Tightening Procedures in Steel Structures
Two commonly used types of bolts are:
- High strength bolt (A325, A449, A490).
- A307 is known by names unfinished, rough, common, ordinary and machine.
- They are made of low carbon steel having tensile strength of 60Ksi.
- A325 is made of medium carbon steel whose tensile strength decreases with increase in diameter
- High strength bolts can be tightened to large tensions.
Research Council on Structural Connections (RCSC) prescribes four tightening procedures.
- Turn of the nut method
- Calibrated-wrench tightening
- Installation of alternate design bolts
- Direct-tension-indicator tightening
- In riveted connections magnitude of clamping is function of length of rivet and magnitude of shrinkage after the head is formed.
- Magnitude f slip depends on the extent to which rivet fills the hole.
Bolted & Riveted Connections
Types of Connections
- Connection transmits the force by friction produced between the faying surfaces by the clamping action f the bolts.
- Slip-critical connections are recommended for joints subjected to stress reversal, severe stress fluctuation, impact, vibration or where slip is objectionable
Bearing type connections:
- Load is transferred by shearing and bearing on the bolt.
- Capacity in shear depends on whether shear plane intersects the body of bolt or threaded portion.