Achieving increased load-bearing capacity in wooden beams in one minute

11. April 2019

A wooden beam is a thing of beauty. It’s a natural product that can be used almost anywhere. But this construction material can also cause issues. In wood construction, components subjected to transverse compression, transverse load and shear load, such as in a coped girder support, represent critical points in the construction. We therefore provide the solution and show you how to achieve a higher load-bearing capacity with your wooden beam within one minute.

Non-braced wooden beam on a testing device

The critical point in wood construction: components under shear stress. Allegedly a strong construction material, wood can fail if the beam is subjected to too much shear load. But just how much load can a non-braced beam really carry? Our testing device allows us to try it out. We placed the beam on the testing device and caused it to fail under load. The conclusion: the non-braced beam will fail at approx. 20 kN. But how can we circumvent the material’s natural weakness?

Braced wooden beam on a testing device

We carry out a second test. In this instance we try to circumvent the natural weakness of the construction material by bracing the beam. The same wooden beam (the one that previously failed) is braced in the same part of the girder support with two full thread screws, which in this case are the fischer Power-Full screws with a diameter of 8.0 x 195 mm. The same test is carried out as before with the non-braced beam. We place the braced beam on the testing device and add loads until the beam fails. In this case, we were able to add loads of up to 53.4 kN until the beam failed. This means that during this experiment we had a load increase of 267 per cent with the braced beam when compared to the non-braced beam.

Conclusion: Achieving significantly higher load-bearing capacity with full thread screws

This test taught us that full thread screws used as bracing elements in beams that are subjected to shear loads can effectively prevent failure, or rather significantly increase the load-bearing capacity. The same applies to wood components that are subjected to transverse compression and transverse loads. The aim of our test was to add loads until the beam failed. Obviously this isn’t the objective in everyday life, and our 267 per cent load increase should therefore not be seen as a benchmark. Nevertheless, this example demonstrates that the load-bearing capacity of a braced beam can be significantly increased without having to change the beam’s exterior or enlarging its cross-section. When bracing the beam, ensure that the full thread screws are inserted in parallel.

One final piece of advice: The drill bit tip of the fischer full thread screws Power-Full reduces  the risk of splitting, which enables lower edge and axial spacing without pre-drilling, saving time and materials. The European Technical Approval (ETA-12/0073)  of the fischer Power-Full screw also provides additional security.

fischer Power-Full

The full-thread screws with cylinder head and TX star recess drive.

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