A Comparative Study on FBD and DBD Methodology with Emphasis on Bridges with Seismic Irregularity

Abstract

One of the major developments in seismic design over the past few decades is the increased emphasis for limit states design now generally termed as Performance Based Engineering. Performance Based Seismic Design (PBSD) uses Displacement Based Design (DBD) methodology where-in structures are designed for a target level of displacement rather than Force Based Design (FBD) methodology, where-in force or strength aspect is used. Indian codes still follow FBD methodology compared to other modern codes like CalTrans, which follow DBD methodology. Hence in the present study, a detailed review of the two most common design methodologies i.e. FBD and DBD will be discussed, along with its comparison on bridge models with and without ‘seismic regularity’. Bridges with irregular column height are studied to discuss the inherent discrepancy associated with FBD while dealing with ‘seismic irregularity’.