Steel structures are the preferred choice for constructing office buildings due to their efficiency and cost-effectiveness, the ability to create large open spaces, and the speed of construction. Considering the advantages of steel and design concepts for office buildings—such as modularity in both horizontal and vertical directions, minimum clear height for offices, and room depth limitations to ensure natural lighting—a steel office building has been designed in the Osijek area. The building has a rectangular floor plan and consists of two stories, each with a height of 4.00 meters. The structural system comprises five unbraced frames connected by secondary beams. The structural elements of the internal frame have been dimensioned and are also adopted for the external frame. Primary and secondary beams are constructed from steel IPE profiles, while the columns are made from steel HEB profiles. The inter-floor structure consists of a reinforced concrete slab supported by secondary beams, acting as a rigid diaphragm that ensures lateral stability of the secondary beams. To assess the impact of joint behavior on the global analysis of the structure, a unilateral connection between the column and beam and a bilateral connection between the column and beam were dimensioned using the component method. The fundamental characteristics of these connections were implemented into the global structural model to analyze their influence on the distribution of shear forces and deformations. The static calculation was performed on a planar model, and the behavior of the structure was verified using a spatial model with the SCIA Engineer software.