The structure of a steel portal frame developed by us, which eliminates the disadvantages and inconsistencies of the above-mentioned known solutions concerning both I-section columns and transoms connected to them. A steel portal frame consisting of two columns and two transoms crowning them, bolted together and forming a gable profile, the columns and transoms are made of openwork one-sided tapering I-sections, the webs of which in the axis of symmetry, their width and along their entire length are made profile through holes symmetrically located in relation to each other, and moreover, these columns are positioned so that they have variable stiffness, increasing from the bottom - of the foundation of the building structure to the transoms, which also have variable stiffness increasing from the upper faces of these columns to the ridge connection according to the invention is characterized by in that the webs of both the one-sided converging I-sections of the columns and the webs of the one-sidedly tapered I-sections of the rafter have perforation with a variable geometry of their openings with the same profile but with decreasing transverse dimensions in the direction of the one-sided convergence of these mullions and transoms, while the openings profiles the web perforations are trapezoidal openings of identical heights situated symmetrically to each other at identical distances between each of these two openings, and the distances between the side walls of the openings and the internal walls of both flanges of these I-sections are unchanged. It is also advantageous if the openings constituting the perforations in the webs of the one-sidedly tapered I-sections of the columns and the rafters connected detachably thereto are made directly in the axes of symmetry of these webs. The use of steel portal frames of the structure according to the invention for the construction of a production hall or hangar with the use of one-sided tapering I-sections, whose webs have symmetrically positioned quadrilateral openings with variable widths with identical distances between the side walls of these openings and both shelves of these I-sections, made it possible to reduce the amount of structural steel and the weight of the entire structure of this frame, and allowed the use of girders of this portal frame up to 30 m. In addition, the structure of these portal frames with such perforation in one-sided converging webs of I-beams significantly improved the architectural qualities of the building, giving the impression of its lightness, allowing at the same time, the free passage of various installation cables through these openings in the space occupied by the gable roof and the columns of this portal frame. The tests carried out using computer simulations and static-strength calculations showed that the portal frame made of openwork one-sided converging I-sections is characterized by a large margin of load capacity, i.e. up to about 30%, which allows increasing the load on the load-bearing system, and at the same time installing additional equipment in the production hall without the need to change type of openwork profiles. In addition, the implementation of symmetrically spaced openings in the webs of one-sided tapering I-sections with dimensions according to the invention allows their use in power networks, especially as load-bearing elements of their equipment.