This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges...This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.展开更多
To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing m...To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.展开更多
Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a pie...Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a piezoelectric active member to control the vibration of a four-bay four-longern aluminum truss structure with cantilever boundary. The active member, which utilizes a piezoelectric actuating unit and an integrated load cell, is designed for vibration control of the space truss structures. Active damping control is realized using direct velocity feedback around the active member. The placement of the active member as one of the most important factor of affecting the control system performance, is also investigated by modal dissipation energy ratio as indicator. The active damping effectiveness is evaluated by comparing the closed-loop response with the open loop response.展开更多
The paper presents the principles of a method, which in two simple stages makes possible to carry out the statically calculation of values of forces acting in the fiat static indeterminate trusses. In each stage, it i...The paper presents the principles of a method, which in two simple stages makes possible to carry out the statically calculation of values of forces acting in the fiat static indeterminate trusses. In each stage, it is considered the static determinate truss, scheme of which is obtained after remove the suitable number of members from the basic static indeterminate truss. The both intermediate statically determinate trusses are of the same clear span and they are loaded by forces of half values applied to the corresponding truss nodes. The method applies one of the typical procedures of calculation of the statically determinate trusses and then it is applied in an appropriate way the rule of superposition for obtaining the final values of forces acting in particular members of the basic truss. The values of forces calculated in this way are of a very close approximation to the force values determined in the special and complex ways being considered as the exact calculation methods. The proposed method can be useful mostly but not only for the initial structural design of such systems. The simplicity of the two-stage method justifies an assumption that it can be relatively easy and worthy to adjust to the requirements of the computer aided technology of statically calculation of the complex forms of trusses.展开更多
Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is...Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is grouted to increase the cave-in beating capacity of a hollow tube chord. An experiment of eight specimens of N- joints made of grout-filled square steel tubes is performed. Based on the experimental study, the geometrical parameters of specimens are analyzed, and the effects of the confinement index ε, the spacing between the two web members g and the ratio of side length of the vertical web member to that of the chord β on the behavior of specimens are investigated through simulation analysis by simulation analyses, the mechanical properties and the failure an ANSYS program. Based on the test results and modes of this kind of joints are analyzed and the formulae to predict the ultimate bearing capacities corresponding to different failure modes are developed. The ultimate bearing capacity of compressive N-joints is calculated in accordance with the cave-in failure mode of a chord member; the ultimate bearing capacity of tension N-joints is calculated in accordance with the punchingshear failure mode; the ultimate bearing capacity of a chord member is calculated in accordance with the shear failure mode in normal sections.展开更多
For the truss structure composed of active-elements with piezoelectric patches affixed to its surface,taking the mechani-cal-electric coupling effect under the action of electric loads and mechanical loads into consid...For the truss structure composed of active-elements with piezoelectric patches affixed to its surface,taking the mechani-cal-electric coupling effect under the action of electric loads and mechanical loads into consideration,the finite element model for static force analysis is established by using the theory of mechanics. The failure mechanism of piezoelectric elements is discussed and the failure criteria of piezoelectric elements are proposed. The expression of safety margins for the element of piezoelec...展开更多
Variable geometry truss manipulator （VGTM） has potential to work in the future space applications, of which a dynamic model is important to dynamic analysis and control of the system. In this paper, an approach is p...Variable geometry truss manipulator （VGTM） has potential to work in the future space applications, of which a dynamic model is important to dynamic analysis and control of the system. In this paper, an approach is presented to model the dynamic equations of a VGTM by independent variables, which consists of two double-octahedral truss units and a 3-revolute-prismatic-spherical （3-RPS） parallel manipulator. In this ap- proach, the kinematic recursive relations of two adjacent bodies and geometric constrains are used to deduce the kinematic equations of the VGTM, and Jourdain＇s velocity varia- tion principle is adopted to establish the dynamic equations of the system. The validity of the proposed dynamic model is verified by comparison of numerical simulations with the software ADAMS. Besides, an active controller for trajectory tracking of the system is designed by the computed torque method. The effectiveness of the controller is numer- ically proved.展开更多
Poplar Laminated Veneer Lumber(Poplar LVL)is a new type of engineering materials with high strength,good reliability and small variability.Poplar LVL is manufactured from the fast-growing poplar,which is widely used i...Poplar Laminated Veneer Lumber(Poplar LVL)is a new type of engineering materials with high strength,good reliability and small variability.Poplar LVL is manufactured from the fast-growing poplar,which is widely used in packaging,furniture and others,however,is rarely adopted in construction.In order to explore the feasibility of poplar LVL trusses in construction of roof,four 4.5-m-span Fink-and-Howe trusses were designed and assembled,which were made of poplar LVL with bolted-and tooth-plated connections.Vertical static loading on the upper chord joints of a truss was imposed by self-balancing test device.The mechanical properties of trusses were examined.The ultimate load,deformation character and failure mode of each truss were measured,observed and analyzed.Furthermore,four types of analytical models with different joint connection assumptions were used to estimate the ultimate load and deflection.The results showed that the poplar LVL trusses were basically in elastic stage before the design load was reached,showing good working performance under the action of design load.The bearing capacity of the trusses of bolted connections was greater than that of the tooth-plated connections.As for the same joint connection type,the bearing capacity of Fink trusses exceeded that of Howe trusses.The poplar LVL light trusses of both types of connections showed good structural performance,which could be reasonably used for building roof systems.展开更多
文摘This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.
基金financially supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)。
文摘To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.
文摘Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a piezoelectric active member to control the vibration of a four-bay four-longern aluminum truss structure with cantilever boundary. The active member, which utilizes a piezoelectric actuating unit and an integrated load cell, is designed for vibration control of the space truss structures. Active damping control is realized using direct velocity feedback around the active member. The placement of the active member as one of the most important factor of affecting the control system performance, is also investigated by modal dissipation energy ratio as indicator. The active damping effectiveness is evaluated by comparing the closed-loop response with the open loop response.
文摘The paper presents the principles of a method, which in two simple stages makes possible to carry out the statically calculation of values of forces acting in the fiat static indeterminate trusses. In each stage, it is considered the static determinate truss, scheme of which is obtained after remove the suitable number of members from the basic static indeterminate truss. The both intermediate statically determinate trusses are of the same clear span and they are loaded by forces of half values applied to the corresponding truss nodes. The method applies one of the typical procedures of calculation of the statically determinate trusses and then it is applied in an appropriate way the rule of superposition for obtaining the final values of forces acting in particular members of the basic truss. The values of forces calculated in this way are of a very close approximation to the force values determined in the special and complex ways being considered as the exact calculation methods. The proposed method can be useful mostly but not only for the initial structural design of such systems. The simplicity of the two-stage method justifies an assumption that it can be relatively easy and worthy to adjust to the requirements of the computer aided technology of statically calculation of the complex forms of trusses.
基金The National Natural Science Foundation of China(No50178026)Program for New Century Excellent Talents in University+1 种基金the Key Technologies R & D Program of Heilongjiang Province(NoGC04A609)the Key Technologies R & D Program of Harbin City(No2004AA9CS187)
文摘Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is grouted to increase the cave-in beating capacity of a hollow tube chord. An experiment of eight specimens of N- joints made of grout-filled square steel tubes is performed. Based on the experimental study, the geometrical parameters of specimens are analyzed, and the effects of the confinement index ε, the spacing between the two web members g and the ratio of side length of the vertical web member to that of the chord β on the behavior of specimens are investigated through simulation analysis by simulation analyses, the mechanical properties and the failure an ANSYS program. Based on the test results and modes of this kind of joints are analyzed and the formulae to predict the ultimate bearing capacities corresponding to different failure modes are developed. The ultimate bearing capacity of compressive N-joints is calculated in accordance with the cave-in failure mode of a chord member; the ultimate bearing capacity of tension N-joints is calculated in accordance with the punchingshear failure mode; the ultimate bearing capacity of a chord member is calculated in accordance with the shear failure mode in normal sections.
基金National Defense Basic Foundation (Z192002A001)National Defense Monograph Foundation
文摘For the truss structure composed of active-elements with piezoelectric patches affixed to its surface,taking the mechani-cal-electric coupling effect under the action of electric loads and mechanical loads into consideration,the finite element model for static force analysis is established by using the theory of mechanics. The failure mechanism of piezoelectric elements is discussed and the failure criteria of piezoelectric elements are proposed. The expression of safety margins for the element of piezoelec...
基金Project supported by the National Natural Science Foundation of China(Nos.11132001,11272202,and 11472171)the Key Scientific Project of Shanghai Municipal Education Commission(No.14ZZ021)the Natural Science Foundation of Shanghai(No.14ZR1421000)
文摘Variable geometry truss manipulator （VGTM） has potential to work in the future space applications, of which a dynamic model is important to dynamic analysis and control of the system. In this paper, an approach is presented to model the dynamic equations of a VGTM by independent variables, which consists of two double-octahedral truss units and a 3-revolute-prismatic-spherical （3-RPS） parallel manipulator. In this ap- proach, the kinematic recursive relations of two adjacent bodies and geometric constrains are used to deduce the kinematic equations of the VGTM, and Jourdain＇s velocity varia- tion principle is adopted to establish the dynamic equations of the system. The validity of the proposed dynamic model is verified by comparison of numerical simulations with the software ADAMS. Besides, an active controller for trajectory tracking of the system is designed by the computed torque method. The effectiveness of the controller is numer- ically proved.
基金funded by National Key Research and Development Plan“Green Building and Building Industrialization”Key Special Project in 2017(Grant No.2017YFC0703505)Ministry of Housing and Urban-Rural Development Technology Project in 2015(Grant No.2015-K2-009).
文摘Poplar Laminated Veneer Lumber(Poplar LVL)is a new type of engineering materials with high strength,good reliability and small variability.Poplar LVL is manufactured from the fast-growing poplar,which is widely used in packaging,furniture and others,however,is rarely adopted in construction.In order to explore the feasibility of poplar LVL trusses in construction of roof,four 4.5-m-span Fink-and-Howe trusses were designed and assembled,which were made of poplar LVL with bolted-and tooth-plated connections.Vertical static loading on the upper chord joints of a truss was imposed by self-balancing test device.The mechanical properties of trusses were examined.The ultimate load,deformation character and failure mode of each truss were measured,observed and analyzed.Furthermore,four types of analytical models with different joint connection assumptions were used to estimate the ultimate load and deflection.The results showed that the poplar LVL trusses were basically in elastic stage before the design load was reached,showing good working performance under the action of design load.The bearing capacity of the trusses of bolted connections was greater than that of the tooth-plated connections.As for the same joint connection type,the bearing capacity of Fink trusses exceeded that of Howe trusses.The poplar LVL light trusses of both types of connections showed good structural performance,which could be reasonably used for building roof systems.
