# Building big bridges



## drew p (Jan 20, 2012)

Thought I would share photos of the 2 35' bridges we built on a new multi-use trail in Santa Cruz City open space, the Emma McCrary Trail in Pogonip. Mostly iphone photos, need to get some good ones of the completed bridges.

Excavation begins on abutments.









Installing forms.









Concrete goes in. About 95 80lb bags per bridge. All hauled in by wheelbarrow about 500' to one of the bridges, about a half mile for the other (used a muck truck, still really hard work).

















Beams get delivered. Had to move them to a different truck as they wouldn't fit under a railroad trestle on the way into the park.









Beams are treated 6x18 glue lams. 35' long, 976lbs. About $13,000 for 8 of them.









Beams were treated with waterproofing on top and ends. Moved in on cricket carts.









This one was a 450' trip straight down the hill. Used a porta-wrap to lower it slowly and safely.









Our arborist volunteer set up rigging for moving the beams across the creek.

























Bridge #2

















Used a high lift jack to lift the beams up to drill the bolt holes.









Time to move the decking in. 5' rough cut 3x8 redwood fresh from the mill. VERY heavy. Went in the same way as the beams.









Decking on.

















Railing posts in.









Railing taking shape. Design matches railing on historic building in the park (Grandpa's house in the Lost Boys movie!).









The final cut!









All done!









It was a huge undertaking for our club's first trail build, but with able and willing volunteers and generous donors we made it happen!

Mountain Bikers of Santa Cruz (MBOSC) | Mountain bike advocacy, events and fun based in Santa Cruz, California


----------



## slocaus (Jul 21, 2005)

Nice work Drew. You have rallied the volunteers up there and are doing some nice new trails.


----------



## singlesprocket (Jun 9, 2004)

that's one big bridge, we need to but in two big bridges on a new section of trail we are laying out. though the span is beyond what we can handle since it crosses a small river. though it will still be interesting to document the builders.


----------



## LyNx (Oct 26, 2004)

That's pretty cool, way load of work and $$$. Curious who designed/engineered that thing and when do you expect the tanks will need to cross it?


----------



## TFitz (Jun 21, 2008)

Beautiful!!!


----------



## drew p (Jan 20, 2012)

We started with some of the standard FS drawings, and a volunteer who is a civil engineer spec'd out the size for the beams and abutments. I think the design load was 80 lbs/sqft. Even with those big beams there was a little bounce in them before we put the railings on. After the railings which kind of work like a truss, they are rock solid even w/ 2 horses walking across at the same time. 

They would have been a bit easier if we could have made them a bit shorter, but Department of Fish and Game required a 6' setback from the top of the bank. I guess we don't need to worry about them falling in anytime soon now.


----------



## Wildfire (Feb 4, 2004)

That is beautiful, it looks bomber. I don't think it's at all overkill, 35 feet is a long span for a wood-stringer bridge that has to withstand possibly three or more horses on it at the same time. And withstand winter snow loading (not sure what your climate is there). Good job to all who helped, very impressive.


----------



## 2bfluid (Aug 17, 2008)

Great job to all who were involved.
Way to knock it out. Looks like they will last for generations. What no heli drop, prefab, cookie cutter bridges? JK Who led the charge on this project?


----------



## zachi (Jul 25, 2006)

Very nice work Drew. I really like the railing detail. It really brings character to the bridge.
zachi


----------



## jzskoorb (Jul 11, 2011)

Great work Drew! Love the craftsmanship and can't wait to see and ride them in person.


----------



## radair (Dec 19, 2002)

Great work, mate! Getting the stringers across the span is often times the crux, other than getting materials to the site. I really like the way you incorporated backwalls into the abutments also.

Pedestrian bridge live loads are generally 85 psf, which is why stringers on properly designed bridges are so massive. Deflection, not strength, is what typically controls in design.

Well done!


----------



## Berkeley Mike (Jan 13, 2004)

Very nice. Good details in the rails, posts and such.


----------

