Increase In Contact Force Research Articles

Quantifying Muscle Forces and Joint Loading During Hip Exercises Performed With and Without an Elastic Resistance Band.

An increase in hip joint contact forces (HJCFs) is one of the main contributing mechanical causes of hip joint pathologies, such as hip osteoarthritis, and its progression. The strengthening of the surrounding muscles of the joint is a way to increase joint stability, which results in the reduction of HJCF. Most of the exercise recommendations are based on expert opinions instead of evidence-based facts. This study aimed to quantify muscle forces and joint loading during rehabilitative exercises using an elastic resistance band (ERB). Hip exercise movements of 16 healthy volunteers were recorded using a three-dimensional motion capture system and two force plates. All exercises were performed without and with an ERB and two execution velocities. Hip joint kinematics, kinetics, muscle forces, and HJCF were calculated based on the musculoskeletal simulations in OpenSim. Time-normalized waveforms of the different exercise modalities were compared with each other and with reference values found during walking. The results showed that training with an ERB increases both target muscle forces and HJCF. Furthermore, the ERB reduced the hip joint range of motion during the exercises. The type of ERB used (soft vs. stiff ERB) and the execution velocity of the exercise had a minor impact on the peak muscle forces and HJCF. The velocity of exercise execution, however, had an influence on the total required muscle force. Performing hip exercises without an ERB resulted in similar or lower peak HJCF and lower muscle forces than those found during walking. Adding an ERB during hip exercises increased the peak muscle and HJCF but the values remained below those found during walking. Our workflow and findings can be used in conjunction with future studies to support exercise design.

B-PO03-131 EFFECTS OF CONTACT FORCE ON LESION SIZE DURING PULSED FIELD ABLATION

Effects of contact force (CF) on lesion formation during pulsed field ablation (PFA) have not been validated. To determine the relationship between average CF and lesion size during PFA using a swine beating heart model. A 7F catheter with a 3.5mm saline irrigated (2ml/min) ablation electrode and CF sensor (TactiCath SE, Abbott) was connected to a pulsed electric field (PEF) generator system (CENTAURI, Galaxy Medical). The catheter was positioned in RV and LV under EnSite guidance in 2 closed chest pigs (66kg). During atrial pacing at 90 bpm, biphasic PEF current was delivered between the ablation electrode and a skin patch at 13 separate sites in RV (28Amp, total pulse width of 1.4ms, 4 pulses synchronized with QRS) and 19 separate sites in LV (35Amp, 1.6ms, 7 pulses) at average CF: 1) low (4-12 g, median 8 g); 2) moderate (16-30 g, median 20 g); or 3) high (33-55 g, median 40 g). Ablation was also performed without electrode contact (2 mm away from the endocardium, confirmed by intracardiac echocardiography, n=5). Pigs were sacrificed at 2 hours after ablation and lesion size was measured using triphenyl tetrazolium chloride (TTC) staining. (Fig.) Ablation lesions were clearly identified with TTC staining, showing the dark central zone surrounded by pale boundaries. At constant PEF current and pulse duration, lesion depth increased significantly with increasing contact force. There were no detectable lesions resulting from ablation without electrode contact. At same PEF dose intensity, lesion depth increases significantly with increasing contact force. Electrode-tissue contact is required for effective lesion formation with PEF ablation.

Lateral Extra-articular Tenodesis Alters Lateral Compartment Contact Mechanics under Simulated Pivoting Maneuvers: An In Vitro Study

Background: There is concern that utilization of lateral extra-articular tenodesis (LET) in conjunction with anterior cruciate ligament (ACL) reconstruction (ACLR) may disturb lateral compartment contact mechanics and contribute to joint degeneration. Hypothesis: ACLR augmented with LET will alter lateral compartment contact mechanics in response to simulated pivoting maneuvers. Study Design: Controlled laboratory study. Methods: Loads simulating a pivot shift were applied to 7 cadaveric knees (4 male; mean age, 39 ± 12 years; range, 28-54 years) using a robotic manipulator. Each knee was tested with the ACL intact, sectioned, reconstructed (via patellar tendon autograft), and, finally, after augmenting ACLR with LET (using a modified Lemaire technique) in the presence of a sectioned anterolateral ligament and Kaplan fibers. Lateral compartment contact mechanics were measured using a contact stress transducer. Outcome measures were anteroposterior location of the center of contact stress (CCS), contact force from anterior to posterior, and peak and mean contact stress. Results: On average, augmenting ACLR with LET shifted the lateral compartment CCS anteriorly compared with the intact knee and compared with ACLR in isolation by a maximum of 5.4 ± 2.3 mm (P < .001) and 6.0 ± 2.6 mm (P < .001), respectively. ACLR augmented with LET also increased contact force anteriorly on the lateral tibial plateau compared with the intact knee and compared with isolated ACLR by a maximum of 12 ± 6 N (P = .001) and 17 ± 10 N (P = .002), respectively. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress by 0.7 ± 0.5 MPa (P = .005) and by 0.17 ± 0.12 (P = .006), respectively, at 15° of flexion. Conclusion: Under simulated pivoting loads, adding LET to ACLR anteriorized the CCS on the lateral tibial plateau, thereby increasing contact force anteriorly. Compared with ACLR in isolation, ACLR augmented with LET increased peak and mean lateral compartment contact stress at 15° of flexion. Clinical Relevance: The clinical and biological effect of increased anterior loading of the lateral compartment after LET merits further investigation. The ability of LET to anteriorize contact stress on the lateral compartment may be useful in knees with passive anterior subluxation of the lateral tibia.

Vibration Perception Thresholds of Skin Mechanoreceptors Are Influenced by Different Contact Forces.

Determining vibration perception thresholds (VPT) is a central concern of clinical research and science to assess the somatosensory capacity of humans. The response of different mechanoreceptors to an increasing contact force has rarely been studied. We hypothesize that increasing contact force leads to a decrease in VPTs of fast-adapting mechanoreceptors in the sole of the human foot. VPTs of 10 healthy subjects were measured at 30 Hz and 200 Hz at the heel of the right foot using a vibration exciter. Contact forces were adjusted precisely between 0.3 N–9.6 N through an integrated force sensor. Significant main effects were found for frequency and contact force. Furthermore, there was a significant interaction for frequency and contact force, meaning that the influence of an increasing contact force was more obvious for the 30 Hz condition. We presume that the principles of contrast enhancement and spatial summation are valid in Meissner and Pacinian corpuscles, respectively. In addition to spatial summation, we presume an effect on Pacinian corpuscles due to their presence in the periosteum or interosseous membrane.

Contact analysis of measured surfaces based on modified interacting and coalescing Hertzian asperities (ICHA) model with oblique contact asperities

The contact mechanism for joint surfaces is important for predicting the loading process and dynamic properties of precision machinery products. A multiasperity model considering the lateral interaction and coalescence of contact regions with oblique asperity contact, the interacting and coalescing Hertzian asperities (ICHA) model, is introduced in this work. Contact angle [Formula: see text] and radius of curvature [Formula: see text] are vital parameters that are directly calculated based on grid points measured from the milling and grinding surfaces. Numerical simulations of [Formula: see text] and [Formula: see text] were analysed. The results show that the proposed model is more effective at improving the contact area versus force relationship than various asperity models for low and middle contact forces. [Formula: see text] and [Formula: see text] follow a Gaussian distribution. Because of the existence of coalescence, they decrease with increasing contact force. Furthermore, the [Formula: see text] and [Formula: see text] in the startup phase are crucial data that can be used to judge the effects of oblique asperity contact. They are greatly influenced by fractal dimension [Formula: see text] and fractal roughness G. From the comparisons with the surfaces generated by Weierstrass-Mandelbrot function, it is suggested that to obtain an accurate contact prediction in the loading process, oblique contact is as important as lateral interaction and coalescence.

Force chain characteristics of dense particles sheared between parallel-plate friction system

Using the discrete element method, we investigate the force chain characteristics of dense particles in a parallel-plate particle flow friction system, and considering the influence of pressure load as well as shear velocity. Simulation results show that the shear dilatancy process of this particle friction system can be divided into three typical stages: plastic expansion stage, whole flow stage, and plastic compression stage. The distribution of force chain generally decreases with the increase of dimensionless contact force f. The distribution and bearing rates of force chains depend on the pressure load as well as the shear velocity. The direction of force chain gradually changes closer to the y-axis with the increase of the pressure load, and shifts from y-axis to x-axis with the increase of shear velocity. The magnitude of the total force chain decreases with shear velocity. Moreover, the total force chain fluctuates significantly at lower shear velocity and start-up stage.

Numerical Simulation on the Longitudinal Breach Process of Landslide Dams Using an Improved Coupled DEM-CFD Method

An accurate investigation of the landslide dam breach process is crucial for the understanding the breach mechanism and disaster prediction. However, the numerical research on the landslide dam breach process to date is rarely reported, especially regarding the soil-water flow coupling effect incorporated in the erosion process. This paper presents a numerical investigation on the longitudinal breach process of landslide dams via a coupled discrete element method (DEM) and computational fluid dynamics (CFD) with the volume of fluid (VOF). Moreover, a virtual sphere model is proposed to overcome the computational instability caused by the particle size approaching the mesh size. The accuracy and validity of the improved coupled method are verified using a series of single particle sedimentation cases. By employing this method, the longitudinal breach process of landslide dams featuring different materials and hydrodynamic conditions has been simulated. It is found to satisfactorily reproduce the longitudinal breach process of landslide dams including surface flow erosion, backward erosion, head-cut erosion, and water and sediment rebalance or complete breach. The effects of the inflow discharges and dam materials on the erosion process are systematically resolved. The breach flow can cause the rotation trend of particles and lead to the increase of tangential contact force at the initial stage of the dam breaching. During the breach process, both the strength and density of the force chain continue to attenuate. The results obtained from the improved coupled DEM-CFD simulations can reasonably explain the particle-fluid interaction mechanisms, physical and morphological evolution and breach process at both macroscopic and mesoscopic scales.

A tribo-dynamic model of coupled journal-thrust water-lubricated bearings under propeller disturbance

The main purpose of this study is to develop a tribo-dynamic numerical model for coupled journal-thrust water-lubricated bearings (also referred as coupled bearings) used in rim driven thruster under propeller disturbance, in which the four degree of freedom (4-DOF) dynamic model of the propeller rotor is bridged with the transient mixed friction model of the coupled bearing. A validating experiment for the coupled water-lubricated bearing is performed to support the correctness of the developed tribo-dynamic model. In the model, the disturbing forces and moment caused by the propeller are calculated by the quasi-steady method. Based on the numerical study, the transient coupling effects between the dynamic characteristic of the propeller rotor and the mixed friction of the coupled bearing are revealed. Furthermore, parametric studies are carried out to identify the effects of the structural and working condition parameters on the tribo-dynamic responses of the coupled bearing. Numerical results indicate that disturbing moment leads to the increase in the transient contact force of the coupled bearing, and the coupling hydrodynamic pressure at the common boundary significantly affects the tribo-dynamic behaviors of the coupled bearing. Parametric studies demonstrate that there exists the optimal radial clearance and tilting angle to minimize the transient contact force of the coupled bearing during operation. In addition, numerical studies reveal that the propeller rotor mass is an important parameter affecting the tribo-dynamic responses of the thrust bearing.

Investigation on the impact wear behavior of 2.25Cr–1Mo steel at elevated temperature

The impact wear test of 2.25Cr–1Mo steel against Gr5C12 alloy was performed at a controlled kinetic energy impact wear rig. The effect of temperatures (from 25 °C to 450 °C) on the impact wear damage mechanism was investigated. The contact force, energy absorption, and interface deformation during the impact process were recorded and analyzed in real time. Wear volume, morphology, and elemental distribution of the wear scars were used to characterize wear and tribo-chemistry behavior. Results demonstrate that at varied temperatures, the interface behavior of 2.25Cr–1Mo steel is different. With the rise in temperature, both the contact force, absorption energy, and wear volume first increase and then decrease. The explanation is that higher temperatures can modify the material's surface properties. Delamination, plastic deformation, and oxidative wear are the major mechanisms of impact wear, but the proportions of the three wear mechanisms differ at varied temperature.

Relationship of Catheter Contact Angle and Contact Force with Contact Area on the Surface of Heart Muscle Tissue in Cardiac Catheter Ablation

PurposeThe aims of this study were to develop an experimental procedure for setting the catheter angle with respect to the surface of the heart muscle and the catheter contact force and to investigate the catheter contact area on the heart muscle as a function of catheter contact angle and force.MethodsVisualization tests were performed for 5 contact angles (0°, 30°, 45°, 60°, and 90°) and 8 contact forces (2, 4, 6, 10, 15, 20, 30, and 40 gf). Each experiment was repeated 6 times with 2 different commercially available catheter tips.ResultsThe morphology of the contact area was classified into rectangular, circular, ellipsoidal, and semi-ellipsoidal. The correlation between contact force and contact area was a logarithmic function; increasing contact force was associated with increased contact area. At the same contact force, the correlation between contact angle and contact area was inverse; decreasing contact angle was associated with a corresponding increase in contact area.ConclusionBoth the catheter contact angle and contact force substantially impact the contact area and morphology in catheter ablation procedures.

Effect of Ulnar Head Offset on Distal Radioulnar Joint Stability

A complete ulnar head replacement may be indicated in cases of distal radial ulnar joint (DRUJ) dysfunction to address bony pathology in lieu of using a constrained total DRUJ prosthesis. Complete ulnar head implants are simple, but they may be unstable if soft tissue tension is not adequately restored. We hypothesized that incorporating an increased offset in the complete ulnar head replacement would lead to increased tension on the distal oblique interosseous ligament, increased contact force at the DRUJ, and improved joint stability. Using a specially designed jig, we measured instability by comparing displacement under load (stiffness) of the DRUJ in 10 cadaveric specimens under 4 different conditions: (1) intact, (2) native head after excision of the triangular fibrocartilage complex, (3) replacement of the ulnar head with a standard offset ulnar head, and (4) replacement of the ulnar head with an increased offset ulnar head. No soft tissue repair was done. We measured anteroposterior displacement under load with maximum translation of 10 mm or maximum loads of 50 N. We tested all specimens with the forearm positioned in neutral, supination, and pronation. Excising the triangular fibrocartilage complex decreased the average stiffness of the DRUJ to 46% of the intact state, creating a simulated state of DRUJ instability. Replacing the ulnar head with the standard offset head increased average stiffness to 54% of the intact state. Increasing the ulnar head offset with the simulated total ulnar head replacement increased average stiffness to 77% of the intact state. An increased offset ulnar head replacement improves DRUJ stability compared with a standard anatomic offset ulnar head replacement. Understanding DRUJ morphology and offset is important in the treatment of DRUJ arthritis and instability.

Numerical Investigation of Particle Shape Effect on Sand Shear Strength

The particle shape contributes significantly to sand mechanical properties but is difficult to study in laboratory experiments. In this study, microscopy experiments were used to classify sand particle morphologies as spherical, non-spherical and ball-shaped. Particles with these three morphologies were modeled using the discrete element method to analyze the effect of the particle shape on the shear strength in a direct shear test simulation. The simulation results showed that the non-spherical particles and balls exhibited the highest and lowest peak shear strengths, respectively, under a low vertical stress. The highest and lowest contact force numbers were observed for the non-spherical particles and balls, respectively. The sand particles exhibited a higher resistance to motion with increasing contact force numbers, resulting in a higher shear strength. For particles with low sphericity (S) and roundness (R) values, a high number of contacts and interlocking structures can form, increasing resistance to external forces. As the S decreased, the anisotropy in the contact force increased during the test, and the contact number distribution of the spherical particles tended to remain isotropic during the entire process.

Outcomes of Arthroscopic All-Inside Meniscal Root Repair vs. Observation in Older Patients

Meniscal root tears occur in a bimodal distribution, affecting both young healthy athletes and older patients with early degenerative knees. Root tears lead to de-tensioning of the meniscus and have been associated with increased contact forces and cartilage damage. Management of older patients with root tears is controversial and the efficacy of different treatment options is unclear. The primary aim of this study is to compare the clinical outcomes of patients undergoing an all-inside arthroscopic repair technique versus non-operative management for posterior meniscal root tears. 48 patients diagnosed with a posterior meniscal root tear between 2006 and 2015 were identified and divided into 2 groups: the arthroscopic repair group (AR, 30 knees) and the observation group (O: 18 knees). The AR group underwent a meniscal root repair technique where two all-inside sutures were used to reduce the root back to its remnant (reduction sutures) thereby re-tensioning the meniscus. One mattress suture was then added to strengthen the repair by re-approximating the construct to the posterior capsule. KOOS subscores (Symptoms, Pain, Activities of Daily Living (ADL), Sports and Rec, Quality of Life), Lysholm, Tegner, and VR12 PCS questionnaires were used as the primary outcome measures at a minimum 2 years follow-up. Differences in baseline patient characteristics between the surgical and non-surgical group were examined using Fisher’s exact tests for categorical variables and Mann-Whitney U tests for continuous variables. For changes from baseline to follow up between the surgical and non-surgical group, independent sample t-tests or Mann-Whitney U tests were conducted depending on normality. A Fisher’s exact test was also utilized to analyze the rates of conversation to total knee arthroplasty (TKA) between the surgical and non-surgical group. There were significant changes in all baseline to follow up mean KOOS (all subscores: p < 0.001), Lysholm (p < 0.001), Tegner (p = 0.0002), and VR12 PCS (p < 0.001) scores for the AR group, while the O group had a significant difference in only mean KOOS pain (p = 0.003), KOOS ADL (p = 0.006), and VR12 PCS (p = 0.038) scores from baseline to follow-up. The AR group had a significantly larger increase from baseline to follow up in mean KOOS pain scores (32.0) compared to the O group (15.7) (p = 0.009), KOOS symptom scores (AR: 24.2, O: 9.3, p = 0.029) as well as in Lysholm scores (AR: 27.3 and O: 7.1; p = 0.016). During the follow-up period, 3.3% of patients in the AR group underwent a TKA, which was significantly lower than the 33.3% of patients in the O group (p = 0.008). The hazard of TKA conversion is estimated to be 93.2% lower for patients in the AR group compared to the O group (p = 0.013). Our study found a significant improvement in all clinical outcome scores in the AR group at 2-year follow-up. There was a significantly larger increase in KOOS pain, KOOS symptom, and Lysholm scores in the AR group compared to the O group. The AR group also had a significantly lower conversion to TKA and significantly lower hazard of TKA conversion as compared to the O group. Surgical management showed higher functional outcomes and decreased TKA conversion rates as compared to observation and should be considered as a treatment option for the treatment of meniscal root tears in the older population.

Effect of gradation segregation on low-temperature crack resistance of asphalt pavement using 3D DEM

Gradation segregation can have a great influence on the low-temperature crack resistance of asphalt pavement. In this paper, five kinds of AC-20 asphalt mixtures with different degrees of gradation segregation are designed according to the standards put forward by the American NCHRPRReport-441 project report, and numerical models are developed using the DEM to simulate the splitting test. The effect of gradation segregation is analyzed on the low-temperature crack resistance of asphalt pavement from two aspects of macroscopic (mean splitting strength and horizontal tensile stress) and mesoscopic (contact force, displacement and crack). The results show that in the macro level, the coarse aggregate gradation segregation leads to the decrease of the splitting strength and horizontal tensile stress of the mixture, while the fine aggregate gradation segregation leads to the increase of the splitting strength and horizontal tensile stress of the mixture. Moreover, in the meso-level, the coarse aggregate gradation segregation leads to the decrease of the internal contact force, the displacement and the number of cracks, and the fine aggregate gradation segregation leads to the increase of the internal contact force and quantity of the mixture. Furthermore, the macroscopic response caused by segregation is related to the mesoscopic response and coarse aggregate heavy segregation has the greatest influence on macro and meso mechanical parameters and the low-temperature properties of asphalt mixtures. The research results provide a new idea and way to evaluate the low-temperature crack resistance of asphalt pavement based on the meso-level gradation segregation.

An improved design of a seesaw-type MEMS switch for increased contact force

Microelectromechanical systems (MEMS) switches have a wide range of possible applications due to their promising working characteristics, but commercial success of these devices is limited by low reliability. In contrast with macroscopic electromechanical relays, MEMS switches typically develop a small contact force, which results in unstable and high contact resistance. In this paper we propose the design that ensures several times higher contact force in comparison with previously used structure. Enhancement of the force is achieved without increasing the footprint and operating voltage of the switch. The analytical calculation and finite element simulation of the working characteristics are performed. At the driving voltage of 100 V the modified switch provides the contact force as high as 130 µN, which is an order of magnitude higher than the force developed by the basic device.

On the mechanical behaviour of steel wire mesh subjected to low-velocity impact

Woven wire mesh is a metallic fabric outperforming traditional metal sheets in air circulation, weight saving, impact resistance, etc. In this study, the dynamic mechanical response of steel wire mesh subjected to low-velocity impact loading was investigated using both experimental and numerical methods. An instrumented drop-weight impact facility was used for experimental impact tests, with the effects of clamping wire direction, impact energy, impactor’s mass and size being considered. The extents of damage to the wire mesh specimens under different loading conditions were evaluated after impact tests. Three types of contact force vs. displacement curves corresponding to the plastic deformation, wire breakage, and perforation of wire mesh were identified. Weft wires were found to be stronger and stiffer than warp wires because they could resist higher peak forces and experienced smaller maximum displacements under the same impact energies. The experimental results revealed that the peak contact force increased with impact energy until wire breakage occurred, after which the peak force remained almost unchanged. With the increase of impactor mass, wire mesh specimens experienced severer damage due to the inertia effect and strain rate effect. Impactor size had a significant influence on the dynamic response of wire mesh; a great increase in peak contact force was found when using a larger impactor tip. Moreover, a mesoscale finite element model was developed to analyse the propagation of stress and the evolution of dynamic failure in wire mesh during impact. The simulation results showed that more than 80% of the impactor’s kinetic energy was absorbed through the deformation and failure of wire mesh, while the frictional energy dissipation accounted for about 10% of impact energy.

Dynamic Analysis of Shearer Traction Unit Considering the Longitudinal Swing

Shearer traction failure occurs frequently, which seriously restricts the safe and efficient mining of coal. However, the influence of the shearer’s posture on traction has not been fully considered in the existing research. To improve traction reliability: the dynamic model of the traction unit is established considering longitudinal swing; the walking characteristics of the shearer and the dynamics of the traction unit are analyzed; and the influences of traction velocity, drum load cutting arm angle, and depression angle are discussed. The results show that the longitudinal swing is reciprocating and the positive swing is more serious. With the increase of the traction velocity, the walking stability of the shearer decreases while the contact force increases, especially the support slipper. The longitudinal swing increases with the increase of lateral load, but the supporting force of the support slipper decreases with the increase of cutting load. The forces of the walking wheel and the support slipper show an increasing trend with the increase of cutting arm angle. When the depression angle is 5–10°, the load distribution of the contact components of the traction unit is more balanced. The results provide a reference for the structure optimization of the shearer and the layout of coalface.

Investigating the Combined Effects of Inherent and Stress-Induced Anisotropy on the Mechanical Behavior of Granular Materials Using Three-Dimensional Discrete Element Method

The three-dimensional discrete element method (DEM) was employed to investigate the combined effects of inherent and stress-induced anisotropy of granular materials. The particles were modeled following real particle shapes. Both isotropic and inherently anisotropic specimens were prepared, and then true triaxial numerical tests were conducted using different intermediate principle stress ratios (b). The results indicate that the oriented particles in the anisotropic specimens form strong contacts in their long axis direction in the early stages of shearing, which restrains the contraction of the specimens. As the strain increases, the oriented particles start to rotate and slide, which results in shorter contraction stages and fewer number of interparticle contacts with peak values compared to the isotropic specimens. In addition, the increase inbvalues aggravates the rotating and sliding of particles in the inherently anisotropic specimens and restrains the contraction of the granular and the increase of contact forces. As a result, the inherent anisotropy reduces the effects of stress-induced anisotropy on the mechanical behavior of granular materials.

Time dependent response of impact induced functionally graded conical shell considering porosity

Time dependent low-velocity single and multiple impact response of functionally graded (FG) untwisted and pretwisted conical shells are analysed considering porosity factor. A modified Hertzian contact law which accounts for permanent indentation is considered for the low velocity impact problem. An eight-noded isoparametric shell element is used for the finite element formulation while Newmark’s time integration algorithm is used to solve the time dependent equations. The effects of porosity considering even and uneven porosity factor, initial velocity of impactor (VOI), mass of the impactor and twist angle of FG conical shell on the transient impact response of the conical shell are examined and analyzed. The contact force and indentation increase with increase of VOI and mass of the impactor while the contact duration decreases for both the occasions. Twist angle has a significant effect on contact force but has marginal effect on contact duration. Contact force for perfect (porosity free) FG conical shells is higher than that of porous FG conical shells. Lower contact force is observed for higher porosity factor. Even porous FG conical shell predicts lower contact force and higher shell displacement than that of an uneven porous FG conical for a given porosity factor.

Framework of wind-traffic-bridge coupled analysis considering realistic traffic behavior and vehicle inertia force

The performance of a long-span bridge under strong wind and traffic loads is of great importance to ensure the functionality and the serviceability of the bridge as well as the safety of running vehicles. In this paper, an innovative wind-traffic-bridge (WTB) interaction model for predicting the dynamic performance of the long-span bridge and running vehicles under the crosswind is proposed, considering realistic traffic behavior and vehicle inertia force. In this regard, the LAI-E traffic simulation model aiming to faithfully reproduce realistic traffic flow is developed by integrating the kinetics theory, vehicle capabilities, and driver reactions. The results indicate that using the traditional NaSch traffic model results in a significant overestimation of the vehicle lateral response under a windy environment, whereas the LAI-E traffic model can overcome this issue by ensuring a smooth speed transition during the vehicular acceleration/deceleration process. Additionally, when the vehicle accelerates or decelerates at the emergency capability, the additional pitching moment caused by the vehicle inertia force can result in remarkable increase of vertical wheel contact forces. The present study suggests the necessity of considering both realistic traffic behavior and vehicle inertia force during the WTB analysis.