Narrow Results

This study aims to investigate the effects of a cyclist’s riding posture on the kinematic response and head injury severity involved in car–bicycle collision. For this purpose, the finite element (FE) model of a common shared bicycle was developed based on its geometric parameters and a 50% THUMS human FE model was employed to conduct this study. Furthermore, a total of 4 simulation tests were carried out via using four riding postures (pedal $0^{\circ }$, pedal $270^{\circ }$, pedal $180^{\circ }$, pedal $90^{\circ }$) with an impact speed of 40km/h and riding speed of 10km/h. Finally, the head kinematic responses and injury severity were analyzed by employing the output head kinematic and injury parameters. The results revealed that head kinematic responses and kinematic injury criteria varied with the different riding postures. The head responses were similar between the pedal $0^{\circ }$ and pedal $270^{\circ }$ postures, as well as between the pedal $180^{\circ }$ and pedal $90^{\circ }$ postures. The head injury risk was lowest in the pedal $0^{\circ }$ posture. It was notable that the brain tissue injury criterion in the pedal $90^{\circ }$ posture showed significant differences with other riding postures. It was exhibited that a maximum principal strain was 41% to 84% higher and the magnitude of shear stress was 22% to 27% of that in other riding postures. The results of this study may provide insights to enhance safety measures for cyclists.

A rigorous mathematical formulation for the kinematic response of single piles embedded in multilayered soil subjected to vertically incident P-waves is proposed based on the modified Vlasov model. The governing equations and boundary conditions of the soil–pile system are obtained by using Hamilton's principle. The soil–pile interaction and the physical properties of the layered soils are taken into consideration in the proposed model. The accuracy of the proposed method is validated by the comparison of the proposed solution results with some existing solutions. A parametric study is conducted to investigate the effects of the soil inhomogeneity on the kinematic response of single piles. The results reveal that: as for the two-layered case, the thickness of the upper soft layer has a significant influence on the kinematic response of single piles; as for the three-layered case, the soil–pile interaction is very sensitive to the thickness and Young's modulus of the middle layer.

This paper presents a study on three-dimensional seismic soil–structure interaction analysis of a piled-raft (PR) foundation in clay by the substructure approach. Two different pile modeling techniques were adopted and compared with centrifuge shaking table test results reported in the literature. The effect of pile spacing on dynamic impedances, kinematic response parameters, axial pile forces and bending moments of PRs is studied. It is found that the presence of a rigid raft on a pile group results in significant variation in vertical and horizontal dynamic stiffness after a dimensionless frequency ($a_o)$ value of around 0.22. The influence of raft on kinematic response parameters at the top of raft is found to be significantly influenced by pile spacing beyond a dimensionless frequency ($a_o)$ value of 0.4. The axial forces generated at the pile heads of a PR–structure system during seismic shaking are quantified using a new dimensionless factor, and are found to be significantly influenced by the pile spacing. Pile layout in the PR system is found to play an influential role in seismic response as well as pile bending moment for a structure–PR–soil system studied.

A rigorous solution for the kinematic response of the disconnected piles under vertically incident P-waves is presented. A new soil–pile column model is proposed with two fictitious soil columns as the extensions of the shaft along the pile top and tip. The discontinuity of the pile at the two ends is modeled using the Heaviside function to simulate the continuity of the soil–pile column. The total displacement of the soil is divided into the free-field and scattered components. The displacement of the soil–pile system is calculated in terms of the method of separation of variables and the soil–pile interaction. A parametric study indicates that for the disconnected pile, the displacement at the pile top increases significantly with the increase of the cushion thickness, and its effect on the scattered field is weak. The axial force of the disconnected pile decreases gradually with the increase of the cushion thickness. The displacement and axial force of the disconnected pile are significantly influenced by the slenderness ratio of the pile.

Foundations can be subjected to dynamic or seismic loads depending on their applications and the site being constructed in. The researchers concentrated their works on investigating the reasons of the significant damage of piles during seismic excitation. Based on the findings of laboratory experiments and other numerical analyses, such failures were referred to as the kinematic impact of the earthquake on piles since they were associated with discontinuities in the subsoil because of sudden changes in soil stiffness. The current work investigates the seismic response of closed-end (CE) pipe pile using three-dimensional finite element analysis, including the impact of the scaling-up model, acceleration-time history of the ground motion, and ground conditions. The numerical model is developed using a variety of scaling rules and the outputs of the available laboratory tests. The current results showed that the saturated sand models have larger pile deformation factors than dry sand models. Pile frictional resistance was evaluated numerically, and the entire findings were evaluated against the earlier work. Mainly, the frictional resistance around the pile shaft was lower than that at the pile tip, and the frictional resistance factor on the soil surface of dry soil models was larger than that of saturated soil models. Owing to the acceleration amplifications, the pile and soil suffered cycles of compression and tension stresses. A hysteresis loop is broader and flatter on the x-axis as the shear strain increases serve to identify the shear stress–strain plane behavior. The main outputs of the scaled models were normalized to provide a deep insight of model to prototype scaling effects.