I-35 / US 30 Flyover Progress

[Cycsk]

The difference is that in the new design there is a lot more time to make that merge. The issue with the standard cloverleaf design (and why it is no longer used) is because you have traffic trying to merge on and off the interstate in a very short stretch of road. At this intersection today you have about 600 feet of space to merge. If you're going the speed limit, it takes about 6 seconds to drive from one end of the merging area to the other. You're realistically not going to merge in there right at the far end of the merging area, so really you only have 3-4 seconds. If traffic is busy at all, there are going to be 2-3 cars in there at least so now you have to find a gap and get into it all in that short time. Meanwhile you have to judge the speed of the other cars and speed up or slow down as appropriate. The cars coming in are driving in a curved path so it's really hard to judge their speed. And if there's a semi or two in there, forget about it. You have almost no opportunity to do the merge.

In the new design, you have a few thousand feet to merge with people who are going the same direction and same general speed as you. You have way more time and it's a much easier task.

When you do traffic design you are not designing the highway for the optimum driver, or even the top third. You could design the bare minimum space needed to merge and assume perfect meshing for traffic and it would work if only the best professional drivers were allowed on the road. Realistically, you have to design to make things easy because people aren't perfect and you can't expect them to be 100% tuned in 100% of the time.

Exhibit A:

http://www.kcci.com/article/caught-on-video-semi-pushes-teen-s-car-down-interstate-35/6922810

 

[Clones123]

Sorry, but there's a reason they're changing it. That much traffic merging and exiting, combined with limited visibility from those merging (because of the curve) at the same short stretch of road at different speeds (traffic on the ramp is going to be slower) is a recipe for failure. The cloverleaf has inherent issues

My biggest fear with this new flyover is that people will still use the ramp going 30 or 40mph, slowing down and backing up traffic. Typically these ramps are designed so you don't have to slow down from the speed limit, such as the ramp from EB 30 to SB 35. You can go down that ramp going 65 easily.

 

[Sousaclone]

My biggest fear with this new flyover is that people will still use the ramp going 30 or 40mph, slowing down and backing up traffic. Typically these ramps are designed so you don't have to slow down from the speed limit, such as the ramp from EB 30 to SB 35. You can go down that ramp going 65 easily.

I see that happen every now and then here in Houston. There are some monster flyovers that you can go through at 55-60 mph without batting an eye and all it takes is someone going 35-40 and you start getting a backup that feeds down the line.

I will say one thing, Texas does know how to do an interchange. Nothing like a 5 layer interchange with the top flyovers so high/steep that you feel like your on an amusement park ride.

 

[AgronAlum]

Can a traffic engineer tell us why the exits ramps are so dang huge here? It seems like they could have done the same things in about 1/4 of the space.

The exit ramps are normal. I think you’re looking at the roads they’re rerouting to connect to the existing roads. They run along side of the new ramps. The most obvious being on the NE side where it curls around the dome house.

 

[scottie33]

Heard that the embed plates were installed in the wrong locations so they have to chip down 18" on ALL bridge piers, reinstall embed plates, and place concrete back to elevation.

They also delivered the main bridge beams and they look 10' tall on the ground.

 

[jbhtexas]

I will say one thing, Texas does know how to do an interchange. Nothing like a 5 layer interchange with the top flyovers so high/steep that you feel like your on an amusement park ride.

And when drivers (car and semi) decide to take them on in ice storms, they become nearly a literal amusement park ride...

 

[DeftOne]

Heard that the embed plates were installed in the wrong locations so they have to chip down 18" on ALL bridge piers, reinstall embed plates, and place concrete back to elevation.

They also delivered the main bridge beams and they look 10' tall on the ground.

I just heard something similar regarding the tops of all the piers (cast-in-place anchor bolts too far out of location).

You're close...the girders are 9 feet deep (I downloaded the bridge plans).

 

[scottie33]

I just heard something similar regarding the tops of all the piers (cast-in-place anchor bolts too far out of location).

You're close...the girders are 9 feet deep (I downloaded the bridge plans).

Can you provide the link to these documents, I was trying to find them earlier.

 

[ajk4st8]

I just heard something similar regarding the tops of all the piers (cast-in-place anchor bolts too far out of location).

You're close...the girders are 9 feet deep (I downloaded the bridge plans).

I was just told this exact same thing but someone working on the project. Said it's a complete crapshow.

 

[Sousaclone]

I was just told this exact same thing but someone working on the project. Said it's a complete crapshow.

That's not going to be a fun one. I haven't been on anything quite that bad, but I've been in a couple of pretty ugly rework situations before. Nothing like going in to work every day knowing you are going to get your ass kicked.

 

[DeftOne]

Can you provide the link to these documents, I was trying to find them earlier.

Here you go...

https://iowadot.gov/contracts/biddocuments/september_2016_letting/20SEP005.zip

It's a large zip file (102 MB) that contains multiple folders and multiple designs. The flyover bridge plans are located in the \Plan\85-0354-183 folder.

 

[kingcy]

How does this all work though? Who foots the bill for all the screw ups? I assume it's written into the contracts, but shouldn't the contracting company be footing the bill for all this, not the state?

I am sure the contractor marked it up plenty and will still be ok in the end.

 

[Sousaclone]

I am sure the contractor marked it up plenty and will still be ok in the end.

Eh, you'd be surprised. Margins tend be pretty thin when there are 5-6 bidders on a contract, especially on a relatively simple contract like this one.

I don't know what there markup is, but if it's more than 5-10% I'd be very surprised.

 

[IcSyU]

I am sure the contractor marked it up plenty and will still be ok in the end.

I doubt it. I'm guessing the margin is under 10% which isn't much with the multitude of things that can go wrong on a project like this.

When something major goes wrong on a small project it isn't a big deal because margin on your big projects will "cover" it. When something goes wrong on a huge project like this people go out of business (whether it's the construction company or engineer's fault).

 

[cycloner29]

Drove past this yesterday and saw all the exposed rebar from removing all the concrete from the two tallest pillars. Yikes! Just have doubts about them taking part of them off and then creating a base again for the beams to set on. I should trust the process but after the first couple of issues, removing the first pillar and redoing it, then this issue..... I just have my doubts. Remember the bridge in Minneapolis???

 

[khardbored]

Eh, you'd be surprised. Margins tend be pretty thin when there are 5-6 bidders on a contract, especially on a relatively simple contract like this one.

I don't know what there markup is, but if it's more than 5-10% I'd be very surprised.

I doubt it. I'm guessing the margin is under 10% which isn't much with the multitude of things that can go wrong on a project like this.

When something major goes wrong on a small project it isn't a big deal because margin on your big projects will "cover" it. When something goes wrong on a huge project like this people go out of business (whether it's the construction company or engineer's fault).

So . . . is this a simple project or a huge project?!?!?

 

[IcSyU]

So . . . is this a simple project or a huge project?!?!?

My assumption is it's a large project for them or they wouldn't be so far out of their footprint.

 

[mj4cy]

So . . . is this a simple project or a huge project?!?!?

Huge for Ames/Iowa but just another project most any other place that does these.

 

[Sousaclone]

So . . . is this a simple project or a huge project?!?!?

My assumption is it's a large project for them or they wouldn't be so far out of their footprint.

Huge for Ames/Iowa but just another project most any other place that does these.

All of the above are correct. For central Iowa, it's a probably a fairly large project (admittedly, I don't know the IA market). In the bigger picture, it's not really that big of a job compared to other work.

My sense of scale is a little warped. I'm just starting a $600 million project right now and the job I came off of in early spring, my portion of the job was $20 million in labor alone, with a $70 million precast contract. All wrapped up into a $3.1 billion bridge contract. (/humble brag)

 

[scottie33]

Finally got a chance to look at the drawings and see what they missed.

Looks like they forgot to install the 1 1/2" diameter anchor bolts that are to have 18" min. embedment into the pier itself. There are no embed plates that get cast into the boxes at the top of the piers. This appears to be why they have to chip down the distance that they are and will have to repour back up to elevation with the anchor bolts embedded in the concrete. It would appear that they forgot to install these at both the bridge abutments as well. These anchor bolts hold the disc plate and sole plate that support the bridge girders and allow the bridge to expand / shrink during changing temperatures.

Unfortunately, I don't see any anchor bolts coming up through the top of any of these piers...