SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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60 Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 = 0.20 for L h /t ≥ 170 = use linear interpolation for 150 < L h /t < 170 L h = vertical leg dimension of the angle T = design thickness For LRFD, the design moment capacity for uplift shall be determined as follows: M u = ΦM nu Φ = 0.80 (Eq. B3.1.3-4) M ng = (2)(0.8564)(33,000) = 56,522 in-lb (for two angles) L h /t = 8.0/0.0566 = 141.34 ≤ 150, Therefore, R = 0.25 M nu = 0.25(56,522) = 14,130 in-lb 2 wL Φ M = 8 E7 Head Track Design ΦM L = 8 w 8(0.8)(14,130) L = = 15’-6” 31 12 Calculate the maximum allowable span for a 350T125-33 head track for an opening in a building subjected to 120 mph Exposure Category C wind speed. 4’ Head Track 8’ Opening L E7.1 Design Loads and Assumptions Wind Load = 37.7 psf (Table C2.2, 120 mph Exposure Category C wind speed) Deflection Limit = L/240 End Bearing Length = 6” (so bearing does not control) 8’ high walls
Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 61 E7.2 Design Capacity Head track spans are calculated using the AISIWIN– V4.0 computer program. The following is a sample output. SECTION <strong>DESIGN</strong>ATION: 350S125-33 INPUT PROPERTIES: Web Height = 3.646 in Top Flange = 1.250 in Bottom Flange = 1.250 in <strong>Steel</strong> Thickness = 0.0346 in Inside Corner Radius = 0.0764 in Yield Stress, F y = 33.0 ksi F y with Cold-Work, F ya = 33.0 ksi INPUT PARAMETERS Nominal Load = 37.7 psf Deflection Limit = L/240 Load Factor = 1.6 Bearing Length for Web Crippling= 6 in ALLOWABLE SPANS – SIMPLE SPAN TRIBUTARY HEAD TRACK BRACING AT: AREA NONE MID Pt THIRD Pt 48.0 in 3’ 5” 3’ 8” 3’ 8” E8 Shear Wall Design (General) The design of the lateral force resisting systems (LFRS) of light-frame buildings generally follows one of three methods: Tributary Area Approach (Flexible Diaphragm); Total Shear Approach (Eyeball Method); and Relative Stiffness Design Approach (Rigid Diaphragms). Each differs in its approach to distributing whole-building lateral forces through the horizontal diaphragms to the shear walls. Each varies in the level of calculation, precision, and dependence on designer judgment. While different solutions can be obtained for the same design by using the different methods, one approach is not necessarily preferred to another. All may be used for the distribution of seismic and wind loads to the shear walls in a building. However, some of the most recent building codes may place limitations or preferences on certain methods. In developing the shear wall tables for the Prescriptive Method the Tributary Area Approach, as described below, is used. The tributary area approach is perhaps the most popular method used to distribute lateral building loads. Tributary areas based on building geometry are assigned to various components of the LFRS to determine the wind or seismic loads on building components (i.e., shear walls and diaphragms). The method assumes that a diaphragm is relatively flexible in comparison to the shear walls (i.e., a “flexible diaphragm”) such that it distributes forces according to tributary areas rather than according to the stiffness of the supporting shear walls. This hypothetical condition is analogous to conventional beam theory, which assumes rigid supports as illustrated in Figure G1.1 for a continuous horizontal diaphragm (i.e., floor) with three supports (i.e., shear walls).
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SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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