AbstractHarbour structures like quay walls or construction pit walls in civil engineering are often built up with steel sheet piles. Aside of U‐steel sheet piles also Z‐shaped piles with interlocks are widely used in such structures. The pressure on costs and efficiency and the competition in this field lead to the necessity of increased efficiency in design. To benefit from the potentials in the bending moment capacity of semi‐compact Z‐shaped steel sheet piles forming the infills of combined walls, four‐point‐bending tests were carried out by the Institute of Structural Design at the Materials Testing Institute in Stuttgart in 2019. A FE‐model was validated by back‐calculating the tests, followed by an extensive parametric study (GMNIA) with different Z‐piles. Among others the different geometries, which lead to different b/t‐ratios and the steel grade were varied leading to a different compression flange slenderness. In addition, the lock state was varied to investigate the impact on the bending moment capacity as: Free lock rotation, crimped interlocks with different crimping densities and fully welded over the entire length. Three resistance models were investigated and evaluated for further development of Eurocode 3 Part 5. The FE model was simplified and further developed for stability analyses. This was followed by a parametric study aimed to investigate the stability of Z‐shaped steel sheet piles under axial loads.