Fuck-off HUGE Tornado in northern Texas

[Napoleon the Clown]

What would happen if F5 tornado like recent 2011. Joplin tornado would directly hit major city like Dallas? Would it tip over the skyscarapers causing total nuclear attack level damage in city center? Evacuating a city is not an option because tornadoes are too unpredictable. Are there enough secure places where to take cover in such event for over a million people?

Skyscrapers wouldn't topple but seeing measurable deformation of the skeleton wouldn't be surprising. Skyscrapers actually HAVE been directly hit by F5/EF5 strength tornadoes. There's one recorded instance of it twisting the frame by several inches, enough that they thought it would have to be demolished, initially. Fortunately, it was still structurally sound so they didn't have to take it down. And that was a skyscraper getting hit directly by the funnel. Tornadoes can do some crazy shit, yes. But a skyscraper wouldn't get toppled. Not in the US, anyway. Building codes are wonderful things.

[madd0ct0r]

In my area that's a major reason. It's not unusual for those structures that do have basements to have multiple sump-pumps to keep them dry. If the power goes out you will have standing water. This part of the state is only slightly higher than Lake Michigan and quite a bit of it is still swamp for part or even all of the year.

Is it that hard to waterproof concrete?

I don't know. I don't know much about waterproofing concrete.

at that depth it's pretty easy, providing you build it correctly in the first place. Repair is possible, but it's a pain in the arse.
A lot of USA non-city construction i've come across on the web is cinderblocks or grouted cinderblocks which will leak like anything. You'd need high quality, well vibrated monolithic concrete, with sufficient cover over any steel, waterstops at the construction joints (eg a strip of rubber half embedded in the slab and half in the wall above it) and the space, formwork and money to cast it.

My site at the minute has 2 basements to total depth about 8m, and we've got horrendous leaks (cos the piling contractor was shit). currently repairing them now. I've seen some lovely work in saigon, they must have gone 12m down, 100m away from the river and not a leak in sight.