A brief introduction to shear reinforcement of concrete beams with the precious support of our Technical Department Eng. Stefano Agnetti and Eng. Andrea Costantini.
Shear reinforcement is necessary for structural elements, for which shear stress is higher than its strength. Strength has to be calculated taking into account the concrete contribution and the existing metal rebars.
Shear reinforcement is implemented with composite materials FRP (made of one or more layers), adhering to the external surface of the architectural elements to be reinforced. For unidirectional reinforcements the composite strips may be laid one next to another or at a given distance (pf).
The main parameters affecting the dimensioning of the strips are related to geometry (thickness, width, inclination and distance between FRP strips) and the disposition:overall wrapping or U wrapping.
In case of U wrapping on rectangular or T section, it is possible to avoid the detachment of the ends of composites by means of specific connectors.
The Italian laws fix the maximum and minimum width of the strips and interaxes to ensure the absorption of shear stress from FRP strips.
Products to be used for FRP reinforcements are:
- KImitech CB,
- bonded using resin Kimitech EP-TX
- impregnated with Kimitech EP-IN, avoiding the creation of areas with excessive concentrations of stresses