Wind loads on a moving structure? 3

[vato]

I am designing a bracing system for modified shipping containers to be shipped by train. Would forces derived from ASCE7 be applicable to a moving structure. The train travels at 60 mph and the wind blows at 90 mph. I put them 90degs to each other and added them up. Twopointfive questions:
1. Is the force from a 3second gust higher than a constant wind ie train moving?
2. The structure is on top of a moving platform, the train car, is ASCE7 the correct reference? If not, what else is there besides the wind tunnel?
It's a cool problem. Thanks for the help

 

[RWF7437]

What about the centripetal force when the train is rounding a curve and is speeding at, say, 90 mph on a windy day ?

 

[haynewp]

I would ask AREMA, ASCE 7 is not meant for this.

 

[vato]

RWF7437 thanks, there is also a 2g lateral force to design for. Should this be combined with a wind load? Not sure. Perhaps that is like a full siesmic and full wind load combination, which we rarely consider.

haynewp thanks, I'm checking it out, trying to get the loading without purchasing a railway design manual.

 

[civilperson]

No trains are running full speed with 90 mph wind.

 

[vato]

civilperson - I agree, but that doesn't really help. I could certainly imagine a train running at 60mph that encounters a head wind of 90mph. Yes the train would slow down as my structures catch that breeze and transmit the forces into the rail car. Wouldn't the structure "see" 150mph wind for a moment?

 

[RWF7437]

http://www.arema.org/eseries/scriptcontent/index.cfm

 

[civilperson]

90 mph wind is major storm and all sirens, weather radios and civil agencies will be in full "Take Cover" mode. The engineer will be advised and decrease speed prior to experiencing the full force of the wind. The structure that you are designing may be able to withstand wind forces of the magnitude considered, but the train may not stay on the rails. Use ASCE wind loading for stationary train, (include right angle overturning with 1.5 FS) and then you are covered. Coastal wind speeds are 110 mph or greater and the train may go to the shore. The object being carried must fit through the bridges, tunnels and restrictive ROW along the proposed route. The railroad company will check the limits of clear dimensions for every proposed track route.

 

[kslee1000]

Agree with civilperson's suggestion "Use ASCE wind loading for stationary train, (include right angle overturning with 1.5 FS).

The critical wind case is side wind (normal to direction of train) on the train/container, not the head wind. I believe relativity can explain the effect of wind on a moving object is less critical than on stationary object.

 

[tngv752]

I had done a similar thing two year ago. I designed a steel tower which was carried by a ship. I had considered the sea water speed (acerlation) and combined with the wind load in all direction. These give you all the forces in all direction (longitudinal, lateal, uplift and downward forces), for example : vertical downward force is 1.5g, longitudinal force is 2g etc. I did get those combination from the clients manual design.

 

[msquared48]

OK, and you get a 90mph gust on a superelevated curve from the outside of the curve.

Mike McCann
MMC Engineering

 

[vato]

msquared48 - Yes, that is what I have been thinking. But the question remains, is the wind pressure from the train moving at 60mph more or less than the forces from the 60 mph 3 second gust per ASCE7? Also, the worst case head wind of 150 mph seems to be worse than the train at 60 with a cross wind on this particular structure.

There is also the temporary nature of the structure to take into account. I usually don't like decreasing a factor of safety due to the temporary nature of a structure, but it is starting to seem reasonable in this case.

 

[Ron]

I believe you are looking for the Durst Curve....see attached.

 

[vato]

Thank you Ron. I believe that is exactly what I need.

 

[JAE]

Way to go, Ron.

 

[kslee1000]

vato:

Link below maybe helpful.

http://portal.railresearch.org.uk/RRUK/Shared Documents/workshop2008/a5 bouferrouk.pdf

 

[Ron]

JAE...thanks....goes to my delightfully varied career! I make my living doing weird stuff.

If a train leaves Pittsburgh at 3:00pm........