Is it appropriate to spec ASTM F1554 in place of A36 tie rods for higher strength applications? What are the lengths these rods come in, the availability of each grade, and cost differences?
Most ASTM standards address the recommended application of the fastener. There are often two or three different ASTM specifications with similar chemical and mechanical properties, but with differing applications. ASTM F1554 is a specification that is designed for anchor bolts embedded in concrete. Since your application is for tie rod assemblies, it would appear that technically, you should select a different specification with similar properties to the F1554 grade 105 specification. In this case, you should consider using ASTM A354 grade BC which is virtually identical to F1554 grade 105 both chemically and mechanically, but is not limited by its application. For a strength comparison of these two grades refer to our strength by grade chart.
Chemically, we manufacture both grades of fastener using the same medium carbon alloy steel (4140). The strengths of these two grades are virtually identical with only subtle differences. F1554 grade 105 has a 105,000 pounds per square inch (psi) minimum yield strength while A354 grade BC has a minimum yield requirement of 109 ksi. The minimum tensile strength requirement of both grades is identical at 125 ksi with F1554 grade 105 also possessing a maximum requirement of 150 ksi. From a manufacturing perspective, we make these bolts in the same way using identical raw material. We certify the finished product based on the end use application of the bolt and based on the requirements of the customer.
If you are considering a larger diameter F1554 grade 55 for this application, there is not a straightforward substitution. Many engineers specify A572 grade 50 (50 ksi minimum yield instead of 55 ksi). We often manufacture rods to this grade, although A572 is really a steel specification and not a bolt specification. There are no other ASTM grades that are similar. Therefore, if you want the chemical and mechanical properties of the F1554 grade 55 specification for a tie rod application, there is no reason you still can’t specify this grade of fastener even though technically it should only be used for an anchor bolt.
Portland Bolt’s view of ASTM specifications is that they are simply guidelines. They are used to order product so that a purchaser has a reasonable expectation as to what they will be receiving when they order based on the requirements of a given specification. However, any aspect of a given specification can be altered provided there is complete understanding and agreement on what changes are being made to a given specification. For example, let’s say in this application that you wanted to use the A354 grade BC specification due to the application instead of F1554 grade 105, but it was critical that the tensile strength not exceed 150 ksi as is the case with the F1554 grade 105 specification. You could certainly stipulate that the bolts be ordered and manufactured to the A354 grade BC specification with the tensile strength NOT to exceed 150 ksi. Likewise, there is no reason you can’t specify the use of F1554 grade 55 rods for a tie rod application if that specification of rod gives you the mechanical values that you are looking for as long as you, the buyer, and the manufacturer all understand that the end use application is different than the intended application of the F1554 specification.
The raw material cost for F1554 grade 105 or A354 grade BC is approximately 50% more expensive than F1554 grade 55 raw material. All of these grades of steel are currently available in our inventory. The raw material for both F1554 grade 105 and A354 grade BC is commonly available in 24 foot lengths while F1554 grade 55 raw material is available in 20 foot lengths. If you would like us to put together budgetary pricing or comparison pricing for you please provide us with a specific list of quantities, grades, and sizes and we will be happy to provide you with a cost estimate.
As always, feel free to submit your questions.