The pictures of the Baltimore roof collapse made me recall the former Ann Arbor backshop that formerly "sheltered" Pere Marquette 1225. Some of the photos seem to show damage to the upper courses of the brickwork, and made me wonder if the failure wasn't some kind of interaction between the brick and iron parts of the building, as outlined in the thoughtful post at the top of this string.

We wondered a lot about that kind of possibility in the course of giving extreme unction to the Owosso building over several years, before finally executing it with a power shovel two years ago. Old brickwork is not necessarily static, and we learned not to rely on it.

Some of my more pungent memories of the Owosso building include one of the authors of an above post, a consultant with considerable engineering background, who came to operate Locomotive 1225 in our "Engineer for an Hour" program. He rushed eagerly into the 1887 brick-and-timber structure (if I may use the phrase loosely) to see the engine. He got about three steps in, long enough for his eyes to adjust to the dimness, and then stopped, looked up, and got a wide-eyed look on his face that I will always remember. Then he decided he could wait until the engine was pulled out for a closer look at it.

A famous railway preservation editor once remarked at length on the "ambience" of our former home. I tried to explain to Mark that if ambience includes watching the roof leakage flow through the electrical junction box before it forms a skating rink on the floor that I would take modernity any day.

I recall all this to point out that anyone who inhabits a 19th-cenbtury building might have to face the fact that when everything is subtracted that poses a leakage, fire, or structural hazard to the people and collection inside it, that some 19th-century buildings might wind up like the one-hoss shay. I sure hope this is not true of the Baltimore building.

PM 1225 is now in a kind of plastic wrapper that despite its faults and mud "floor" will never burn or fall down around the engine.

Aarne Frobom
The Steam Railroading Institute
P. O. Box 665
Owosso, MI 48867-0665

> PM 1225 is now in a kind of plastic wrapper
> that despite its faults and mud
> "floor" will never burn or fall
> down around the engine.

Yeah Aarne, but you now have a dandy new turntable that you can do 360's with to your heart's content. Even trade, don't you think?

TJ

Port Huron Museum
tjgaffney@phmuseum.org

Answering Randy's question about rebuilding, I'm told unofficially that the surviving portion of the roof will be removed and the entire structure rebuilt. Also, they are apparently able to remove the smaller pieces in the undamaged portion (eg, the "Tom Thumb" replica, "Lafayette", Imlay coaches, Nova scotia coach,"Atlantic", etc.) but that the larger pieces, both damaged and undamaged, will have to remain there throughout the rebuilding.

> No P.E. here either, but I do have one handy
> in the room.
> Two quick thoughts - one, is that unlike the
> Columbia, we have plenty of forensics to
> look at here, including destructive material
> analysis and calculated load. But, unlike
> steel, nobody can accurately forecast
> load/stresspoints on old wrought iron. Which
> is why iron bridges are so rare, by the way.
> But of more interest is the half of the roof
> that DIDN'T collapse, giving some credence
> to dead load as opposed to pure thermal
> stress contraction. I'm also marvelling at
> the wonderful stuff that didn't get crushed
> under the half that stood. I'm as curious
> about what kept the other half up, and if it
> dare be left there, no matter how historic
> the fabric. So the solution can't be just to
> repair the half that fell.


herbhar@yahoo.com

I'm kind of currious about a couple of conflicting details that have cropped up. In an earlier post that was a part of one fo the first threads on the collapse it was stated that the roof collapsed fromt he outside edge inward, thus falling clear of the walls. In this thread it was stated that the most popular theory is that the connections between the roof joists and the central iron ring structure gave way. These two statements are pretty much mutualy exclusive of one another, so I'm currious if the statemtent about the mode of collapse, i.e. outside in, is accurate.

If that was indeed the correct mode of collaose, (and that could be determined from the debris patterns alone. essnetially all the big stuff is towards the middle, nothing but little stuff directly at the outside edges, little to no damage to the lower protions of the walls themselves, which at elast superficialy seems to be the case fromt he photographs,) then the initial failure has to have caused the roof to seperate from the vertical members along the outer perimiter first, while it remained to some extent fixed to the inner hub. Thus the connections between the joists and the inner iron ring could not be the source of that kind of collapse, correct?

Presumably we'll gat a better idea of the collapse as the investigation progresses. As an added point, local scuttlebut is rarely an accurate source of structural analysis. I have acquaintances from Kansas City that to this day inisist it was a pocket tornado that caused the collapse of the Kemper Arena roof and dancers in step that caused the failure of the Hyatt skywalks. Both were the fault of design flaws, and in the Hyatt a further design modificatin, exacerbated by a lack of redundancy, and both in actual fact collapsed under loads far below the local code requirements. I have outlines of both collapses along with some of the mathematical details. There's a wonderfull book by a structural engineer named Mario Salvitori called "Why Buildings Fall Down" appropriately enough that examines a number of interesting failures in laymen's terms.

Sincerely,
David Ackerman

david_ackerman@yahoo.com