Building Mighty Mac

Building Mighty Mac. Mackinaw City Historical Pathway. , The Mackinac Bridge is constructed of three segments – at each end is a post-supported truss bridge and in the center is a suspension bridge segment. This bridge was the longest suspension bridge in the world for decades after its construction. Today most of the longest are in China. , Mighty Mac is an engineering masterpiece designed to withstand crushing ice and winds up to 120 mph. It is also a construction triumph, built for $99.8 million between 1954 and 1957 – on time and within budget. The 4.5 million vehicles which safely cross the bridge each year pay tribute to its dedicated builders, the crews that overcame the harsh winters, and the winds of the Straits. , How the suspension part of the bridge works , Truss bridges, supported by posts, are far cheaper to build than suspension bridges. But the water in the Straits of Mackinac gets quite deep, up to 300 feet, and it was impractical to put posts that deep. , The engineers put an anchor block, or main supporting post, (shown in red below) at each edge of the deep water. Cables, propped up by two towers, were stretched between these two blocks across the chasm. The roadbed dangles from the cables. All of the weight of the roadbed, vehicles, and cables is supported by the pull of the cables on the anchor blocks (the big wide concrete pads where the police cars hide). , The bridge designers determined the required height of the towers, how tall the towers should be, by calculating the bridge span and the desired height of the roadbed above the water. The roadbed is 149 feet minimum above the water to allow for the passage of freighters and tall ships.