Analysis of reduced modulus action in U-section steel sheet piles

U-section steel sheet piles are commonly used for constructing retaining walls in marine environments and have been in widespread use throughout the world for most of the 20th century. Relatively recently, concern has been raised about the bending strength of this pile section, because U-section piles are connected together by interlocking joints located along the pile wall centreline. As the piles resist bending moments, inter-pile movement can significantly increase bending stresses. When this occurs, the wall is said to have exhibited reduced modulus action (RMA), reducing the bending strength and stiffness below the fully composite values normally assumed during design. In view of this concern, the recently introduced Eurocode 3: Part 5 has introduced strength reduction factors to account for the effect of RMA during design. The work presented herein has been carried out in order to provide more information as to the values that should be selected for these reduction factors. The work is based on the experimental testing of one-eighth-scale miniature piles.