All the fencing and securing of perimeters isnt to keep Congress locked in it's to make sure leftists don't riot and actually storm the capitol when it turns out Trump will be President.
Why fortify DC so heavily if you are worried about Trump supporters? Shouldnt they be deployed to different state capitals where the right wingers live? DC is 95% democrat.
As I understand it, FEMA is in charge of the country, with managers overseeing 10 regions of the country. The authority & power of FEMA cannot be overstated. Their recourse is greater than Martial Law.