Continous beam with large step

[oranda]

How would you analyse continuous beam (RC or Post tensioned) with a large step (say 900mm - 1000mm, this would look like a step in stairs)? Would you just try to model a step in your analysis (this is with a computer program)? Alternatively would you model the beams as two beams with one beam supporting the other.

 

[dik]

I'd normally model it as continuous with the appropriate 'd' value for the beam above and below and treat the step as a beam with another 'd'...

Post tensioning it would be another matter. You may have to treat it as two beams and treat parts as regular reinforced and provide a pour strip between or something... it would be a matter of reviewing it and how the post-tensioning was going to deform it...

 

[Ingenuity]

I would model the step in the continuous beam analysis, and model the PT as equivalent loads due to prestress (end forces from anchorages and effects of tendon curvature within spans etc) - the step in the CG of the section at the step needs to be accountered for too via equivalent prestress "loads/forces".

Make sure the equivalent prestress is based upon realistic tendon profiles.

You will have to manually check local stress effects at the step using other techniques - maybe strut and tie method depending what is happening.

Does the step occur at/over a support or within the span?