Sizing bridge beams

[LD1]

Steel it is! I will check out the scrap yards to see what is available.
Next I will try to locate an area of the creek that is narrowest. Keeping my footers/concrete blocks 2' from the bank, I am going to end up with a 11' - 14' span.

Is there a good online calc for "point loads" of the different sizes of steel beams?

I downloaded a program called beamboy. It has a lot of beam specifications stores....and you can enter basic information like span, load, and select a beam. Then it will calculate stress and deflection for you.....

But you still have to have an understanding of just how much stress and deflection is acceptable.

You can also do it long hand with the stress and deflection formulas. But you have to find the specs of the beam.....specifically the moment of inertia.

But to my knowledge.....there is no simple chart that lists all the various beams and their max weight for a given span like there is for lumber and lvl's.

In your quest for shopping for a beam.....just know that all but the very lightest of the 5" and 6" steel I-beams will support a ton at midspan of 14'.

Obviously heavier beam means higher capacity....as well as shortening the span. 11' will hold alot more with a given beam than 14'

 

[5030]

But to my knowledge.....there is no simple chart that lists all the various beams and their max weight for a given span like there is for lumber and lvl's.

Yes, there is. Your local library will have a copy of the ASTM book listing not only web widths but static loading as it relates to length.

 

[Everhard]

7 Pages already! Nice! Well 2 more cents...
I had a CK20s (loaded rears with a hoe) now a CK2510 cab, loaded rears and yes the same hoe has been hanging on the back... (sometimes) so total weight is under 4000lbs. Being a cheap-ass I cut down 2 big trembling aspens (poplar - crappy wood...) chainsaw flat the top side, slapped a bunch of 2x8 pressure treat on top with a couple perpendicular rows of 2x8 pressure treat on top of those where the tractor travels over. Tractor parked on top I measured the flex before and after. Zero flex.
That lasted almost 10 years before one of the logs rotted enough that it started to give. Pulled up boards... 2 more trees... boards back down... here's to the next 10 years. lol. Maybe more? This time I wrapped it with some extra water/ice guard I happened to have laying around.

E.

 

[/pine]

There is no "finding my own proof".

Because it doesn't exist.

YOU are the one that believes plywood is stronger. I'm simply asking you to show proof.

Saying an I-joist is stronger than a dimensional board is indeed factual. Because the strength isn't because plywood is used for the web and you are changing the structural shape vs comparing apples to apples is size.

Furthermore, I gave you an example of achieving the same or greater strength WITHOUT plywood but via floor trusses.

And you have yet to cite anything I said that is inaccurate.....yet you make the claim in an attempt to discredit what I have said

What you have said and claimed is mostly supposition...with nothing to back it up...
I have merely pointed out that the strength of plywood etc...allows it to be used in place of solid lumber to make lighter , cheaper alternatives...figure it out already...geeze...!

And BTW... floor trusses are extremely heavy and depending on the span can require a machine to set them in place...an I joist can be set with even only one or two mechanics...!

 

[2manyrocks]

7 Pages already! Nice! Well 2 more cents...
I had a CK20s (loaded rears with a hoe) now a CK2510 cab, loaded rears and yes the same hoe has been hanging on the back... (sometimes) so total weight is under 4000lbs. Being a cheap-ass I cut down 2 big trembling aspens (poplar - crappy wood...) chainsaw flat the top side, slapped a bunch of 2x8 pressure treat on top with a couple perpendicular rows of 2x8 pressure treat on top of those where the tractor travels over. Tractor parked on top I measured the flex before and after. Zero flex.
That lasted almost 10 years before one of the logs rotted enough that it started to give. Pulled up boards... 2 more trees... boards back down... here's to the next 10 years. lol. Maybe more? This time I wrapped it with some extra water/ice guard I happened to have laying around.

Where did the rot set in? My guess is the log started to rot where moisture was trapped under the deck boards. But what was your experience?

 

[jonsstihl]

On my bridge, the one beam that failed had disintegrated enough that i couldn't really tell where it had failed but the other beam was still nice so I am leaning towards a bad spot in the wood.

I had to get wood out in the fall so I kept driving over it after it failed. Mine is more of a creek crossing that is dry during the summer but gets quite full when rains come. I will try and get pics before and after later.

If you do go steel make sure you think about how to keep the beams from twisting. don't rely on the decking to keep them parrallel and right side up. Someone posted a pic of a steel bridge farther up this thread with the beams laying on their sides. do not do that. I'm not sure if that pic was just while the bridge was being built but...

Mine was small enough that I welded it up in the garage and set it in place then put the decking on once it was placed.

I used galvanized beams my neighbour had a few used lengths that I got for 350$ CAD for four 11 foot beams. that was pre covid

 

[JamesHW]

I found this US Forest Service guide covering in detail the following bridge types (including CAD templates) very useful. No reason to reinvent the wheel.

SINGLE LOG STRINGER TRAIL BRIDGE
MULTIPLE LOG STRINGER TRAIL BRIDGE
SAWN TIMBER TRAIL BRIDGE
LONGITUDINAL NAIL - SAWN TIMBER TRAIL BRIDGE
GLULAM STRINGER TRAIL BRIDGE
LONGITUDINAL DECK PANEL GLULAM TRAIL BRIDGE
PREFABRICATED STEEL TRAIL BRIDGE
TIMBER SILL ON GEOCELL PAD - TRAIL BRIDGE SUBSTRUCTURES
TIMBER SILL ON TIMBER CRIBBING - TRAIL BRIDGE SUBSTRUCTURES
CONCRETE LEVELING PAD ON BEDROCK - TRAIL BRIDGE SUBSTRUCTURES

We have a small stream in a valley we want to span and originally I was thinking a bridge, but realized everywhere close by the spanning of streams was done with causeways and culverts due to the silty/sandy soil. There are three ways to solve the issue, create a ford, add a causeway and culvert or add a bridge.

A resource I've also found useful for planning this sort of project is the USGS National Map Viewer that allows you to overlay layers, adjust order and transparency to see pretty detailed Lidar images of your project. This shows the use of a measurement tool showing the area off a potential causeway overlaid on lidar layers, "hillside stretched" and contour lines which for our area are very accurate in our area, though the wetlands data seems offset from the lidar data, though accurate in the aggregate AFAICT, just annoyingly mis-aligned.

 

[LD1]

What you have said and claimed is mostly supposition...with nothing to back it up...
I have merely pointed out that the strength of plywood etc...allows it to be used in place of solid lumber to make lighter , cheaper alternatives...figure it out already...geeze...!

And BTW... floor trusses are extremely heavy and depending on the span can require a machine to set them in place...an I joist can be set with even only one or two mechanics...!

Getting exhausting. If I said 2+2=4 and you disagreed......I'm sure you would want the burdon of proof to lie on me as well.

Do your own research. I state facts. Well know facts to anyone in the trade. Sorry you disagree.

But I give up. You win. Plywood and OSB is stronger than dimensional lumber, and never fails. Use plywood for everything....even exterior bridge beams.

I got no skin in this game and could careless if anyone else's projects fail. I'll still sleep well tonight.

Now carry on.....I'm done with this thread. There is only so much effort I'm willing to put into trying to educate others. And I have surpassed that limit.

 

[/pine]

Getting exhausting. If I said 2+2=4 and you disagreed......I'm sure you would want the burdon of proof to lie on me as well.

Do your own research. I state facts. Well know facts to anyone in the trade. Sorry you disagree.

But I give up. You win. Plywood and OSB is stronger than dimensional lumber, and never fails. Use plywood for everything....even exterior bridge beams.

I got no skin in this game and could careless if anyone else's projects fail. I'll still sleep well tonight.

Now carry on.....I'm done with this thread. There is only so much effort I'm willing to put into trying to educate others. And I have surpassed that limit.

LoL...to educate someone...first you have to know more about what you're teaching than the person you're teaching...you obviously do not...and you really need a remedial reading comprehension class because you have done nothing but misquote me or totally misconstrue what I've posted...
go ahead and run off...your tail should be between your legs....LoL...!

 

[Everhard]

Where did the rot set in? My guess is the log started to rot where moisture was trapped under the deck boards. But what was your experience?

I think likely you're right although I didn't bother to look in detail, timing was crap and I was rushed to replace the beams. Note I did soak the flattened top of the first beams with a lot of preservative. Incidentally the beam that didn't rot was actually in very good condition, it wouldn't have failed any time soon.

E.

 

[Sawyer Rob]

Someone posted a pic of a steel bridge farther up this thread with the beams laying on their sides. do not do that. I'm not sure if that pic was just while the bridge was being built but...

You mean, don't do it IF you expect the bridge to carry heavy loads!

The bridge posted above with the beams lying down is only used as a walk, ATV or lawn mower bridge, it's not going to see a heavy tractor.

SR

 

[Slackdaddy]

I found this US Forest Service guide covering in detail the following bridge types (including CAD templates) very useful. No reason to reinvent the wheel.


We have a small stream in a valley we want to span and originally I was thinking a bridge, but realized everywhere close by the spanning of streams was done with causeways and culverts due to the silty/sandy soil. There are three ways to solve the issue, create a ford, add a causeway and culvert or add a bridge.

A resource I've also found useful for planning this sort of project is the USGS National Map Viewer that allows you to overlay layers, adjust order and transparency to see pretty detailed Lidar images of your project. This shows the use of a measurement tool showing the area off a potential causeway overlaid on lidar layers, "hillside stretched" and contour lines which for our area are very accurate in our area, though the wetlands data seems offset from the lidar data, though accurate in the aggregate AFAICT, just annoyingly mis-aligned.

View attachment 778979

The county, state (and probably the feds) would have a heart attack if I dropped a culvert in the stream and backfilled.
This creek is a tributary of the Patuxant river (part of the tidal Chesapeake Bay),, The creek on my property is not tidal, but about 1/2 mile down it is.

 

[2manyrocks]

I think he was just saying that design information was available from the Forest Service and that those topo maps were available.

I detest culverts because most of them I've seen are woefully undersized causing the water flow to either backup in a storm or cause stream water to overflow the banks into the highway. Or they aren't maintained, fill up with debris and backup the flow of water.

 

[jonsstihl]

about the bridge with the beams sideways. unless there is some specific dimensional reason to do that you really are loosing a lot of the beam capacity. the beams I used were 6" wide and 6" high so I had no difference. It obviously worked for you and with light traffic its fine. but why compromise the capacity of the bridge in that way when a simple 90 degree flip of the beam would give a huge increase in capacity.

some taller beams and larger spans would not even support themselves on their sides.

 

[KDubU]

Following as I have a similar project for this summer.

 

[Sawyer Rob]

about the bridge with the beams sideways. unless there is some specific dimensional reason to do that you really are loosing a lot of the beam capacity.

Yes there's a specific reason, that's why there's 3 instead of two beams.

SR

 

[LD1]

Yes there's a specific reason, that's why there's 3 instead of two beams.

SR

Got me curious as to the reason. Definitely arent as strong that way....but obviously strong enough for what you need them to do.

 

[jonsstihl]

i'm curious as well as to the reason. If it worked for you than that's great. Sometimes challenges come up and how we adapt to them within the constraints of the project make all the difference.

 

[beeforty]

A steel beam with the web vertically that is long can be curved sideways just like a long plank can be curved while not flexing downward any appreciable amount when in the vertical position. The top flange I believe is in compression and the bottom is in tension working to keep it straight with the webbing keeping them apart, just like in a floor joist. That short of a span on those beams it might not matter, but when they are placed vertically you have more support for your decking. Usually with steel beams you'll have a nailer board attached to the top flange for your decking to be secured to, not sure how he's planning to secure his deck boards.

 

[Slackdaddy]

Did some final measuring today.
Looks like the best spot the top of the bank width is about 12',, so adding 2' on each side to get away from the bank,, I will need 16' beams.
I'll be dropping by the scrap yard later this week.
With the 16' beams, my clear span would be about 14-15'
Now how to keep them from twisting.