If you don't want the navbar to be collaspeable in Bootstrap 3 it's pretty easy to disable it using LESS.
Open the file variables.less and locate @grid-float-breakpoint, it will look something like this:
@grid-float-breakpoint: @screen-sm-min;
To disable collapse just change the value to zero:
@grid-float-breakpoint: 0;
And the navbar will not collapse ever again!