ILYAS

why 3D ? WHY NOT 2D?

justified and reasonable practice as explained above the concept of equilibrium torsion

anaylsis of raft should be run with option 3D OR 2D?

anaylsis of raft should be run with option 3D OR 2D?

ACI 318-14 (page 43) defines a wall: vertical element designed to resist axial load,lateral load or both,with horizontal length to thickness ratio greater then 3.

length to thickness is greater then 3 so treat as wall

factored shear force is determined from free body diagram obtained by cutting through the column ends,with end moments assumed equal to the nominal moments strengths

REPLY FROM CSI Ilyas, Regarding your questions: 1, 2 and 3- Results are not expected to be the same, in general, ETABS is based on 3D analysis of the building while SAFE is based on a single story. If you uncheck thick plate in SAFE slab property it is similar to shell thin in ETABS in which slab shear deformation is not accounted for in both programs. This is also depending on ETABS--->SAFE export option you are using, load cases involved, meshing, rigid zone over columns etc. 4- Please make sure to run latest version of SAFE 2016 v16.0.1 5- Concrete strength does not matter for stiff element property as program does not design stiff elements. Program magnify their bending stiffness by a factor of 100 to model the rigidity of the interface. Regards, Mohamad ____________________________ Mohamad Ali-Ahmad CSI Technical Support Computers & Structures, Inc. TECHNOLOGY FOR A BETTER WORLD 1646 N. California Blvd. Suite 600 Walnut Creek, CA 94596 – USA Main (510) 649-2200 Fax (510) 649-2299 support@csiamerica.com www.csiamerica.com

i am not refering to that case my cracking analysis option is off in SAFE, i have already done that my input is same by assuming different cases.

even the results you will have same in cracked version.

There are issues which needs to be addressed: 1-Why there is much difference in punching shear results in SAFE and ETABS models considering same parameters in both models.(same modifier, same geometry,same assignment of shell behavior in both cases though SAFE does not have the option of thin shell all other the input is same),i have checked both the cases when the automatic rigid zone area over the column is on and the second case is when this option is off. 2- I have analyzed the both cases assuming the shell thick in ETABS and thick plate in SAFE behavior,in other case thin plate in ETABS and thick/thin PLATE both in SAFE,but results still vary. 3-Even when you export same slab in SAFE the punching shear results vary in both models .There is significant difference in unbalanced moment value in both models. 4-i am using licensed ETABS 16.2.0 and SAFE 16.0.0. 5-IN SAFE Made MODEL,what should be the concrete strength of stiff elements, it should be of column strength or it should be of slab strength, if you assign the same strength (concrete) as the column have then you will get reduced moments and if you assign the slab strength you will have more moments. i have read the csi knowledge , safe manual,thin/thick shell and plate behaviour and all other data related to these issues.

agreed,thanks for correction.

NO designer will consider picked up column as part of lateral force resisting system

1-picked up columns will not be part of seismic load resisting system,so thay are treated as secondary frames and design procedure will be same as for usual columns

Thanks sir

1-How to read in 1st mode/2nd mode lateral/absolute displacement of structure in ETABS?(FOR separation purpose) 2-When you go to command " story response plots" ETabs shows unreasonable results(very less) fo lateral displacement.(case/combo =modal, output type=mode and step number=1),is step number mean mode number? 3-While in print tables option you recieve lateral/JOINT/absolute displacement corresponding to only load case,but i am intersted in mode shape.(What is lateral dispalcement of story in 1st/2nd and third mode?

1-reference point cant be deleted in etabs 2-calcalutae water pressure value and apply in horizental axis.

1-as we have To follow simplified approach in structural software to model geotechnical properties,as you are right that modulus of different soil will be different therefore i have uesd a word" accordingly". 2-anyway there are many other ways to incorporate the lateral stiffness/vertical stiffness approxiamately,Thanks .

1-Horizental (lateral stiffness) or vertical spring constant?and it will be better that you you go for point spring in case of pile rather then line spring. 2-multiply the modulus of subgrade reaction with area of pile. 3-divide the pile length into equal parts(to add modulus of subgrade reaction accordingly) and, assign the joint at intervals and then apply joint spring. 4-you will get approximately not exactly bending moments/shear force depending upon the pile end condition fixity or partially fixed ,free whatever you have.

SLAB THICKNESS IS TOO HIGH,YOU HAVE TO THINK ON ALTERNATIVE

Dear fawad najam! The methodology for seismic design has been radically changed in ASCE7-05 from that used in earlier codes like UBC 1997,the governing parameter for development of response spectrum are now the ss (short period accelaeration) and s1(one second spectral acceleration) ss and s1 can be derived from the peak ground acceleration(PGA) using empirical relationshops based on performance level(EUROCODE 8).

SIR KINDLY STUDY building code(ACI318-14) AS WELL AND THEN DISCUSS

BEAM AND COLUMN ARE DEFINE IN START OF ACI 318-14,NOT IN ANY CLAUSE

thanks ,i just came to know that we can assign inclined force (point load) to member by rotating its joint local axis but in sap not in etabs.

Can we assign force/point load with some angle to any member(shell or line element)?