Explore the vast range of titles available.

Performance of reinforced concrete (RC) walls in recent laboratory tests and in recent strong earthquakes has revealed that thin wall boundaries are susceptible to concrete crushing, reinforcing bar buckling, and lateral instability. To address this concern, a wall database with detailed information on more than 1000 tests was assembled to enable the study of the impact of various parameters on wall deformation capacity. For this study, the data are filtered to identify and analyze a dataset of 164 tests on well-detailed walls generally satisfying ACI 318-14 provisions for special structural walls. The study indicates that wall deformation capacity is primarily a function of the ratio of wall neutral axis depth-to-compression zone width (c/b), the ratio of wall length-to-compression zone width ([l.sub.w]/b)), wall shear stress ratio ([v.sub.max]/[square root of (term)][f'.sub.c], and the configuration of boundary transverse reinforcement. Based on these observations, an expression is developed to predict wall drift capacity with low coefficient of variation. Keywords: compression zone width; cross-sectional aspect ratio; drift capacity; overlapping hoops; structural wall; wall shear stress.

This paper assesses the effect of direct and indirect factors on the shear performance of ultra-high performance fibre reinforced concrete beam containing coarse aggregate (UHPFRC-CA) using four point loading arrangement. The obtained results were used to categorize UHPFRC-CA beam's failure mode, establish the influence of key factors on shear performance, and develop UHPFRC-CA beam's compression zone resistance and first shear cracking load equations whose results were compared with those from this research, other researchers and existing equation. Findings revealed that UHPFRC-CA beam fails in cable stayed, shear partial compression, cable stayed-diagonal tension and cable stayed-partial shear tension. Shear span-depth ratio (a/d) has the most influence on the beams' failure mode. Higher percentage volume of steel fibre improves ultimate load capacity and midspan displacement resistance at failure load. Hooked-end steel fibre improves deformation (crack width and midspan displacement at failure load) resistance. Higher a/d is more beneficial to midspan displacement resistance at failure load than load capacity; while lower stirrup spacing leads to higher midspan displacement at failure load. Finally, the developed first shear cracking load equation can adequately capture the true first shear cracking load of UHPFRC-CA beam; and the developed compression zone resistance equation can be conveniently used to represent the joint contribution of compressive strength and fibre factor to UHPFRC-CA beam's shear resistance.

The ANSYS software is used for finite element numerical simulation to analyze the failure mechanism of local compression in concrete cone foundations in conjunction with previous experimental experience. The results reveal that the “hooping action” of surrounding concrete and the arch structure under the compression zone causes the increase of local compression in the concrete cone foundation. According to the findings of the analyses, the failure of local compression in concrete cone foundations is caused by the combined action of top shear force, middle splitting force, and top splitting force. The results also demonstrate that the failure mechanism of local compression in concrete cone foundations may be explained more rationally by integrating the theories of hoop strengthening and shear strength. These results serve as a basis for further study into the calculation method of cone foundation local compression.

In view of a previous study of the intermediate principal stress effect at a limited σ2 range, a series of true triaxial tests, covering a full range of intermediate principal stresses that vary from the generalized triaxial compression stress state (σ2 = σ3) to the generalized triaxial tensile stress state (σ1 = σ2), was carried out on sandstone and granite samples. The experimental results revealed that the deformation, failure strength and failure mode have a significant dependence on the stress state. As an effect of the intermediate principal stress on crack evolution, the deformation difference known as stress-induced deformation anisotropy occurred and should be considered when developing the mechanical model. Moreover, a post-peak deformation with a step-shaped stress drop is observed and illustrates that there will be a multi-stage bearing capacity after the rock failure. The peak strength is non-symmetrical with the increasing σ2 and is closely related to the Lode angle. Based on the final fracture surface and SEM analysis under true triaxial compression, three failure modes and failure zones, including tension failure, shear failure and mixed failure, are delineated and discussed. Combining the failure mode and the strength under true triaxial compression, it is found that the strength variation exhibited a close relationship to the failure mechanism.

A three-dimensional unsteady CFD model was developed to investigate leakage behavior within the compression compartments of a scroll-type compressor used in automotive air-conditioning systems. The effects of variations in axial and radial gaps on volumetric and isentropic performance were examined, along with the transient evolution of temperature and pressure within the compression zones. The results show that, when the axial spacing is kept at 0.02 mm, enlarging the radial gap from 0.02 mm to 0.05 mm reduces volumetric efficiency from 95.68% to 93.09% and lowers isentropic efficiency from 85.67% to 80.38%. Conversely, with the radial clearance maintained at 0.02 mm, increasing the axial gap to 0.05 mm decreases volumetric efficiency from 95.68% to 84.10%, while isentropic efficiency drops from 85.67% to 69.13%. As both clearances increase, the average mass flow through the compressor’s suction and discharge ports gradually declines. It is evident that the axial spacing has a stronger influence on overall compressor performance, highlighting the importance of precise control of the axial gap to ensure stable and reliable operation.

Creating accurate predictive models for drift and pack ice is crucial for a wide array of applications, from improving maritime operations to improving weather prediction and climate simulations. Traditional large‐scale sea ice dynamics models rely on phenomenological ice rheology to simulate ice movements. These models are efficient on large scales but struggle to depict smaller‐scale ice features. In our study, we use a new version of the HiDEM discrete element model software to examine the formation of drift and pack ice under various stress conditions. Our findings show that high‐resolution size distributions of ice floes are universal and multimodal, and that compression ridges form three distinct zones. Reproducing complex characteristics of this nature in a standard rheology model is challenging, suggesting that a combination of models may be necessary for more precise predictions of sea ice dynamics. We propose a potential hybrid algorithm that integrates these approaches. Plain Language Summary Sea ice forms in cold climates and is susceptible to being easily fragmented by wind and currents, resulting in a dynamic landscape comprising solid fast ice, drift ice and pack ice. Pack ice, in particular, can pose challenges such as hindering shipping, causing damage to offshore structures, and complicating traditional fishing and hunting activities. Operational models for sea ice dynamics are currently utilized to optimize ship routes and the deployment of icebreakers. Although existing rheology‐based models perform well on large scales, they encounter difficulties in capturing the finer details that are often crucial. In this study, we utilize a high‐resolution Discrete Element Model computer code that is capable of simulating detailed sea ice dynamics at scales ranging from meters to kilometers. Our simulation results reveal insights that are not readily obtained from conventional large‐scale models, and we explore the potential for integrating these two approaches to create a hybrid model. Key Points Ultra high‐definition simulation (0.5 m elements) of sea ice fragmentation on a square kilometer scale The HiDEM model captures in fine detail the formations of leads, pressure ridge networks, and floe‐size distributions The model reveals features that cannot be reproduced by rheological models, suggesting a hybrid method for prediction

Most earthquakes occur at plate boundaries, but some also strike within stable continental interiors. Although dominant causes of such intraplate earthquakes remain elusive, a prevailing hypothesis attributes intraplate stress and seismicity to variations in lithospheric thickness. Here, we test this hypothesis using the Korean Peninsula as a natural laboratory by constructing three‐dimensional numerical models that extend from the surface to a depth of 650 km, incorporating realistic plate boundary configurations and deep thermal and compositional heterogeneities. Our results show that lithospheric thickness variations alone cannot account for the observed seismicity distribution and stress orientations. Instead, models that include weak subduction interfaces, slabs extending into the transition zone, and mantle buoyancy—while excluding shallow lithospheric density contrasts—explain the observed seismicity and stress distribution. In particular, the subducted Pacific slab in the mantle transition zone acts as a gravitational sinker, enhancing crustal compression along the eastern margin of the peninsula.

The NE Tibet experienced complex and distinct basin developments and uplifts in different areas. However, the reasons for such distinct surface deformation and their relationship to deep crustal geodynamic processes are not well understood. Here, we obtain a crust model of NE Tibet by jointly inverting Rayleigh wave ellipticity and phase velocity. Our results reveal that deep crustal strength contrasts across NE Tibet play an important role in controlling basin development. Extrusion of the significantly weak Qilian crust is obstructed by rigid Alxa block, resulting in deep foreland basin with dramatic topographic step. In contrast, the relatively weak crust of Longzhong absorbs outward extrusion of NE Tibet within a wide transition zone, leading to small intermontane basins. Furthermore, the systematic thinning of basins from north to south around the western Ordos Block demonstrates the tectonic transformation from extension to compression due to expansion of NE Tibet since the late Miocene. Plain Language Summary In this study, we obtain a high‐resolution model of NE Tibet by jointly inverting Rayleigh wave phase velocity and ellipticity (the radial‐to‐vertical amplitude ratio), which provides complementary constraints to the shallow structure. Our results show a clear correlation between velocity variations in the deep crust and basin structures at the surface. We infer that the extrusion of mechanically weak mid‐to‐lower crust of Qilian is obstructed by the strong Alxa block, leading to the steep topography and deep foreland Hexi Basin. To the east, in contrast, the outward extrusion of Songpan‐Ganzi is absorbed in a wide range by the relatively weak Longzhong region, developing gently sloping topography and small intermontane basins. Furthermore, the significant structural differences of rift basins from north to south around the western Ordos likely result from tectonic regime transformation induced by the continuous expansion of NE Tibet since the late Miocene. Our results improve the understanding of how deep crustal geodynamic processes influence surface uplift and basin developments in the expanding NE Tibet. Key Points A high‐resolution 3‐D crustal model of NE Tibet is obtained by joint inversion of Rayleigh wave ellipticity and phase dispersion We infer that deep crust extrusion and strength differences across plateau boundaries control distinct surface deformation in NE Tibet The systematic thinning of basins in west Ordos indicates tectonic regime transformation due to expansion of Tibet since Miocene

Crack formations in concrete may cause major damages in concrete structures. These damages require extensive maintenance work and thus have high costs. This paper addresses issues such as what causes cracks in concrete structures and how does the appearance of cracks look like with respect to an applied load? Can the appearance, distance, and size of the crack tell us something about crack initiation and propagation, or is it just by pure coincidence that cracks occur in structures as they do? This research work investigated the effect of external factors such as load variables, time, the dimensions of the beam and the relative humidity on crack formation. Internal factors that have been investigated are the various constituents of the concrete, and how various levels of these constituents have an impact on cracking. In addition, the influence of concrete quality, tensile reinforcement, shear reinforcement, and anchoring reinforcement was investigated. The paper presents technical calculations, where both the bending moment and shear forces are included in the analysis to determine how crack formations will propagate in the beam as a function of the applied loads. The first part of the paper deals with the theoretical factors that influence cracking in concrete. The second part deals with the calculations of crack formation in concrete. The results show how the cracks propagate in the x and y directions as a function of the load being applied.

In hypersonic flight the shock wave and turbulent boundary layer interaction (STBLI) sharply increases wall heat transfer that intensifies the aerodynamic heating problems. In this work the STBLI is modelled by compression ramp flow with a Mach number of 5, a Reynolds number based on momentum thickness of 4652 and a wall to recovery temperature ratio of 0.5. The aerodynamic heat generation and transport mechanisms are investigated in the interaction based on theoretical analysis and direct numerical simulation (DNS) that agrees with previous studies. A prediction correlation of wall heat flux in STBLI is deduced theoretically and validated by some representative data including the present DNS, which improves the prediction accuracy and can be applied to a wider $Ma$ range compared with the canonical Q-P theory. The correlation indicates that the sharp increase of wall heat transfer in the STBLI can be explained by the boundary layer compression and the convection transport enhancement. Based on the DNS results, the aerodynamic heat generation and transport mechanisms are revealed in the separation, recirculation and reattachment zones in the STBLI. From this perspective, the peak heat flux can be further explained by the enhancement of near-wall turbulent energy dissipation, compression aerodynamic heat generation and the near-wall turbulent transport. The generation and transport of compression aerodynamic heat reveal the underlying mechanism of the strong correlation between the peak heat flux ratios and the pressure ratios in STBLIs.