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Number of holes in Double angular

Number of holes in Double angular

Number of holes in Double angular

(OP)
Hi,

When you have a doble angular in X form and you have to calculate the number of holes to put in angle members, you have to consider all posibbilities of holes in the section. I have made this assumption (in the attached file).

Could anyone help me is my assumption is right?

And like this kind of doble angular always have plates. Could I increase the gross area in angle properties?

Thanks.

RE: Number of holes in Double angular

I have never used or specified these cruciform cross double angle type legs, so I don't know how the holes are specified. The section in the PLS-Tower manual 3.1.2.4.1 describes what to do for bolts. For lacing members you input the stagger and edge distances, but for legs I guess you have to do it manually.

As far as using the plates for the area, I doubt that you should since they will change the tension and compression allowable of the built up member. From what I recall, the individual single angles should be stitched together so that their individual L/r is smaller than the gross L/r and they don't buckle before the entire built up member.

You might need to find someone from SAE in Spain or Italy that use a lot of these built up legs to find out how they did it.

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

RE: Number of holes in Double angular

(OP)
I ask for add the gross area of the plates because in some legs of the tower, in de body, the angles fail around 103% at NET SECTION. In the real construction at the connection between two legs you really have more section than in the model of PLS-TOWER.

Probably 103% only at NET SECTION in the real tower is not a problem but I try to quantify the real construction of the tower. For this kind of cruciform double angles, in the connection between two legs you have the both angles and plates and a small part of angle (I don't know the english name, sorre). You can see in the attached file.

Thanks

RE: Number of holes in Double angular

Unless the stitch plates that connect the 2 main angles are continuous, I'm not sure if you can count on them to add area for tension. If they are at the leg splice, then I would say that you can add them there. If the legs are connected by the stitch plates between lacing connections, then you should count the holes out for that cross section and not include the stitch plates because the tension is carried by only the 2 main leg angles through the holes out for the stitch plates.

You can probably count on the leg material being a minimum yield and it is probably a little higher than minimum so 103% should not be a problem.

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

RE: Number of holes in Double angular

(OP)
I know that 103% should not be a problem, but I would like be more precise.

Yesterday I modeled the tower trying (you can see in the attached file) to represent the connection between legs. And only in this zone add the gross area of the plates. The plates are continous along the holes of both legs, more or less around 500-600 mm.

Thanks

RE: Number of holes in Double angular

(OP)
I have one more doubt.

When PLS-TOWER calculate the joint between two legs (double shear). Which is the effective Area PLS-TOWER use? I mean, for example. The joint is between L100*8 and L100*8 and the joint is double shear. PLS-TOWER calculate with thickness of the joint 8 mm?

But really you have the leg, the inner angle and the outside plate (double shear). How tower calculate?

Thanks.

RE: Number of holes in Double angular

I'm not sure if I understand the question. Is it a leg butt splice for the cruciform leg where you have a splice plate or splice angle? The double shear is just to determine the number of shear planes on the bolts to see if they are overstressed. The net section is for the tension capacity and IIRC, they take the gross area and subtract the holes so if I think about a double leg in a cross shape the number of holes will be for both angles because the gross area is for 2 leg angles.

To really be sure how it is done, you can eMail the PLS-CADD people and ask them. This assumes you are a current customer and have phone and eMail support. They should be happy to explain how the program handles double angles.

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

RE: Number of holes in Double angular

1 - You should not ( Can not ) count splice plate and splice angle area for net area calculation.
2 - No of holes for deduction minimum Four ( In case of no zig zak failure). For design consider Six to Seven in PLS.
3 - 103% ( With out considering splice plate & angle )is OK as in real world as most of the time Yield stress of material is more then specified value. Normally legs are more critical in compression then in tension


Nitin patel
India

RE: Number of holes in Double angular

(OP)
Thak you transmissiontowers and nitin36537,

I will send an email to PLS-CADD to be sure.

I am agree with you nitin36537 on your point 3.

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