Re: funky DOT-speak on Chesapeake Bay Bridge repairs

On Aug 29, 11:37 pm, jdunlop <jdun...@xxxxxxx> wrote:
On Aug 29, 10:09 pm, "Scott M. Kozel" <koze...@xxxxxxxxxxx> wrote:



jdunlop <jdun...@xxxxxxx> wrote:

"Scott M. Kozel" <koze...@xxxxxxxxxxx> wrote:

There is no way that that a truck going 50+ mph on a 26-foot-wide
bridge roadway can hit a parapet at a 90 degree angle.  Mathematically
it probably couldn't be more than 20 degrees, and a combination of
rollover and impact at that angle might only knock down a short section
of the parapet, or possibly none at all.

You are right about a truck not fitting, unless it was jackknifed
(which is likely given the situation) but I wasn't the one who said 8
feet, it was in the press release mentioned in either the first or
second message.  I could see the cab hitting at close to a 90 degree
angle, but the trailer would almost have to take out more of the
barrier.

The front of the tractor may have been at a 90 degree angle as it
skidded and hit the parapet, but if the truck was moving at high speed,
the angle of forward progress would have most likely would have been not
more than 20 degrees from the highway centerline.  In that scenario the
front of the tractor would scrap along the parapet from some distance.

There was a similar situation on I-40 near RDU Airport a few months
back.  The truck was cut off, lost control and went through the median
guardrail at essentially a 90.  Of course, there's four lanes there,
so the truck had about 46' to "turn."  That crash had some locals
asking why NCDOT didn't have a concrete NJ barrier there.  I doubt
that would have stopped the truck, either.

Was that NCDOT's excuse?  Even on 4 lanes, there is no mathematical way
that a truck moving at highway speed could hit the concrete median
barrier at a 90 degree angle.  It probably couldn't be more than 30
degrees (but they are still not designed to sustain an impact like that
from a large truck).

Excuse?  No.  Explanation, yes. And it would be physics, not
mathematics.  The truck starting at highway speed doesn't mean that it
winds up hitting the barrier at the same speed (or the same spot on
the highway where it started skidding/braking/etc.)  What
"mathematics" would you say that would prevent this situation?

In any event, I believe we're all saying that any highway median
barrier is designed for a glancing blow, not a blow from a steeper
angle, and that given the relative rarity of the situation, it is not
reasonable to expect to construct such a barrier in most cases.

There is no question that strong enough barriers can be built - at a
cost and I think that is part of the problem.

But it would also seem that speeds for the larger vehicles .. should
be reduced if we know that they can go through those barriers.

The deal on the Bay Bridge for me is that the DOT was saying two
things:

1. - that radar inspection showed rebar corrosion whereas visible
inspections did not.

2. - that the barriers were safe and operated as expected and that the
truck was just too big and had too much inertia and went through a
barrier than they knew could not hold it ....

but the problem I have is:

1. - hidden rebar corrosion is a known issue and that in saltwater
environments ..it would be prudent to INCLUDE radar inspections as
part of routine inspections.. at least periodically.... it just cannot
be that big of a cost concern to not do it. You could have a small
number of units - for statewide inspections.

2. - if the barriers were fine - then why are they retrofitting them
now.. and having traffic backups as a result?

the two statements - that the barriers are fine ...but we must
immediately retrofit them.. and cause traffic disruptions (they are
telling people to take alternate routes that require several hours of
additional travel time) ... those statements are not consistent.
.

Relevant Pages

  • Re: funky DOT-speak on Chesapeake Bay Bridge repairs
    ... bridge roadway can hit a parapet at a 90 degree angle. ... skidded and hit the parapet, but if the truck was moving at high speed, ... asking why NCDOT didn't have a concrete NJ barrier there. ...
    (misc.transport.road)
  • Re: funky DOT-speak on Chesapeake Bay Bridge repairs
    ... The WWB was and is a steel structure; ... the post tensioned bridges use those cables to keep ... strength a barrier should be for a given situation... ... truck, for example), but not a semi. ...
    (misc.transport.road)
  • Re: NYS Thruway tolls at Spring Valley (Exit 14A)
    ... but I think the barrier there (back when it ... It then went to a fixed-rate cash toll (in both directions? ... transponder than passenger cars, I guess there are sensors that can ... It's a truck only toll, and they take a picture of everyone and ...
    (misc.transport.road)
  • Re: funky DOT-speak on Chesapeake Bay Bridge repairs
    ... adding a concrete median barrier would have been prohibitive since the ... that can withstand the impact of a large truck; ... Here's the bridge rail I'm familiar with that is considered truck safe ... Which means that either the visible inspections were not conducted ...
    (misc.transport.road)
  • Re: funky DOT-speak on Chesapeake Bay Bridge repairs
    ... The truck starting at highway speed doesn't mean that it ... > I-40 in that area has a wide enough median that adding a concrete median barrier would have been prohibitive since the ... The two left lanes in each direction ...
    (misc.transport.road)