Why steel is used in concrete?

In a axial loading.There are two type of forces
1. Tension force Or 2. Compression force
Acting on body

The steel is good in tension and compression strength but concrete is only good in compression strength
The long column is break Or failure due to Buckling of column
you seen in a fig the inner edge of column is in compression but outer edge of column is in tension
if you want more details go to you tube
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