The Operation and Maintenance Building of Eurasia Tunnel in Istanbul is one of the most critical components of the Eurasia Tunnel, the road tunnel connecting Europe and Asia under Bosporus. The operation and maintenance building was architecturally designed by GMW architects, and by Intac Engineering for structural design. The seismic performance required for this structure, due to its importance and the importance of the tunnel as a critical facility, is “fully operational” for the case of a strong earthquake. Senso Engineering provided assistance and consultancy to Intac Engineering for performance based seismic design as well as for post-design validation of the building by using nonlinear dynamic analyses.