Vertical Impact Load Research Articles

Impact resistance study of lime slag–stabilised steel slag mixes

ABSTRACT Given the transient nature of impact loading, exploring the microscopic damage characteristics and damage mechanisms of materials through indoor tests is difficult. In this study, the damage morphology and energy dissipation characteristics of lime slag–stabilised steel slag (LSSS) mixes under vertical impact loading is explored using ABAQUS software, a finite element model of LSSS for falling hammer impact test is established, the validity of finite element calculation is verified by comparing the results of indoor tests, and the strain characteristics, deflection changes, and energy transformation process of LSSS under vertical impact loading are analysed. Results show that the LSSS tensile and compressive strains under impact loading are roughly divided into low strain rate, precracking, and cracking phases with a rapid increase in strain. Under the same impact energy conditions, the LSSS bottom tensile strain, span deflection, drop hammer kinetic energy conversion time, and LSSS plastic energy consumption curve rising slope are sensitive to drop hammer mass. Thus, improvement in drop hammer mass will prolong the impact loading of the drop hammer–LSSS system internal energy conversion time, and the LSSS strain peak range to the central concentration, enhancing span deflection and bottom deformation.

The relationships between patellofemoral bone remodeling, cartilage composition, and vertical loading rate: PET/MRI in isolated patellofemoral osteoarthritis

ObjectiveLoading is invariably an important factor of consideration for understanding the causality flow and parallel existence of articular cartilage and subchondral bone changes. The goal of this study was to investigate the patterns of subregional 18NaF-SUV vs. T1p-T2 associations and vertical ground reaction force loading rates; in isolated patellofemoral-joint-osteoarthritis (PFJ-OA) patients. MethodThirty-five isolated PFJ-OA patients, with no tibiofemoral involvement, underwent simultaneous scans in a 3.0T whole-body hybrid PET-MRI scanner. MRI WORMS assessments were performed to identify/confirm isolated PFJ-OA knees from bilateral scans. T1p-T2 relaxation and SUV values were automatically computed for both trochlear and patellar cartilage and subchondral bone subregions (deep, superficial, lateral, and medial). Maximum vertical impact loading rates (Loading-RateNorm) were calculated from walking trials. Relationships were explored between SUV uptake, T1p-T2 values, and Loading-RateNorm via linear mixed-effects modeling. ResultsSignificant and complex association patterns were noted between medial and lateral bone 18NaF-SUV uptakes vs. medial and lateral cartilage sub-regional T1p and T2. SUVMean and SUVMax were positively associated with deep cartilage subregional T1pand T2 values; and negatively associated with superficial cartilage subregional T1p-T2 values in both medial and lateral regions. Both medial and lateral bone 18NaF-SUVMean and SUVMax uptakes remained positively associated with the individual gait characteristics, i.e., peak vertical impact loading rates (Loading-RateNorm). ConclusionEvidence of simultaneous, complementary, cross-sectional associations between T1p-T2 values and peak vertical loading rates with 18NaF-SUV, have been rare in the isolated PFJ-OA cohort. The clinical implications of such novel associations remain of utmost importance from a gait retraining perspective.

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.

Numerical model for suction anchor under vertical impact loading

In marine engineering, suction anchors are widely employed as the supporting foundation for many types of fixed or floating structures. One of the important control conditions for the service of marine foundations is the impact loading in extreme environments. This study proposes a numerical model to predict the dynamic behavior of suction anchors under impact loading. A mass module is added to the numerical model to quantify the effect of anchor inertia. The t-z springs are positioned along the depth to reflect the soil layer stress and accurately calculate the skirt wall friction. Considering the seepage effect, the differential pressure development, internal soil stress loss and external soil stress enhancement are also reflected. Subsequently, the influence of anchor aspect ratio and loading history are investigated. As the foundation uplift movement is further pronounced, the friction resistance gradually works, resulting in the weakening of inertial force. The existence of pretension loading makes friction resistance take effect earlier, and accelerates its attenuation during the impact loading stage.

Dynamic Responses of Single-Layer Reticulated Shells under Oblique Impact Loading

This paper focuses on the response of reticulated shell structures under oblique impact loads, with a departure from the traditional emphasis on vertical impact loads. These structures are typically utilised in large-span spaces such as iconic buildings and large venues. The study begins by establishing a numerical simulation method for reticulated shell structures subjected to oblique impact loads, which is then validated against existing experimental results. Building on this verified method, the research delves into the effects of varying impactor mass, velocity, and initial kinetic energy on the reticulated shell structure under oblique impacts, as well as the influence of different oblique impact angles. The study extensively examines the failure modes of the structure, node displacements in the structure, and variations in member stress under different impactor parameters. It further investigates how these parameters influence the maximum impact bearing capacity, impact duration, energy dissipation capability, and response forms of the structures, analyzing the reasons behind these effects. The findings offer valuable insights for further research and practical engineering design of reticulated shell structures.

How to walk to reduce footstep noise in multi-story residential buildings

Loud footsteps from upstairs cause disturbance to downstairs neighbours in multi-story residential buildings. In this experiment, we examined how participants walk when asked to walk quietly and evaluated the efficiency of their quiet walking patterns. Changes in vertical impact loading rates during the early stance phase, walking speed, and lower limb muscle activity when asked to walk quietly were evaluated from twenty-six young participants. Study data show that participants who struck the ground with the rearfoot reduced the impact loading rate by 44.6% with 29.3% slower walking speed than normal walking. Those who struck with the fore- or mid-foot reduced the impact loading by 69.2% with a 23.4% decrease in speed. Quiet walking with the non-rearfoot strike pattern reduced the impact loading by 48.7%, even when asked to walk as fast as normal walking. The results support the non-rearfoot strike pattern as an efficient walking strategy for lowering footstep impact. Practitioner summary: Data of this study show that voluntary gait alteration, such as adopting a non-rearfoot strike pattern, can reduce footstep impact. The study results propose that implementing such changes could be beneficial in addressing floor noise issues of multi-story residential buildings. Abbreviations: RFS: Rearfoot strike; NRFS: non-rearfoot strike; COP: Center of pressure; NW: Normal walking; QWs: Quiet walking at a preferred slower speed; QWn: Quiet walking at the speed of normal walking; EMG: Electromyography; BW: Body weight; iNEMG: integrated normalized EMG.

CFD-FEM simulation of water entry of aluminium flat stiffened plate structure considering the effects of hydroelasticity

In this paper, the slamming loads and structural response of an aluminium flat stiffened-plate structure during calm water entry considering the hydroelasticity effects are studied by a partitioned CFD-FEM two-way coupled method. The target structure is simplified as one segment of an idealized ship grillage structure, comprising flat plate and stiffeners. The typical numerical results are analyzed such as vertical displacement, velocity, acceleration, impact loads, and structural stress of the flexible flat bottom grillage structure considering the hydroelasticity effect and air cushion effect in different free fall height conditions. Drop test results of the same structure and other existing numerical simulation data by both coupled and uncoupled solutions in the literature are used for comparison with the present numerical simulation results. This study provides a practical means to simulate the slamming behaviour and structural response of ship structures, which is useful for predicting ship hull stiffened panel loads and related structural design.

The Impact of Excessive Body Weight and Foot Pronation on Running Kinetics: A Cross-Sectional Study

BackgroundRunning exercise is an effective means to enhance cardiorespiratory fitness and body composition. Besides these health benefits, running is also associated with musculoskeletal injuries that can be more prevalent in individuals with excessive body weight. Little is known regarding the specific effects of overweight and foot pronation on ground reaction force distribution during running. Therefore, this study aimed to investigate the effects of overweight/obesity and foot pronation on running kinetics.MethodsEighty-four young adults were allocated to four experimental groups: non-excessive body weight/non-pronated feet; non-excessive body weight/pronated feet; overweight or obesity/ non-pronated feet and overweight or obesity/pronated feet. Biomechanical testing included participants to run at ~ 3.2 m/s over an 18-m walkway with an embedded force plate at its midpoint. Three-dimensional ground reaction forces were recorded and normalized to body mass to evaluate running kinetics from 20 running trials. Test–re-test reliability for running speed data demonstrated ICC > 0.94 for each group and in total.ResultsThe results indicated significantly lower vertical impact peak forces (p = 0.001, effect size = 0.12), shorter time to reach the vertical impact peak (p = 0.006, effect size = 0.08) and reduced vertical loading rate (p = 0.0007, effect size = 0.13) in individuals with excessive body weight (overweight or obesity/non-pronated feet group and overweight or obesity/pronated feet) compared with individuals non-excessive body weight (non-excessive body weight/non-pronated feet and non-excessive body weight/pronated feet). Moreover, the excessive body weight groups presented lower peak braking (p = 0.01, effect size = 0.06) and propulsion forces (p = 0.003, effect size = 0.09), lower medio-lateral loading rate (p = 0.0009, effect size = 0.12), and greater free moments (p = 0.01, effect size = 0.07) when compared to the non-overweight groups. Moreover, a significant body mass by foot pronation interaction was found for peak medio-lateral loading rate. Non-excessive body weight/pronated feet, excessive body weight/non-pronated feet and excessive body weight/pronation groups presented lower medio-lateral loading rates compared to non-excessive body weight/non-pronated feet (p = 0.0001, effect size = 0.13).ConclusionsOur results suggest that excessive body weight has an impact on ground reaction forces during running. We particularly noted an increase in medio-lateral and torsional forces during the stance phase. Individuals with excessive body weight appear to adapt their running patterns in an effort to attenuate early vertical impact loading.

Numerical study on the anti-impact performance of novel concrete-filled steel tubular joint with corrugated web and cover plates

To improve the impact resistance of the traditional concrete-filled steel tubular (CFST) bolt-welded hybrid joint, a novel connection configuration with the corrugated web and the cover plate was proposed in this study. The failure modes and bearing mechanism of the novel connection under vertical dynamic impact load were studied in detail based on the finite element model validated against the previous test results. The falling-debris impact on top of the joint column can be simplified as the drop hammer of the non-deformed discrete shell rigid body. The effect of the design parameters including the dimensions of the cover plate and corrugated web was analyzed numerically. Results show that the existence of the cover plate increases the bending capacity of the steel beam and delays the fracture of the connection. The fracture and local buckling of the web are delayed due to the folding effect of the corrugated web. The energy consumption of the joint with the cover plate and the corrugated web is 20.2%–52.8% higher than that of the traditional joint, in which the corrugated web and bottom flange with cover plate contribute 6.6%–8.3% and 16.3%–32.2% respectively. The time history curves of the internal force of the joints are mainly consisted of the beam mechanism stage, the catenary mechanism stage and the failure stage. Through the parameter analysis, it is suggested that the long diameter of the bolt hole is 0.08–0.09 times of the beam height and the thickness of the cover plate is 0.42–0.50 times of the flange thickness to reach the optimum impact resistance. Furthermore, a simplified calculation method for the impact resistance considering the effect of the corrugated web and the cover plate is proposed. Impact energy can be absorbed by the bending effect and the catenary effect of the joint. The relative errors of the predicted impact resistance and energy absorption by theoretical formulas are within +10% compared with the experimental and numerical results.

Dynamic response and impact loads in twin-barge floatover installation

Complex impact loads during the floatover installation will threaten the mating operations. This paper presents the experimental investigation on the impact loads and dynamic response in the twin-barge floatover installation. In the model test, two critical loads transfer scenarios were modeled, including 0% and 100% stages in which the topsides are initially connected and separated from the barges. The near-zero gaps between the topsides and the twin-barge are simulated at two stages with the aim of investigating the collision characteristics. The impact loads on mating units, mooring forces, hawser forces, as well as motions of the twin-barge and the topsides were investigated. It is found that the windward barge motions are much larger than the leeward barge in sway, roll and yaw directions. The larger barge sway and yaw motions occurred at the 100% stage compared with the 0% stage. Statistical results indicate that the 100% stage seems to induce the larger impact loads on mating units than the 0% stage. The lateral impact loads were comparable with the vertical loads, in which the maximum lateral impact loads were even greater than the vertical impact loads. The mooring and hawser lines at the 100% stage are subjected to larger loads.

Sensitiveness of Variables Extracted from a Fitness Smartwatch to Detect Changes in Vertical Impact Loading during Outdoors Running.

Accelerometry is becoming a popular method to access human movement in outdoor conditions. Running smartwatches may acquire chest accelerometry through a chest strap, but little is known about whether the data from these chest straps can provide indirect access to changes in vertical impact properties that define rearfoot or forefoot strike. This study assessed whether the data from a fitness smartwatch and chest strap containing a tri-axial accelerometer (FS) is sensible to detect changes in running style. Twenty-eight participants performed 95 m running bouts at ~3 m/s in two conditions: normal running and running while actively reducing impact sounds (silent running). The FS acquired running cadence, ground contact time (GCT), stride length, trunk vertical oscillation (TVO), and heart rate. Moreover, a tri-axial accelerometer attached to the right shank provided peak vertical tibia acceleration (PKACC). The running parameters extracted from the FS and PKACC variables were compared between normal and silent running. Moreover, the association between PKACC and smartwatch running parameters was accessed using Pearson correlations. There was a 13 ± 19% reduction in PKACC (p < 0.005), and a 5 ± 10% increase in TVO from normal to silent running (p < 0.01). Moreover, there were slight reductions (~2 ± 2%) in cadence and GCT when silently running (p < 0.05). However, there were no significant associations between PKACC and the variables extracted from the FS (r < 0.1, p > 0.05). Therefore, our results suggest that biomechanical variables extracted from FS have limited sensitivity to detect changes in running technique. Moreover, the biomechanical variables from the FS cannot be associated with lower limb vertical loading.

Temporal corridors of forces and moments, and injuries to pelvis-lumbar spine in vertical impact simulating underbody blast

Pelvis and lumbar spine fractures occur in falls, motor vehicle crashes, and military combat events. They are attributed to vertical impact from the pelvis to the spine. Although whole-body cadavers were exposed to this vector and injuries were reported, spinal loads were not determined. While previous studies determined injury metrics such as peak forces using isolated pelvis or spine models, they were not conducted using the combined pelvis-spine columns, thereby not accounting for the interaction between the two body regions. Earlier studies did not develop response corridors. The study objectives were to develop temporal corridors of loads at the pelvis and spine and assess clinical fracture patterns using a human cadaver model. Vertical impact loads were delivered at the pelvic end to twelve unembalmed intact pelvis-spine complexes, and pelvis forces and spinal loads (axial, shear and resultant and bending moments) were obtained. Injuries were classified using clinical assessments from post-test computed tomography scans. Spinal injuries were stable in eight and unstable in four specimens. Pelvis injuries included ring fractures in six and unilateral pelvis in three, sacrum fractures in ten, and two specimens did not sustain any injuries to the pelvis or sacrum complex. Data were grouped based on time to peak velocity, and ± one standard deviation corridors about the mean of the biomechanical metrics were developed. Time-history corridors of loads at the pelvis and spine, hitherto not reported in any study, are valuable to assess the biofidelity of anthropomorphic test devices and assist validating finite element models.

Inter-muscular coordination during running on grass, concrete and treadmill.

Running is an exercise that can be performed in different environments that imposes distinct foot-floor interactions. For instance, running on grass may help reducing instantaneous vertical impact loading, while compromising natural speed. Inter-muscular coordination during running is an important factor to understand motor performance, but little is known regarding the impact of running surface hardness on inter-muscular coordination. Therefore, we investigated whether inter-muscular coordination during running is influenced by running surface. Surface electromyography (EMG) from 12 lower limb muscles were recorded from young male individuals (n = 9) while running on grass, concrete, and on a treadmill. Motor modules consisting of weighting coefficients and activation signals were extracted from the multi-muscle EMG datasets representing 50 consecutive running cycles using non-negative matrix factorization. We found that four motor modules were sufficient to represent the EMG from all running surfaces. The inter-subject similarity across muscle weightings was the lowest for running on grass (r = 0.76 ± 0.11) compared to concrete (r = 0.81 ± 0.07) and treadmill (r = 0.78 ± 0.05), but no differences in weighting coefficients were found when analyzing the number of significantly active muscles and residual muscle weightings (p > 0.05). Statistical parametric mapping showed no temporal differences between activation signals across running surfaces (p > 0.05). However, the activation duration (% time above 15% peak activation) was significantly shorter for treadmill running compared to grass and concrete (p < 0.05). These results suggest predominantly similar neuromuscular strategies to control multiple muscles across different running surfaces. However, individual adjustments in inter-muscular coordination are required when coping with softer surfaces or the treadmill's moving belt.

Numerical investigation of wave run-up and impact forces on large offshore jacket platforms

This paper focuses on wave interactions with large deep-sea jacket platforms. A numerical wave tank is designed and developed to simulate the wave-structure interactions, and the accuracy and precision of this numerical wave tank are verified by the theoretical values and LWI experimental tests. Then the processes of wave run-up along with the legs and impact the lower deck of a large deep-sea jacket platform located at the South China Sea are simulated, analyzed, and discussed. The results show that the greater the wave steepness, the stronger the wave run-up ability. The wave run-up processes are mainly concentrated within a radius R around the legs, and the maximum wave run-up ratio reaches 1.56 on the front side of leg 1 when the wave steepness is 0.03. Due to the interference, reflection, and superposition effects, all the legs show different wave run-up characteristics, and additional high-frequency side wave peaks are observed around the legs, which are mainly focused on 0–0.6 Hz in the frequency domain. With the increase of wave steepness λ, the wave drag forces increase significantly during the wave run-up processes. Especially, when the waves impact the lower deck under case 3, it will cause huge vertical wave impact loads, and the maximum value reaches 46.59 MPa, which will cause further attenuation to the vertical and lateral resistance of the jacket platform.

Wave impacts on a solid deck in transient wave groups

Wave impacts on an elevated solid deck due to transient focused wave groups are studied numerically. Previously reported experiments with and without an I-beam grillage beneath the deck by Santo et al. (2020) are reproduced successfully in a three-dimensional numerical wave tank based on a two-phase Navier–Stokes solver. The impact loads on the solid deck are relatively simple. The three-dimensional horizontal force, characterised by a single peak in time, is close to two-dimensional, whereas the vertical force consists of upward force and downward suction force. The downward suction force is related to triangularisation of the wetted area underneath the deck and dominated by the added mass effect, which is a three-dimensional effect and therefore any two-dimensional simulation will overpredict the strongly three-dimensional process and the vertical impact loads. The wave impact loads on the solid deck with a grillage are more complicated, with successive force spikes observed for both the horizontal and vertical loads. The significance of entrapped air pockets in the grillage to global wave impact loads is ascertained through interrogating flow field of numerical experiments. It is found that large upward vertical impulsive forces are caused by high local pressures when entrapped down-wave air-pockets are formed, while large downward suction forces are resulted from both high-frequency up-wave air-pocket effect and the low-frequency added mass effect. Large horizontal impulsive forces are due to the combined effects of the down-wave air-pocket and the upward jetting motion of the wave crests. The entrapped air-pocket effects are found to be more important for vertical than horizontal forces.

Experimental Study for Downfall Pressure on the Floor behind Rubble-Mound Structure by Wave Overtopping: Non-Breaking Condition

The large uprush could be occurred when the waves hit the coastal structure and this uprush by wave could make the overtopping. The downfall of the wave overtopping water over the structure brought about the vertical impact loads. The vertical impact loads should be evaluated in order to design the pavement behind the crown wall however these loads were still unclear. In this study, the hydraulic model tests for the downfall impact loads by wave overtopping were performed and the various conditions were applied to the tests. The effect of the incident wave condition, the freeboard, the armour crest height and the height of the parapet were investigated. The test results showed that the parapet on the crown wall could reduce the wave overtopping however the inclusion of parapet could lead to the increased downfall wave pressures behind the crown wall. The empirical formulae were proposed for evaluating the maximum downfall pressures behind the crown wall of rubble mound structure.

Residual performance and damage mechanism of prestressed concrete box girder bridge subjected to falling heavy object impact

Extreme vertical impact loading from dropped heavy cargo or falling rocks threatens the safety of bridge structures. The impact behavior and post-impact performance of a multi-piece prestressed concrete (PC) box girder bridge were investigated through numerical simulation. The moment-curvature analysis was performed to explain the damage mechanism and to predict the residual capacity of the girder under impact. The results demonstrate that the impacted girder suffers the most severe flexural failure whereas the other un-impacted girders exhibit flexural-torsional combined damage type. The impacted girder suffers from flexural failure to shear failure if the impact position on the girder transfers from mid-span to support. The increased impact energy deteriorates the damage of impacted girder while has little influence on the un-impacted girder. When the impact area decreases due to the varying impact angle, the displacement and impact force of the impacted girder reduce whereas local damage becomes more severe. The residual stiffness and resistance decrease significantly as the impact energy raises. It is concluded that severe concrete damage of top plate diminishes the flexural capacity of impacted girder.

Spatiotemporal and Ground-Reaction Force Characteristics as Risk Factors for Running-Related Injury: A Secondary Analysis of a Randomized Trial Including 800+ Recreational Runners

Background: Running biomechanics may play a role in running-related injury development, but to date, only a few modifiable factors have been prospectively associated with injury risk. Purpose: To identify risk factors among spatiotemporal and ground-reaction force characteristics in recreational runners and to investigate whether shoe cushioning modifies the association between running biomechanics and injury risk. Study Design: Case-control study; Level of evidence, 3. Methods: Recreational runners (N = 848) were tested on an instrumented treadmill at their preferred running speed in randomly allocated, standardized running shoes (with either hard or soft cushioning). Typical kinetic and spatiotemporal metrics were derived from ground-reaction force recordings. Participants were subsequently followed up for 6 months regarding running activity and injury. Cox regression models for competing risk were used to investigate the association between biomechanical risk factors and injury risk, including stratified analyses by shoe version. Results: In the crude analysis, greater injury risk was found for greater step length (subhazard rate ratio [SHR], 1.01; 95% CI, 1.00-1.02; P = .038), longer flight time (SHR, 1.00; 95% CI, 1.00-1.01; P = .028), shorter contact time (SHR, 0.99; 95% CI, 0.99-1.00; P = .030), and lower duty factor (defined as the ratio between contact time and stride time; SHR, 0.95; 95% CI, 0.91-0.98; P = .005). In the stratified analyses by shoe version, adjusted for previous injury and running speed, lower duty factor was associated with greater injury risk in those using the soft shoes (SHR, 0.92; 95% CI, 0.85-0.99; P = .042) but not in those using the hard shoes (SHR, 0.97; 95% CI, 0.91-1.04; P = .348). Conclusion: Lower duty factor is an injury risk factor, especially for softer shoe use. Contrary to widespread beliefs, vertical impact peak, loading rate, and step rate were not injury risk factors in recreational runners. Registration: NCT03115437 (ClinicalTrials.gov identifier).

Static and dynamic plate loading tests of stabilized soil samples used for riverbank consolidation

Building of an experimental slope protection system on Căpuş river, near Cluj presented the opportunity of in situ testing of stabilized soils. Different hydraulic binder was used on each side of the river, so this testing series provided valuable data about deformability properties of the encountered soil types. There are some deformability parameters used in Romania which were “imported” at the specific request of foreign investors. The strain modulus, Ev, is a parameter expressing the deformation characteristics of a soil and is calculated taking values from the load-settlement curve obtained from the first and second loading cycle, on a static plate load test. In earthworks, the dynamic plate load test using the Light Falling Weight Deflectometer may be used for testing load-bearing capacity as an alternative to the static plate load test which provides the strain modulus, Ev parameter. Dynamic modulus of deformation Evd is a parameter for the deformability of soil under a defined, vertical impact load with the impact duration. Its value is being calculated with the maximum settlement of the load plate. None of these methods made way into official Romanian standardisation, the Evd is subject of a technical agreement, which also contains the correlation of it with Ev. Conducting both static and dynamic loading tests enabled the verification of validity of relation between strain modulus and dynamic modulus.

Out-of-round tram wheels – Multibody simulation study based on measured wheel rim geometry

The article discusses the influence of out-of-roundness ( OOR) type of wheel shape deviations on its interaction with the rail. The analysis was carried out using multibody simulation technique ( MBS). Measurements of tram wheel rims and sample models of flat spots were used as input data. It has been observed that the presence of wheel OOR deviations caused a significant increase in vertical impact loads at the interface between the wheel and the rail, which favours rolling contact fatigue formation. Deviations created at the stage of manufacturing the wheel rim (usually while the profile of the rim itself is turned on a lathe) were amplified by increasing amplitudes and were also visible during the measurement of worn rims, thus creating inequalities with dominant amplitudes. Flat spots present on the rolling surfaces of the wheels cause cyclic jumps of vertical force at the contact point of the wheel and the rail, with maximum values depending on the depth and radius of the rounded edges of the flat spot, and thus subject to change in subsequent stages of the flat spot development. Taking into account the observations made, preventive measures have been proposed against the development of OOR deviations in tram wheels, the origin of which is primarily in the machining process.