High strength thermomechanical steels S460 (AST MA 913 Grade 65)
Using S460 grade steels for structural sections presents numerous advantages for multi-story and highrise buildings thanks to their optimum relation of cost and efficiency: The higher strength of the material allows to reduce the size of the structural sections, specially when used as columns, allowing the realization of lighter buildings, with equal structural safety.
Structural shapes in S460 are also produced by thermomechanical rolling (the correct name is S460M or S460ML according to European regulations EN10025 : 2004 ), a process that affects the chemical composition of the material, reducing its alloy content: This process translates into better weldability of the material, generally the sections do not require pre-heating, allowing further savings in costs and time. An additional advantage is that less material welding is used, as the sections to be welded in S460 may be, on equal terms, thinner than traditional steel sections.
Depending on the application, the weight reduction for using S460 (65 ksi) in comparison to S355 (50 ksi) is generally between 10 percent and 30 percent. For columns, weight saving is on average 15 percent; for trusses it is usually more than 20, sometimes even up to 35 percent. Thus S460 shapes are used predominantly as columns in multi-story structures, as beams in short- to medium-span bridges and as diagonals and chord members in trusses.
For seismic applications, high yield strength steels offer an additional advantage: They allow structural engineers to optimize the design of the "strong column-weak beam" concept by using columns in S460M and beams in S355M. This can help the engineer implement the relatively new concept of "clean columns", which means choosing stronger columns without costly web reinforcing in the panel zone of moment connections. With these columns, any cost increase due to the use of heavier shapes (or in the case of S460M / 65 ksi material, heavier and stronger column shapes) is minimal compared to the fabrication time and cost savings from the elimination of web doubler plates.