Question

the bridge are declared unsafe after long use .why?

Answer 1

Due to repeated stress and strain, the material used in the bridges loses elastic strength and ultimately may be collapsed. Hence, bridges are declared unsafe after long use.

Answer 2

$\Large \text{EXPLAINATION :-}$

❁ A bridge undergo continuous alternating strains number of times in a day .

❁ After long period the bridge gets fatigued and there is loss of strength of bridge .

❁ Bridges are regularly and continuously used .

❁ Then the amount of strain in the bridge for a given stress will be large and causes the collapse of the bridge . This permanent changes leads to it's Collapse.

❁ Hence To avoid this, bridges are declared unsafe after long use