Numerical modelling and strut-and-tie concepts for seismic design and assessment of pre-cast two-column bents

Abstract

Precast structures are more common in zones not affected by earthquakes or affected by low - to moderate-intensity earthquakes; the application of precast structures in zones of higher seismic intensity is unusual due to the seismic performance uncertainty of these structures. Concerning precast bridges, special attention needs to be paid on the column to cap-beam connections, as well as the methods to anchor the column longitudinal bars into the cap beam or foundation. The constructability of these joints often becomes unworkable due to the high reinforcement concentration that current standards require. Moreover, some design rules are rather unclear and the link to the flow of forces in the joint is sometimes lost. In this paper, to ensure a clear understanding of the forces flow, strut-and-tie concepts were applied to design a column-to-cap-beam joint region of a viaduct located in southern Europe. In addition, different ductility classes were considered. Emphasis was given to nonlinear numerical models developed to validate the strut-and-tie models as well as to evaluate the two ductility scenarios performed. As a modeling strategy, a rotating smeared crack approach was considered; also, constitutive models with fracture energy were considered to simulate the concrete mechanical behavior. Numerical results will be further validated through an experimental campaign planned to assess the structural performance of the designed solution.