Modelling Behaviour of Bridge Pylon for Test Load Using Regression Analysis with Linear and Non-Linear Process

This paper presents the procedure for dynamic system identification regarding behaviour of bridge pylon for test load, and the numeric example had been illustrated by examination of "Sloboda" bridge in Novi Sad. Since pylon shifts, occurred during test load, were long-period in nature, static GPS method had been applied for measurements. To identify dynamic process of the construction, auto-regression model with external input (ARX) had been selected. The process had been approximated as linear and non-linear. Establishing model degree had been performed by autocorrelation function and parameter significance test. It had shown that the shifts of pylon along the longitudinal axis of the bridge, occurring due to the load action, must be described as a result of non-linear process; while shifts, occurring orthogonal to longitudinal axis of the bridge, occurring due to the temperature change, are the result of linear process. Model fitting was also analyzed, observing the pylon as both rigid and deformable body. Higher percentage of fitting (alignment) had been achieved when the construction had been viewed as a deformable body.