3. In SAP2000 (Version 14) model,
a. At the particular floor level, select all the slab joints, you want to assign diaphragm to
b. Go to 'Assign' menu.
c. Select 'Joint' and then 'Constraints' in sub-menu.'Assign/Define Constraints' window will be displayed.
c. Select 'Diaphragm' from the 'Chose Constraints to Add' drop-down list.
d. Click on 'Add New Constraint' button.'Diaphragm Constraint' window will be displayed.
e. Change the 'Diaphragm Name' and/or 'axis' , if required.
f. Press 'OK' to apply the option to selected slab joints.
HTH
A good structural engineer is often a blessing for others.