Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expr...Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expressways,are thought to influence the deposition of the wind-blown sand,but this has yet not to be studied adequately.To address this issue,we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow,the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions.The subgrade model is 3.5 cm high and 80.0 cm wide,with a bank slope ratio of 1:3.The W-beam central guardrails model is 3.7 cm high,which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column.The wind velocity was measured by using pitot-static tubes placed at nine different heights(1,2,3,5,7,10,15,30 and 50 cm)above the floor of the chamber.The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler,which was sectioned into 20 intervals.In addition,we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016,by using a customized 78-cm-high gradient sand sampler for the sand flux structure test.Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade,and the wind velocity on the leeward side weakens significantly.The W-beam central guardrails decrease the leeward wind velocity,whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails.The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails.At 0.0H and 0.5H(where H=3.5 cm,which is the height of the subgrade),the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails,and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface.The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height.The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points,which is consistent with the position of the minimum wind velocity in the wind tunnel test.The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.展开更多
In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, throu...In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, through computer simulation experiment were analyzed, and optimization design, through the real car collision test, make the concrete guardrail after heightening structure satisfies the requirement of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">safety performance of current specification. The results show that the protective performance of the two guardrail schemes meets the requirements of the current guardrail evaluation standards through the computer simulation experiment. Through the optimized design of scheme 1, the actual car crash test proves that the enhanced structure of Minhua TYPE II concrete guardrail can meet the requirements of safety performance evaluation. The research results provide an important basis for the transformation of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">guardrail and the revision of the current design of expressway in China.展开更多
Guardrail,an important highway traffic safety facility,is mainly used to prevent vehicles from accidentally driving off the road and to ensure driving safety.Desert highway guardrails hinder the movement of wind-blown...Guardrail,an important highway traffic safety facility,is mainly used to prevent vehicles from accidentally driving off the road and to ensure driving safety.Desert highway guardrails hinder the movement of wind-blown sand,resulting in the decline of sand transportation by the pavement and the deposition of sand gains on the pavement,and endangering traffic safety.To reveal the influence of guardrails on sand transportation of desert highway pavement,we tested the flow field and sand transport volume distribution around the concrete,W-beam,and cable guardrails under different wind velocities through wind tunnel simulation.Wind velocity attenuation coefficients,sand transportation quantity,and sand transportation efficiency are used to measure sand transportation of highway pavement.The results show that the sand transportation of highway pavement was closely related to the zoning characteristics of flow field and variation of wind velocity around the guardrails.The flow field of the concrete guardrail was divided into deceleration,acceleration,and vortex zones.The interaction between the W-beam guardrail and wind-blown sand was similar to that of lower wind deflector.Behind and under the plates,there were the vortex zone and acceleration zone,respectively.The acceleration zone was conducive to transporting sand on the pavement.The cable guardrail only caused wind velocity variability within the height range of guardrail,and there was no sand deposition on the highway pavement.When the cable,W-beam,and concrete guardrails were used,the total transportation quantities on the highway pavement were 423.53,415.74,and 136.53 g/min,respectively,and sand transportation efficiencies were 99.31%,91.25%,and 12.84%,respectively.From the perspective of effective sand transportation on the pavement,the cable guardrail should be preferred as a desert highway guardrail,followed by the W-beam guardrail,and the concrete guardrail is unsuitable.The study results provide theoretical basis for the optimal design of desert highway guardrails and the prevention of wind-blown sand disasters on the highway pavement.展开更多
Asphalt mow strips are typically used as vegetation barriers around guardrail posts in the design of roadside safety structures. Asphalt mow strips have historically been modeled as a rigid layer in simulations;this a...Asphalt mow strips are typically used as vegetation barriers around guardrail posts in the design of roadside safety structures. Asphalt mow strips have historically been modeled as a rigid layer in simulations;this assumption results in significant ground level restraint on the guardrail post. However, experiments have shown that asphalt rupture should be considered in the analysis of the response of guardrail posts embedded in mow strips. The present study investigates the effect of asphalt material properties and mow strip geometry on guardrail post performance using finite element simulations. Numerical simulations are performed and correlated with results from static experiments and material testing. The test simulations and experimental results are used to evaluate the response of guardrail posts with various mow strip designs to predict the level of restraint from the asphalt layer. The model is then used to investigate the effects of asphalt material properties and mow strip geometry on the overall performance of the system. The results demonstrate that including asphalt rupture in numerical simulations is essential in accurately predicting the behavior of guardrail posts installed in asphalt mow strips. In addition, mow strip geometry along with asphalt material properties significantly affect the guardrail post response.展开更多
To explore the safety of highway traffic operations,the vehicle state and guardrail deformation during highway guardrail collisions are simulated and analyzed.The vehicle-guardrail collision is simulated by finite ele...To explore the safety of highway traffic operations,the vehicle state and guardrail deformation during highway guardrail collisions are simulated and analyzed.The vehicle-guardrail collision is simulated by finite element software such as LS-DYNA and HyperMesh.The vehicle speed settings are 60,80,100 and 120 km/h,and the collision angles are 5°,10°,15°and 20°.The guardrail deformation,vehicle acceleration and energy changes under different collision speeds and angles are studied.The research results show that at the same collision speed,an increase in the collision angle causes more serious damage to the vehicle,a greater transverse displacement of the guardrail,and a greater range of car acceleration fluctuations.When the collision angle is the same,an increase in the collision speed causes greater lateral displacement of the guardrail,a greater vehicle acceleration fluctuation range,and more serious vehicle damage.The results of the study can provide a reference for demonstrating highway guardrail safety.展开更多
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences"Environmental Changes and Green Silk Road Construction in Pan-Third Pole Region"(XDA2003020201)the National Key Research and Development Program of China(2017YFE0109200)the National Natural Science Foundation of China(41571011)
文摘Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expressways,are thought to influence the deposition of the wind-blown sand,but this has yet not to be studied adequately.To address this issue,we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow,the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions.The subgrade model is 3.5 cm high and 80.0 cm wide,with a bank slope ratio of 1:3.The W-beam central guardrails model is 3.7 cm high,which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column.The wind velocity was measured by using pitot-static tubes placed at nine different heights(1,2,3,5,7,10,15,30 and 50 cm)above the floor of the chamber.The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler,which was sectioned into 20 intervals.In addition,we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016,by using a customized 78-cm-high gradient sand sampler for the sand flux structure test.Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade,and the wind velocity on the leeward side weakens significantly.The W-beam central guardrails decrease the leeward wind velocity,whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails.The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails.At 0.0H and 0.5H(where H=3.5 cm,which is the height of the subgrade),the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails,and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface.The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height.The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points,which is consistent with the position of the minimum wind velocity in the wind tunnel test.The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.
文摘In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, through computer simulation experiment were analyzed, and optimization design, through the real car collision test, make the concrete guardrail after heightening structure satisfies the requirement of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">safety performance of current specification. The results show that the protective performance of the two guardrail schemes meets the requirements of the current guardrail evaluation standards through the computer simulation experiment. Through the optimized design of scheme 1, the actual car crash test proves that the enhanced structure of Minhua TYPE II concrete guardrail can meet the requirements of safety performance evaluation. The research results provide an important basis for the transformation of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">guardrail and the revision of the current design of expressway in China.
基金supported by the National Natural Science Foundation of China(52168065)。
文摘Guardrail,an important highway traffic safety facility,is mainly used to prevent vehicles from accidentally driving off the road and to ensure driving safety.Desert highway guardrails hinder the movement of wind-blown sand,resulting in the decline of sand transportation by the pavement and the deposition of sand gains on the pavement,and endangering traffic safety.To reveal the influence of guardrails on sand transportation of desert highway pavement,we tested the flow field and sand transport volume distribution around the concrete,W-beam,and cable guardrails under different wind velocities through wind tunnel simulation.Wind velocity attenuation coefficients,sand transportation quantity,and sand transportation efficiency are used to measure sand transportation of highway pavement.The results show that the sand transportation of highway pavement was closely related to the zoning characteristics of flow field and variation of wind velocity around the guardrails.The flow field of the concrete guardrail was divided into deceleration,acceleration,and vortex zones.The interaction between the W-beam guardrail and wind-blown sand was similar to that of lower wind deflector.Behind and under the plates,there were the vortex zone and acceleration zone,respectively.The acceleration zone was conducive to transporting sand on the pavement.The cable guardrail only caused wind velocity variability within the height range of guardrail,and there was no sand deposition on the highway pavement.When the cable,W-beam,and concrete guardrails were used,the total transportation quantities on the highway pavement were 423.53,415.74,and 136.53 g/min,respectively,and sand transportation efficiencies were 99.31%,91.25%,and 12.84%,respectively.From the perspective of effective sand transportation on the pavement,the cable guardrail should be preferred as a desert highway guardrail,followed by the W-beam guardrail,and the concrete guardrail is unsuitable.The study results provide theoretical basis for the optimal design of desert highway guardrails and the prevention of wind-blown sand disasters on the highway pavement.
文摘Asphalt mow strips are typically used as vegetation barriers around guardrail posts in the design of roadside safety structures. Asphalt mow strips have historically been modeled as a rigid layer in simulations;this assumption results in significant ground level restraint on the guardrail post. However, experiments have shown that asphalt rupture should be considered in the analysis of the response of guardrail posts embedded in mow strips. The present study investigates the effect of asphalt material properties and mow strip geometry on guardrail post performance using finite element simulations. Numerical simulations are performed and correlated with results from static experiments and material testing. The test simulations and experimental results are used to evaluate the response of guardrail posts with various mow strip designs to predict the level of restraint from the asphalt layer. The model is then used to investigate the effects of asphalt material properties and mow strip geometry on the overall performance of the system. The results demonstrate that including asphalt rupture in numerical simulations is essential in accurately predicting the behavior of guardrail posts installed in asphalt mow strips. In addition, mow strip geometry along with asphalt material properties significantly affect the guardrail post response.
基金supported by the Key Lab of Road Structure&Material in Chang’an University,Ministry of Transport(grant number 300102212504)by the National Natural Science Foundation of China(grant number 71771047).
文摘To explore the safety of highway traffic operations,the vehicle state and guardrail deformation during highway guardrail collisions are simulated and analyzed.The vehicle-guardrail collision is simulated by finite element software such as LS-DYNA and HyperMesh.The vehicle speed settings are 60,80,100 and 120 km/h,and the collision angles are 5°,10°,15°and 20°.The guardrail deformation,vehicle acceleration and energy changes under different collision speeds and angles are studied.The research results show that at the same collision speed,an increase in the collision angle causes more serious damage to the vehicle,a greater transverse displacement of the guardrail,and a greater range of car acceleration fluctuations.When the collision angle is the same,an increase in the collision speed causes greater lateral displacement of the guardrail,a greater vehicle acceleration fluctuation range,and more serious vehicle damage.The results of the study can provide a reference for demonstrating highway guardrail safety.
