HELP REGARDING TIME HISTORY

Can you help me with time history load, I already finish the time history loading and run analysis using perform anlysis

and then finish the design and displacement check, all members passed.

1. My question, Is my input for time history load correct?

2. Do I use perform anlaysis or non-linear or steady state etc?

3. Can i assume my structure subject to harmonic load because the structure is on top of turbine table thus using time history load is appropriate?

4. For the stress and displacement check of the member thus my results ok or do I need to generate load cases just like RSA wherein you need generate IMR load cases?

5. Regarding mass participation I only achieve 74% in y direction, how to increase, can I use cut-off mode?

6. Do i disregard the warning   *WARNING- APPLIED SELFWEIGHT IS MORE THAN TOTAL WEIGHT OF ALL  ?

7. What is the relationship between mode shape and deflection?

Attached is the staad file

A1CJK02 SUPPORT_7slave_timeHistory.std

Parents
  • 1. Took a quick look at the model. The only thing you may want to check is that the maximum displacement is almost 25 inches at the top node 169. This is due to the softer material you have used for the L20X20X2.5

    2. You should use perform analysis.

    3. Since the acceleration at the base is coming from the operation of a turbine, I think it is ok to represent it using a harmonic function

    4. Load combination is fine. IMR is only appropriate for RSA.

    5. In addition to CUT OFF MODE which I set to 20, I also added the CUT OFF FREQ 1000 to allow for the high frequency modes. I also reduced the integration time step DT to 0.0001. The mass participation in Y is close to 98% now.

    6. The following wiki should explain what the warning is and based on that you can decide whether to disregard or not

    7. In simplest terms, mode shape shows the way or the manner in which the structure is vibrating in a particular mode. Deflection is the actual amount by which the structure being displaced in a particular mode. Mode shape coefficients are used in computing the deflections.

    A  modified file is attached for your reference

    A1CJK02 SUPPORT_7slave_timeHistory_rev.std



    Answer Verified By: Jonathan  

Reply
  • 1. Took a quick look at the model. The only thing you may want to check is that the maximum displacement is almost 25 inches at the top node 169. This is due to the softer material you have used for the L20X20X2.5

    2. You should use perform analysis.

    3. Since the acceleration at the base is coming from the operation of a turbine, I think it is ok to represent it using a harmonic function

    4. Load combination is fine. IMR is only appropriate for RSA.

    5. In addition to CUT OFF MODE which I set to 20, I also added the CUT OFF FREQ 1000 to allow for the high frequency modes. I also reduced the integration time step DT to 0.0001. The mass participation in Y is close to 98% now.

    6. The following wiki should explain what the warning is and based on that you can decide whether to disregard or not

    7. In simplest terms, mode shape shows the way or the manner in which the structure is vibrating in a particular mode. Deflection is the actual amount by which the structure being displaced in a particular mode. Mode shape coefficients are used in computing the deflections.

    A  modified file is attached for your reference

    A1CJK02 SUPPORT_7slave_timeHistory_rev.std



    Answer Verified By: Jonathan  

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