All the S/W packages that are mentioned above are developed using FEM(Finite Element Method - A Numerical Modeling Technique ) which is one of the most commonly used numerical modeling technique and validated for the use in analysis of structures that are subjected to  static as well as dynamic loading cases. you can find many literature for your understanding.

But these softwares are having some computation limitations, such as either in terms of boundary specifications, material descritpion, computation algorithm etc., , few point which i understood over this period are covered below :

SAP2000 & ETABS :

Basically both are almost the same since it is from the same developer , this package can be used for static and dynamic analysis of any type of structures, but most commonly used cases  for analyzing are RCC structures & steel structures. The advantage that ETABS offer over the SAP2000 is that it has more advanced computation algorithms which are implemented to analyse any complex high rise structure in lesser resources(time & memory). Also ETABS has more user friendly input options to generate the complex high rise structure's model, where as in SAP2000 its difficult to model discretely.

STAD Pro :

This S/W Package, the static analysis is preferred than dynamic analysis, because it is bit tedious process and results may not be more reliable. Basically STADD Pro is commonly used to analyse steel structures but can also be used for several other types too with careful note on the numbers :D .  

STRAP : Im hearing for the first time. so not sure ! but any software package has its own limitation in performing computation but the results of analysis should always be the same otherwise there is something going wrong in any of the parameter that is involved in over all analysis computation( which is basically limitation of S/W Package) May be the user manual can help us knowing about the "What are the limitations this software package has ?" or we should spend some time in understanding the limitations of these packages which will be very much help full to all  ! :) 

And finally yeah!  i agree with @Tareq Alsaleh's message too, don't rely on the reinforcement detailing for some time, still some more validations has to be made on it.

Thanks :) hope this would be helpful to you ! :) 

Its better not to depend on the reinforcement details that comes from those programs , while you can use the analysis outputs ( Moment , Shear ... , etc )   which I believe they should be the same for all the programs in case of using the same code , loading case , factors ... 

Dear Mr. Alsaleh and Mr. Bao-Jie He,

I modelled plan irregular high-rise building in STRAP and STAAD Pro. Its showing different analysis results. I used same code and loading conditions in both tools while modelling.  

All the S/W packages that are mentioned above are developed using FEM(Finite Element Method - A Numerical Modeling Technique ) which is one of the most commonly used numerical modeling technique and validated for the use in analysis of structures that are subjected to  static as well as dynamic loading cases. you can find many literature for your understanding.

But these softwares are having some computation limitations, such as either in terms of boundary specifications, material descritpion, computation algorithm etc., , few point which i understood over this period are covered below :

SAP2000 & ETABS :

Basically both are almost the same since it is from the same developer , this package can be used for static and dynamic analysis of any type of structures, but most commonly used cases  for analyzing are RCC structures & steel structures. The advantage that ETABS offer over the SAP2000 is that it has more advanced computation algorithms which are implemented to analyse any complex high rise structure in lesser resources(time & memory). Also ETABS has more user friendly input options to generate the complex high rise structure's model, where as in SAP2000 its difficult to model discretely.

STAD Pro :

This S/W Package, the static analysis is preferred than dynamic analysis, because it is bit tedious process and results may not be more reliable. Basically STADD Pro is commonly used to analyse steel structures but can also be used for several other types too with careful note on the numbers :D .  

STRAP : Im hearing for the first time. so not sure ! but any software package has its own limitation in performing computation but the results of analysis should always be the same otherwise there is something going wrong in any of the parameter that is involved in over all analysis computation( which is basically limitation of S/W Package) May be the user manual can help us knowing about the "What are the limitations this software package has ?" or we should spend some time in understanding the limitations of these packages which will be very much help full to all  ! :) 

And finally yeah!  i agree with @Tareq Alsaleh's message too, don't rely on the reinforcement detailing for some time, still some more validations has to be made on it.

Thanks :) hope this would be helpful to you ! :) 

Dear Mandar Pandurang Ganbavale, 

Actually the results of analysis should match with the classical analysis solutions,  what ever the type of analysis you do using what ever S/W package . The finer thing that you should note in all these packages is that ,  there are  parameters/properties such as boundary conditions, material properties etc.,which are applied to the generated model by the software package by default at the initial stage.  May be the ambiguity you observed in results arise due to these default params. and these by default properties/ parameters changes from one S/W package to other.

May be more inspection of these inputs may give better results ! :) sometimes closer or exact ! :)  

Staad pro, STRAP, ETABS and SAP 2000

Sap2000 v15 is solely a generic software for FEM analysis of generic structures.

Sap2000v12 had bridge modules included but later in sap2000 v15 they separated the bridge module and kept it in the CSIBridge.

Etabs is also a part of sap2000 but it is specifically to analyze the structures like building.

Staad pro is a generic software for fem analysis.You need to check what modules and capabilities it provides.

ETABS is the most advanced (from among what I’ve seen). ETABS has facility for:

- Construction sequence analysis.

- Push-over analysis. (RISA 3D also has this facility)

- Shear wall design that’s practically very useful (STRAP also has this. Results from STAAD are confusing to me)

- Live load reduction for upper floors (STAAD doesn’t have this)

- Earth quake force can be applied in any angle (not just X and Y alone)

- Modelling tapered concrete beams

- Floor load for irregular panels, that is easy to do (STRAP too has this)

- Design of columns with cross section of any arbitrary shape (including T, L, +. STRAP too has this)

- Diaphram action (with earthquake loads and wind loads automatically applied on the diaphragm centre)

- Automatic lumping of masses for earthquake (STAAD doesn’t have this, STRAP and NISA/Civil has)

- Choice of Eigen or Ritz vector for Response Spectrum analysis

- Auto calculation of beam reinforcements based on moments at column face, rather than at column centreline; and column reinforcements based on moments at beam soffit, rather than at beam centreline

ETABS and SAP2000 are probably much more capable of providing you with accurate results for dynamic seismic analyses than any other software. The different results can be due to one of many of the following reasons (these factors being different in the different software you have tried);

• The modal combination methods adopted by default (or through your selection) may have been different.  CQC is recommended if many of the participating modes are close to each other, otherwise SRSS is adequate
• Directional combination method (CQC is preferred - SRSS is also OK) may be different
• Mass source definition
• Choice of Eigen or Ritz vectors for modal analysis. You can refer the CSI knowledge base online for a comprehensive description on what to use where.
• Meshing of floor slabs, walls and other shell elements

Your results may vary slightly due to the above factors being different in each of the software you chose. However, if you have a simple symmetric building model the results should not change by that much. However, if the building is complex with large and varying aspect ratios for eg. you can experience drastic differences in your results. ETABS and SAP2000 are through my experience the best to analyse for dynamic behaviour.

Good question.. Please share me the best answer might you trust...

Regards…

refer the research paper

State of the Art Report - A Comparative Study of Structural Analysis and Design Software - STAAD Pro, SAP-2000 & ETABS Software