When Things Go Wrong Structural Stress and Fatigue

When a structure is poorly designed or built, it may not be able to withstand all of the forces it has to face. When a structure has to face large

combinations of internal and external forces over a long period of time, the structure might weaken. This may result in structural stress. At first, signs of structural stress may disappear when the internal and external forces are reduced. For example, if you place an abnormally large book on the middle of a bookshelf, the shelf might bend. The

bend in the shelf is a sign of stress. When the book is removed,

the shelf may go back to its original shape. However, if the

shelf cannot withstand the stress, it might crack. Permanent

changes, like the bookshelf cracking, are signs of structural