Optimum bitumen content determination is one of the major aims for foamed bitumen mix design. However, mix design procedures for foamed bitumen mixes are still under development. In this paper a method to determine th...Optimum bitumen content determination is one of the major aims for foamed bitumen mix design. However, mix design procedures for foamed bitumen mixes are still under development. In this paper a method to determine the optimum bitumen content for given foamed bitumen mix based on primary aggregate structure porosity and indirect tensile strength criterion is proposed. Using packing theory concepts, the aggregate gradation is divided into three aggregate structures which are oversize, primary and secondary struc- tures. Porosity for the primary aggregate structure is determined for given bitumen contents. A maximum value for porosity of 50% for the primary aggregate structure is used to choose initial bitumen content. Furthermore, a minimum indirect tensile strength criteria is suggested to refine this bitumen content. This method enables a bitumen content value to be chosen prior to the start of experimental work, as porosity is expressed in terms of physical parameters such as aggregate and binder specific gravity, and aggregate gradation which are known before the mix design process. The bitumen content is then later refined when the indirect tensile strength is determined in the laboratory. This method would reduce resources such as time and materials that may be required during the mix design procedure.展开更多
The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon ...The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.展开更多
基金The financial assistance from the Swedish International Development AgencyDivision of Highway and Railway Engineering,KTH,Stockholm
文摘Optimum bitumen content determination is one of the major aims for foamed bitumen mix design. However, mix design procedures for foamed bitumen mixes are still under development. In this paper a method to determine the optimum bitumen content for given foamed bitumen mix based on primary aggregate structure porosity and indirect tensile strength criterion is proposed. Using packing theory concepts, the aggregate gradation is divided into three aggregate structures which are oversize, primary and secondary struc- tures. Porosity for the primary aggregate structure is determined for given bitumen contents. A maximum value for porosity of 50% for the primary aggregate structure is used to choose initial bitumen content. Furthermore, a minimum indirect tensile strength criteria is suggested to refine this bitumen content. This method enables a bitumen content value to be chosen prior to the start of experimental work, as porosity is expressed in terms of physical parameters such as aggregate and binder specific gravity, and aggregate gradation which are known before the mix design process. The bitumen content is then later refined when the indirect tensile strength is determined in the laboratory. This method would reduce resources such as time and materials that may be required during the mix design procedure.
基金The work described in this paper is supported by the National Natural Science Foundation of China(Grant Nos.52278455 and 52311530685)the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(21SG24)+1 种基金the International Cooperation Project of Science and Technology Commission of Shanghai Municipality(No.22210710700)the Fundamental Research Funds for the Central Universities.
文摘The presence of water films on a runway surface presents a risk to the landing of aircraft.The tire of the aircraft is separated from the runway due to a hydrodynamic force exerted through the water film,a phenomenon called hydroplaning.Although a lot of numerical investigations into hydroplaning have been conducted,only a few have considered the impact of the runway permeability.Hence,computational problems,such as excessive distortion and computing efficiency decay,may arise with such numerical models when dealing with the thin water film.This paper presents a numerical model comprising of the tire,water film,and the interaction with the runway,applying a mathematical model using the smoothed particle hydrodynamics and finite element(SPH-FE)algorithm.The material properties and geometric features of the tire model were included in the model framework and water film thicknesses from 0.75 mm to 7.5 mm were used in the numerical simulation.Furthermore,this work investigated the impacts of both surface texture and the runway permeability.The interaction between tire rubber and the rough runway was analyzed in terms of frictional force between the two bodies.The SPH-FE model was validated with an empirical equation proposed by the National Aeronautics and Space Administration(NASA).Then the computational efficiency of the model was compared with the traditional coupled Eulerian-Lagrangian(CEL)algorithm.Based on the SPH-FE model,four types of the runway(Flat,SMA-13,AC-13,and OGFC-13)were discussed.The simulation of the asphalt runway shows that the SMA-13,AC-13,and OGFC-13 do not present a hydroplaning risk when the runway permeability coefficient exceeds 6%.
