P: 402 426-2104

F: 402 426-2105

Fastening Method

A friction connection is the most fatigue resistant type of connection used in steel construction today. It was developed in 1919 for use in bridges and other cyclically loaded structures. This fastening method has the following properties:

• Once the bolt is tensioned, it never sees additional load. The bolt merely provides the normal force required for the friction between the plates to work.
  
  
• We have designed the connection based on Euro Code 3, which is the most comprehensive code dealing with fatigue.
  
  
  • Our redundancy in connection design provides an alternative load path should an overload occur. This safety condition does not exist in current flange-to-flange connections.
    
    
  • The primary load path in the NORTHSTAR tower is the friction between the splice plates.
    
    
• In an overload situation the secondary load path is the bearing of the bolts on the tower wall and splice plates.
  
  
• Our proprietary design allows for practical field installation, as well as long term O&M. Bolt tensioning during installation is done from the inside of the tower. All bolt inspections are done by a simple visual inspection from the inside as well.
  
• A benefit of using the turn-of-the-nut system is that calibration of tension tools is no longer required as this method is not based on torque. This reduces risk related to installation error.

By always being mindful of the concerns and constraints related to field assembly, NORTHSTAR has worked diligently to minimize the amount of manpower and equipment necessary to efficiently construct the lower tower sections in the field.