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Calculation of joints

Equipment designing

Calculation of guy chain joint of covered skating center in Krylatskoye

Destruction of guy chain axis of the covered skating center in Krylatskoye resulted in the need to carry out a comprehensive analysis of failure causes.
Hexa Company performed a range of nonlinear static calculations for the connection point of links in the guy chain based on initial data provided by the customer.

Finite element model. Connection point of guy chain. General view of finite element model Distribution of stresses in eyes

The model takes account of contact interactions between all parts in the structure of the joint. The interaction of plates between each other is also taken into consideration. The model has 350 thousand elements, 360 thousand joints and 37 contact pairs.
The calculation takes account of geometric nonlinearity (deformation of the structure) and physical nonlinearity (elasto-plastic properties of material).

Distribution of stresses in joint. Deformation scale 50

Distribution of shearing stresses in axis

It was found that maximum stresses in axis under design static load do not exceed yield point. Therefore, stiffness of the structure is ensured. However, one should not forget that axis material have been idealized in the calculation while real diagram «σ–ε» is different from that specified in the calculation. Real steel forged pieces of such large size (500 mm x 800 mm) cannot be made ideally. In addition, the larger the size of a steel part, the more defects it has. Designers should always take account of this fact.

In this case it is obvious that due to uneven crystallization of a large-size part, significant residual stresses have been generated in it. From experience it is known that residual stresses of compression act on the surface of cylinder, while tensile stresses act in the cylinder. As a result of shrinkage in presence of residual stresses, casting has radial cracks found on the surface of break in the destructed part.
There are cases when large-size parts are destructed under action of residual stresses even without any external load. Thus, non-critical for the structure external load in combination with high residual stresses may become a sufficient cause for crack formation and growth. The result is the structural damage.

Hexa Company to order of the State Unitary Enterprise Moscow Scientific-Research and Design Institute for Culture, Leisure, Sports and Health Care Buildings (GUP MNIIP MOSPROJECT-4), 2008

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