A beam of length L = 8 m is loaded with a uniformly distributed load w = 4 kN/m. Determine the reactions at supports A and B.
Consider a free-body diagram of beam AB. There are three unknown forces and moments: Ay, MA, and By.
With three unknowns and only two equilibrium equations (i.e., ΣFy = 0 and ΣM = 0), the unknown forces cannot be determined using statics alone. This type of problem is known as statically indeterminate. To solve the problem, a third equation that includes the unknown forces must be developed.
Note: Since there are no forces in the horizontal direction, the ΣFx = 0 equilibrium equation will be omitted.