What are slip-critical bolts?

What are slip-critical bolts?

Slip-critical joint, from structural engineering, is a type of bolted structural steel connection which relies on friction between the two connected elements rather than bolt shear or bolt bearing to join two structural elements.

What are HSFG bolts?

HSFG bolts are high strength structural bolts which have been tightened such as to induce predefined tension in the bolt shank. Due to the tension in the bolt, the interface between the plies (steel members in a joint) cannot move relative to each other because of the frictional resistance.

What is a twist off bolt?

Made correctly, the “twist-off” will occur at a bolt pretension above the minimum required. The main advantage of “twist-off” bolts is that they can be tightened from one side by one person, although bolt installers now realize that regular hex bolts and DTI’s can also be installed one-side, one-man, too.

Do you torque the nut or bolt?

In simple terms, you need torque to create tension in a bolt. You use torque to turn a nut onto a bolt and then to stretch the bolt, making it a solid spring that clamps the two materials together.

How tight is snug?

Simon Bridge said: Turn the bolt until it stops, there is little or no visible gap and does not rattle when you shake it – a low-to-nil setting on a torque wrench for eg or just “finger tight”. This is “snug tight”.

Where are slip-critical bolts required?

Slip-Critical connections may also be required for connections that use oversized holes, slotted holes where the direction of the slot is not perpendicular to the direction of the load, and in connections where welds and bolts share in transmitting shear loads at a common faying surface.

What makes a slip-critical connection?

In a slip-critical connection, loads are transferred from one element to another through friction forces developed between the faying surfaces of the connection. These friction forces are generated by the extreme tightness of the structural bolts holding the connection together.

What is a squirter® DTI washer?

Squirter® DTI Washers are hardened DTI (Direct Tension Indicator) washers that when the proper tension has been applied to the washer, a colored silicone material will squirt out giving you a visual indication that the proper tension has been achieved. Squirter DIT’s are manufactured to the ASTM F959 specification

What is a DTI F959?

Load Indicating Washers (DTI) F959 Load indicating washers (LIW) are used to develop the correct tension when installing A325 or A490 structural bolts. Standard DTIs and Squirter™ DTIs are made to ASTM F959.

What size DTI bolts are available?

DTI’s and DuraSquirt DTI’s are manufactured for connections using bolts from 1/2″ up to 1-1/2″ diameter. They are available in ASTM A325 and A449 specifications.

What is a durasquirt direct tension indicator washer?

DuraSquirt Direct Tension Indicator Washers provide all the same advantages as the standard Squirter Washer. The added benefit is the Silicone used is designed to withstand exposure to the elements for up to 2 years.

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