Why do they make roads that cause porpoising?

Yep, the bad news is concrete has rough joints and is more expensive.

The good news is that it lasts a long, long time...or is that the bad news?

2oldman wrote:

sabconsulting wrote:
More recently they have been replacing it with tarmac, including a newer type which seems to drain water better and cause less tyre noise

Tarmac.. is that asphalt?

I find that most concrete freeways are bouncy and rough. And I conclude that concrete is less expensive than asphalt.

Quite the opposite. Yes asphalt provides a better initial ride but its service life is only a fraction of concrete. Concrete is considerably more expensive.

I've not seen this personally in newer pccp roads. Maybe all dot's don't stagger control joints.
I've used 2 different methods to control this (by spec). Either randomly stagger the control jts or cut them at less than 90 deg to the traffic direction so both wheels don't hit the jt at the same time.

valhalla360 wrote:
Low bid: The contractor has no incentive to do anything not specifically in the contract. To a degree, this can be addressed by writing tighter specs but it's a constant battle with the contractor trying to save a penny on construction costs. There are other methods of letting projects but they also have down sides.

Purpose built: I can guarantee no contractor, designer or official wants to be on the stand and explain why they "purposely" created a dangerous situation. (we are talking freeways here not speed bumps on subdivision roads)

Settling: This is often the case with problems that develop after a few years. The slabs don't curl up as they "dry".

Nope, but under some conditions they curl as they "cure."

free radical wrote:

mkirsch wrote:
Just got back from the "big" camping trip of the year.

The last 5 or so miles on the East end of Interstate 490 in New York is fairly new concrete. My truck is nothing special, a regular cab long bed with the most common pickup truck wheelbase on the planet.

I have to drop down to 50MPH on this stretch of highway to keep my head from bouncing off the cab roof! Doesn't matter loaded or empty, it bucks like a bull moose in heat.

If I maintain the 65MPH speed limit, the truck quickly becomes uncontrollable. It's downright dangerous. Even my DD gets to galloping on that stretch of road.

If my truck does it, EVERY regular cab long bed that passes through there has to be experiencing the same thing. It's a function of wheelbase and the seams in the road.

Hundreds of trucks like mine, maybe thousands, pass through that area every day.

Why on earth would the DOT spend millions to lay down a road that they *KNOW* is going to set up such a dangerous harmonic?

Ive experienced the same problem in Edmonton on Anthony Henday dr ,and its brand new concrete surface!!
I figured its probably those gaps are made wide on purpose so the concrete can expand and contract,as the temperatures can vary from minus 30 in winter to plus 30 in summer,,
but since its only small section of that road its probably some design fault ..

That's strange with the Henday Jr. I know a few people on that project. Experienced with concrete paving too. Not sure what the cdn hwy spec is for control it placement though.
Fact of the matter is concrete moves, swells, shrinks, edges swell more than the mass.
It can be controlled by proper jt placement to a great extent but concrete is still a science experiment.

sabconsulting wrote:
More recently they have been replacing it with tarmac, including a newer type which seems to drain water better and cause less tyre noise

Tarmac.. is that asphalt?

I find that most concrete freeways are bouncy and rough. And I conclude that concrete is less expensive than asphalt.

bhoat wrote:
We have a good section of concrete bridge near my house going over the intercoastal waterway. All vehicles porpose going over this.
I was told when they pour a section of I-Beam for the bridge, then place it, it will have an engineered pronation so when the top is poured, the weight will level out. Sometimes they are a little off.

Yep that happens on bridges sometimes. More so with concrete girders then steel as it is much more difficult to dial in exact camber with post tensioned concrete due to shrinkage and creep than steel with more consistent properties.
With concrete girders sometimes 100% of the dead load deflection is not taken out intentionally to account for additional deflection of service loads and time stress vs strain.

I-5 north out of Bakersfield is so darn bad my Right-rear tie-down broke loose, heavy camper seemed to be bouncing about like a rag doll, I doubt this is too good on the superstructure... Stopped and re-centered camper and reattached fast-gun...Since then, I've added two more leaf$ per each side of the dually's rear. Empty, truck bed now 2" higher than stock, spring shop says that rear 'spring capacity' now exceeds that of a 4500.

Happy Camping,

3 tons

...

Porpoising occurs when bumps in the road match the natural frequency of the truck suspension. Unfortunately all automotive suspensions are tuned near the same creature-comforting low frequency. Adding adjustable Rancho shocks set to high might damp it.

About 20 years ago, part of I-94 through North Dakota was poured with immediate high joints. It was fixed by grinding off the humps/joints. Carborundum stock must have climbed the day that contract was signed.

Some sort of later I-94 foul-up caused a pair steady 12" by 4" block cuts to be made every few feet to cut some sort of imbedded rod or cable, ostensibly to prevent a similar bounce. Thousands and thousands of cuts.

I blame it on progress. Whereas workers used to accurately level stuff (think still surviving Roman roads) with string and bubble-levels and understand what the heck they were doing, now it is done with "buzzword" lazers, and nobody onsite understands, or cares, what the automatic leveling machine is supposed to be doing.

I submit this is similar to cock-eyed automatic lazer tire alignment machines in vehicle service bays everywhere. I just bought a "pre-owned" truck with fairly new tires and concurrent new suspension parts. The nearly new tires... aligned-by-lazer... were obviously wearing in an over-toe-in condition requiring me to eyeball them back to straight ahead specs the old fashioned way. Not to mention, I think the new balljoints are torqued too tight.

Geez. What happened to good ol' common sense.

Wes
...

Stefonius wrote:

nycsteve wrote:
Reason... The miracle of the lowest bid.

And we have a winner!

Many people are reporting this issue in regions that have freeze/thaw cycles.