6.12:
Frames
Frames are generally rigid, stationary structures often consisting of pin-connected members to form a stabilized system to support externally applied loads.
Trusses are made of two-force members that withstand axial forces like tension and compression, operating along the axis of their members.
In comparison, frames are composed of two-force members and at least one multi-force member, which is acted upon by three or more forces.
They are widely used as structural support in beams and columns of buildings, chassis in automobiles, and construction equipment like cranes and excavators.
To analyze a frame, consider an example of a crane in equilibrium lifting a load W.
A free-body diagram of the crane is drawn to determine the external forces acting on the frame.
Further, each member of the free-body diagram is separately analyzed to identify the known and unknown forces. Generally, two-force members are considered first.
Then, the forces acting at each end and connecting point of multi-force members are determined.
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.
Suggested Reading
- Ferdinand Beer, E. Johnston, David Mazurek, Phillip Cornwell, and Brian Self (2019). Vector Mechanics for Engineers: Statics and Dynamics. McGraw Hill. Page no. 330
- Russell C. Hibbeler. (2016). Engineering Mechanics: Statics & Dynamics. Pearson. Page no.305.