Trusses Method of Joints
Engr . Saeed A Maitlo
Lecturer
Institute Of Biomedical Technology ,LUMHS
Jmashoro.
What is a truss.
A truss is an assembly of linear members connected
together to form a triangle or triangles that convert
all external forces into axial compression or tension
in its members.

A rigid framework, as of wooden beams or metal
bars, designed to support a structure, such as a roof.
Method of Joints
 If a truss is in equilibrium, then each of its joints
must also be in equilibrium
 The method of joints consists of satisfying the
equilibrium conditions for the forces exerted “on
the pin” at each joint of the truss
Method of Joints
 If a truss is in equilibrium, then each of its joints must be
in equilibrium.
 The method of joints consists of satisfying the
equilibrium equations for forces acting on each joint.
∑ Fx = 0
∑Fy = 0
Method of Joints
 Recall, that the line of action of a force acting on a joint
is determined by the geometry of the truss member.
 The line of action is formed by connecting the two ends
of each member with a straight line.
 Since direction of the force is known, the remaining
unknown is the magnitude of the force.
Joint A
Joint B
Tension Force
Joint B
Joint A
Compression Force
Method of Joints
Upper Cord members
Verticals
Diagonals
Lower Cord Members
Method of Joints
Gusset Plate
Weld
Idealized joint –
members connected
by a frictionless pin
Method of Joints
Upper chord in compression
Lower chord in tension
This is a Pratt truss
Upper chord in compression
Lower chord in tension
This is a Howe truss