Design of Experiments Study to Obtain a Robust 3D Computational Bridge Model

Ambient traffic vibration tests for the three continuous span bridge were conducted to investigate the dynamic response of the bridge in order to identify the natural frequencies and the mode shapes. Understanding the dynamic response of the bridge in its existing, unretrofitted condition is the starting point for developing confidence in the computer model because the same model will evolve from the existing bridge to the retrofitted bridge. A robust 3D computational model is developed using design of experiments (DOE) techniques. Extensive full factorial experiments are carried out to determine simultaneously the individual and interactive effects of many factors such as concrete density, concrete modulus of elasticity and steel modulus of elasticity that could affect the natural frequencies of the bridge. Data is processed to derive natural frequencies and modes shapes, which are remarkably consistent over the range of experiment conditions. ANSYS is used to complete the finite element model and analysis. In the DOE each factor is given two values. The set of allowable model factors which causes the model to match the tested natural frequencies and mode shapes are presented in this paper.