The RCSC Specification does not directly permit reuse of any structural bolt. The Specification does permit reuse in certain cases when approved by the Engineer of Record. Considering best practices, LeJeune Bolt Company does not recommend fully pretensioned reuse of F3148 assemblies. In this case “reuse” is defined as two or more complete pretensioning installations (torque plus angle), or using the angle mode multiple times sequentially (torque plus angle, plus angle).
Like the turn of the nut method, using the angle mode on the TNA® tool will permanently stretch the fastener. TNA® assemblies have sufficient lubrication and ductility to stretch well beyond the target minimum pretension and nut rotation. Testing by the University of Cincinnati demonstrated that the great majority of TNA® assemblies support multiple full pretension cycles. While unlikely, using multiple angle cycles could result in stretching the bolt to fracture or the spline shearing off. In test cases where the spline sheared the assembly was always well above minimum pretension.
It is LeJeune’s objective to provide an optimal system, designed around optimum fastener performance, and as such we would not recommend a practice that was less than ideal. However, as recognized in RCSC for other fastener standards, LeJeune would support an Engineer of Record’s decision permitting reuse of fully pretensioned F3148 TnA assemblies in certain circumstances.
The TNA® system is designed so that the torque applied to initially tighten the assembly is below the bolt yield strength and as such does not permanently stretch the fastener. Multiple snugging passes or snugging and removing a fastener for use in another (or the same location) is not considered reuse of structural bolts by RCSC. Tensioning TNA® assemblies in the snug mode (single or multiple applications or locations) is not considered reuse for F3148 TNA® assemblies, in fact multiple controlled snug cycles are one of the intended design improvements the TNA® system has over other bolting methods.
Yes. Tension Control Bolts have been used for many years in bridge construction. Appoximately 1/2 of the nations DOT’s have approved the use of TC’s for regular use and many others have given conditional use approval for specific projects. Bridge projects typically require a mechanically galvanized or weathering steel (Type 3) fastener. Both of these types are available as F1852 (A325) tension control bolts and can be ordered through LeJeune Bolt Company.
Our Clean-Lube Nut was developed as a solution for contractors spending vast amounts of resources preparing bridges for topcoat. The typical mechanically galvanized nut is emersed in a wax-based lubricant that is visible through the required dye. Prior to topcoat, contractors are required to remove all evidence of contamination from the prepared surface that may cause topcoat failure. The standard wax dye nut was requiring an exponentially large amount of time and resources to clean. The clean-lube nut offers a dry to the touch lubricant that is placed on the internal threads and a single bearing face leaving the exposed nut surface after installation completely free of any contamination. The nut requires no additional surface prep than is required by your indicated surface prep procedure. Our Clean-Lube Nut meets the requirements of ASTM A563 Supplementary Requirements – Section S3 Lubricant Placement.
This scenario typically arises from clearance issues when the shear wrench cannot fit into a tightly designed connection area. We would recommend installing a standard A325 or A490 heavy hex bolt in these instances. If the TC bolt must be used in a pretensioned joint, they may be installed using one of the other approved installation techniques. When this is done, your inspector should sign off on the installation and the tip should not be removed by some other means (i.e. cutting, torching, hammering). In snug tight connections, the fastener may be tightened using a spud wrench or impact wrench.
We apply a destinctive lubricant to the nut for use on our F1852 (A325) mechanically galvanized tension control bolts. The nut is coated with a solid film, non-water soluble lubricant that is black or dark charcoal in color. This lubricant is used to control fastener tension and torque. The end result is more consistent installation tension in the field. The nut is an A563 DH nut that is both overtapped and mechanically galvanized under the lubricant required by ASTM F1852. The lubricant meet the requirements of ASTM specification F1852 section 6.4, ASTM A325 section 4.4, and ASTM A563 section 4.8.1 and supplementary requirement S2.1. The specifications read “the lubricant shall have a color that contrasts with the zinc coating so its presence is visibly obvious”.
Yes, there are three approved coatings options for A490 bolts, ASTM F1136/F1136M, ASTM F2833 and ASTM F3019/F3019M.
Potential users/specifiers should review Bulletin on Zinc/Aluminum Coatings prior to ordering.