Trusses

Question	Answer
Definition: Rigid structure made of many bars or beams joined at ends	Rigidity and strength comes from arranging bars in multiple triangles. other shapes distort easily
Assumptions: -Members are joined with smooth pins (hinges) -Bars have a joint at each end ONLY -Loads applied at joints	-Weights of members negligable -2D arrangements only
-Therefore, every member is a two-force member. Only forces at pinon ends acting. -Forces act along bar -Inwards (compression) -Outwards (tension)	Struts (compression) need to be stronger than ties (tension) as there is no tendency for ties to bend
Whole truss: Look at truss as single rigid body and analyse external forces. Applied loads know Find reactions at supports	Method of Joints: To find forces in member, split them up with each bar and pin separate
Method of Joints: All internal forces are NIII pairs between member and pin.	-Members are 2-forces members and so direction depends on angle of bar -Draw forces as TENSION forces so negative answer = compression
Each internal force occurs 4 times. Draw them! 2 on one pin NIII 2 on one bar, at each end	Pin forces are concurrent! Two resolving equations for each pin. In the X and Y direction
On a fixed support, there are x and y reaction components	Rolliing support. There are only reactions in directions opposite to direction of rolling

Resource summary

	Created by nataliemangondo about 12 years ago