The Bulls gave the Hurricanes a big test but fell short, while the Brumbies ensured there will be no South African sides in the last four.
Salesi Rayasi grabbed a double as the Hurricanes battled past the Bulls 35-28 to reach the Super Rugby semi-finals and the Brumbies battered the Sharks to saunter into the last four.
The Hurricanes will face defending champions the Crusaders at Orangetheory Stadium in a repeat of last year's semi-final next Saturday after overcoming the spirited Bulls.
John Plumtree's side looked to be cruising through at Westpac Stadium when they went in at half-time with a 24-14 lead following tries from TJ Perenara, Ben Lam and Rayasi.
Warrick Gelant had scored the first try of the game and Cornal Hendricks crossed six minutes before the break, but three tries in the space of 10 minutes and nine points from the boot of Beauden Barrett made it advantage the Hurricanes.
Rayasi - a replacement for Wes Goosen midway through the first half - had a brace early in the second half but the Bulls were awarded a penalty try after the wing was sent to the bin.
Hendricks touched down for a second time in between a couple of Jordie Barrett goals and he dropped the ball wide on the right with time up as the Bulls applied late pressure without reward.
The Brumbies will travel to face first-time semi-finals the Jaguares after a 38-13 thumping of the Sharks at Gio Stadium.
Pete Samu touched down twice in the first half and there were also tries for Henry Speight, Joe Powell and Matt Lucas for Dan McKellar's men.
The Sharks were unable to live with the Brumbies' power and creativity, Andre Esterhuizen scoring their only five-pointer in the first half.