6.12 : Frames

Frames are essential components of various mechanical and structural systems used daily. These structures are known for their stability and ability to bear heavy loads. A frame is constructed using two-force and multi-force members, interconnected using pin joints. In contrast, trusses are made entirely of two-force members.

Frames are versatile and widely used in various applications such as structural supports for beams and columns, automobile chassis construction, and in the construction industry for equipment such as cranes and excavators.

Analyzing a frame involves understanding the forces applied to each structure member. For example, consider the scenario of a crane lifting a load W. A free-body diagram is drawn to determine the external forces acting on the crane. Then, each member of the crane is analyzed separately to identify known and unknown forces.

Initially, two-force members are analyzed to determine the forces acting at each end of the member. Next, the forces acting at each connecting point of multi-force members are determined. Through this analysis, the forces present in all structure members can be determined, allowing for proper design and safe operation.