In this paper research work on welded butt weld connections between hot-rolled seamless tubes and steel castings are presented. Comparison is made between different weld preparations for the butt welds including different steel grades, repair methods, the influence of residual stresses and a study on large scale trusses. The steel grades investigated include S550QH as well as S690QH to complement previous test results on lower steel grades. These investigations are intended to lead towards the development of a concept for improving the fatigue life for bridges using such end-to-end connections. Furthermore examples in practice of integral planned bridges made of hollow sections are presented. Also specifications and facts of the bridge as well as architectural features and special characteristics are described.