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OMF Bolt-Tightening Requirements

Strong Frame Moment Frame

General Bolt Installation Instructions

  1. All hardware must be protected from dirt and moisture. Do not remove hardware from packaging until it is ready for installation.
  2. The performance of bolt assemblies (bolt, nut, hardened washer and DTI washer) has been verified through pre-installation verification testing. (Important: Do not substitute any components.)
  3. Lubrication is critical to proper installation. Do not remove lubricant on bolt assemblies or apply additional lubricant.
  4. High-strength bolts which have been fully tightened may only be reused if the nut can still be threaded onto the bolt by hand.

Snug-Tight Joints

  1. Install a DTI washer under the bolt head, with the protrusions against the bolt head. Slide the bolt through the connection holes. Install the hardened washer and nut on opposite side (see Figure 1).
  2. Tighten all bolts to snug-tight condition, making sure the bolt head does not turn while the nut is turned (see Figure 2). Snug-tight condition is the tightness attained by either a few impacts of an impact wrench or the full effort of a worker with an ordinary spud wrench that brings the beam end plate and column flange into firm contact. Little or no orange silicone from the DTI washer should be visible at this time.
OMF Bolt-Tightening Requirements: Figure 1
OMF Bolt-Tightening Requirements: Figure 2
OMF Bolt-Tightening Requirements: Figure 3

Pretensioned Joints

  1. Install a DTI washer under the bolt head, with the protrusions against the bolt head. Slide the bolt through the connection holes. Install the hardened washer and nut on opposite side (see Figure 1).
  2. Tighten all bolts to snug-tight condition, making sure the bolt head does not turn while the nut is turned (see Figure 2). Snug-tight condition is the tightness attained by either a few impacts of an impact wrench or the full effort of a worker with an ordinary spud wrench that brings the beam end plate and column flange into firm contact. Little or no orange silicone from the DTI washer should be visible at this time.
  3. Once all bolts are snug-tight, calibrate the DTI washers by fully tightening one of the four inside bolts (see Figure 4). Proper installation pretension is reached when the 0.015" feeler gauge can no longer be inserted all the way into the bolt shank at three or more of the five notches between the silicon markers (see Figure 5). Remember to make sure the bolt head does not turn while the nut is turned.
  4. Tighten all bolts, starting with the most rigid part of the joint (typically the three remaining inside bolts, and then the four bolts above and below the beam) (see Figure 4). The proper installation pretension is reached when the amount of squirt from the silicon markers matches the washer from the calibration in Step 3 (see Figure 3). When tightening bolts, make sure the bolt head does not turn while the nut is turned.
  5. Verify that at least four of the silicon markers have squirted at each bolt. Completely flattened DTI washers are acceptable.
OMF Bolt-Tightening Requirements: Figure 4
OMF Bolt-Tightening Requirements: Figure 5

Connection-Plate Gaps And Finger Shims

The finger shims provided may be used to adjust the connection between the beam end plate and column flange. For a gap of 1/8" or less under the bolt head (see Figure 4), draw plates together by tightening the bolts until plates are in rm contact. If the gap exceeds 1/8", shims must be installed. Gaps away from the bolt heads are permitted. If the connection plates cannot be drawn together sufficiently by tightening the bolts, additional shims are required. Total thickness of shims under each bolt head must not exceed 1/4". To install shims, loosen connection bolts and slide provided shims around the bolts where necessary. Make sure shims do not protrude beyond the outer edges of the connection plates, and re-tighten bolts.

Finger Shim Diagram