General

On the load case data for construction stage analysis, what exactly is the difference between Load Objects and Load Objects If Added?

"Load Objects" will load all objects in the specified group using the specified load, regardless whether or not they were added in the current stage. "Load Objects If Added" will load only the objects in the specified group that were added in the current stage.

Why the stresses (shears and moments) dissapear after changing section properties in staged construction?

See Staged Construction Operations

How can I extract creep, shinkage and secondary prestress effect, respectively from the staged-construction analysis result?

For statically indeterminate structures, this is not possible since the shrinkage strains can cause stresses that affect the creep so they ca not be separated (unless the effect of shrinkage on creep is neglected).

For statically determinate structures, the procedure is not automated, but you could do some post-processing of SAP2000 results to obtain an estimate of these forces. For example, you could analyze the response with creep and without the creep and then the estimate effects of creep from the difference between the two responses.

How I can do design for individual stages of staged construction load case?

Extended Question: I need to do a code check for steel members for a certain step in a staged construction load case. The code checker uses design load combination for checking. I do not seem to be able to define a load combination that includes the results of certain step from a staged construction load case. Can this be done?

Answer: You could replace each stage (or sequence of stages) for which you need to perform the design by a standalone staged construction load case that would be using stiffness at the end of a load case for the previous stage. Then the design load combination can be created for these new load cases that essentially represent the individual stages in the construction stage analysis.