HW 4 Solutions Wind Loads.pdf - CVEEN 3210 Fall 2016 Solutions HW 4 Problem I Compute the design wind pressures on the following steel building for the

HW 4 Solutions Wind Loads.pdf - CVEEN 3210 Fall 2016...

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CVEEN 3210, Fall 2016 Solutions HW # 4 1 Problem I. Compute the design wind pressures on the following steel building for the wind direction shown in the figure for all walls and roof, according to ASCE 7 10. Assume the following: a. The penthouse is a rigid structure. b. The building is located on an open terrain in one SLC, UT suburb. c. It is an enclosed building. d. The building is in a flat terrain. SOLUTION: The penthouse is located in SLC, UT. The building is considered Category II (Table 1.5-1), and from Figure 26.5-1A, the wind speed is 115 mph. The building is in a flat terrain and, therefore, the topographic factor, ܭ ௭௧ = 1. Load combinations will be computed. Thus, the wind direction factor for a building is ܭ = 0.85, according to ASCE Table 26.6-1. Then, the static wind pressure is modified by several factors to obtain ݍ , at a height ݖ : ݍ ൌ 0.00256ܭ ܭ ௭௧ ܭ ܸ ൌ 0.00256ܭ ሺ1.0ሻሺ0.85ሻሺ115ሻ ൌ 28.78ܭ ሺ݌ݏ݂ሻ To compute ݍ as a function of the height, we take into account that the building is in open terrain . Thus, the Exposure Category is C, and based on ASCE Table 27.3-1: Height (ft) (Cat. B) (psf) 0-15 0.85 24.46 15-20 0.90 25.90 20-25 0.94 27.05 25-30 0.98 28.20 30-40 1.04 29.93
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CVEEN 3210, Fall 2016 Solutions HW # 4 2 For the wind pressure at the mean roof height ( ݍ ), we need to consider that the height is ݄ = 40 ft. Thus, by linearly interpolating we find that ܭ = 1.04, and that ݍ ൌ ݍ ௛,ସ଴௙௧ = 29.93 psf. Once the ݍ and ݍ values have been computed, we can get the design wind pressures based on the equation: ݌ ൌ ݍܩܥ െ ݍ ሺܩܥ ௣௜ Because the building can be considered enclosed, ܩܥ ௣௜ 0.18 (Table 26.11-1). Also, the structure is assumed to be a rigid building, and the gust factor can be taken as ܩ = 0.85. Then, the equation can be expressed as: ݌ ൌ ݍሺ0.85ሻܥ െ 29.93ሺേ0.18ሻ ൌ 0.85ݍܥ ∓ 5.39 psf The pressures at different surfaces are: Windward Wall This is the only surface in which ݍ ൌ ݍ . Also, based on ASCE Table 27.4-1, ܥ = 0.8. ݌ ௪,଴ିଵହ ൌ 0.85ݍܥ ∓ 8.5 ൌ 0.85ሺ24.46 ݌ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݌ݏ݂ ൌ ૚૟. ૟૜ ∓ ૞. ૜ૢ ݌ݏ݂ ݌ ௪,ଵହିଶ଴ ൌ 0.85ሺ25.90 ݌ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݌ݏ݂ ൌ ૚ૠ. ૟૚ ∓ ૞. ૜ૢ ݌ݏ݂ ݌ ௪,ଶ଴ିଶହ ൌ 0.85ሺ27.05 ݌ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݌ݏ݂ ൌ ૚ૡ. ૜ૢ ∓ ૞. ૜ૢ ݌ݏ݂ ݌ ௪,ଶହିଷ଴ ൌ 0.85ሺ28.20 ݌ݏ݂ሻሺ0.8ሻ ∓ 5.39 ݌ݏ݂ ൌ ૚ૢ. ૚ૡ ∓ ૞. ૜ૢ ݌ݏ݂
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