Grain storage is universally recognized as one of the post-harvest infrastructure elements for national food security and societal stability. Among them, the multiple-floored grain warehouses can directly dominate the long-term reliability of the grain reserve. Its safety and stability can also require storing the grain from natural hazards and operational risks. Thereby, it is very necessary to safeguard the national food supply chains during emergencies. Particularly, the conventional single-story structures cannot fully meet the large-scale production requirements in recent years. In this study, the multi-floored grain warehouse was developed under different storage conditions. An advanced form of centralized bulk grain storage was provided for the high-density urban environments. The high mechanization was combined with efficient material handling and a compact land footprint. Thus, the storage efficiency was maximized to alleviate the land scarcity driven by rapid urbanization. A critical influencing factor under seismic loading was then obtained as the interaction between stored grain and the supporting structure in the overall dynamic response. The mass, stiffness, and inherent damping of stored grain altered the structural vibration modes, thus potentially reducing the seismic demand from the complex load transfer mechanisms. A series of shaking table experiments was conducted on the representative multi-floored grain warehouse. A 1:25 geometric similarity model was constructed to verify the measurement. Eight typical conditions of grain storage were selected: empty warehouse (EEE), fully loaded warehouse (FFF), third-floor empty (FFE), second-floor empty (FEF), first-floor empty (EFF), third-floor full (EEF), second-floor full (EFE), and first-floor full (FEE). Each condition was tested under six peak ground acceleration (PGA) levels (0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g, and 0.6 g). Finally, a systematic examination was carried out on the structural dynamics and seismic response. The results demonstrate that the stored grain consistently reduced the structural acceleration amplification, where the magnitude of damping was positively correlated with both PGA and storage elevation. For instance, the EFF condition decreased the top-floor acceleration by 44.1%, compared with the EEE condition at the highest test intensity (0.5 g). As such, the stored grain served as an effective vibration-mitigation medium. The peak acceleration of the grain itself was slightly lower and then delayed relative to the silo wall, indicating an energy dissipation caused by grain–grain and grain–wall friction. The displacement response was found to be jointly influenced by storage height and vertical discontinuity in grain distribution, where the latter shared the greater tendency to induce the torsional vibrations. Notably, the FEF condition generated the second-floor displacements of 24.7% and 4.0% higher than those of the EFF and FFE, respectively, under 0.5 g two-floor loading. The uneven patterns of the vertical loading significantly amplified the structural drift in the intermediate floors. Furthermore, the lateral pressure increased with the burial depth and PGA, where the strong-motion cases exhibited the pronounced overpressure. The lateral pressure at point P5 reached 1.46 times its static value in the EFE condition at 0.5 g. The substantial dynamic amplification of silo wall loads was obtained during intense earthquakes. Grain distribution also dominated the seismic performance. The optimal vertical loading can be expected to serve as a passive control strategy for the seismic demand. These findings can provide a technical basis for the seismic design and optimization of the multi-floored grain warehouses, thus supporting their application in national grain reserves and emergency supply facilities.
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Granular grain can be stored into the warehouse in food industry. The high loading efficiency is often required to optimize the land use for the effective grain preservation. The crucial warehouse mode has emerged in the regions with limited land resources. The diverse grain varieties can be stored to promote the sustainable development. Currently, the granular grain warehouse normally employs a load-bearing system that constituted by a reinforced concrete frame structure. The vertical gravity load of the grain is supported by the well-beam floors and large-section frame columns, while the lateral pressure exerted by the grain is directly absorbed by reinforced concrete horizontal tie-up beams integrated within the warehouse walls. The structural integrity of granular grain warehouses can also depend on the dynamic lateral pressure exerted by the storage material on the warehouse wall during seismic events. In this study, a scaled-down 1:25 three-story warehouse was designed and then produced to explore the effect of granular grains on the dynamic lateral pressure. Shaking table tests were carried out to simulate the varying ground vibration levels under three seismic waves. The data was collected on the acceleration and the lateral pressure that exerted on its walls. Analysed the seismic response characteristics of the storage material. Furthermore, the overpressure coefficient was obtained from the patterns of dynamic lateral pressure on the walls. The dynamic lateral pressure on the warehouse walls was also calculated. Acorrelation analysis was conducted between the height of warehouse and the timing of the peak moment, when the dynamic lateral pressure was exerted on the warehouse walls. Specifically, there was a noticeable lag in the occurrence of this peak moment, as the height of the building increased. Moreover, the peak moment of dynamic lateral pressure on the warehouse wall was consistently lagged behind that of acceleration on the same wall, particularly with the elevation of the height. The dynamic lateral pressure on the warehouse walls escalated progressively with each ascending floor. In the given floor, this dynamic lateral pressure incrementally intensified along the vertical extent of the warehouse walls. Each floor was found with an average increase of approximately 29% per floor. The dynamic lateral pressure exerted on the upper and middle sections of the warehouse walls was 2.5 and 1.4 times greater than that on the lower sections within the same floor. Consequently, the structural design of granular grain warehouses should consider these variations across different floor levels. The overpressure coefficient of the warehouse wall increased with the elevation of the floor, indicating a higher overall overpressure at upper levels. Within a single floor, the overpressure coefficient peaks at the upper section of the warehouse wall, with the middle and lower sections exhibiting lower and closer. Specifically, the maximum overpressure coefficients were 2.9, 3.4, and 4.1, respectively, for the first, second, and third floors of the warehouse walls. The overpressure on the warehouse walls was of significant concern, when subjected to seismic activity. It is very necessary to consider the influence of the dynamic lateral pressure on the warehouse wall across various floors. The seismic response of the storage materials can be used to elucidate the distribution pattern of dynamic lateral pressure. The overpressure on the warehouse walls can be assessed to calculate the lateral pressure on these walls. The findings can offer a strong reference for the warehouses of granular grains under seismic conditions.
Packaged grain stacking serves as the primary storage method for finished grain globally. However, stack inclination and collapse remain persistent safety hazards, threatening both economic sustainability and food security. Current industrial practices lack a systematic understanding of the interlayer friction mechanics governing stack stability, particularly under variable stacking geometries and long-term storage conditions. This study addresses this critical gap by quantitatively investigating the deformation-coupled friction behavior of packaged grain layers, aiming to establish a predictive framework for collapse risk assessment and provide actionable insights into the optimization of storage configurations. The urgency of this work is underscored by escalating global grain storage demands and the need to minimize postharvest losses estimated at 8% to 10% annually because of improper stacking practices.
A dedicated friction performance testing platform was developed to evaluate the interlayer friction dynamics in packaged grain stacks. The grain bag friction testing device was independently developed and mainly consisted of three systems: horizontal tension, vertical load, and measurement. The packaged grain was subjected to horizontal tension provided by a horizontal tensioning system, with a quantifiable vertical load applied to its upper part, and the horizontal tension and horizontal displacement of the packaged amount under different load conditions were obtained by the measurement system. The values obtained by the horizontal tension and horizontal displacement sensors were recorded, and the relationship curve between horizontal tension and horizontal displacement was plotted. Controlled experiments were conducted to analyze key variables, including stacking patterns (i.e., laminated seamless, vertical–horizontal crisscross, and multisided contact arrangements), grain layer deformation, and interlayer interactions. Quantitative metrics, such as equivalent friction coefficients, were measured under incremental vertical loads to characterize friction evolution.
The results showed that the deformation of packaged grain is a significant factor affecting the interlayer friction characteristics. The interlayer contact friction initially increases with the increase in deformation, subsequently reaches the maximum value, and finally tends to be stable. The friction characteristics of packaged grain are affected by the interlayer contact friction performance of the packaging bag, the bite effect between the grain particles on the surface of the packaging bag, and the mutual embedding effect between the bags. Because of the slight outward expansion of the side of the multilayer stacked packaged grain during stacking, the extrusion effect forms on the side of the adjacent packaged grain, and the equivalent friction coefficient of the interlayer contact is larger than that of the single-sided contact. Under the same vertical load, the equivalent friction coefficient of the vertical and horizontal crisscross arrangements (i.e., the lower transverse juxtaposition) of the packaged grain is increased by 41% to 47% compared with the laminated seamless arrangement, and the equivalent friction coefficient of the four-sided contact extrusion arrangement is increased by 38% to 57% compared with the double-sided contact extrusion arrangement.
This study establishes a deformation-coupled friction model for packaged grain, revealing that optimized stacking geometries significantly enhance interlayer friction and collapse resistance. The quantified friction increments under crisscross and multisided contact arrangements provide actionable guidelines for designing stable grain stacks. These findings advance the mechanistic understanding of stack collapse and provide a scientific framework for improving grain storage safety standards.
Vertical silo is a type of container widely used in industrial and agricultural storage, transportation, and grain storage. According to its supporting structure, it can be divided into column supported and cylindrical supported types. As a modern grain storage warehouse type, column supported vertical silos have a small footprint, large storage capacity, and complete grain receiving, distribution, storage, cleaning, weighing, and automatic control functions. Different storage conditions have a significant impact on the dynamic characteristics of column supported vertical silos. To reveal the influence of grain dispersion on the dynamic characteristics of column supported vertical silos, an organic glass silo model with a scale ratio of 1:25 was designed and made based on an actual column supported vertical silo design. Vibration table modal tests, finite element numerical analysis, and natural frequency theoretical calculations were conducted under four storage states: empty, half, three-quarters, and full. The research results indicate that different grain storage conditions have a significant impact on the natural frequency of the column supported vertical silo test model. As the grain storage state changes, the natural frequency decreases significantly, and should be considered in structural design; The damping ratio is the smallest in an empty warehouse state, and it increases by 42.65% in a full warehouse state compared to an empty warehouse state. The more existing grain is stored in the warehouse, the greater the increase in damping ratio and the more obvious the shock absorption and energy consumption effect; There is a significant difference between the torsional stiffness of the finite element model and the first two translational stiffness. Compared with the first two periods, the natural frequency of the third order of empty, half, three-quarters and full grain storage conditions increased by 27.2%, 37.27%, 39.93% and 40.09% respectively; The average error between the first-order natural frequency of the finite element model and the experimental value is 5.1%. The constructed finite element model is relatively reasonable, providing a reasonable numerical simulation method for structural dynamic response analysis and structural design; The simplified three particle series multi degree of freedom elastic dynamic model accurately calculates the natural frequencies of column supported vertical silos under four storage conditions, with an average error of 5.6% between experimental and theoretical values. This study can provide reference for the calculation of dynamic characteristics of column supported vertical silo structures, and provide theoretical basis and experimental basis for their seismic performance design.
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