Influence of ductility of buried pavement nodes of structures at the impact limit value

Introduction. The literature review of research in the field of dynamic calculation of composite structures is carried out, which shows that research in the field of damping of dynamic impacts on coatings of buried structures is actual. At the same time, the issues of asymmetric impulse impacts remain insufficiently studied.

Materials and methods. A typical structural solution of a pavement slab of a buried structure subjected to impulse loading is considered. The deformation is modelled in the volumetric formulation by the finite element method. The dynamic effect is represented as a set of scaled time functions. This type of modelling allows the variable impact point and the change in impact intensity to be taken into account. The physical non-linearity of the materials is taken into account based on plasticity models of the fibre concrete and reinforcement. The JWL model was used to determine the initial load moment.

Results. Limits of dynamic load corresponding to the pre-failure state of the structure were determined. The thickness of the pipes used as damping inserts in the support nodes was varied. A series of calculations were carried out with different thicknesses of damping (crumpled) inserts under asymmetric impulse loading. The equivalent stresses according to the energy theory of strength were considered as time-observed parameters for symmetrical reinforcement of the transom parts of the slab. A comparison was made with previous studies dedicated to the calculation of the slab for symmetrical impacts.

Conclusions. The high efficiency of the use of damping inserts was established, and the highest value of the dynamic ultimate load in comparison with a rigid bearing unit and a solid pipe was obtained with the thickness of the inserts equal to 9 mm. Prospects and further research directions are defined.

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