Building a bridge

[sld]

I think transit is way off base.

Does he realize the how much load it would take to break even one 6x6, let alone 4 of them with only 7 feet unsupported?

Now, it could of been stronger if you would've triangulated the middle of the unsupported section back to the base of the vertical posts on either side but it would be totally unnecessary for what you are doing.

Great job! Getting it done and overthinking it and never getting it done are two very different things.

 

[SpringHollow]

Actually, it would be fairly easy to calculate the load limits on your beams if you know the span for each beam. For shorter distances, beams are amazingly strong. If i had the formulas in front of me, i would calculate it for you. But do not want to wake up my wife getting my Timberframing references. There are tables readily available for uniform loads for wood, and possibly for point loads.

Ken

 

[buggyman1]

I think transit is way off base.

Does he realize the how much load it would take to break even one 6x6, let alone 4 of them with only 7 feet unsupported?

Now, it could of been stronger if you would've triangulated the middle of the unsupported section back to the base of the vertical posts on either side but it would be totally unnecessary for what you are doing.

Great job! Getting it done and overthinking it and never getting it done are two very different things.

Thanks,,, What blows me away, with a seven foot span max, a train wouldn't break it...think about it..two 6x6's bolted together on both sides of the track...It must be me?

 

[buggyman1]

Actually, it would be fairly easy to calculate the load limits on your beams if you know the span for each beam. For shorter distances, beams are amazingly strong. If i had the formulas in front of me, i would calculate it for you. But do not want to wake up my wife getting my Timberframing references. There are tables readily available for uniform loads for wood, and possibly for point loads.

Ken

Thanks....
Please post them when you get a chance. I would really like to see them.

 

[cowboy357]

Thanks for the updated pics. Looks great to Me & Plenty strong , But I aint no engineer .

But the again Maybe You could get a job designing & Building bridges for the state of Kansas , because over 300 of the ones That the Engineers Designed & had Built by there specs have been condemned as not safe .

Looking Forward to You next project . Bob

 

[SpringHollow]

I can by no means guarantee these calculations especially since i can not access my books at this time so I am using some values for modulus etc off of the web and using a spreadsheet set up for a specific situation. I would be much more comfortable using the tables and equations i always use. Having said that, I came up with the following:

2000 lb point load in the middle of a span of a Southern Yellow Pine 6x6 (used 5.25" x 5.25"):
span (ft) deflection (in)
5' 0.14"
6' 0.25"
7' 0.4"
8' 0.6"

No safety factors etc.for being wet wood, etc.

Realize a tractor bouncing up and down from a backhoe on the back etc can significantly increase the amount of instantaneous force on a member.

Multiple members increases the safety especially if the decking is strong enough to help distribute the load to multiple members.

Ken

 

[Transit]

I think transit is way off base.

Does he realize the how much load it would take to break even one 6x6, let alone 4 of them with only 7 feet unsupported?

Now, it could of been stronger if you would've triangulated the middle of the unsupported section back to the base of the vertical posts on either side but it would be totally unnecessary for what you are doing.

Great job! Getting it done and overthinking it and never getting it done are two very different things.

Maybe so. Better to be off base than under a tractor. Shooting from the hip is not the way to build a bridge.

 

[buggyman1]

Maybe so. Better to be off base than under a tractor. Shooting from the hip is not the way to build a bridge.

Thanks Transit for kinda being my "devil's advocate". I welcome everyone's input, it makes me try harder. If you check-out my other posts, you'll prob. see, I really don't leave much to chance. This bridge isn't going to be crossed by anyone on my tractor but me. It's more of a landscaping bridge to be used as such...UTV's, zero turn mowers, golfcarts, etc. I needed it to feel safe to me for the occasional crossing of my tractor, and I do. The bridge is done, i'm happy with it...I would really like your input on my next one, it's going to be a 32 foot span, and a lot higher. I regret not taking pics from the start of my last one, I plan to this time...Thanks again for you're input.

 

[Transit]

Thanks Transit for kinda being my "devil's advocate". I welcome everyone's input, it makes me try harder. If you check-out my other posts, you'll prob. see, I really don't leave much to chance. This bridge isn't going to be crossed by anyone on my tractor but me. It's more of a landscaping bridge to be used as such...UTV's, zero turn mowers, golfcarts, etc. I needed it to feel safe to me for the occasional crossing of my tractor, and I do. The bridge is done, i'm happy with it...I would really like your input on my next one, it's going to be a 32 foot span, and a lot higher. I regret not taking pics from the start of my last one, I plan to this time...Thanks again for you're input.

I'm not trying to put anyone down. I remember a question on my Civil Engineering final. A very simple question about hanging a door of a given weight and dimensions, the question was to find the size and number of screws to set the hinges that would support twice the weight of the door. Simple, no? I'm an EE, haven't been civil in years. There are cook books on building a house, none that I know of for bridges. Just drill a hole for a bolt in a beam in the wrong place and down goes the bridge. There are things outside my rice bowl that I will not take on even with the know how. Be careful.

BTW, B+

That 32 foot bridge. Just a though, if there is a Engineering college close by, maybe you could make a deal with the engineering department as a class project to have the students design a bridge for you with the guidance of the instructors?

 

[BlacknTan]

I think the bridge looks great!

I'd cross it on a tractor withouit giving it a second thought... It seems overbuilt enough to be more than just safe..but, I'm no civil engineer...

Your dog looks like he trusts your handiwork without question.. LOL

Enjoy it, it turned out great!