Abdullah Anjum

I need help regarding MAT footing design in safe. Please read questions mentioned below and comment if any extra step or correction need to be done. This MAT footing is for 4 storey building in zone 2A and bearing capacity would be more than 1.25 ton/sft. 1) Does we need to increase the bearing capacity by 33% as mentioned in NILSON book for soil pressure calculation or not if we are taking basic load combinations of UBC including earthquake loads not the alternative load combinations. 2) If we want to take reduced live load for footing then is there any way to export in form of reactions from Etabs to safe. In my opinion Etabs does not give Reduced live load reaction, Correct me if I am wrong. 3) When we use the basic load combinations which include earthquake load then there is very localized uplift (due to earthquake combo) when we check soil pressure. is it normal or something wrong with my reactions. If it is normal then we always used non-linear basic combinations to check soil pressure and non-linear design combinations for design of raft? 4) Does it required to check crack width and settlement in case of raft or not. If required then explain in few words. 5) At boundary of raft where there are shear walls/lift core, soil pressure is more than the bearing capacity in these localized regions. what we need to overcome this situation if we cannot increase the area of raft at that side. any additional check which you think important for design then write in comment your help would be appreciated Regards

Thanx

Dear All, Could anyone suggest me assigning diaphragm like assigned in attached pic is correct for this building. If it is correct then how could we apply torsional irregularity in static load cases (earthquake case eccentricities override). I can calculate and apply it in simple building but in this building there would be two options of diaphragm( D1 & D2) in eccentricity override option in etabs ( If my assigned diaphragms are correct). which one i need to select.