Seismic Performance Of Structures Under Vertical Ground Motion

Abstract

In the earthquake-resistant design of structures, emphasis has traditionally newlinebeen placed on the study of horizontal ground motions (HGMs), with less attention given newlineto vertical ground motions (VGMs). Despite this, the significance of VGMs has been newlineunderscored by field observations of structural damage resulting from the vertical newlinecomponents of seismic event in proximity to fault lines. This recognition within the newlineliterature underlines the necessity of incorporating the impact of vertical ground motion newlineinto seismic design practices to improve structural integrity and resilience. newlineInternational earthquake codes recommend a design-based ratio of peak newlinevertical to horizontal spectral acceleration for earthquakes, typically suggesting a value of newlineone half to two-thirds. Yet, empirical data from recorded earthquake motions of several newlinenear fault seismic events indicate that the actual peak vertical-to-horizontal acceleration newlineratio significantly exceeds the prescribed guidelines. This discrepancy highlights the need newlinefor a reevaluation of existing seismic codes to better reflect the observed dynamics of newlineearthquake ground motions, thereby enhancing structural design and safety. The newlineamplification of vertical loading effects is particularly pronounced in structures such as newlineconcrete gravity dams, those with plan irregularities, long spans, and large overhangs newlinesituated in proximity to fault zones. Near-source seismic events, characterized by high newlinevelocity and frequency, can induce vertical-to-horizontal peak ground acceleration (V/H) newlineratios exceeding unity, resulting in potentially catastrophic outcomes due to substantial newlinevertical accelerations. Notably, the literature lacks documented investigations on the newlinebehavior of structures with plan irregularities, concrete gravity dams, long-span steel gable newlineframes, and large overhang planar frames under vertical ground motion (VGM) in the newlineIndian context, indicating a significant gap in research. newline