The effect of partial fixity at nodal points on the behaviour of the truss and prefabricated structures

It is theoretically assumed that structural members constituting a truss system are pin connected at the nodal points. However truss system joints are rarely seen being formed as ideal pinned connections. Truss members that are connected to nodal points with weld and bolts are generally partially fixed. Therefore while designing a truss system it is important that fixity ratios of the connections should be considered in computations.

When analyzing a truss system having theoretically pinned connection, by using different section properties, (i.e. moment of inertia) except for section area, the results will not change. However, if the connections are not theoretically pinned, the moment of inertia of theoretically the sections will affect the results. Because of that reason, it is important that the partial fixity should be taken into account in computations.

Prefabricated structures are constituted by connecting separated members that are prepared before hand. In the analysis of this kind of structures, these members are assumed to be theoretically pin connected at the nodal points. However, these connections neither pinned nor rigid connection. They are partially connected. Consequently it is also important for the prefabricated structures that the partial fixities should be taken into account in designing such a system.

In this study, truss and prefabricated systems being composed of bars being partially fixed to nodal points with different ratios are investigated. Besides, how the bars having different section properties will affect the analysis is investigated. For this purpose a computer program has been developed using finite element method. It is possible to see how the displacements, end forces and stresses alter in partially fixed systems using this program.