On the use of three-force member concept versus equilibrium equations in Statics

ABSTRACT

Use of three-force member concept for rigid bodies whenever possible, to circumvent the more taxing use of equilibrium equations has been long-established. However, most students fail to reap its benefits due to a number of reasons, including the fact that its importance is hardly emphasized to them; skills and details needed for the concept are missing in many undergraduate textbooks on Statics. This paper revisits and solidifies the understanding of three-force member in exploiting its potential for solving difficult problems. The paper addresses one of the most frequent students’ questions and concerns that the authors have faced in their experience of teaching Statics. This topic is revitalized herein, and its importance emphasized, to obviate the possibility of students’ wrong impression about its obsoleteness, by presenting detailed material in a pedagogical manner to serve as an addendum to any textbook for university undergraduate course in Statics. This serves as a good reference for both instructors and students in the course and eliminates their difficulty in accessing a concise document on the topic. Four examples, with increasing complexity, are solved where quicker and easier steps using three-force member concept are compared with the lengthier and relatively more difficult use of equilibrium equations.

KEYWORDS:

• Three-force member
• equilibrium equations
• geometry
• Statics

MSC:

• 70C20
• 51-01

Acknowledgment

The authors would like to acknowledge the support of King Fahd University of Petroleum & Minerals (KFUPM).

Disclosure statement

No potential conflict of interest was reported by the authors.