What are the acceptable bolting methods per AISC?
There are four acceptable installation methods to obtain the pretension values for bolting: turn-of-nut method (with or without match marking), calibrated wrench method, twist-off-type tension-control bolt method and direct tension indicator method. Each of these methods is assumed to be used independent of the others.
What is turn of the nut method for tightening bolts?
Turn-Of-Nut is performed by rotating the nut or bolt of a fastener assembly a specific turn angle based on the fastener’s length, and diameter while restraining the unturned element from rotating.
How tight should structural bolts be?
This is re- ferred to as Snug-tight. i.e. no gap between the steel plates. Snug-tight can be achieved by a few impacts of an impact wrench or by the full effort of a person using a standard podger spanner. Correct bolt ten- sion is required to ensure effective load transmission on the joint.
What is snug tightening?
Snug-tight is the condition that exists when all of the plies in a connection have been pulled into firm contact by the bolts in the joint and all of the bolts in the joint have been tightened sufficiently to prevent the removal of the nuts without the use of a wrench.
What is torque turn method?
Torque-Turn. The torque-turn method is used when precise control over clamping force is required. There is an initial torque and an additional turn. The initial torque is required to bring all parts of the joint into contact. The additional turn provides the desired clamping force.
How is bolting done?
Bolts can come in a wide range of different sizes and shapes, but the basic production process generally remains the same. It starts with cold forging steel wire into the right shape, followed by heat treating to improve strength and surface treating to improve durability, before being packed for shipment.
What is AISC code?
The AISC Code of Standard Practice provides a framework for a common understanding of the acceptable standards when contracting for structural steel. As such, it is useful for everyone associated with construction in structural steel.
What is the bolt method?
This bolt tightening method involves measuring bolt tension through things such as load indicating bolts and washers, along with techniques that calculate the length change of fasteners.
What does TB stand for in bolts?
(TB) – Bearing type application.
What is TB and TF?
TB and TF. The norm is TB – this means under loads the connections can slip such that the bolts bear against their 2 mm oversized hole. For applications where building movement is not acceptable, TF is used. And the bolt uses friction to prevent it from slipping to the edge of the hole.
What is Step 1 of applying torque to a fastener?
1. Hand tighten all fasteners. Larger fasteners may require the use of a small hand wrench. 2.
What are the phases of fastening?
When a bolt is torqued, it typically operates in one of four phases: elastic phase, plastic phase, yield point, and shear point (figure 3). Elastic Phase — In this case, the bolt will stretch while under torque, but returns to its original condition as soon as the force releases.
What is the latest AISC Code?
The latest version of ANSI/AISC 360-16 dated March 2021 incorporates all of the errata to previous printings (the following errata lists include revisions to other parts of the 15th Edition Steel Construction Manual): Errata to ANSI/AISC 360-16, Revised March 2017. Errata to ANSI/AISC 360-16, Revised June 2018.
What are four methods of torquing?
Use of tension indicating methods.
- Torque Control Tightening. Controlling the torque which a fastener is tightened to is the most popular means of controlling preload.
- Bolt Stretch Method. A problem relating to the tightening of large bolts is that very high tightening torques are required.
- Heat Tightening.
What does B on a bolt head mean?
ASTM A307 Grade B Grade B bolts and studs have a tensile strength between 60 ksi and 100 ksi.
Does direction of bolt matter?
No. There is no requirement governing the entering direction of the bolt. Some people feel that bolts should be installed with the head up, so that a loosened bolt will not fall from the hole. However, a falling nut is nearly as dangerous as a falling bolt and a bolt without a nut should not be relied on to carry load.
Are all bolt tightening sequences created equal?
Not all bolt tightening sequences are created equal. Bolted flange joint assemblers have been using the Star Pattern since Taylor Forge started standardizing on flanges in 1938.
What is the correct tightening order for the bolts?
Before you can tighten the bolts, they can be numbered in a clockwise sequence (1, 2, 3, 4, 5 …) or by the tightening order. The two main methods of tightening sequence are the legacy pattern and modified model.
What is the best bolt tightening pattern for flange bolts?
As we mentioned earlier, this is the most common of all bolt tightening sequences used on flanged connections. The pattern is well understood around the globe, and its use has stood the test of time. The first thing you do is tighten each flange bolt between 20% and 30% of your target ft-lbs in the star pattern.
Is there a “silver bullet” bolt tightening sequence?
In fact, there is no “silver bullet” bolt tightening sequence ideal for torquing every type of flange or gasket. The gasket type, and arrangement of the flange connection, are both critical to choosing which tightening sequence an assembler can use.