Question

3. Use method of Section and determine the force in member GF and GD of the truss. State whether the members are in tension or compression. The reactions at the supports have been calculated. (Lec/Tute a half) 45 m m 40 B с D A, EN 6 kN 8 kN 2 EN E-7AN

Answer 1

G Ja; a 9 H f 4.5m < 3M LA Ax=0 E Ath B A 6KN 8 KN 21N Ay= 9 KN Ey= - FIN x 3m 14 3m L 3m 43m I] Angle calculations tan o = OD OG 4.5m 3m O o- tani - 10-56.309 tanat of 4.5-3 OG 3 -1 d = tant x = 26.570

2] Method of sects (a-a) from left G ola 9 A for FGD 4.5m Н. A FED B gen GKN 9 KN 8 KN. x 3m 3m a) EMG=0 9x6 - 6x3 Fox 4.5=0 FCD = 8 KN b) 2 V=0> 9 - 6 - 8 - For sind FGD sino = 0 0.45 For +0.832 FGD - 5 IP (c) € H=0 => Fco & FGF cosa t fod Coso=0 0.8943 Forr +0.555 Ford - 8

solving eq" & 2 We get → FGE= - 8.734 KN FGD = -1.285 KN 3) Final Answers Note: - of the direction of force Negative sign en above analysis shows that force is compressive, because is towards towards the node its member force is compressive .. Member Member force (KN) 8. 734 Nature of force GF compression GD 1.285 compression