Trusses

TRUSSES

Subject : Engineering mechanicsSubject Code : CE151Faculty : Mr. Rajmal JatDefinition of Engineering StructureAn engineering structure is any connected system of members built to support or transfer forces and to safely withstand the loads applied to it. e.g. Trusses, Frames and machines etc.

TRUSSES A framework composed of members joined at their ends to form a rigid structure is called a truss. e.g. Bridges, roof supports, derricks etc.Commonly used structural members are I-beam, Channel, angle and bars etc.Two types:- Plane truss (e.g. at Side of bridge) Space Truss (e.g. Mobile phone tower)

Bolted or welded connections are assumed to be pinned together. Forces acting at the member ends reduce to a single force and no couple. Only two-force members are considered.When forces tend to pull the member apart, it is in tension. When the forces tend to compress the member, it is in compression.Plane Trusses: These are the two dimensional structure of rigid bars as shown

Space Truss : These are three dimensional structures like mobile tower electricity towers.

Development of plane trusses

A rigid truss will not collapse under the application of a load.

A simple truss is constructed by successively adding two members and one connection to the basic triangular truss.Development of Space trusses

An elementary space truss consists of 6 members connected at 4 joints to form a tetrahedron.A simple space truss is formed and can be extended when 3 new members and 1 joint are added at the same time. Analysis of Plane Trusses Two Methods:Method of JointsMethod of sectionsSteps of Method of Joints: Step Ist : Computation of support reactions of truss Step IInd : Representation of forces either tensile or compressive in each member of the truss. Step IIIrd: Draw the free body diagram of the pin where more than two unknown forces are not present. Step IVth : repeat the step IIIrd to the subsequent joints till the forces at all the joints are computed.

Development of truss and Joint forcesTHANK YOU