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Plate Girder

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.

RE: Plate Girder

Wow! Thanks.

RE: Plate Girder

ok is there something wrong with the beam?
i have no building/bridge experience but i have not seen a beam with that much bolts  

RE: Plate Girder

Ok-
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

As big @$$ girder like that needs a lot of bolts.  

RE: Plate Girder

Where was that can I ask?
Looks like West Virginia/ Virginia/ North Carolina country.  

RE: Plate Girder

Doesn't look like a bridge girder with those stiffeners in the middle.  Unless maybe they are supporting it there?

I wonder what it frames into considering the flanges are clipped.

Anthony Deramo
American Bridge Company

RE: Plate Girder

(OP)
I took that picture on Interstate 20 just east of Birmingham, Alabama, just a mile from where I live.

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

It has some strange details for sure.

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

Those bolt holes seem awfully small.

Anthony Deramo
American Bridge Company

RE: Plate Girder

am i missing something?
it looks like shear connection to me not moment connection..

RE: Plate Girder

If it's a bridge girder, it could be a section of a   continuous girder - between contraflecture points. However, a clipped flange is unusual in bridge work, at least in the mid-Atlantic and northeast.

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

Nice picture.

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

Interesting!

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

It could be for a power plant.
Coal silos can be enormous.  

RE: Plate Girder

i guess nutte explains it very well..

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

With that many holes and that hole spacing I'm willing to bet those holes are for 3/4" bolts.

Anthony Deramo
American Bridge Company

RE: Plate Girder

I say 7/8" dia. A490's.  

RE: Plate Girder

i say 5/8" A325.. lol.. who cares

RE: Plate Girder

Just a stupid question:
How stable is this girder traveling on the semi?

RE: Plate Girder

The end connection looks as though it is going on a knife plate so the bolts are in single shear. I think the girder flanges are clipped to fit between the column flanges. It has some low connections to it's stiffeners, something that happens on boiler support beams and girders, but the flanges don't look thick enough, unless it's a small boiler. As ToadJones said, they get very big, I worked on one that was 16' deep and had 56" wide flanges, 6" thick in the center. Toad is right about the bunkers too, sometimes they support 100' of coal.

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

It certainly looks like a bridge girder and I agree that its' part of the continuous line of girders.  Most likely that pieces is over the pier.  

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,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
 

RE: Plate Girder

qshake, question..
even the 4 columns of bolts is AASHTO geometric requirement?

RE: Plate Girder

qshake,

edit:

so both the number of bolts (rows and columns) arent shear related but often AASHTO geometric requirement?

thanks,

RE: Plate Girder

Paddingtongreen, the other girder framing into the splice could have the weld prep.  Also, the web connection is likely two plates, putting the bolts in double shear.  I doubt this is going into a column.

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

The four columns are definitely shear/moment related requirements, what's geometrically required is top to bottom bolts spaced at X" apart.  So the designer needs to figure out how many columns of top to bottom bolts he/she needs.

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,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
 

RE: Plate Girder

nutte, thanks, I did a lot of different things during my working life, but bridge design wasn't one of them. If it is a bridge girder, it must be the center section, it looks symmetrical.

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

I would not think that nutte is too far off.  Upon further review of the stiffeners/connection plates on web, there doesn't appear to be any top bolt holes for a full depth cross-frame or diaphragm from one girder to another.  

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,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
 

RE: Plate Girder

Looks like a normal bridge girder to me.  If anything, that's a pretty modest number of bolts.

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

Indeed you must love the inordinate amount of speculation that a group of engineers can make based on a photograph!!!!

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

(OP)
There's a steel fabricator down the road that does big boy work for jobs acros the country. My boss knows a guy there. I'll see if I can track it down and solve this mystery. My guess is that it came from there.

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

My 2 haypennies,
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

But there is no reason other than aesthetics for the flange to be tapered at a bolted connection.  It's not like a welded connection.  Just bolt the wide one to the narrow one; if you leave the corners on they're not doing anything.

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

Eng-Tips policies:  FAQ731-376: Eng-Tips.com Forum Policies

RE: Plate Girder

In my life, I have NEVER met a Structural Engineer that wanted to be an architect. Not once.
Regardless of profession, there is something to be said for pride and craftsmanship.  

RE: Plate Girder

I've met several.  And several more who, although they aren't specificially wannabe architects, engage in the same emphasis of aesthetics at the expense of function.

Hg

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RE: Plate Girder

(OP)
Don't knock aesthetics.  Wanting to only build rectangular boxes is what give SE's a bad rap.

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

My degree is architectural engineering. I can appreciate what an architect is trying to achieve. He(the architect) just usually doesn't see the innate difficulties in achieving his dream.
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 like aesthetics as much as the next person, but sometimes the aesthetic gain isn't worth the extra labor cost, or the degradation of the material, etc.

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

I argued with an architect one time about the underside of an awning at a grocery store. What he wanted cost 3x what was needed. He won the argument. I'd have to say the owner lost.

RE: Plate Girder

"I argued with an architect one time about the underside of an awning at a grocery store."

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

Continuing the thread drift...I dealt with an architect who didn't care about huge ugly weld seams all over the primary architectural element but freaked out about what kind of bolts could be seen from underneath the structure.  I love good architecture when I see it, but dang, I don't always get their mentality.

Hg

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RE: Plate Girder

I all for drifting,
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

Does the architect want that column painted?

RE: Plate Girder

of course not, they want the natural timber look :)

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

RE: Plate Girder

(OP)
is there anyway to delete this thread. it's gone on long enough, lol.

RE: Plate Girder

You can red flag it, but not until we get an answer on where that girder was going.

RE: Plate Girder

(OP)
I tried to track it down, but it didn't come from the fabricator I had guessed.

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.

 

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