The right choice of steel – according to the Eurocode - Economical Bridge Solutions based on Innovative Composite Dowels and Integrated Abutments - page 23

maximum basic thickness (for a specified minimum service temperature, 27J Charpy impact
value and the strength grade of steel) multiplied by a K-factor (for type of joint detail, stress
level and strain conditions). Therefore, the toughness assessment according to the Code may
benefit from the consideration of the structural details investigated - however, advantages of
higher toughness addressed by the Eurocode (subgrades, “Tab. 3”) stay disregarded.

2.3.3 Through thickness properties

Lamellar tearing is a type of weld-cracking that occurs beneath a weld (“Fig. 19”). It may
form when certain plate materials presenting low ductility in the thickness (or through) direc-
tion are welded to a perpendicular element. The failure by tearing is generally located within
the base metal outside the heat-affected zone and parallel to the weld fusion boundary. The
problem is caused by welds that the base metal is subjected to high shrinkage stresses in the
thickness direction. The main parameter governing the deformation behavior in its through-
thickness direction on the material side is the sulphur, contained as a residual element in the
steel. However, it is known that only the deformation behavior and not the strength in through
thickness direction can be improved by the steel manufacturing process.
Therefore, if necessary, lamellar tearing is avoided by the choice of the base mate-
rial with adequate ductility in the thickness direction. This choice defines the quality class
for through-thickness properties according to EN 10164 (2004) [8], the Z-grade as special
requirement in the steel designation (Z 15, Z 25, Z 35) (“Fig. 3”), and should be selected
depending on the consequences of lamellar tearing.

Figure 19: Lamellar tearing [9] Figure 20: Effective weld depth a eff for shrinkage,

Fig. 3.2 of [9]

The following aspects should be considered in the selection of steel assemblies or con-
nections to safeguard against lamellar tearing (“Tab. 4”):

The criticality of the location in terms of applied tensile stress and the degree of redun-
dancy.
The strain in the through-thickness direction in the element to which the connection is
made. This strain arises from the shrinkage of the weld metal as it cools. It is greatly
increased where free movement is restrained by other portions of the structure.
The nature of the joint detail, in particular the welded cruciform, tee and corner joints.
Chemical properties of transversely stressed material. High sulphur levels, in particular,
even if significantly below normal steel product standard limits, can increase the risk of
lamellar tearing.