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SEAW Wind Commentary Slides


SEAW Wind Commentary Slides


This album contains the slides from Bill Mooseker's presentation at the ASCE Conference in Seattle.    I've changed the slides to a basic black and white layout to be more printer friendly.  Click on the thumbnails to get a larger image to view or save to your hard drive. The default size is 800 X 600 but larger sizes are available (originals are about 1600 X 1200).
-Cascade Bill


Date(s): May 31, 2003. Album by Cascade Bill. 1 - 24 of 78 Total. 5516 Visits.
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01method

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02method

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03method

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04method

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05netpressure
This slide shows that the end zone pressure can be represented as a "net" pressure equal to the "End Zone" pressure minus the "Interior zone" pressure.  I find this easier than to use two partial loadings.

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06inclined
For ASCE-7 Methods 2a & 2b, wind pressures are applied normal to the surface.  However it is convienent (to get shears and overturning moments on a shear wall for instance) sometimes to transform the normal pressure into horizontal and vertical components.  This graph shows that the magnitude of these components is the same as the normal pressure but applied to the horizontal or vertical projected area.

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07exp2-01
Note: the roof slope of this problem has been set at less than 10 degrees so that the ASCE Method 1 (Simplified Procedure) may be used.  When the Wind Commentary is published, refer to Problem 1 which is almost identical but has a steeper roof slope

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08exp2plan

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09exp2endelev

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10ibcbsd
(ASCE-7 Simplified Method calls this a "Simple Diaphragm Building" which seems to make better semantic sense.

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11ibcsimp2

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12aibcsw
For the IBC Simplified Method there are two possible loading conditions for each side of the building, one with the "End Zone" located on the left and the other with it on the right.  Fortunately for a symmetric rectangular structure, only two need to be considered - those parallel to each of the major axes.

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12ibcse
(Note: Windward wall is actually the South Wall)

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15ibcwn
One of my pet gripes with the IBC method is that their tables refer to direction as transverse and longitudinal.  These distinctions lose their meaning as each side is considered as a "windward" face.  Note that the column for "longidutinal" pressures is identical to the "transverse" column for a 0 degree roof angle.

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16ibcvv120
Another gripe that I have with the IBC is that they give numerous tables of pressures with values for different wind speeds.  These are not necessary since wind pressures are proportional to the ratio of the velocity squared.  In my example I use the values for V=120mph and then multiply those pressures by the ratio of the square of the wind speeds to get values for other wind speeds.

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18ibcxls02a
I've used the values for Horizontal and vertical pressures vs roof angle based on a 120mph wind speed.  Using the "vlookup" and "index" functions, values for any roof angle can be found by interpolation.  For this example the values for roof angles of 5 degrees and 10 degrees are used.  The values for Height and Exposure adjustment are also tabulated.

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17ibcxls01
Typical spreadsheet for use with the IBC Simplified Method.  Values in "red" are variables input by the user. Interpolation of values is shown.

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19ibcxls03
Calculation of "Net" end zone pressures.  Yellow highlighted rows show that the windward roof has negative (outwards) pressures.  These are to be disregarded per a footnote to the the table.  These pressures are for a building with h = 30' located in an Exposure B site.

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20ibcxls04
The pressures in the preceding table are now multiplied by the "height and exposure" factor.

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21ibcxls05
This shows the calculation of loads, shears, and overturning moment for the end wall of the building.

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22ibcresults
Graphical summary of the wind loads, shears, and moments using the IBC method.  Note loads are expressed as a net horizontal and vertical force.

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