RALEIGH, N.C. — Crews working on the downtown convention center held a ceremonial "topping out" party Wednesday to mark the completion of most of the structural framework for the $215 million project.

About 1,400 workers have put in more than 500,000 hours on the project so far without a single day lost to injury, officials said. That compares to a national average of a construction injury every 23 seconds.

To celebrate, workers signed a beam that was hoisted to the top of the building and set in place and had lunch with state and city leaders in what will become the convention center's lobby.

Meanwhile, the city is hammering out details for new conventions to host inside the convention center after it opens in 18 months.

Officials on Wednesday announced 42 events have been booked through 2014. Those conventions will result in more than 142,000 hotel room nights being booked, officials said.

Many of the conventions being booked are larger than Raleigh could accommodate in the past. Officials with the Greater Raleigh Convention & Visitors Bureau said each event could have an economic impact to the region of $500,000 to about $2 million.

The North Carolina Alliance for Athletics, Health, Physical Education, Recreation and Dance, for example, has held its annual conference in Greensboro for 20 years. But the new 500,000-square-foot convention center prompted the group to commit to moving its annual event to Raleigh for three years.

"We couldn't be here (in Raleigh) because of the size. We couldn't have enough sleeping rooms or meeting space for our convention of 2,500," alliance executive director Ron Murrow said.

From the beginning, city leaders said they expected to market the convention center to regional and state associations. But four international groups have also already signed up to hold their worldwide conferences in Raleigh.

Laurie Okun, the director of sales at the Greater Raleigh Convention & Visitors Bureau, credits a new group called Capital City Connectors for the bookings. The groups includes prominent business people in the area who can use their connections to attract large conventions.

"The international conferences coming here are literally coming because there was a catalyst -- either Research Triangle Park or the city of Raleigh -- someone that said, 'Look at our city,'" Okun said.

Before construction even began, a study was done on how many bookings the convention center should have in its early years. Okun said the facility is 50 percent ahead of predictions.

Still, Mayor Charles Meeker said there's more work to do.

"The main thing is to get the repeat business in 2010, 2013 to really sustain it over the years," Meeker said.