Preconditions for Health-Monitoring of Thermal Power Plant Pipeline Systems – Experimental and Analytical Investigation

Abstract

Pipeline systems are integral parts of thermal power plants (TPP). They are of a great importance for the proper functioning of power plant systems. During normal functioning of TPP-s, pipeline systems are repeatedly subjected to cyclic harmonic loading, which results in fatigue of material and links. To increase the life-time and stability of pipeline systems, it is necessary to provide health monitoring during their serviceability period, particularly when the systems are subjected to working dynamic excitation and accidental seismic loadings. However, prior to introducing health monitoring of such systems, it is necessary to create some preconditions, namely, investigate the characteristics of the systems under dynamic loading. To this end, a 1/3 scale model was constructed based on the original prototype and tested on the seismic shaking table in the Laboratory of the Institute of Earthquake Engineering and Engineering Seismology (IZIIS) with the objective of defining the system behavior under harmonic and seismic excitation. The material presented in this paper refers to a part of these investigations related to numerical simulation and verification of the shaking-table tests of the power plant pipeline system subjected to a series of seismic excitations. The tested model consisted of a deformable part – a pipeline hung on springs, and a much stiffer part – a steel frame structure so that the overall dynamic response of such a structure was influenced by the interaction between these two parts of different dynamic properties. The analytical models were based on the finite element method and the use of the SAP2000 computer program. Special attention was paid to modeling of boundary conditions as well as spring stiffness properties. The dynamic analyses showed a very reasonable correlation with the tests in terms of obtained displacement and acceleration time-history responses that proved the validity of the analytical model. The final conclusion is that both – health monitoring testing and analytical activities are necessary for the purpose of identifying the parameters for diagnosis of the conditions of TPP pipeline systems under both serviceability and seismic loads.