The direct connection of column splices using partial joint penetration groove welds with a penetration percentage between 40% - 60% of the thickness of the column section was common until the Northridge and Kobe earthquakes. With the poor performance of beam-to-column welding connections after the Northridge earthquake and column splice welding connections after the Kobe earthquake, new design details and executive instructions were added to the regulations and the use of partial joint penetration (PJP) welding in moment frame structures was prohibited and designers were required to use complete joint penetration (CJP) welding (AISC 341-10). With experimental and numerical studies conducted on PJP welding with a higher penetration percentage in I-shaped sections, the possibility of using PJP welds with a penetration percentage of 85% was confirmed in the regulations (AISC 341-16). All previous studies were conducted on the behavior of PJP groove welds in I-shaped sections. in this study, a 3D finite element numerical model was simulated in Abaqus software in order to investigate the behavior of the column splice and the failure and spread of damage in the Heat Affected Zone (HAZ). By ensuring the proper performance of the finite element model, 33 box-shaped column splices have been modeled, and the effects of parameters such as penetration weld percentage, column thickness and cross-sectional dimensions on the column splice behavior has been evaluated.