ABSTRACT
The increase in road and railroad transport cargo, especially in Brazil, with increased intensity values of loads on the roads, has been producing degradation in many bridges throughout the countries. This is an issue of paramount importance, as is related to the structural health of bridges and with the matter of the conservation of highroads and railway structures.
The movement of a vehicle on the bridge is already, in itself, a dynamic action on the structure. However, the track irregularities tend to excite the vehicle dynamically which in turns triggers additional vibrations in the bridge structure besides those produced by its own movement. This condition tends to increase the degree of damage of the structure, further intensifying the nonlinear dynamic responses in terms of displacements, velocities, accelerations and strains in comparison to linear dynamic models, especially at critical speeds of the vehicle, capable to provoke some resonance. The approach developed in this study treats this phenomenon uncoupled. This study aims to analyze the vehicle-irregularity dynamic interaction of a reinforced concrete bridge, through the Finite Element Method, considering the stiffness loss of the bridge by Damage Mechanics.
The track irregularities are represented by random and sinusoidal harmonic functions and also compared to the case of no irregularities. The highway bridge analyzed has four supports and two overhanging spans. In its model are used Euler-Bernoulli beam elements, with Hermite cubic interpolation functions. The passage of the accelerated vehicle with one degree of freedom in the different forms of irregularities generates stresses that are transmitted to the highway bridge in uncoupled way. Firstly the computational routine analyzes the forces generated by the coupling between vehicle and irregularities and transmits them to the bridge for the desired analysis. It is a model coupled between vehicle and irregularities and uncoupled between the coupled vehicle-irregularities and the highway bridge.
Effects of physical nonlinearities occur by the fact that the forces do not linearly depend from the 487displacements according as damage to the material takes place. To differentiate the behavior of the concrete to traction and compression is used the Mazars Damage Constitutive Model, implemented with the condition of stress inversion due to vibration. The structural damping is defined by the Rayleigh method. The equations of motion are obtained by nonlinear dynamic equilibrium and numerically integrated in time using the Newmark Method in conjunction with the iterative Newton-Raphson Method. This works seeks to evaluate the dynamic effects produced in a structural model on which the degree of damage is altered over time. Example illustration and its boundary conditions. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig267_1.tif"/>
