Vertical Load Research Articles

Performance of RC frames strengthening by external post-tensioning tendons under vertical and lateral loads

In this study, the structural performance of reinforced concrete frames strengthened with external post-tension tendons was investigated. An experimental study was performed to investigate the failure modes and generate the data required to validate the numerical model. The experimental study includes a reinforced concrete (RC) frame control specimen without strengthening and three strengthened specimens under vertical loads. The specimens were strengthened using external post-tensioning with three different tendon layouts, including a straight tendon in the beam-positive moment zone, straight tendons in the beam-positive and column-negative moment zones, and U-shape tendons along the frame beam. The numerical model was built for the four specimens, validated using the experimental results, and used to analyze the lateral load performance. Results showed that the most effective strengthening technique for the vertical load was the beam U-shape tendons, and for the lateral load, it was the beam and column strengthening. It can be concluded from this case study that strengthening frames with external post-tensioning techniques can enhance the first crack load, yielding load, and ultimate load by 80–100 %, 180–250 %, and 35–70 %, respectively.

Biomechanics of Bruxism Potentially Determine the Sites of Severe TMJ Osteoarthritis

The objective of this study was to assess the osteoarthritis (OA) disease severity in 47 temporomandibular joints (TMJs) using a validated scale for gross signs of OA while noting the specific sites for profound disease on the donor condyle and fossa. A disease severity score of Grade 0–4, representing absent to severe disease, was awarded to each specimen’s condyle and fossa by two blinded investigators who have demonstrated interrater reliability. The mandibular fossa was more pathological compared to the mandibular condyle (* p = 0.001). When the deepest focal lesions were qualitatively assessed, it was demonstrated that the mandibular fossa was more severely degenerated than the articular eminence in 58% of donors. In this subpopulation, 74% of the severe mandibular fossa pathology was seen on the deep articular surface. When the articular eminence was the most severely degenerated region of the fossa, it was equivalently likely to see severe focal lesions on the lateral eminence (35%) or equally distributed across the entire eminence (35%). The greatest disease severity was discovered in sites of overloading, which may be associated with paranormal mandibular movements and potentially bruxism. Patients with bruxism produce significant translational movements (grinding) in the upper joint compartment and heavy vertical loading (clenching). Theoretically, this amplifies pressure and inflammation on the lateral articular surfaces and in the deep fossa.

Assessment of different materials used for fabrication of fixed free fixed dental prostheses: finite element analysis

BackgroundThis research assessed three materials to be used in the fabrication of fixed free fixed dental prosthesis using finite element analysis. Total deformation, Von Mises stress maximum amounts and sites on both the bone, and the fixed dental prosthesis body were compared.Methods3D finite element model was made for the tested fixed dental prosthesis and a contact scanner was used. A fixed free dental prosthesis was made restoring the maxillary first premolar, where second premolar with first molar were the supporting abutments that were scanned. Porcelain fused to metal, CEREC Tessera (Dentsply Sirona) and Poly-Ether-Ketone-Ketone were assessed as fixed free dental prosthesis materials. Cement thickness was adjusted to 40 microns. 100 N vertical load was applied to the central fossa of the pontic in the model.ResultsThe deformations in this study were within the acceptable range except with the PEKK fixed free prosthesis. Tessera showed better results than the porcelain fused to metal as the more elastic modulus allows for absorption of energy from loading.ConclusionsPurely used PEKK is not recommended for fixed free dental prosthesis. Low stiffness fixed dental prosthesis material helps in transferring low amount of load to the underneath tissues.

Numerical Study of the Ultimate Bearing Capacity of Two Adjacent Rough Strip Footings on Granular Soil: Effects of Rotational and Horizontal Constraints of Footings

In this paper, the numerical study of the ultimate bearing capacity (UBC) of two closely spaced strip footings on granular soil is investigated using the finite element method (FEM) and upper bound limit analysis (UBLA). Although the UBC of two adjacent footings has previously been studied in other experimental and numerical research, in all the previously reported studies, the footings were not allowed to rotate and move horizontally freely. Due to the deformation of the soil medium, two closely spaced footings are subjected to horizontal movements and tilting, even under central vertical loads. When the two adjacent footings are not permitted to rotate and move in the horizontal directions, the unwanted bending moment and horizontal force act on the footings. Indeed, the UBC of two closely spaced rough footings is evaluated under incorrect constraints in earlier research. In the present research, the UBC of two adjacent rough footings is evaluated with and without these incorrect constraints. The key finding of this study is that constraining the horizontal and rotational movement of the foundation artificially increases the UBC, which does not reflect field conditions. When foundations are permitted to rotate and move horizontally, there is no increase in UBC; however, there is an increased risk of differential settlement and structural instability.

Influence of Tire-Enveloping Model Complexity on High-Frequency Simulations

ABSTRACT Race tires are subject to high speeds and high vertical loads during cornering. They are also subject to extreme stress when they are driven over high-frequency and low-amplitude curbs, often leading to tire failures. Research and development by D. C. Davis and P. W. A. Zegelaar has shown that when the tire moves over high-frequency, low-amplitude, and short-wavelength obstacles, it exhibits obstacle-enveloping properties. Tire response over such obstacles includes vertical force variation, longitudinal force variation, and rotational speed variation. Additionally, such road inputs excite tire belt dynamics that include high-frequency modes. Therefore, a single-contact-point model is no longer sufficient to predict tire response over such obstacles. To better capture the tire obstacle-enveloping behavior, advanced contact patch models such as the tandem-cam model by P. W. A. Zegelaar, the radial–interradial spring model by J. M. Badalmenti and G. R. Davis Jr., and the flexible ring model by S. Gong have been developed. To capture high-frequency tire belt dynamics, the rigid-ring model has been developed by P. W. A. Zegelaar. Previous work combines the rigid-ring model with the tandem-cam model to capture obstacle-enveloping behavior and tire belt dynamics up to 60–100 Hz. This paper presents a comparative study of different tire–road contact models to simulate high-frequency curbs typically found at racetracks. The curb profile of the Singes corner at the Paul Ricard racetrack is chosen for simulations as it is known to be extremely demanding on the tires, often causing failures. An advanced four-wheel model is used to simulate a race car at high speeds. Metrics to quantify the tire response over these high-frequency curbs are created and an investigation is conducted to quantify the influence of tire model complexity on the metrics.

Multi-Story Volumetric Blocks Buildings with Lower Frame Floors

This article presents the results of experimental studies of the stress–strain state of volumetric blocks based on the underlying frame structures. The aim of the research is to evaluate the stress–strain state and the nature of damage development as a result of an increase in the load up to a critical level. Based on the analysis of the nature of the damage, recommendations have been developed to strengthen the destruction zone. Data were collected on the redistribution of stresses and deformations, the formation of cracks and joint openings, the magnitude of horizontal displacements, and the failure mode of volumetric blocks and floor frames. Five full-scale volumetric blocks were tested under the loading of hydraulic jacks, differing in concrete type, reinforcement, presence of doors, and dimensions of the stylobate beams. When the volumetric modules were supported by a frame floor the results revealed that the maximum destructive load of 10,462 kN was observed in the first specimen; the horizontal displacements of the walls decreased by 13–18 mm, and there was a decrease in the crack opening width to 0.5 mm. The cracks decreased the strength of the walls, leading to a redistribution of the compressive stresses and their increase in the support zone. The most significant compressive strains in concrete in the corner parts of longitudinal walls were in the range of (600–620) × 10−6, and in the middle part of the walls, 370 × 10−6 were observed. Furthermore, the largest cracks caused significant horizontal displacements (deplanation) of the walls, which decreased the stiffness of the conjunction of longitudinal walls with the floor slab and created an additional eccentricity of the vertical force. Based on the findings, the correlation between the measured parameters of each specimen at all stages of vertical load increase is demonstrated and illustrated in graphs of the measured parameters. The importance of quantity compliance with the initial rigid connection between the longitudinal wall and ceiling plate has been estimated.

Experimental and theoretical studies on deformation characteristics of Geosynthetic-Reinforced Soil (GRS) abutments induced by vertical loads

This study conducted five centrifuge model tests to investigate the deformation characteristics of the Geosynthetics Reinforced Soil (GRS) abutments under vertical loads, considering the setback distance ab and beam seat width B as two major influencing factors. Test results show that a linear correlation existed between the maximum lateral facing displacements DL and the maximum settlements at the top of the GRS abutments Dv. The ab and the B had different effects on the deformation characteristics of the GRS abutments as well as the relationship between the DL and the Dv. The total volumetric strains of the GRS abutments were smaller than 0.3% for all the cases investigated in this study, indicating that it was reasonable to use the assumption of zero-volume change for the deformation calculation of the GRS abutments. This study proposed an improved semi-empirical method to describe the relationship between the DL and the Dv. Centrifuge test results and data collected from the literature were used to validate the improved method. It was concluded that the improved method had the advantage of considering the effects of the ab and the B separately and therefore significantly improved the prediction accuracy of the deformations of the GRS abutments.

Bearing Capacity Equations for Intact Argillaceous and Arenaceous Rocks in Malaysia Derived from P-Wave Velocity

This paper presents the derivation of the bearing capacity equation of shallow foundations using P-wave velocity based on the seismic refraction method on argillaceous rocks (shale) and arenaceous rocks (sandstone). Various theories of bearing capacity equations were developed over the years for the calculation of bearing capacity under vertical central loading. But, the most widely used on rock is the Mohr-Coulomb failure criterion given by Meyerhof (1963). Based on this theoretical development, the empirical equation of ultimate bearing capacity was obtained. The detailed derivation of these parameters is comprised of the results from Uniaxial Compressive Strength (UCS) and P-wave velocity values. The proposed empirical equation of bearing capacity derived from P-wave velocity herewith can be used as an alternative method in designing shallow foundations. There is a good agreement on the bearing capacity determination from P-wave velocities.

Comparison of Biomechanical Behaviors of Different Designs and Configurations of Titanium and Zirconium Dental Implants With Finite Elements Analysis in Anterior Maxilla.

Finite element analysis assists in the understanding of the biomechanical behavior of implants with different designs and material characteristics. Through this analysis, this study aimed to compare the biomechanical behaviors of different designs and configurations of titanium (tapered or cylindric) and zirconia dental implants in the edentulous anterior maxilla. Three-dimensional models of the edentulous maxilla, dental implants, and prosthetic structures were modeled, and different loading conditions were applied to simulate realistic conditions. A total of 6 different models were evaluated: the model (M1) in which tapered implants were located bilaterally in the central canine, the model (M2) in which tapered implants were located bilaterally in the lateral canine, the model (M3) in which cylindric implants were located bilaterally in the central canine, the model (M4) in which cylindric implants were located bilaterally in the lateral canine, the model (M5) in which zirconia implants were located bilaterally in the central canine, and the model (M6) in which zirconia implants were located bilaterally in the lateral canine. Maximum tensile and compressive stress values were recorded at M4 under vertical loading and at M6 under oblique loading, whereas minimum stress values were recorded at M1 under all loading conditions. Maximum von Mises stress values under vertical and oblique loading conditions were observed at M3 and M4, while the minimum stress was observed at M1 and M2. In conclusion, zirconia implants may present a biomechanically convenient and esthetic alternative treatment option in edentulous anterior maxilla rehabilitation compared with tapered and cylindric implants.

Study on physiological injuries of occupants under vertical impact loads

Under vertical impact loads, such as explosions, serious compressive deformation occurs in the pelvic bones and lumbar vertebrae of the human body leading to injuries or fatalities for occupants. This study focuses on the occupant-seat model in military vehicles, establishes a biomechanical model of the human spine, and establishes the relationship between vertical impact loads and human injuries. Subsequently, a C-shaped energy-absorbing cushioning structure is designed for application at the bottom support of the seat. Using a peak value of 50 g explosion-simulated triangular wave loading, the study compares the attenuation effects of different structural characteristics of cushioning energy-absorbing structures on impact loads. The results indicate that a 50 g peak vertical impact load can cause significant human injuries. The designed energy-absorbing cushioning structure can greatly reduce human response, but both excessively soft and rigid energy-absorbing cushioning structures fail to achieve effective impact attenuation.

Tire dynamics simulation based on MATLAB/Simulink

Abstract This paper explores different tire models to address the challenge of simulating tire dynamic characteristics. The Magic Formula is utilized to establish the dynamic model of the tire using the MATLAB/Simulink tool. Simulation analysis is performed under three distinct operating conditions: pure braking, pure cornering, and combined. The outcomes demonstrate that the mechanical properties of automotive tires can be effectively simulated using the Magic Formula tire model. Controlling the longitudinal slip ratio within a 10% range, maintaining the slip angle within a range of 7 degrees, and ensuring that the vertical load on the tire does not exceed 6 KN significantly contribute to enhancing the stability and handling of the vehicle.

Performance Evaluation Of Disconnected Piled Raft System Under Vertical And Lateral Loading

Performance Evaluation Of Disconnected Piled Raft System Under Vertical And Lateral Loading

Inverse finite element analysis for an axisymmetric model of vertical tooth extraction

Background and objectiveTooth extraction is a common clinical procedure with biomechanical factors that can directly influence patient outcomes. Recent development in atraumatic extraction techniques have endeavoured to improve treatment outcomes, but the characterization of extraction biomechanics is sparse. An axisymmetric inverse finite element (FE) approach is presented to represent the biomechanics of vertical atraumatic tooth extraction in an ex-vivo swine model. MethodsGeometry and boundary conditions from the model are determined to match the extraction of swine incisors in a self-aligning ex vivo extraction experiment. Material parameters for the periodontal ligament (PDL) model are determined by solving an inverse FE problem using clusters of data obtained from 10 highly-controlled mechanical experiments. A seven-parameter visco-hyperelastic damage model, based on an Arruda-Boyce framework, is used for curve fitting. Three loading schemes were fit to obtain a common set of material parameters. ResultsThe inverse FE results demonstrate good predictions for overall force-time curve shape, peak force, and time to peak force. The fit model parameters are sufficiently consistent across all three cases that a coefficient-averaged model was taken that compares well to all three cases. Notably, the initial modulus ,u, converged across trials to an average value of 0.472 MPa with an average viscoelastic constant g of 0.561. ConclusionsThe presented model is found to have consistent parameters across loading cases. The capability of this model to represent the fundamental mechanical characteristics of the dental complex during vertical extraction loading is a significant advancement in the modelling of extraction procedures. Future work will focus on verifying the model as a predictive design tool for assessing new loading schemes in addition to investigating its applications to subject-specific problems.

Estimation of nosing load in existing railway transom top bridges based on field testing and finite element modelling

A significant number of wind bracings in existing railway transom top bridges are numerically assessed deficient against the assessment nosing load recommended by the AS5100, where in almost all cases, there is no observed evidence of wind bracings being overloaded. This paper estimates the nosing load applied by various trains to a couple of random spans of an existing railway transom top bridge. Firstly, field testing of this bridge is conducted and the measured stresses at the mid-center of girders and wind bracings are collected during various normal train operations to validate the developed Finite Element (FE) models of this bridge. Then, the nosing loads due to different trains are estimated using the validated FE model through a two-staged validation approach, including automatic FE stress intensity optimization and rigorous manual FE model sensitivity analysis while transoms in various conditions are also incorporated in the FE model. Results demonstrate that the nosing load is significantly less than the required load in the AS5100 with magnitudes ranging between 8.6% to 9.4% of the maximum vertical axle load of the passed trains; suggesting that the AS5100 assessment nosing load should be revised to avoid unnecessary expensive upgrades of numerically assessed deficient wind bracings.

Powder coating waste filler in high‐density polyethylene – Variations in morphology, mechanical and thermal performance

AbstractIn the present study, electrostatic powder coating waste was recycled and employed to reinforce high‐density polyethylene. The hydrolysis method was preferred to modify the powder coating waste of various systems, and they were mixed with high‐density polyethylene at various weight ratios. The mixtures were prepared in a mechanical mixer and then in an extruder to obtain a homogeneous mixture. This homogeneous structure was pressed into molds with a plastic injection device to obtain standard tensile samples. Mechanical and thermal tests were conducted on the samples. It was determined that the tensile stress of the sample decreased with the increase in filler content. The changes in sample tensile strength were investigated after the samples were aged. Three‐point bending strength of the samples was also investigated and it was observed that they became more resistant to vertical loads as the filler content increased. The Izod impact strength of the samples differed based on the filler type and weight ratio. Furthermore, mass loss in the produced mixtures was determined with thermogravimetric analysis. The matrix and filler bonding mechanisms were observed under an electron microscope.

Car-trailer coupling devices - description of requirements and overview of flexible and static load measuring solutions

The article presents an overview of the current normative, national, and international documents, containing in their content the requirements for devices coupling a car with a trailer in terms of technical conditions that these devices must meet to confirm proper performance and ensure the possibility of safe use during exploitation before will go on sale. Attention was paid to the division of coupling devices of motor vehicles and trailers into classes according to Regulation 55 of the UN/ECE and the resulting requirements. The principles according to which it should be accepted that couplings meet the approval requirements are discussed, and the meaning and way equipment manufacturers determine the characteristic values of the indicated coupling parameters are explained. Requirements for the minimum and maximum loads exerted by the trailer on the coupling device are presented. Particular attention was paid to the existing technical solutions (including patent claims in the Patent Office of the Republic of Poland or in the European Patent Office) regarding coupling devices characterized by the possibility of measuring the static vertical force on the coupling and couplings with vertical flexibility (compliance), which can potentially reduce dynamic loads on the coupling device. Calculations focused on two practical applications are planned using the article's content and simulation. The first is the ability to assess the impact of introducing vertical compliance to the coupling device on its durability. The second is the ability to assess the impact of the value of the static vertical load of the coupling device (resulting from the trailer load and the longitudinal position of its center of mass) on the length of the braking distance of the combination: towing vehicle - trailer.

Experimental assessment of stainless-steel wire mesh (SSWM) strengthened wet precast beam-column connections

Connections are important elements of precast structures as they introduce discontinuity between the elements affecting strength and stiffness. In the present study, locally available SSWM 40 × 32 is explored as a strengthening material for precast beam column connections. Experiments are conducted on test specimens to evaluate their performance under monotonic vertical loading applied using hydraulic actuator. Various wet precast connections with different location of connections and detailing of beam column reinforcement are considered for this investigation. Two novel SSWM configurations like enclosure of junction with box shape strip and diagonal strips of SSWM are used for strengthening of precast beam column connections. Experimental study is conducted on twelve test specimens to measure their performance in terms of ultimate load capacity, displacement profile, ductility, failure pattern and energy dissipation. SSWM strengthened specimens show 8–43 % improvement in load carrying capacity along with better ductility and energy dissipation. For the precast connections at junction, box shape SSWM strip configuration is recommended while for the connection at the face of column, diagonal strip configuration of SSWM is recommended. Overall, SSWM can be effectively used for strengthening of precast connections.

Strut method for the analysis of Confined Masonry structure with opening subjected to vertical and lateral loads

Strut method for the analysis of Confined Masonry structure with opening subjected to vertical and lateral loads

An Experimental Study of High-Damping Rubber Bearings (HDRB) and Their Implications for the Seismic Performance of Cable-Stayed Bridges

This article investigates the efficiency of high damping rubber bearings (HDRB), which are made of special rubber with excellent damping attributes and layers of steel. HDRB isolators have excellent flexibility, vibration reduction ability, and high restoring ability for controlling the seismic response of long-span cable-stayed bridge systems under near-fault ground motions. The seismic isolation of cable-stayed bridges is achieved using high-damping rubber bearings (HDRB). High-damping rubber bearings have excellent seismic effects during earthquakes. The elastic stiffness of the bearing depends on the degree of deformation. When the deformation is small, the stiffness will be large. Therefore, compressive stiffness is one of the key parameters in the design of seismic isolation bearings for cable-stayed bridges. For this reason, predicting the behavior of high-damping rubber bearings under compressive loads is highly important for their design. Therefore, the experimental verification of high-damping rubber bearings (HDRB) for compressive loading was tested according to the standard assumptions in STN EN 1337-3. Firstly, periodic vertical compression tests are performed, and the high damping rubber (HDRB) capabilities and energy dissipation are analysed, taking into account the effect of vertical compression and loading frequency. Secondly, a corrected calculation of the vertical stiffness for high-damping rubber bearings is proposed based on experimental data to provide a more accurate and realistic tool for measuring the vertical mechanical properties of rubber bearings. The test results prove that HDRB has the most advanced performance. For the fatigue property, the hysteresis curves of the HDRB plump both vertically, which provides a good energy dissipation effect. DOI: https://doi.org/10.52783/pst.431

Vertical load distribution in precast hollow core floors: State of the art and future perspectives

AbstractPrecast prestressed hollow core (HC) floors are widely used in various applications within the construction sector. Such floors are usually designed as single, simply supported elements, although it is known that individual elements forming the floor interact with each other. This article presents the state of the art regarding load redistribution in HC floors in the light of experimental data, current analytical models and code provisions. While this phenomenon is widely known and recognized, only sparse, and often poorly documented experimental data are available, which represent the basis for the assessment and calibration of analytical models. Moreover, even though the available models and code provisions share similar assumptions, their outcomes are in some cases conflicting. Having recognized the existing knowledge gap, the authors outline future perspectives for the development of consistent analytical and numerical approaches supplemented by new experimental data.