Effects of fling step and forward directivity on seismic response of buildings

• Published in: Earthquake spectra Vol. 22; no. 2; pp. 367 - 390
• Main Authors: Kalkan, Erol, Kunnath, Sashi K
• Format: Journal Article
• Language: English
• Published: Oakland, CA Earthquake Engineering Research Institute 01-05-2006
• Subjects: amplitude; buildings; cyclic loading; damage; data bases; data processing; Earth sciences; Earth, ocean, space; earthquakes; Earthquakes, seismology; elastic waves; Engineering and environment geology. Geothermics; Engineering geology; Exact sciences and technology; failures; faults; ground motion; Internal geophysics; loading; mathematical models; Natural hazards: prediction, damages, etc; seismic response; Seismology; structures; velocity; waveforms; steel; damage; spectra; cycles; ground motion; velocity; faults; acceleration; seismic response; amplitude; buildings; dispersion; waveforms; energy
• ISSN: 8755-2930; 1944-8201
• DOI: 10.1193/1.2192560

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.