Live Load Increase for "Hanging Load" 1

[Nameless_One]

Hello,

I am dealing a small project which includes the design of a overhead retail sign. The project requires a live load to be considered to account for someone jumping up and hanging on the sign. My question is, should this live load consider an impact load factor in addition to the 1.6 LRFD load factor. My intuition leads me to believe it should, but I am having a hard time finding anything code related that confirms my thought. Any info is apprciated.

Thanks

 

[BAretired]

On the lower end of the scale, I would forget about it, i.e. live load is zero. On the upper end of the scale, 5000# is what OSHA requires per person for a fall protection system. The load could be applied anywhere on the structure. Sounds a bit goofy to me, but you don't want vandals getting killed from the fall, do you?

BA

 

[phamENG]

Yes, I'd use an impact factor of 2 in addition to the LRFD load factor. So L=2xweight of the person jumping up and grabbing it. So if your 'design person' is 250lbs, then L=0.5K. 1.6L=0.8K.

This is assuming somebody jumps up as you described. If there's a means for them to jump down onto the sign, you'd need to calculate your impact factor with the height of the surface above the sign taken into consideration.

 

[GC_Hopi]

Agree with above, you have to use engineering judgement. Here is another data point. 2,000 lb for lower chord of commercial garages.

 

[human909]

Remember that the LRFD is a probability factor. The further down the path of explicitly designing for X load the less reasonable it is to have a probability load on it.

Yes, I'd use an impact factor of 2 in addition to the LRFD load factor. So L=2xweight of the person jumping up and grabbing it. So if your 'design person' is 250lbs, then L=0.5K. 1.6L=0.8K.

Not too many people can dead hang 800pounds. You'd be designing for a beast of a person there! Remember if you are genuinely designing for a person hanging off the sign then that same load needs to be transferred through that persons fingers. There is no additional impact force ontop of that load that is restrained by the persons fingers and arms. A person jumping up and grabbing something to hang off is quite low impact.

That said greater context is needed regarding likelihood and consequence. Also load direction could be just as much of a concern. Jump, grab, swing could impart significant lateral loads which depending on the attachment could be more damaging than a vertical load.

 

[Settingsun]

GC_Hopi, that load of 2000# sounds as though it's for lifting things, eg engine.

Ladder rung loading is my contribution here. Someone could slip and make a grab while falling.

Or:

 

[MotorCity]

You can debate the impact factor and load to use, but in my opinion, the prudent thing to do is eliminate the hazard. If it is possible for someone to jump up and hang on the sign, it seems like the owner is inviting problems and lawsuits. Another thing to consider is that even if you design the connection for such a load, if the sign is not designed to withstand the same load, this simply is an exercise in futility.

 

[dhengr]

Nameless_One:
It’s partly a risk and reward calculation; or risk, and current costs vs. future saving/future costs/future headaches calc. Try to make the sign or structure at its bottom elevation impossible to hold onto, so that they can’t hang from it. Hang it from above, at an elevation which is to high to jump to and grab. Provide smooth contours and no hand holds/grabs at its lower levels so they just can’t hold on. Hang it high enough so they can’t reach it. Of course, that becomes pretty difficult on some structures, with exposed structure like truss bottom chords, etc. Whatever your time and extra materials costs them now, you will save them ten or one hundred times that amount if you minimize their attorney and court costs/time, at some future date. In our litigious times and our country’s court system, you can’t always prevent stupid people and jerks from acting out, but you can maximize the potential for a simple defense when can show that you did all you could to minimize their likelihood of being hurt by their own stupidity.

 

[Nameless_One]

Thanks all for the responses. Much Appreciated!