Chapter 6.2, Problem 6.73P

6.70 through 6.74 classify as determinate or indeterminate. (All members act both in tension and in compression.)

Fig. P6.73

Structure (a):

Rigid truss with r = 3, m = 14, n = 8,

so r + m = 17 > 2n = 16

so completely constrained but indeterminate

Structure (b): Simple truss (start with ABC and add joints alphabetically), with

r = 3, m = 13, n = 8, so r + m = 16 = 2n

so completely constrained and determinate

Structure (c):

Simple truss with r = 3, m = 13, n = 8, so r + m = 16 = 2n, hut horizontal reactions (A_x and D_x) are collinear, so cannot he resolved by any equilibrium equation.

Structure is improperly constrained.