CONSTRUCTIVE METHODS FOR INCREASING THE LOAD-BEARING CAPACITY OF CONNECTION JOINTS BETWEEN MAIN AND END GIRDERS OF BRIDGE CRANES

Purpose. To enhance the load-bearing capacity of the junction nodes between main and end beams of overhead cranes by improving diagnostic methodologies and developing structural reinforcement techniques for repair applications. Research methods. The stress state of junction nodes was investigated using the finite element method with adaptation of the hot spot stress approach to Ukrainian standards. Stress-strain analysis of the overlapping structure was conducted using sub-modeling techniques. Stress intensity factors were determined through the displacement method. Results. Based on statistical data analysis, a logit model was developed to determine the probability of junction node damage depending on overhead crane parameters. It was established that for butt joint structures, the most significant factors are operation intensity (coefficient 4.0) and service life (coefficient 2.05), whereas for overlapping structures, operation intensity is the dominant factor (coefficient 6.12). Stress state models were developed for nodes under vertical and transverse loads. It was discovered that increasing the gusset plate leg length does not have the expected effect on stress magnitude due to load redistribution between end beam elements. It was determined that reinforcing end beam webs can reduce stresses in the upper flange by a factor of 1.8. Structural methods for enhancing the load-bearing capacity of butt joint and overlapping structures were proposed. Experimental verification confirmed that when using an integrated approach (gusset plate, overlay, and cut-out) for overlapping structures, the maximum effective stresses in the cut-out zone are 60 MPa. Scientific novelty. New data were obtained regarding the influence patterns of structural parameters of junction nodes between main and end beams of overhead cranes on their load-bearing capacity. Relationships between crack length and fracture toughness parameters were established, enabling prediction of the residual service life of junction nodes. Practical value. The developed structural methods for enhancing the load-bearing capacity of junction nodes provide sufficient safety margins against high-cycle fatigue and improve the operational safety of overhead cranes.