R TARINEJAD - Assistant professor, Civil engineering faculty, University of Tabriz, Tabriz, Iran
R FATEHI - MSc. Student, Civil engineering faculty, University of Tabriz, Tabriz, Iran
A MAHDAVI - MSc. Student, Civil engineering faculty, University of Tabriz, Tabriz, Iran

Seismic Retrofitting of Lifelines in order to improve their safety and prevent irreparable damages during earthquakes has been attracted special attentions, Because of their crucial role in human life. Different kinds of energy absorbing systems, such as yielding dampers, have been used in structural and industrial parts in recent years. In this paper the effects of using of accordion yielding connections as energy dissipation devices on seismic behavior of the pipeline systems is studied. This kind of connection can be used instead of rigid connection or other energy absorbing systems at both ends of the pipes, valves joints and bents. Numerical modelling of a pipeline system using finite element method is done for two different cases: with accordion yielding connection and without accordion yielding connection. Modal analysis for two different cases show that the dynamic properties of pipeline system is changed (27% average reduction for natural frequencies) using the accordion connections. Seismic analyses are done with 1952 Taft Earthquake accelerograms and the results are compared for two different cases. The results of time-history analysis show that the dynamic responses of the main pipeline on the system with accordion connection are severely reduced because of high energy absorption and deformation along the accordion connections. The results show that the stresses are reduced up to 58% by using accordion connections in the main pipeline system so using this kind of connections lead to increasing their safety during earthquakes. By using the accordion connection in the pipeline systems the probable damage is expected to be appeared only along this connection and the rest parts of the pipeline experience safe conditions.

lifelines,seismic retrofit,accordion connection,energy absorption,finite element