Combination method

Hello All,

I'm kinda new to pipe stress and CAESAR II. would you please tell me why we use the scalar method to sum (SUS+OCC) ? I'm reading CAESAR help but it just says that Scalar is typically used to sum (SUS + OCC) code stresses. it doesn't mention why?

and also why is SRSS method used to sum seismic directional components?

Thanks

A scalar summation just sums the magnitudes of the two stresses, which is what the Code requires. (If you change the summation to Algebraic, then the sum of the displacements would be used to recomputed forces/moments, and then stresses. This is not what the Code asks for.)

The SRSS method determines the vector sum of the components.

When you're in the Load Case Editor, click in the "summation type" column, then click "F1" and review the help text. There are numerical examples here that will illustrate the different methods.

Thanks Richard. I understand the method but don't understand why do we use the SRSS specially for summing seismic components. I'd be so thankful if you help me with that.

It depends on how you specify the seismic load. If you've specified individual vectors (directions), then you need to perform a vector summation - i.e. SRSS.

Thanks