Rules

23. Ball Touches Permanent Fixtures
If the ball in play touches a permanent fixture (other than the net, posts, singles sticks, cord or metal cable, strap or band) after it has hit the ground, the player who struck it wins the point; if before it hits the ground, his opponent wins the point.

USTA Comment: A ball in play that strikes a pipe support running across the Court at the base of the net is treated the same as a ball landing on clear ground. See USTA Comment under Rule 20 e. for a player who touches a pipe support.

Case 1. A return hits the Umpire or his chair or stand. The player claims that the ball was going into Court.
Decision: He loses the point.