Question

Determine the forces in members DE, GN, and MS of the pin-connected truss in Fig. 10,000 lb 7 at 10.70

Answer 1

Solution 10! 10! 10! 10! 10 y 10000 lb IB C D E F G NIP Support Reaction Calculation Taking Moment about Rj Considering 2 (10000x30) - (Rgx 20) = 0 Rg = 15000 lb (1) Fy=0; -10000 + Rg - RR=0 RR = 15000 10000 RR = 5000 lb (1) We have to find forces in member DE, GN and Ms so, regarding this we will make an assumption. We will assume that all the forces are in Tension so that the direction of all forces will be away from joints. Now if positive result comes out then our assumption is okay cie Tension. else the opposite of our initial assumption should be taken under considerations de Compression,

Member forece in De Calculation In that case; We will take section - and considering Right portion of the section. F-B.D н N tanda logo Ostan" (1) 'KL 0=450 FuL L M gse ber + 5000 lb 15000 lb 4 10 T01 10 100 1 Taking Moment about L; Considering 26 (FDX 10) - (1500oxlo) – (5000x10) = 0 FCD = 20000 lb Considerine Joint Di preaning FB.D FDE DL If = 0; -FotFDE =0 DE = Fep TE = 20000 lb (te

Member Force in GN Calculation. In that case; We will take the section and considering teight of the section. ③ - ② portion FFG G Ecoso *-- Fur ENp I 101 Here if we take Fy=0; we can see only E sino is working as a vertical force Therefore we can write; { Fy = Fansino =0 Fan = 0 (zero force member) Member force in MS calculation At first considering support S. Efy=0; - Drawing F.B.D FLassina FLo sino + 15000=0 Free - 15000 sinus open--Fig cose [fx=0; Facet FLUCOSE=0 15000 Es g = - FL g cosa

Fog - - (- 15000) cosys R Face= 15000 lb Now considering Support Dreawing F.B.D. Fx=0; - FRS=0 FRS=0 4 Fur MP FRS + 5000 lb Now considering Joint s Preawing F.BD ZF z = 0; we get - Esg & Frs + FM Cosa=0 & Fris sine FM SCOSO = Fs-FRS F px Fus FMs = 15000-0 so s FAS Friscose Cos 450 FMS = 21213.203 lb (Tension (Answer)