الفهرس 
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Abstract
In theory of structures the plane truss is designed under the assumption, that its joints are frictionless, the centroidal axes of the members are straight and coincide with the connecting line between joint centers at the end of each member. The truss is in elastic state and the loads are only applied at the joints.
In real trusses the joints are rigid or semi-rigid, because they are welded or bolted. The centroidal axes do not always coincide with the connecting line between the joint centers. Thus the truss is subjected to bending moments and shear as well as axial forces, even if the truss is only loaded at the joints. The stresses that occur due to bending and shear are called secondary stresses. It is assumed that their values does. not exceed 30 % of the primary stress’ values and they are neglected in the design.
This thesis studies several factors that have great influence on the value of secondary stresses. First, the chord members of the truss are manufactured in the workshop as one continuous member. Second, the effect of moving loads on the truss as in the case of a crane bridge. The third factor is when the upper steel chord is connected to an R.e slab by shear studs, thus acting as one composite section.
Several truss models are studied, subjected to different cases of loading. The truss models are assumed to be in elastic state and the effect of lateral buckling is neglected. The stresses are computed for each case and compared. From the results of this study, it may be concluded, that the determination of the secondary stresses is very important in some cases, The assumption of an ideal truss with ideal conditions can lead to incorrect design. The type of truss affects the stress distribution.
Also, the continuity of the chord member allows the truss to be loaded by direct moving loads.
The design of trusses using composite section is possible and economic. Propped section against deflection is preferable, because it produces smaller stress values in the upper and lower steel sections.