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A meshless local scour model for cylinder bridge foundation based on the smoothed particle hydrodynamics (SPH) method is proposed in this paper. Differing from the traditional Eulerian mesh model used for monopile local scour, it overcomes the high requirements of mesh quality and density for capturing large deformations at the fluid interface. Unlike the transient sediment erosion SPH model used for dam-break, sediment flushing, and water jet, the meshless approach is innovatively applied to the continuous simulation of bridge local scour under steady flow conditions. The present SPH model is established based on the SPH multi-phase fluid model, integrating a classical fluid model combined with numerical stabilization algorithms to govern water particle motion and a sediment model from Zhang et al. (2024) to govern sediment evolution, and tests a new scheme for boundary treatment in the model based on DualSPHysics. Furthermore, a novel scour visualization method that aims at extracting both visible and actual bed surfaces from discrete particles is proposed. The model is validated through comparison with rigid bed and live bed experiments, demonstrating favorable agreement in terms of flow and scour simulation. Importantly, the model results reveal a discrepancy between the elevation of the post-scour visible bed surface derived from the conventional Eulerian mesh model and experimental data, compared to the actual bed surface unaffected by water flow erosion. This indicates the necessity for incorporating a safety margin in foundation design when utilizing experimental results to determine the maximum scour depth. • A meshless numerical simulation method for local scour of bridge foundation is proposed. • An improved in\out boundary for the multi-phase SPH model is proposed. • The mDBC boundary for the multi-phase flow model is proposed. • A scour visualization method is proposed to extract the actual bed surface from discrete particles. • A suggestion for foundation scour resistance design are proposed according to the model results. [ABSTRACT FROM AUTHOR]

The erosion of soil around bridge shallow foundation piers can substantially increase the fragility of bridges during flood events. The available research for assessing the fragility of shallow foundation piers under floods is predominantly qualitative, while ignoring the influence of coupling effects arising from complex hydrodynamic-soil-structure interactions. To fill these gaps, a numerical solver for coupled simulations accounting for hydrodynamic-soil-structure interaction is developed, facilitating boundary conversions for different physical fields and updating them over time. The numerical solver is validated in terms of subgrade reactions, pier displacements and scour extent based on the results of open-channel tests of a reference shallow foundation pier. The validation results show that the developed coupled solver has satisfactory accuracy in predicting the morphology of scour-hole and failure process of shallow foundation piers. Then all potential failure modes of shallow foundation piers under floods are analyzed within the framework of deterministic analysis. Finally, a probabilistic fragility analysis using the coupled solver accounting for uncertainties in hydraulic, structural, and geological parameters is performed through the Latin Hypercube Sampling method. The study concludes that the deterministic analysis without considering the uncertainties in model parameters leads to underestimating the risk due to overturning failure and vertical failure. • A numerical solver is developed to simulate hydraulic failures of shallow foundation piers via coupled simulations. • The solver is validated using subgrade reactions, pier displacements and scour extent from open-channel tests. • The failure modes and envelopes of shallow foundation piers under flood loading space are investigated. • The results show that deterministic methods tend to underestimate the risk of potential failure modes. [ABSTRACT FROM AUTHOR]

Target of Myb1 (TOM1) facilitates the transport of endosomal ubiquitinated proteins destined for lysosomal degradation; however, the mechanisms regulating TOM1 during this process remain unknown. Here, we identified an adjacent DXXLL motif-containing region to the TOM1 VHS domain, which enhances its affinity for ubiquitin and can be modulated by phosphorylation. TOM1 is an endosomal phosphatidylinositol 5-phosphate (PtdIns5P) effector under Shigella flexneri infection. We pinpointed a consensus PtdIns5P-binding motif in the VHS domain. We show that PtdIns5P binding by TOM1 is pH-dependent, similarly observed in its binding partner TOLLIP. Under acidic conditions, TOM1 retained its complex formation with TOLLIP, but was unable to bind ubiquitin. S. flexneri infection inhibits pH-dependent endosomal maturation, leading to reduced protein degradation. We propose a model wherein pumping of H+ to the cytosolic side of endosomes contributes to the accumulation of TOM1, and possibly TOLLIP, at these sites, thereby promoting PtdIns5P- and pH-dependent signaling, facilitating bacterial survival. [Display omitted] • Binding of TOM1 VHS to ubiquitin is enhanced by an internal DXXLL motif • Binding of TOM1 to PtdIns5P is maximal under acidic conditions • TOLLIP's binding to PtdIns5P also increases as pH acidifies • A tight TOM1-TOLLIP complex binds to PtdIns5P under acidic conditions Xiong and Roach et al. report a DXXLL motif in TOM1 that increases its affinity for ubiquitin binding. They identify a PtdIns5P-binding site in TOM1 and demonstrate that its binding is maximal under acidic conditions. Furthermore, under these conditions, the TOM1-TOLLIP complex also interacts with the phosphoinositide. [ABSTRACT FROM AUTHOR]