Old historically relevant buildings, originally built as residences, are more and more often renovated and turned into offices, libraries and public places. The need to increase the load bearing of floors while safeguarding the well-proportioned beauty of the original structures - the legacy of a relevant cultural background - has led to the development of several reinforcement techniques.The most reliable and cost-effective one is the mixed wood-concrete structure.
The procedure aims at establishing a static connection between the pre-existing wooden beams with a new limited thickness reinforced concrete slab, cast above the completion planking of the floor. The connecting element is an L-shaped steel rod secured to the beam with epoxy adhesives and set in the new concrete casting.
Thanks to this technique, the bending behavior which is typical of two purely overlapping structures is changed to the more rational and effective one typical of multi-layered beams. The reliability of the operation stems from the epoxy adhesive which ensures perfect and long-lasting union between wood and concrete so that the two overlapping structures can effectively convey to one another mutual forces moving in a direction parallel to axis. Epoxy resins are the most suitable ones, because they are the only ones which maintain in time the excellent features of adhesion to wood and prevention of rod pull-out.
Epoxy resins are the best adhesives available because they do not have solvents. This means they harden without shrinking and they have excellent mechanical features. Their elastic modulus, which can be adjusted as per specific structural requirements, can be made similar to wood.