Loads on Conveyor supports

[eit09]

I am working on the loading information for conveyors and would like to hear how other engineers calculate loadings.

Example:
When I have a conveyor that is supported by a truss I use ASCE Figure 6-22 (open signs & lattice Frameworks) for the conveyor truss frame & the conveyors components (idlers..). The solid area I use to calculate Cf is the area of the steel in the support truss plus the area of the idlers. I apply 100% of the wind load to the solid area of the front face of the truss and 50% of the wind load to the back face of the truss.

I then use ASCE Figure 6-21 (Chimneys, Tanks, Rooftop Equipment, & Similar Structures) for the belt wind loads. For applying the wind load to the belt I assume half the belt width x the length of the conveyor for the area. The reason I use half the width is I assume it acts like a sail forming a parabolic shape.

I neglect all loads in the direction of the conveyor.

Calculations from others:

Engineer #1
Provides wind load on full height of belt & 100% of wind load on both faces of the truss

Conveyor Co. #1
Provides wind load to truss assuming bottom of truss to top of idler is solid

Conveyor Co. #2
Provides 100% wind load to front face truss members and half width of belt x length of belt.

 

[JAE]

I'd tend to go with Engineer #1. I'm not sure how you can (code-wise) justify 50% on the far truss but I know engineers do that.

 

[eit09]

Thanks JAE!
IMO the front face would provides some sheilding to the back face. Thats how I would justify the 50% load reduction if I were ever questioned.

 

[bootlegend]

I treat the truss as one item and calculate the wind load on it as a truss tower and apply the full load each both sides (no shielding).

I treat the idlers and belt profile as a open sign (fig 6-22 ASCE 7-05) and Cf always comes out to the 1.6, but depending on the style of idler, spacing, and the troughing angle you may get up to 1.8 I suppose. I apply half of this load to each of the top two chords.

For the walkway I use the lattice framework charts and apply half the load to each bottom chord if it is mounted there, or split between all four chords depending on the mounting.

 

[eit09]

bootlegend,

For the belt profile do you use the full height of the belt to apply WL?

 

[bootlegend]

eit09,

Yes. I use the full vertical projection of the belt and idler. This means the area will vary for different idler can sizes and troughing angle combinations.

 

[TLHS]

Also, consider what you're conveying. I've seen some conveyors on mine sites that have a hell of a lot of material buildup on the surrounding... well... everything. In that case you're going to get voids in your structural steel that fill up with material and provide a greater wind area.

 

[Vinnende]

Hi Everyone,

I'm currently performing wind tunnel tests on open trussed conveyor arrangements, using a scaled model. I'd be very interested to hear what aspects of this you'd like clarified most.

My current general plan is to test the model with wind normal to the truss face, under a variety of configurations.

1. Conveyor Belt (inc. idlers, return belt, etc)
2. Structure Frame (4 structural chords only - no truss members) + Conveyor Belt (inc. idlers, return belt, etc)
3. Full Structure (not including services/walkways etc.) + Conveyor Belt (inc. idlers, return belt, etc)
4. Complete arrangement
5. Increasing the solidity of the face by adding sheets of impermeable material until the solidity is 1.

Then I plan to test for shielding in the case of dual conveyors running parallel. s = spacing between conveyor trusses, d = height of truss structure

1. s/d = 0.5
2. s/d = 1
3. s/d = 2

I also plan to test for the effect of a circular cover over the material, as well as the effect of the material being at critical repose.

The objective will be to develop design charts, that are valid for an arbitrary arrangement. Inputs will be solidity + arrangement type (ie. is it trussed, services, material, cover, etc.). Outputs will be a drag coefficient to use based on a given projected area of an arrangement (such that a total force can be calculated), as well as guidelines on how to accurately distribute this total force on the structure so that overturning forces match those found in experimentation, and the primary load paths from wind loading are (approximately) accounted for.

Is there anything obvious I'm missing, or would this be sufficient to answer most the questions engineers have regarding wind loading of these conveyors?

Thanks