Capturing city issue

When I captured the city with infantry or armour unit, the infantry deal 0.2 damage and the armour car deal about 0.4 but why it's get destroyed which is waste of resource to build it again and it doesn't make any sense. For examples, The industry building has 20 hitpoint but why it gets destroyed. When the city is captured by a infantry unit, it should get 0.2 damage to building and the industry hitpoint should be 19.8. Please fix this bug issue.