I am using AISC 360 code. How can I have STAAD do deflection check for service cases and do strength check for ultimate cases ?

For AISC 360-10, the design routine can do deflection checks based on SERVICEABILITY LOAD ENVELOPES and strength checks based on STRENGTH LOAD ENVELOPES as part of the same design cycle. One needs to define serviceability envelope and strength envelope first consisting of the appropriate cases and then define a LOAD LIST ENV command  for the design to consider these as explained below.

For example if you have a strength load case 10 and a serviceability case 11, you can set up the design as shown next

…

DEFINE ENVELOPE

11 ENVELOPE 1 TYPE SERVICEABILITY

10 ENVELOPE 2 TYPE STRENGTH

END DEFINE ENVELOPE

LOAD LIST ENVELOPE 1 2

PARAMETER

CODE AISC UNIFIED 2010

METHOD ASD

*specify all design parameters here including DFF, DJ1, DJ2

CHECK CODE ALL

…

The Load Envelopes are for grouping load cases based on whether they are service type cases ( used for serviceability checks like deflection checks ) or strength type cases ( used for strength checks ). In the example two envelopes has been defined

Envelope 1 – Serviceability Envelope

Envelope 2 - Strength Envelope

Load case 11 has been assigned to the Serviceability envelope ( Envelope 1 ) which means that the software will only check deflections for this case.

Load case 10 has been assigned to the Strength envelope ( Envelope 2 ) which means that the software will check member strengths for this case. No deflection check will be carried out for this load case.

One can define the Load Envelopes using the Graphic user interface as shown next

More details on load envelopes can be found at section 5.40 of the Help documentation.