Considering the interaction between a sleeper,ballast layer,and substructure,a three-dimensional coupled discrete-finite element method for a ballasted railway track is proposed in this study.Ballast granules with irr...Considering the interaction between a sleeper,ballast layer,and substructure,a three-dimensional coupled discrete-finite element method for a ballasted railway track is proposed in this study.Ballast granules with irregular shapes are constructed using a clump model using the discrete element method.Meanwhile,concrete sleepers,embankments,and foundations are modelled using 20-node hexahedron solid elements using the finite element method.To improve computational efficiency,a GPU-based(Graphics Processing Unit)parallel framework is applied in the discrete element simulation.Additionally,an algorithm containing contact search and transfer parameters at the contact interface of discrete particles and finite elements is developed in the GPU parallel environment accordingly.A benchmark case is selected to verify the accuracy of the coupling algorithm.The dynamic response of the ballasted rail track is analysed under different train speeds and loads.Meanwhile,the dynamic stress on the substructure surface obtained by the established DEM-FEM model is compared with the in situ experimental results.Finally,stress and displacement contours in the cross-section of the model are constructed to further visualise the response of the ballasted railway.This proposed coupling model can provide important insights into high-performance coupling algorithms and the dynamic characteristics of full scale ballasted rail tracks.展开更多
Climate change is having an increasing impact on coastal infrastructure,leading to more frequent and intensified wave activity,including higher waves driven by typhoons and abnormal sea conditions.Consequently,issues ...Climate change is having an increasing impact on coastal infrastructure,leading to more frequent and intensified wave activity,including higher waves driven by typhoons and abnormal sea conditions.Consequently,issues related to the stability of existing port structures,such as caissons,have become a significant concern.In particular,gravity-type caisson on the land side of coastal port structures require enhanced stability and safety.Gravity-type caissons,which resist external forces through their own weight,are highly vulnerable to functional failures,such as sliding displacement,triggered by abnormal waves shifting specific caissons.The destruction of caisson and quay walls can lead to substantial recovery costs,necessitating improvements in caisson stability to address the challenges posed by increased wave forces and changes in port logistics due to larger vessels.One approach to enhancing caisson stability is the use of long caissons.Long caisson is commonly used where a breakwater is needed to withstand wave action and distribute forces evenly along a length of breakwater.The construction of caissons faces challenges due to limitations on the size of individual units imposed by construction conditions,launching methods,and marine crane requirements.Therefore,connecting multiple caissons to form long caissons presents a viable alternative.This study suggested two connection methods for long caissons.The first method was a hemisphere caisson,which allows the connection parts to seat against each other under self-weight during construction.The second method was a displacement-allowing connection utilizing rubble(embedded rebar connection within riprap connection).This approach allows some displacement while employing rebar to resist excessive deformation,thereby dispersing the resulting wave forces to adjacent caissons.Performance comparisons between the developed connections and conventional gravity-type caissons were conducted using a finite element analysis model.The results indicate that the proposed connections demonstrate improved resistance to wave forces compared to traditional caissons without such connections.Further studies should include field applications and performance evaluations of various caisson sizes under different environmental and geological conditions.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11872136,11802146,11772085)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT19GJ206,DUT19ZD207).
文摘Considering the interaction between a sleeper,ballast layer,and substructure,a three-dimensional coupled discrete-finite element method for a ballasted railway track is proposed in this study.Ballast granules with irregular shapes are constructed using a clump model using the discrete element method.Meanwhile,concrete sleepers,embankments,and foundations are modelled using 20-node hexahedron solid elements using the finite element method.To improve computational efficiency,a GPU-based(Graphics Processing Unit)parallel framework is applied in the discrete element simulation.Additionally,an algorithm containing contact search and transfer parameters at the contact interface of discrete particles and finite elements is developed in the GPU parallel environment accordingly.A benchmark case is selected to verify the accuracy of the coupling algorithm.The dynamic response of the ballasted rail track is analysed under different train speeds and loads.Meanwhile,the dynamic stress on the substructure surface obtained by the established DEM-FEM model is compared with the in situ experimental results.Finally,stress and displacement contours in the cross-section of the model are constructed to further visualise the response of the ballasted railway.This proposed coupling model can provide important insights into high-performance coupling algorithms and the dynamic characteristics of full scale ballasted rail tracks.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(Nos.RS-2023-00212586 and RS-2024-00348557)the Korea Maritime&Ocean University Research Fund in 2024.
文摘Climate change is having an increasing impact on coastal infrastructure,leading to more frequent and intensified wave activity,including higher waves driven by typhoons and abnormal sea conditions.Consequently,issues related to the stability of existing port structures,such as caissons,have become a significant concern.In particular,gravity-type caisson on the land side of coastal port structures require enhanced stability and safety.Gravity-type caissons,which resist external forces through their own weight,are highly vulnerable to functional failures,such as sliding displacement,triggered by abnormal waves shifting specific caissons.The destruction of caisson and quay walls can lead to substantial recovery costs,necessitating improvements in caisson stability to address the challenges posed by increased wave forces and changes in port logistics due to larger vessels.One approach to enhancing caisson stability is the use of long caissons.Long caisson is commonly used where a breakwater is needed to withstand wave action and distribute forces evenly along a length of breakwater.The construction of caissons faces challenges due to limitations on the size of individual units imposed by construction conditions,launching methods,and marine crane requirements.Therefore,connecting multiple caissons to form long caissons presents a viable alternative.This study suggested two connection methods for long caissons.The first method was a hemisphere caisson,which allows the connection parts to seat against each other under self-weight during construction.The second method was a displacement-allowing connection utilizing rubble(embedded rebar connection within riprap connection).This approach allows some displacement while employing rebar to resist excessive deformation,thereby dispersing the resulting wave forces to adjacent caissons.Performance comparisons between the developed connections and conventional gravity-type caissons were conducted using a finite element analysis model.The results indicate that the proposed connections demonstrate improved resistance to wave forces compared to traditional caissons without such connections.Further studies should include field applications and performance evaluations of various caisson sizes under different environmental and geological conditions.
