As with most of my “operations”, there is generally a higher plan if you will. If you recall, the summer project was focused on “parkifying” the area around a stream in our back lot. There was actually another follow on effort to establish a means to get myself and ATV across the stream so I can enjoy the other 7 acres of my lot. Focusing on the brush cleanup around the stream allowed me to take a step back and find the best possible placement to construct a bridge. With the brush and thorns cleared out I could judge the flood lines and pick the highest banks. All of this prework put me in a good position to start the fall project of constructing the bridge.
From a requirements perspective, it needed to span the river without any permanent supports in the actual stream due to not wanting to deal with any DNR permits or restrictions. If you are curious, you may own the property, but they own the rights to the waterways and any flow changes or obstructions need to be cleared through them. Secondly, it needed to be wide enough and strong enough to support my ATV. That is my workhorse and I already have a few trails over there that I currently enjoy those few times of the year that are dry enough to drive through the stream bed. With these few requirements, I set about planning the design. The sticking point was what construction material to use. A few options included a semi-truck bed, steel construction beams, cables, concrete and lastly lumber. The first two options were ruled out after unsuccessfully trying to figure out how to get those materials down to the stream and the steel beams added some significant cash to the effort. The cable option would probably be the cheapest, but figured the ATV traversal would be a little hair raising. The concrete option looked intriguing. There would be plenty of water for mixing, but the inability to get a concrete truck down there would mean hauling a staggering number of concrete bags. With those options crossed off, I was left with the treated lumber option.
With that decision out of the way, the next task was to set the design. Fortunately, my oldest brother (Dan) is well versed in the engineering design field and spent a long time helping me figure out the best approach to spanning the stream. By far, the trickiest part was compensating for no mid-stream supports. This means the structure has to be able to support a hefty downward force and distribute that weight out to the bank supports. With arcs being a tad difficult construct out of lumber, we went with the next best geometric shape, the triangle. I will take a short cut here and simply state we made a LOT of design changes before we were done and actually still considering adding some additional support. Oh, and credit should also be given to the John’s Hopkins Online Bridge Designer website. Although this site does not give rotational forces, it does a very good job of showing how the downward forces will distribute over the triangle legs. Thanks to this program we actually decided to double the amount of triangles and actually removed the upward triangle legs at the post ends.
Next up.. the prep work – hit the jump to check out some pictures of project
It was clear from the beginning that the structure would require a pretty good foundation. Unable to get a mechanical auger down to the stream. Well, at least without spending over $500 so I instead invested in a 6′ steel chisel bar and dug out the manual post hole digger. Having mapped out 4 posts per side with the aid of a long string and a tape measure (imagine about 50 traversals through the stream to get those positions right), I went about digging 8 twelve+ inch holes up to 5′ deep. Every once in a while there would be a stubborn root or sandstone boulder that had to be removed with the chisel bar. Note, this particular workout far exceeded anything done in the P90X tapes and highly recommend it if you are looking for a quick weight loss program and do not mind being unable to close your fingers for week. Once dug, 4′ re-bar was pounded into the hole and 12″x4′ cardboard cylinder forms were dropped to hold the foundation. The opposite bank was actually lower near the stream so those holes were not as deep. If you recall, I ruled out the concrete bridge due to the amount of bags that needed to be hauled. This was confirmed after hauling 64 bags of concrete to fill the foundation forms in with. Checking this task off was a major accomplishment for me. To complete the foundation piece I also had to have 8 brackets created to hold the 6″x6″ posts. A local iron worker was able to create them for me with just a brief conversation over the phone. To his credit, he immediately caught on to my design, verified a few dimensions and cranked them out in about a week. With a quick paint coating, they were ready to be installed. Issue #432 raised its ugly head. I already owned a hammer drill and figured it could be used to drill the 32 holes in the foundation pillar to secure the brackets. Problem was it had this cord thingy dangling from it and couldn’t find a tree with the right plug in it. Sigh, it was time to call on a friend who lent me his generator. Clearly underestimating the weight of this beast, it just about resulted in a hernia to get it in the ATV cart and brought up the death fears again as I pulled it down the hill. After getting it down there, everything went off very smooth. The Bosch drill cut through the cement like butter and with the metal inserts and 1/2 x 5″ lags the brackets were in place. Although a little small, here is a picture that shows the a few of the footings.
You can also tell the elevation differences I was fighting will laying out the footing placement.
Now that the prep work was checked off, the lumber construction phase was initiated. Dan came over and helped me set the 8 6″x6″ posts used to anchor the bridge. We kept the inside posts at the full 10′ length to compensate for any design changes that may come up, but the outer posts were set at 5′ in order to reduce the total number of posts to 6 (those posts are not cheap). With all the manual measurements (string and tape measure along with the distance apart, the inner posts only came out only 1″ off between the two sides spanning the stream. There was a small issue (#487) with the alignment of the last post on the left far side. It was shifted inward slightly when the cement was being poured, but having done it all by myself, it was a large miracle the others didn’t move as well. Now that the posts were up, it was time to call in some favors to help haul the support beams across the stream and hook them to the posts. Dan help prep this effort pointing out helpful supports to hold the beams while we locked them into the posts. The bottom rails are made out of 2 stacked 2x12x10 boards and the top rails are a single 2x12x10 cleated together to make it the 30′ feet between the inner posts and 42′ to the outer posts on the bottom. To reduce the lift weight we did not stack the bottom rails until after we had one layer installed. It took about 6 of us to haul these beams across and lift them into place. This picture provides a good feel for the size of this structure.
Those new to the project were pretty surprised of the size. Most of them thought it was just going to be a little foot bridge across a ditch. To help stabilize the structure we added some temporary posts and set them on large patio blocks in the stream. This is also a good time to note the depth of the water. We lucked out and the level had dropped significantly while on this phase.
I have a number of favors to return now, but after a hard days work, this was a satisfying picture.
There is a 2×6″ plate on the top of the top rail and the bottom of the bottom rail in order to add stiffness (reduce flex) of the long beams. In a late design change another 2×10″ plate was put on top of the top 2×6″ plate to reduce some of the wobble and firm up the beam since it needed to hold up the bottom deck. The down supports are actually 2×6″s and although they do support some of the weight, most of the structural support is in the diagonals that go between them. With the completion of this phase, you can now walk across the stream thanks to a temporary deck make out of additional 2xs. Here is a head on shot from the near bank.
The ropes were just temporary supports to help insure the pillars didn’t collapse inward while putting on the beams. About this time, the weather was turning and the sun was checking out very early. I was able to get a few of the diagonals up myself, but I was struggling to get more than two boards up a night with having to measure, cut the angles, hold a 2x10x6′ board up by myself (with clamps of course) and have enough hands left to screw it into place. Dan and his son Jeff actually took a day of work to come over and help me knock that work out. A lifesaver without which I would probably be still standing in the middle of the stream trying to get them installed. Issues #502, #503, #504 and #505 all came about trying to figure out how to stack the diagonal boards on the beams. I will not go into detail, but imagine if you will trying to compensate for two boards per rail on the bottom, only one rail on the top, a downpost connected on the outside and not wanting to put any diagonals on the inside because that would decrease the width of the bridge. Thanks to an assist from Dan, we figured out that we could put one of the diagonals between the downposts and the other cross diagonal would attach to the outside of the downposts. If you are board (bad pun), try drawing this out. I have about 12 sheets of paper from my attempts to figure it out. I am guessing you didn’t even notice this in the picture at the top of this post. The Xs are actually skewed slightly as a result of the longer length of the outside diagonal.
Next up was the decking. The day Dan and Jeff came over we were able to get some of the decking under frame completed. 2x12s were put perpendicular to the bottom rails at about 3 foot intervals. This varied from section to section due to compensating for the cleats and interference with the temporary supports. In between these sections, 2x10s were cut and put in with hangers parallel to the rails roughly 25″ in from the outside rails. This provides a nice foundation for the decking to rest on and structural support for the ATV tires. I completed the remaining length of the span based on the three sections they were able to help on. It was definitely easier with more hands, but eventually I worked out an efficient process. The downside was having to navigate the openings since all the temporary boards in the section being worked on had to be removed… well, that and the fact it was getting down in the 30-40 degree range making it difficult to feel my fingers after awhile.
The light was beginning to appear down the project tunnel now. With the weather fighting my progress, I decided that the last task of the year was going to be putting down the deck. The approaches would wait until next spring and I really didn’t want anyone using the bridge until the footings had a chance to settle anyway. Having cleaned out both of the local Lowes of every halfway decent decking board and hauling the 45+ boards down to the bridge I was ready to complete the final task. This is probably a good time to give credit to a set of tools that were critical to the success of this entire project. It was obvious that some battery power tools would be required due to the location of the build. I had returned the genset after the brackets were installed which reduced my tool options significantly. Primarily looking for a cordless reciprocating saw we noticed a Master Force set on sale at Menards for only $145. It was an 18V NiCad and not Lithium but contained a drill, light, circular saw and two batteries along with a free skill saw and reciprocating saw. To be honest there was not high expectations but figured it would get me through most of the work. Turns out, this set of tools was a workhorse making all the cuts, drilling and screwing that needed to be done. Not to mention it was exposed to rain, sleet, snow and all kinds of harsh treatment during the course of this work. I wish it had about 2 more batteries since the cold weather really sucked up the juice, but it is pretty hard to complain at this point. So night after night and occasional vacation day brought completion of the decking. As you can see from this picture, the difficult part was cutting the edges around the diagonals (go back to your drawings to see the complexity in the diagonal stacking).
On the last night I actually put the last 4 boards down in sleet. After that last screw went in I walked up to the side of the far bank, sat down in the ice and just sat there and admired the fruits of our 4 month labor. As much as this was an effort of function (to get across the stream), there was a side goal of proving to myself I could actually do something like this. A tremendous amount of thanks goes to my brother for helping with mental (far more difficult) as well as the physical labor, to his son who gave up his time (and a vacation day) to help out and make lifesaving trips to the hardware stores and to my friends who gave up a sunny Saturday to delay their honey do lists and risk life and hernia to help me out. But the biggest thanks goes to my father who spent countless hours teaching me how to properly use a tool and letting me help on any cool projects he undertook. I know he is a little upset I didn’t invite him up to help out on this project, but I didn’t want him to be out in the crappy weather we had during most of this project and really wanted to prove to him he prepared me well. I’ll definitely let him help out putting the bridge approaches on when the weather turns better in the spring.
Here is another shot of the bridge. It was taken a few days before I finished the decking, but it is one of the few non-snow covered shots I have at the moment.
I plan to leave the temporary posts in over the winter. If the DNR complain about it I’ll remove it, but it will give me piece of mind while the footings settle. Since completing the decking, we have had days and days of continuous rain and a few days of heavy snow (last snow fall was in the 7-8″ range) the latter of which got me down there to shovel it off. This has brought the water up pretty high, but thankfully still in the banks.
And if you are a regular reader of this blog, you might recall the recent post on the dead coyote. Well, it is currently enjoying a little cold bath, but still hanging around against all odds.
Time to actually go watch the Bears. For some unknown reason they are actually beating the Vikings which means either Cutler has been yanked or the Vikings’ cornerbacks can’t catch a pass in the cold. Later everyone and thanks for taking the time to read about one of my projects.
