The damage properties of two types of rocks under dynamic loading are studied. The shock induced experiments are done using planar impact technique on the one? stage light gas gun, and the ultrasonic tests on the da...The damage properties of two types of rocks under dynamic loading are studied. The shock induced experiments are done using planar impact technique on the one? stage light gas gun, and the ultrasonic tests on the damaged rocks have been made by use of the ultrasonic pulse? transmission method. The shock induced damage of rock is related to the shock speed and the attenuation coefficient of sonic wave, and the latter reflects the damage degree in rock fairly well. The attenuation coefficient α can be used as main damage parameter for constructing damage model of rock under dynamic loading.展开更多
The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite...The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric travel, affected by the restricts from the static effects of the eccentric moving trucks, are significantly smaller than the vehicle-free side, the increase in the road roughness is the most sensitive one among the above influential factors. The results could provide references for the design, static and dynamic response analysis of the similar extra-wide suspension bridges.展开更多
The single-layer latticed cylindrical shell is one of the most widely adopted space-fl'amed structures.In this paper,free vibration properties and dynamic response to horizontal and vertical seismic waves of singl...The single-layer latticed cylindrical shell is one of the most widely adopted space-fl'amed structures.In this paper,free vibration properties and dynamic response to horizontal and vertical seismic waves of single-layer latticed cylindrical shells are analyzed by the finite element method using ANSYS software.In the numerical study,where hundreds of cases were analyzed,the parameters considered included rise-span ratio,length-span ratio,surface load and member section size.Moreover,to better define the actual behavior of single-layer latticed shells,the study is focused on the dynamic stress response to both axial forces and bending moments.Based on the numerical results,the effects of the parameters considered on the stresses are discussed and a modified seismic force coefficient method is suggested.In addition,some advice based on these research results is presented to help in the future design of such structures.展开更多
In order to study the dynamic response and calculate the axial dynamic coefficient of the monolayer cylindrical explosion vessel,the wall of vessel is simplified as a multi-degree-of-freedom(MDoF) undamped elastic fou...In order to study the dynamic response and calculate the axial dynamic coefficient of the monolayer cylindrical explosion vessel,the wall of vessel is simplified as a multi-degree-of-freedom(MDoF) undamped elastic foundation beam.Decoupling the coupled motion equation and using Duhamel's integrals,the solutions in generalized coordinates of the equations under exponentially decaying loads,square wave loads and triangular wave loads are calculated.These solutions are consistent in form with the solutions of single-degree-of-freedom(SDoF) undamped forced vibration simplified model.Based on the model,equivalent MDoF design method(also called MDoF dynamic coefficient method) of cylindrical explosion vessel is proposed.The traditional method can only predict the dynamic coefficient of torus portion around the explosion center,but this method can predict that of the vessel wall at any axial n dividing point position.It is verified that the prediction accuracy of this model is greatly improved compared with the SDoF model by comparing the results of this model with SDoF model and numerical simulation in different working conditions.However,the prediction accuracy decreases as the scaled distance decreases and approaches the end of the vessel,which is related to the accuracy of the empirical formula of the implosion load,the simplification of the explosion load direction,the boundary conditions,and the loading time difference.展开更多
文摘The damage properties of two types of rocks under dynamic loading are studied. The shock induced experiments are done using planar impact technique on the one? stage light gas gun, and the ultrasonic tests on the damaged rocks have been made by use of the ultrasonic pulse? transmission method. The shock induced damage of rock is related to the shock speed and the attenuation coefficient of sonic wave, and the latter reflects the damage degree in rock fairly well. The attenuation coefficient α can be used as main damage parameter for constructing damage model of rock under dynamic loading.
基金Project(51278104)supported by the National Natural Science Foundation of ChinaProject(2011Y03)supported by Jiangsu Province Transportation Scientific Research Programs,China+1 种基金Project(20133204120015)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(12KJB560003)supported by Jiangsu Province Universities Natural Science Foundation,China
文摘The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric travel, affected by the restricts from the static effects of the eccentric moving trucks, are significantly smaller than the vehicle-free side, the increase in the road roughness is the most sensitive one among the above influential factors. The results could provide references for the design, static and dynamic response analysis of the similar extra-wide suspension bridges.
基金National Natural Science Foundation of China,Grant No.59895410
文摘The single-layer latticed cylindrical shell is one of the most widely adopted space-fl'amed structures.In this paper,free vibration properties and dynamic response to horizontal and vertical seismic waves of single-layer latticed cylindrical shells are analyzed by the finite element method using ANSYS software.In the numerical study,where hundreds of cases were analyzed,the parameters considered included rise-span ratio,length-span ratio,surface load and member section size.Moreover,to better define the actual behavior of single-layer latticed shells,the study is focused on the dynamic stress response to both axial forces and bending moments.Based on the numerical results,the effects of the parameters considered on the stresses are discussed and a modified seismic force coefficient method is suggested.In addition,some advice based on these research results is presented to help in the future design of such structures.
基金supported by grants from the Department of Infrastructure Barracks and National Science-Technology Support Plan(Grants No.BY209J033 and 2012BAK05B01)。
文摘In order to study the dynamic response and calculate the axial dynamic coefficient of the monolayer cylindrical explosion vessel,the wall of vessel is simplified as a multi-degree-of-freedom(MDoF) undamped elastic foundation beam.Decoupling the coupled motion equation and using Duhamel's integrals,the solutions in generalized coordinates of the equations under exponentially decaying loads,square wave loads and triangular wave loads are calculated.These solutions are consistent in form with the solutions of single-degree-of-freedom(SDoF) undamped forced vibration simplified model.Based on the model,equivalent MDoF design method(also called MDoF dynamic coefficient method) of cylindrical explosion vessel is proposed.The traditional method can only predict the dynamic coefficient of torus portion around the explosion center,but this method can predict that of the vessel wall at any axial n dividing point position.It is verified that the prediction accuracy of this model is greatly improved compared with the SDoF model by comparing the results of this model with SDoF model and numerical simulation in different working conditions.However,the prediction accuracy decreases as the scaled distance decreases and approaches the end of the vessel,which is related to the accuracy of the empirical formula of the implosion load,the simplification of the explosion load direction,the boundary conditions,and the loading time difference.
