بررسي امكان كاربرد روش "زمان دوام" در تحليل لرزه يي مخازن فولادي

INVESTIGATION OF THE POTENTIAL APPLICATION OF THE ENDURANCE TIME METHOD IN THE SEISMIC ANALYSIS OF STEEL TANKS

The development of experimental science and the amaz- iug improvement in computational tools have caused sci¬entists and researchers to provide the infrastructure for the development of new methods, which are more ap¬propriate and rational, in comparison with traditional methods, in structural engineering. Performance based design methods and increasing static and dynamic load methods are some examples. The behavior of liquid storage tanks under seismic loading has been consid¬ered by engineers and researchers because of their im¬portance and soil-structure interaction. The initial ana¬lytical models for the dynamic analysis of liquid storage tanks were based on simple assumptions, such as wall rigidity, that have been gradually modified. In this pa¬per, a new method for performance based earthquake analysis (seismic analysis) and the evaluation of struc¬tures, which is called the Time Endurance method, is introduced. In this method, the structure is subjected to accelerograms that impose increasing dynamic demand on the structure with time. The purpose of this project is investigating the application of an ET method in the seismic design of ground-supported steel storage, tanks and comparing them with the seismic design codes of steel tanks (snch as API and AWWA). In addition, the obtained results of the ET method are compared with the obtained results of the seismic design codes. Then, the compatibility of the ET method in seismic design is investigated, in comparison with the codes. First, an ex¬tensive literature survey was carried out, regarding the mechanical models introduced for the seismic analysis of tanks and related design codes. Then, the dynamic re¬sponse of the flexible storage tanks under different input ground motions has been investigated, using the finite element method. For this purpose, the container and its fluid have been modeled with displacement based el¬ements, using the general-purpose finite element code ANSYS. In an axisyinmetric harmonic and 3D model¬ing, the specifications of one of the existing cylindrical tanks have been adopted. The compressibility and vis¬cosity of the containerʹs fluid have been also taken into accouut,.