Stiffness Method 

Introduction





Truss
Stiffness Matrix


Fig. 2 Truss element for stiffness matrix 
Where 

Frame
Stiffness Matrix


Fig. 3 Plane frame element 


(2) 

Where A = Cross section area of the element E = Elasticity modulus I = Moment of inertia L = Length of the element C = cos(q) S = sin(q) k = Element stiffness method 

Assembling
the Stiffness Matrices and Force Matrices


Where Similarly, the force can be assembled as following: Where 

Formulation
of a System of Equations


To determine the displacements, the boundary conditions are imposed and the following equation is solved.
Where 