Abnormal Level Earthquake(ALE) Analysis With SACS

Hi, 

Could I know is it possible to perform Abnormal Level Earthquake (ALE) with SACS?

Is there any example for this analysis in SACS manual or samples?

Thanks!

Parents
  • You can do it by either Response spectrum or Time History depend on your available information.

    ALE is low probability of occurrence. Actually, it can be done by using 'Nonlinear Inelastic Analysis' which can be performed by SACS collapse.

    However, it you can make it pass code requirement with 'Linear Elastic Analysis with Code-Checking'. It is unnecessary to perform costly analysis like nonlinear inelastic analysis.
  • My friend just taught me how to run Seismic for Strength Requirement using Response Spectrum by Spectral Earthquake.
    I have a few more question:
    1. For low seismic activity zone, the "Strength Requirement" should be sufficient right?
    2. Could I know how to perform non-linear analysis to meet "Ductility requirement" with SACS Collapse? Any procedure/step and methodology? Is there any examples in SACS manual"?
  • Hi Pei Shing,

    1. SLE and DLE are two different considerations which you can refer to design code such as API (chapter 2.3.6.a of API 21st). Generally for area with strength level acceleration less than 0.10g, no ductile level analysis was required.
    2. The process of performing an ALE(or DLE) analysis in SACS is similar to a strength level earthquake in the first few steps, foundation linearization - mode shape extraction - dynamic response of earthquake input. The only difference for these two is in the DYRINP file of seismic response, for DLE you need an extra "EQKLOD" command line to generate equivalent static load of seismic(see 2.2.1.3.2 of dynamic response manual). With the equivalent static load generated in the OCI file, you can perform a collapse analysis to explore the platform reserve capacity against a rare intense earthquake(RSR can be calculated).

    Kevin

    Answer Verified By: Pei Shing Ooi 

  • Based on my understanding of your answer, for low seismic zone, if from the Strength Requirement analysis, the member, joints and foundation passed the UC requirement, not further action for ductility level analysis.

    In case the UCs is above 1 even after we consider AMOD of 1.7, we can proceed with ductility level design.

    For Strength analysis, below are my steps
    Step 1 Static (for combine later)
    Step 2 Superelement
    Step 3 Eigenvalue
    Step 4 Dynresp + combine
    Step 5 Post Analysis

    I repeat step 2 to 4 for base shear iteration with EQKLOD command line, only the base shear is constant then only changed to STCMB.

    In Step 5, there are 3 separate code checks for post:
    6.1 Member UC
    6.2 Joint UC
    6.3 Pile and Foundation

    Is this the correct steps for ductility level design? Please correct me if I'm wrong.
    1. For ductility design, I still perform step 2 to 4 till I get the oci file from EQKLOD, then I combine the oci loads to static sacinp file.
    2. Is the methodology for Collapse analysis very similar to the sample problem 2 in Collapse Manual? I need to prepare a collapse input file similar to sample problem 2, however need to change to loadcn 1 and 2 in sample problems 2 to my static case, Loadcn 3 to the loads from OCI file.
    3. Do you have any other samples for ductility level analysis for seismic for SACS?

    Thank you very much for your explanation.
Reply
  • Based on my understanding of your answer, for low seismic zone, if from the Strength Requirement analysis, the member, joints and foundation passed the UC requirement, not further action for ductility level analysis.

    In case the UCs is above 1 even after we consider AMOD of 1.7, we can proceed with ductility level design.

    For Strength analysis, below are my steps
    Step 1 Static (for combine later)
    Step 2 Superelement
    Step 3 Eigenvalue
    Step 4 Dynresp + combine
    Step 5 Post Analysis

    I repeat step 2 to 4 for base shear iteration with EQKLOD command line, only the base shear is constant then only changed to STCMB.

    In Step 5, there are 3 separate code checks for post:
    6.1 Member UC
    6.2 Joint UC
    6.3 Pile and Foundation

    Is this the correct steps for ductility level design? Please correct me if I'm wrong.
    1. For ductility design, I still perform step 2 to 4 till I get the oci file from EQKLOD, then I combine the oci loads to static sacinp file.
    2. Is the methodology for Collapse analysis very similar to the sample problem 2 in Collapse Manual? I need to prepare a collapse input file similar to sample problem 2, however need to change to loadcn 1 and 2 in sample problems 2 to my static case, Loadcn 3 to the loads from OCI file.
    3. Do you have any other samples for ductility level analysis for seismic for SACS?

    Thank you very much for your explanation.
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