Through bolt installation errors

Depending on the respective approval, through bolts are suitable for embedment in cracked and non-cracked concrete.

EJOT offers various through bolts:
  • BA-V, made of galvanic zinc-plated steel
  • BA-F, made of hot dip zinc plated steel
  • BA-E, made of A4 stainless steel
  • (The through bolt BA-E-HCR, made of HCR stainless steel for highly-corrosive environments, is available upon request.)

Through bolts work by driving a steel bolt into the substrate. When the bolt is tightened, a metal ring is expanded, which in turn clamps the bolt into the substrate.

Caution on edges

This concept of load transfer over the expansion pressure is also the reason that the through bolt has its limits as a fastener for certain applications. This is mainly the case when the fixing points are close to the edge of concrete surfaces. If the concrete has not enough mass to absorb the expansion pressure, the result may be spalling of the substrate material and in the end even complete failure of the fixing point.

In the following you can see some negative examples for the assembly of through bolts:

What could have prevented the damage?

The minimum edge distance for through bolts in concrete should have been observed and the drill holes should have been perpendicular.

As a rule of thumb for the edge distance, a minimum of 6 times the through bolt diameter (6 * d) should be used. Example: through bolt M10 = min. 60 mm edge distance. The currently valid approvals of the manufacturer and the included centre distance needs to be observed as well. The respective European Technical Approval ETA-18/0219 contains information about the min. edges distances.

Chemical anchors for expansion pressure-free fixing

If it is not possible to observe the minimum distances for structural reasons, the only option is an expansion pressure-free fixing solution, which usually facilitates lower edge distances. Suitable for this are chemical anchors. How this works will be explained at a different time.

Product portfolio through bolts

As a fastening specialist, EJOT offers a variety of solutions for anchoring and connecting components on solid substrates in the field of anchoring technology.