EFFECTS OF NEAR-FAULT EARTHQUAKES ON SEISMICALLY ISOLATED BRIDGES

H. Cem Yenidoğan

(Thesis Supervisor: Mustafa Erdik)

ABSTRACT

Bridges constitute one of the critical components of the modern transportation systems that need to be functional after major earthquakes. The seismic isolation method has been proposed as an innovative mature performance enhancement strategy to mitigate earthquake risks on bridges. This study aims to review the advances in the seismic isolation technology for bridge applications while assessing the suitability of isolation units in close proximity to active faults. Suite of ground motion sets with pulse and nonpulse contents were compiled from PEER and European Ground Motion Database.

Two multi-span continuous reinforced concrete bridges are adapted to this study by considering distinct nonlinear properties of three isolation systems. The critical appraisal is given to the curved surface spherical friction sliders together with the evaluation of their modelling assumptions in finite element programs. The first bridge example is utilized to perform comprehensive parametric investigations. In contrast, the second bridge example is a part of large-scale testing which requires to generate reliable analytic models for the Pseudo Dynamic(PsD) testing.

It has been concluded that the effectiveness of isolation systems in reducing the demand parameters of both bridge models are demonstrated by analytical models. The reliability of implemented analytical models of the Rio-Torto Viaduct were justified through the conducted PsD test. Extensive parametric investigations were indicated that the suite of pulse dominated near source ground motions with coupled vertical components not only led to increase in the demand parameters of isolation systems but also exceeds the code-mandated factors for MCE level earthquakes.