Abstract
Sensitivity of modal parameters of multi-span bridges to SSI and pier column inelasticity and its implications for FEM model updating
Highlights
Structural characteristics of a bridge in the modal domain are the key parameters that can be used to infer structural parameters of a bridge system subjected to forced vibration testing, ambient vibrations or seismic excitations through system identification procedures
The relatively small variation in Coordinate Modal Assurance Criteria (COMAC) values (0.92 – 0.97) in the bottom 2 m region of the pier column was indicative of relative sensitivity of COMAC to detect changes in modal properties caused by variations in boundary conditions (SSI effect) and/or stiffness of the pier column
The study presented results of more than 450 non-linear dynamic time-history finite element method (FEM) analysis of ordinary multi-span highway bridges founded on shallow foundations in rock profiles and pile-group foundations in soil profiles
Summary
Structural characteristics of a bridge in the modal domain (i.e. frequency, mode shapes and damping ratio) are the key parameters that can be used to infer structural parameters of a bridge system subjected to forced vibration testing, ambient vibrations or seismic excitations through system identification procedures. Many times, the acquired modal data is utilized to calibrate a FEM numerical model for carrying out parametric studies involving various scenarios of damage or for using it as a benchmark for future testing and evaluation (Friswell & Mottershead, 2013) This process, termed FEM model updating, is focused mainly around fine-tuning three parameters, i.e. mass, stiffness and boundary conditions. Focus of this study was to numerically investigate the influence of two parameters that are fundamental to the FEM model updating procedure for multispan bridges i.e. SSI and pier column inelasticity Effect of these parameters on changes in modal frequencies and mode shapes of ordinary, multi-span highway bridges was investigated through a non-linear FEM numerical model. Results and conclusions of the study delineated the relative importance of SSI and pier column inelasticity on variation in modal properties of the bridges and provided a heuristic guidance for FEM model updating of the type of bridges studied
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