Compared to other age groups, older adults are at more significant risk of hip fracture when they fall. In addition to the higher risk of falls for the elderly, fear of falls can reduce this population's outdoor activity. Various preventive solutions have been proposed to reduce the risk of hip fractures ranging from wearable hip protectors to indoor flooring systems. A previously developed rubberized asphalt mixture demonstrated the potential to reduce the risk of head injury. In the current study, the capability of the rubberized asphalt sample was evaluated for the risk of hip fracture for an average elderly male and an average elderly female. A previously developed human body model was positioned in a fall configuration that would give the highest impact forces toward regular asphalt. Three different rubber contents with 14, 28, 33 weight percent (% wt.) were implemented as the ground alongside one regular non -rubberized (0%) asphalt mixture, one baseline, and one extra -compliant playground rubber -composite material. The whole -body model was simulated to fall on the rubberized asphalt mixtures with an initial vertical velocity of 3 m/s with a 10 degrees trunk angle and +10 degrees anterior pelvis rotation. The impact forces were measured on the femoral head, and a previously developed hip fracture risk function was used to compare the rubberized asphalt mixtures. It was found that the rubberized asphalt mixture with 33% wt. rubber can reduce the impact forces up to 10% for the elderly male and female model compared to regular asphalt. The impact forces were most reduced for the extra -compliant playground material, with a 23% reduction for the female model. The risk of injury for the asphalt mixture with 33% wt. rubber was reduced up to 18% for elderly females and 20 for elderly males, compared to regular asphalt. The extra -compliant playground material had the most reduction of hip fracture risk for both sexes, 39 and 43% for elderly females and males, respectively.

Objective: Vulnerable Road Users (VRU), including pedestrians and cyclists, are generally the leastprotected road users and are frequently missed in the planning process of preventive measures.Rubberized asphalt mixtures were originally developed as a possible environmentally friendly solutionto recycle the End-of-Life Tires while making the pavements more durable. The objective ofthe current study was to explore the effects of increasing the rubber content of the common rubberizedasphalt mixtures in reducing the head injuries risk for VRUs.Method: To achieve this purpose, four different sample series with 0, 14, 28, and 33 weight percentrubber in each were tested. A compressive test without permanent deformation and onewith failure were performed on each sample series. The mechanical behavior of each set wasmodeled using a MAT_SIMPLIFIED_RUBBER material model in LS-Dyna and validated against astandard Head Injury Criterion (HIC) drop test. Ultimately, previously low-speed accident reconstructedcases, a bicycle and a pedestrian one, were used to assess the effect of varying the rubbercontent on reducing the head injury risk.Results: In the bicycle accident case, the risk of skull fracture was reduced from 0.99 to 0.29 whencomparing the non-rubberized asphalt mixture with the 33% rubber mixture. In the same accidentcase, the risk of concussion, evaluated using the logistic regression method, was reduced from0.97 in the non-rubberized mixture to 0.81 in the 33% rubber mixture. The initial conditions, linearand rotational velocities, were lower for the pedestrian case compared to the bicycle case (thebicycle case was more severe compared to the pedestrian case), which led to lower strains in thepedestrian case. In the pedestrian accident case, the risk of skull fracture was reduced from 1.00in the non-rubberized mixture to 0.63 in the 33% rubber mixture, while the risk of concussion wasreduced from 0.64 to 0.07.Conclusion: The rubberized asphalt mixtures could reduce the head injury risk for the studiedcases when the rubber content in the asphalt mixture increases.

A fall is a serious health issue for the elderly. Among different fall types, the sideways fall is considered to be more severe concerning the injury outcome. When elderlies experience an unintentional sideways fall, they can either resist the impact forces with the soft tissue force attenuation capacity and femoral strength or need external protections to reduce the injury risk. In this thesis, these two aspects were investigated. Finite element whole-body models are valuable tools for analyzing fall biomechanics and investigating the possible preventive measures more conveniently. The whole-body models were developed to investigate traffic accidents; however, a sideways fall has different kinematics than the other types of accidents. Consequently, it is necessary to enhance the whole-body models according to the major fall parameters leading to severe injury cases before assessing the external protection capabilities.The current thesis attempted to advance these two critical aspects regarding fall-induced injuries. A finite element whole-body model was chosen to study three critical parameters in fall biomechanics: body posture, soft tissue, and femoral strength. The whole body model was positioned in different body configurations relevant for the sideways fall to evaluate the body posture that could lead to the highest internal forces on the femoral head. Next, different soft tissue constitutive material models and soft tissue thicknesses were investigated to find a material model that could accurately reproduce the experimental results according to an objective rating method named CORrelation and Analysis (CORA). Finally, the separate and combined effects of geometrical and mechanical properties change due to aging on femoral strength were assessed for the elderly males and females. In the second aspect of the thesis, the shock-absorbing rubberized asphalt pavements' preventive capacity was examined. First, different rubberized asphalt mixtures were implemented in a bicycle and a pedestrian accident reconstruction cases to evaluate the head injury risks. Later, the asphalt mixtures were studied in a sideways fall scenario to evaluate the hip fracture risk in an elderly male and female.

The first aspect of the thesis presented the results and methods to improve the sideways fall analysis, and the second aspect of the thesis focused on assessing the rubberized asphalt mixtures for injury prevention purposes. The sideways fall with the upright trunk and a slightly forward-tilted pelvis could lead to the highest internal forces. A nonlinear Ogden material model for muscle tissue and a Mooney-Rivlin material model for adipose tissue scored better among different soft tissue material models in the side impacts to the hip segments. The geometrical and mechanical properties change due to aging leading to a different behavior for males and females, where females experience a higher rate of strength loss due to aging. Moreover, it was indicated that a rubberized asphalt mixture could reduce the head injury risk for pedestrians and cyclists and the hip fracture risk for the elderly. The amount of rubber in the asphalt mixtures needs to exceed a specific limit to observe rubberized asphalts' preventive effects. Consequently, it is necessary to optimize the mixtures' rubber content to improve its prevention capacity.

In summary, the current thesis presented a method to improve the whole-body models according to the sideways fall requirements and assessed the protective capacity of the rubberized asphalt mixtures against head and hip injuries.

Ett fall är ett allvarligt hälsoproblem för äldre. Bland olika falltyper anses fallet i sidled vara allvarligare vad gäller skadeutfallet. När äldre drabbas av ett oavsiktligt fall i sidled kan de antingen stå emot slagkrafterna med mjukvävnadskraftens dämpningsförmåga och lårbensstyrka eller behöva yttre skydd för att minska skaderisken. I denna avhandling har dessa två aspekter undersökts. Finite element helkroppsmodeller är värdefulla verktyg för att analysera falls biomekanik och lämpligt för att undersöka möjliga förebyggande åtgärder mer bekvämt. Helkroppsmodellerna utvecklades för att undersöka trafikolyckorna; ett fall i sidled har dock en annan kinematik än de andra typerna av olyckor. Följaktligen är det nödvändigt att förbättra helkroppsmodellerna enligt de viktigaste fallparametrarna, vilket leder till allvarliga skadefall, innan man bedömer de yttre skyddsförmågan.

Den aktuella avhandlingen försökte föra fram dessa två kritiska aspekter angående fallinducerade skador. En finite element helkroppsmodell valdes för att studera tre kritiska parametrar i falls biomekanik: kroppshållning, mjukvävnad och femoral styrka. Helkroppsmodellen placerades i olika kroppskonfigurationer som är relevanta för fallet i sidled för att utvärdera kroppshållningen som kunde leda till de högsta inre krafterna på lårbenshuvudet. Därefter undersöktes olika konstitutiva materialmodeller för mjukvävnad och mjukdelstjocklekar för att hitta en materialmodell som exakt kunde återge de experimentella resultaten enligt en objektiv klassificeringsmetod som heter CORrelation and Analysis (CORA). Slutligen utvärderades de separata och kombinerade effekterna av förändringar av geometriska och mekaniska egenskaper på grund av åldrande på lårbensstyrkan för äldre män och kvinnor. I den andra aspekten av avhandlingen undersöktes de stötdämpande gummerade asfaltbeläggningarnas förebyggande kapacitet. Först implementerades olika gummerade asfaltblandningar i rekonstruktionsfallen för en cykel och en fotgängarolycka för att utvärdera riskerna för huvudskador. Senare studerades asfaltblandningarna i ett sidledes fallscenario för att utvärdera risken för höftfraktur hos en äldre man och kvinna.

Den första aspekten av avhandlingen presenterade resultaten och metoderna för att förbättra analysen av sidledsfall, och den andra aspekten av avhandlingen fokuserade på att bedöma de gummerade asfaltblandningarna i skadeförebyggande syfte. Fall i sidled med upprätt bål, och ett något framåtlutat bäcken kan leda till de högsta inre krafterna. En ickelinjär Ogden-materialmodell för muskelvävnad och en Mooney-Rivlin-materialmodell för fettvävnad fick bättre poäng bland olika mjukdelsmaterialmodeller i sidokollisioner mot höftsegmenten. De geometriska och mekaniska egenskaperna förändras på grund av åldrande vilket leder till ett annorlunda beteende för män och kvinnor där kvinnor upplever en högre grad av förlust i styrka på grund av åldrande. Dessutom indikerades att en gummerad asfaltblandning kunde minska risken för huvudskador för fotgängare och cyklister och risken för höftfraktur för äldre. Mängden gummi i asfaltblandningarna behöver överskrida en specifik gräns för att observera gummerad asfalts förebyggande effekt. Följaktligen är det nödvändigt att optimera blandningarnas gummihalt för att förbättra dess förebyggande förmåga.

Sammanfattningsvis presenterade den aktuella avhandlingen en metod för att förbättra helkroppsmodellerna enligt kraven på sidledes fall och bedömde skyddsförmågan hos de gummerade asfaltblandningarna vid huvud- och höftskador.

Older adults are at more significant risk of hip fracture when they fall. In addition to the higher risk of falls for the elderly, fear of falls can reduce this population's outdoor activity. Various preventive solutions were proposed to reduce the risk of hip fractures ranging from wearable hip protectors to indoor flooring systems. A previously developed rubberized asphalt mixture demonstrated the potential to reduce the risk of head injury. In the current study, the capability of the rubberized asphalt sample was evaluated for the risk of hip fracture for an average elderly man and an average elderly woman. A previously developed human body model was positioned in a fall configuration that would give the highest impact forces towards regular asphalt. Three different rubber contents with 14, 28, 33 % wt. were implemented as the ground alongside a reference non-rubberized (0%) asphalt mixture and regular and compliant playground rubber-composite materials. The whole-body model was simulated to fall on the rubberized asphalt mixtures with an initial vertical velocity of 3 m/s with a 10-degree trunk angle and +10 degree anterior pelvis rotation. The impact forces were measured on the femoral head, and a previously developed hip fracture risk function was used to compare the rubberized asphalt mixtures. It was found that the rubberized asphalt mixture with 33 % wt. rubber can reduce the impact forces up to 10 percent for the elderly male and female model compared to regular asphalt. The impact forces were most reduced for the compliant playground material, with a 23% reduction for the female model. The risk of injury for the asphalt mixture with 33% wt. rubber was reduced up to 18 percent for elderly women and 20 for elderly men, compared to regular asphalt. The compliant playground material had the most reduction of hip fracture risk for both sexes, 39 and 43 percent for elderly women and men, respectively.

Whole-body models are historically developed for traffic injury prevention, and they are positioned accordingly in the standing or sitting configuration representing pedestrian or occupant postures. Those configurations are appropriate for vehicle accidents or pedestrian-vehicle accidents; however, they are uncommon body posture during a fall accident to the ground. This study aims to investigate the influence of trunk and pelvis angles on the proximal femur forces during sideways falls. For this purpose, a previously developed whole-body model was positioned into different fall configurations varying the trunk and pelvis angles. The trunk angle was varied in steps of 10 degrees from 10 to 80 degrees, and the pelvis rotation was changed every 5 degrees from -20 degrees (rotation toward posterior) to +20 degrees (rotation toward anterior). The simulations were performed on a medium-size male (177 cm, 76 kg) and a small-size female (156 cm, 55 kg), representative for elderly men and women, respectively. The results demonstrated that the highest proximal femur force measured on the femoral head was reached when either male or female model had a 10-degree trunk angle and +10 degrees anterior pelvis rotation.

Soft tissues in the hip region, which are typically considered the natural shock-absorbers during falls, attenuate the applied forces to the underlying hard tissue. The soft tissue thickness is, therefore, a significant parameter in the force attenuation. Another factor that could affect the assessment of the force attenuation in numerical simulations is the choice of constitutive model and material parameters for the soft tissue. Several constitutive models and parameters for muscle and adipose tissue were suggested in the published literature; however, the biofidelity of the proposed models for the lateral impacts has not been assessed yet. To achieve this purpose, we used a previously developed human body model named THUMS v4.02 and modified the mechanical properties and geometry of the soft tissues in the hip region. The simulations consisted of regional hip models and wholebody models. The biofidelity of the constitutive models of muscle and adipose tissue was determined objectively using the CORrelation and Analysis (CORA) rating. Moreover, the potential force attenuating effect of the adipose tissue thickness was investigated in the regional models. We collected and fitted several available nonlinear material models for muscle and adipose tissue and implemented them. The CORA ratings for several constitutive models for adipose tissue in the regional model were above 0.8. Among the muscle constitutive models, three Ogden models consistently rated above 0.58 for the whole-body model. Moreover, the impact forces in the selected adipose tissue model attenuated 47 N for every 1 mm increase in thickness. Overall, the choice of the nonlinear material model for the adipose and muscle tissue influences the external and internal force, and the difference between the material models is more pronounced when the thickness of the soft tissue increases.

Aging, from 40 to +80 years old, causes geometrical and mechanical properties changes in the proximal femur. The subperiosteal width expands faster in men compared to women during aging, while the cortical thickness varies unequally in each sector and differently between men and women. Another change which occurs during aging is bone mechanical properties such as stiffness and ultimate strains. Numerical analysis allows us to study the potential effects of each of the age-dependent changes on the fracture forces separately and combined. We investigated the effects of the geometrical and bone mechanical properties changes due to aging on the femoral strength during a common falling scenario using a transverse isotropic continuum damage model. First, the femur model was adapted from a previously developed human body model named THUMS v4.02. Then, three sets of models were developed to address each of the changes separately and combined for both sexes. We found that the fracture forces in women are on average 1500 N less than in men of the same age. The age-dependent geometrical changes increased the fracture forces in men (25 N/decade), whereas it reduced the fracture forces by 116 N/decade in women. The mechanical properties changes reduced the fracture forces in men more than in women (354.5 N/ decade vs. 225.4 N/decade). When accounting for both geometrical and mechanical properties changes due to aging, the fracture forces decreased by 10.7% of the baseline in women per decade compared to 7.2% per decade in men.