## 1 Introduction  
The consideration of actual welding processes can have an impact on the complexities and uncertainties involved in the Finite Element Analysis (FEA) of structures. FEA utilizes welding models to approximate the effects of the welding process. However, these models may not accurately replicate the actual welding process, resulting in discrepancies between FEA results and the actual welded structure. Determining accurate welding parameters for FEA analysis can be challenging, especially in the case of complex welded structures. Welded joints may possess different material properties compared to the base structure. FEA typically assumes constant material properties, which may not accurately represent the variations in material properties caused by welding. The welding of multiple components can influence the stiffness and natural frequency of the structure. To address these limitations, it is crucial to refine the welding models employed in FEA and validate them using testing data. Additionally, conducting iterative testing and adjusting parameters based on experimental data can enhance the accuracy of FEA analysis for structures with multiple welded components. Numerous vehicle owners opt to modify or alter their registered vehicles. However, in the absence of proper control or supervision to ensure compliance with automotive engineering principles and appropriate safety standards, this can pose a threat to both the vehicle owner and other road users. Additionally, such modifications may create opportunities for illegal activities. Therefore, it is essential to establish specific criteria to permit vehicle modifications or alterations to ensure compliance with international standards and guarantee safety. The Land Transport Act of B.E. 2522 (1979) is among the regulations that Thailand has utilized to define the following terms [1]:* Land transportation refers to the transportation of people, animals, or goods by road using vehicles. * Regular transportation refers to transportation for hire on routes designated by the Transport Committee. * Small-scale transportation refers to transportation of people or goods, or a combination of both, for hire on routes designated by the transport committee, using vehicles with a combined weight of no more than 4000 kg. * Personal transportation refers to transportation of goods for one's own business using vehicles that weigh more than 2200 kg. * A pickup truck is defined as a vehicle that has a solid, box-shaped section for carrying cargo with a permanent roof. The cargo area and the driver's compartment may be integrated together or separated, and there may be doors for loading on the side or rear. It is classified as the second type of vehicle used for transporting animals or goods from among the nine types. The regulations cited in this passage include the Vehicle Act (No. 3) of B.E. 2525 (1982), as well as Sections 12 and 14 of the Vehicle Act, B.E. 2522 (1979), and Section 4 of the Land Transport Department Regulation on Criteria for Requesting and Granting Permits for Modified Vehicles under the Vehicle Act, B.E. 2562 (2019). According to these regulations, \"vehicle\" refers to personal cars and motorcycles, \"chassis\" refers to the original manufacturer's framework that supports the weight and cargo of the vehicle, and \"body\" pertains to the driver's seat and passenger compartment, but excludes the cargo area. Vehicles that have undergone reinforcement, modification, or installation of additional parts are considered to be unlawfully altered, specifically pickup trucks. Nonetheless, this can be rectified by informing the Department of Land Transport where the vehicle is registered about the modification. Failing to report such modifications would be considered a breach of the Land Transport Act of B.E. 2522. As of September 30, 2022, the total number of trucks in Thailand was 1,217,179. Compared to September 30, 2021, there was an increase of 397,122 trucks that are not fixed-route, representing 32.63% (an increase of 5.57%).