## 2 Methodology
### Quayside Container Crane Safety Evaluation Index System  
A comprehensive and rational evaluation index system is essential for ensuring the accuracy, scientific rigor, and precision of equipment safety evaluations. Quayside container cranes are complex integrated systems, comprising multiple interdependent subsystems that work collaboratively to ensure the safe operation of the entire machinery. The risk sources for quayside container cranes primarily include equipment factors, human factors, and environmental factors. Equipment factors encompass the metal structure of the equipment, various mechanisms, and protective devices. Human factors include aspects related to operators and management. Environmental factors, such as typhoons and earthquakes, often exhibit strong randomness and uncontrollability. Based on the risk sources of gantry cranes, the safety evaluation index system can be divided into five parts: metal structure, main mechanisms and components, safety protective devices, electrical equipment, and operation and management. The index system is illustrated in Figure 1.  
The metal structure of a quayside container crane serves as the load-bearing system for all its components. It is fundamental to the crane's functionality and the primary stress-bearing part of the gantry crane. Damage or defects in the metal structure can impair the function of other parts, potentially leading to overall damage and serious safety accidents. Thus, the integrity of the metal structure is crucial for the overall safety of the gantry crane. The types of damage commonly found in the metal structure of gantry cranes can be categorized into insufficient local strength of structural components, inadequate stiffness in bending members, local deformation of plates, cracks in plates and welds, and metal corrosion. Accordingly, five indicators have been selected for assessing the safety of the gantry crane's metal structure: strength, stiffness, deformation, cracks, and corrosion. The strength indicator can be characterized by the maximum stress measured at the main load-bearing points under the rated load. Stiffness can be indicated by the deflection of the front beam under the rated load. Deformation can be assessed by local undulations. The crack indicator can be evaluated by the longest inspection cycle, and the corrosion indicator can be represented by the thickness of the corroded area of the plate. The normal loading and unloading operations of quayside container cranes are carried out through the coordinated function of various main mechanisms and components. The safety condition of this part significantly impacts the overall safety of the crane. This section primarily includes the hoisting mechanism, luffing mechanism, gantry travel mechanism, trolley travel mechanism, and hydraulic system. Under each of these mechanisms, there are components like brakes, reducers, couplings, bearings, pulleys, wire ropes, drums, and wheels. The hydraulic system includes components such as hydraulic pumps, hydraulic cylinders, hydraulic valves, and pipelines. Assessing the safety of these components and systems often cannot be characterized using quantitative data. Instead, it typically involves qualitative evaluations by experts, based on the specific conditions of each component and part. The safety protection devices of quayside container cranes are crucial for ensuring safety in the event of equipment malfunction or operator misconduct. These devices serve a crucial function in the safe operation of the equipment and in preventing accidents, effectively safeguarding the overall safety of the machinery. This section mainly includes  
Figure 1: Quayside Container Crane Safety Evaluation Index System. The figure was created using Microsoft Visio 2016.  
limit position limiters, load limiters, hatch cover protection devices, emergency stop devices, anti-wind skid devices, buffers, and other similar components. Like the main mechanisms and components, the safety of these protective devices and systems is challenging to quantify with data.