ABSTRACT
In existing structures, particularly in prefabricated ones, structural connections can be neither absolutely rigid nor ideally elastic but semi-rigid, that significantly changes stresses and strains in the structure. Hence, there is a need to carry out the structural analysis and design taking in account the level of rigidity of connections. For that purpose the Deformation method is applied in this work assuming ratios between real and absolutely rigid fixing of the member ends to be μik and μki (0 ≤ μik ≤ 1) [1].
In this paper forming of the stiffness and mass matrices for a bar with semi-rigid connections is shown depending on the level of rigidity of a joint connection. These two matrices can be introduced into the well-known computer programs to modify them for the static and dynamic design of a plane linear system whose connections are semi-rigid.
Influence of semi-rigid connections on the changing of dynamic characteristics is illustrated by use of numerical examples. Horizontal seismic forces and maximal horizontal displacements of a frame are computed according to Yugoslav regulations, based on the circle frequencies and vibration periods of free horizontal frame vibrations calculated for different levels of rigidity of connections. Obtained results are presented in diagrams.
The results of dynamic testing of a prefabricated RC structure in full scale are presented briefly. It is concluded from the obtained results that level of rigidity of connections should not be neglected, both in the static and dynamic design, and particularly in the analysis of prefabricated structures. The special significance of the design allowing for semi-rigid connections is in earthquake engineering because seismic forces cause the joint connections to become slack, what has not been adequately taken in consideration in up-to-date dynamic analysis.
