IF articles

Railway bridges seismic design and assessment of base isolation hypothesis

 

This document assesses the effects connected

with the adoption of seismic base isolators in railway

viaducts with reference to the “Cintura” viaduct (located

in the outskirt of Bologna High Speed/High Capacity

Milan-Bologna line), representative of the most common

structural types in the high speed railway system and

designed according to the 1996 Ministerial Decree (D.M.)

and the 44B Railway Directive in category II seismic zone.

The assessments were made by applying the new Technical

Norms for Constructions (NTC) and by conducting linear

and non linear dynamic analyses. Results obtained are

illustrated by following two design hypotheses: the first

hypothesis adopts the use of elastomeric isolators with a

lead core (lead rubber bearings - LRB), whilst the second

hypothesis adopts isteretic metallic isolators (Steel

Dampers). Results obtained show how the NTCs lead to

more severe control conditions on some structural elements

such as foundations and supports. The study highlights

how a strategy focusing on seismic base isolation

may have a high potential for success also in railway

viaducts, providing an efficient seismic performance is al-

 

so associated with a guarantee of a suitable performance

under non seismic conditions for the effects associated

with railway activity.

  • Novembre
2009
Num. 11
Pag. 937