masonry containment/tank

[bmagdalena]

Hi

I have project where I have containment structure for a tank, which will have to hold liquid in case of spilling. I'm using masonry blocks. Wall is only 4ft tall, liquid level 2ft. structure is rectangular 31'x31'.
Can I apply design methods from ACI 350 and just use values for masonry?

 

[cntw1953]

I think you shall follow ACI 530 for masonry works. I would consider provide suitable liners, depending on properties of the contained liquid, for leakage prevention.

 

[bmagdalena]

the reason I was thinking about ACI350 is because this code recognize rectangular tanks. If just follow ACI530, the loads would be computed based on ASCE 7. but ASCE7 section 15.7.6 is for rectangular tanks only.

 

[cntw1953]

If you are design the parapet around a contaiment area, then it is simply a cantilever beam subjects to pressure with triangle distribution (density x depth). Then you have to check against the proper code (ACI 530 for your case) to ensure the stresses are within allowable.

Am I missing something here?

 

[bmagdalena]

ok, so in my case, since wall acts as containment in case of spill, and not as tank wall, I don’t have to check for seismic load for tanks (sloshing effect etc).

thanks

 

[cntw1953]

I could have misunderstand something, but, it is a tank if there is lid (roof) over the wall, otherwise it is a simple retaining (cantilever/parapet) wall. However, for either case you would need to check the wall for inertia forces and hydrodynamic effects induced from a seismic event in a seismic active region. The only difference is what type of structural system the forces are acting upon, not the requirement of checking.

Think about this, are you sure the wall will remain functioning and serve its purpose? Before checking, there is no straight answer.

Please talk to your boss or seniors to setup design criteria, and determine proper code for the design and check.

Good luck.

 

[bmagdalena]

it is a wall around 2 tanks, so the idea is that in case of spill from one tank it will retain liquid till is pumped out. tanks are anchored into the slab and are design for seismic load, so probability of earthquake before liquid is clean up is small.
I guess my main question was if I can use ACI350 to calculate inertia force and convective force, since this is only code that I found that has equations for rectangular, open top tanks. I would assume that if spill occur my containment wall acts like open top rectangular tank.

I would take this with my senior but currently he is on thanksgiving vacation

 

[ARLORD]

I would use cast-in-place concrete.

 

[cntw1953]

Except for the calculation of inertia forces, type of wall material does not affect the exterior applied forces (loadings), nor load patterns. However, once you have obtained the reactions, material properties and proper selection of the code/specification become important, as in many cases, the code/specification is material specific, such as AISC for steel, ACI 318/350 for concrete, and ACI 530 for masonry...

Check IBC on how to apply and make load combinations, then check stresses/strength use the code specifically developed for the material in use.

I agree, it would be a rare event that the wall will experience both spill and earthquake at the same time, but I wouldn't ignore it completely.

As suggested by LRLORD, concrete wall sounds a better choice.

 

[msquared48]

Concrete wall would be best, agreed. But, in either case, I would design the wall and footing for a 4 foot liquid depth to account for short term impact and sloshing, waterproof the inside and be done with it.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[bmagdalena]

ok, thanks

 

[cvg]

spill and then subsequent earthquake could be very likely and not as rare as you think. Consider the scenario - earthquake causes tank to leak. Second quake (either main shock or aftershock) hits within minutes /hours or perhaps a day after the first quake. It is not unusual for aftershocks to be nearly as severe as the main shock and certainly capable of knocking over a wall.

 

[bmagdalena]

cvg, you got good point.
I was going to design the wall for forces due to the earthquake any way. thanks

 

[JAE]

ACI 350 won't apply to masonry walls. For masonry, a liner would be required I think as the block/mortar interface isn't all that liquid-tight. ACI 350 is a code directed at cast-in-place concrete to ensure durable, more liquid-tight structures.

 

[bmagdalena]

JAE

I agree that ACI350 is for concrete not masonry. But ACI350 is the only code that has equation to calculate seismic forces for rectangular, open top tanks due to liquid movement. That was the point of my question.

After calculating seismic forces I will use ACI530 to design masonry wall, or ACI350 if client goes with concrete wall.

 

[JAE]

bmagdalena, OK. I don't have 350 handy but I don't recall analysis/seismic force information in it. Could you give me a reference within 350? 350 and 318 are almost identical in general content and organization and there is no analysis/seismic within 318 other than a few simple/continuous beam moment equations.

 

[bmagdalena]

chapter 4 is for calculating earthquake forces and moments above the base due to inertia forces, hydrodynamic impulsive pressure and hydrodynamic convective pressure from liquid, chapter 5 is for earthquake load distribution.
and now that I’m looking closer the code is ACI350.3 it is for computing seismic forces only, and it is companion document to chapter 21 of ACI350.

 

[JAE]

OK - yes....350.3 makes sense...not 350. Thanks