Ions and water transmembrane transport in nervous and testicular cultured cells in low gravity conditions

Aim of the present study was to investigate on the possible alter- ations induced by on ground modeled microgravity on ion-water transport proteins at cellular level. For the purpose we used astrocytes, C6 line, neurons (NT2 line from human teratocarci- noma) and testicular cells (germ cells, Sertoli cells, and Leydig cells; primary cultures from trypsinised prepuberal pig testes). Modeled microgravity was achieved by a desktop 3D Random Positioning Machine, cultures were kept rotating for 30’, 1h and 24h. After 30’, immunopositivity for the antibodies to Na+/K+ATPase and Na+/K+/Cl- co-transporters was greatly diminished, the plasma membrane appeared to be altered, and the mitochondria inner cristae were disrupted. Immunostaining to the antibody to the water channel aquaporin 4 was very bright. After 1h at random rotation immunostaining for the heat shock protein Hsp27 was visible, After 24h, immunostaining for the ion transport proteins was again like that of the controls,plasma membrane and the mitochondria were again normal. Immunostaining for aquaporin 4 become again similar to that of the controls. We conclude that low gravity induces only tran- sient alterations in the cell’s transmembrane ion-water trans- port: the cells are able to adapt to the gravity vector changes in few hours

Coupling of an SPH-based solver with a multiphysics library

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGA two-way coupling between the Smoothed Particle Hydrodynamics-based (SPH) code with a multiphysics library to solve complex fluid-solid interaction problems is proposed. This work provides full access to the package for the use of this coupling by releasing the source code, completed with guidelines for its compilation and utilization, and self-contained template setups for practical uses of the novel implemented features, is provided here. The presented coupling expands the applicability of two different solvers allowing to simulate fluids, multibody systems, collisions with frictional contacts using either non-smooth contact (NSC) or smooth contact (SMC) methods, all integrated under the same framework. The fluid solver is the open-source code DualSPHysics, highly optimised for simulating free-surface phenomena and structure interactions, uniquely positioned as a general-purpose Computational Fluid Dynamics (CFD) software with a GPU-accelerated solver. Mechanical systems that comprise collision detection and/or multibody dynamics are solved by the multiphysics library Project Chrono, which uses a Discrete Element Method (DEM). Therefore, this SPH-DEM coupling approach can manage interactions between fluid and complex multibody systems with relative constraints, springs, or mechanical joints.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia e Innovación, Xunta de Galicia con fondos de la Unión Europea NextGenerationEU y el Fondo Europeo Marítimo y de Pesca | Ref. PRTR-C17.I

Coupling an SPH-based solver with an FEA structural solver to simulate free surface flows interacting with flexible structures

This work proposes a two-way coupling between a Smoothed Particle Hydrodynamics (SPH) model-based named DualSPHysics and a Finite Element Analysis (FEA) method to solve fluid–structure interaction (FSI). Aiming at having a computationally efficient solution via spatial adjustable resolutions for the two phases, the SPH-FEA coupling herein presented implements the Euler–Bernoulli beam model, based on a simplified model that incorporates axial and flexural deformations, to introduce a solid solver in the DualSPHysics framework. This approach is particularly functional and very precise for slender beam elements undergoing large displacements, and large deformations can also be experienced by the structural elements due to the non-linear FEA implementation via a co-rotational formulation. In this two-way coupling, the structure is discretised in the SPH domain using boundary particles on which the forces exerted by fluid phases are computed. Such forces are passed over to the FEA structural solver that updates the beam shape and, finally, the particle positions are subsequently reshuffled to represent the deformed shape at each time step. The SPH-FEA coupling is validated against four reference cases, which prove the model to be as accurate as other approaches presented in literature.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Ministerio de Ciencia e Innovación | Ref. TED2021-129479A-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Universidade de Vigo/CISU

Seismic design lateral force distributions based on elastic analysis of structures

It has been often observed, as outcome of non-linear dynamic analyses that structures designed according to the force distribution proposed by Eurocode8, i.e. proportional to first mode shape, show a displacement demand at the top storey higher than those occurring at other intermediate storeys, thus increasing the probability of premature failure at this very storey. The scope of this work is to propose a new force design distribution that allows for the higher mode effects and therefore further structural dynamic characteristics

Seismic devices for steel storage structures

The importance of the logistics sector has increased even more in the last year, due to the Pandemic event which lead to an increasing of the online purchases. Goods and products are generally located in steel frames known as steel racks or simply racks. Consequently also the safe design of these structures, i.e. preserve their fully functionality and avoid their collapse, is becoming of paramount importance, especially when they are located in strong and moderate seismic zones. Despite pallet rack provisions for seismic loads have been significantly improved in the recent years, only two classic ways to enhance the seismic performance are considered: rack netting and structural strengthening. Both of these suggested solutions are not fully effective to preserve the integrity of the stored products that, when subjected to strong accelerations, can topple and fall down. The only reliable and effective systems seem to be the introduction of seismic devices, such as base-isolation and energy dissipation systems. Since no indications about these techniques are reported in the standards, many researches worldwide are trying to fill this gap. Unfortunately, up to now, just theoretical studies and very limited applications are available in literature. In the present paper a short overview on the base isolation systems available on the market for different steel storage rack typologies is presented highlighting main advantages and defects of each solution

An optimal seismic force pattern for uniform drift distribution

The force distribution proposed by codes, which in many cases is framed in the equivalent static force procedure, likely leads to design structures with non-uniform drift distribution in terms of inter-storey drift and ductility demands. This can lead to an unbalanced drift demand at certain storeys. This phenomenon may also amass cyclic damage to the dissipative elements at this very storey, therefore increasing the probability of premature failure for low-cycle fatigue. This work proposes a new force design distribution that accounts for higher mode effects and limits the displacement concentration at any storey thus improving the dissipative capacity of the whole structures. The main advantage of the proposed method stands in its formulation, which allows to spare any previous set up with structural analyses. The proposed force distribution has been applied to multi-degree-of-freedom systems to check its effectiveness, and the results have been compared with other proposals. In addition, in order to obtain a further validation of the proposed force distribution, the results obtained by using a genetic algorithm have been evaluated and compared. Additionally, the results provided in this work validate the proposed procedure to develop a more efficient lateral load pattern

Recent development on the seismic devices for steel storage structures

Goods and products are stored in framed systems, such as pallet racks, used for industrial and commercial activities. In the last years, pallet rack code provisions for seismic loads have been significantly improved, but there are still relevant aspects that need attention for guaranteeing a safer structural design. For example, in the current European and American standards, no indications are given about the seismic isolation systems applied to these structures. Only two ways to enhance the performance of racks in seismic zones are reported: rack netting and structural strengthening. Both methodologies present logistic and technical problems. For this reason, researchers are investigating more efficient solutions, like the base isolation systems. An accurate isolation system can bring benefits in terms of reduction of the structural damage and improving the safety of the stored items. Since the cost of the structural frame is often negligible, with respect to the cost of the stored products, avoiding the overturning of merchandise is an important challenge. Moreover, falling pallets can bring to the overall global collapse due to an impact given on beams or columns. In the paper, a critical overview of base isolation systems developed for different steel storage rack typologies is presented and discussed, highlighting the main characteristics and the advantages associated with their use in practical cases. Furthermore, four different applications of energy dissipation devices are briefly discussed, comparing these systems with the previously introduced devices

Residual displacements for non-degrading bilinear oscillators under seismic actions

This work aims to provide a relationship to assess the residual displacements for one-storey buildings standing in seismic-prone areas. The maximum residual displacement that a structure can possibly sustain is clearly identified by means of its structural characteristics alone. It is demonstrated that the upper bound is independent of the peak displacement. The proposed procedure can help in controlling the structural residual deformations, which is an issue that is gaining momentum into the seismic community: a large body of research has been dealing with post-seismic damage. However, no general rule or theoretical mechanic model with general validity are reported in the literature. The solely valuable approach, though widely accepted, for predicting seismic-induced residual displacements is a statistical one. In order to frame the given relationship into the established probabilistic framework, an extensive numerical campaign has been carried out by means of nonlinear time-history analyses. Artificial spectrum-compatible accelerograms are used as proxies to account for seismic events. As a final result, residual displacement response spectra are proposed

Seismic devices for steel storage structures

The importance of the logistics sector has increased even more in the last year, due to the Pandemic event which lead to an increasing of the online purchases. Goods and products are generally located in steel frames known as steel racks or simply racks. Consequently also the safe design of these structures, i.e. preserve their fully functionality and avoid their collapse, is becoming of paramount importance, especially when they are located in strong and moderate seismic zones. Despite pallet rack provisions for seismic loads have been significantly improved in the recent years, only two classic ways to enhance the seismic performance are considered: rack netting and structural strengthening. Both of these suggested solutions are not fully effective to preserve the integrity of the stored products that, when subjected to strong accelerations, can topple and fall down. The only reliable and effective systems seem to be the introduction of seismic devices, such as base-isolation and energy dissipation systems. Since no indications about these techniques are reported in the standards, many researches worldwide are trying to fill this gap. Unfortunately, up to now, just theoretical studies and very limited applications are available in literature. In the present paper a short overview on the base isolation systems available on the market for different steel storage rack typologies is presented highlighting main advantages and defects of each solution