Beams and bolts and washers oh my!
April 16, 2009 9:02 PM Subscribe
Is this an acceptable construction technique in ironwork?
The Chicago Transit Authority is finishing up a project to rebuild stations along one of its lines. A few days ago I was waiting for a train and my eyes wandered to the ironwork for the platform. What I saw was interesting and then a wee bit scary. I've been trying to figure out how to explain what I saw but a picture I took can do a much better job that I can.
Bolts and washers.
To my know nothing mind whenever beams go together the bolts go through holes, the edges aren't held down with washers. Most of the cross beams do have holes for bolts like the beam at the top of the picture. Is this technique something unusual? If not why did they do things this way?
The Chicago Transit Authority is finishing up a project to rebuild stations along one of its lines. A few days ago I was waiting for a train and my eyes wandered to the ironwork for the platform. What I saw was interesting and then a wee bit scary. I've been trying to figure out how to explain what I saw but a picture I took can do a much better job that I can.
Bolts and washers.
To my know nothing mind whenever beams go together the bolts go through holes, the edges aren't held down with washers. Most of the cross beams do have holes for bolts like the beam at the top of the picture. Is this technique something unusual? If not why did they do things this way?
What direction is the camera looking? Is that a wall or the floor?
posted by Chocolate Pickle at 9:16 PM on April 16, 2009
posted by Chocolate Pickle at 9:16 PM on April 16, 2009
Just the part shown in your photo doesn't look too good, but there may be a connection beneath the wooden boards that makes up for it. It may have been a dimensional mistake, but it's not like they couldn't drill another hole through the steel somewhere else and attach it more securely.
It looks like the end of the beam is just about right where the centerline for the bolt hole should be, which makes me think that somebody overlaid dimensions on the drawing or misinterpreted them in the shop.
posted by LionIndex at 9:22 PM on April 16, 2009
It looks like the end of the beam is just about right where the centerline for the bolt hole should be, which makes me think that somebody overlaid dimensions on the drawing or misinterpreted them in the shop.
posted by LionIndex at 9:22 PM on April 16, 2009
That is an accident waiting for a victim.
posted by JohnnyGunn at 9:23 PM on April 16, 2009 [1 favorite]
posted by JohnnyGunn at 9:23 PM on April 16, 2009 [1 favorite]
Yes, this is a major error, there is no way to rationalize this as proper technique. In fact I think you have a moral duty to contact the Chicago Transit Authority and report it.
posted by Tube at 9:27 PM on April 16, 2009
posted by Tube at 9:27 PM on April 16, 2009
Well, the beam in the foreground is the same. So I guess that's a good thing :)
Actually, the dark seam that runs down the center of the girder that the (apparently un-bolted) beams bear on looks to me like the joint between a pair of channels that are paired back-to-back (to form an "I" profile). My guess is that the beams are actually bolted through the top flange of the inner channel, and the bolts in the top flange of the outer channel that are visible in this photo are there for some other reason.
Can you see this from the side at all, instead of just from above?
posted by misterbrandt at 9:32 PM on April 16, 2009
Actually, the dark seam that runs down the center of the girder that the (apparently un-bolted) beams bear on looks to me like the joint between a pair of channels that are paired back-to-back (to form an "I" profile). My guess is that the beams are actually bolted through the top flange of the inner channel, and the bolts in the top flange of the outer channel that are visible in this photo are there for some other reason.
Can you see this from the side at all, instead of just from above?
posted by misterbrandt at 9:32 PM on April 16, 2009
Just the part shown in your photo doesn't look too good, but there may be a connection beneath the wooden boards that makes up for it.
I agree.
It may have been a dimensional mistake, but it's not like they couldn't drill another hole through the steel somewhere else and attach it more securely.
The holes on the flange which is vertical in the photograph look to be positioned correctly. At the very least, the I beams should have tabs welded on that would correctly match the holes in the flange.
posted by Tube at 9:38 PM on April 16, 2009
I agree.
It may have been a dimensional mistake, but it's not like they couldn't drill another hole through the steel somewhere else and attach it more securely.
The holes on the flange which is vertical in the photograph look to be positioned correctly. At the very least, the I beams should have tabs welded on that would correctly match the holes in the flange.
posted by Tube at 9:38 PM on April 16, 2009
The holes on the flange which is vertical in the photograph look to be positioned correctly.
That's the thing - the holes on the upper (in the photo) beam are very precisely located - equidistant from the end and sides of the beam, which makes it weird that they're now empty. Then, the lower beam doesn't appear to have any holes at all, and I don't know how to explain that, because from what I can tell, they should be the same.
posted by LionIndex at 9:59 PM on April 16, 2009
That's the thing - the holes on the upper (in the photo) beam are very precisely located - equidistant from the end and sides of the beam, which makes it weird that they're now empty. Then, the lower beam doesn't appear to have any holes at all, and I don't know how to explain that, because from what I can tell, they should be the same.
posted by LionIndex at 9:59 PM on April 16, 2009
Response by poster: The picture is looking down and to the left (north) side of the platform. The wood section is the station platform. The beams under the washers are crossbeams that support the platform. Here's another picture looking to the right (south).
Another view.
Wow, I didn't even realize that in the second picture the beams aren't even under washers. I should be able to take pictures of the underside of the station tomorrow. If I'm able to get those I'll post the links here. I'll contact the CTA as soon as I can.
posted by @homer at 10:37 PM on April 16, 2009
Another view.
Wow, I didn't even realize that in the second picture the beams aren't even under washers. I should be able to take pictures of the underside of the station tomorrow. If I'm able to get those I'll post the links here. I'll contact the CTA as soon as I can.
posted by @homer at 10:37 PM on April 16, 2009
If the beam is fastened in other locations, this may not be structurally significant and it may still be perfectly safe. But by all means inquire, as there are a lot of ifs and maybes there.
posted by cardboard at 3:01 AM on April 17, 2009
posted by cardboard at 3:01 AM on April 17, 2009
If you don't get a respectable answer from the CTA, e-mail those photos to the "questions" type address at either newspaper or some TV station. At least that'd get some more eyes on it.
posted by rokusan at 3:33 AM on April 17, 2009
posted by rokusan at 3:33 AM on April 17, 2009
Tough call. It's almost impossible to look at a single connection and determine whether it's appropriate or not. That looks pretty half assed, but the original detail may have called for no connection and someone decided to add a little something extra.
That said, it looks like the beams should've been bolted through the flange of the beam they're resting on top of. The beams appear to be the wrong length, so the connection isn't possible since it'd fall right in the center of the two C-channels. Usually there'd be some kind of connection plate, but it's not strictly necessary unless the structural engineer calls for it.
It looks like it's holding up a pedestrian walkway, so you should definitely alert someone to it. It's likely that it's fine, but no one here would be able to tell you otherwise if it isn't, based on the limited information we've seen.
posted by electroboy at 6:34 AM on April 17, 2009
That said, it looks like the beams should've been bolted through the flange of the beam they're resting on top of. The beams appear to be the wrong length, so the connection isn't possible since it'd fall right in the center of the two C-channels. Usually there'd be some kind of connection plate, but it's not strictly necessary unless the structural engineer calls for it.
It looks like it's holding up a pedestrian walkway, so you should definitely alert someone to it. It's likely that it's fine, but no one here would be able to tell you otherwise if it isn't, based on the limited information we've seen.
posted by electroboy at 6:34 AM on April 17, 2009
Response by poster: The other picture shows beams on the same side.
posted by @homer at 7:09 AM on April 17, 2009
posted by @homer at 7:09 AM on April 17, 2009
in the second photo, there's no visible reason to have bolts installed at all, if they're not holding down those cross-members. Is there any structure below the girder, perhaps, and they bolt/washer assembly shown in the first photo is only coincidentally appearing to "hold down" the cross-members? That's the only non-sketchy reason I can think of. You really need to determine if there is anything else securing those cross-members to the girder.
posted by Chris4d at 7:58 AM on April 17, 2009
posted by Chris4d at 7:58 AM on April 17, 2009
Response by poster: I took a trip on the Brown line to the new Stations at Damen and Irving Park. I also looked at the other side (southbound) side of the Montrose platform. Damen and Irving Park have all the beams bolted. The southbound side of Montrose does as well. Here are the pictures I was able to get.
Southbound platform at Damen. This picture is looking down and to the right (west.)
Southbound platform at Montrose. This is looking down and to the right (north.)
Northbound platform at Montrose. The picture in the original question. This looks down and to the right (south.)
Close view of the platform beams for the northbound platform at Irving Park.
Typical view of the platform support beam connections on the rail side of the platform. As far as I can see that's the only other connection for the platform supports. I emailed the CTA and got a canned response. I also emailed a local TV station and got a canned response.
posted by @homer at 2:54 PM on April 17, 2009
Southbound platform at Damen. This picture is looking down and to the right (west.)
Southbound platform at Montrose. This is looking down and to the right (north.)
Northbound platform at Montrose. The picture in the original question. This looks down and to the right (south.)
Close view of the platform beams for the northbound platform at Irving Park.
Typical view of the platform support beam connections on the rail side of the platform. As far as I can see that's the only other connection for the platform supports. I emailed the CTA and got a canned response. I also emailed a local TV station and got a canned response.
posted by @homer at 2:54 PM on April 17, 2009
But @homer, in all those photos, there are a pair of bolts securing the crossing beams to the inner C-channel as well. 4 bolts per beam-end is serious overkill (as all the bolts need to do is prevent displacement and overturning of the beams), so maybe somebody decided to save some steel and labor by leaving some beams short?
posted by misterbrandt at 6:40 PM on April 17, 2009
posted by misterbrandt at 6:40 PM on April 17, 2009
Response by poster: It's entirely possible it was an attempt at saving labor or materials. It seems like a strange way to do it though.
posted by @homer at 9:21 PM on April 17, 2009
posted by @homer at 9:21 PM on April 17, 2009
It seems like a strange way to do it though.
Agreed
posted by misterbrandt at 10:30 AM on April 18, 2009
Agreed
posted by misterbrandt at 10:30 AM on April 18, 2009
Jon Hilkevitch at the Chicago Tribune would likely take an interest in this.
posted by rigby51 at 4:23 PM on April 18, 2009
posted by rigby51 at 4:23 PM on April 18, 2009
This thread is closed to new comments.
posted by pmbuko at 9:07 PM on April 16, 2009