Figure 4 shows a general plan of a (90ft x 250 fi) construction site of an indus
ID: 1885330 • Letter: F
Question
Figure 4 shows a general plan of a (90ft x 250 fi) construction site of an industrial building. Section 1-1 shows a front view of a typical (internal) unit of the industrial building. As shown in the figure the main supporting elements are N-trusses that are spaced at 25 fi. The dimensions of a typical (internal) truss unit are shown in Fig. 4 below. For ease of erection, all purlins are assumed to be made of simply supported units having 25 ft span each. The roof is covered by metal cladding sheets with the following loads to be considered in the design: Dead Loads: Roof Weight.e., roof cladding and bracing) - 5 psf Weight of I-shape Purlin- 14 lb/ft Weight of C-shape Purlin -8 lb/ft Truss members own weight 20 b/ft (to be applied to the system as concentrated loads at the joints of the upper chord) Roof Live Loads: As provided by the ASCE7-10 standards for pitched roofs Present detailed calculations and the corresponding sketches for the following cases of loading 1. The dead loads acting on an internal (I-shape) purlin. 2. The dead loads acting on an external (C-shape) purlin. 3. The dead loads acting on a typical (internal) truss 4. The live loads acting on a typical (internal) truss. Purlin Roof Cladding External Truss Internal Truss 5 ft urlins 250 ft 20 ft 10panels x 9 ft = 90 ft Section 1-1 90 ftExplanation / Answer
1. Dead load on internal I section,
Considering 5 panels on either side of truss, having total length of 45 ft, Each panel has a length of 9 ft.
Inclined Angle = tan inverse of (5/45) = 6.34 degrees,
Inclined length on either side of truess = Sqrt (5^2 + 45^2) = 45.28 ft.
Length of each panel = 9.055 ft.
This length of panel has to be multiplied by roof dead load to arrive at uniformly distrubuted load (UDL) on the Internal I perlin, = 9*5 = 45 lb/ft,
Dead load of perlin = 14 lb/ft.
Hence, total UDL = 14 + 45 = 59 lb/ft.
Concentrated point load acting on the individual Internal Purlin on the truss due to self weight of Truss = 20 * 45/5 = 180 lb (Ating on top chord members only) (Note that 45 ft is the length of truss on either side and there are net 5purlins supporiting the roof)
Concentrated Dead load on truss due to purlins = 59 * 25/2 = 737.5 Lb. (Note that spacing of truss in plan is 25 ft.) , Reaction at supports = w.l / 2
Total Dead Load acting on Internal joint of truss on top chord members = 737.5+180 = 917.5 Lb.
2. Dead load acting on C purlin will be half of ans 1.
Thus, ans = 59/2 = 29.5 lb/ft.
3. Combined ans of 1 and 2.
At edge Total load acting on C purlin = 458.75 lb
At Internal I purlin Total Dead Load at joint = 917.5 Lb
4. For live load calculations provision under ASCE7-10 standard must be provided for pitched roof.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.