STUDY ON VIBRATION RESPONSES OF A STEEL-CONCRETE VERTICAL HYBRID STRUCTURE UNDER MULTIPLE HARMONIC RESONANCE EXCITATIONS

The air cooled condenser platform is a vertical hybrid structure consisting of reinforced concrete pipe columns and space steel truss with several large-diameter fans installed on it. To study vibration responses of the structure under the excitation of fans, a 1/8 scale model is constructed and tested. The structural dynamic properties, the resonance frequencies of the structure and fans, the amplitude-frequency curves under different rotational speeds and working states of fans, and the dynamic strains of typical structural members are measured in the experiment. Numerical modal analysis and harmonic response analysis are done with ANSYS, and the calculation results are in good agreement with the test results. It is found that the vibration responses of the structure under the excitation of fans are rather slight, and the structural responses at low resonance frequencies are larger than those at high frequencies. It is also suggested to avoid the fatigue effect by rational structural constructing.