Sensitivity of modal parameters of multi-span bridges to SSI and pier column inelasticity and its implications for FEM model updating

Abstract

Modal parameters, determined through forced vibration testing, ambient vibrations or seismic excitations, are central to the structural health monitoring process for bridges. These parameters are used to obtain highfidelity numerical models through FEM model updating by fine-tuning mass, stiffness and boundary conditions and matching the numerical and observed modal parameters. This study investigated sensitivity of modal parameters to changes in boundary conditions (soil-structure interaction effect) and pier column inelasticity (stiffness effect) through more than 450 non-linear dynamic time-history analysis of an ordinary multi-span bridge. The bridge system was founded on shallow foundations in five rock profiles and on pile foundations in five soil profiles and was subjected to 21 seismic ground motions of varying intensity (0.036 to 0.61g). Modal frequencies showed sensitivity to the SSI and pier column inelasticity effects for low and higher levels of seismic excitations respectively. Mode shapes, on the contrary, were insensitive to SSI as well as pier column inelasticity for all levels of seismic excitations.

The Current Development of Structural Health Monitoring for Bridges: A Review

“…They used FEM to detect and verify the contribution of SSI in altering the dynamic response of continuous viaducts. Chaudhary [200] studied the extent to which SSI and pier column inelasticity variations affect modal parameters under different horizontal seismic excitations, aiming to provide a higher fidelity FEM. During seismic excitation experiments conducted on pile foundations established in five soil profiles, modal frequencies demonstrated a sensitivity to the effects of SSI and pier column inelasticity, which was not reflected in the mode shapes.…”

Estimation of structural stiffness with the use of Particle Swarm Optimization

“…Model update methods are usually based on experimentally obtained modal model parameters or frequency response functions (Maia and Silva, 1997;Heylen et al, 2007). Updating the finite element model is an important and actual problem (Wang et al, 2018;Zhang and Hou, 2018;Batou and Nabarrete, 2018;van Ophem et al, 2018;Rakshit and Khare, 2019;Chaudhary, 2020;Hu et al, 2021). An analytical approach may require a high quality and complete experimental model which may need to be expanded to allow the least square approach for the FEM update.…”