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Dear Sir, Please explain briefly. What is the value in assigning Area Spring? Direction is Local Axis-3. According to my friend, this value is depending on the bearing capacity(B.C) of soil. For example, for 2.24 ksf of B.C, this value is 2.24 x12 = 26.88, he said. But, I am not sure about this value and reason. So, explain briefly for my question. With bundle of thanks, Aung Myat thu MilLimetRe-training & Design Group Taunggyi, Shan State, Myanmar 0936048015, 09260329221

Greetings Everyone, I am doing a case study for validating the results of ETABS and SAFE using same input data. I am using ETABS 2017v and SAFE 2020v. I have assumed same data to be modeled and analyzed in both software. I have been trying to figure out the difference in my results but no use. I am providing the input data for reference for correction. I have modeled 4 bays (in both x and y directions) with 25' each. Drawn the raft section on grids. I am modeling raft for 10 stories but I will model single story and multiply my loads with 10 for just comparison. RAFT=24"; Slab=6"(for self weight calculation); Modulus of Subgrade reaction=240kip/ft2/ft (Assumed); SDL=90psf; LL=40psf All the loads are factored [(1.2 dead load)+(1.6 live load)] applied as point loads on joints. I have 3 types of joints (Corner, Middle, Edge joints) with their corresponding contributing areas. The loads come to be Corner Joint Loads=410kips; Edge Joint Loads=820kips; Middle Joint Loads=1630kips All loads are assigned under the load pattern of SDL. I have also provided size of load for punching shear X=36"; Y=36". Assigned all raft sections area spring with stated data in direction 3 and compression only. Ran the analysis and displayed base reactions. Results were not matching. I had to explain all the steps so to convey my message properly. KEYPOINT: I am assuming that the inconsistency is coming from the assignment of area springs. Because in ETABS the input data is "Spring Constant/ Unit Area" while in SAFE it is directly defined by the Modulus of subgrade reaction. I even tried to multiply the subgrade modulus with their tributary areas and assigned to their respective areas in ETABS but no use. RESULT VARIATION (Screenshots Attached): The corner joints in both ETABS and SAFE are providing consistent results. The edge joints of ETABS have double base reactions to that of SAFE. The middle joints of ETABS have four times the reactions of SAFE. ANOTHER CLEARIFICATION: I also tried in SAFE v12 and SAFE v16 but I am unable to display the base point reactions in those versions with the same model I was able to display them in Version 20. Thanks and regards, Muhammad Fawad Khan. B.Sc. Civil Engineering UET Peshawar. Etabs Model Final.EDB Safe Model Final 2020 Result.FDB

AsSalaam alaikum dear members, I am new both here and structural engineering. I'm just a fresh graduate, recently joined a consultancy co.. I want to know in details about joint spring, area spring, line spring as we see them in Etabs. When to assign them based on what understanding. It will be OK if i am given some links to somewhere, or books, if it's already discussed. Thanks.

Assalam-u-alikum for modeling raft foundation in etabs the supports for raft is point spring or area springs support?How i will assign value to a spring?