Cable or Wire Rope, Minimum Tensile Strength

I have a 1" diameter strand on an existing 1970s rehabilitated cable/wire rope bridge that I am analyzing. I know that the steel material is not of A36 type. I am looking for help in coming up with the minimum tensile strength.


Cable is never A36. You will really need to identify the particular type. 6x7 and 6x19 IWRC rope, 1" dia. has a breaking strength of 45.7 tons while galvanized bridge strand has a BS of 46.0 tons. The modulus of elasticity can vary from 13E6 to 21E6.

Refer to the Wire Rope Engineering Handbook published by Bethlehem Steel. There’s also more to the design, such a cable anchorage, sheave diameter etc. Also, factors of safety vary with the use.

The standard grades that I quoted from the manual was re-published in 1968. The handbook is archived courtesy of @slideruleera at

Above is a snippet.

I won’t know if this is the right size of cable, but the specification that I turn to for aircraft cables is MIL-DTL-83420. It defines the materials, construction, quality tests, and breaking strength of numerous types of wire rope. Not large sizes used in bridge construction, of course, but if you can find MIL-DTL-83420 on the ASSIST website you should be able to find the spec for the larger types.
Wire rope suppliers still conform their products to Mil-specs so if you ask for it, you can get it.

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