If you haven't been to Chuck E. CheeseTM or north of 152 on I-29 lately, it's changing. The new Old Tiffany Springs Road Bridge over I-29 is going gangbusters. If you don't know what I'm talking about, the old narrow two lane farm bridge that used to serve the lost city of Tarrytown is being replaced on alignment with a new four lane bridge that completes the arterial grid around the I-29/152 cloverleaf. Even though it's a state interstate bridge, it's being paid for by federal funds obtained by KCMO and funds from the KCI Corridor TIF.
The project will also add sidewalks and finish a huge gap in the Route 152 Trail and make that a continuous corridor from North Amity to US 169 (see this 152 Trail post for better explanation). If you're feeling a need for a life threatening rush and can't afford sky diving, try riding your bike over the bridge with its 30" or so concrete railing and steady flow of cars like this.
The project will also include an underpass for the future KCI Corridor Trail along the east side of I-29 and the underpass is in place. Underpasses are more than pedestrian only HAWK signals but don't have the threat of a car going 45mph hitting a child or family crossing the street nor does it impede traffic flow by making cars stop. This picture is looking north and shows the amount of dirt needing to be brought in and the bridge abutment and retaining wall partially complete on the left.
In the picture above, you can see the construction crane and what looks like a red steel truss or 3D ladder. That red contraption is the hammer for the steel piles that are necessary to build the bridge support.
Basically bridges are supported by "abutments" which are platforms for the bridge beams to sit on. The weight of the bridge and vehicles on it is transferred to the top of the abutment. However, the abutments alone can't support the load. In this case steel piles are driven into the ground until they hit a solid bedrock surface so that there is no settlement of the bridge.
Some of the time bedrock is not always available and so the steel piles are driven into the soil until the pile can no longer be driven. These steel piles act like nails and the friction between the soil and the steel pile provide enough resistance to support the bridge. I tried finding something on the internet that showed it but couldn't find what I wanted so I drew up a back of the letter illustration of how loads are transferred from the piles and support the bridge.
How does the pile hammer work? Something like this video I captured for the Shoal Creek Trail bridge behind Maplewoods Community College.
Every time that hammer hits the steel pile, it's called a "blow." Piles are marked with chalk in one foot intervals to show the depth and rate at which the steel pile is being driven into the ground. Somewhere some program or engineer does all sorts of calculations that calculate the number blows per one foot which the steel pile will meet resistance ie when the hammer hits the pile 42 times and it goes one foot deep, the hammer can stop pounding.
However from my observation is the pile gets driven and driven until a distinctive "ping" sound starts and the hammer pounds a few times without any movement into the ground at all. Piles are steel H-beams and are usually very long in this area as shown below.
Once the piles are driven, earth or usually rock is backfilled and compacted. This is looking west from the east side of I-29 at driven piles. These will be marked at the right elevation and a cutting torch will cut them to a uniform level.
A reinforcing steel basket will be placed around the piles and then the concrete abutment poured. I don't have a picture of that frame because the contractor hadn't started work on it yet but you can imagine it from the picture below.
The bridge crosses both I-29 and Prairie View Road so it has three spans and two "intermediate bents" or piers. This is the pier on the west side of I-29 and it shows the formwork. I really wish I had a picture of the wire frame because it's rather impressive.
The project will raise Old Tiffany Springs Road just north of Chuck E. CheeseTM to the same level as the parking lot to the south and will require a lot of dirt. This is looking east towards Skyview and all of that will be filled in with dirt.
The new road west of I-29 requires a lot of dirt and retaining wall which is going up quickly. This picture was taken a week ago and looking west over I-29 at the new road just south of Honda of Tiffany SpringsTM.
Notice the hanging equipment from the crane way in the air and wonder why that's a common construction site sight? Theft prevention. It's hard to steal a pump or generator when it's 50+ feet in the air.
The project looks even more impressive when over on North Congress looking to the east.
One thing about concrete is that it is really strong when it is compressed or crunched. It is not strong at all when it is in tension or stretched so those round columns in the center need steel within the concrete to provide strength against stretching. Here is how much steel and how it has to be tied all together like Tinker ToysTM.
Vertical concrete columns may appear to be compressed but the weight of the load actually creates tension on the outside of the column. The reinforcing steel cages provide tension support and create the strength to support the bridge loading. I tried another back of the napkin sketch trying to illustrate how it works. If a column doesn't have that steel reinforcement, the column will "shear" at a 45 or so degree angle.
The grading on the west side of I-29 is coming along and the storm inlets and pipes appear to be in place. This is looking east towards I-29.
Did you know that construction grading is quasi-automated? Some contractors use computer aided drafting and modeling software to create 3D models which are then uploaded into a GPS type system. These models are used to guide the operators on where and how much to dig of fill. This is a GPS type system attached to the blade of a bulldozer. The operator has something in the cab that tells him/her how much to lower or raise the blade to get to the right elevation.
The retaining wall for the project is a mechanically stabilized earth (MSE) wall (us engineers are great with acronyms that make sense to only us.) The wall will be these narrow MSE panels interlocked together and then held up using friction created by gravity from the "backfill" material on a vertical tie. In this case, the backfill material is rock and I'm running out of envelopes.
This is looking east along the north side of the new road and shows wall panels without the tie backs. It also shows some black "filter fabric" between the rock and the dirt. The filter fabric is supposed to keep the "fines" or small dirt/clay particles from eroding into the rock and causing water to saturate right behind the wall. Water is bad in these situations because it weighs a lot and adds unnecessary stress to the wall face. The principle is very similar to the "soil nail wall" installation I explained in 2012.
Here's a ten year old with angst that he was hauled out onto another construction site and a six year old who was super excited for perspective on how big these panels are.
Here's a shot of a tie back buried into the gravel and how it's held onto the MSE wall face. You might also be wondering why some of the steel is green and some is not. The green is a coating that is supposed to keep water off the steel and prevent corrosion/rust.
Now bridge designers have other tools in their toolbox and on this one, they used another type of bridge abutment support......the drilled shaft. Rather than hammer steel H-piles into the ground, a drill digs out soil to a solid foundation like bedrock and then the shaft is filled with concrete. I'm tired and it's late so geek out on drilled shafts here. Drilled shafts will hold up the west side of the bridge.
Why would this be different than the other side? Well the west side is 15 or so feet in the air from the existing ground so there's no way to drive pile and use the dirt to hold it in place I'm assuming. In this case, round metal culvert pipes are placed after the drilling is done and will be filled with concrete. That's why you see the shiny tubes in this picture. To the left of the concrete panels right where I am standing is a 10+ foot drop.
The boys had fund dropping rocks into the drilled shaft tubes and then listening for water. They didn't believe me when I said it was 30+ feet deep but once I dropped a rock to show how I knew what I was talking about, they had about five minutes of fun listening for the splash at the bottom of the tubes.
As we were wrapping up, the six year old loudly pointed out the porta-potty in the median and I had to explain that the crane operator and anyone in the middle of the interstate just couldn't find a non-conspicuous place to take a whiz. The crane is in the middle of the interstate to drive the pile for the middle pier and there is a lane closed each way on I-29 so you might hit some stop and go traffic getting to KCI.
KCMO has a project website for official information which you can find here. Work should progress pretty quickly once the piers are in place and they place the bridge beams and hopefully it's all done and ready for Black Friday because we all know we want to make sure Zona Rosa is easily accessible for Christmas shopping...….
It's moving right along...looks like they have all the concrete girders in place. As someone who has to dodge cars to bike from PHHS area to connect onto the trail spur behind CEC it's awesome.
Posted by: Northlander | 07/09/2019 at 02:12 PM