In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach emba...In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach embankment, and scale model tests were carried out under different conditions. The results show that when graded gravels were selected as the backfill materials, the effect of setting approach slab to reduce the differential settlement is more prominent. When lime soils were selected as the backfill material, approach slab can moderate the longitudinal settlement slope. When using different backfill materials, the ultimate settlement of the positive trapezoidal backfill geometries is less than that of the inverted trapezoid, and the backfill geometries have little effect on the settlement slope.展开更多
This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model ...This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model containing a flexible bridge and a single levitation unit is presented.Based on the simplified model,the principle underlying the self-excited vibration is explored.After investigations about the energy transmission between the levitation system and bridge,it is concluded that the increment of modal damping can dissipate the accumulated energy by the bridge and the self-excited vibration may be avoided.To enlarge the equivalent modal damping of bridge,the sky-hooked damper is adopted.Furthermore,to avoid the hardware addition of real sky-hooked damper,considering the fact that the electromagnet itself is an excellent actuator that is capable of providing sufficiently fast and large force acting on the bridge to emulate the influence of the real sky-hooked damper,the technique of the virtual sky-hooked damper is proposed.The principle underlying the virtual sky-hooked damper by electromagnet is explored and the vertical velocity of bridge is estimated.Finally,numerical and experimental results illustrating the stability improvement of the vehicle-bridge interaction system are provided.展开更多
Bridge quality assessment is an important part in the final acceptance of new bridge construction,and it is also the main basis for the reinforcement or removal of old bridges.We evaluated the weight of each affecting...Bridge quality assessment is an important part in the final acceptance of new bridge construction,and it is also the main basis for the reinforcement or removal of old bridges.We evaluated the weight of each affecting factor to the upper events using progressive analytical hierarchy process(AHP)with the adoption of 3 scaling,reduced the calculation in analytical process,and precluded the nonuniformity of the scaling system.We obtained a comprehensive evaluation system of bridge quality, and verified its pra...展开更多
The temperature distributions of a prestressed concrete box girder bridge under the effect of cold wave processes were analyzed. The distributions were found different from those under the effect of solar radiation or...The temperature distributions of a prestressed concrete box girder bridge under the effect of cold wave processes were analyzed. The distributions were found different from those under the effect of solar radiation or nighttime radiation cooling and should not be simplified as one dimensional. A temperature predicting model that can accurately predict temperatures over the cross section of the concrete box girder was developed. On the basis of the analytical model, a two-dimensional temperature gradient model was proposed and a parametric study that considered meteorological factors was performed. The results of sensitivity analysis show that the cold wave with shorter duration and more severe temperature drop may cause more unfavorable influences on the concrete box girder bridge. Finally, the unrestrained linear curvatures, self-equilibrating stresses and bending stresses when considering the frame action of the cross section, were derived from the proposed temperature gradient model and current code provisions, respectively. Then, a comparison was made between the value calculated against proposed model and several current specifications. The results show that the cold wave may cause more unfavorable effect on the concrete box girder bridge, especially on the large concrete box girder bridge. Therefore, it is necessary to consider the thermal effect caused by cold wave during the design stage.展开更多
In order to decrease relative settlement, foundation treatment plays an extremely important role in bridgehead transition section, especially, the situation of building the bridge piles firstly, and then processing pi...In order to decrease relative settlement, foundation treatment plays an extremely important role in bridgehead transition section, especially, the situation of building the bridge piles firstly, and then processing piles. On the basis of engineering practice, the authors analyzed the influence of foundation treatment on bridge piles in bridgehead transition section by finite-element method (FEM). This research has positive significance in predicting displacement of bridge pile, directing construction of foundation treatment, and improving quality of engineering and so forth.展开更多
In the centre of the famous Chinese painting, Qingrning Shanghe Tu, an arch-shaped timber bridge, Hongqiao, stands like a rainbow over the river Bianhe. Unfortunately, Hongqiao was damaged during floods from the Yello...In the centre of the famous Chinese painting, Qingrning Shanghe Tu, an arch-shaped timber bridge, Hongqiao, stands like a rainbow over the river Bianhe. Unfortunately, Hongqiao was damaged during floods from the Yellow River, and we can only see her beautiful form in Qingming Shanghe Tu. While, the geometrical dimensions, structural principle, as well as the construction methods of the bridge are still an interesting mystery. In the present paper, the author uncovers the structural principle and the geometric dimensions of the bridge as well as its history background. Furthermore, the author introduces two new structural systems, Lap-Beam and 1.5-Layer space frame, which are inspired by the structural principle of the Hongqiao.展开更多
To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance asses...To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.展开更多
基金Project(51978068) supported by the National Natural Science Foundation of ChinaProject(2018YFE0103800) supported by the National Key R&D Program of China+1 种基金Project(2017M620434) supported by the China Postdoctoral Science FoundationProject(310821173501) support by the Special Fund for Basic Scientific Research of Central College of Chang’an University, China。
文摘In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach embankment, and scale model tests were carried out under different conditions. The results show that when graded gravels were selected as the backfill materials, the effect of setting approach slab to reduce the differential settlement is more prominent. When lime soils were selected as the backfill material, approach slab can moderate the longitudinal settlement slope. When using different backfill materials, the ultimate settlement of the positive trapezoidal backfill geometries is less than that of the inverted trapezoid, and the backfill geometries have little effect on the settlement slope.
基金Projects(11302252,11202230) supported by the National Natural Science Foundation of China
文摘This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model containing a flexible bridge and a single levitation unit is presented.Based on the simplified model,the principle underlying the self-excited vibration is explored.After investigations about the energy transmission between the levitation system and bridge,it is concluded that the increment of modal damping can dissipate the accumulated energy by the bridge and the self-excited vibration may be avoided.To enlarge the equivalent modal damping of bridge,the sky-hooked damper is adopted.Furthermore,to avoid the hardware addition of real sky-hooked damper,considering the fact that the electromagnet itself is an excellent actuator that is capable of providing sufficiently fast and large force acting on the bridge to emulate the influence of the real sky-hooked damper,the technique of the virtual sky-hooked damper is proposed.The principle underlying the virtual sky-hooked damper by electromagnet is explored and the vertical velocity of bridge is estimated.Finally,numerical and experimental results illustrating the stability improvement of the vehicle-bridge interaction system are provided.
基金Funded by the Development Foundation of Key Laboratory in Bridge-structure Engineering Ministry of Communication,P.R.China(No.CQSLBF-Y07-3)
文摘Bridge quality assessment is an important part in the final acceptance of new bridge construction,and it is also the main basis for the reinforcement or removal of old bridges.We evaluated the weight of each affecting factor to the upper events using progressive analytical hierarchy process(AHP)with the adoption of 3 scaling,reduced the calculation in analytical process,and precluded the nonuniformity of the scaling system.We obtained a comprehensive evaluation system of bridge quality, and verified its pra...
基金Project(08Y60) supported by the Traffic Science’s Research Planning of Jiangsu Province,China
文摘The temperature distributions of a prestressed concrete box girder bridge under the effect of cold wave processes were analyzed. The distributions were found different from those under the effect of solar radiation or nighttime radiation cooling and should not be simplified as one dimensional. A temperature predicting model that can accurately predict temperatures over the cross section of the concrete box girder was developed. On the basis of the analytical model, a two-dimensional temperature gradient model was proposed and a parametric study that considered meteorological factors was performed. The results of sensitivity analysis show that the cold wave with shorter duration and more severe temperature drop may cause more unfavorable influences on the concrete box girder bridge. Finally, the unrestrained linear curvatures, self-equilibrating stresses and bending stresses when considering the frame action of the cross section, were derived from the proposed temperature gradient model and current code provisions, respectively. Then, a comparison was made between the value calculated against proposed model and several current specifications. The results show that the cold wave may cause more unfavorable effect on the concrete box girder bridge, especially on the large concrete box girder bridge. Therefore, it is necessary to consider the thermal effect caused by cold wave during the design stage.
文摘In order to decrease relative settlement, foundation treatment plays an extremely important role in bridgehead transition section, especially, the situation of building the bridge piles firstly, and then processing piles. On the basis of engineering practice, the authors analyzed the influence of foundation treatment on bridge piles in bridgehead transition section by finite-element method (FEM). This research has positive significance in predicting displacement of bridge pile, directing construction of foundation treatment, and improving quality of engineering and so forth.
文摘In the centre of the famous Chinese painting, Qingrning Shanghe Tu, an arch-shaped timber bridge, Hongqiao, stands like a rainbow over the river Bianhe. Unfortunately, Hongqiao was damaged during floods from the Yellow River, and we can only see her beautiful form in Qingming Shanghe Tu. While, the geometrical dimensions, structural principle, as well as the construction methods of the bridge are still an interesting mystery. In the present paper, the author uncovers the structural principle and the geometric dimensions of the bridge as well as its history background. Furthermore, the author introduces two new structural systems, Lap-Beam and 1.5-Layer space frame, which are inspired by the structural principle of the Hongqiao.
基金Project(2006.318.223.02-01) supported by the Ministry of Transportation and Communications through the Scientific and Technological Funds of ChinaProject(2007AA11Z104) supported by the High Technology Research and Development of ChinaProject(20090072110045) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.