Bringing Down A Bridge Is No Easy Feat. Here's How It Might Happen With The McClugage
It's common knowledge the current eastbound span of the McClugage Bridge is coming down as part of a multi-year reconstruction project. But how it'll be demolished is still an open question. The Illinois Department of Transportation doesn't yet have a demolition plan submitted.
WCBU's Tim Shelley speaks with Souhail Elhouar, chairman of Bradley University's department of civil engineering and construction, about the logistics of bringing down a bridge.
SOUHAIL ELHOUAR: Bridge demolition is such a technical and specialized task. You'll have to be involved in it for quite a while to become an expert. Now with that said, I can provide a lot of general information about budgeted demolition, and talk a little bit about bridges, but mostly about bridge demolition, and what the impact is and so on.
I think that would benefit the public, because at the end of the day, the decision on how to demolish this bridge, when to do it, by which method to do it, it would be really decided by IDOT. They have done this, I mean, a number of times I think as recently as in March, I think they demolished the Utica bridge on Illinois 178. Now, it was built in 1962 and was demolished in March of 2021. I think. So just recently, and there are others that they have demolished.
Also, there are different types of bridges, you know, from like the steel truss cantilever bridge that you see on the McClugage Bridge, the Murray Baker Bridge, and those types. There are different types of bridges and each one of them, the the method of demolition is going to be different.
So, the decision on what best approach to use can only be taken by specialized experts in the field who have access to all the plans and documents and other pertinent information about the bridges and its surroundings. The general idea first, you know, is to probably inform the public about why this is such a big deal. Why don't you just go and demolish the bridge?
Well, there are lots of considerations. But one of the things that we need to understand about structures in general and a structure that is under load, and a bridge is going to be under at least its own weight load from its own way, even if it's not being used. So in those bridges, and these types of bridges like the truss bridge, for example, that is made of numbers of steel. Each number is like an extended rubber band or compression spring in the constructed bridge. Now you can imagine what happens if you take an extended rubber band and cut it. Or if you take a spring that is compressed. They will rebound. And from that rebounding, they can cause extensive damage. So it is something that needs to be done with great care. And quite a bit of study.
TIM SHELLEY: So this is not just a matter of, put some explosives on either side of it and watch it fall. It's a lot more intricate than that.
SOUHAIL ELHOUAR: Oh, absolutely. Absolutely. There are a number of ways to take down the bridge. You just mentioned one of them. Which one to use, they're selected based on for safety and expected cost. Okay. In addition to a number of other considerations, for example, state of the bridge. If the bridge is fairly well ... holding itself and so on, or if it is deteriorating in some areas. The type of bridge and material used.
So, is it a concrete bridge steel bridge, other types of bridge? Even in a concrete bridge, is it a cast in place bridge? Was a pre-stressed concrete that was used? So there are so many different types of bridges.
Also of importance is what to do with the material after the demolition task is completed? Is it going to be disposed of? Or is it going to be recycled? So sometimes, you know, for example, asphalt, if a bridge has an asphalt overlay, asphalt is probably one of the most recycled materials in construction.
And typically, they want to take that material and recycling. Steel also is one of the highest recycled materials in construction, and they probably would like to take it and recycled. Okay, so all of those decisions need to come into play. The type of demolition also. Is it a complete demolition or partial demolition that they're after?
So in this case, most likely, this is going to be a complete demolition of an old bridge that's going to take place. The location of the bridge has an effect on the decision, because you're going to have an impact on the surrounding structures. So that needs to be considered. So if you have a lot of structures that are close by, it's different from if you have a bridge out in the middle of nowhere. Impact on road and river traffic. So for example, if the bridge is on roads, and you want to keep them open for as long as you can, or diminish the amount of time that they are closed, during the demolition process, or also on a river, especially a river like the Illinois River where we have barges going in, back and forth, and boats, and so on. So you want to exact into consideration if there's going to be any closures due to the demolition and how long they are going to be - and then also impact on the environment.
TIM SHELLEY: You actually weighed upon one of the things I've been wondering about, which was the river and the bridge and the barge traffic. Because you obviously don't just want all that stuff falling into the river. If you have to decide, am I going to recycle it dispose of it, but how do you collect it and just keep it from being swept away in the current?
SOUHAIL ELHOUAR: Exactly. Well, swept away in the current with debris that heavy will probably not be easy, but even though they take precautions, because even when they do an explosion or implosion of a of a bridge, so that it falls, and then they plan on of course clearing it and and cleaning up the site right away to open it up for for traffic. Usually, they do have some way or some process to really protect also the environment make sure that the debris or minimize the debris that will be swept away by the current.
TIM SHELLEY: Absolutely. And you also mentioned other structures. I mean, the other span of the bridge is going to remain. So how do you demolish one span without damaging that other span?
SOUHAIL ELHOUAR: Well, that's part of the study. So that's what they will be looking at whoever is going to be designing because it's complete, complete special kind of design. Even though it's demolition, we think about it, oh you're breaking something. But you need to design that process. Okay, so you need to really take into consideration lots of things.
I mean, I can give you an example of actually a bridge where the demolition process didn't go as planned. And this, I think, was a two span pre-stress concrete bridge in Minnesota. I think in 2014, they planned to just demolish portion of it, okay. But damage to the superstructure led to full superstructure replacement. So they just wanted to replace the bridge, I mean, the the pavement area, the bridge, pavement, on the slab, and so on, and replace that. But during the demolition, something went wrong, and the superstructure was damaged. So they ended up having to put the whole bridge down.
TIM SHELLEY: You mentioned the public, you know, needing to understand this process. And I think it's probably not widely understood how just how intricate this process is. The fact that you have to make a highly individualized plan for demolishing. It's not just like there's a, just do it and go, and, you know, it's not simple. So what do you think the public needs to really know about this?
SOUHAIL ELHOUAR: Really, I mean, as far as the public is concerned, that's a good question. You know, it depends really on their interest in it. I mean, as I said, personally, just trust the engineers that are doing it. These are people who have been doing a lot of this for a while, so they have experience, they have expertise.
If you get to watch it, I think it's a great sight to watch from a distance, to look at how a planned demolition takes place, I'm sure knowing I thought because they have webcams and live cams on lots of places. You can probably watch it, you know, live on the internet or watch it later on the internet. I saw the demolition of the Utica bridge, the one I talked to you about. That's available, and you can go and see it blasted by explosives. They just imploded it, and you can see it when it came down all in one piece in the river, and they probably went then and cleaned up right away after that.
But they're typically about four different ways, in general, that you can use to dismantle bridges. Explosives is one of them. So it and it's a very, very well studied process. And, you know, if you look at the requirements to participate, mostly, in general, you have to have experience in it. The company that's going to do it, you have to provide a lot of information about the explosives that will be used, where they will be placed. And all of that is studied adequately so that it only produces the effect that you want to produce. Okay. And that's probably the quickest way. Well, once the explosives... I mean, it takes a lot of preparation. It's loud, it's creates a lot of dust and stuff, but you know, it's probably the quickest way to bring down a bridge or a structure in general.
There is another method where they use hydraulic breakers. So usually these are boom-mounted breakers. They can even be used underwater to break specific pieces of the bridge, and it's also planned so that other pieces may either fall down, and then they pick them up and, you know, dismantle them or so on. This method also does create debris and vibrations.
There's also dismantling. So this is basically the reverse process of building a bridge. It's probably the method that takes the most time. But if you want to typically conserve, you know, a bridge, move it somewhere else. Dismantling is another way. Bridges can be cut to pieces, or actually just dismantled piece by piece and taken away.
There is also a method called bursting, and you've probably used it to split wood. And they do the same thing for splitting concrete. And they can do with either mechanically, or with pressure, or chemically. You know, when if you have a big piece of wood, like you're splitting wood for your fireplace, and you go and take a chisel or something and try to hammer it in until the thing splits in two. That's basically what it is. Okay. So that is called bursting. It's probably one of the quietest ways to dismantle a bridge or a structure in general.
But, you know, those four, which one are they going to use on the McClugage Bridge? That remains to be seen. I really don't have enough information about what part of it is going to be demolished. I didn't have a chance to really look at the new plans either. But you know, I'm sure it's going to be one of them. Typically, they want to go for the explosives because it's probably the quickest after you have set it up and so on. But that doesn't mean that other possibilities or other ways will not be investigated.