Infrastructure Projects - Construction Technology
A Practical Guide to Construction Techniques and Practice
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Welcome to class 14, where we will examine, removing and replacing a bridge and accomplishing that in a remarkable six months.
Here is a detailed view. You can see some preliminary cutting of the existing bridge has already been done. The roadways have been cut here. You can see the daylight shining through, and the charges are in place on the primary cause of the bridge, and also on the secondary diagonal members. The bridge is now ready for this controlled demolition.
The entire process from beginning to end took about two weeks. You can compare that to the previous bridge, which had similar dimensions where the superstructure was removed in about eight weeks.
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Demolishing the bridge all at once is really ideal. Nothing could be more cost-effective and nothing could be faster than this method, but where's the traffic? Where is the MPT plan? They had a very simple plan here. They closed the bridge. Of course, they provided an alternate route, which probably added five or ten minutes to your trip. It was certainly an inconvenience, but it was really manageable.
The community had to choose between several options. The bridge could have been replaced in sections, which would have taken several years and certainly impacted the community and the flow of traffic throughout that duration. Instead, they accepted a proposal to demolish the bridge. That's really quite a remarkable undertaking, but they were assured that the bridge could be removed and replaced and reopen to traffic in just six months. The way that was accomplished was by adopting a method which is somewhat unusual, Instead of a single contract managed over the duration by a single general contractor, they created three separate standalone contracts. The first contract was to furnish the structural steel. If you're familiar with these projects, you know that the shop drawing approval alone could probably take six months and then the steel has to be ordered from the mill and then fabricated. Certainly, that could be another six months. That needed to be handled in a separate contract and that's what was done here. The second contract was for removing and replacing the existing superstructure. There the community was promised that that could be turned around in six months, and it was. Six months is still very ambitious, even though the steel has been fabricated in advance and is available to you immediately. The contract also provided an incentive for timely completion, as well as a penalty for failure to reopen the bridge on schedule. There will also be a third follow-on contract, which will reconstruct the approach roadways to the new bridge. The existing bridge piers were demolished. They were not reused, and two new piers were constructed. Here, you can see the foundation for the new pier, which are drilled in piles.
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