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Figure $4$ shows a general plan of a $(90ft250ft)$ 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 $25$ ft $.$ 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 $($i$.$e$.,$ roof cladding and bracing$)=5psf$

Weight of I$-$shape Purlin $=14l\frac{b}{f}t$

Weight of C$-$shape Purlin $=8l\frac{b}{f}t$

Truss members own weight $=20l\frac{b}{f}t($to be applied to the system as concentrated loads at the joints of the upper chord$)$

Roof Live Loads: As provided by the ASCE$7-10$ standards for pitched roofs.

Present detailed calculations and the corresponding sketches for the following cases of loading:

The dead loads acting on an internal $($I$-$shape$)$ purlin.

The dead loads acting on an external $($C$-$shape$)$ purlin.

The dead loads acting on a typical $($internal$)$ truss.

The live loads acting on a typical $($internal$)$ truss.

Figure $4$