###### Abstract  
This paper presents a study on the modelling and estimation of stress concentration at the tips of leg stiffeners in ship-to-shore (STS) quay cranes, which is intensified in those on the sea-side leg extensions, which are more prone to crack formation, notably following structural heightening of the cranes. A computer-simulated database was generated, incorporating mechanical parameters and geometric features that impact stress concentration. These variables can then be integrated as inputs into a multiple linear regression model (MLR). This methodology offers an alternative to the finite element method (FEM) for the computation of stress concentration and deformations. At the same time, the statistical significance of the parameters influencing this scenario is determined, ensuring a comprehensive assessment of their impact on the studied phenomenon. The research underscores the importance of incorporating stress concentration and structural geometry considerations into crane design or modification, given their crucial role in preserving the remaining lifecycle of the structure. Crack initiation is significantly intensified in regions characterised by high stress concentrations, particularly in areas where there are geometric changes at the tips of the stiffeners, where local stiffness is altered. All of this is in combination with work cycles under the supported loads. m 2024 20  
worldwide to accommodate mega container vessels with increasingly wider beams and greater draughts. Consequently, it becomes imperative to modify the quay cranes to suit these colossal vessels through a meticulous and sophisticated engineering process involving their expansion and adaptation. In recent years, the maritime industry has witnessed a significant surge in the size and capacity of mega container ships, prompting necessary adjustments in port infrastructure, notably ship-to-shore (STS) cranes. As these cranes are structurally raised to meet the growing demands of larger vessels, novel challenges arise regarding stress distribution and concentration, particularly at critical areas, such as the tips of internal leg stiffener zones. Stiffened plates are composed of several stiffeners and the attached plates, and they serve as fundamental structural elements in ships and marine installations [2; 3]. Therefore, an accurate assessment of their strength is essential for ensuring overall structural safety. Several studies have been carried out to assess the capacities and behaviours of stiffened plates [4; 5; 6]. However, due to the structural complexity and stringent safety standards of structures, experimental approaches are vital for evaluating their ultimate load capacities  
This work explores the crucial need to understand and model stress concentration phenomena computationally at these critical points within STS quay crane legs. The heightened structural configuration, prompted by the changing maritime port environment, underscores the importance of this study in ensuring structural integrity, operational efficiency, and safety in port operations. The structural heightening procedure involves cutting the legs and attaching plates with stiffeners, as illustrated in Figure 1. This structural raising of the cranes has introduced new challenges related to the distribution and concentration of stress, particularly in critical areas such as the tips of internal leg stiffener extensions. Addressing similar problems, [PERSON] et al. (2016) [7] presented research on developing strength equations for internally ring-stiffened circular hollow section (CHS) tubular DT-joints. [PERSON] et al., (2018) [8] and [PERSON] et al., (2018) [9] studied different collar plate joints using the finite element method (FEM) modelling. In the work of [PERSON] et al. (2023) [10], experimental laboratory tests on eight plate girders with thin webs and two transverse stiffener configurations revealed that the real axial compression and bending moments in the stiffeners are significantly lower than those prescribed by the standard.