Loading tests on overhead line structures

[rubenpezu]

Hello,

I have to test a TOWER in the test station (my first time) and I have a doubt. I have to prepare the loads for the test. I try to use the PLS-TOWER to obtain this loads but I'm not sure If it is right.
Now I have a maximun puntual loads of the structure in the crossarms wiht my national wind pressure (2550 Pa). And I put some clamps in the body according de IEC 60652 to obtain the wind loads in the body (put the load of one stretch in one point). But this loads I think are small.
My doubt is, this load that TOWER gives to me are right? or I have to calculate the wind force of the stretch manually and later put into the TOWER model. As you can see in the attached file the difference is important.

Thank you.

 

[transmissiontowers]

In the Criteria file, what was the wind on structure assumption? Did you use wind on all or one of the code based winds? If you have put all your redundants into the tower model, I really prefer ASCE-74-2009M which uses a fluid mechanics method to put wind on each member. The problem is that the loads are not displayed on the tower. Since you are generating wind on tower loads, you probably need to pick a wind method that calculates the wind and places it at the joints.

If all your redundants are not in the tower model, you will have to adjust your Section drag factors to account for the missing members.

I'll have to take a look at your pictures and give some more thought to it. It's getting late in Texas and 4:00am comes too soon when the alarm goes off.

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I have been called "A storehouse of worthless information" many times.

 

[rubenpezu]

I have to use the national code of Spain, because the tower is to use in Spain. The wind is on face and the pressure is 2550 Pa (170 daN/m2).

I have made some manual calculations. One is take the area gives me PLS-TOWER and multiplicate by 170 daN/m2. This result is a puntual force to apply in the real test in one section in one joint between two legs. For example the area between stretch 1 and 2 multiplicate by 170 daN/m2 apply in the joint between stretch 1 and 2.

After the previous result, I have made the same calculation but taking the areas en the drawing in AUTOCAD and multiply by 170 daN/m2. The result was very similar, about 1% difference.

You are right, for obtain a similar value in PLS-TOWER, I have to put in every joint in the model a clamp and later show the loads in the wind load case. If I add every force in every joint the result is a little bit more than the manual calculation.

I suppose that the more exactly result is take the areas of the AUTOCAD drawing and later multiply by 170 daN/m2. Am I right?

I really thanks all your support. Thank you very much.

 

[transmissiontowers]

I'm not familiar with the Spanish code or if it allows you to neglect the wind on the side faces because of shielding by the legs. If you allow PLS-CADD to calculate the basic wind pressure, remember that when it applies the pressure in TOWER, it used the gust and height factors. Also remember that the wind pressure is not adjusted for shape and the pressure calculated in PLS-CADD is for round members. You will need to apply the 1.6 shape factor for the front face members and another 1.6 for the back face members. Many times you can just apply a 3.2 shape factor to members in the front face and apply the joint loads only to the front face.

For a tower test, you can probably calculate the wind pressure for all the members in a face between the top and bottom joints and apply the point loads to the top 2 joints on the front face. Then you apply the point loads in the real test with cables attached to the front joints to simulate the wind on the tower. The wind on tower for a normal tower accounts for a small percentage of the overall load assuming you have long spans and big wires.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[nitin36537]

Whatever wind load values you calculate ( Manually or Through PLS ), before testing do PLS Tower analysis with wind load as point load on model and make sure that all members are OK.

Do not forgot to distribute wind load on top and bottom nodes.

Nitin Patel

 

[rubenpezu]

thanks Nitin,

I will do.