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Moment frames

Discussion in 'Residential Seismic' started by zigmark, Jun 24, 2014.

  1. zigmark

    zigmark Silver Member

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    I am looking for some feedback regarding steel moment frames. In 15 years I have not had a residential plan come in with anything other than a "preapproved"(Simpson) moment frame. I now have someone proposing to have a local shop fab up a moment frame. I am hoping some of you can help me with standards for the design and construction of this system. I am aware that the steel is required to be ASTM A992 grade 50 for shapes and plates. I am aware of the structural welding requirements of AWS D1.1. What else should I be looking for? All help appreciated.

    ZIG
     
  2. steveray

    steveray Sawhorse

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    An engineers stamp.......
     
  3. MASSDRIVER

    MASSDRIVER Sawhorse

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    Special inspection requirements, certified welders. I've done dozens of them, and there is nothing really special other than residential guys may be unfamiliar with the process or the unfamiliar trades.

    Generally, depending on size, the components with backing plates and whatnot are made in the shop, then assembled on site.

    The welder generally schedules his own inspections, as he knows his layout and time frame. Provisions need to be made for fastening of lumber the frame, and my preferred method are welded-on studs. Some guys pin the lumber with powder actuated tools.

    That's the perspective of the builder if it helps.

    Brent.
     
  4. zigmark

    zigmark Silver Member

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    Engineering!! well that just blows the project budget....

    Ok, so I found this: www.nehrp.gov/pdf/nistgcr9-917-3.pdf. It is a little dated but it's a start. I've found a few others as well.

    I see they have prequalified connections with limits of applicability, I didn't see any for welded connections however.

    Thanks,

    ZIG
     
  5. zigmark

    zigmark Silver Member

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    Ok here is what I am down to regarding the moment frames.

    Seismic Zone "D" and 3-story light framed construction.

    What are the limitations of using an Ordinary Moment Frame in this condition? Specifically, how are the connections determined and configured?

    Proposal is face welded beams to upright columns with full pen welds. How practical is this?

    Thanks again,

    ZIG
     
  6. Mark K

    Mark K Platinum Member

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    The building code has provisions for steel moment frames. They need to be engineered. The plan checker needs to be an engineer.

    I believe you will find that the Simpson frames were designed to comply with the code provisions. Licensing laws do not eliminate the need for an professional engineers seal and signature just because there is an evaluation report. Thus the moment frames either custom designed or provided by Simpson should be Stamped and signed by a professional engineer.
     
  7. Mark K

    Mark K Platinum Member

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    The NEHRP report listed is not code. An engineer should know the particular code requirements.
     
  8. TheCommish

    TheCommish Sawhorse

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    Zig,

    regardless of the moment frame, a three story building in a D seismic zone would require engineering anyway. I would suggest your budget if blown was not realistic.
     
  9. Phil

    Phil Sawhorse

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    To give you an idea why an engineer is required, there are many standards can apply to a moment frame in SDC D, and interpreting them typically requires an engineering background :

    IBC

    ASCE 7 Minimum Design Loads for Buildings and other Structures

    AISC 360 Specifications for Steel Buildings

    AISC 341 Seismic Provisions for Structural Steel Buildings

    AISC 358 Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications

    AWS D1,.1 Structural Welding Code - Steel

    AWS D1.8 Structural Welding Code Seismic Supplement (may be required for 2012 IBC)

    RCSC Specification for Structural Joints Using High Strength Bolts (for 2009 IBC and earlier this was 'Using ASTM A325 or A490 Bolts')

    ACI 318 Building Code Requirements for Structural Concrete (needed for anchor bolt design)

    An ordinary moment frame may be permissible if the structure's height is not over 35', the floor and roof dead load are less than or equal to 35 psf, and the walls weight does not exceed 20 psf

    The AISC specification can be downloaded at https://www.aisc.org/content.aspx?id=2884
     
  10. richardsmyth

    richardsmyth Member

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    Today steel moment frames is a better residential option as they are pre-engineered, pre-fabricated and cost-effective, also its installation is fast which is performed by standard framing crew and not welders.
     

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