Determine the reactions at the supports and the force in each member of the space truss shown in Fig.

 Determine the reactions at the supports and the force in each member of the space truss shown in Fig. 

Solution

Static Determinacy The truss contains 9 members and 5 joints and is supported by 6 reactions. Because m+r=3j and the reactions and the members of the truss are properly arranged, it is statically determinate.

Member Projections The projections of the truss members in the x; y, and z directions, as obtained from Fig. , as well as their lengths computed from these projections, are tabulated in Table 4.1.

Zero-Force Members It can be seen from Fig. that at joint D, three members, AD;CD, and DE, are connected. Of these members, AD and CD lie in the same ðxzÞ plane, whereas DE does not. Since no external loads or reactions are applied at the joint, member DE is a zero-force member.