Irregularities and Roughness

The periodically repeated pavement irregularities and their effect on the dynamic behavior of a bridge are the subject of this paper, as well as a new point of view of how the surface roughness operates on vehicles. The authors observed that the models used so far accept that the wheels are always in contact with the roughness curve. But in reality the wheels only come in contact with the peaks of the roughness curve by applying impact forces. The theoretical formulation is based on a continuous approach that has been used in literature to analyze such bridge. The procedure is carried out by the modal superposition method, while the obtained equations are solved by using Duhamel’s integrals. Important conclusions for structural design purposes can be drawn through a variety of numerical examples

Inclined cable-systems in suspended bridges for restricting dynamic deformations

The present paper deals with the influence of the inclination of cables' system on the decrease of the lateral-torsional motion because of dynamic loadings. For this goal, a mathematical model is proposed. A 3- D analysis is performed for the solution of the bridge model. The theoretical formulation is based on a continuum approach, which has been widely used in the literature to analyze such bridges. The resulting uncoupled equations of motion are solved using the Laplace Transformation, while the case of the coupled motion is solved through the use of the potential energy. Finally, characteristic examples are presented and useful results are obtained. © 2017 Techno-Press, Ltd

Analytical treatment of in-plane parametrically excited undamped vibrations of simply supported parabolic arches

The present work offers a simple and efficient analytical treatment of the in-plane un-damped vibrations of simply supported parabolic arches under parametric excitation. After thoroughly dealing with the free vibration characteristics of the structure dealt with, the diffierential equations of the forced motion caused by a time dependent axial loading of the form P = P-0 + P-t cos thetat are reduced to a set of Mathieu-Hill type equations. These may be thereafter tackled and the dynamic stability problem comprehensively discussed. An illustrative example based on Bolotin's approach produces results validating the proposed method

The Influence of the Load Model and other Parameters on the Dynamic Behavior of Curved-in-Plane Bridges

This paper deals with the dynamic behavior of curved-in-plane bridges where the effect of the bridge curvature radius, the moving load (vehicle) speed, the truck cant angle, the deck surface conditions and, mainly, the response accuracy depending on the vehicle model used are investigated. Besides the above parameters, the influence of several loading models is studied as well, especially the models of a concentrated load, a damped mass-load, a sequence of two concentrated loads and a real vehicle aswell as a damped vehicle,where its width is taken into account. A 3-DOF model is considered for the analysis of the bridge, while the theoretical formulation is based on a continuum approach, which has been widely used in the literature to analyze such bridges

The effect of infinitesimal damping on the dynamic instability mechanism of conservative systems

The local instability of 2 degrees of freedom (DOF) weakly damped systems is thoroughly discussed using the Lienard-Chipart stability criterion. The individual and coupling effect of mass and stiffness distribution on the dynamic asymptotic stability due to mainly infinitesimal damping is examined. These systems may be as follows: (a) unloaded (free motion) and (b) subjected to a suddenly applied load of constant magnitude and direction with infinite duration (forced motion). The aforementioned parameters combined with the algebraic structure of the damping matrix (being either positive semidefinite or indefinite) may have under certain conditions a tremendous effect on the Jacobian eigenvalues and then on the local stability of these autonomous systems. It was found that such systems when unloaded may exhibit periodic motions or a divergent motion, while when subjected to the above step load may experience either a degenerate Hopf bifurcation or periodic attractors due to a generic Hopf bifurcation. Conditions for the existence of purely imaginary eigenvalues leading to global asymptotic stability are fully assessed. The validity of the theoretical findings presented herein is verified via a nonlinear dynamic analysis