This paper reports on a series of shaking table tests on a full‐scale flat‐bottom steel silo filled with soft wheat, characterized by aspect ratio of around 0.9. The specimen was a 3.64‐m diameter and 5.50‐m high corrugated‐wall cylindrical silo. Multiple sensors were used to monitor the static and dynamic response of the filled silo system, including accelerometers and pressure cells. Numerous unidirectional dynamic tests were performed consisting of random signals, sinusoidal inputs, and both artificial and real earthquake records. The objectives of this paper are (i) to provide a general overview of the whole experimental campaign and (ii) to present selected results obtained for the fixed‐base configuration. The measured data were processed to assess the static pressures, the dynamic overpressures (related to the effective mass) and the accelerations of monitored points on the silo wall, and to identify the basic dynamic properties (fundamental frequency of vibration, damping ratio, dynamic amplification factors) of the filled silo. The main findings are discussed and compared with the predictions given by available theoretical models and code provisions. It is found that the fundamental frequency slightly decreases with increasing acceleration, while it slightly increases with increasing compaction of the granular material. For close‐to‐resonance input, the dynamic amplification (in terms of peak values of accelerations) increases along the height of the silo wall up to values of around 1.4 at the top surface of the solid content. The dynamic overpressures appear to increase with depth (differently from the EN1998‐4 expectations), and to be proportional to the acceleration.
In this paper, recycled polyethylene terephthalate (PET) was used to produce eco-innovative engineering materials with optimized performance, minimizing the environmental impact deriving from plastic consumption activity and limiting the continuous consumption of raw materials. The recycled PET obtained from waste bottles, commonly used to improve the ductility of concrete, has been used with a different weight percentage as plastic aggregate in the replacement of sand in cement mortars and as fibers added to premixed screeds. In detail, the effect of PET treatment (chemical or mechanical) on the thermal performance was evaluated. Non-destructive physical tests were conducted to determine the thermal conductivity of the investigated building materials. The performed tests showed that chemically depolymerized PET aggregate and recycled PET fibers derived from plastic wastes can reduce the heat conduction capacity of the cementitious materials with limited reduction in compressive strength. The results of the experimental campaign have made it possible to evaluate the influence of the recycled material on the physical and mechanical properties and its feasibility in non-structural applications.
18 December 2023 in Journal of Civil Structural Health Monitoring
The seismic design of industrial flat-bottom ground-supported silos filled with granular material still presents several challenges to be addressed. They are related to the main aspects which differentiate silo structures containing granular material from other civil structural typologies: 1) the relatively low silo structure mass as compared to the ensiled content mass; 2) the granular nature of the ensiled material. Indeed, the internal actions in the structural members are governed by the complex dynamic interactions along the interfaces between granular content and silo wall or base, or even the internal interaction between particles. More in detail, even though the scientific interest in such complex interactions dates back to the middle of the 19th century, several issues are still unclear such as the dependency of the fundamental dynamic properties (period of vibration and damping ratio) on the characteristics of the dynamic excitation (intensity, frequency content, duration) or the amount of ensiled material mass activated during a seismic excitation and provoking extra pressures on the wall (effective mass). Therefore, most of current seismic code provisions for silos are grounded on rather approximate and simplified assumptions leading to often over-conservative evaluations. The present paper intends to provide a comprehensive summary of the mainly acknowledged experimental and theoretical advances in the dynamic and seismic behavior of silos, supporting the potential researcher in the field to understand the real differences between the code assumptions and recommendations and the actual conditions, as well as illustrating the open issues to be still further investigated.