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Yes, its is necessary to define the static seismic load case first

@@Torq123 what if in command file, i have pasted earthquake first even though load case number for DL and LL is 1 &2 respectively. will it work?

@@Enfld1122 STAAD doesn't have the feature to handle the material non linearity . The only inelastic rotational effect ( plastic rotation ) is considered for pushover analysis is for steel structures per FEMA guidelines ( non linear static analysis done for seismic evaluation) . Apart from that there are no extensive what you perform material inelastic analysis

@@Torq123 thanks for replying. It's okay that, staad pro doesn't have features of material non linearity. Does staad pro has feature/s of "GEOMETRIC NON-LINEARITY" & "CONTACT NON-LINEARITY" ? If yes, Which methodology does staad pro adopt for accounting the geometric & contact non-linearity?

@@Enfld1122 Yes STAAD does have GNL and to some extend boundary non linearity like compression only and tension only specs

@@Enfld1122 For GNL there are different types , PDelta effect is also a types of geometric non linearity. In addition to PDelta analysis STAAD does have rigorous Geometric Non Linear algorithm to capture several effects like Large deformation effect . Here the program solves the geometric non linear responses by the tangent matrix procedures. The applied load is divided into small units and sequentially applied . In every step the stiffness is updated due to the change in geometric shapes . On the other hand the Pdelta analysis is done by force vector iteration.

@@Torq123 Thank for replying. It has been observed that, there was several lackings/inabilities in staad pro regarding material non-linearity and contact non-linearity, which needs to be incorporated in staad pro for capturing appropriate effect of the same. Please suggest the parameters regarding material and contact non-linearities, so that it can be posted in "STAAD BRAND IDEA" tabs for implementation in advance version of staad.

Thanks for your comment and this is indeed an pertinent question. Please see my webinar in this where detailed discussion was made . Hope you could find some help from there. th-cam.com/video/HjZBvYfXOkM/w-d-xo.html

@@Torq123 thank you Torq,

thanks for your comment. Yes it’s pinned

Thanks , the load combination and repeat are not the same although the main objective is to determine the response against the combined loading action . Now the Load Combination in Staad simply sun them algebraically and hence you can expect the correct result if the structure behaves linearly. However the REPEAT LOAD option actually generates a new load case and the same is resolved not by alzebric summation but by solving stiffness matrix . And hence if there is any non linear condition the Repeat Load exactly captures the same . Regarding your second point, when the compression only springs experiences tension, they get switched off and hence when there is uplift these springs will be switched off if the REPEAT LOAD is used

@@Torq123 Thanks for your response. I want to know that in some software there is option for generating LOAD CASES from LOAD COMBINATIONS. so is this for the same reason as that making repeat load in staad ?

Please check here 20:30 .

It depends on how the structure behaves . If the structure behaves non linearly then Repeat Load is must. Some example are like Pdelta case, Tension Only or Compression Only specifications, Direct analysis or Geometric NonLinear case . These are all generates non linear response in structure. Now one might argue how to know if the pdelta effect is present in the structure or not . Now the PDelta or the 2nd order effect exist is all the structure but in different magnitude. If this effect is very pronounced then only we need to consider its effect or treat the structure as non linear . A general thumb is to check the 2nd order drift to first order drift , if it exceeds more than 5% in deviation, then always consider the Pdelta effect . That means here you must use the Repeat Load . Now you can use Repeat Load feature in any structure irrespective of linear or non linear but you can use load combination only if the structure responds linearly..

It's okay that if the deviation of 2nd order drift to 1St order drift is exceeds by 5%, then structure is considered as non linear and p delta effect should be considered, but p delta effect or drift deviation is applicable only for building like structures.what about structures other than building like structures? i.e underground tanks, pipe racks, equipment supporting structures, retaining walls etc . How to determine about non linearity of such structures?

@@Enfld1122 Yes , the thumb rule of 5% is based of ASCE prescription for drift mostly for building like structures. Now coming to machine supporting structures( general block or table structure , retaining wall and underground tank , the PDelta effect is insignificant. Secondary moment is most pronounced is tall and slender members . …The structure that you mentioned are mostly compact. but still if you are concerned about to check if second order moment are indeed developed in the those compact structures, you might want to run the model both with Pdelta and Perform Analysis separately and compare the maximum deflection. If the difference is negligible then it indicates second order moment is insignificant..Yes other type of non linearity might existing like Compression Only plate mat support . So if the compression only , tension only specs are involved, use repeat load ..

th-cam.com/video/71dqxjiHWMM/w-d-xo.html

@@Torq123 sorry but this is part1 and this video here is part 2 and in the end of part 2 u said there will be a other session! which mean part 3 could please provide a link for that?

@@Torq123 check here 51:51

@@gamingfps1611 sorry part3 is not created yet

@@Torq123 ok thanks alot, these videos really helps me alot

You can go to our website connect.bentley.com

Thanks. I will try

If you mean by base shear comparison which are determined by status seismic and dynamic analysis and apply that as scaled factor for response quantities then yea Staad does it automatically.

It was there in the some version ik earlier edition but its available in CE.

Thanks Modestas . Yes it’s indeed a lot more we engineers have to contribute to the society.. Nice talking to you after a long time..😊

Please share your email.

I got it, now it’s flawless. Thank you. I need one info. Suppose I am designing a dynamic pump skid. Can I ignore transient effect . ? Since in the above example we are Taking steady state and ignoring transient effect.

@@prajwalbm9508 transient part is in the initial phase of the vibrating motion. Very quickly it decays depending on the damping of the structural arrangement. In case you want to check the transient part too then use the THA. You may create the time vs acc pairs in spreadsheets from the speed zero upto certain speed ( till you can assess the decay of the transient part) and feed these values in time history definition and perform the analysis.

@@Torq123 Thanks for the quick response. I performed time history harmonic analysis for my skid (Displacement against time). As u told for initial fraction of seconds my displacement are high. (>1 in) later in steady state it’s around 0.7 in, but my skid spring capacity is 1 in. I am bit confused here.

@@prajwalbm9508 there could be two reason . (1) transient component is significant (2) the natural frequency is very close to the operating frequency at the start ( natural frequency is low)..

Thanks

These are two different methods to combine the responses against the individual modes to find the resultant response . You can follow IS 1893 where the expression is mentioned

You can still define diaphragm but only with Master-Slave ( zx) option. For direct floor diaphragm option, you must have to define Reference Load.

@@Torq123 thank you sir. in other wards, it is better to define reference DL ..R1 ,LL..R2 load and assign DL LL as ref 1.R1,0.5 R2 then utilise create mass model and assign diaphargm. is it correct way sir

@@fazalarju yes

@@fazalarju yes you need to define the ref load with dead and live and designate the load type as MASS and then it will be used as Mass Modeling..

Thanks for your comment. NL Time History is not yet implemented in Staad . Time History analysis is Staad is based on the modal analysis which based on superimposition principles ( linear) .. However , one can do Response spectrum analysis in conjunction with Geometric NL analysis like Pdelta analysis by Geometric stiffness based approach . I have already created a video on the same in my channel . You may visit the same .

@@Torq123 sir, is it correct approach to conjunct analysis method as a non linear(like geometric non linear) and seismic analysis as a linear method (modal time history analysis)?

We can do GNL in conjunction to the dynamic analysis .Essentially, under this scheme, the program converts the non linear path into a equivalent linear condition by (k+Kg ) matrix and directly solves then rather doing iteration... here the program we are using the geometric stiffness method to active the final solution by modifying s the stiffness matrix directly by KG so that the modal analysis can be performed on the modified (K+Kg) matrix . This method gives good result for building like structure undergoing PDelta effect. This method is first proposed by Edward Wilson which was then implemented in many building analysis package like SAP, RAM , Staad etc

@@nooranistores8015 Please watch this video for more detail...th-cam.com/video/3fhjVEXfP88/w-d-xo.html

While modeling with no end release in Staad it’s shear Center considered but in reality the connection is on the face . It doesn’t matter much unless the depth of the section is huge .

Sure . I will upload the file and share the download link .

Sir, on which platform we can download these mentioned staad file??

@@nooranistores8015 Today I will try to upload in a ftp site and share you the link if possible

Thanks a lot lot sir....

@@Torq123 sir, kindly share the videos, links and some staad files for study purpose....

Thanks for your words

Thanks for your comment

Sure , I am working on it. Thanks for your request