TB-Lecture08-ASCE-7-Wind-Method-2

TB-Lecture08-ASCE-7-Wind-Method-2 - EGN-5439 The Design of...

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© L. Prieto-Portar - 2008 EGN EGN -5439 The Design of Tall Buildings 5439 The Design of Tall Buildings Lecture 08 Lecture 08 ASCE 7 ASCE 7 - - 02 Solved Problem #1: 02 Solved Problem #1: Analytical Method 2 (for buildings < 60 feet high). Analytical Method 2 (for buildings < 60 feet high).
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This lecture applies the ASCE 7-02 code requirements for wind (Section 6.0) to a simple structure and analyzes it with, The ASCE 7-02 Method 2 , the Analytical Method for buildings smaller than 60 feet in height. The structure chosen is a warehouse-office building in downtown Tampa . Its dimensions are 100 feet long by 50 feet wide by 20 feet tall. A drawing is shown on slide #3 depicting the location of all the windows and doors. The location of these windows and doors are either in the field (or internal) zones or in the end (or external) zones. The analysis consists of finding all pressures affecting every part of this structure that come from all four directions. Finally, when all the pressures have been calculated, the engineer will choose the largest positive pressure and the largest negative pressure for the design of the building.
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The example: a single-story warehouse building, 100 feet long, 50 feet and 20 feet tall.
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The location of the windows and doors are critical: are they in the “field” or in the “end” zones; are they “debris resistant” or not, in which case, this face of the building is breached during a hurricane.
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The basic formula used to compute the wind design pressure p that is applied to a structure or a portion of a structure is, The wind velocity comes from County maps in lieu of Fig 6-1b pg 73 This formula is performed upon 10 different zones of the structure in 4 different wind directions for both the transverse and the building’s longitudinal directions. The analysis is also performed for both the MWFRS and C&C. Therefore, there are a total of 160 calculated pressures. From these, the engineer will choose the largest positive and negative pressures for the final design. ( ) ( ) ( ) 2 0 00256 z zt d p pi p . K K K V I GC GC ± = - ² ³ A constant / Table 6-3 pg 75 / Figure 6-4 pg 47+48 / Table 6-4 pg 76 / Table 6-1 pg 73 A constant = 0.85 or Equation 6-4 pg 30 / Fig 6-6 to 6-8 pg 50-53 / Fig 6-5 pg 49 ( ) ( ) ± = - ² ³ z p pi where p q GC GC
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( ) ( ) 2 0 00256 = zt z d p . K K V I f K actor The wind exposure category coefficient Kz shall be taken from ASCE 7-02, Section 6, page 75, Table 6-3. The Exposure Category is discussed in ASCE 6.5.6, pages 28 and 29. 6.5.6 Exposure. For each wind direction considered, an exposure category that adequately reflects the characteristics of ground roughness and surface irregularities shall be determined for the site at which the building or structure is to be constructed. Account shall be taken of variations in ground surface roughness that arises from natural topography and vegetation as well as constructed features.
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6.5.6.1 Wind Directions and Sectors. For each selected wind direction at which the wind
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This note was uploaded on 08/29/2011 for the course CES 4600 taught by Professor Staff during the Fall '08 term at FIU.

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TB-Lecture08-ASCE-7-Wind-Method-2 - EGN-5439 The Design of...

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