Rapid Seismic Assessment of Alaska Highway Bridges Using a Direct Displacement-Based Methodology

• Main Author: Cetinkaya, Mustafa Yavuz
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2019
• Subjects: Civil engineering
• ISBN: 165841201X; 9781658412018

The invention of ShakeMap (by USGS) has led to use of HAZUS post-earthquake assessment methodology (by FEMA) for rapid seismic assessment of bridge structures via ShakeCast (by Caltrans/USGS) with the aim of determining inspection priorities. The HAZUS approach was developed by using coarse limit state definitions for the purpose of assessing bridges with limited information, hence it is not ideal for assessment of bridges whose limit states can be identified more accurately with available bridge metadata. Utilizing ShakeMap, a simple and accurate seismic assessment procedure for the case where bridge details are known can be preferable in lieu of the HAZUS method to determine inspection priorities. In this research, the implementation of a displacement-based rapid assessment approach for Alaska highway bridges using ShakeMap is proposed. The approach is based on the direct displacement-based design (DDBD) methodology developed by Priestley et al. (2007), which allows for characterization of Multi Degree of Freedom (MDOF) structures by equivalent Single Degree of Freedom (SDOF) system properties (system displacement, damping and effective period) to a specified limit state. Limit state displacements of a set of bridges (three reinforced concrete and four reinforced concrete steel tube) from Alaska were identified at different performance levels. A scenario earthquake created from ShakeMap was used to check whether limit state displacements were achieved during a given earthquake scenario, which is an indication of damage level. An inspection priority list of the bridges based on the results of the direct displacement-based assessment (DDBA) approach was proposed. The accuracy of the DDBA was checked performing incremental dynamic analysis (IDA) with spectrum compatible records. The results of IDA indicate that the DDBA method provides satisfactory estimates of the performance level of a bridge under a given seismic hazard. Finally, DDBA application of the three bridges under the ShakeMap of a real earthquake is shown.