Dynamic effects in reinforced beams at brittle failure - evaluated for timber members

Brittle failure in reinforced beams results in associated stress release in the beam. The reinforcement is activated to carry the released stresses by deformations between the beam and the reinforcement. This sudden process leads to dynamic impact, resulting in additional stresses in the system. In this paper, an analytical engineering approach is presented to estimate the magnitude of the corresponding stresses. The magnitude is dependent on the stiffness ratio between the reinforcement and the reinforced element failing in a brittle manner. On the example of timber beams with shear reinforcement in form of screws or threaded steel rods it is shown that a small increase in plastic deformation capacity of the reinforcement helps to considerably reduce the stress increase due to dynamic impact.