1. Diaphragm are the mathematical operator which transfers the lateral forces to the vertical elements.
   
2. Diaphragm are of two types. Rigid Diaphragm and Semi-Rigid Diaphragm.
   

Rigid Diaphragm

1. Software will consider the infinite stiffness in its own plane.
2. Horizontal forces in the beams and the slab shall be equal to zero where the rigid diaphragm is defined.
3. Centre of mass and center of rigidity shall be computed and reported by the program or software.
   

Applications

1. To identify the center of mass location and location of the center of stiffness.
2. For podium or large span slabs with a limited amount of opening or ducts one can use rigid diaphragm.
3. Accidental torsion effect would be considered by the program by performing seismic analysis.
   

Semi-Rigid Diaphragm

1. Horizontal the stiffness would be calculated by the program and accordingly the lateral forces will be distributed to the vertical element
2. Centre of mass and center of stiffness cannot be calculated by the software (limitations).
3. Axial forces in the slab, the beam can be calculated and reported by the software.
4. For initial phases, it is advisable to use the rigid diaphragm and after solving Centre of Mass and Centre of Stiffness issue, we can use Semi-Rigid diaphragm.

Applications

1. At the last phase of the design Semi-rigid diaphragm should be used.
2. Accidental torsion effect would be considered by the program by performing Seismic analysis 

No Diaphragm conditions

1. Software will not calculate the eccentricity
2. Software will not calculate Diaphragm drift and Displacement
3. The lateral load will not be calculated

·       Limitations

1. Software will not consider the Eccentricity
2. It will not calculate the diaphragm drift
3. It will not calculate the diaphragm displacement
4. The lateral load will not be calculated