2014). In sequel, two reinforced concrete 3D frames are designed according to the Eurocodes, using the software FESPA 10 by LH Logismiki. These structures are simulated using the software of linear and nonlinear analyses SAP2000 v15.2.1 by Computers and Structures, Inc. in which they are subjected to static and time history nonlinear analyses. Ten “pulse like” and five “non pulse like” seismic records from the Northridge earthquake (1994) are then chosen to be applied as base excitation to the aforementioned structures in non linear time history analyses. Remarks are given concerning the inter-storey drifts, the dactility and the ductility – reduction factor ratio (μ/qy) for the “pulse like” records and each structure, in comparison to the ratio of the equivalent SDOF systems periods of the structures, to the dominant pulse periods (T/Tp).
APA:
Angelidakis, V. (2014). Effect of near-fault directivity to the inelastic response of reinforced concrete frames (Diploma thesis).
MLA:
Angelidakis, Vasileios. Effect of near-fault directivity to the inelastic response of reinforced concrete frames. Diploma thesis, University repository: National Technical University of Athens, 2014.
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