Plate Girder
Plate Girder
(OP)
No question here. Just wanted to pass along a photo that I took on the highway. I think I counted 120+ bolt holes on the near end.
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: Plate Girder
RE: Plate Girder
i have no building/bridge experience but i have not seen a beam with that much bolts
RE: Plate Girder
This a "plate girder", made up of individual plates welded together....I kid.
I have had occassion to work on girders bigger than this in the power industry and some this big in steel mills. Not all too uncommon at all.
"Top Steel" boiler support girders can get huge.
RE: Plate Girder
RE: Plate Girder
Looks like West Virginia/ Virginia/ North Carolina country.
RE: Plate Girder
I wonder what it frames into considering the flanges are clipped.
Anthony Deramo
American Bridge Company
RE: Plate Girder
Most likely A bridge girder wouldn't need bolts like that on the end. It would just have a stiffener and be bottom flange bearing.
Even if it is a framing member in an industrial setting or a transfer girder in a building, I can't imagine framing that into the side of a column. Imagine the moment induced into the column.
Maybe it is a bridge girder and all those bolts are for a splice plate.
RE: Plate Girder
I would have said that it was a bridge girder, over an intermediate support with sliding bearing (hence the 3 heavy vertical stiffeners, to distribute the load as the bearing slides).
The clipped flanges are not unusual, I have seen that detail several times. Bolted connections are good places to change the flange sections, and flange transitions usually have tapered corners.
The unsual part (for me) is that I do not see any shear studs (connectors) on the top flange, and that the girder looks fully painted and the bolted splice area does not seem to be masked. Usually those are friction connections and they require a special primer to achieve the required friction coeficient.
RE: Plate Girder
Anthony Deramo
American Bridge Company
RE: Plate Girder
it looks like shear connection to me not moment connection..
RE: Plate Girder
If it is a bridge girder, shop attached studs wouldn't be used, for safety reasons. It can get a bit precarious assembling a large girder.
RE: Plate Girder
I bet it's a girder for a railroad bridge. The stiffeners are at a support. The bolt hoels at the end are for a splice. It's part of a continuous system. The intermediate stiffeners, with holes in the bottom portion, are to receive beams. The railroad runs across the tops of these beams, hence no shear studs on the girder.
The flanges could be welded at the splice. (I can't tell if there are bolt holes in the flange or not.) If the next girder has a narrower flange, that would explain the clip on the flange that we're looking at, to make the transition from one width to another.
Bolt holes look too small? How big is a 1.25" diameter hole supposed to look on an 8' tall girder?
RE: Plate Girder
I assumed there were bolt holes on the flanges. On second inspection it is not so clear on the picture. If there are not, I am at a loss.
Bridgebuster, in my area of the woods, clipped flanges at flange area transitions are not unsual, also on ocasions placed at splice locations, and studs are always attached on the shop. I have handled fairly large girders (up to 8 feet) with studs. Interesting to hear a different approach.
The bolt holes are probably not that small, the scale of the girder makes them look small.
RE: Plate Girder
Coal silos can be enormous.
RE: Plate Girder
am still wondering though why that many bolts on the web..
i have done many (small) beam splice before, i didnt have to have that much bolts on the web..
RE: Plate Girder
Anthony Deramo
American Bridge Company
RE: Plate Girder
RE: Plate Girder
RE: Plate Girder
How stable is this girder traveling on the semi?
RE: Plate Girder
I don't think it's a splice because there is no prep for a full penetration weld at the end of the flanges, that would have been done in the shop.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Plate Girder
Many bridge girders that we design for medium span (200-300') economy will generally have two stiffeners on each side of the web plate at the intermediate support and end support. for the range of span mentioned you will get about 7-9' girder depth on the low end and 12' on the high end. 12' is about the maxium you can ship on a low boy and meet vertical clearances. My recollection is that is not a lowboy and so the girder is part of a 200' span +/- some feet. Moreover, fabricators are allowed to chamfer the ends of a gider at the splice. After all, from the pier, the girder will splice into some smaller cross-section.
As to the number of bolts, that's not often a shear/moment requirement but must comply with AASHTO which states that splices will have have bolts extending the near total depth of the web. AASHTO also gives bolt spacing requirements. So often the number of bolts satisfies the geometric requirements of AASHTO and that is checked by the designer to see how many columns of bolts there should be.
I hope this helps.
Bridge girders - Go big or don't go at all!!
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Plate Girder
even the 4 columns of bolts is AASHTO geometric requirement?
RE: Plate Girder
edit:
so both the number of bolts (rows and columns) arent shear related but often AASHTO geometric requirement?
thanks,
RE: Plate Girder
Here's a cross section through the type of bridge I'm envisioning this belonging to. Of course, I could be wrong, but this seems the likely scenario to me.
RE: Plate Girder
In the bygone days of ASD and LFD, the requirement was to design the splice for a percentage of the girder section with consideration for material properties. Thus even the smallest section of a large girder had an impressive splice arrangment.
That there are not splice plates on the end of this girder may indicate that plates are on the other piece that will recive the end of this girder. Steel shops will typically partially bolt the splice to one of the sections leaving just enough bolts holes open to pull in the next piece.
As an a example, I've seen smaller beams in buildings that the splice plate is only half or some fraction of the total web depth. And was likely deisgned to the loads. Under AASHTO guidelines you can not do that. You must have a full depth web plate.
Also, all bridge splices are designed as slip-critical and so friction resistance is the governing requirement. Bolts in bearing under LFD were checked as an ultimate condition.
It very well may be a transfer girder for a power plant or even something else, but it just looks like a typical bridge girder to me.
For structural steel to be at it's best when competing with a local prestress, precast fabricator, steel leaves all behind at the 250 to 300 range and upward. Steel is much ligher than concrete at those spans - though nowadays spliced prestressed girders are pushing longer spans, up to 300', they remain heavier requiring heavier foudations.
Either way I just like big girders!
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Plate Girder
Qshake, I like the big girders too. Perhaps because one of the first jobs I did when I got promoted to the drawing board were some big riveted plate girders to hold up the cat crackers on a new refinery. Somebody got hold of a picture from a beauty pageant and traced the girls so they were walking on my girder.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Plate Girder
So the idea posed by nutte has merit in that the two columns of bolts in the transverse connection plate likely support a cross girder.
It's just that most railroads and or light rails don't use continuity too much as the weight of the engines can put a span in uplift when continuity is used. Of course, with the right span ratios....
Anyway, impressive stuff.
paddingtongreen - I started in construction as a new graduate and worked on a large river crossing. First girders I ever seen were 10' tall. The flanges were 26" wide and felt like walking on a sidewalk, when compared to some of the smaller girders I've been around.
All good stuff.
Regards,
![[pipe] pipe](https://www.tipmaster.com/images/pipe.gif)
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Plate Girder
Flanges are clipped because some engineer-wannabe-architect thinks it looks better that way, or because they imagine the savings of a few pounds of steel makes enough of a difference to make up for the labor of cutting the corners off. In a bolted connection, there's no structural reason for the taper.
Hg
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RE: Plate Girder
I would have followed the truck a little further back and then, when ready to pass, I would floored the gas pedal!!!
You'd think a load that big would have had an escort. I wouldn't be hangin' out next to that thing admiring it wait for the next big gust of wind.
Vandede427:
I really wish you had followed this thing to the jobsite so we knew what the hell it was for!?!?!?!
RE: Plate Girder
I seriously doubt any architects, wannabe or not, were involved in this project enough to voice their concerns for clipped flange corners.
I don't remember if there was an escort or not. I may not have have gotten them in the picture since I was next to the truck and going over a hill.
RE: Plate Girder
Definitely a highway bridge, railroads avoid continuous girders especially this size.
Flanges are not clipped, they are tappered to meet a narrower flange in the positive moment region. The splice is a good location to change flange widths and thicknesses for economy of material.
RE: Plate Girder
By "wannabe architects" I was referring to structural engineers. Architects aren't the only people who get cute aesthetic ideas in their heads.
Actually, there's another reason other than aesthetics, which is "we've always done it this way". Why "this way" started would be aesthetics or carryover from welded connections, but there's no longer a reason for it.
Hg
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RE: Plate Girder
Regardless of profession, there is something to be said for pride and craftsmanship.
RE: Plate Girder
Hg
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RE: Plate Girder
Why not be a little bit of a renaissance man? Being creative in designs and being able to design the difficult is what makes Arch's happy and keeps them coming to you for their projects.
500 years ago, the masters where architects, engineers, philosophers, and artists all wrapped up in one person.
RE: Plate Girder
add a couple of outcroppings and returns to a box. you still have a box but now it has texture. It's amazing what you can get from architecture.
RE: Plate Girder
I saw a project once where they chamfered the corners of all the splice plates. Just an inch or two clipped off each corner. No structural purpose whatsoever, and I can guarantee you that at least 99.96% of the driving public was never going to notice the difference, and of the remaining 0.04%, who knows how many would have thought it looked better that way than with a rectangular splice plate.
Choosing a too-small bend radius in a girder dap because the designer's personal opinion is that it looks niftier that way is another example of suboptimal design in the name of questionable aesthetics.
I could go on all day.
Hg
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RE: Plate Girder
RE: Plate Girder
I think we all worked for that same architect. We did a temporary pedestrian bridge with amenities - roofing, siding, elevator - anyway, the grief I went through detailing some connections and girders because at some locations the architect didn't want to see exposed bolts and electrical conduits. Funny thing - he was working for us.
RE: Plate Girder
Hg
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RE: Plate Girder
Currently I am designing a column that starts as concrete changes to timber then fishes as steel. To top it off the column supports a steel/timber truss. I am yet to work out how I am going to spec the durability for the timber, as it is external.
sorry I wanted to whinge to someone.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Plate Girder
RE: Plate Girder
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Plate Girder
RE: Plate Girder
RE: Plate Girder
Zoom in real close, get the truck's license number, track down the driver, and see if he remembers delivering a plate girder 6 months ago.