Wooden Bridge Question

[Diggin It]

This sounds more like a high school homework question.

 

[Jw5875]

Well after several years of bridge washouts, finally bit the
big one and called in the pro's for the abutments, the rest I
finished myself.
A fellow TBN'r was gracious enough to give me an
APPROXIMATE capacity for my bridge after seeing my
beams etc. No I won't the numbers.
Any how, age 72 and less concern for washouts now.
If this one goes, going to buy a Duck Boat!!!!!!
Built railing from well pipe.

JW5875

 

[airbiscuit]

Now we're talkin.

 

[kenmbz]

That looks really sturdy jw

 

[fried1765]

Well after several years of bridge washouts, finally bit the
big one and called in the pro's for the abutments, the rest I
finished myself.
A fellow TBN'r was gracious enough to give me an
APPROXIMATE capacity for my bridge after seeing my
beams etc. No I won't the numbers.
Any how, age 72 and less concern for washouts now.
If this one goes, going to buy a Duck Boat!!!!!!
Built railing from well pipe.

JW5875

It does look sturdy, but I would be very concerned about washout/erosion over time, under those big blocks, unless there is actually a deep concrete footing under the blocks, or another row of buried blocks, beneath those that are visible.

 

[IH3444]

Nice job, keep an eye on it for scouring. When you neck water down during flood stage the force of the water can cause scouring under your concrete abutments. Also the water flowing lower during flood stage moves faster than the surface water due to it being under pressure from the top water. It looks to be flowing smooth and nice, but the real work is going on under the surface. The deep the water, the more force it has to remove material. You are channeling the water into a narrower configuration, making it a more powerful force down below.

Chapter 2 - Abutment Forms and Scour | Countermeasures to Protect Bridge Abutments from Scour | The National Academies Press

https://mtri.org/mdot_scour_workshop/13_Swartz_ScourCountermeasures_2017.pdf

 

[deezler]

^ I too would be nervous about scouring under those big concrete blocks. From the pics it looks like the span of the bridge should be about 8-10' wider....

If you choke off the creek into a narrow bridge crossing, the next flood is going to be exerting tremendous pressure on those blocks and pulling material out from beneath and around them. Hope I am wrong and it holds up forever, but I'd be mentally prepared to do that whole job again someday.

 

[workinonit]

It's obvious to me that I don't know crap about building a bridge. It sure looks good for the long haul to me. What size I beams did you use for the weight baring load? And how much weight do you calculate it will hold? I need to build one but just to cross a ditch. I hate using tile for a crossing. All of mine need to be replaced now. They are full of mud or collapsed.

 

[fried1765]

It's obvious to me that I don't know crap about building a bridge. It sure looks good for the long haul to me. What size I beams did you use for the weight baring load? And how much weight do you calculate it will hold? I need to build one but just to cross a ditch. I hate using tile for a crossing. All of mine need to be replaced now. They are full of mud or collapsed.

My Civil Engineering training, with reference to the bridge in question, leads me to believe that your first sentence may be essentially correct.

 

[workinonit]

It is or I wouldn't have stated it. But thanks for confirming. It's pretty much why I don't build bridges and chose the EE route to repair and commission generator voltage regulators in order to keep your lights burning. The abutments aside I was really more interested in the actual bridge span structure. I assume since you guys didn't flame his butt over that it must be fairly sound. Thus my questions about the I beams.