Question

Question IV: Classify the structures shown below in figures (a), (b), and (c), as statically determinate, indeterminate, or mechanism (use the equations and/or member arrangements, as I shown on the online class, for necessary / sufficient conditions to determine). All connections are pin-joints. (a) The middle two diagonal members are not touching each other. (b) (c)

Answer 1

Static degree of indeterminacy (Ds) Ds = Ose + Dsi For truss member Dsi a Internal Static indeterminacy (m+3) - 23 where m Number of member Number of joint j 2 Dse = External static indeterminacy R-3 where R a Number of support reaction Now DS=0 stable & statically determinate Ds co > Unstable Ds >o stable & statically indeterminate.

Dse = (2+2+2)-3=3 Dsis (7+3) - 2x6 = -2 Ds 3-2 .. Ds > D ... so it is statically indeterminate structure compatibility equatim is need .. 1 ose = - (2+2)-3 =1 Dsis (8+3) – 2x 6 = -1 Ds = 1-1 .. so it is stable and statically determinate

Ise (2+ 2+ 2)-3 3 Dsi - (6+3)-2x6 = -3 Ds = 3-3 so, it is stable and statically determinate.