Limitations of through bolts and hollow sections

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IDEA StatiCa Connection allows designing nearly anything. But some connections are non-standard and cannot be checked by simple general checks provided by the codes implemented in IDEA StatiCa. One of them is the connections of hollow sections (traditionaly RHS) with through bolts.

Through-bolts are an alternative to blind bolts, hollo bolts, flow-drill bolts, or other special types of fasteners. They are easy to come by; threaded rods, nuts, and washers are all that is needed. However, the design and assembly have to be carefully thought through.

  • First of all, the bolts cannot be preloaded, and even the snug-tight bolts must be tightened very carefully so that the hollow section is not flattened. 
  • Second, the bolts do not undergo the typical failure mode when loaded in shear. The check of bolts in shear is not valid, and the through bolt must be designed as pins.
  • Third, the plates are not gripped by bolt and may cripple. Their resistance in bearing is decreased compared to a typical bolted connection.  

These facts have to be considered in the design, and the respective checks in IDEA StatiCa Connection must be replaced in order to deliver the correct and complete check for a through-bolt.

This article is based on a paper by Jason McCormick, Connecting Hollow Structural Section Members with Through-Bolts.

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