Section of I-95 collapses after fire burns under overpass... 15

[JohnRBaker]

Portion of Interstate 95 collapses in Philadelphia after tanker fire burns under overpass

A tractor trailer fire started under an I-95 overpass and spread to the lanes above.

https://6abc.com/interstate-95-collapse-i-95-fire-philly-overpass-tanker/13368736/

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Murph 9000]

Looks like a fairly simple structure, with steel I-beams spanning between the diagonal abutments, lightweight bracing between the beams, and a poured concrete deck on top. Google Street View has pretty good imagery of the underside of the bridge:

https://goo.gl/maps/3JSJ6Gb9dQhUGKUw7

 

[resqcapt19]

From the fire dispatch audio
0622....initial alarm
0627....on scene, requested box alarm
0628....requested hazmat task force
0629....request complete shut down of I-95
0647....notify DOT that NB I-95 has collapsed

 

[FacEngrPE]

Looks like the steel softened sagged, and eventually the weight of the deck, which can not support itself with out the strength of the steel substructure, pulled one end off of the abutment. It took a very hot fire to do this in 20 minutes.

 

[JohnRBaker]

Yes, this image shows the damage and indications as to the intensity of the fire:

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[TugboatEng]

We had a tanker fire under an overpass a few years back in the San Francisco bay area. It caused some spalling of the concrete but there was no structural damage.

https://www.mercurynews.com/2008/10...still-closed-after-early-morning-tanker-fire/

This one was kind of funny. A motorcycle wiped out merging onto the freeway and wedged itself under a tanker truck causing it to catch on fire. Nobody was hurt. I've wiped out on a motorcycle merging onto the freeway... Luckily nobody was injured there, either.

https://www.mercurynews.com/2020/10...place-order-issued-after-tanker-fire-on-i-80/

 

[FacEngrPE]

video: Pennsylvania Gov. Shapiro gives news briefing on I-95 overpass collapse
I have seen the results of 2 fuel tanker fires, both were fortunately on top of a bridge with the result tug reports, spalled concrete. Concrete is a really fire resistant material. Compost construction bridges do not as far as I am aware protect the steel structure with fire proofing as is commonly used in buildings to protect steel members. So direct exposure to fire will heat the steel faster and hotter.

This enlargement from a picture here

https://www.mcall.com/2023/06/11/i-95-bridge-collapse-in-philadelphia-photos/

clearly shows the bridge steel bent in a manner that can only happen when the steel is heated above forming temperature.

Underside of bridge showing steel.

https://www.google.com/maps/@40.024..._5WCGCIojKy_6gxw!2e0!7i16384!8i8192?entry=ttu

 

[MJCronin]

I believe that this was sabotage ... The 9000 gallon Tanker Truck was way, way too accurately positioned !!!

Anybody agree with me ???

MJCronin
Sr. Process Engineer

 

[IRstuff]

The videos are pretty crazy; the overpass was sagging at least 6 inches in a couple of the videos where people were driving on the overpass while the fire was going full blast. No doubt that the steel beams were on the verge of collapse

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[FacEngrPE]

I believe that this was sabotage Y/N?

As an engineer, no I do not think so and not important to the discussion at this time. If i was an investigator yes, needs to be investigated.

 

[sgw1009]

The road going under the bridge makes an abrupt curve to the left just before going under the bridge. My guess is that the gasoline tanker was going too fast for the curve and overturned. But that is just my guess.

 

[Sym P. le]

Brush Fire on I-95 Twitter ...... !!!!!!!!!!!!!!

Be carefull Twitter

If you didn't think folks were vulnerable, these two videos might prompt a rethink.

 

[jerseyshore]

Holy shit, they almost ended up in the fireball. Crazy video. Thank god concrete is so great for fireproofing. So lucky this was early Sunday morning, imagine if this was rush hour, nuts.

What kind of temperatures would it have needed to get under there to collapse these beams?

 

[hokie66]

Steel starts to weaken at about 600F, loses half strength by 1100F, and it is all downhill from there.

 

[dik]

Yup... both loss of Es as well as yield...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[MortenA]

wow - those people really wanted to cross that bridge...

--- Best regards, Morten Andersen

 

[LittleInch]

I would have thought that a risk analysis would have come up with the possibility of a fire in that quite long underpass and designed accordingly. Say using concrete beans? Or adding some level of fire resistance?

The effect of fires in an enclosed space are well known, especially in tunnels.

Not sure who made the decision to close the road but this could have ended very badly.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[FacEngrPE]

This search turns up some interesting items

https://duckduckgo.com/?t=lm&q=protection+of+bridge+from+fire+undernewth&ia=web

A quick skim seems to indicate that designing highway bridges to account for fire risk is a new thing.

The Society of Fire Protection Engineers: Bridge Fires: Fiction or Reality? - Well we have another example.

https://www.sfpe.org/publications/periodicals/sfpeeuropedigital/sfpeeurope6/issue6feature3[/URL]]Introduction

Fire protection engineering has mainly focused on two areas: buildings and tunnels, which have their own standards and about which a large number of studies have been published. What about other types of infrastructure, such as bridges? Are they outside the scope of fire studies? One could think that the probability of a bridge being affected by a fire does not merit special study, but is this really so?

 

[LittleInch]

So when does a long underpass turn into a tunnel?

Might need to be a fire dept SOP to stop traffic when there is a fire under a bridge section?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Lomarandil]

I'll posit the theory that we can't and shouldn't design bridges for every eventuality... And I think this sort of scenario is likely better addressed on the trucking side than the bridge side.