This book encapsulates the state-of-the-art advancements and methodological innovations in structural and geotechnical engineering using OpenSees, as detailed by esteemed international scholars and practitioners at the 6th Eurasian Conference on OpenSees (EOSD), held in Beijing, China, on June 24-25, 2024. The event, following a two-day course with more than 100 attendees, was dedicated to examining recent progress and applications within the OpenSees framework. The book delves into a spectrum of topics, such as the deployment of OpenSees in structural and geotechnical projects, the development of novel computational elements and materials models, and enhancements in the software’s pre and post-processing capabilities that improve simulation accuracy and user interaction. Each paper is rigorously vetted through a comprehensive international peer-review process, ensuring the inclusion of high-quality, impactful research. The technical content presented extends beyond mere applications, offering detailed discussions on the integration of new numerical modeling techniques, the validation of complex material models under seismic loading, and the optimization of simulation workflows for enhanced scalability and efficiency. Moreover, this book serves as a critical resource for identifying emerging research trajectories and facilitating partnerships among experts in OpenSees.