What is the term for defect that runs along the rings of timber?

The term that describes a defect running along the rings of timber is "shake." Shakes are separations or cracks that occur in the wood, primarily parallel to the growth ring structure, and they typically result from the natural drying process of the timber. This defect can be caused by various factors such as rapid drying or environmental stresses during the growth of the tree. Understanding shakes is essential for evaluating the structural integrity of timber elements in bridges, as it can affect their load-bearing capacity and durability.