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Fire Collapses Oakland Freeway as Steel Supports Fail

by MANUEL GARCIA, Jr.

At about 3:30 AM on Sunday, April 29, 2007, a tanker truck collided into the right side guard rail of a freeway ramp from Highway 80 east (Richmond, Berkeley) to Highway 880 gsouth (San José), rolled onto its right side and exploded into fire. The driver escaped with burned hands and was later hospitalized. This fire burned directly under another freeway ramp, in the exiting direction of the Bay Bridge in the city of Oakland along Highway 80 eastbound, onto Highway 580 eastbound. This intersection of Highways 80, 580 and 880 in Oakland near the terminus of the Bay Bridge is called “The Maze”, which accurately describes the scene; some ramps weave over and then under others. On this day the truck accident and fire occurred on one ramp elevated above ground level and yet below another ramp. When seen from above, the accident site looks like a rough X formed in asphalt by the collapse of the upper ramp.

At this moment of writing, it is 7 PM on April 29; my information was gleaned at 11 AM from a KRON Channel 4 TV broadcast, and photos at sfgate.com (San Francisco Chronicle) and kron.com, before noon. So far as I can determine, the upper ramp had collapsed onto the lower ramp by 7 AM, today. It appears that the collapse occurred before the fire ended. The images of the scene, after the fire, show asphalt that had flowed like taffy, and the deformed metal beams at the ends of the fallen section of the upper ramp.

The fallen section seems to about 10 car lengths long, so perhaps about 70 meters or 200 feet (give or take 50 per cent). The entire section is draped over the underlying ramp in a manner clearly indicating that melting and flow of the asphalt road surface had occurred. These ramps were about 2 car widths wide, plus minimal shoulders, so perhaps 10 meters or 30 feet. I could not see deformation of the concrete pillars, nor any clearly melted and resolidified steel. However, the steel supports at the ends of the fallen section of ramp were very clearly bowed and twisted.

The fallen section had rested on two uprights, massive structures of concrete (I’m sure reinforced) in the shape of a Y, with the stem quite broad and the V section filled in; the entire “letter” being flat (of the order of 2 meters, 6 feet or more thick). The steel beams across the width of the ramp section fit into the tops of the concrete Y uprights; and these steel beams also supported a framework onto which the roadway surface of the ramp was laid. I expect these ramps to have been assembled in sections, with expansion joiners between them to allow for the expansion and contraction of the ramp sections due to the variations of temperature during the day-night cycle and over the seasons. Also, we can assume that allowance for thermal expansion and contraction at joints included a “safety factor”, to build in some insurance against the possibility of rare instances of unusually high or low ambient temperatures. Possibly, the design also allowed for car fires and dry ice spills occurring in contact with the structure. However, it is evident that the design considerations did not include the possibility of a tanker truck (presumably with gasoline or fuel oil) burning for considerable time just below a ramp, impacting a large area of its bottom surface with high temperature burning (we assume about 1000 C) and infusing the structure with a massive quantity of heat.

I think the collapse proceeded as follows.

The metal supports below the upper ramp heated and expanded. The heating and expansion were far beyond design expectations. The lengthwise roadbed supporting framework expanded between the massive spanwise beams at the ends of the section, at the concrete Ys. The constrained lengthwise expansion created very large stresses within the framework (whose details I do not know, presumably metal trusses supporting metal plates on which concrete, then asphalt was laid); and this framework bowed downward since its ends were pinned. Why not bow up? Because of the downward force of its weight, and that of the roadway it supported. A similar constrained thermal expansion occurred to the spanwise beams at the concrete Ys. They, too, bowed down. The entire section of ramp was curling up like a potato chip being fried.

This section of ramp had a slope, one concrete Y was taller. The bowing of the ramp and the stress induced by the constrained expansion put lateral force against the concrete Ys. Because of the slope, the higher end of the ramp section pushed against its Y support both laterally and upward, popping up, while the lower end of the ramp section pushed against its Y support both laterally and downward, popping down. The high end of the collapsed section rests against the top of the taller Y support, while the lower end now rests at or below the level of the lower ramp; the material in between drapes and sags over the lower ramp. The beams at the ramp ends look bowed and twisted by the action of constrained thermal expansion, or creep (as defined in engineering usage). Metal-to-metal joints at the tops of the Y supports were probably sheared at the actual moment of collapse, so there may be some metal debris from these locations that show “clean breaks.”

We will have to wait and see if melted and resolidified steel is actually found in the debris. Perhaps none will be found, and we will then have to be concerned about a cover-up here, because there are unconfirmed reports that Dick Cheney was seen leaving the scene, driving an otherwise ordinary-looking van but marked “Acme Thermite Company (Livermore, CA).” If we reject the obvious conclusion that this was a case of controlled demolition by Dick Cheney, then we have to believe the wild speculation that this collapse of a steel-reinforced concrete structure was due solely to a hydrocarbon fire, without prior or coincident mechanical shock and breakage to the structure; a physical phenomenon outlawed by orthodox history (maybe this was a “black ops” job, to help solidify the government’s story about 9/11).

So far, it appears that there have been no fatalities, and that the tanker truck driver’s injuries are not critical. So, aside from the widespread inconvenience (maybe BART and local mass transit will get a boost), this incident may help us learn more about fire protection for our large metal-reinforced concrete structures. Hope they nail Dick and I get a Medal of Freedom.

MANUEL GARCIA, Jr. is a physicist, a native of New York, and perhaps a Tralfamadorian. His discussion of heat and metal and the collapse of the World Trade Center towers can be found at ninelevenconsp11252006.html E-mail received at mango@idiom.com.

 

 

Manuel Garcia, Jr, once a physicist, is now a lazy househusband who writes out his analyses of physical or societal problems or interactions. He can be reached at mangogarcia@att.net

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