McDonald’s posted better-than-expected sales in the first quarter as a new burger — and a continuing emphasis on value — brought in customers. The company said its global same-store sales, or sales at locations open at least a year, rose 3.8% in the January-March period. That was better than the 3.7% increase Wall Street was expecting, according to analysts polled by FactSet. McDonald’s shares rose nearly 3% before the opening bell Thursday. The limited-time Big Arch burger —- a 1,610-calorie behemoth that went on sale in the U.S. last month — became a viral sensation after McDonald’s CEO Chris Kempczinski posted a video of himself taking a nibble from one. Kempczinski was mocked for his tentative bite. Tom Curtis, president of rival Burger King, posted his own video taking a vigorous bite of his chain’s new Whopper. But the Big Arch did capture peoples attention. McDonald’s said U.S. customers spent more per visit in the first quarter than the same period a year ago.…