Eccentricity concideration due to reinforcement.

[dmitriy555]

I have a tower pipe leg, reinforced with a single angle welded along its length. The reinforcement changes the centroid of the new reinf. leg and thus creates a load eccentricity. When a uplift load is applied to the leg, that extra eccentricity creates an additional moment that has to be taken by the anchor bolts. However, i need to determine if the pier portion of the foundation will have to resist that additional moment. Please see the attached sketch.
As often seen from practice, most towers are built not perfectly in the center of the pier but with some offset due to construction process.

 

[BAretired]

I don't think the eccentricity affects the load in the anchor bolts. What it does is creates a constant eccentricity in the member.

BA

 

[dmitriy555]

what exactly do yo umean by constatn eccentricity? and if eccentricity exist at the connection (i.e. anchor bolts) shouldn't the connection experience the moment?

 

[BAretired]

If the uplift force is centered on the pipe and the pipe is centered on the c.g. of the anchor bolts, the tension is eccentric to the built up column but not to the bolts.

The moment in the column would be P*e from top to bottom but if the connection at both ends of the pipe are hinged, there is no moment transferred to the bolts.

If the pipe is welded to the base plate, the plate would try to resist column rotation, setting up a small moment in the anchor bolt group but it seems to me it could safely be ignored.

BA