Hi everyone, I am designing a st

[Eng_Girl]

Hi everyone,

I am designing a stoplog gain which is essentially a channel or in my case two angles bolted to a concrete wall which hold 10 x 10’s in place. See attached sketch.

In this configuration I’m loading the flange of an angle. I have sized the angle flange based on bending and shear and found I need to add stiffeners spaces at 400 mm.

I’ve sized the stiffener thickness based on the assumption that the stiffener acts as a column. See attached hand calculations.

Is this the correct approach?

 

[SlideRuleEra]

Use a heavier angle (if available) that does not need stiffeners.

Reasons: Bolted to concrete in a wet environment, the angles will receive little maintenance. Overtime, stiffener welds will be the first thing to fail.

Thicker angle will provide a corrosion allowance for the angle itself.

Extra cost of heavier angle will be competitive with stiffener fabrication cost.​

Are stiffeners (or heavier angle) needed on the upstream side?

 

[Eng_Girl]

Good point about the welds, I hadnt thought of that.
The load is on the downstream angle so stiffeners arent needed on the upstream side.

 

[dhengr]

Eng_Girl:
That looks like the lateral retaining structure/system for timbers, in a dam gate or sluice channel, to control the water elevation, and provide a spill way for overtopping of the water. I would shop fab. that member out of three plates. The downstream flange (thicker flg.) takes the primary hydrostatic forces and potential impact loading on the top timbers, while the upstream flange (maybe thinner) keeps the timbers from floating away. The back plate is pre-drilled for fixing to the conc. of the dam or channel wall, spaces the flg. pls. for the timbers, and transmits the loads into the conc. structure. Sometimes, the conc. has cast-in shear slots for this back pl. or the timbers. Of course some consideration should be given to a corrosion, but welds do not just automatically fall apart/rust-to-dust because they are welds. You must pick the appropriate materials for the conditions.

SRE is absolutely right, make the pls. thick enough, without stiffeners. The stiffeners just add weld and detail complexity which, if nothing else, will collect debris, and clog up the works. Otherwise, the angles and stiffeners increase the weld length and complexity and the potential for weld defects, lack of weld joint sealing, and stress raisers due to multi-axial stresses at intersecting corners, etc.

 

[dik]

What are you fastening to? Concrete... I'd not use ASTM A307 bolts, but would use Hilti chem anchors Hit-Hy 200V3 and HAS E-55 or threaded ASTM F1554 Grade 55S1. Also leave clearance for the timber logs swelling a bit as they become saturated. I'd use HDG for the fasteners, though...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[cvg]

you might consider prefab stoplogs/frames

 

[Eng_Girl]

Thanks for your replies!

We did have a prefab option but it was extremely costly, double the price of getting it manufactured.

In order to make the downstream plate thick enough it'd have to be 38 mm thick... It was too heavy so I had to use stiffeners. I followed a similar approach to the clients other sites (they own many dams with stoplog gains) and they seemed happy with the design. Thank you for your input!