Laboratory observation of shear stress recovery in rock joints asperity considering joint compaction and dilatancy

Understanding the shear stress recovery mechanism during the stick-slip motion is a fundamental requirement for predicting the sliding behavior of rock joints. In this study, slide-hold-slide (SHS) type direct shear experiments under constant normal stress are performed on granite joints with significant roughness components to investigate the effects of compaction and dilation on the shear stress recovery. The shear stress recovery of rock joints is contributed by the growth of the contact area induced by the compaction during the hold period and the enhancement of dilation work during the re-shear process. The contact area reaches the maximum value under relatively low normal stress after the long hold period. Then, the dilation gradually contributes to the shear stress recovery because the welded asperities or grains are assembled, and the slide needs to ride over these bonded areas. The surface roughness plays a significant role in the shear stress recovery since the initial aperture and asperity morphology affect the compaction and dilation. The greater magnitude of shear stress recovery observed on rougher surfaces can be attributed to the effective normal closure during the hold period and significant dilation after the long hold periods

Effect of composite slab and connection detail on cyclic behavior of steel beam-to-HSS column moment connections

This paper investigates the effects of composite slabs and connection details on the cyclic performance of steel beam-to-HSS column moment connections through advanced numerical models. Sophisticated 3D finite element (FE) models and simplified 2D plastic hinge models are developed for six connections and validated against experimental data from cyclic loading tests on five large-scale specimens. The analysis focuses on how composite slabs and connection details affect various cyclic properties, including hysteretic behavior, strength/stiffness degradation, cumulative plastic deformation, energy dissipation, equivalent fatigue fracture life, strain distribution, and failure modes. The findings indicate that composite slabs enhance the stability of the beam top flange but limit the cumulative plastic deformation ratio (η) and energy dissipation (∑E), with composite beams exhibiting only 50%–67% of η and 35%–66% of ∑E compared to bare steel beams. Furthermore, no-weld access hole (WAH) connections, in contrast to field-welded connections, effectively shift the plastic hinge outward, thus delaying flange fracture. The average η of no-WAH connections was 1.6 and 2.6 times higher than that of modern field-welded and pre-Kobe connections, respectively, and the average ∑E was 2.0 and 3.8 times higher. The proposed FE models offer comprehensive seismic assessments for beam-to-HSS column connections, aiding in detailed parametric analysis. The simplified plastic hinge models, which incorporate cyclic deterioration and fracture behavior, provide a more efficient and practical modeling approach and parameters for system-level frame analyses

Hysteretic magnetic field analysis with Second-Order homogenization

A dynamic hysteresis model represented by the Cauer circuit was combined with the finite element analysis to efficiently compute magnetic field in micro-structured iron-cores. A finite element eddy-current analysis with higher order homogenization method is reformulated to implement the Cauer circuit representation. Three types of hysteretic Cauer circuits for the 2nd-order homogenization were examined. The analysis of wounded core under sinusoidal excitation showed that the 2nd order homogenization scheme with finite difference approximation improved the accuracy of representation of iron loss and current-flux loops. The 2nd-order scheme also improved the accuracy of homogenized representation under pulse-width-modulation excitation. The computation time was greatly reduced by the homogenization schemes

Small ship collisions in coastal areas during tsunamis: Impact on seawalls behind sand dunes

Coastal regions often feature seawalls situated behind sand dunes, introducing unique topographical factors that significantly influence ship drift and collision behavior. This study investigates the collision dynamics of a small ship, particularly fishing boats, in coastal areas during tsunamis and the subsequent impact forces on a seawall behind dunes. Through hydraulic model experiments, the characteristics of tsunami-driven drift, collision probabilities, and instantaneous impact forces were examined. The likelihood of ship collisions with seawalls increased when the dimensionless initial position of a ship (the ratio of its distance from the shore to the tsunami breaking point) was less than 0.6. The impact force experienced by a ship was influenced by the behavior of the water mass rising in front of the seawall post-tsunami. Collisions before the descending water mass resulted in increased impact forces, while collisions post-descent showed forces decreased owing to reduced drift velocity. In cases where ships encountered falling water masses before a collision, impact forces decreased significantly compared to other scenarios. An equation to estimate ship impact velocity, accounting for dune effects, based on the dimensionless time difference between the tsunami and ship collision and the tsunami propagation velocity calculated from near-shore tsunami height was introduced. This equation considers the damping effect of impact velocity, improving accuracy within the experimental range of small impact forces

Charge transfer across the ionic liquid/oil interface: Facilitated ion transfer and electron transfer

Facilitated ion transfer (FIT) and electron transfer (ET) across the ionic liquid (IL)/oil (O) interface between ethylamine nitrate (EAN) and 1, 4-dichlorobutane (DCB) have been electrochemically studied. Cyclic voltammograms (CVs) for the FIT of Li⁺ cation in IL by dicyclohexano-18-crown-6 (DCH18C6) across the IL/O interface formed at a micropipette tip show that the onset of the FIT current is significantly shifted due to the facilitation beyond the potential window limit and that the current is proportional to the concentration of DCH18C6 in O limited by the diffusion of DCH18C6 inside the micropipette. CVs for the ET from supporting electrolyte anions in O to NO₃⁻, the IL anion of EAN, across the IL/O interface studied using a closed-bipolar cell show that NO₃⁻ in EAN has an ability to oxidize tetraphenylborate ions in O but not tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate ions, the latter of which have more oxidation resistance

Does accrual information impact municipal bond prices? Evidence from Japan using AI

This study aims to empirically determine the extent to which accrual-based information disclosed by local governments contributes to the pricing of municipal bonds using eXplainable artificial intelligence, which provides better regression accuracy than multiple regression analysis. The analysis is particularly crucial in the world’s many non-bankruptcy law countries: those without legislation for local government failure. Very little research has been conducted to date on their municipal bond markets. This study focuses on the Japanese market as a representative non-bankruptcy law country. The results demonstrate that accrual-based information disclosed by local governments contributes as much to determining municipal bond prices as traditional disclosure information other than accrual-based information, even in a non-bankruptcy law country, such as Japan