Abstract
The dynamic behaviour of large and complex structures largely depends on damping resistance in the structure. A portion of the structural energy is lost to deformations in material, friction between the contact surfaces, and relative motion within the structure. Often, in an analysis of numerical models, before the dynamic analysis of transient events (transient analysis), the damping resistance is adopted on the basis of recommendations, which implies an error of transient response (introduced by frequencies, logarithmic decrements and maximal amplitudes). Decreasing amortized vibratory movement is dependent on the extent of the structural damping. This paper presents the importance of structural damping in structural analysis and shows the experimental and theoretical procedure for identifying G values of the structural damping coefficient. A model for determining the G coefficient is shown in the example of a real tower crane structure. The experimentally obtained values were then used in the transient numerical FEM analysis, as the basis for adopting the conclusions about the dynamic behaviour of this class of structures (transportation machines). The effect of the external perturbation force of trapezoidal impulse form (lifting and quickly lowering of load) is introduced and the dynamic task, as an example of the use of the G coefficient G, is solved. The experimentally determined damping (theoretically isolated for tall truss structures) can be used in similar transient analyses.
Highlights
Building sites with large construction machinery structures are very numerous and widespread today
An understanding of the dynamic behaviour of the support structures for such machinery will minimize the negative impact caused by improper handling, random events and force majeure
The support structures of cranes are tall and heavy, and they can be defined as complex truss structures due to different shapes and properties of the elements
Summary
Building sites with large construction machinery structures are very numerous and widespread today. The coefficient of proportionality is named the viscous damping coefficient This coefficient is determined by defining the material properties of the elements forming the model for numerical analysis. According to the recent literature, aerodynamic damping is used in dynamic analysis of the tall truss structures [13] This type of damping of truss structure vibrations occurs with the motion of wind in the direction of the longitudinal axis of the tower. A parallel observation of free vibrations of the structure for different values of the structural damping coefficient G in numerical models enables the determination of the real structural damping on basis of the experiment.
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