Why are the bridges declared unsafe after long use ?

1.	Why are the bridges declared unsafe after long use ?
Answer» SOLUTION :A BRIDGE during its use undergoes alternating strains a large number of times every DAY . When a bridge is used for long time it loses its elastic strength . Due to this the strain produced for a given STRESS may be quite large . ASA result the bridge may collapse . To avoid this the bridges are decleared unsafe after long use .

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