# Economic Superiority of PIP Slip Joint Compared to Conventional Tubular Joints
## 2 Methodology
### Definition and Characteristics
Another pivotal cost parameter is welding cost, which can significantly influence the initial cost. Welding material costs can vary widely based on several factors, including the type of materials used, the welding process, and the specific requirements of the project. Here is a breakdown of different welding material costs:  
* Base Metals: The cost of the base metal is a significant factor in welding expenses. For instance, in one paper, S420 ML steel is used, which is a structural steel that meets specific standards. The price of structural steel can fluctuate based on market conditions, availability, and the specifications required for the project [42]. * Filler Materials: Filler materials, such as welding wires or rods, are essential for many welding processes. For example, the use of HTW-58 welding wire--known for its specific mechanical properties and chemical composition--has been documented in previous studies [43]. The cost of filler materials can vary based on their type, diameter, and manufacturer. Generally, higher-quality filler materials that match or exceed the properties of the base metal may come at a premium. * Shielding Gases: In processes like CO\({}_{2}\) gas-shielded arc welding, the cost of shielding gases is an important consideration. The price of gases such as argon, carbon dioxide, or mixed gases can vary based on purity, supplier, and regional availability. These gases are crucial for protecting the weld pool from contamination during the welding process [44]. * Consumables: Other consumables, such as flux, electrodes, and protective gear, also contribute to the overall material costs. The choice of consumables can depend on the welding process and the specific requirements of the job [45]. * Surface Preparation Materials: Before welding, surface preparation may require additional materials, such as cleaning agents or heating equipment. Surfaces are typically heated before welding, which may involve costs related to heating equipment and fuel usage, as documented in prior studies [46]. * Post-Welding Treatment Materials: After welding, materials for stress relief, inspection, and finishing may also incur costs. These treatments are essential for ensuring the integrity and performance of the welded structure [47]. * The loading factors for the different joint types were carefully extracted from a comprehensive analysis of a 15 MW wind turbine design, ensuring a robust foundation for our engineering approach [23]. Following that study, the average monthly wind load over 7 years at Buan (an offshore site in South Korea) was used, as per Figure 2[24]. * Accurate and comprehensive data acquisition forms the foundation of reliable wind economic modeling. This section presents a detailed description of the raw dataset and experimental conditions employed in the present study. The primary source of data is the Korea Meteorological Administration (KMA), which offers long-term offshore wind and wave observations. These datasets encompass critical meteorological and oceanographic variables, including wind speed, wind direction, air temperature, wave height, wave period, and water temperature, all recorded with high temporal resolution. * Table 1 summarizes the key characteristics of the wind dataset utilized, acquired from the Buan offshore monitoring station in Korea. Wind measurements were taken at a height of 10 m above mean sea level with a temporal resolution of 10 min, enabling high-frequency monitoring. Wind speed and direction were captured using ultrasonic anemometers mounted on automatic weather stations (AWS) and buoys, with measurement accuracies of \(\pm\)0.3 m/s and \(\pm\)3\({}^{\circ}\), respectively. Air temperature data, recorded by AWS, exhibited a precision of \(\pm\)0.1 \({}^{\circ}\)C, ensuring dependable meteorological input. The extended data record spanning from 2017 to 2023 provided a robust basis for developing an economically optimized wind energy model. Please note that in Table 1, TI is measured turbulence intensity in % and St. Dev.