Seismic Analysis of Reinforced Concrete Silos under Far-Field and Near-Fault Earthquakes

Abstract

Silos are strategical structures used to stockpile various types of granular materials. They are highly vulnerable to earthquake excitation and have been frequently reported to fail at a higher rate than any other industrial structure. The seismic response of silos within the near-fault region will suffer a complex combination of loadings due to the unique characteristics of the near-fault ground motions; which are usually associated with a large amplitude pulse at the beginning of either the velocity or the displacement time histories. This study aims to numerically evaluate the seismic response of reinforced concrete cylindrical silos under near-fault ground motions (NFGM) and farfield ground motions (FFGM). The assessment investigates the impact of the slenderness ratio and the parameters' influence on the seismic behavior of reinforced concrete silos. The validity of the Eurocode provisions in the structural safety of silos will also be inspected. The nonlinear time history analysis is carried out through the finite element approach by examining four silos with different slenderness ratios. The concrete damage plasticity model is assigned to the silo wall to simulate the nonlinear behavior of concrete in the plastic zone; while, the behavior of the stored material is represented by the Drucker-Prager plastic model. The wall-granular material interaction is considered and defined by coulomb's friction theory. The results of the near-fault records reveal a growth up to 72.8% in the hoop stress and 160.4% in the vertical stress compared to the far-field earthquakes. Consequently, the seismic response of reinforced concrete silos is highly sensitive to the type of ground motion, and slender silos tend to impose greater structural demand under the NFGM. Additionally, The Eurocode-8 seismic provisions were adequate in the conventional far-field ground motions and less effective in the near-fault zone.

Performance of Single Degree of Freedom (SDOF) Systems Subjected to The Near-Fault Earthquakes

“…It is utilized to compute the inelastic SDOF systems strength demand. The rate of (R) depends on the ductility of the structure and Figure 3 shows diagram which illustrates the concept of response reduction factor [18].…”