teknik – vol. 29 no. 2 tahun 2008, issn 0852-1697 139 *) staf pengajar jurusan d iii teknik sipil fakultas teknik undip tegangan sekunder pada struktur rangka batang

In our previous analysis of trusses, it was always assumed that the truss members are joined by idealhinges and that loads are applied only at joints. The centroidal axes all of members are stright,coincide with the lines connecting the joint center, and lie in a plane that also contains the lines ofaction of all the loads and reaction. Thus the members of truss are subjected to axial force only, andthese can be determined by static method. A stress analysis base on these assumtion leads to thedetermination of so – called “primary stresses”.In actual cases the joint are usually riveted or welded; and because of this fact the members undergo,not only axial forces, but also bending stresses from secondary moment, cuased by this condition arecalled “secondary stresses”. In discusing secondary stresses we shall consider only trussses in oneplane and assume that this plane represents the plane of symmetri for all members and that externalloads are acting in the same plane. Of these the most important are caused by the fact that the jointare rigid, and hence the members are not free to change their relative directions when the truss isdeformed. This problem can likewise be solved very eficiently by means of moment distibution.From the first analyze result, it was obtained the scondary tension ratio with the primary tension at thepull shaft about 19.20 %. This result is significant that it will increase the existence of primary tension.At the analyze by SAP 2000 is obtained that the end tension much more lower than the scondarytension in the first analyze. This is need to obtain attention at planning trusses.