A former board president of New Canaan’s defunct teen center said Tuesday morning that the organization’s directors had learned through a study conducted as early as 2007 of a “hinge effect” in the building’s second floor—a part of the Outback’s design and construction that professional engineers now describe as unsafe for the young people it had been built to serve. The danger developed over time as the flooring began to “crown,” and there’s no way the Outback’s board could have known the hazard it would create when the teen center opened in 2001, officials said during a regular meeting of the Board of Selectmen. Yet the first reaction from an engineer who entered the Outback building before it was closed to the public last week was, “ ‘You’ve got to close this building. No one should come in here,’ ” according to Bill Oestmann, buildings superintendent with the New Canaan Department of Public Works. “And when I told them what they were doing there, he explained that having a large dance up there, if you have 100 kids and people moving around, that whole weight load is bouncing going back and forth, and he just said that floor could drop down on one side because it’s just hinged up there,” Oestmann said at the meeting, held in Town Hall.