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  1. shin25

    Scaling Down Design Values of Combined Response Spectrum

    Not sure why your RSA is showing larger base shear than the base shear calculated by equivalent lateral force method. When you calculated the static base shear did you limit the structure's period to maximum allowable by the code?
  2. shin25

    Calculate Building Stiffness

    Since it's a two story building there are two modes of vibrations. Natural frequency for the first mode will be lower than the 2nd mode, hence the effective stiffness of the building will be lower for the 1st mode as well. since, the stiffness is directly related to structure mass and frequency...
  3. shin25

    Basement Wall Analysis (take 2)

    Correction: I meant to say distribution factor for load NOT moment.
  4. shin25

    Basement Wall Analysis (take 2)

    As hokie said, the load will be distributed based on the proportion of the stiffness. If you know how to calculate the beam stiffness (hint: may consider slightly stiffer than simple span beam in each direction)then the distribution factor for flexure for each direction beam can be calculated...
  5. shin25

    Plastic hinging

    I agree with hokie66. Since under a design earthquake, a plastic hinge could undergo enough straining to get into the range of strain hardening, it is very important to also consider possibility of strain hardening that could deliver additional member capacity during capacity protection design...
  6. shin25

    pile cap design

    How many columns do you have per pile cap, more than one for a 24 pile cap? As the others said, for a single column cap, the cap will be a cantilever beam. However, if you have more than one column then the cap will behave like a continuous beam between columns. In order to determine moment...
  7. shin25

    Damping for Static Seismic analysis

    IF you are analyzing the structure for seismic, then the code specified damping is 5%. However, damping value should be less for dynamic analysis for wind, machinery or wave induced fatigue. Under those types of loading the structure essentially remains elastic and so the damping is relatively...
  8. shin25

    Pseudo Spectral Acceleration

    The difference between spectral and pseudo spectral acceleration is negligible and most often they are the same thing.
  9. shin25

    5% Critical Damping

    This has been in the seismic design code for sometime now. I believe, the value is selected from experience and testing based on material and structural elastic and post elastic behavior.
  10. shin25

    Analysis of an Industrial Building

    If this is a single story portal frame building, then either the base of the column or connection between the roof and columns can be considered pinned and designed as such, the other end should be considered fixed. The structure will be unstable if both ends are considered pinned. You may also...
  11. shin25

    5% Critical Damping

    Critical damping means that a system will not vibrate at all, on the other hand 0% damping means that the system will keep on vibrating without any reduction in the amplitude or frequency. 5% damping means that the damping is 5% of critical damping. 5% damping is low but still should reduce the...
  12. shin25

    Pseudo Spectral Acceleration

    I believe, it is the maximum spectral response of a damped single degree freedom system under a given ground acceleration history.
  13. shin25

    Ground Beam Design

    Your beam should be designed considering interaction of both bending and axial loads. You should use the load combinations from Chapter 2 and 12 (as applicable) of ASCE 7. Load combination specific load factors should be applied to bending and axial. Don't forget to add the vertical component...
  14. shin25

    Non Structural Components

    I believe your interpretation is correct. When failure of a non-essential component may damage an essential or structurally important part of the structure, the attachment for a non-essential component must be designed adequately per the code requirement. An example may be, if a non-essential...
  15. shin25

    UFC 3-310-04 Acceleration

    I believe, the short period acceleration, Sds that is included in UFC should match with that in ASCE 7. Therefore, you should be fine if you use Sds from ASCE. Component Importance factor (Ip) can also be taken from ASCE.
  16. shin25

    Separating Buildings

    If the buildings are connected, they should be analyzed as connected considering due torsional irregularity for seismic analysis. For certain type of irregularity, static seismic analysis is no longer valid, a dynamic analysis may be required. If the buildings are physically separated, they can...
  17. shin25

    Seismic Analysis Requirements in Areas with Low Seismic Activity

    The likely resolution would be to perform an elastic level seismic analysis using DLE and allow a 70% increase in allowable steel stress per API.
  18. shin25

    Stability, Bracing, and Moment Frames

    If possible, it may be wise not to mix different load resisting systems (moment frame and braced) in the same direction. Although, having moment frame system in one plan direction and braced frame in the orthogonal direction of the building should be fine. However, if different systems will...
  19. shin25

    Existing Concrete Columns - Confinement Ties

    If the lateral ties are truly needed for strength, then I may recommend to retrofit the columns with FRP wrap, etc to provide concrete confinement.
  20. shin25

    Achieving pin connection in concrete by rebar extension

    As Hokie said, it may not be desirable to detail an exterior beam to column connection with no top reinforcing or very little development length to act as pinned connection. Following should be kept in mind when deciding on such detail: 1. Will the connection see any load reversal due to...

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