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1

Comparative analysis of dynamic load models generated by runners on footbridges

Pańtak Marek

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

147--162

EN

Footbridges, like all building structures, must be designed in a way that ensures their safe and comfortable use. Steel footbridges characterised by low vibration damping often turn out to be a structure susceptible to the dynamic influence of users during various forms of their activity. For these structures, the impact of running users may be a key type of dynamic load for the verification of the serviceability limit state due to vibrations. In the literature, there are several proposals for models of dynamic load generated by runners (models of ground reaction forces - GRF). The paper presents the characteristics, analyses and comparisons of selected GRF load models. The analyses were performed using the GRF recorded during the laboratory tests of runners (tests planned and carried out by the author) and the GRF determined using various load models. In order to illustrate the accuracy of the estimation of the dynamic response of the structure, depending on the GRF model used, dynamic field tests and dynamic numerical analyses of the selected steel footbridge were carried out. The obtained results were analysed and compared.

PL

W artykule przedstawiono charakterystyki i analizy porównawcze wybranych modeli GRF. Analizy przeprowadzono z wykorzystaniem GRF zarejestrowanych podczas badań laboratoryjnych osób biegnących (badania własne autora) oraz GRF wyznaczonych z wykorzystaniem różnych modeli. W celu zobrazowania dokładności oszacowania odpowiedzi dynamicznej konstrukcji, w zależności od zastosowanego modelu GRF, przeprowadzono dynamiczne badania terenowe oraz dynamiczne analizy numeryczne stalowej kładki dla pieszych podatnej na oddziaływanie osób biegnących. Przeprowadzone analizy pozwoliły ustalić poprawność odwzorowania przebiegów GRF oraz dokładność wyznaczania odpowiedzi dynamicznej konstrukcji narażonych na dynamiczne oddziaływanie osób biegnących. W artykule przedstawiono własne zalecenia dotyczące modelowania oddziaływania osób biegnących na kładki dla pieszych oraz własne zalecenia dotyczące doboru parametrów wybranych modeli GRF opracowane na podstawie własnych badań sił reakcji podłoża generowanych podczas biegu. Zalecenia te pozwalają zwiększyć dokładność odwzorowania przebiegów GRF oraz dokładność oszacowania odpowiedzi dynamicznej konstrukcji narażonych na dynamiczne oddziaływanie osób biegnących. W szczególności: zaproponowano rozróżnianie technik biegu w celu dokładniejszego odwzorowania oddziaływań dynamicznych osób biegnących na konstrukcje, przedstawiono wartości współczynników Fouriera i przesunięć fazowych dla różnych technik biegu na potrzeby modelu bazującego na szeregu Fouriera, przedstawiono zalecenia dotyczące doboru wartości czasu kontaktu stopy z podłożem tcr dla różnych technik biegu na potrzeby modelu półsinusoidalnego (ang.: half-sine model), przedstawiono zalecenia dotyczące maksymalnych amplitud GRF dla różnych technik biegu oraz scharakteryzowano własną propozycję odwzorowania przebiegów GRF za pomocą funkcji Gaussa.

2

How to teach safe landing after the jump? The use of biofeedback to minimize the shock forces generated in elements of modern dance

Gorwa Joanna, Michnik Robert, Nowakowska-Lipiec Katarzyna

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 3

47--59

EN

Purpose: The aim of the study was to assess the possible use of biofeedback (information on the course and values of ground reaction forces (GRF) during landing following the performance of a dance evolution) for training minimising impact loads after a jump in modern dance. Methods: The tests involved the analysis of a total of 60 expressive elements of modern dance performed by 5 soloists. The tests involved the recording of the vertical component of GRF (GRFz) vector using Kistler platform in the landing phase following the performance of modern dance jumps. The dancers performed the above-named jumps three times in successive tests: a reference test (without biofeedback) and the next two tests with biofeedback, after the obtainment of information about the vertical value of GRF. After each performance, the dancers watched a course of GRF and films showing the recorded landing phase. Results: Applying of a proposed didactic laboratory session led to: extension of contact time and of time preceding the obtainment of the maximum value of GRFz, reduction of the maximum values of the vertical components of the GRF, reduction of the loading rate of the ground reaction force, increase of an impulse of the vertical component of GRF in the entire stance phase and in the shock absorption phase. Conclusions: Proposed didactic laboratory session with biofeedback may result in the change of the post-jump shock absorption technique.

3

Biomechanical evaluation of swing-through crutch gait in patients with lower extremity injury

Rzepnicka Agata, Kabaciński Jarosław, Murawa Michał, Fryzowicz Anna, Syczewska Małgorzata, Dworak Lechosław Bogdan

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 1

111--117

EN

The main purpose was to determine the values of spatio-temporal parameters and ground reaction forces during the swingthrough crutch gait. Methods: Eighteen male patients with unilateral injury within the foot, ankle or shank (age: 25.4 ± 7.7 years, body height: 1.79 ± 0.06 m, body mass: 76.1 ± 11.5 kg) participated in the study. In the experiment, 6-camera optoelectronic motion capture system and force platform were used. The measurements of spatio-temporal parameters and ground reaction force (GRF) were performed for uninjured lower extremity (ULE), crutch on the ULE side (CrU) and crutch on the injured lower extremity side (CrI). Results: Analysis demonstrated a significantly longer stance phase and a significantly shorter swing phase for ULE than crutches ( p < 0.05), and a significantly longer first, compared to the second, double support phase ( p < 0.05). Comparisons showed also significantly higher maximum values of the vertical GRF and extreme values of the horizontal antero-posterior GRF for ULE than crutches ( p < 0.05) as well as for CrI than CrU ( p < 0.05). Conclusions: The present study provides biomechanical data related to the spatio-temporal parameters and GRFs for the swing-through crutch gait in patients with the lower extremity injuries.

4

Investigation of the effects of flat cushioning insole on gait parameters in individuals with chronic neck pain

Kirmizi Muge, Simsek Ibrahim Engin, Elvan Ata, Akcali Omer, Angin Salih

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 2

135--141

EN

Individuals with chronic neck pain (CNP) walk with a stiffer spine known to cause an increase in dynamic loading on the spine. They also exhibit altered spatiotemporal gait variables, however, it is still unclear whether flat cushioning insole, which reduces dynamic loading on the musculoskeletal system by absorbing the ground reaction force, affects gait parameters in individuals with CNP. The aim of this work was to investigate the effects of flat cushioning insole on neck pain during walking and gait parameters in individuals with CNP. Methods: Twenty-one individuals with CNP and 21 asymptomatic controls were included. Assessments of gait parameters and pain were conducted in two sessions, standard shoe only and standard shoe with flat cushioning. In both sessions, all participants performed the 10-meter walk test in two walking conditions: preferred walking, walking at maximum speed. The force sensitive insoles and the video analysis method were used to assess plantar pressure variables and spatiotemporal gait variables, respectively. Pain was assessed using the Visual Analogue Scale. Results: Our results indicated that flat cushioning reduced the maximum force and force-time integral in both groups ( p < 0.05). Flat cushioning increased walking speed and step length in both walking conditions and reduced neck pain during walking at maximum speed in individuals with CNP ( p < 0.05). In asymptomatic individuals, no difference was found in spatiotemporal gait variables between two sessions ( p > 0.05). Conclusions: These results have suggested that the use of flat cushioning insole may improve neck pain during walking and spatiotemporal gait variables in individuals with CNP.

5

A 4-link model of a human for simulating a forward fall

Grzelczyk D., Biesiacki P., Mrozowski J., Awrejcewicz J.

Vibrations in Physical Systems

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2018

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Vol. 29

art. no. 2018008

EN

In this paper we consider a 4-link model of a human for simulating a forward fall. The model implemented in Mathematica is constructed based on a planar mechanical system with a non-linear impact law modelling the wrist-ground contact. The segments of the human body are modelled as bodies connected by rotary elements which correspond to the human joints. Parameters and kinematic relations used in numerical analysis are obtained based on the 3D scanned model of the human body created in Inventor and experimental observation by the motion capture system. Validation of the model is conducted by means of comparing the simulation of the impact force with the experimental data obtained from the force platform. The obtained ground reaction forces can be useful for the finite element analysis of the numerical model of the human upper extremity.

6

Dynamic simulation of a novel “broomstick” human forward fall model and finite element analysis of the radius under the impact force during fall

Grzelczyk D., Biesiacki P., Mrozowski J., Awrejcewicz J.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 1

239--253

EN

The paper presents dynamic simulation and experimental identification of a human forward fall model describing the process of “falling like a broomstick” on the outstretched arms. The model implemented in Mathematica allows one to estimate time histories of the ground reaction force in different scenarios of the fall process. These time series are applied as time-varying load conditions to the numerical analysis of the human radial bone model created from the computed tomography data. Finally, the obtained numerical results indicate that the strain criterion seems to be more useful for estimating the radius fracture site in comparison to the stress criterion.

7

Parkinson's disease monitoring from gait analysis via foot-worn sensors

Aşuroğlu T., Açıcı K., Erdaş Ç. B., Toprak M. K., Erdem H., Oğul H.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 3

760--772

EN

Background: In Parkinson's disease (PD), neuronal loss in the substantia nigra ultimate in dopaminergic denervation of the stiratum is followed by disarraying of the movements' preciseness, automatism, and agility. Hence, the seminal sign of PD is a change in motor performance of affected individuals. As PD is a neurodegenerative disease, progression of disability in mobility is an inevitable consequence. Indeed, the major cause of morbidity and mortality among patients with PD is the motor changes restricting their functional independence. Therefore, monitoring the manifestations of the disease is crucial to detect any worsening of symptoms timely, in order to maintain and improve the quality of life of these patients. Aim: The changes in motion of patients with PD can be ascertained by the help of wearable sensors attached to the limbs of subjects. Then analysing the recorded data for variation of signals would make it possible to figure an individualized profile of the disease. Advancement of such tools would improve understanding of the disease evolution in the long term and simplify the detection of precipitous changes in gait on a daily basis in the short term. In both cases the apperception of such events would contribute to improve the clinical decision making process with reliable data. To this end, we offer here a computational solution for effective monitoring of PD patients from gait analysis via multiple foot-worn sensors. Methods: We introduce a supervised model that is fed by ground reaction force (GRF) signals acquired from these gait sensors. We offer a hybrid model, called Locally Weighted Random Forest (LWRF), for regression analysis over the numerical features extracted from input signals to predict the severity of PD symptoms in terms of Universal Parkinson Disease Rating Scale (UPDRS) and Hoehn and Yahr (H&Y) scale. From GRF signals sixteen time-domain features and seven frequency-domain features were extracted and used. Results and conclusion: An experimental analysis conducted on a real data acquired from PD patients and healthy controls has shown that the predictions are highly correlated with the clinical annotations. Proposed approach for severity detection has the best correlation coefficient (CC), mean absolute error (MAE) and root mean squared error (RMSE) values with 0.895, 4.462 and 7.382 respectively in terms of UPDRS. The regression results for H&Y Scale discerns that proposed model outperforms other models with CC, MAE andRMSE with values 0.960, 0.168 and 0.306 respectively. In classification setup, proposed approach achieves higher accuracy in comparison with other studies with accuracy and specificity of 99.0% and 99.5% respectively. Main novelty of this approach is the fact that an exact value of the symptom level can be inferred rather than a categorical result that defines the severity of motor disorders.

8

Determination of a ground reaction force affecting human body during jump

Karpiński R., Jaworski Ł.

Journal of Technology and Exploitation in Mechanical Engineering

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2016

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Vol. 2, nr 1

32--35

EN

The article presents a study on calculating the ground reaction force, which affects the human body during landing after the jump. A basic, one mass model of human body and an equation of movement are presented in the paper. The model for the studies was created in Adams software and the study on a change of the ground reaction force was performed by using different values of height and mass.

PL

Artykuł opisuje metodę wyznaczania siły reakcji podłoża oddziałującej na ciało człowieka podczas zeskoku. W pracy przedstawiono prosty, jednomasowy model ciała człowieka wraz z opisującym go równaniem ruchu. Zbudowano model ciała w środowisku Adams, a następnie przeprowadzono obliczenia siły reakcji podłoża dla różnych wysokości i mas.

9

Analiza obciążeń kończyny dolnej podczas wykonywania ćwiczeń na stepie

Jochymczyk-Woźniak K., Bonk A.

Aktualne Problemy Biomechaniki

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2014

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z. 8

51--56

PL

Grupę badawczą stanowiły cztery studentki bez jakiegokolwiek doświadczenia w step aerobiku. Zadanie ruchowe polegało na 15-krotnym powtórzeniu, bez przerwy, kroku basic step dla dwóch wysokości stepu-10 cm i 15cm. Parametry, które zostały wykorzystane do oceny obciążeń działających na kończyny dolne oraz stopy człowiek, to: składowa pionowa siły reakcji podłoża, współczynnik obciążenia oraz siły nacisku stopy na podłoże. Badania przeprowadzono z wykorzystaniem platform dynamometrycznych AMTI oraz wkładek do pomiaru sił reakcji podłoża MEDILOGIC.

EN

Step aerobics is a very intense and exhausting physical activity. Classes are led with using the platform, which height is being regulated behind the help so-called floors. Aim of this study is to analyze the loads acting on the human movement during basic step. The studies are preliminary research introducing into issues connected from burdens of human movement during exercise on the step.

10

Ground reaction force analysed with correlation coefficient matrix in group of stroke patients

Szczerbik E., Krawczyk M., Syczewska M.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 2

3--9

EN

Stroke is the third cause of death in contemporary society and causes many disorders. Clinical scales, ground reaction force (GRF) and objective gait analysis are used for assessment of patient’s rehabilitation progress during treatment. The goal of this paper is to assess whether signal correlation coefficient matrix applied to GRF can be used for evaluation of post-stroke patients status. Group of patients underwent clinical assessment and instrumented gait analysis simultaneously three times. The difference between components of patient’s GRF (vertical, fore/aft, med/lat) and normal ones (reference GRF of healthy subjects) was calculated as correlation coefficient. Patients were divided into two groups (“worse and better”) based on the clinical functional scales tests done at the beginning of rehabilitation process. The results obtained by these two groups were compared using statistical analysis. Increase of median value of correlation coefficient is observed in all components of GRF, but only in non-paretic leg. Analysis of GRF signal can be helpful in assessment of post-stroke patients during rehabilitation. Improvement in stroke patients was observed in non-paretic leg of the “worse” group. GRF analysis should not be the only tool for objective validation of patient’s improvement, but could be used as additional source of information.

11

Statyczne i dynamiczne testy równowagi u osób trenujących Taekwondo

Podbielska M., Senhadri H., Kuczyński M.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2013

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Vol. 19, nr 2

79--84

PL

Równowaga dynamiczna i statyczna oceniania była u osób w wieku 19 do 27 lat, trenujących Taekwondo i w grupie kontrolnej, nieuprawiającej aktywności fizycznej. Równowaga statyczna była mierzona w czasie 20 s spokojnego stania na platformie stabilograficznej. Równowaga dynamiczna oceniana była przez 2,5 s po skoku na platformę i zeskoku z platformy. Nie stwierdzono znaczących różnic w równowadze statycznej pomiędzy grupami. W grupie osób uprawiających Taekwondo zmierzono mniejsze zmiany sił reakcji podłoża po skoku jednonożnym na platformę niż u osób nieuprawiających sportu, co dowodzi lepszej równowagi dynamicznej.

EN

Static and dynamic postural stability was tested on a force plate between recreational Taekwondo athletes (TAE) and subjects who were not involved in any systematic sports activities (CON) aged 18 to 27 years. The static stability was measured in single- and double-leg 20 s quiet stance. The dynamic stability was assessed by the standard deviation of the ground vertical forces during 2.5 s period after landing in two tests: hopping and leaping on the force plate. The results revealed similar postural sway in TAE and in CON groups during a 20-sec quiet stance indicating that the traditional interpretation of stabilographic findings may be sometimes misleading in the assessment of postural performance in athletes. However, the vertical force variability that resulted from a single-leg hopping on the force plate was much lower in athletes than in controls.

12

Estimated ground reaction force in normal and pathological gait

Winiarski S., Rutkowska-Kucharska A.

Acta of Bioengineering and Biomechanics

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2009

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Vol. 11, nr 1

53-60

EN

In clinical gait analysis, ground reaction force (GRF) is the gait parameter which can validate the state of disorder of the patient's movement. The purpose of this study was to explore the possibilities of employing the GRF derived from kinematics of the center of gravity (COG) in the study of dynamics of human gait. Gait data was collected for healthy able-bodied men and women and patients after ACL reconstruction who use larger lateral COG excursions during gait. Reasonable agreement between methods was found in fore-aft and vertical directions, where the methods differed by an average of less than 10% in either direction. Based on model predictions of the body's COG trajectory during walking, algorithms were developed to determine spatio-temporal gait parameters related to GRF characteristics. The suitability of calculating ground reaction forces using COG displacement in a patient population is questioned.

13

Peak ground reaction force and loading rate from kinematics in the ACL deficient patients

Winiarski S., Siemieński A.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2006

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z. 26

377-382

EN

In clinical gait analysis ground reaction force measurement is the gait parameter which can validate the state of disorder of the patient's movement. 3D kinematic gait analysis was conducted on normal and ACL-deficient subjects to test the usefulness of ground reaction force (GRF) measurement obtained from the kinematic data of the body center of gravity (COG) in clinical condition. The 3D displacement of the COG was calculated using the Clauser model and acceleration was calculated using double differential operation. Peak force and loading rate in gait was estimated from kinematics and directly from force plate measurement.