Shear Model Research Articles

A Study of {10-12} Twinning Activity Associated with Stress State in Mg-3Al-1Zn Alloy during Compression

An eight-sided prism sample, obtained from a hot-rolled AZ31 magnesium alloy sheet, was compressed at room temperature along the transverse direction to investigate the influence of local strain on twinning behavior using electron backscatter diffraction (EBSD) measurements, hardness distribution, and metallographic observations. The octagonal surface of the sample was divided into distinct regions based on hardness distribution and metallographic observations. Combined analysis of the Schmid factor (SF) and the strain compatibility factor (m’) was employed to study twin variant selection. Basal on SF ratio distribution, the Schmid factor criterion, can predict over 75% of observed twin variants in regions A and D (normal stress samples). In contrast, 64% of twin variant selection behavior in region C (shear stress sample) can be effectively explained using a pure shear model. Twin variants with high strain compatibility factors may prefer activation to reduce stress concentration. The strain compatibility factor is more appropriate than the Schmid factor for analyzing the effect of local strain on the selection behavior of twin variants.

Elasto-Plastic Seismic Shear Distributions of Frame-Wall Structures

ABSTRACT In this study, theoretical and numerical methods were used to research seismic shear distributions of frame-shear wall structures under elasto-plastic conditions. The shear distributions of frame-shear walls were analyzed based on a simplified elasto-plastic analysis model of flexural shear. Based on a preliminary project, three groups of 2D models with different stiffness eigenvalues were designed and used to compare the shear distributions of whole structures and frames. The characteristics of the shear distributions of structures and frames and the development of plastic hinges were analyzed, and the rationality of shear adjustment based on Chinese standards was discussed from the perspectives of structural design, seismic performance and collapse resistance. The results revealed obvious differences between shear distributions of structures caused by strong vs. frequent earthquakes. For strong earthquakes, the shear distributions tended to be evenly distributed with respect to height, while the shear force of the bottom story was significantly larger than that of the upper stories. This was mainly caused by the redistribution of plastic internal forces due to the development of plastic hinges. The shear adjustment of the frame usually affected the reinforcement in the beams rather than in the columns, which contradicted the design concept of strong columns – weak beams. Additionally, shear adjustment had little effect on the seismic performance and collapse resistance of structures. This paper suggests that by ensuring the ability of strong columns, weak beams and plastic hinges to rotate, shear force adjustment can be prevented.

A numerical model database for rapid seismic damage assessment of typical regular reinforced concrete frame structures in urban building clusters

A vast city usually encompasses hundreds of thousands or even millions of buildings, majority of which are regular buildings with typical structural configurations. In the seismic damage simulation of cities, efficient and reliable simplified models are required to represent these buildings. A numerical model database of typical regular reinforced concrete (RC) frame structures was developed, utilizing shear models to simulate these RC frame structures. In contrast to existing shear models that are automatically generated based solely on the fundamental rules regulated by the theories of structures and the design codes, the shear models in this study were calibrated using refined numerical models to guarantee precise depiction of RC frame structures. The effects of reinforcement corrosion and the year of construction on structural performance were also considered. First, 108 RC frame structures were designed with typical configurations, strictly adhering to the regulations of design codes. Second, the refined models of the RC frame structures were established with modified material parameters to account for reinforcement corrosion, resulting in 540 refined models. Afterward, the parameters of each shear model were calibrated through cyclic pushover analysis of the corresponding refined numerical model. Finally, the characteristic points of the shear models were further modified to consider the different redundant capacities of the structures constructed in three time phases due to the update of design codes, by which a simplified numerical model database containing 1620 shear models was developed. The models' accuracy in predicting fundamental periods and seismic damage states was verified by comparing them to the refined models and three real RC frame buildings. The effects of the reinforcement corrosion and year of construction on the seismic damage states of the RC frame structures were also discussed. The developed numerical model database can be utilized for the seismic damage assessment of RC frame structures in urban building clusters.

Softened membrane model for shear of ultra-high-performance concrete (SMM-UHPC)

Understanding the shear behavior of Ultra-High-Performance (UHPC) is crucial to prevent undesired responses that could be induced by diagonal shear cracks. Hence, the ability of analytical models to predict shear responses of UHPC members is of paramount importance, which is addressed in this paper by the Softened Membrane Model (SMM). Since the SMM is a two-dimensional shear modeling framework developed for reinforced concrete, a parametric investigation was conducted to assess its suitability for UHPC, namely SMM-UHPC. Through this assessment, a softening coefficient for the biaxial behavior of UHPC was developed and new constitutive laws were integrated in SMM. Comparisons with shear panel tests were used to evaluate the accuracy of SMM-UHPC and quantify the significance of key model parameters. Sensitivity analyses showed that the decomposition between biaxial and uniaxial strain fields, which is used in SMM to capture the Poisson effect, has a negligible influence on UHPC shear. Combining experimental and analytical data, the tensile localization strain was identified to be of most significance for predicting the shear stress-strain response of UHPC.

Reduced model for H-mode sustainment in unfavorable ∇B drift configuration in ASDEX Upgrade

A recently developed reduced model of H-mode sustainment based on interchange-drift-Alfvén turbulence description in the vicinity of the separatrix matching experimental observations in ASDEX Upgrade has been extended to experiments with the unfavorable ∇B drift. The combination with the theory of the magnetic-shear-induced Reynolds stress offers a possibility to quantitatively explain the phenomena. The extension of the Reynolds stress estimate in the reduced model via the magnetic shear contribution is able to reproduce the strong asymmetry in the access conditions depending on the ion ∇B drift orientation in agreement with experimental observations. The Reynolds stress profile asymmetry predicted by the magnetic shear model is further extended by comparison with GRILLIX and GENE-X simulations matched with comparable experiments in realistic X-point geometry. The predictions of the radial electric field well depth and its difference between the favorable and unfavorable configurations at the same heating power from the extended model also show consistency with experimental measurements.

Highly Efficient Hemostatic Cross-Linked Polyacrylate Polymer Dressings for Immediate Hemostasis.

A traumatic hemorrhage is fatal due to the great loss of blood in a short period of time; however, there are a few biomaterials that can stop the bleeding quickly due to the limited water absorption speed. Here, a highly absorbent polymer (HPA), polyacrylate, was prepared as it has the best structure-effectiveness relationship. Within a very short period of time (2 min), HPA continually absorbed water until it swelled up to its 600 times its weight; more importantly, the porous structure comprised the swollen dressing. This instantaneous swelling immediately led to rapid hemostasis in irregular wounds. We optimized the HPA preparation process to obtain a rapidly water-absorbent polymer (i.e., HPA-5). HPA-5 showed favorable adhesion and biocompatibility in vitro. A rat femoral arteriovenous complete shear model and a tail arteriovenous injury model were established. HPA exhibited excellent hemostatic capability with little blood loss and short hemostatic time compared with CeloxTM in both of the models. The hemostatic mechanisms of HPA consist of fast clotting by aggregating blood cells, activating platelets, and accelerating the coagulation pathway via water absorption and electrostatic interaction. HPA is a promising highly water-absorbent hemostatic dressing for rapid and extensive blood clotting after vessel injury.

Micromechanical response of an electrodeposited NiP metallic glass by pillar compression under extreme conditions

In this work, the mechanical properties of pulse electrodeposited amorphous nickel phosphorous (NiP), with ∼16 wt% P, was investigated for an improved understanding of the deformation behavior of metallic glasses at extreme conditions, particularly at the microscale. Upon decreasing the temperature to sub-ambient, both the yield strength and the shear band density increase. While the change of yield strength with temperature can be well explained by a cooperative shear model, the increase in the number of shear bands can be related to an increase in potential sites for activation of shear transformation zones due to the enhanced structural heterogeneity at lower temperatures. This, however, hinders the percolation of deformation units and leads to a decrease in the shear band propagation speed, from ∼50 nm/s at 295 K to ∼20 nm/s at 195 K. By testing micropillars across seven orders of magnitude in strain rate, a two-stage strain rate sensitivity is observed, from nearly negligible at the quasi-static range (m1 = 0.001 ± 0.002 for 10−3 s−1 to 10−1 s−1) to highly positive at dynamic high strain rate range (m2 = 0.02 ± 0.004 for 1 s−1 to 1000 s−1). This transition implies a change in the yield-controlling process, from the diffusion-assisted relaxation at quasi-static conditions to the rate of energy barrier crossing of shear transformation zones at high strain rates. These findings highlight several distinctive features of microscale metallic glasses, including the reduced shear band velocity at sub-ambient temperature and the two-stage strain rate sensitivity.

Autoclaved aerated concrete masonry wallettes strengthened using TRC overlay under out-of-plane load

The objective of this study is to assess the out-of-plane flexural responses of autoclaved aerated concrete (AAC) masonry wallettes externally strengthened with textile reinforced concrete (TRC) overlay. This method can be applied as a retrofitting technique for existing AAC masonry walls or as a constructive technique for new constructions. Sixteen AAC masonry specimens (shear span ratio = 5) were subjected to monotonic four-point bending loads. The design variables were the textile types and number of textile layers (reinforcement ratio). The load–deflection responses and corresponding flexural performances of specimens were assessed to quantify the influences of different test parameters. Results showed that the higher tensile strength of TRC would change the failure mode of AAC masonry wallettes from bending to shear. Finally, according to the different failure pattern observed in the tests, flexural and shear models available in the literatures were examined to assess their applicability to predict the load-carrying capacity of AAC masonry wallettes strengthened with TRC.

Adjoint Waveform Tomography for Crustal and Upper Mantle Structure of the Middle East and Southwest Asia for Improved Waveform Simulations Using Openly Available Broadband Data

ABSTRACT We present a new model of radially anisotropic seismic wavespeeds for the crust and upper mantle of a broad region of the Middle East and Southwest Asia (MESWA) derived from adjoint waveform tomography. The new model enables fully 3D simulations of complete three-component waveforms and provides improved fits that were not possible with previous models. We inverted over 32,000 waveforms from 192 earthquakes recorded by over 1000 openly available broadband seismic stations from permanent and temporary networks in the region with highly uneven coverage. Inversion iterations proceeded from the period band 50–100 s in six stages and 54 total iterations reducing the minimum period to 30 s. Our final model, MESWA, improves waveform fits compared to the starting and other models for both the data used in the inversion and an independent validation set of 66 events. Restitution tests indicate that the model resolves features in the central part of the model to depths of about 150 km. The new model reveals tectonic features imaged by other studies and methods but in a new holistic model of anisotropic shear and compressional wavespeeds (VS and VP, respectively) covering a larger domain with smaller scale length and amplified features. Examples include low crustal VS in the Tethyan belt and low mantle VS following divergent (Gulf of Aden, Red Sea) and transform (Dead Sea fault) margins of the Arabian plate. Low VS is imaged below Cenozoic volcanic centers of the Mecca–Madina–Nafud Line, Arabian Peninsula, and the Türkiye–Iran border region. Elevated VS tracks Makran subduction under southeast Iran with near vertical dip. MESWA could be used as a starting model for further improvements, say, using waveforms from in-country seismic networks that are not currently openly available and/or smaller-scale studies targeting a shorter period. The model could be used to improve earthquake hazard studies and nuclear explosion monitoring.

Parameter optimization and tractive performance evaluation of tracked miner

Enhancing the traction performance of the tracked miner is crucial for ensuring smooth seabed operation. In this study, an experimental device for the interaction between track and deep-sea sediments was designed, aligning with the walking process of the tracked miner. The primary and secondary order of the influence of the driving parameters on the mechanical properties of the undisturbed deep-sea sediments was determined by an orthogonal test, and the pressure-sinkage model and shear stress–displacement model were constructed. Building upon the shear model and the vehicle ground mechanics theory, the driving mechanics model of the tracked miner in the seabed environment was derived, and the track structure and parameter optimization method were proposed. The results show that the experimental factors significantly influence the mechanical properties of undisturbed deep-sea sediments, with the order of influence being grounding pressure > grouser height > shear rate > track shoe length > track shoe width; By optimizing the structural parameters of the “Kunlong 500” tracked miner, the drawbar pull increased by 29.1%, and the sinkage depth reduced by 12.8%. This study quantitatively analyzes the influence of structural parameters in driving performance on the sinkage and shear characteristics of deep-sea sediments, and proposes a new method for optimizing the tractive parameters. It provides new insights for achieving efficient and environmentally friendly movement of tracked miner on the seabed.

Estimating the contribution of thermal processes to generation of seismicity in the junction zone of the Chuya Depression and the Kyrgyz Ridge of the Northern Tien Shan

This paper presents the attempt to estimate the contribution of thermal processes in the Earth’s crust to the generation of seismicity by the example of the seismically active region of the Chuya depression and the Kyrgyz ridge of the Northern Tien Shan. For this purpose, we use the models of temperature, petrophysical characteristics, and elastic moduli constructed in the previous works. The silica content model based on seismic tomography data is used to build a lithotype model. The constructed thermal conductivity model is utilized, along with the temperature model, to create a depth model of heat flow density. Based on the density, elastic moduli, and temperature models, the shear and thermoelastic stress models in the rocks are constructed. Their comparison with the distribution of earthquake hypocenters suggests that on the scale of the seismically active zone of the Chuya depression and the Kyrgyz ridge of the Northern Tien Shan, seismicity is mainly determined by the thermomechanical effect resulting from the hot ascending flow of acid magma from the upper mantle beneath the Muyunkum–Narat median mass.

On the problem of solvability of nonlinear boundary value problems for shallow isotropic shells of Timoshenko type in isometric coordinates

The solvability of a boundary value problem for a system, which describes the equilibrium state of elastic shallow inhomogeneous isotropic shells with loose edges referred to isometric coordinates in the Timoshenko shear model and consists of five non-linear second-order partial differential equations under given non-linear boundary conditions, is studied. The boundary value problem is reduced to a nonlinear operator equation for generalized displacements in Sobolev space, the solvability of this equation is established with the help of the contraction mapping principle.

Seismic Damage Assessment of Reinforced Concrete Slab-Column Connections—Review of Test Data, Code Provisions and Analytical Models

Reinforced concrete slab-column connections are vulnerable to punching shear failure when subjected to combined gravity and lateral loadings during earthquakes. Over the years, many experimental campaigns have been conducted and assessed the seismic performance of flat slabs. The experimental findings were used to derive empirical equations for the design provisions. The paper aims to provide a detailed description of the code development for seismic punching shear. Two current code provisions (ACI 318-19, EC 2 & EC 8-2004) for seismic punching shear are presented and discussed. Relevant and updated experimental data of interior slab-column connections without and with shear reinforcement are selected and assessed against the current design provisions with a focus on key response parameters such as the drift ratio and the gravity shear ratio. The ACI 318-19 limit drift line is considered to assess the lateral deformation demand for the connections with respect to the updated database. The gravity shear ratio is shown to have a considerable impact on the limit drift ratio of slab-column connections without shear reinforcement. The majority of the test specimens with no shear reinforcement experienced punching shear failure, followed by the specimens which showed a combined flexure–punching failure. Punching shear failures occurred for a range of gravity shear ratios of 0.2 to 0.9, while all combined flexure–punching shear failures occurred for gravity shear ratio values below 0.5. The shear-reinforced concrete slab-column connections can achieve much higher drift ratios. Most of the slabs were reinforced with shear studs, particularly in the range of gravity shear ratios of 0.4 to 0.6. Most test specimens failed by flexure for gravity shear ratio values of 0.1 to 0.7, followed by the specimens which failed in combined flexure–punching for gravity shear ratio values that ranged from 0.3 to 0.9. Finally, the available numerical and analytical models for seismic punching shear are presented with the objective of observing their potential strengths and limitations.

Machine learning-based evaluation of punching shear resistance for steel/FRP-RC slabs

With the emergence of fiber-reinforced polymer (FRP) reinforcement as a substitute for conventional steel reinforcement, different design codes have been developed to account for the different mechanical properties of the FRP, specifically the elastic modulus. The ACI 440.11-22, CSA/S806-12, and JSCE-97 are well-known standards for FRP-reinforced concrete structures. In particular, these design standards show significant variations in estimating the punching shear resistance and accounting for the elastic modulus. This study provides a statistical and machine learning-based evaluation of the punching shear models in design standards. An Artificial neural network (ANN) framework is used to develop a generalized punching resistance model of flat slabs reinforced with steel and FRP bars utilizing a large experimental dataset with 539 tests. The study presents a parametric study to examine the effect of different factors on the punching shear strength. The parametric study provided a graphical presentation and comparison between the design models and the developed ANN model.

A Class of Efficient Sixth-Order Iterative Methods for Solving the Nonlinear Shear Model of a Reinforced Concrete Beam

In this paper, we present a three-step sixth-order class of iterative schemes to estimate the solutions of a nonlinear system of equations. This procedure is designed by means of a weight function technique. We apply this procedure for predicting the shear strength of a reinforced concrete beam. The values for the parameters of the nonlinear system describing this problem were randomly selected inside the prescribed ranges by technical standards for structural concrete. Moreover, some of these parameters were fixed taking into consideration the solvability region of the adopted steel constitutive model. The effectiveness of the new class is also compared with other current schemes in terms of the computational efficiency and numerical performance, with very good results. The advantages of this new class come from the low computational cost, due to the existence of an only inverse operator.

Investigating the structure under the Pingting Terrace from the co-seismic surface rupture of the 2022 Guanshan earthquake

AbstractOn September 17th and 18th, 2022, shallow earthquakes with magnitudes of 6.6 (ML) and 6.8 (ML) occurred in the eastern Taiwan Longitudinal Valley, which marks the collision zone between the Philippine Sea plate and the Eurasian plate, and led to noticeable surface deformation and ruptures within 70 km. This study primarily focuses on the southernmost section of the rupture zone—the Pingting Terrace. Surface rupture locations and behaviors correspond to changes in topography, providing mutual confirmation that the deformation behavior of Pingting Terrace is complex. Based on the distribution of surface ruptures and topography changes, this study roughly divides the Pingting Terrace into northern and southern segments, using the central concave feature as a boundary. The Riedel shear model analysis results show that the principal shear directions in the northern and southern segments are N–S trending and azimuth 20°, respectively. The maximum principal stress orientations are around 135° for the northern and 155° for the southern segments. These findings align with the fault mechanical investigation of the Lichi Mélange in the northern Muken River area of the Pingting Terrace. This suggests spatial changes in shear zone orientations within the Lichi Mélange, which contribute to developing pressure ridges due to transpressional forces. As a result, the Pingting Terrace experiences rapid uplift, causing the Luliao River to migrate southward into the Beinan River, while the eastern Beinan River turns to the eastward edge of the Pingting Terrace.

Pole Allocation Applied to Two Buildings Connected by Joint Damper

For two adjacent buildings connected by a joint damper, an inverse problem is formulated based on the pole allocation method in control theory. The structural system is simplified as a two-degrees-of-freedom (2-DOF) lumped-mass damped shear model. The unified governing equation, which expresses the relationship between an assigned control target and the structural parameters for an earthquake-resistant building, seismically isolated building, or passively controlled building, is extended to structural control using a joint damper. The introduced equation automatically constrains the variations in the structural parameters under the assigned modal properties. The integration of the pole allocation method and fixed-point theory directly estimates the additional damping effect on the target buildings from the optimum capacity of the joint damper, which improves the trial-and-error steps at the preliminary design stage. The past fixed-point theories do not provide the additional damping effect but the optimum damping coefficient of the joint damper. The present study directly links the additional damping with the damping of the joint damper. Numerical examples are used to verify the theoretical integration using a 20-DOF building model wherein two 10-DOF models are connected by a joint damper between the top lumped masses.

A Study on the Softening Shear Model of the Energy Pile–Soil Contact Surface

In this paper, a finite element numerical model of thermal-hydro-mechanical of energy piles under multi-layer geological conditions was established, and field tests of ultra-long energy pile (1000-mm-diameter, 44-m-long) were carried out to reveal the temperature distribution and mechanical properties of energy pile under typical working conditions. Based on the analytical results, a softening shear model of the energy–soil interface under the condition of large shear displacement was proposed with the load transfer method, and the reliability of the model was verified. The model can simulate the shear–displacement relationship of the pile–soil interface under different geological conditions.

Design of UHPC prestressed girders for shear

AbstractBreakthrough technology of ultra‐high‐performance concrete (UHPC) introduced in the 1990s exhibits several exceptional mechanical properties that are advantageous in elements of bridge applications. Extensive research has aimed to industrialize UHPC and develop design models. This paper investigates several design models for shear, including a unified approach with that of conventional concrete based on the modified compression field theory (MCFT). An experimental database of UHPC prestressed concrete girders subjected to shear failure is compiled to evaluate model accuracy and a reliability study is conducted to establish appropriate safety factors. The analysis demonstrates that the proposed MCFT‐based model aligns well with experimental results, exhibiting a suitable level of conservatism for design. A reliability assessment of a typical prestressed girder designed according to Canadian Standards Association building and bridge loadings is performed, resulting in a structural reliability evaluation against a target reliability index. The study recommends specific strength reduction and safety factors for design approaches using UHPC.

Machine learning approaches for stability prediction of rectangular tunnels in natural clays based on MLP and RBF neural networks

In underground space technology, the issue of tunnel stability is a fundamental concern that significantly causes catastrophe. Owing to sedimentation and deposition processes, the strengths of clays are anisotropic, where the magnitudes of undrained shear strengths in the vertical and horizontal directions are different. The anisotropic undrained shear (AUS) model is effective at considering the anisotropy of clayey soils when analyzing geotechnical stability issues. This study aims to assess the stability of rectangular tunnels by adjusting the dimensionless overburden factor, cover-depth ratio, and width-depth ratio in clay with various anisotropic strength ratios. The stability analysis of these tunnels involves employing finite element limit analysis and the AUS model to identify the planes of soil collapse in response to the aforementioned variations. In addition, this study presents the development of soft-computing models utilizing artificial neural networks (ANNs) to forecast the stability of rectangular tunnels across various combinations of input parameters. The findings of this study are presented in the form of design charts, tables, and soft-computing models to facilitate practical applications.