Heavily loaded long-span beams, such as ceiling substrings, bridge girders, as well as frame structures are designed as I-beam or box-shaped plate girder elements. The walls of plate girders loaded in their plane may lose their stability due to their significant slenderness. A common method of securing the web against local loss of stability is the use of longitudinal and / or transverse stiffeners. Due to the inability to automate the welding process of the stiffeners, they have to be manually welded, which is very labor-intensive and costly. Therefore, in the research team of the Department of Engineering Structures, Gdańsk University of Technology, an innovative idea was developed to increase the web stability of a bent plate girder by increasing the wall thickness in the compression zone. This approach requires one additional butt weld along the entire element, which is technologically simpler, cheaper and faster (due to the possibility of full automation of production) compared to manual welding of each stiffener. Moreover, the weight of the structure would not change as the material for the longitudinal stiffener would be used to thicken the web. Such a solution has not been used so far. As part of the pilot studies, experimental and numerical tests of a bent plate girder beam with a variable web thickness are planned. It is planned to perform destructive tests on two-point bending plate girder beams in two geometric variants. During the experimental tests, the values of the critical load and the limit load will be determined. Moreover, strains and displacements at selected measurement points will be measured. The results of the experimental research will be used to validate the numerical model using the finite element method (FEM). The analyzes of subsequent buckling modes will form the basis for determining the equivalent computational imperfection. Its purpose is to take into account all possible technological and geometric imperfections of the tested beam, which are random character. The results of the study carried out as part of this project will allow to introduce an innovative construction solutions in the field of steel structures, confirming a significant role of Gdańsk University of Technology as development of innovative solutions.