Classify each of the following trusses as stable or unstable

Classify each of the following trusses as stable or unstable. If stable, indicate if it is determinate ar indeterminate. If indeterminate, indicate the degree of indeterminacy. Assume all joints are pin-connected (20 pts). a) b) Cc)

Solution

a) If (m+r>=2j) then it is stable other wise unstable

m= number of members

r=number of reactions

j=number of joints

11+5>2*7 Hence stable.

Statically Indeterminate.

Degree of indeterminacy = m+r-2j =11+5-2*7 =16-14 =2

b)

If (m+r>=2j) then it is stable other wise unstable

m= number of members

r=number of reactions

j=number of joints

8+4>=2*6 Hence stable.

Statically determinate.

Degree of indeterminacy = m+r-2j =8+4-2*6 =12-12 =0.

c) If (m+r>2j) then it is stable other wise unstable

m= number of members

r=number of reactions

j=number of joints

10+4>=2*7 Hence stable.

Staticall determinate.

Degree of indeterminacy = m+r-2j =10+4-2*7 =14-14 =0