Engineering against moving ice
The Confederation Bridge connects Prince Edward Island to mainland New Brunswick across the 12.9-kilometer Northumberland Strait. For about four months each winter, from December to April, sea ice covers this passage, presenting a formidable engineering challenge. Ice floes, some measuring up to four kilometers in diameter and a meter thick, are constantly in motion, driven by currents and wind. The bridge's design had to account for the immense and destructive power of this moving ice.
The primary defense consists of 61 piers, with 44 main piers spaced 250 meters apart. At the waterline, each main pier is protected by a massive, cone-shaped structure called an ice shield. These conical shields, which have a 52-degree slope, are engineered to manage the horizontal forces from ice floes. Instead of meeting the pier with blunt force, the moving ice rides up the angled surface of the cone. This action uses the ice's own weight and momentum to bend and break it into smaller, less threatening pieces that are then deflected around the pier shaft. The shields are constructed from high-performance concrete, with some also featuring a 1-centimeter-thick carbon steel skin to resist abrasion.