Modal Analysis of Bridge Structure Using Finite Element Analysis

Abstract

The objective of the research study is to model a bridge with four different material using ANSYS software and to perform a modal analysis of bridge problem. For all four materials eight node solid element is selected and meshing is done individually for each modal. The material property of each material is selected as per literature database in ANSYS software. The modal analysis in ANSYS is performed to obtain the natural frequency and mode shapes of bridge to avoid the resonance of the bridge. Broquet et al. (2004) describe in a paper the dynamic behavior of deck slabs of concrete road bridge. This research interesting in dynamic analyses of bridges. The finite element method was used to study the local dynamic effects of traffic actions on the deck slabs. Advanced numerical models were described and the results of a parametric study presented. The bridge was represented by a shell element model and the vehicle by lumped masses, assembled in a nonlinear damped system. Important parameters that influence bridge vehicle interaction were taken into account, to investigate characteristic properties of the dynamic behavior of the bridge deck slabs of concrete bridges and to deduce the distribution of dynamic amplification factors throughout the deck slab. The vehicle was excited by irregularities of the road surface, generated by using power spectral density function. Experimental studies (Wolek 1992) have indicated that present methods of analysis underestimate impact and, thus, the dynamic effect for many structures. Since so many variables play a significant role in the generation and control of the total response, it is essential that bridge designers develop a better understanding of the dynamic behavior of bridge structures and the physical characteristics and parameters that affect response. II. Material Properties The dynamic material properties for the road-bridge as well as for the adjacent ground are vital information for the study of the road-bridge. Parameters concerning the soil characteristics are taken from the database that was formed during previous studies which were aimed of ensuring adequate vibration levels. By choosing the parameters according to that database it was easier to equate the results with research made previously. The database enclosing material data for the studies also contains information about suitable parameters for concrete and other materials such as asphalt.In Table 2.1 the material parameters which are used in the modelling are displayed. The quantities displayed in Table 2.1 are the materials density ρ (kg/m3), Young's modulus E (MPa), Poisson's ratio v (−).