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  1. ajh1

    Building/runway impacts for overhead cranes.

    A lot of this is based on the travel speed of a crane. If a crane is pendant operated or hand-geared it can only travel as fast as the operator can walk under it. Thus the impact forces are lower as there is less dynamic action. With a cab controlled or remote controlled crane, the crane...
  2. ajh1

    ANSI- A58.1-1982 Load Combinations (For Chicago)

    From A58.1-1982: ASD combinations: D D + L +(Lr or S or R) D + (W or E) D + L + (Lr or S or R) + (W or E) Load Combination Factors 0.75 for combinations including, in addition to D: L + (Lr or S or R) + (W or E) L + (Lr or S or R) + T (W or E ) + T 0.66 for combinations including, in addition...
  3. ajh1

    ASCE7-10

    A couple of sources you might check into: FM Global Data Sheets contain ASCE-related information for several countries outside of the US US DOD UFC documents contain information for US military bases around the world. If one is close to your site, you may be able to utilize those values...
  4. ajh1

    Snow Load - Sliding Snow

    What version of IBC 2009 are you looking at? My copy of the code shows only one paragraph for Section 1608.1 that simply says looks at Chapter 7 of ASCE 7. No figures, tables, charts, etc.
  5. ajh1

    Snow Load - Sliding Snow

    Canadian code requires a combination of both, but in their case the sliding snow is also a tapered load unlike the uniform load in ASCE.
  6. ajh1

    Snow Drift (Lower Roof)

    I saw pictures a few years ago of a scenario as you had described following a Buffalo, NY snowstorm that had dropped 7' overall on the city. The low area was probably on the order of 30' square and had basically filled to the brim with snow. I would agree with mssquared, put a higher roof on...
  7. ajh1

    ASCE 7-10, MWFRS Wall Loads on OPEN building?

    ASCE 7-10 Section 27.4.3 indicates that for walls that could be deemed "fascia panels", which I take to mean partial height walls suspended from the roof plane as opposed to running from ground to eave, should be considered as an inverted parapet, i.e., use parapet loadings with forces on both...
  8. ajh1

    Snow loads on a trough roof (butterfly truss)

    Yes, this falls under Section 7.6.3. I would consider it a folded plate structure (or valley structure) more than a sawtooth, but the same rules apply. Section 7.6.3 applies for greater than 3/8:12 slope (1.79 degrees) so your building falls into the requirement. In effect you have a drift...
  9. ajh1

    Load Combinations & Crane Loads

    Crane loads must be combined with snow loads and wind loads in exactly the same way that any other live load would be combined. IBC does provide some reduction in the combinations when you are working at the ASD level.
  10. ajh1

    ASCE 05 fig.6-10

    See my response over in the Structural Engineering forum thread507-271297.
  11. ajh1

    Moment Frame Classification

    Probably the best description of requirements is contained in AISC 341 (Seismic Provisions). Each frame type has a series of requirements such as width/thickness ratios that must be maintained. Obviously, the higher the allowed R factor, the tighter all of the rules are. IMF and SMF frames...
  12. ajh1

    Columns of A large roof-Effect of Snow load reducible?

    The other aspect of live load on a roof is that it is there primarily to accomodate the potential of maintenance workers on the roof, at least in a post-construction timeframe. There is a good likelihood of a few workers congregated in one area, say around a roof top unit, but it is highly...
  13. ajh1

    Special seismic load combinations

    I would agree that the code is not particularly clear on when you use these provisions, other than the example you cited. There are also some Em requirements in regard to collector elements. For steel design, the higher level seismic requirements get defined by the AISC Seismic Provisions...
  14. ajh1

    Wind Loads... Roll up Doors "open" or closed?

    As long as the doors themselves meet the same wind load/speed requirements of the building code as the building shell proper, the building would be classified as enclosed. If you think in terms of a "design event" for wind being typically 90 mph (most places in the US), most owners would know...
  15. ajh1

    ASCE 7 Wind Loads on Open Structures

    The new ASCE7-05 has a much enhanced section on open coefficients, both MWFRS and components and cladding. The new charts cover monoslope, gable with ridge, and inverted gable with valley. They are still rather silent on what to do with elements of the building other than the roof surface that...
  16. ajh1

    Do we consider windows and doors as "openings" in any special cases?

    Not as long as the window, door, whatever is designed to meet the same wind resistances as required for the building proper (adjusted for tributary areas, etc.) Coastal Florida and some other areas take that limitation a bit farther, but in general a window is NOT an opening when designed properly.
  17. ajh1

    ASCE 7-02 Snow Sliding

    The last sentence in Section 7.9 clearly states: "Sliding loads shall be superimposed on the balanced snow load." There is no mention of drifting snow in that paragraph.
  18. ajh1

    ASCE 7-02 Wind Loads - definition for enclosed structure

    I would agree with you. "Enclosed" is a catch-all anytime that "open" and "partially enclosed" are not met. The best example is of a building where both sidewalls are completely sheeted and both endwalls are completely open. Checking the conditions: "Open" - each wall at least 80% open -...
  19. ajh1

    WInd Loads for h < 60 ft

    The definition does not distinguish between dimension parallel to wind and dimension perpendicular to wind, it simply says least horizontal dimension. Realistically I doubt there is that much difference in actual loads between 6.5.12.2.1 and 6.5.12.2.2. I would probably use 6.5.12.2.1 for both...
  20. ajh1

    WInd Loads for h < 60 ft

    Your eave height exceeds the least horizontal dimension so you do not qualify for the low-rise provisions (definition in 6.2). That means you fall under either 6.5.12.2.1 or 6.5.12.2.3 (not 6.5.12.2.2). You are permitted to use the normal wind provisions, rather than the low-rise provisions...

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