Search Results (98)

The oscillatory properties of pendular motion, along with the associated energetic conditions, are used to induce analytical functions capable of simultaneously describing the angular position and velocity. To describe the angular position of a generic pendulum, for very large amplitudes of oscillation, we used the numerical solutions obtained from the numerical resolution of the differential equation of motion. The solver software needed was built using the LabView 2019 platform, but any other ODE solver containing peak and valley detectors can be used. The fitting software and plots were performed with the ORIGIN 7.0 program, but also other equivalent programs can be used. For a non-damped pendulum, an analytical model is proposed, built from simple trigonometric functions, but containing the important physical information of the dependence between the period and amplitude of oscillation. The application of the proposed model, using the numerical solutions of the non-approximated differential equation of motion, shows very good agreement, less than 0.01%, for large amplitudes, up to 3π/4. Full article

Asphalt pavements are widely used in airports due to their excellent skid resistance, vibration damping, and ease of construction. However, traditional fog seal materials often suffer from insufficient adhesion between fine sand and the emulsified asphalt binder, resulting in limited durability of the maintenance effect. This study aims to optimize the design of traditional fog seal materials and systematically evaluate their surface and durability performance. Firstly, a composite modified emulsified asphalt was prepared as the sand suspension slurry for the sand-containing fog seal. Through the dry wheel abrasion test, the optimal fine aggregates content was determined for four different spraying amounts (0.8, 0.9, 1.0, and 1.1 kg/m²). When the proportion of fine aggregates increases, the spraying amount needs to be increased accordingly to ensure the wrapping effect. Subsequently, pavement performance evaluation was conducted based on several indicators, including surface curing time, British Pendulum Number (BPN) friction coefficient, permeability coefficient, and mass loss rate. The results showed that the designed sand-containing fog seal significantly reduced surface curing time and exhibited superior skid resistance and permeability property compared to styrene-butadiene rubber (SBR)-modified emulsified asphalt. After freeze–thaw cycles, the maximum decrease in friction coefficient was 10.2%, and the mass loss rate after abrasion was approximately 67%, which were lower than those of SBR-modified emulsified asphalt (22.2% and 81%, respectively). Finally, considering the comprehensive performance comparison and evaluation, the optimal mix proportion was determined as 1.0 kg/m² spraying amount with 30% fine aggregates content. The findings of this study provide practical support for improving the durability and service life of airport asphalt pavements. Full article

This study investigates the evolution laws and prediction models of anti-skid and wear-resistant performance for asphalt pavements during the operation period. Using a combination of indoor accelerated wear tests and field detection, mixed specimens are prepared with SBS modified asphalt, limestone, and basalt aggregates. Through accelerated wear tests of different durations, the structural depth and friction coefficient are measured. Combined with the field data from the G56 K2319 section of the Hangrui Expressway, the decay laws of anti-skid performance are analyzed, and prediction models are established. The results show that the anti-skid performance of basalt mixtures is superior to that of limestone. The deepened structure technology significantly enhances the performance of basalt but has a negative impact on the pendulum value of limestone. The influence degrees of wear duration, aggregate type, and deepened structure state on structural depth and pendulum value vary. The initial structural depth of basalt mixtures (0.85 mm) is 11.8% higher than that of limestone (0.76 mm). The longitudinal pendulum value of basalt (44) is 10% higher than that of limestone (40), while the transverse pendulum value of limestone (50) is 4.2% higher than that of basalt (48). After 21 h of wear, the structural depth of basalt (0.68 mm) is 4.6% higher than that of limestone (0.65 mm), with a decay rate 23.6% lower. The pendulum value of basalt remains above 50, while limestone’s longitudinal pendulum value drops to 36 (10% lower than its initial value), even below the unmodified state. The influence order for structural depth is deepened structure state > wear duration > aggregate type, and for lateral pendulum value, it is wear duration > deepened structure state > aggregate type. There is a significant linear relationship between structural depth/pendulum value and wear duration, and the prediction models are reliable. The indoor accelerated wear of 44.5 h is equivalent to the field operation wear of 3 years. The research findings provide a theoretical basis for the evaluation of anti-skid performance, maintenance decision-making, and material optimization of asphalt pavements. Full article

The torsional, lateral, and axial vibrations that occur during drilling operations have negative effects on the drilling equipment. These negative effects can cause huge economic impacts, as the failure of drilling tools results in wasted materials, non-productive time, and substantial expenses for equipment repairs. Many researchers have tried to reduce these vibrations and have tested several models in their studies. In most of these models, the drill string used in oil wells behaves like a rotating torsion pendulum (mass spring), represented by different discs. The top drive (with the rotary table) and the BHA (with the drill pipes) have been considered together as a linear spring with constant torsional stiffness and torsional damping coefficients. In this article, three models with different degrees of freedom are considered, with the aim of analyzing the effect of variations in the stiffness and damping coefficients on the severity of torsional vibrations. A comparative study has been conducted between the three models for dynamic responses to parametric variation effects. To ensure the relevance of the considered models, the field data of torsional vibrations while drilling were used to support the modeling assumption and the designed simulation scenarios. The main novelty of this work is its rigorous comparative analysis of how the stiffness and damping coefficients influence the severity of torsional vibrations based on field measurements, which has a direct application in operational energy efficiency and equipment reliability. The results demonstrated that the variation of the damping coefficient does not significantly affect the severity of the torsional vibrations. However, it is highly recommended to consider all existing frictions in the tool string to obtain a reliable torsional vibration model that can reproduce the physical phenomenon of stick–slip. Furthermore, this study contributes to the improvement of operational energy efficiency and equipment reliability in fossil energy extraction processes. Full article

Pavement surface texture significantly affects its skid resistance. To characterize pavement surface texture and analyze its correlation with skid resistance, this paper proposes a novel three-dimensional (3D) texture evaluation index: mean texture surface area density (MTSAD). First, field tests were conducted on Chengdu Greenway pavement using a portable laser scanner to collect high-precision texture data, while a pendulum friction tester was employed to measure the British Pendulum Number (BPN). Subsequently, digital image processing technology was employed for the 3D reconstruction of pavement texture. Leveraging the high-resolution data characteristics and incorporating the concept of infinite subdivision, an innovative method for calculating the pavement texture surface area was developed, ultimately yielding the MTSAD. Finally, polynomial regression analysis was performed to examine the correlation between MTSAD and BPN, revealing a coefficient of determination (R²) of 0.8302. The results demonstrate a close relationship between MTSAD and pavement friction, while proving that texture indices that are easy to promote can be obtained through high-precision 3D point cloud images, and validating the potential of non-contact texture measurement as a viable alternative to conventional contact-based friction testing methods. Full article

This research article tackles the control problem of an inverted pendulum, also known as the Furuta pendulum, mounted on a velocity-controlled robot manipulator in two configurations: the rotary pendulum and the translational pendulum. Differently from most of the existing control architectures where the motor actuating the pendulum motion is torque-controlled, the proposed control architecture exploits the inner velocity loop usually available on industrial robots, thus easing the implementation of an inverted pendulum. Another aspect investigated in this paper and mostly overlooked in the literature is the digital implementation of the control and, specifically, the latency introduced by the digital controller. The proposed control solution explicitly models such effects in the control design phase, improving the closed-loop performance. The additional novelty introduced by this paper is the friction compensation that is essential in the swing-up phase of the inverted pendulum, whereas classical control strategies for the nonlinear swing-up usually neglect this effect, and their solutions lead to control failures in practical systems. This paper presents detailed modeling and experimental identification phases followed by the control design of both the nonlinear swing-up algorithm and the linear stabilization controller, both experimentally validated on a Meca500 robotic arm controlled via an EtherCAT communication protocol by a mini PC featuring a Xenomai real-time operating system. The overall system showcases the potential of high-performance digital control systems in industrial robotic applications. Full article

In this paper, we construct the conformable actuated pendulum model in the conformable Lagrangian formalism. We solve the equations of motion in the absence of force and in the case of a specific force resulting from torques, which generalizes a well known mechanical model. Our study shows that the conformable model captures essential information about the physical system encoded in the parameters which depend on the conformability factor $\alpha$. This dependence can describe internal variations such as viscous friction, transmission, or environmental effects. We solve the equations of motion analytically for $\alpha =1/2$ and using Frobenius’ method for $\alpha \ne 1/2$. Full article

To investigate the influence of pavement texture on tire hydroplaning, this study utilized laser scanning to capture the surface characteristics of three asphalt mixtures—AC-13, SMA-13, and OGFC-13—across fifteen rutting plate specimens. Three-dimensional (3D) pavement models were reconstructed to incorporate realistic texture data. Finite element simulations, employing fluid-structure interaction and explicit dynamics in Abaqus, were conducted to model tire-water-pavement interactions. The results indicate that the anti-skid performance ranks as OGFC > SMA > AC. However, despite OGFC and SMA exhibiting comparable anti-skid metrics (e.g., pendulum friction value and mean texture depth), OGFC’s superior texture uniformity results in significantly better hydroplaning resistance. Additionally, tire tread depth critically influences hydroplaning speed. A novel Anti-Slip Comprehensive Texture Index (ACTI) was proposed to evaluate pavement texture uniformity, providing a more comprehensive assessment of anti-skid performance. These findings underscore the importance of texture uniformity in enhancing pavement safety under wet conditions. Full article

The study of vibration isolation devices has become an emerging area of research in view of the extensive damage to buildings caused by earthquakes. The ability to effectively isolate seismic vibrations and maintain the stability of a building is thus addressed in this paper, which evaluates the effect of horizontal ground excitation on the response of a structure isolated by a coupled isolation system consisting of a non-linear damper (QZS) and a friction pendulum system (FPS). A single-degree-of-freedom system was used to model structures whose bases are subjected to seismic excitation in order to assess the effectiveness of the QZS–FPS coupling in reducing the structural response. The results obtained revealed significant improvements in structural performance when the QZS–FPS system uses a damper of optimum stiffness. A 30% reduction in displacement was recorded compared with QZS alone for two signals, one harmonic and the other stochastic. The response of the QZS–FPS system with soft stiffness to a harmonic pulse reveals amplitudes reaching around eight times those of the pulse at low frequencies and approaching zero at high frequencies. In comparison, the rigid QZS–FPS coupling has amplitudes 0.9 and 3.5 times higher than those of the harmonic signal. Thus, the resonance amplitudes observed for the QZS–FPS system are lower than those reported in other studies. This analysis highlights the performance differences between the two types of stiffness in the face of harmonic pulses, underlining the importance of the choice of stiffness in vibration management applications. The stochastic results show that on both hard and soft soils, the new QZS–FPS system causes structures to vibrate horizontally with maximum amplitudes of the order of 0.003 m and 0.007 m respectively. So, QZS–FPS coupling can be more effective than all other isolators for horizontal ground excitation. In addition, the study demonstrated that the QZS–FPS combination can offer better control of building vibration in terms of horizontal displacements. Full article

High Friction Surface Treatments (HFSTs) are frequently used to increase skid resistance and reduce collisions, particularly in crash-prone zones, including horizontal curves and intersections. Epoxy-based binders traditionally have been the sole option for HFSTs, but their drawbacks, such as high costs and compatibility challenges, have led to the search for substitute binders, including asphalt-based options. This study investigates the comparative performance of highly modified asphalt-based binders, including polymer-modified, mastic, and highly modified emulsions, in HFST applications using two aggregate types, Calcined Bauxite (CB) and Rhyolite with different gradations, with an emphasis on their frictional properties, durability, and resistance to polishing. Laboratory evaluations, including the Pendulum Tester (BPT), Dynamic Friction Testing Equipment (DFT), Surface Texture Measurement Apparatus (CTM), and Binder Bond Strength Test (BBS), were carried out to examine the Coefficient of Friction (COF), Mean Profile Depth (MPD), and aggregate bonding and retention. In terms of durability and friction, this study indicated that highly modified asphalt-based binders performed better than PG binders and conventional emulsions. The highest BPT values, both prior to and following polishing, were consistently observed for CB, with the emulsion containing the highest reactive polymer modifier showing the smallest decrease in BPT value (12.86% for CB and 10.34% for Rhyolite). Epoxy showed a greater COF retention over lengthy polishing cycles; however, highly polymer-modified (PM) binders like PG82-22 (PM) performed better than Epoxy under specific conditions. The macrotexture analysis revealed that Epoxy-based samples retained surface texture for further polishing cycles, while Mastic2 and PG82-22 (PM) also showed strong MPD retention. These findings highlight the importance of optimizing aggregate–binder combinations to ensure durable and effective HFST applications. Full article

This study presents a comprehensive comparative analysis of a hospital located in Costa Rica, examining the performance of sliding pendulum isolators under different international seismic design standards. The standards considered in this research include the U.S. code ASCE/SEI 7-22 and various European standards, namely EN 15129, EN 1337, and EN 1998-1. The case study employs the Equivalent Linear Analysis method, as prescribed by Eurocode 8, alongside the Equivalent Lateral Force procedure from ASCE/SEI 7-22. The seismic action is defined using the acceleration response spectrum from the Costa Rican Seismic Code (CSCR-10, 2010). However, certain limitations must be acknowledged when applying the equivalent linear analysis approach. One key restriction is that the isolation system must be modeled with equivalent viscoelastic behavior, which is feasible for sliding pendulum isolators. Despite being a simplified method, this approach proves valuable in the initial selection and optimization of an isolation system, particularly for practitioners. It is recommended that this method be applied as a preliminary step before performing more advanced nonlinear analyses. After determining the optimized parameters for the friction pendulum system, the detailed design of the isolators will be conducted following the provisions of the selected international standards. This process includes verifying compliance with key performance requirements such as self-recentering capability, type testing procedures, deformation verification, and partial load verification on the concrete pedestal, where the isolators are assumed to be installed. These requirements ensure that the isolation system meets the necessary structural performance criteria, providing reliable seismic protection while adhering to international engineering best practices. Full article

In developing countries with high seismic activity, a need exists to construct resilient infrastructure and reduce the housing deficit. Industrialized timber construction and the implementation of seismic isolation interfaces may represent a good alternative to respond to these demands. This paper studies the feasibility of constructing cross-laminated timber (CLT) buildings equipped with frictional pendulum bearings in Chile or similar highly seismic regions. The first part of this study shows a first-order approach for modeling the highly nonlinear behavior of CLT walls using a Smooth Hysteretic Model (SHM). An equivalent model of a base-isolated building was developed using the SHM as well as a physical model of the Friction Pendulum System in order to assess the seismic performance of CLT buildings with frictional isolators. The second part of this research presents and discusses the results of a broad parametric analysis concerning the seismic performance of base-isolated CLT buildings. The seismic assessment was carried out by deriving fragility curves and including the uncertainty linked to the seismic input and the friction coefficient of the isolation system. Constructing lateral resistant systems based on CLT walls presents a feasible alternative for buildings in high seismic hazard areas. Excellent seismic performance is achieved if the superstructure’s is designed with a reduction factor of 1, or if the superstructure’s fundamental period ranges from 0.6 to 0.9 s and is designed with a reduction factor of 2 and ductility capacity of 6 or more. An excellent seismic performance can be obtained for larger reduction factor values if the superstructure has middle to high maximum ductility capacity. Full article

To address the issue of air pollution caused by automobile exhaust in China, a titanium dioxide/graphite carbon nitride (TiO₂/g-C₃N₄) composite photocatalyst capable of degrading automobile exhaust was prepared in this study. It was used as an additive to modify styrene–-butadiene latex (SBR) emulsified asphalt. The basic properties of modified emulsified asphalt before and after aging were analyzed, and the dosage range of TiO₂/g-C₃N₄ (TCN) was determined. The environmentally friendly micro-surfacing of degradable automobile exhaust was prepared. Based on 1 h and 6 d wet wheel wear test, rutting deformation test, surface structure depth test, and pendulum friction coefficient test, the road performance of TCN environmentally friendly micro-surfacing mixture with different contents was analyzed and evaluated, and the effect of environmentally friendly degradation of automobile exhaust was studied by a self-made degradation device. The results show that when the mass ratio of TiO₂ and melamine was 1:4, the TCN composite photocatalyst had strong photocatalytic activity. The crystal structure of TiO₂ and g-C₃N₄ was not damaged during the synthesis process. The g-C₃N₄ inhibited the agglomeration of TiO₂. The introduction of N-Ti bond changed the electronic structure of TiO₂, narrowed the band gap and broadened the visible light response range. When the TCN content was in the range of 1~7%, the softening point of SBR- modified emulsified asphalt increased with the increase in TCN content, the penetration decreased, the ductility decreased gradually, and the storage stability increased gradually. The penetration ratio and ductility ratio of the composite-modified emulsified asphalt after aging increased with the increase in TCN content, and the increment of the softening point decreased. This shows that the TCN content is beneficial to the high-temperature performance and anti-aging performance of SBR-modified emulsified asphalt, and has an adverse effect on low temperature performance and storage stability. The addition of TCN can improve the wear resistance and rutting resistance of the micro-surfacing mixture, and has no effect on the water damage resistance and skid resistance. The environment-friendly micro-surfacing asphalt mixture had a significant degradation effect on NO, CO, and HC. With the increase in TCN content, the degradation efficiency of the three gases was on the rise. When the content was 5%, the degradation rates of NO, CO, and HC were 37.16%, 25.72%, and 20.44%, respectively, which are 2.34 times, 2.47, times and 2.30 times that of the 1% content, and the degradation effect was significantly improved. Full article

Asphalt pavement skid resistance, governed by surface texture, is critical for traffic safety. Most research has focused on full-depth textural characteristics, often overlooking the depth of tire–pavement contact under real traffic conditions. This study introduces the concept of the Effective Depth of Skid Resistance (EDSR) to describe the effective depth of tire–asphalt contact, improving skid resistance assessment accuracy. Using blue linear laser scanning, surface textures of three common asphalt pavements with wearing courses—AC-13, AC-16, and SMA-13—were analyzed, and friction coefficients were measured using a British pendulum. After pre-processing three-dimensional texture data, fractal dimensions at various depths were calculated using the box-counting method and correlated with the friction coefficients. Previous studies show an insignificant correlation between full-depth asphalt pavement textures and skid resistance. However, this study found a significant positive correlation between skid resistance and pavement textures at specific depths or the EDSR. A depth with a correlation exceeding 0.9 was defined as the EDSR. Linear formulas were established for each pavement type within these EDSR ranges. A theoretical model was developed for predicting skid resistance, showing an over 80% accuracy against real-world data, indicating its potential for improving road surface performance detection. Full article

Friction pendulum bearings are widely used seismic isolation devices for bridges, with their behavior governed by friction during excitation. Sliding velocity and contact pressure are among the factors that substantially affect the friction coefficient. Common friction models include the Coulomb model, which assumes constant friction and neglects both sliding velocity and contact pressure, and the velocity-dependent model, which ignores contact pressure. This study investigates the impact of neglecting contact pressure on bridge response by additionally employing a velocity-pressure-dependent friction model and comparing the effects of these three models on the bridge response. Five 3-span box-girder RC bridges were modeled in OpenSees (v3.5.0) using Coulomb, velocity-dependent, and velocity-pressure-dependent friction models. Deck height variations were introduced to account for axial load changes on bearings. Nonlinear time history analyses were performed to evaluate seismic responses. The study also explored the effects of substructure-to-superstructure mass ratio and variations in the experimentally obtained rate parameter of velocity-dependent and velocity-pressure-dependent models. Results indicate that the velocity-pressure-dependent model provides more consistent predictions, while the rate parameter has negligible effects. The velocity-pressure-dependent model increases isolator displacement by nearly 2.5 times compared to the Coulomb and velocity-dependent models. Differences in responses are influenced more by the mass ratio than by the deck aspect ratio. Full article