Longshore workers kept the Port of Oakland, California shut for a second day Wednesday as union officials studied a wage and benefits offer. The Oakland work stoppage, which began Tuesday, was part of a campaign by West Coast longshore workers to press for concessions after their last contract expired on July 1. The Pacific Maritime Association, which represents the management of West Coast ports in contract negotiations with the International Longshore and Warehouse Union (ILWU), said longshore workers had also staged work slow-downs at ports in Los Angeles and Long Beach.