Overview
Whenever you’re using pretensioned, high strength bolts, IE A325 & A490, ASSHTO, the RCSC and AISC require you to test at least 3 bolt assemblies, that are representative of what will be installed on site, all of which must meet or exceed the values in the RCSC’s Specification for Structural Joints Using High-Strength Bolts Table 7.1. The pre-installation test was designed to verify that the bolting crew, whom will be installing the bolts in the structure, understand and can preform the installation method being used, and that the installation method chosen combined with the bolt assembly will develop the minimum pretension as specified by RCSC’s Table 7.1. Pre-installation testing shall be performed for each fastener assembly lot prior to the use of that assembly lot in the work.
Procedure
1. Take 3 bolt assemblies consisting of 3 bolts of each diameter, length, grade, production lot, with 3 nuts of each diameter, grade and production lot, also include the appropriate washers of the same diameter grade and production lot, if washers are to be used. Each bolt, nut and washer combination is referred to as an “assembly.”
2. When installing with Turn-of-Nut installation/testing method, place the bolt in the bolt tension calibration testing device, with the bolt head in the back of the device, securely seated in the bushing (plate.)
3. Depending on the length of bolts being tested, you may need to add hardened spacers or flat shim plates achieve full-thread engagement of the threads, the bolt shank and the nut After you add the nut and washer (if you’re using washer) the end of the bolt shank must have full thread engagement prior to snug tightening the bolt, it is allowable to have 1 to 3 threads sticking out past the end of the nut. This step will prevent common job-site bolt testing issues, i.e. bolt shank out, among others. AT NO POINT SHOULD YOU “STACK OUT WASHERS” TO FILL THE GRIP SPACE. Using multiple washers, that are not going to be used in the actual connection, can cause inaccurate results possibly failing bolts that would otherwise pass.
4. Snug the assembly by rotating the nut (i.e. with a spud wrench) so that you can confirm a visual indication of tension on the testing device’s dial. We do this to ensure that all of the plys in the test assembly are in firm contact and to confirm that the head of the bolt is not rotating and to ensure that we are starting the test from the correct “starting line.”
Maximum Initial Tension Chart
| Bolt Diameter | A325/F1852 | A490/F2280 |
|---|---|---|
| 1/2 | 1000 | 2000 |
| 5/8 | 2000 | 2000 |
| 3/4 | 3000 | 4000 |
| 7/8 | 4000 | 5000 |
| 1 | 5000 | 6000 |
| 1-1/8 | 6000 | 8000 |
| 1-1/4 | 7000 | 10000 |
| 1-3/8 | 9000 | 12000 |
| 1-1/2 | 10000 | 15000 |
| Source: FHWA Appendix A1 | ||
5. Mark the end of the bolt shank, the nut and face plate of the testing device, mimicking the match-marking you would do when installing bolts in the structure.
6. Use the chart below to determine how far to rotate the nut.
Turn of Nut Required Rotation Guide
| Bolt Diameter | Bolt Length | Turns Required |
|---|---|---|
| 1/2" | Through 2" | 1/3 Turn |
| 1/2" | Over 2" through 4" | 1/2 Turn |
| 1/2" | Over 4" through 6" | 2/3 Turn |
| 5/8" | Through 2-1/2" | 1/3 Turn |
| 5/8' | 2-1/2" through 5" | 1/2 Turn |
| 5/8" | over 5" through 7-1/2" | 2/3 Turn |
| 3/4" | Through 3" | 1/3 Turn |
| 3/4" | Over 3" through 6" | 1/2 Turn |
| 3/4" | 6" through 9" | 2/3 Turn |
| 7/8" | Through 3-1/2" | 1/3 Turn |
| 7/8" | Over 3-1/2" Through 7" | 1/2 Turn |
| 7/8" | Over 7" through 10-1/2 | 2/3 Turn |
| 1" | Through 4" | 1/3 Turn |
| 1" | Over 4" through 8" | 1/2 Turn |
| 1" | Over 8" through 12" | 2/3 Turn |
| 1-1/8" | Through 4-1/2" | 1/3 Turn |
| 1-1/8" | Over 4-1/2" through 9" | 1/2 Turn |
| 1-1/8" | Over 9" through 13-1/2" | 2/3 Turn |
| 1-1/4" | Through 5" | 1/3 Turn |
| 1-1/4" | Over 5" through 10" | 1/2 Turn |
| 1-1/4" | Over 10"through 15" | 2/3 Turn |
| 1-3/8" | Through 5-1/2 | 1/3 Turn |
| 1-3/8" | Over 5-1/2" through 11" | 1/2 Turn |
| 1-3/8" | Over 11" through 16-1/2" | 2/3 Turn |
| 1-1/2" | Through 6" | 1/3 Turn |
| 1-1/2" | Over 6" through 12" | 1/2 Turn |
| 1-1/2" | Over 12" through 18 | 2/3 Turn |
| Source: RCSC Table 8.2 | ||
7. Using the table , verify the needle on the testing device’s dial shows 5% more than the required bolt minimum pretension.
Table 7.1 Minimum Bolt Pretension for Pre-Installation Verification
| Bolt Diameter | A325/F1852 | A490/F2280 |
|---|---|---|
| 1/2 | 13,000 kips | 16,000 kips |
| 5/8 | 20,000 kips | 25,000 kips |
| 3/4 | 29,000 kips | 37,000 kips |
| 7/8 | 41,000 kips | 51,000 kips |
| 1 | 54,000 kips | 67,000 kips |
| 1-1/8 | 59,000 kips | 84,000 kips |
| 1-1/4 | 75,000 kips | 107,000 kips |
| 1-3/8 | 89,000 kips | 127,000 kips |
| 1-1/2 | 108,000 kips | 155,000 kips |
| Source: RCSC Section 7 | ||
8. Record the bolt tension as required and test the remaining 2 bolts. Use the average torque value, for the 3 samples, as a guide for the torque needed to install these bolts.
Sources: RCSC, AASHTO & FHWA
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