Angelidakis V (2016)
Publication Language: Greek
Publication Type: Thesis
Publication year: 2016
Publisher: National Technical University of Athens
City/Town: University repository
Near-fault ground motions are of interest to the structural engineer, as they tend to put large inelastic demands on structures. Inside the Near-Fault zone ground motions are influenced by the rupture mechanism and the directivity phenomena. In this thesis an investigation is implemented, concerning the effect of directivity pulses on the inelastic behavior of a curved RC bridge. A sample of 90 near-fault seismic records is selected, containing 55 records that were classified as pulse-like ground motions by Baker (2007) and 35 seismic records from European and Eastern seismic events, containing at least one significant velocity pulse. The first 6 pulses are extracted from each record, using the method proposed by Mimoglou et al (2014), in which the mathematical representation of the pulses inherent in the ground motion is given using the wavelet proposed by Mavroeidis and Papageorgiou (2003) and their periods are computed from the peaks of the product spectrum Sd × Sv (ξ = 5%). Superpositioning the N first pulses, 6 synthesized accelerograms are constructed per record, as the sums of the first pulses.
Subsequently, the effect of the pulses is examined on the behavior of a real, existing structure. In this Case Study, the Bridge G7 of Egnatia Highway is employed, which is simulated in OpenSees (McKenna et al, 2000). Implementing a Static Pushover Analysis to the Longitudinal axis of the structure, the capacity curve is derived, which is transformed to an ADRS capacity spectrum of an equivalent SDOF system and it is brought to an idealized elastic-perfectly plastic form. Having the yield acceleration (ay) and the period of the equivalent SDOF system (T∗) computed from the Bi-Linear capacity spectrum, each record is scaled for three intensity levels, so that the developed behavior factor for the original records is equal to q=2, q=3, q=4. The Scaling is carried out using the elastic acceleration spectra of the original records (ξ=5%). The structure is then subjected to Non-Linear Time-History Analyses for the original records and the synthesized accelerograms that form from the superpositioning of the N first pulses for the 3 scalings. The frequency domain in which the maximum response is observed is then identified and the response results for the superpositioning of the pulses are compared to those for the original records. The comparison is performed calculating the errors for various general and local response quantities for the original records and the synthesized sums of the first pulses. Observations are given concerning the sign and the value of the errors over the ratio T∗/Tp1, where Tp1 is the period of the first velocity pulse. The moving average is then calculated for the errors of each response quantity, scaling and sum of first pulses and the number of the pulses that suffice to keep the error under an accepting threshold of 25% is found.
APA:
Angelidakis, V. (2016). Investigation of the near-fault directivity pulses’ effect on the inelastic behavior of a curved RC bridge (Master thesis).
MLA:
Angelidakis, Vasileios. Investigation of the near-fault directivity pulses’ effect on the inelastic behavior of a curved RC bridge. Master thesis, University repository: National Technical University of Athens, 2016.
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