RAM Concept: Precompression values on Design Strips

Question

HI, Can anyone clear my following queries from RAM Concept 
 1) The Centroid stress plots under the Rule Set design reflects the Precompression forces in the slab ? 
 2) We have noticed that the precompression value reduces if we put an additional short tendon and stop midway in the slab rather than putting it till the end. When we remove this short tendon, it regains back its precompression values. This shouldn't happen in reality as any additional tendon should help the slab to attain more precompression force. We believe it is because the slab elements are meshed as nodal points and when the short tendon ends, due to difference is displacement between two nodal plates( one with the tendon and one without the tendon), it takes the average of two location and displays the precompression force at that point. Is it true?

Karl G · Answer

1) The centroid stress is the axial stress at the centroid of the cross section that make up the cross section. It is calculated from the resultant axial force and bending moment in the strip and the cross sectional area. Both precompression from tendons and restraint of supports which effectively reduce precompression are reflected in the stress. 
 2) Please share your model with the short tendon for review. You can use the Secure File Upload link at the bottom of the page to send us the model. Please post back here after the file is uploaded.

Seth Guthrie · Answer

You can look at the balance load layer to see the applied load effect of the tendons, or just plot the tendon forces to see the total force and divide that by the section area to establish a pre-compression without 2nd order effects, but there is no easy way to separate the direct effect of the tendons from the 2nd order effect of the restraints. You could put everything on rollers (and auto-stabilize the model as another approach). 
 Whenever you are working with T-beams and axial forces these concept are important: RAM Concept T-Beams and Axial Force TN