STAAD PRO PUSHOVER ANALYSIS

I have been analyzing a model for pushover analysis. I have roof bracing of HSSP members which STAAD does not recognize as a circular type & I keep getting error messages that I need to model these as circular section (which they are already!). I end up re-modeling these as PIPE. STAAD then forces me to change some of these to W or T or channel shape as I keep getting error message "   ***ERROR : ONLY WIDE FLANGE, TEE, AND CHANNEL   ARE ACCEPTED AS BEAM/COLUMN IN PUSHOVER ANALYSIS. "  although these are not beams or columns but roof or wall plane bracing. I ran the program & kept changing these individually to W shape (for sake of making the program run). Although if I ever mange to finish the design of the structure it has no resemblance to my original with all these force changes due to STAAD PUSHOVER  ANALYSIS Package bugs & limited capabilities. In the process of changing these bracing to a type that Staad Pushover accept & let it run I get a new message which I have not seen before namely "EXCEPTION (ACCESS VIOLATION) RAISED! ABORTING ANALSIS".

Can some one let me know how to resolve this?

Parents Reply
  • Mohandes,

    If you run your first model with the command

    PERFORM BUCKLING ANALYSIS

    the buckling factor for the first mode is reported as 1.04. It means that the applied loads in your model are very close to the capacity of the structure calculated from a linear buckling analysis.

    By changing the full releases to partial releases as DSANJU has suggested, the buckling factor for the first mode goes up to 1.63. The revised model that he has provided represents a structure that is more stable.



Children
  • Thank you Kris. It solves the fatal error but I have left with a structure with so many member different from my original design that either I have to re-design and change my building to the same member type that Staad Pushover accept which is not what I can do as we have all our building with circular section for bracing which staad does not like. So need to find an alternative program which does what is expected rather than staad which is a) not up to date to the latest code ASCE 41-06 rather than outdated FEMA356  b) limit in which  member type can be used & C) if you lucky program works without any fatal error.

  • Kris /DSENJU Thanks for your reply. Can you tell me how Can I solve the error "   **ERROR : MASS PARTICIPATION IS LESS THAN 75 PERCENT IN PUSH LOAD DIRECTION. FURTHER ANALYSIS IS STOPPED."

    What does it really means? Does it mean the structure does not response to the seismic spectrum as less than 75% of the mass participate or it is because FEMA 356 require more than 75% participation for lateral load distribution (i.e. Clause 3.3.3.2.3 of FEMA]. Please Note the 75% limit stated in FEMA 3.3.3.2.3 is no longer in its replacement i.e. ASCE 41-06 Clause 3.3.3.2.3.

    Furthermore FEMA440 (which partially replaces FEMA356) no longer recommend multiple load pattern & states that a single pattern based on first mode shape is recommended.

    Any idea re timetable when Bentley are expected to address the problem (which was also confirmed by DSANJU post)?

  • Lateral load distribution pattern determines magnitudes of shears, moments and deformations within the structure. If lateral load distribution changes structural behavior also changes. Hence, use of more than one lateral load distribution pattern is recommended in Pushover Analysis. One needs to do this to arrive at the conclusion of the possible behavior of the structure that may occur during actual dynamic response. Use of simply one lateral load distribution will not give you desirable result for Pushover Analysis.

    As per Section 3.3.3.2.3 of FEMA-256, lateral load distribution has been divided into two broad groups - a) Load distribution depends on modal pattern where 75% of mass participation is must and b) Load distribution depends on mass distribution. Group a) contains 3 sub-groups of which two are implemented (Method 1 and Method 2). Group b) contains 2 subgroups of which one is implemented (Method 3). One needs to take one lateral load distribution from group a) (use VDB 1 or 2) and the lateral load distribution from group b) (use VDB 3). Model should be analyzed separately with each of these lateral load distribution and the results should be compared.

    Since use of lateral load distribution from group a) is a must, you will get the mass participation error message even if you use load distribution from group b). The reason is simple - even if you succeed in analyzing the structure for VDB = 3, you will fail for VDB = 1 or 2.

    Thus to arrive at the best possible solution use of both methods is must.



  • Dear DSANU

    I assume you are refereeing to FEMA356-2000 as FEMA 256 is a "Flood Management & Development" Standard. Please note that FEMA 356-2000 which Staad Pushover is based on is a "Pre-Standard". It was never published as a Standard. It was partly replaced by FEMA440, which is a Standard. With regards to participation please refer to ASCE 41-06 clause C3.3.2.4 (referencing  recent research in FEMA-440-2005). Furthermore the actual code to which a push over should have been written is ASCE 41-06.  Staad Development team are way behind the latest approved Standard (to be exact 8 years(2014-2006)). Staad Pushover Program  should have a warning for the user saying the approach used here is based on a superseded code.

    Furthermore what does the user has to do when they get the error "MASS PARTICIPATION IS LESS THAN 75 PERCENT IN PUSH LOAD DIRECTION. FURTHER ANALYSIS IS STOPPED". It is not clear on any of on line document or the Help Menu of  Staad Advance Analysis package.

  • Dear DSANU

    Further to my post yesterday regarding the error "MASS PARTICIPATION IS LESS THAN 75 PERCENT IN PUSH LOAD DIRECTION. FURTHER ANALYSIS IS STOPPED".  I had to modify the member selected by you (i.e. Channel etc) & turn them to equivalent  member as far as properties of AX/IX/Zx to my original HSSP section.

    Here is my original model (including the bracing elements in roof that I originally had to remove to pass the above error). Instead of deleting these members from my model, I used Inactive command. I followed your instruction of using moment release at 0.99. However in doing so I get the other error i.e. "EXCEPTION (ACCESS VIOLATION) RAISED! ABORTING ANALSIS". If I makes these element active I get the Mass participation error. Note that some these were already fully release in my model so the moment release may not have much impact.  It seems like Catch 22! Either way I get an error which not possible to by pass.

    I still do not know what a user of STAAD pushover has to do when they get the error "MASS PARTICIPATION IS LESS THAN 75 PERCENT IN PUSH LOAD DIRECTION. FURTHER ANALYSIS IS STOPPED". It is not clear on any of on line document or the Help Menu of  Staad Advance Analysis package. Surely you should be able to check any structure for push over analysis.

    Any further guidance or ideas, would be appreciated. Thanks in advance.