Abstract
This paper describes a problem related to a casting bridge crane with a combined load of 200/50/12.5 t and a span of 18.6 m, working in a heavy metallurgical operation. Due to the specific stress of the structure after its long-term operation, longitudinal fillet welds between the upper flange and the web of the main box beam on the rail side of the 200 t trolley were irreparably damaged. As a result, the cross-section of the main beam had opened, thereby substantially reducing its strength and stiffness. This resulted in a disproportionate increase and undesirable redistribution of stresses in the beam and, at the same time, an increase in the probability of acute fatigue or the loss of stability of the elastic beam shape. Therefore, the rectification of the damaged load-bearing structure was carried out by specific structural modifications. Critical load-bearing elements were subjected to complicated strength and fatigue life analyses before and after rectification. These analyses were supported by experimental measurements. The applied modifications resulted in a partial strengthening of the lifting device with the possibility of its further operation, but only in a limited mode, with a limited period of operation with a time limit of 2 years and a reduced total load capacity of 150 t. The applied methods are also applicable for the fatigue analysis of load-bearing elements and equipment for bridge, gantry and tower cranes, crane tracks, road and railway bridges and support structures under machinery and other devices with a dominant transverse and rotating effect.
Highlights
A serious and complex technical problem in steel structures is the assessment of their technical capability
It was subjected to analysis andProblem assessment of the condition of the load-bearing structure and the Solved accumulation of fatigue damage at the weld flange and the web under the crane rail on the main
The structure of a bridge casting crane working under conditions of heavy metallurgical
Summary
A serious and complex technical problem in steel structures is the assessment of their technical capability. Fatigue damage can affect the structural elements and structural nodes of load-bearing structures due to unsuitable structural design during manufacture or unsuitable additional structural modifications, e.g., overhaul (project design factors), failure to observe technological discipline during the manufacture or repair of the equipment (manufacturing technology factors), the intentional or unintentional use of the equipment in a manner inconsistent with its intended use, including the unavoidable effects of natural factors (streaming wind and water, tectonic movement of the Earth) or incorrect so-called non-prescribed maintenance (operational load factors) [7,8,9,10,11] Due to these factors, the real nature of the stress is far more unfavourable than expected in the design of the structure, and the direction, gradient, magnitude, or redistribution of stresses may change. The level of damage to the material and structural elements is characterised either by the level of internal energy, in particular at the concentration points, or by the volume fraction of the areas of material cohesion failure due to external or internal fatigue limit factors [26,27,28,29,30]
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