Question

why do bridges are declared unsafe after long use??

Answer 1

Because of wear and tear. Regualar use make them poor and they are usua;y closed after their purpose

Answer 2

$\underline{\underline{\Huge\mathfrak{Answer-: }}}$

A bridge during its use undergoes alternating stresses and strains for a large number of times each day, depending upon the movement of vehicles on it. When a bridge is used for long time, it loses its elastic strength. Therefore, the amount of strain in the bridge for a given stress will become large and ultimately, the bridge may collapse. That is why the bridges are declared unsafe after long