I have a mind bender for everyone. We have an annular plate at the base of a thin shelled tubular structure. The base is usually unstiffened. When this fails, we try one stiffener per bolt and change the method of calculation to PL/6 (partially fixed) between stiffeners and then size the stiffener for compression (ungrouted base). Often, when one stiffener is used, the calculation shows that the plate has a higher capacity in annular bending than it does as a stiffened plate (the stiffeners are too far apart). When this occurs, we then use a two stiffener per bolt solution. Usually, the stiffened plate calculation governs and me move on down the road.
I've been presented with a case study which shows that the annular bending capacity is much higher than the stiffened plate capacity and the geometry is locked in. The only reason I can come up with for the answers given are that the stiffeners are too far apart to work effectively and the annular bending will control the design. I don't buy that the stiffeners are doing nothing...merely going along for the ride. Does anyone know of a way to calculate a combination of annular bending and stiffened plate behavior working in conjunction, without the use of FEA. I was unable to find anything in Rourk and the problem is very complex for statics.
I've been presented with a case study which shows that the annular bending capacity is much higher than the stiffened plate capacity and the geometry is locked in. The only reason I can come up with for the answers given are that the stiffeners are too far apart to work effectively and the annular bending will control the design. I don't buy that the stiffeners are doing nothing...merely going along for the ride. Does anyone know of a way to calculate a combination of annular bending and stiffened plate behavior working in conjunction, without the use of FEA. I was unable to find anything in Rourk and the problem is very complex for statics.
