Force-displacement Relationship Research Articles

Analysis of disturbance factors of magnetorheological damper in continuous impact buffer system

Abstract Magnetorheological (MR) impact buffering systems are widely used in vehicle suspensions, bridge damping, and aircraft landing gear due to their excellent buffering performance and rapid response time. However, under the condition of high-speed continuous impact, magnetorheological damper (MRD) operate in complex environments where various internal and external uncertainties can negatively affect control performance. This paper analyzes the impact of disturbance signals on MR buffering systems and explores control strategies to mitigate these effects. First, we established a hysteresis model based on experimental data and identified parameters using a genetic algorithm to determine the influence of hysteresis disturbances. Next, we developed a temperature model based on the thermal characteristics of SG-MRF2035 magnetorheological fluid, fitting the relationship between temperature and dynamic viscosity to identify temperature disturbances. The results showed that when disturbances were considered, the system exhibited higher peak damping forces and a deviation from the desired "platform effect" in the damping force-displacement relationship. Finally, we applied an Active Disturbance Rejection Control(ADRC) strategy, which effectively compensated for the hysteresis and temperature disturbances, enhancing the system's robustness. Compared to PID control, the ADRC-controlled system demonstrated lower peak damping forces and a damping force-displacement relationship closer to the desired platform effect.

In‐Plane Crashworthiness of Gradient Curved‐Walled Honeycombs: Experimental, Numerical Simulation, and Theoretical Analysis

Honeycombs are widely used in engineering protection, while the gap between peak and mean stresses remains to be narrowed, and the interaction effects among walls are weak. To break these limits, gradient curved‐walled honeycombs have been proposed recently. However, their in‐plane crashworthiness has never been studied, which restricts the actual applications in complex load environment. For this purpose, this article adopts experiments, finite‐element simulations, and theoretical analysis to reveal in‐plane crash performance of gradient curved‐walled honeycombs. Quasistatic and dynamic experiments are carried out for 3D‐printed honeycomb specimens made of 316L stainless steel, and numerical simulations are conducted by ABAQUS/Explicit. Compared to traditional straight‐ and curved‐walled honeycombs, gradient curved‐walled honeycombs display stabler deformation mode and more efficient mechanical response. Their EA and SEA are respectively 25.5% and 6.4% larger than straight‐walled honeycombs, and their energy absorption and force efficiencies are nearly 2.4 and 5.3 times larger, respectively. On this basis, plastic hinge model with high accuracy has been established, to derive the analytical solutions of their force–displacement relations. This work extends the comprehensive properties and application prospects of gradient curved‐walled honeycombs and sets an example to develop plastic hinge analysis with effective simplification and desirable accuracy on complex‐shaped structures.

Bandgap characteristics of periodic mindlin plates under arbitrary boundary conditions via the Spectral Element Method

This paper employs the Spectral Element Method (SEM) to investigate the bandgap characteristics in periodic plates under arbitrary boundary conditions. The spectral element model of Mindlin plate is derived via force-displacement relations. The convergence of the SEM results for a single plate structure is validated by comparing them with the Finite Element Method (FEM) results at distinct mesh resolutions, demonstrating that SEM maintains high computational accuracy even with fewer elements. Like FEM, the spectral element matrix is assembled to establish the spectral element model of the periodic plate. The influences of boundary conditions, substructures, material properties, and geometric dimensions on the bandgap characteristics in the periodic plate are explored.

Effect of Lead Core Heating on Residual Displacements of Lead Rubber Bearings Under Bi-Directional Earthquake Excitations

ABSTRACT This paper investigates the variation in residual displacements (RDs) of lead rubber bearings (LRBs) subjected to bi-directional earthquake excitations when lead core heating effect is of concern. Accordingly, several dynamic analyses were conducted considering isolator response with and without lead core heating effect. A wide range of isolation system properties, several characteristic strength to weight ratios, isolation periods and yield displacements were considered to construct the bi-linear force-displacement relations of LRBs. Ground motions were selected to represent different magnitudes and pulse characteristics. Results were also used to assess the efficacy of code suggested equations to estimate RDs of seismic isolators.

Combined effect of track-bridge interaction on the dynamic response of a simply supported railway bridge

In this work, the objective is to understand the effect of the nonlinear behaviour of the ballasted track, or the mechanism of vertical and horizontal track-bridge interaction behaviour, on the dynamic response of a simply supported railway bridge, carrying a single ballasted track characterized by a fractional order viscoelastic nonlinear Winkler foundation type, and acted by a moving train load with constant speed. The main feature of the model is that the horizontal and vertical interactions at the interface between the bridge deck and the ballasted track, composed by rails, sleepers and ballast, is introduced through a nonlinear cubic force-displacement relation, schematizing the nonlinear stiffness, plus fractional derivative term for simulating the rail bed’s damping behaviour and a system of horizontally orientated spring-damper elements. By applying the two numerical methods, fourth-order Runge-Kutta method and Finite Difference Method, the validation of the dynamic behaviour of the rail-bridge system is performed, and numerical simulations demonstrate the accuracy of the proposed theoretical model for predicting the real behaviour of the studied bridge taking into account the track-bridge interaction effect. The influence of the fractional-order derivative and the distance between sleepers on the critical velocities, associated with resonance effects, is also addressed.

Electrochemical–Mechanical Coupling Is Essential to Predict Solid-Electrolyte Fracture during Li-Metal Plating

Lithium propagation through the solid electrolyte is a main failure mechanism for the all-solid-state lithium-anode battery. Preceding the lithium penetration is a crack formation, i.e., fracture, in the solid electrolyte, providing a passage for lithium to preferentially grow during plating [1,2], due to the field-enhancement effect at the lithium tip [3]. Therefore, it is vital to understand both the crack initiation and lithium propagation for the prediction of the system behaviors, as well as the optimization of the interfacial design. Mathematical modeling is a key tool for the fundamental understanding of the undergoing physical processes.There are several solid-electrolyte fracture models in the literature, but they often treat none or a limited amount of the electrochemical–mechanical couplings. This is despite the fact that high stack pressure, as well as the stress build-up at the lithium/electrolyte interface, necessitate the consideration of stress in the thermodynamic, kinetic, and transport constitutive and governing equations. In particular, the Butler–Volmer equation (or alternative interfacial kinetic expression) must be modified to take into account the stress effects on the reaction kinetics. Furthermore, the incorporation of an appropriate lithium mechanical constitutive behavior is equally important for an accurate depiction of the system behaviors.Consequently, we aim to build a model that brings together (1) rigorous electrochemical–mechanical couplings and (2) appropriate lithium properties at the battery-application length scale to study the crack initiation during battery operation. It features an isolated Gaussian-curved lithium peak in perfect contact with the lithium-lanthanum-zirconium-oxide (LLZO) solid electrolyte. LLZO is treated as an elastic solid, while lithium is modeled as a non-Newtonian fluid. The pseudo-viscosity of lithium is carefully extracted from Haslam et al.’s thin-film compression experiment [4] using the force–displacement relationship in the squeeze-flow experiment. Current flow in the LLZO is treated with Ohm’s law, and the model is solved for a steady-state application of current.Preliminary results show that electrochemical–mechanical couplings strongly influence the model outputs. The stress distribution is intimately intertwined with the interfacial current distribution, which dictates the fracture initiation. Other key sensitivities include the constitutive model for the lithium metal and the asperity geometry. We also aim to present model parameter values that produce an experimentally observed fracture current density of around 1 mA/cm2.

A Revised Abaqus® Procedure for Fracture Path Simulation Based on the Material Effort Criterion.

This paper presents the results of computer simulations of fracture in three laboratory tests: the three-point bending of a notched beam cut from sandstone, the pull-out test of a self-undercutting anchor fixed in sandstone, and the pull-out test of a bar embedded in concrete. Five material failure criteria were used: Rankine, Coulomb-Mohr, Drucker-Prager, Ottosen-Podgórski, and Hoek-Brown. These criteria were implemented in the Abaqus® FEA system to work with the crack propagation modeling method-extended finite element method (X-FEM). All criteria yielded similar force-displacement relationships and similar crack path shapes. The improved procedure gives significantly better, close-to-real crack propagation paths than can be obtained using the standard subroutines built into the Abaqus® system.

A contact-based constitutive model for the numerical analysis of masonry structures using the distinct element method

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.

Force-displacement relation for lumped plasticity model of compact square concrete-filled steel tube columns

Integration of steel and concrete benefits in square concrete-filled tube columns (SCFTs) makes them be utilized extensively worldwide. To evaluate the seismic behavior of special moment frames having SCFT columns, an accurate macro-modeling tool with little complexity is necessary. Although the fiber section can consider both linear and nonlinear behavior of SCFT, it fails to allow for deterioration, which is vital in assessing a seismic resisting system. This study proposes a new deterioration tool based on the Ibarra-Krawinkler model for compact SCFT columns using artificial neural networks (ANNs) through numerical simulation. Initially, 96 specimens with variations in geometry, material, and axial loading conditions were simulated in ABAQUS and then were analyzed using displacement control loading protocol to obtain hysteretic curves, which were used to prepare the data sets for training, testing, and validating the neural networks. Finally, the performance of ANN models was evaluated by statistical relations such as regression and mean square error. Through FEMA 356 and Ibarra-Krawinkler approaches, parameters defining linear and nonlinear phases of SCFTs behavior were derived. By employing efficiently trained neural networks, equations predicting the parameters of the deterioration model were established, and the obtained results show the accuracy and efficiency of the proposed model.

Study on unseating prevention for multi-union long simply supported girder bridges under near-fault ground motions

Girder shifting is a common form of seismic damage for girder bridges. Unseating could occur when the displacement of the girder is too large, especially for bridges near faults, because the velocity impulse effect leads to greater displacement responses of structures. Setting metal dampers between girders and piers is a useful way to control the seismic behavior and reduce the risk of unseating. Since metal dampers are inevitably exposed to the erosive service environments, their mechanical properties may degrade due to corrosion. In this paper, a U-shaped metal damper made of stainless steel instead of mild steel (i.e., U-shaped stainless steel damper, which could be named simply as USSSD) is proposed and applied to the seismic reduction design of girder bridges. First, the finite element model (FEM) of the USSSD is built by the ABAQUS, and its force-displacement relationship is obtained based on the skeleton curve, which is fitted by the trilinear kinematic strengthening model. Then, a multi-union long simply supported girder bridge is taken as an example. The FEM of the adopted bridge is established via the Midas Civil to verify the seismic mitigation effect of the proposed USSSD excited by near-fault ground motions. The numerical analyses demonstrate that the unseating may occur without the use of the USSSDs. The relative displacement between the girder and pier is effectively controlled by the USSSDs, and the reduction is more than 50 %. When the bridge is equipped with the USSSDs, both the curvature ductility coefficient of the pier bottom and the maximum drift of the pier tip increase by a limited amplitude, which do not cause additional damage to the piers.

Performance Improvement of Three-Spring Quasi-Zero-Stiffness Isolator by Shape Memory Alloy Damper

Quasi-zero stiffness vibration isolators (QZSI) can effectively resolve the contradiction between the load bearing and the vibration isolation for low-frequency vibration systems. The three-spring QZSI is a classical QZSI. However, constrained by its geometrical relationship, the working stroke of the QZSI is limited, and the isolation performance will deteriorate when the displacement response is significant. To solve this question, the shape memory alloy (SMA) damper, characterized by lower secondary stiffness, partially replaces the positive-stiffness spring of the three-spring QZS isolator to widen its effective working stroke, which forms a novel SMA-QZSI. Based on a piecewise linear constitutive model of SMA, a theoretical model of the force–displacement relationship of SMA-QZSI is established. Subsequently, the approximate analytic amplitude–frequency response equation of the non-smooth nonlinear SMA-QZSI system under harmonic excitation is obtained by the average method and verified numerically. In addition, the effects of mechanical parameters of SMA springs and external excitation parameters on mechanical behaviors and low-frequency isolation performance of the SMA-QZSI isolator are discussed. Finally, the static and dynamic experiments of SMA-QZSI are conducted to verify its force–displacement relationship and isolation performance. The results show that the proposed SMA-QZSI has remarkable low-frequency vibration isolation performance.

Advancing earthquake resistance: Hybrid retrofitting of RC frames with FRP and TDS

Traditional and technological retrofitting methods have been proposed over time to enhance earthquake resistance in structures. Friction-type dampers have attracted considerable interest from both researchers and the construction industry because of their versatility in retrofitting, quick installation, and non-destructive characteristics. Moreover, the integration of damping systems with various retrofitting elements and the resulting impact of these hybrid systems on building performance have consistently been subjects of interest. This study involved the construction of three identical half-scale reinforced concrete (R.C) frames. One frame served as the reference (REF), the second was wrapped with Fiber Reinforced Polymers (FRP) material (REF-FRP), and the third was retrofitted using both FRP wrapping and the developed Technological Damper System (TDS-FRP). Quasi-static cyclic experiments were performed on the three structural frames, providing force-displacement and force-rotation relationships. The acquired data were then used to assess the damage states of the frames according to the Turkish Building Earthquake Code (TBEC 2018), and energy consumption rates were determined. Moreover, Finite Element Method (FEM) analyses were performed on REF, REF-FRP, and TDS FRP frames to derive force-displacement relationships, which were subsequently compared with experimental findings. The experiment results indicate that the horizontal load-carrying capacity of the TDS-FRP frame increased by 76 % to 122 % compared to the REF frame, while the REF-FRP frame showed a maximum increase of 14 %. Additionally, the cumulative energy consumption capacity of the REF-FRP frame increased by a maximum of 42 % compared to the REF frame, and the TDS-FRP increased between 51 % and 156 %. At a 1 % drift ratio, shear cracks at the beam ends and column-beam intersections of the REF frame were observed to be significantly reduced in the REF-FRP frame and eliminated in the TDS-FRP frame. Additionally, upon reaching a 3 % drift ratio, it was observed that the TDS-FRP frame remained within acceptable limits as per TBEC 2018, whereas the REF and REF-FRP frames exceeded the advanced damage limit. Additionally, it has been observed that the results obtained from FEM analyses coincide with the experimental results. In this context, the TDS-FRP hybrid application can be considered as an effective and alternative solution for the R.C buildings.

Theoretical nonlinear force-displacement constitutive model of triangular-plate steel damper

Utilizing the inelastic deformation of a steel damper to dissipate seismic energy and control structural damage is a prevalent design strategy in a passive control field. Such a design strategy requires an explicit force-displacement constitutive model of the steel damper in both the elastic and plastic deformation phases. Currently, the nonlinear force-displacement relationship of the steel damper is mainly determined by quasi-static tests or numerical simulations which are generally time-consuming, and there is a lack of a theoretical and straightforward approach to determine the nonlinear force-displacement constitutive model of the steel damper. This study thus theoretically derives the nonlinear force-displacement constitutive model for a commonly used triangular-plate steel damper. The theoretical formula is derived based on the equal curvature assumption commonly applied to the triangular plate and is further modified based on the curvature shape function proposed in this study for the first time. After that, the force-displacement curves obtained from the theoretical formula are compared with those obtained from a large number of numerical simulations and several sets of quasi-static tests. The result shows that the theoretical formula derived based on the curvature shape function can better predict the nonlinear force-displacement curve of the triangular-plate steel damper, which significantly outperforms the theoretical formula derived based on the equal curvature assumption especially as the triangular-plate steel damper has a large plastic deformation. Furthermore, the influence factors of the strain-hardening phenomenon existing in the force-displacement curve of the triangular-plate steel damper are analyzed based on the modified theoretical formula. The result implies that the thickness-to-height ratio of the plate is the most significant factor for the strain-hardening behavior of the triangular-plate steel damper.

Multi-spring model for tubular rocking steel bridge piers subjected to earthquake loading

Recent decades have seen increased interest in using the controlled rocking concept in seismic resisting systems. Unlike conventional systems, where lateral deformation of a member is achieved through the formation of plastic hinges in critical regions, in the rocking systems this is achieved through a gap opening mechanism. Due to gravity load and/or post-tensioning forces, the rocking systems exhibit a self-centering behavior. Conducting a continuum finite element analysis to investigate the seismic response of such a system is quite expensive in terms of computational resources. On the other hand, a simplified macro model using two springs to simulate the gap opening/closing mechanism cannot accurately predict the dynamic response of the system. This study utilizes a multiple-spring model to simulate the nonlinear seismic response of circular tubular steel piers. An efficient optimization procedure based on a genetic algorithm is developed to calibrate the parameters of the springs. The results of continuum finite element analyses are compared with those obtained from the multi-spring model to verify the accuracy of the model. The proposed method is shown to be advantageous for accurately simulating the seismic response of a bridge model subjected to multi-directional ground motions, particularly the hysteretic force-displacement relationship, and dynamic response time history.

Experimental, analytical and numerical study of reinforced concrete beams impacted by deformable bodies at low velocities

In this work, the structural behavior of Reinforced Concrete (RC) beams struck by rigid and deformable impactors at low velocities is studied. An experimental campaign consisting of three-point bending, crushing, and drop-weight tests is carried out to characterize and compare the quasi-static and dynamic behaviors of the colliding bodies. Three repetitions per configuration are tested to obtain reliable data and to check the consistency and repeatability of the proposed experiments. The results are accurately reproduced using Non-Linear Finite Element (NLFE) models to obtain insights regarding the influence of strain rates in the experiments. Furthermore, a simple analytical method that considers the deformability of both bodies through their corresponding force–displacement relationships is presented. The proposed model is observed to predict with a reasonable accuracy the contact force profiles and the deformations of both bodies in almost all of the studied scenarios, while being orders of magnitude faster than the NLFE simulations.

Generative quasi-zero stiffness paradigm for vibration isolation by constraining the constant force with hardening boundaries

Quasi-zero stiffness (QZS) isolators are widely used to mitigate the low-frequency vibration. This paper proposes a new QZS paradigm for vibration isolation utilizing constant force with hardening boundaries (CFHB). Different from the conventional parallel connection of positive and negative stiffness elements, the CFHB directly exhibits the QZS characteristic which is generated when the uniform magnetic field is converted to a non-uniform one. Therefore, it avoids complex assembly and material deformation, and eschews the reliability issues related to stiffness combination. Concretely, the radially magnetized shaft has a uniform area in the middle part which can be distorted by a coaxial sleeve made of high permeability material. A constant magnetic force is generated in this process. Two hardening boundaries formed by two pair of repulsive magnets are applied to constrain the QZS stroke and maintains the working position. The shaft's magnetic field is studied to clarify the filed distribution, and the distortion by the sleeve is simulated by finite element analysis (FEA). The force-displacement relationship of the case study is proven to be continuous and fitted by a polynomial form. The influence of dimension parameters on the performance of vibration isolator is systematically investigated to guide the design. Dynamic differential equation considering Coulomb damping and viscous damping is established and solved applying the Runge-Kutta Method (RKM) to obtain the vibration response. A prototype is fabricated to experimentally validate its performance, demonstrating the QZS properties in quasi-static calibration and the vibration isolation effect under the frequency sweep and periodic excitations. The generative QZS offers a new paradigm with a simple structure, suggesting its substantial potential for practical deployment.

Presence of XX Sex Chromosome Complement Increases Aortic Circumferential Stiffness in Female Mice

Elastin and collagen uniquely adapt to the mechanical demands of high pulsatile pressure in the vascular system in conjunction with the extracellular matrix (ECM). Elastic fiber networks and collagen are affected by component disorganization, leading to an array of vascular diseases and compromised mechanical behavior. It is shown that women than men have accelerated arterial stiffening. Previously, we have shown increased axial and circumferential linearized material stiffness in the carotid arteries of female than male wildtype mice. Whether sex hormones interact with sex chromosomes is unknown. Therefore, we hypothesize that sex hormones interact with sex chromosomes to increase aortic circumferential stiffening in female than male mice. In this study, we used gonadal intact 15-week-old four core genotype mice (n=4-6/group) comprising female (F) and male (M) mice with either XX or XY sex chromosome complement (SCC). Using a tissue puller, we assessed the stress-strain and displacement-force relationship of the abdominal aorta. Briefly, the aorta was cut into 3mm rings and pulled apart to a range of 1300 μm with a velocity of 35 μm/sec. To determine the load-bearing effect of collagen and elastin, collagenase type II (16 units) and elastase (5 units) were used to digest the aortic ring before pulling. Part of the aortic ring was digested for a PCR array of extracellular matrix and adhesion molecules. We observed a leftward shift of stress-strain in XXF than in XXM (P=0.03). A leftward shift of stress-strain was also indicated in XXF than in XYM mice (P=0.004). Displacement-force tests showed a similar effect with a leftward shift in XXF than XXM (P=0.01). A leftward shift of displacement force was also indicated in XXF than in XYM (P=0.004). Aorta digestion with elastase reversed the phenotype, showing a leftward shift of displacement force in XXM than in XXF (P=0.02). Collagenase digestion removed the observed sex differences in stress-strain and displacement force tests. The PCR array comparing XXF and XXM showed increased fold change in Adamts5 (4.2), Emilin (2.2), Icam1 (2.4), and Thbs2 (3). We also observed the downregulation of Cntn1 (0.4), Cntnna1 (0.5), Ecm1 (0.3), and Fbln1 (4). Our data suggested that XX sex chromosome complement, and ECM genes contribute to the structural stiffness of female mice aorta. Our study will contribute to understanding connective tissue diseases, including arterial stiffness, aortic aneurysms, Marfan and Danlos syndrome. HL105400 and HL155841. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Development and validation of an innovative uplift-restraining friction pendulum bearing

This paper presented an innovative uplift-restraining friction pendulum bearing (UR-FPB) to address the limitations of traditional FPBs, which are unable to withstand vertical tensile loads. The UR-FPB is composed of a friction set acting as the horizontal sliding module and an anti-uplift set acting as the vertical uplift-restraining module. Based on this configuration, the study derived the theoretical force-displacement relationships of the UR-FPB, established three solid finite element models in Abaqus, and proposed a hybrid modeling method based on OpenSees. Then the practical effectiveness of this bearing and the credibility of the theoretical analysis models and hybrid numerical models were validated. The theoretical and numerical results demonstrate that the frictional behavior of the UR-FPB in horizontal sliding is characterized by multi-stage hysteresis relationships. The numerical results on the sliding characteristics and the corresponding hysteresis relationships are highly consistent with the theoretical results. The UR-FPB has a large horizontal sliding capacity similar to that of traditional FPBs, while the design of the anti-uplift configuration does not reduce or limit this sliding capacity. Significantly, the study investigated the uplift-restraining behavior of the UR-FPB and its effect on the horizontal responses. The analysis results suggest that the UR-FPB has a good uplift-prevention capacity and this paper recommends that the design value of tensile capacity should not exceed the yield force in tension. Therefore, this novel uplift-restraining friction bearing has an expected effectiveness, which can simultaneously resist vertical tensile loads and function as a horizontal seismic isolator. The proposed hybrid modeling method may provide a useful reference to model the behavior of the UR-FPB in software used for response-history analysis.

Functionally varied negative-stiffness metamaterial core sandwich structures with three-phase bending deformation

Abstract This paper introduces a novel class of negative-stiffness (NS) core sandwich composite structures that exhibit unique mechanical performance, including shape recovery, superelasticity, and energy absorption (EA) in bending and shear mode. The core of these structures consists of a periodic cellular arrangement of double-curved beams that undergo consecutive local snap-buckling transitions between multiple equilibrium states, enabling the structures to change shape reversibly between their initial and deformed configurations. To characterize the force-displacement relationship of the core, a comprehensive analysis was conducted using a combination of 3D printed models and finite-element simulations. The metamaterial core with gradient-thickness negative-stiffness beams were examined under uniform compression, demonstrating that the snap-through behavior of the curved beams was intricately controlled by the beam thickness in each row. The numerical simulations accurately predicted the deformation characteristics of the graded cellular core, supporting the design of a metamaterial core with functionally varied beam thickness for nonuniform transverse loading. This led to spatially controlled NS core material with specific EA of around 50 J kg−1 and an apparent core shear strength of 0.1 MPa, all mainly within the reusable elastic regime. The resulting sandwich structures efficiently mitigated the localized effect from concentrated compressive forces and achieved complete snap-through buckling in all curve beams. Three-point bending response revealed three distinct phases of flexural deformation: the local facial bending phase, the sequential core-snapping superelastic phase, and the global bending phase.

Exploring Porosity’s Role in Stiffening Waste Concrete Conglomerates Synthesized with Microbial Calcite: A Micromechanical Analysis

Abstract Amidst environmental challenges, this study utilizes the innovative method of microbially-induced calcite precipitation (MICP) to explore its application in recycling waste concrete fines (WCF). Specifically, we scrutinize the role of porosity in the mechanical behavior of MICP-cemented WCF conglomerates. Through a series of indentation tests, the study provides force-displacement relationships from which the stiffness of the samples is calculated. The Young’s modulus of the samples is then estimated using Sneddon’s solution, which assumes a conical indenter and homogeneous elastic behavior. Subsequently, the Mori–Tanaka scheme with Eshelby’s solution is employed to predict the Young’s modulus of the samples with different porosity, allowing a comparison with the calculated stiffness. This work contributes to the understanding of the role of porosity in the mechanical behavior of MICP-cemented WCF specimens and offers a pathway for optimizing the production process of such materials. Graphical Abstract