Nine reinforced concrete (RC) beams strengthened by glass fiber reinforced polymer (GFRP) sheets and three control beams are tested. Four parameters are considered in this experimental program included the concrete st...Nine reinforced concrete (RC) beams strengthened by glass fiber reinforced polymer (GFRP) sheets and three control beams are tested. Four parameters are considered in this experimental program included the concrete strength, the reinforcement ratio, the number of GFRP sheets, and the shear span ratio. It is shown that the application of GFRP sheets can increase the ultimate flexural capacity. The effect of the concrete strength, the reinforcement ratio and the number of GFRP sheets on load capacity is obvious. The shear span ratio can affect the failure mode of RC beams strengthened by GFRP sheets. A theoretical model for flexural behavior of the strengthened RC beam is also developed.展开更多
Reconstituted specimens are prepared by means of vacuum preloading. Both static and cyclic triaxial tests are carried out, with the specimens consolidated under different principal stress ratios. A finite element meth...Reconstituted specimens are prepared by means of vacuum preloading. Both static and cyclic triaxial tests are carried out, with the specimens consolidated under different principal stress ratios. A finite element method is put forward for calculating the cumulative deformation of soft clay under cyclic loading.展开更多
In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given a...In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.展开更多
A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linear...A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linearized drag force. An additional drag force convolution term is added to the linearized drag force spectrum, therefore the error is reduced which arises from the truncation of higher order terms in the drag force auto-correlation function. An expression of linearized drag force spectrum is given taking the relative velocity into account. It is found that the additional term is a fold convolution integral. In this paper dynamic responses of risers are investigated, while the influence of floater motion on risers is considered. The results demonstrate that the accuracy of the present method reaches the degree required in time domain analysis.展开更多
The local joint flexibility matrix of multibrace tubular joints (uniplanar and multiplanar joints) is defined. The formulation for computing the elements of local flexibility factor matrix of multibrace tubular joints...The local joint flexibility matrix of multibrace tubular joints (uniplanar and multiplanar joints) is defined. The formulation for computing the elements of local flexibility factor matrix of multibrace tubular joints by semi-analytic method is presented in this paper. The stiffening effect of unloaded braces and cross-flexibility between braces are discussed. Using the local flexibility of unibrace joints instead of that of multibrace joints in conventional structural analysis will lead the result to an unsafe side.展开更多
The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered ...The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered integrally as a close system, and the driving forces actuating the mechanical load can be taken as inner forces in the coupling structure system with controlling. Therefore, one can use the method for dealing with conservative systems to simplify greatly modeling and analyses. The relative equilibrium state of motion of the flexible beam under the condition of zero gravity is studied by using the energy method, in which the characteristics of structure and controlling are considered synthetically. And further, the stability conditions for the relative equilibrium state of the system have been found. If the stability conditions are used as controlling parameters of motion of the system, the kinetic energy of the flexible beam can be converted advantageously into the electromagnetic energy of the motor and controller as well as the vibration of the flexible structure can be reduced rapidly. The results in the research provide a kind of very simple and effective real-time control method reducing the vibration of the flexible beam. The method has been verified in many kinds of experimental systems of flexible beams.展开更多
A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical e...A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical examples are shown to verify the efficiency and validity of the method presented here.展开更多
This paper deals with the initiation and non-coplaner propagation of cracks under biaxial compression. The running process of the propagating cracks is successfully recorded with the method of dynamic photoelasticity....This paper deals with the initiation and non-coplaner propagation of cracks under biaxial compression. The running process of the propagating cracks is successfully recorded with the method of dynamic photoelasticity. A series of important fracture parameters such as cracks propagating velocity, critical opening loading and initial angle of cracks growth under biaxial compression is calculated. Results show that the stress field in front of the non-closed crack tip under biaxial compression is a mixed-mode singular field, the dynamic propagation of the new tensile cracks is just stable and shows distinct stages, but the unstable crack appears under high loads and results in the rupture of the matrix.展开更多
The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface co...The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface conditions for uncracked, craze, open crack, adhesive crack and slid crack parts were discussed and the corresponding incremental iteration algorithm was given. A simplified damage propagation model was presented. The technique has been applied to some specific examples which give the evidence that the method is satisfactory and efficient.展开更多
控制和转发单元分离结构(forwarding and control element separation,ForCES)路由器必须能够支持上百个转发单元(forwarding element,FE),为解决分组在路由器内部的路由问题,在ForCES路由器拓扑发现的基础上,提出基于标签的内部路由机...控制和转发单元分离结构(forwarding and control element separation,ForCES)路由器必须能够支持上百个转发单元(forwarding element,FE),为解决分组在路由器内部的路由问题,在ForCES路由器拓扑发现的基础上,提出基于标签的内部路由机制。引入备份路径减少了路由恢复时间。若n代表FE结点数,m代表含外部接口的FE数,e代表平均边数,则该机制与OSPF(open shortest path first)相比,计算量由O(n3)减小为O(mn2),通信开销由ne的数量级减至n的数量级。实验结果表明:转发表更新算法的计算开销优于OSPF。该机制收敛速度快,通信开销小,路径发生故障时能够快速恢复。展开更多
In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time doma...In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time domain algorithm under the condition of a linearized free surface.展开更多
Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower t...Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower transport rates. The main reason for the under-prediction is that Dp, the effective diameter of particles, is too large as a representative diameter of the bed material for gravel streams with partially movable bed. Performance of these formulas can be significantly improved if D35 is adopted instead of Dp.展开更多
This paper presents a method to analyze the nonlinear aerostatic stability of cable-stayed bridges including all three components of the wind load and the geometric nonlinearity. The analysis was used to investigate t...This paper presents a method to analyze the nonlinear aerostatic stability of cable-stayed bridges including all three components of the wind load and the geometric nonlinearity. The analysis was used to investigate the effects of the wind angle of incidence, the wind load of individual bridge elements, the sagging of cable elements, the changes of tower height and the changes of side span length on the aerostatic stability of cable-stayed bridges. The results show that the wind angle of incidence and the wind loads on the cables have an important effect on the aerostatic stability of cable-stayed bridges.展开更多
This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave p...This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave pressure on the wet surface of the cylinder and second order oscillating wave forces were obtained in this test, but the second-order steady wave force was not able to be measured due to its very small magnitude. The test results also show that third-order wave force may be greater than the second-order force when wave frequencies are high. The experimental results were compared with the corresponding calculation results of Reference [3].展开更多
文摘Nine reinforced concrete (RC) beams strengthened by glass fiber reinforced polymer (GFRP) sheets and three control beams are tested. Four parameters are considered in this experimental program included the concrete strength, the reinforcement ratio, the number of GFRP sheets, and the shear span ratio. It is shown that the application of GFRP sheets can increase the ultimate flexural capacity. The effect of the concrete strength, the reinforcement ratio and the number of GFRP sheets on load capacity is obvious. The shear span ratio can affect the failure mode of RC beams strengthened by GFRP sheets. A theoretical model for flexural behavior of the strengthened RC beam is also developed.
文摘Reconstituted specimens are prepared by means of vacuum preloading. Both static and cyclic triaxial tests are carried out, with the specimens consolidated under different principal stress ratios. A finite element method is put forward for calculating the cumulative deformation of soft clay under cyclic loading.
文摘In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.
文摘A dynamic response analysis in the frequency domain is presented for risers subjected to combined wave and current loading. Considering the effects of current, a modified wave spectrum is adopted to compute the linearized drag force. An additional drag force convolution term is added to the linearized drag force spectrum, therefore the error is reduced which arises from the truncation of higher order terms in the drag force auto-correlation function. An expression of linearized drag force spectrum is given taking the relative velocity into account. It is found that the additional term is a fold convolution integral. In this paper dynamic responses of risers are investigated, while the influence of floater motion on risers is considered. The results demonstrate that the accuracy of the present method reaches the degree required in time domain analysis.
文摘The local joint flexibility matrix of multibrace tubular joints (uniplanar and multiplanar joints) is defined. The formulation for computing the elements of local flexibility factor matrix of multibrace tubular joints by semi-analytic method is presented in this paper. The stiffening effect of unloaded braces and cross-flexibility between braces are discussed. Using the local flexibility of unibrace joints instead of that of multibrace joints in conventional structural analysis will lead the result to an unsafe side.
基金National Natural Science F oundation of China !( No.5 95 75 0 2 6 )
文摘The system of coupling structure with controlling is a kind of dynamic feedback system in which the mechanical load and the actuator/controller interact. The mechanical system and the control system can be considered integrally as a close system, and the driving forces actuating the mechanical load can be taken as inner forces in the coupling structure system with controlling. Therefore, one can use the method for dealing with conservative systems to simplify greatly modeling and analyses. The relative equilibrium state of motion of the flexible beam under the condition of zero gravity is studied by using the energy method, in which the characteristics of structure and controlling are considered synthetically. And further, the stability conditions for the relative equilibrium state of the system have been found. If the stability conditions are used as controlling parameters of motion of the system, the kinetic energy of the flexible beam can be converted advantageously into the electromagnetic energy of the motor and controller as well as the vibration of the flexible structure can be reduced rapidly. The results in the research provide a kind of very simple and effective real-time control method reducing the vibration of the flexible beam. The method has been verified in many kinds of experimental systems of flexible beams.
文摘A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical examples are shown to verify the efficiency and validity of the method presented here.
文摘This paper deals with the initiation and non-coplaner propagation of cracks under biaxial compression. The running process of the propagating cracks is successfully recorded with the method of dynamic photoelasticity. A series of important fracture parameters such as cracks propagating velocity, critical opening loading and initial angle of cracks growth under biaxial compression is calculated. Results show that the stress field in front of the non-closed crack tip under biaxial compression is a mixed-mode singular field, the dynamic propagation of the new tensile cracks is just stable and shows distinct stages, but the unstable crack appears under high loads and results in the rupture of the matrix.
文摘The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface conditions for uncracked, craze, open crack, adhesive crack and slid crack parts were discussed and the corresponding incremental iteration algorithm was given. A simplified damage propagation model was presented. The technique has been applied to some specific examples which give the evidence that the method is satisfactory and efficient.
文摘控制和转发单元分离结构(forwarding and control element separation,ForCES)路由器必须能够支持上百个转发单元(forwarding element,FE),为解决分组在路由器内部的路由问题,在ForCES路由器拓扑发现的基础上,提出基于标签的内部路由机制。引入备份路径减少了路由恢复时间。若n代表FE结点数,m代表含外部接口的FE数,e代表平均边数,则该机制与OSPF(open shortest path first)相比,计算量由O(n3)减小为O(mn2),通信开销由ne的数量级减至n的数量级。实验结果表明:转发表更新算法的计算开销优于OSPF。该机制收敛速度快,通信开销小,路径发生故障时能够快速恢复。
文摘In this paper, based on transient free-surface Green function and panel method, accurate wave exciting forces and moments acting on an arbitrary 3-D body moving at constant forward speed are given by using a time domain algorithm under the condition of a linearized free surface.
文摘Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower transport rates. The main reason for the under-prediction is that Dp, the effective diameter of particles, is too large as a representative diameter of the bed material for gravel streams with partially movable bed. Performance of these formulas can be significantly improved if D35 is adopted instead of Dp.
基金Supported by the National Natural Science Foundation of China(No.59895410 and 59938180)
文摘This paper presents a method to analyze the nonlinear aerostatic stability of cable-stayed bridges including all three components of the wind load and the geometric nonlinearity. The analysis was used to investigate the effects of the wind angle of incidence, the wind load of individual bridge elements, the sagging of cable elements, the changes of tower height and the changes of side span length on the aerostatic stability of cable-stayed bridges. The results show that the wind angle of incidence and the wind loads on the cables have an important effect on the aerostatic stability of cable-stayed bridges.
文摘This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave pressure on the wet surface of the cylinder and second order oscillating wave forces were obtained in this test, but the second-order steady wave force was not able to be measured due to its very small magnitude. The test results also show that third-order wave force may be greater than the second-order force when wave frequencies are high. The experimental results were compared with the corresponding calculation results of Reference [3].