He considered the issues of designing welded metal span structures of railway bridges with lattice trusses. A short history of bridge building, history of welding application in bridge building and modern level of railway bridge building in Russia are covered. The classical method of calculating forces in the rods of trusses using influence lines is briefly described, and the modern computer method of calculating forces in rods using finite elements (FEM) is given. The FEM method allows to simulate a volumetric rod structure as a single three-dimensional system loaded with a system of external forces, which create the resulting deformations, stresses and movements in the rods of the farm units. The book also contains descriptions of new patents on the shape of rods and farm units. The book will be useful for bridge designers and manufacturers, as well as bridge engineering students. This book has been translated with Artificial Intelligence.