Rupture Length (material properties, i.e., structural efficiency)

Rupture length is the maximum length a bar of constant cross section area can be  suspended without rupture under its weight in tension (compression for concrete & masonry).

Rapture length defines material efficiency as strength / weight ratio:

R = F / λ

R = rupture length
F = breaking strength
λ = specific gravity (self weight) 

Rupture length, is of particular importance for long-span structures.  The depth of  horizontal span members increases with span.  Consequently the weight also increases  with span.  Therefore the capacity of material to span depends on both its strength and  weight.  This is why lightweight material, such as glass fiber fabrics are good for long- span structures.  For some material, a thin line extends the rupture length to account for  different material grades.

The graph data is partly based on a study of the Light weight Structures Institute, University Stuttgart, German.