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Crane runways are steel structures cyclically stressed by wheel loads.These structures are usually realized by means of steel girders or beams with hot-rolledor plated I-sections and a block rail fastened by welding on the section’s top flange.Due to the wheel loads the upper part of the girders including the rail welds issubjected to a local stress state mainly consisting of a local compression stress peak,local and local shear stresses. Furthermore, this stress state is superimposed bywelding residual stresses and normal and shear stresses as a consequence of globalbending. Up to the present moment no systematical experimental investigation has beenrealised. A research project has been launched to investigate full-scale crane runwayswith welded rails in cyclic testing with stationary and reciprocating wheel loads toidentify the contribution of damage on the multiaxiality. The paper solely focuses on theexperimental investigations with reciprocating wheel loads. Especially themicrostructural investigations on the location of the crack initiation and thedevelopment of the crack front are exemplified.