R. Sieniawska

LIFE EXPECTANCY OF HIGHWAY BRIDGES DUE TO TRAFFIC LOAD

Abstract In this paper the life expectancy of highway bridges to traffic flow is studied. It is assumed that the traffic is a composition of different types of vehicle models. Each type of vehicle is modeled by one or more concentrated random forces. In this idealization the vehicles are regarded as being of random weight and traveling with the same constant speed. The interarrival times of the vehicles are regarded as random variables. For estimation of the life expectancy of the structure one needs to find the joint probability density function of the displacement, velocity and acceleration of the vibrating beam. In the paper the damage process of the bridge is determined by the Palmgren-Miner rule. As an example, the covariance function, the spectral density function and the life expectancy of a bridge modeled as a simply supported beam are determined.

Vibrations of the beam due to a load moving with stochastic velocity

The aim of this work is to give an approach for obtaining the probabilistic characteristics of the beam response due to a load moving with stochastic velocity. It is assumed that the load is modelled by a set of point forces of random amplitudes, the inter-arrival times are random variables that constitute the Poisson stochastic process and the forces are moving along the beam with velocities that are also stochastic. The effective solution in such a case can be obtained by applying the Ito integral and the Ito differentiation rule. In this paper, the theoretical basis for such an approach is given. Analytical expressions for calculating the probabilistic characteristics of the beam response and numerical results are shown.

Reliability Analysis of Elastic-Plastic Frames under Wind Load

An approach for calculating the reliability of elastic-plastic frames loaded statically by the dead load and snow and dynamically by the wind is presented. It is assumed that the wind is described by the Gaussian stochastic process. The algorithm is based on the kinematic formulation of the shakedown problem and random vibration analysis. Structures reliability is regarded as the probability of no failure. For calculating the reliability the FORM and SORM reliability methods built in the STRUREL system are applied.

Optimization of absorbers in the highway bridges due to traffic flow

The problem of reducing the level of vibrations in various constructions is considered for many years and numerous ways and means of preventing unacceptable vibrations are known [1]. One of this ways are various vibration absorbers. Their application play a special role because they can be used during the construction design and also when unsatisfactory dynamic properties appear in a construction during operation. Absorbers are applied in various engineering structures such as shipbuildings, steel chimneys, TV towers, bridges [2, 3], etc. Vibrations of some of this structures are excited by load of random nature. In this cases damped vibration absorbers (DVA) are used to mitigate the random excitation [3] and their parametres are optimized on the condition of the main mass’s. The minimum variance of the displacement corresponds to the maximum reliability of the system. The traffic flow is such type of load which causes complicated stress and displacement states in bridges and also causes the material fatigue that ultimately can damage the structure. The application of absorbers can greatly extend its lifetime.