For a support that can transfer only compression forces, the program also shows tension forces.
How is this possible?
In a result combination of your model, the load cases are connected as acting alternatively ("or"), that is, acting one time positively and one time negatively. Negative factors in an RC can be dangerous in case of nonlinear analysis. The failure of springs, tension members, etc can act in the wrong direction and you obtain nonsense results.
The reason for this can be found in the calculation of the RC results. They are combined from the available results. If a support in a load case has compressive forces, then the minus sign in the combination criterion reverses the magnitude and acts as tension force.
To avoid this issue, you can specify the load cases that are included as negative in the combination criterion as new load cases with negative loading. Alternatively, we recommend to use load combinations.