Why does the load history deflection increase when reinforcement is added?  

In some situations adding additional user reinforcement can unexpectedly increase long term deflection predicted from Load History Analysis. 

There are several factors that should be considered, but one potential cause for this is “shrinkage warping” behavior. Adding reinforcement on the flexural tension face tends to increase cracked moment of inertia and reduce cracked curvature due to loading, but also increases the curvatures due to shrinkage. Think about what happens as shrinkage occurs on a cross section with reinforcement on only the flexural tension face. The flexural tension face is restrained by the reinforcement, while the compression face is free to deform. The result is a curvature and resulting deflection, even in the absence of loading. There are also stresses induced on both the reinforcement and concrete by this behavior (which RAM Concept also account for).

A test to isolate this is to set shrinkage strain to zero.

See Also

RAM Concept Load History Calc Options TN