Kerto Composite (Hybrid City)


The main goal of the work is to experimentally verify the effect externally fastened steel angles on flexural performance of LVL beams. The objective is to increase its modulus of elasticity of a convetional LVL beam, while not disturbing any of the desired properties such as: low density, low thermal conductivity, and ease of connectivity to other LVL beams with common fasteners. The aim is to keep the cost of the modifications at minimum while investigating various alternatives of the proposed modifications. Several types of beam’s modifications were designed and applied on unmodified LVL beams. Both groups of modified and unmodified beams were tested in flexure and compared. Conclusions proposing application of the developed modifications were drawn from the results. Design of layered composite beams always fascinated me as the careful balance between tension and compression plays a crucial role. Therefore, when I heard about the Hybrid City Challenge, I was very excited. By accepting this challenge, I was able to put in test not only the specimens but also my earlier speculations regarding this subject matter.

Key benefit

LVL reinforcement. Modulus of elasticity increase. LVL use increase.

Material list

Kerto-S LVL 63mmx130mmx6000mm. Structural steel (S235) angles 25x25mm. Ring nails 4/40.

Ecological values

Thanks to Modulus of elasticity increase the reinforced LVL can replace steel and concrete structural elements.



  • Economical span (mm)
  • Thickness (mm)
  • Airbourne sound reduction factor (dB)
  • Impact sound transmission (dB)
  • Resistance to fire class
  • Thermal properties



  • This Hybrid City competition entry looks at the Kerto LVL as a beam and how to improve its performance in bending. It is a variation and improvement of a steel/timber flitch beam. The result is a research paper where a test series describes the effect of a steel re-inforced beam. The idea is worked out both theoretically with a gap analysis of the components strength and weaknesses, structural calculations, as well as with initial prototype testing. It also looks in the practical application of these beams, ways how to produce them, and gives hints where further work would be required or where further research and development would be of benefit.


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