Bridge design and engineering, how?

   / Bridge design and engineering, how?
  • Thread Starter
#11  
</font><font color="blue" class="small">( How did you figure the 4' culvert and why would you need one if you are building a bridge?

The reason I ask is because I have a seasonal creek, also, that I needed to across. The contractor that needed to cross it had me send in a check with his intended use to the PA something or rather and they sent back the plans on how it needed constructed. We were going to fill it in with gravel to drive across and even though the culvert pipe upstream is only 2' diameter, I needed a 3' diameter pipe plus all kinds of landscaping to prevent bank errosion.
After my project was done I had him rip it back out. It was only in half-a**ed anyway and the culvert was smaller than what the state told him to use. I can ford it with no problem and prefer the look of the creek.

I don't understand why you would need the culvert if you are building a true bridge and not filling it in like we did. )</font>

The culvert would be an alternate to using a bridge. I would not use a pipe. I'd use a half culvert inverted and fill in to the sides and then rock face the outside edges. This would give the appearance of an arched rock bridge. This also keeps the stream bed intact.

My property is basically two slopes leading to the stream, which divides the property roughly in half. The slopes to the stream bed vary from 4:1 to 2:1. This (culvert) would work in only one of the two spots I intend to cross the stream. In this spot the two slopes down to the stream are near a 2:1 slope and the stream bed is only 1.5' wide, in addition the downhill run of the stream is about 4:1 at this point. A 4' span (at base) inverted culvert would more than contain the existing stream bed at its maximum flow.

The soil around here is not quite decomposed granite. Not much stream bed erosion over time. The soil supports steep slopes and has a high absorption rate when it rains. Not a lot of natural run-off from the soil. The "stream" flow source is the street drain up hill from me. It does run year around though because my neighbors overwater their lawns.
 
   / Bridge design and engineering, how?
  • Thread Starter
#12  
</font><font color="blue" class="small">( Dave - If you will do a search for bridge, you will find several threads on bridge building. Don't remember any plans, but there have been a number of pictures of different bridges people have built, both with large culverts and using steel I beams. Also at least one using salvaged flat bed trailers. I am planning a bridge also so I have watched these posts with interest. Search all forums back as far as at least a year as they have been in different forums at different times. )</font>

I did do a search here and while I didn't look at all the replies, I did find several nice projects. I was looking for specifics on how to really know the load capacity of what I build. Not to just take my usual over do it approach.
 
   / Bridge design and engineering, how? #13  
Some of you might remember a thread about a bridge I want to build across my creek. I even had very generous offers of help, and the expert services of one of our most talented Texan artisans. Hopefully this will happen one of these days. It sorta got squeezed out of my budget due to the vacancy of my only rent property. Been empty a couple of months, but hope to get it rented out this weekend......

This is a very interesting subject, as bridges can really be beautiful as well as functional.
 
   / Bridge design and engineering, how? #14  
If the bridge span is only 10-15 feet, I suggest that a prestressed concrete slab be considered. You can even drive on the deck with your vehicle. I cannot remember the web address but I'm sure there are many other websites. They even had a chart on span, stress, load, etc.

If access is no problem, they will even bring out the slab and place it on supports. Because they have done all the load calculations, pulling permit will not be a problem. I once compared wooden bridge to prestressed concrete slab and found the latter cheaper.
 
   / Bridge design and engineering, how? #15  
</font><font color="blue" class="small">( specifics on how to really know the load capacity of what I build. Not to just take my usual over do it approach. )</font>

Like someone else mentioned.. if you use prestress, or a culvert box section.. the manufacturer will provide loading specs.. spans.. etc. You may have to come up with some sidewall stuff.. but that is no biggy.

Like I said.. we've put in large box culvert sections as bridges in putnam county florida.. this is for car and light truck traffic... it is very doable.. though not sure about your budget... box culvert can get pricey... prestress may be way cheaper.. then all you need is pylon supports.. large lentils and friction piles come to mind..

Soundguy
 
   / Bridge design and engineering, how? #16  
</font><font color="blue" class="small">( This would give the appearance of an arched rock bridge. This also keeps the stream bed intact.
)</font>

That would look nice, Dave. The engineers that designed mine had the 3' pipe buried half deep, which kind of gives the same effect since you can't see the stream bed at this point anyway.
 
   / Bridge design and engineering, how? #17  
Does anybody have a copy or know where I can get a copy of Army FM 5-34? --Not having much luck.
 
   / Bridge design and engineering, how? #19  
Larry,

Yeah, I tried somthing like this on another part of the Army site....turns out to be blocked by a log-in. I'm finding this all over the the .mil and .gov sites (Army Corp Eng. as well).

Apparently we can thank 9/11 on this change. I've also heard the Bush administration is labeling everything they can "secret" regardless of its actually use....thousands upon thousands of documents are now classified. Oh well. Maybe somebody has a copy and can email it or has it posted on the web.
 
   / Bridge design and engineering, how? #20  
This one Jim? Engineer Field Data - FM5-34.
PM me and I can email it, though it's 10MB zipped.
 

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