2 2 Classify the trusses in Figure P42 as stable or un hle I

2 2 Classify the trusses in Figure P4.2 as stable or un- hle. If stable, indicate if determinate or indeterminate. f indeterminate, indicate the degree. P4.2

Solution

a) Stable if (m+r>2j). Otherwise unstable.

m= number of members

r= number of reactions.

j= number of joints.

17+5>2*10 =22>20: Hence stable

Degree of indeterminacy = m+r-2j = 22-20 =2: Statically indeterminate to 2nd degree

b) Stable if (m+r>2j). Otherwise unstable.

m= number of members

r= number of reactions.

j= number of joints.

13+5=2*9 19=18: Hence stable

Degree of indeterminacy = m+r-2j = 19-18 =0: Statically determinate

c) Stable if (m+r>2j). Otherwise unstable.

m= number of members

r= number of reactions.

j= number of joints.

8+4=2*6 =12>12: Hence stable

Degree of indeterminacy = m+r-2j = 12-12=0: Statically determinate

d) Stable if (m+r>2j). Otherwise unstable.

m= number of members

r= number of reactions.

j= number of joints.

14+3>2*8 =17>16: Hence stable

Degree of indeterminacy = m+r-2j = 17-16 =1: Statically indeterminate to 1 degree