Cable Material, Construction & Elongation


Material & Corrosion Protection Options

The level of corrosion protection is the very first consideration in the cable specification process, critical not only for aesthetic appeal, but for structural performance and longevity.
Ronstan offer cables manufactured from the following materials:

Cable Material, Construction & Elongation

Stainless Steel Grade 316 – Superior Corrosion Resistance & Aesthetics
Grade 316 stainless steel with it’s with increased chromium, nickel, and the addition of molybdenum, is the most ‘all round’ stainless steel in terms of resistance to corrosion and tensile strength. Today, it is used commonly as a default grade for architecture, offering significantly greater aesthetic appeal, and resistance to corrosion, than coated carbon steels.
The active protection offered by the naturally occurring chromium oxide layer on the surface of stainless, requires significantly less maintenance than carbon steels.
The basic austenitic stainless material offers superior resistance to extreme temperatures than carbon steel. It has a lower tensile strength and hence is more elastic than carbon steel.

Cable Material, Construction & Elongation


Open Spiral Strand consists of a plurality of round strands of the same diameter laid together in one or more layers. This construction provides good cross sectional area for higher tensile strength and minimal elongation, and is well suited to static rigging applications. Depending on diameter 1×19, 1×37, 1×61, or 1×91 constructions are used for stainless steel cables.

Stainless Steel open spiral strand adds the attributes of unparalleled corrosion resistance and aesthetics to the mix of high structural integrity and performance.

The ultimate structural cable with the highest corrosion resistance for visual architectural applications.

Applications Include:

Cable Material, Construction & Elongation Cable Material, Construction & Elongation

Galfan Coated Carbon Steel – Moderate Corrosion Resistance
While non-alloyed carbon steel is more economical than stainless, it requires coating, and later painting, to maintain corrosion protection.
The Galfan coating, with its 95% zinc and additional 5% aluminium composition, provides significantly greater resistance to corrosion for carbon steels than conventional galvanized coatings. As the sacrificial zinc layer in galfan gives way, an aluminium oxide layer develops replacing the lost zinc. This extends the life of the coating beyond where standard galvanizing offers no protection and renders the steel vulnerable to corrosive elements. Depending on the environment, a galfan coating will erode three to six times slower than conventional galvanizing.

Cable Material, Construction & Elongation


Open Spiral Strand consists of a plurality of round wires of the same diameter stranded together in one or in several layers. This construction provides good cross sectional area for higher tensile strength and minimal elongation, and is well suited to structural architectural rigging applications. Depending on diameter 1×19, 1×37, or 1×61 constructions are used for Galfan strand.

Galfan Coated Carbon Steel open spiral strand cables offer economy with higher tensile strengths than their stainless counterparts above. While lacking the stainless ‘glitz’ and corrosion resistance, aesthetically the end fittings are streets ahead of chunky industrial styled galvanized alternatives.

The carbon steel cable with the highest corrosion resistance and best aesthetics.

Applications Include:


Cable Material, Construction & Elongation


Full Locked Cables consist of a round multistrand core around which several layers of Galfan coated shaped strands are locked together. The round inner strands are heavy galvanized and the voids filled with a durable elastic zinc dust paint. The outer profiled layers are dry-stranded to avoid any escape of the internal filling under load.

The combination of the densely enclosed Galfan locked strands and the internal filling provides extreme resistance to corrosion. The full locked cable is primarily used for higher load applications where resistance to deformation, surface compression (e.g. when using clamps) and good corrosion protection are essential. All cables are pre-stressed and manufactured to a nominated design load.

The ultimate structural cable for high load and engineered applications.

Applications Include:

  • Bridge and guy cables.
  • Main cables for lightweight cable structures.
  • Tie back cables.
  • Cables for Stadia, sports arenas or exhibition facilities.

Cable Elongation

Stretch or elongation is a characteristic of all cables and wire ropes, initially as permanent stretch when the load is first applied and the individual wires bed down, then as conventional elastic stretch within the wires as load increases. Where stretch is critical to the application, initial stretch can be accounted for with cables pre-stretched (pre-stressed) during swaging and cable manufacture.

As unloaded cables show a non-linear load/elongation behaviour, the most accurate method of determining cable elongation is by pre-stretching (pre-stressing) the cable to a defined load. This process involves cyclical loading of the cable until elongation has stabilized and the measurement taken. The following stretch calculation can be used as a guide, but should be verified by your Structural Engineer, or the pre-stretching measurement method.

Cable Material, Construction & Elongation


W = Applied load (kN)
L = Cable length (mm)
E = Strand modulus of elasticity (kN/mm²)
A = Metallic cross section area of cable
(refer Structural Cables tables)

Typical values for E: Stainless Steel Cable
7 x 19 97.1 kN/mm² 14,100 ksi
7 x 7 106 kN/mm²  15,400 ksi
1 x 19 127 kN/mm² 18,400 ksi
1 x 61 130 kN/mm² 18,850 ksi
1 x 91 130 kN/mm² 18,850 ksi
“Galfan” Steel Cable
1 x 19, 1 x 37, 1 x 61, VVS-1, VVS-2, VVS-3
  160 kN/mm² 23,210 ksi
Ronstan Tensile Architecture