Restrained cargo dynamics in road transportation: direct tiedowns Online publication date: Mon, 10-May-2004
by J.A. Romero, A. Lozano, S. Rakheja, A.K.W. Ahmed, H. Hong
International Journal of Heavy Vehicle Systems (IJHVS), Vol. 11, No. 2, 2004
Abstract: A model is proposed to study the dynamic response and effectiveness of direct tiedowns under longitudinal decelerations. Two independent legs of the securing tiedowns are considered in the model, and tiedown elasticity is represented by an equivalent longitudinal stiffness as a function of the material, tiedown angle and geometry, assuming negligible initial tension. The contribution due to initial tension and variations in the orientation of tiedowns are incorporated in the model as external forces acting on the secured cargo. The cargo-deck friction force is further derived assuming ideal properties on the basis of resultant normal loads under the influence of vertical trailer vibration. A nonlinear single degree-of-freedom model of the restrained cargo is developed and analysed to study the cargo displacement responses as functions of initial tension, orientation of the tiedown, tiedown material, cargo-deck friction, nature of trailer vibration and magnitudes of constant deceleration. The results of the study revealed nearly linear cargo displacement response with the magnitudes of deceleration and vertical vibration. The cargo displacement response varies considerably with the tiedown angles, and cargo-deck friction coefficient in a nonlinear manner. The effective resistance of the restraints is further dependent upon the vertical vibration frequency and natural frequency of the tiedown system. Tiedown angles exceeding 45° yield considerably larger cargo displacement, specifically under trailer vibration.
Online publication date: Mon, 10-May-2004
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