Pylon sign board foundation design

[App1907]

Hi,
I am asked to check the foundation stability of a pylon sign board of height 2000mm, 900mm width and 160mm thickness made of mild steel. The structure is in the middle east with a wind velocity considered around 60m/s. I have been trying to search only for the footing design of pylon sign boards and can only find boards erected on posts. Also I need to know how to calculate the design load and moment of such a structure standing directly on the ground. They usually follow the BS or ACI code here in the UAE. Thanks in advance.

 

[thaidavid40]

I'm confused. If your "pylon sign board" isn't supported on "posts" (columns), either internal, or external, what holds it up? A sketch would help a lot.
Dave

Thaidavid

 

[App1907]

@thaidavid40,
It looks like this

http://www.google.ae/imgres?imgurl=...d=0CHAQMyhLMEtqFQoTCIXhouuR08cCFUGC2wodrqIC3w

It is connected to the footing with base plates and anchor bolts. I cant find any design details for such a structure, hence I'm lost..

 

[App1907]

What I was thinking was to prepare a simple model in Staad Pro and apply wind loads to get the reaction. Reaction/SBC of soil will give me the approximate foundation size. would that be correct?

 

[thaidavid40]

@App1907,
I think that I see now what you are trying to analyze. Your posts have to have rigid, moment-carrying type bases to transmit the overturning moment and the base shear to either a spread footing, or a pair of drilled shafts. The drilled shafts would obviously be similar to an embedded post design, with the additional step of designing the base to transmit the loads. Since that approach apparently doesn't seem to fit your situation, I am guessing that you have a moment-resisting type of spread footing. This would then be a combined footing supporting both posts. You can treat the design of such a moment-resisting footing just as you would one designed for a building column with moment - and paying attention to the base plate design to ensure it can handle the moment carried to the footing.
Good luck, Dave

Thaidavid

 

[App1907]

Thanks a lot. That gave me a better understanding of the support system. The foundation and the bolted connection design have already been done, I'm assuming using the above procedure you mentioned. I just need to check if the provided foundation is sufficient enough for the overturning moment and vertical load. which is why Im thinking of using a staad model for analysis to get the base reactions. Is there anything else I need to keep in mind while preparing the model? I will check for the overturning capacity at the base of the footing using the horizontal reaction at the base of the base of the structure

 

[structSU10]

you should be able to do this by hand calculation. Its essentially a cantilever off the foundation, so the forces should be easy to figure. If the load is outside the kern of the footing, and generates an uplift condition, the soil pressure is a little more complicated to figure, but otherwise its simple P/A +/- M/S.

 

[App1907]

@stryctSU10,
But doesnt the wind loads acting on it make it more complicated? I checked the wind load manual calculations..which seemed quite complicated to do by hand

 

[BAretired]

How complicated can it be? Take a conservative uniform wind load and check it out by hand; 60 m/s is a pretty strong wind, but your sign is only 2m high.

BA

 

[App1907]

Thank you very much. I am trying to do a manual design using the wind load specs given in the BS EN 01991 - 01.4 - Eurocode 1 - Actions on structures. wind actions. However this is my first time referring the Eurocode as I was previously working in India hence only familiar with the IS codes. Can somebody please help me out in whether we need to use the pressure co-efficient Cp to calculate the design wind load or just the force co efficient Cf for sign boards? This part in the code book is a bit confusing for me. I have been able to calculate upto the basic wind pressure but unclear about the steps from here on to arrive at the design wind load for this particular structure.