Analysis of Vertical-to-Horizontal Spectral Acceleration Ratios for Shallow Crustal Ground-Motion Records in Taiwan
Date Issued
2016
Date
2016
Author(s)
Chiu, Li-Chun
Abstract
Seismic design of structures often focuses on the demand from horizontal ground motions; however, the impact of vertical ground motions can be significant for seismic responses of ordinary buildings, highway bridges, and isolation systems. A practical procedure to determine vertical design spectrum is to scale a PSHA-based horizontal design spectrum using a vertical-to-horizontal ratio (V/H). Many seismic design codes (such as IBC and ASCE 7-10) specify a constant value of 2/3 for V/H at all periods. However, there are evidences that the V/H ratios might be greater than 2/3 in the short period range. This study explores the V/H ratios for shallow crustal ground motions in Taiwan and evaluates the adequacy of modern ground-motion models and the requirements of current Taiwan building code on V/H. Pulse-like near-fault ground motions may cause significant damage to structures. This study analyzes the V/H ratio of pulse-like near-fault ground motions recorded worldwide and in Taiwan to understand the regional differences of the ratio. Seven sets of ground-motion prediction models and two relatively simple models were used to predict the V/H ratios for ground motions in different databases of this study. The residuals between the predicted and recorded V/H values were computed and analyzed using both statistic approach and Sammon’s Map, which is a high-dimensional visualization technique to map the high-dimensional space data into a two-dimensional space. The results were used to evaluate the pros and cons of the application of the models on Taiwan data.
Subjects
vertical-to-horizontal spectral-acceleration ratio
shallow crustal earthquake
pulse-like
near-fault ground motion
ground-motion prediction equation
Sammon’s Map
Type
thesis