Development of Earthquake-Resistant Design Guidelines for Bridges in Sri Lanka

With recent seismic events in and around the island, Sri Lanka can no longer be deemed safe from seismic threats. Currently, there are no specific seismic design guidelines available for bridge design in Sri Lanka. Therefore, this study aims to formulate earthquake-resistant design guidelines for bridges in Sri Lanka. To formulate these design guidelines, the study proposes a classification of bridges into three distinct importance classes. This classification draws from relevant categorizations found in comparable codes such as EN 1998–2:2005, IS 1893–3:2014, and AS 5100.2–2004. The proposed importance factors and return periods are based on the guidelines outlined in EN 1998–1:2004. Furthermore, the study suggests the adoption of an elastic response spectrum for rock or hard soil based on available data specific to Sri Lanka. For medium and soft soil types, it is recommended to utilize the response spectrum available in IS 1893–1:2002. This choice is grounded in the similarity between soil and rock types in countries situated on the same tectonic plate. The study introduces a seismic analysis approach for bridges, offering the option to use either EN 1998–2:2005 or AS 5100.2–2004. Additionally, it proposes suitable design parameters, including peak ground acceleration values, to be selected based on the available national data. Three case studies were conducted to exemplify the application of the developed guidelines for bridges in different importance classes. These case studies utilized the design codes of AS 5100. 2–2004, IS 1893–3:2014, and EN 1998–2:2005. Notably, When Eurocode 8-part 2 served as the basis of analysis, both the fundamental mode method and response spectrum analysis yielded similar results in terms of fundamental period and base shear values. Given the flexibility provided by Eurocode 8-part 2 to incorporate national choices, this developed guideline with national parameters stands as a viable option for seismic bridge design in Sri Lanka.