Infrastructure Projects - Construction Technology
A Practical Guide to Construction Techniques and Practice
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Now we're up a few stories, and we're getting into the rhythm of pouring the upper floors. The floors are all pretty much identical, and they can get really high production rates. The forming is basically done with loose pieces. This is formed with sticks. It's as simple as that. There are wooden posts, then there are members that run across the posts. In this view, they're running from left to right. Then there are the members that are running up and down in that direction. They're all loose pieces. A man can carry them. They're all easily managed. You can cover a huge area in no time at all.
You can see how quickly this goes. The labor who's carrying those stringers can barely keep up to the guys who are dropping the sheets of plywood. They actually get into a little conflict here. He's already fallen behind. He doesn't know where to put this piece, but he knows it belongs under the plywood, and he's very determined to do this thing correctly. He's telling the guys to give him a break because they're ignoring him, so he takes matters into his own hand. What looks rather chaotic is a very carefully orchestrated system, and he understands exactly how many stringers are needed in each bay, and he's determined to get it right. You can make out all the vertical members. Of course, they're not striped, you just seeing the sunshine coming through the stringers, but they're pretty closely spaced. There's a screw jack on each one, to set it to the correct height, but they're not exactly all perfectly plumb. It's kind of a hurry up job. It certainly gets the job done. They're raising bundles of rebar. This fits in very nicely with our discussion about tower cranes.
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These people are using wire rope slings, which is the way I pick up bundles of rebar or pieces of structural steel. I have never seen these fail. Responsible people do look at them, and there is a point where the wire rope sling, because they look worn and needs to be replaced. But it is tremendously strong and, because it works as a choker, it's hard to imagine the rebar ever getting away.
There's a line hanging from the end of the rebar. That's a tagline, and that's used to get control of the load. Sometimes the load can just rotate slowly. You really don't want to grab it with your hands. Using the tag line, you can control it. They're going to set it down on a series of horses, which is a great idea. Typically, in the heavy construction business, I see them always dropping the rebar on the ground, but setting it on the horses first of all, makes it easy to take the slings off -and it's a lot easier for the workers to pick up the pieces when they're waist-high, instead of bending down and lifting them off the ground.
They would drive along the deck and then apply their brakes and tip their load of concrete. Every time they applied their brakes, it was a tremendous horizontal Force applied on the formwork. Without this diagonal bracing, the entire floor of forms could collapse. This is critically important in this application and in any application. Your mind gets focused on the vertical loads, but there are these unpredictable horizontal loads from the wind or from the sudden breaking of equipment. These need to be taken into account.
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