Developing Steel Stoplog to hold back water forces

[CaliEngineer16]

My goal is to develop 12 7ft stoplogs that can be stacked (3 per bay for a max height of 21ft) and will be fabricated to stop the water from flowing into the levee pipes. The bay is 9.5ft, with stoplog channel, I have steel stop logs with a width of 122in.

I have already determined the force of water to be 1.3 k-ft. The steel face plate will be 1/4" thick, with 6"x5" HSS bracing every 21" OC (weak axis). I am now at the point where I need to determine how the load will be transferred from the plate and bracing, to the channel. I am looking to use an L beam which will be welded to the bracing and will push up against the channel, supporting the force of water.

How do I calculate the load from this support? I guess what I'm trying to ask is, how do I go about sizing which L beam I need from this setup? I'm using the AISC Steel Manual so feel free to reference that.

See attachment for rough drawing

 

[JedClampett]

Simple answer is tributary area times load per square feet. But why is the guide slot so large and your L beam (an angle?) so big? Why don't you make your slot the same size as your plate plus HSS, 5.25 inches plus a little slop? You're just adding another member to design.
But if you have a reason to design the stop log that way, it's just compression on a plate. Do a kl/r on the plate and be conservative. It is a variable load, so if you design the bottom 12 inches, it's conservative for the rest of it.
Stop logs see very large loads. Be conservative and be sure to pay attention to the load path. I'd armor plate the groove, too. Bearing on the concrete might cause problems.

 

[CaliEngineer16]

The gap from HSS and L beam was more of an exaggeration. I could use a 6"x"6" L beam if it could handle the load. And that's where I'm at in the design, determining which L beam can handle that load if welded like in the rough drawing.

And the reason there's another member in the design is because of the water. The L beams on each side would solidify the gate as well as make it easier to install a rubber seal along this beam to keep the water out (to an extent). Installing the rubber seal on the back will ensure that the force of water is helping me create s tighter seal.

 

[DamsInc]

How are the logs going to be installed/removed? Is there significant water flow? You may get a good seal against the gains, but the friction could make it very difficult to remove the logs. Is the channel embedded in a concrete structure? In that case the channel would be acting more as a bearing plate, than a member in bending.

 

[cvg]

why wouldn't you call up Waterman, Rodney Hunt, Hydrogate or another manufacturer and ask them to suggest one of their standard products? these are not generally custom designed but manufactured using standard drawings.

 

[CaliEngineer16]

They will be lifted with a crane from lifting bars that will be welded on the top. And I don't know why we're not going through rodney hunt or hydrogate, this is just the assignment my boss gave me (I work for the state).

Since the bracing will be welded on the L beam, it will be handling the shear forces of the HSS. I'm basically just going to pick a reasonable sized L beam and check for buckling. What would be the best way to check for buckling from a load being applied like this (see attachment)?

 

[cvg]

http://files.engineering.com/getfil...32&file=hydrogate_stop_Logs_and_bulkheads.pdf

 

[CaliEngineer16]

that doesn't help me, thanks though

 

[JedClampett]

Figure out the load per inch (or foot). Calculate your weak axis "r" for that section. Do a kl/r with l being the unsupported legth of the angle (in the direction of the load) and use k=1.2 to be conservative. It will probably be about 70 or even less. Than go to the AISC, and see what they allow for a compression section with that kl/r. A little more math figuring out stresses per inch or foot and you've got an allowable (from AISC) and an actual stress. If the allowable is more and your units are consistent, you're done.

 

[CaliEngineer16]

Thank you Jed, that sounds about right. And ya, with k=1.2, i get about 80. I was considering even using k=2 since it's almost like a fixed/free-end from where the load is being applied. The AISC spec. section E on compression shows Fe for elastic buckling, and Fcr for critical stress. As long as the force being applied downward on the L beam < the critical stress, I should be good then right?