Dear Punashri Prakash Phadnis

Commonly existence of infill frames in a structure will raise the amount of stiffness . on the other hand it's a brittle element not a ductile one and can not take part in ductility of structure !!

So the main question which journal reviewer think on it is that how a structure has better performance with infill frame ?? and he/she asked you to prove it .

the answer is that infill frame cause an artificial stiffness which can not continue during strong ground motion (earthquake) duration because in early stage of IDA or Pushover analysis it will fail and collapse suddenly however it will constraint the corresponding or related columns in real situation therefor the structure can not shake as well as it has been considered in design ( proper drift that considered in designing process ) and you can not use the bending potential of the columns . As it is obvious existing infill frames limit the displacement and drift of structure during earthquake but you have designed your structure for a specific drift ( in other word for specific target displacement ) to obtain the ductility ( R coefficient ) of that type of structure ( special moment frame, dual systems, etc ) . lets imagine that we designed a structure for example a special steel moment frame with specific Ru , we want to do pushover analysis to ensure that this structure will hit the target displacement and satisfy the performance level like life safety ( LS level ) and according to calculation our target displacement obtained as 20 cm at the center of the roof mass . in this example infill frame can cause the structure to has lateral displacement less than 20 cm because it prevent the structure to shake normally and infill will make displacement limitation because it has very high in plan stiffness .

even in some cases infill frames lead to brittle failure of their adjacent columns because they prevent adjacent columns to shake freely and in this manner some times the column behavior is not proper because the columns and structure must resist 20 cm target displacement to reach their performance level but now they have used 15 cm of target displacement while they damaged more than 20 cm .

the true modeling and simulation is that use links element which their stiffness will be removed after specific axial force or displacement to simulate the effect of collapse of infill frame .

You may refer to the following article 10.1016/j.istruc.2022.09.108

The presence of infill has a huge impact on increasing the stiffness of the frame that you are studying when compared to bare frames by limiting column displacements.