Dynamics and damage in the Quisi steel truss bridge

Quisi Bridge located in Benissa (Alicante) is an historic steel truss structure, which is investigated with different techniques to assess fatigue damages. A method based on vibration measurements, is illustrated to determine defect-induced reduction of stiffness, (combination of damage intensity and extension). Natural frequency change for a structural damage in a truss member is quantified through a classical FEM procedure in which a damaged truss element is defined and implemented. This model is used to produce pseudo-experimental response of a damaged truss which is dynamically excited by white noise. Stochastic Subspace Identification (SSI) has permitted to identify the main modal parameters related to both damaged and undamaged truss system. A damage index depending on Stiffness Reduction Factor (SRF) permits to determine the damage description based on measured quantities.