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.
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
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
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.
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
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
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.
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
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
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.
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!?!?!?!
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.
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.
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.
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.
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.
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.
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.
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 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.
"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.
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