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  • Users: WAstruc10
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  1. WAstruc10

    Grade beam seismic hoops - overkill?

    For SDC of D, looking at ACI 318-14 section 18.13.3.4: "Grade beams and beams that are part of a mat foundation subjected to flexure from columns that are part of the seismic-force-resisting system shall be in accordance with 18.6." My situation requires large grade beams NOT spanning between...
  2. WAstruc10

    Liquefiable Soils - Where Is The "Base" of the Structure?

    I am designing a large but lightweight one-story steel building, similar to a PEMB. The foundation system is augercast piles due to liquefiable (seismic) soil conditions. The slab-on-grade is considered sacrificial and non-structural (so if the subgrade settles 7 inches during liquefaction, the...
  3. WAstruc10

    Hole Size in Steel for Post-Installed Anchors

    Though AISC requires +1/16" oversized holes for bolts, shop drawings for weldments (angle ledgers, etc) being attached to concrete with post-installed anchors often come back with +1/8" or +3/16" oversized holes proposed, presumedly so they'll have more tolerance for installation. Are +1/16"...
  4. WAstruc10

    Brick Veneer at Exterior Canopy

    I'm designing a cantilevered (steel HSS) column freestanding canopy. The architect now wants the steel columns surrounded by a wrap of brick veneer, with air gap. We're in seismic SDC=D here. First thought would be to provide veneer anchors to the sides of the HSS column. However, it would be a...
  5. WAstruc10

    Unusual Platform Framing Scheme

    I am working on a mixed-use project that is pretty typical for the pacific northwest...3 or 4 stories of wood-framed apartments platform framed over two stories of post-tensioned concrete flat plates (for parking & retail). However, the owner and contractor think it might save them some money to...
  6. WAstruc10

    "Micropile" minimum diameter

    Small diameter steel pipe piles (2 to 6 inch nominal) are fairly common in our region. I have always heard these referred to as "micropiles". However, just noticed 2012 IBC section 1810.3.5.3.2 limits minimum pipe diamter to 8", followed by an exception "There is no minimum diameter for steel...
  7. WAstruc10

    Wood Post - Holdown Shim Fastening

    Let's say we have a shearwall endpost holdown which utilizes SDS screws, but it's installed misaligned by one stud's width, so a short piece of 2x6 shim is needed to fill the gap. Do you think it would be acceptable to simply lengthen the SDS screws by 1.5" and assume that the shim is now acting...
  8. WAstruc10

    Holdown Shim Fastening

    When a shearwall endpost holdown which utilizes SDS screws is misaligned by one stud's width, so a short piece of 2x6 shim is needed, do you think it would be acceptable to simply lengthen the SDS screws by 1.5" and assume that the shim is now acting as an integral part of the endpost? Or do I...
  9. WAstruc10

    Subdiaphragm in light-framed wood building??

    I certainly understand the ASCE 7-05 Section 12.11 requirements for wall anchorage and subdiaphragms when it's a concrete or masonry wall tied into my floor. But what about light-framed wood wall structures...it seems like there is no exception to 12.11.2.2.3, so when I have exterior studwalls...
  10. WAstruc10

    Diaphragm Cross-Ties

    For retrofit of an existing URM building with wood joist floors, my understanding from ASCE/SEI 31-03 is that the joists must form continuous cross-ties from one wall anchorage to the opposite side wall anchorage (in the absence of subdiaphragms). Pretty straight forward. But what about the...
  11. WAstruc10

    Spiral Reinforcing in Seismic Pile

    I have a fixed pier in a high seismic zone, for which the geotech has specified 16" square prestressed piles. For the spiral reinforcing, I need 2" cover (marine environment) so I am left with a core diameter (Dc) of 12". Works fine with equation 21-2 (ps=0.12f'c/fyt), which calculates to #3...
  12. WAstruc10

    Tilt-up hooked dowels

    For tilt-up wall panels (especially 5.5" ones), how would you typically provide hooked dowels to the slab pour strip (or to a concrete mezzanine floor if needs be), since the hook development length is too long? It seems like a commonly overlooked error - even the TCA engineering manual shows...
  13. WAstruc10

    Cantilever Beam Bracing

    I've got a situation that doesn't seem to fit traditional AISC theory too well...essentially a horizontal "ladder" shape made out of MC18 channels as the primary stringers (ie. the legs of the ladder) spaced about 36" apart, with C6 channel cross members (ie. "rungs" of the ladder) welded to...
  14. WAstruc10

    Seismic load on conveyor truss?

    OK, ASCE 7-05 is giving me a headache again. I need to determine seismic loads on a steel box truss (single angle chords at 4 corners, single angle side verticals and diagonals, single angle diagonal "wind" bracing between top chords & sim between bottom chords). This truss is used in an...
  15. WAstruc10

    Force on Weir

    For a "sutro" (or proportional) weir, how do you calculate the force on the weir "blades"? This is an outlet for a small lake, into a channel. Is it simply the hydrostatic force, assuming the water is flowing pretty slowly on the high side, or are there significant "nozzle" type or other...
  16. WAstruc10

    Vehicle barrier load

    Section 1607.7.3 of the 2003 IBC requires a 6000# horizontal load (due to vehicle impact) applied on a 1.0 square foot area. I have a parking garage situation with CMU infill wall along part of the edge, which must be designed for this load. My question is, how wide of a "design strip" would...
  17. WAstruc10

    Building Separation

    Per IBC 2003 Sec. 1620.4.5, SRSS method is used to check separation of adjacent structures, to avoid seismic pounding. I have a new building being constructed next to an existing URM building, and no plans are available of the existing... does anyone have advice on how to rationalize a...
  18. WAstruc10

    Timber beam bracing

    I have a cantilevered PSL 7x20 beam, supported at two locations by PSL 7x7 columns. The problem is that my first support (not at cantilever) has lateral bracing but the support at the beginning of the cantilever has no bottom chord bracing, and cannot due to architectural constraints. Also...
  19. WAstruc10

    Waffle Surface Problem in PS Conrete Beam

    I have a weird concrete problem that I have never seen before; any advice or thoughts would be appreciated. It is a prestressed, large (2'-6"deep, 6'-0"wide, 20' long) concrete beam, simple span (so PS strands towards bottom), longitudinal mild reinforcing towards top, #5 full...
  20. WAstruc10

    Masonry Shearwall "Rw"

    For design of reinforced masonry shearwalls, UBC97 Sec. 2108.2.5.6 references "Rw" = 1.5. What is this? A remnant from the 94 UBC? It is not listed as a variable, as far as I have seen. How should one apply it to boundary member design? Regards,

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