Rising for the sixth straight session, the Sensex at the Bombay Stock Exchange gained 85 points, or 0.5 percent, to 18,902, today, as global markets climbed amid the re-election of Barack Obama as US President. The Nifty at the National Stock Exchange rose 36 points, or 0.6 percent, to 5,760.Stock markets in Hong Kong, South and Singapore gained between 0.5 percent and 0.8 percent.