The Significance of Vertical Shaking on Seismic Assessment of Gravity Dams: A Case Study

Abstract

Vertical motions' effects have recently been recognized in building codes. The corresponding effects on infrastructure components is less certain. Current industry practice ignores vertical shaking based on earlier recommendations obtained using linear analyses. The goal of this study is to assess this suggestion for a case study and investigate the significance of the use of vertical motion, along with the horizontal component, during the seismic assessment of dam structures. A 50 m concrete dam monolith was used to this end and the effects of the vertical motion was assessed for two groups of engineering demand parameters (EDP). Such displacement and crack based EDPs are commonly used in the assessment of gravity dams. The response of the chosen system with and without the contribution of vertical ground motion was obtained and compared. The results show an increase in the horizontal displacement and vertical acceleration on the system when vertical ground motion was used along with the horizontal, in lieu of the horizontal only shaking case. The cracking around the neck of the system can be significantly different with the use of vertical motion, both with regard to extension and distribution.