The advancement of society has led to an increase in demand for infrastructure, particularly bridges, which are designed in accordance with different design codes. In Sweden, bridge design adheres to the Eurocode and national code (TRV specifications), with the most adverse scenario of the two codes determining the basis for bridge design. The process of designing a bridge according to both codes and subsequently comparing them necessitates a prolonged design duration, resulting in an increase in project costs. This thesis explores the possibility of determining multiplication factors αM and αV for the bending moment and shear force respectively, which would enable the direct transition from the most unfavourable load case in the Eurocode to the worst one in the TRV specifications. Thus, the bridge can be modelled based on the most conservative of the two. The study concentrates on portal frame bridges ranging in length from 6 to 25 m, with a 1 m step between each case study and expanding from 1 to 4 traffic lanes. The FEM software "Brigade/Plus" was used to analyse the portal frame bridges, with the key internal forces being the longitudinal bending moments and shear forces in the deck slab. The analysis of the different models showed that bridges with four lanes had αM increasing according to a quadratic relation while αV increased linearly. In the case of three-lane bridges, only one value of αM was greater than one. In conclusion, the analysis indicated that the Eurocode is more conservative for short-span bridges of up to three lanes and less conservative for four lanes above a span length of 16 m.