Interview with Jacques Lequy

Jacques Lequy, site supervisor [00:00] When you’re talking about concrete, and you’re saying it’s a 5,000 pounds per square inch, that means it can withstand pressure up to 5,000 pounds per square inch. If you take, let’s say, a three feet by one square inch column. If it’s a 5,000 pounds, it’ll hold. But if you lay that same column on its side and put some pressure on it, it’ll break. It’s not built to resist certain tensions. That’s why you have to reinforce it by putting steel bars inside. In addition to that, we put the prestressing cables. These are cables that we put within the structure itself. When the concrete hardens, before it’s completely cured, it still has some elasticity. Then we pull on the cable. By pulling on the cables, the concrete is forced to inflate. Instead of being flat it will rise up so that when we put it in the water, and put the weight on it, it will flatten back down. It’s the same thing with the girders on a bridge. When trucks are crossing the girders aren’t flat, they’re arched. There is a certain prestress there. When you put those girders in the deck of the bridge, it makes it stronger, and that’s on top of the steel frame already inside. [01:23]