In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidim...In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidimensional translational spring model, in which each finger is constructed with prismatic joints. Human hands and the most developed mechanical hands are constructed with revolute joints. In this paper, the effects of fingertip rotation and a revolute joint spring model are investigated. A grasp stiffness matrix is analytically derived by considering not only frictional rolling contact but also frictionless sliding contact. The difl＇erence between the frictional stiffness matrix and the frictionless one is analytically obtained. The effect of local curvature at contact points is analytically derived. The grasp displacement directions affected by the change in curvature and the contact condition are also obtained. The derived stiffness matrix of the revolute joint model is compared with that of the prismatic joint model, and then the stiffness relation is clarified. The gravity effect of the object is also considered. The effectiveness of our method is demonstrated through numerical examples. The stability is evaluated by the eigenvalues of the grasp stiffness matrix, and the grasp displacement direction is obtained by the corresponding eigenvectors. The effect of joint angle is also discussed.展开更多
The beam-to-column semirigid connection in a steel frame structure is represented by a zero-length rotational spring at the end of the beam element. The beam-to-column semirigid connection behavior is represented by i...The beam-to-column semirigid connection in a steel frame structure is represented by a zero-length rotational spring at the end of the beam element. The beam-to-column semirigid connection behavior is represented by its moment-rotation relationship. Several traditional mathematical models have been proposed to fit the moment-rotation curves from the experimental database,but they may be more reliable within certain ranges. In this paper, the intellectualized analytical model is proposed in the semirigid connections for top and seat angles with double web angles using the feed-forward back-propagation artificial neural network （BP-ANN） technique. the intellectualized analytical model from experimental results based on BP-ANN is more reliable and it is a better choice to the moment-rotation curves for beam-to-column semirigid connection. The results are found to provide effectiveness to the experimental response that is satisfactory for use in steel structural engineering design.展开更多
Analytical models used to describe behaviour of steel frame loadbearing structures in fully developed fire usually do not allow for reduced joint stiffness due to increased member temperature. Joints previously design...Analytical models used to describe behaviour of steel frame loadbearing structures in fully developed fire usually do not allow for reduced joint stiffness due to increased member temperature. Joints previously designed as nominally rigid tend to become flexible in fire situation, with degree of flexibility increasing during fire development. Reliable analysis of this phenomenon and its influence on the redistribution of internal forces result in the need for developing appropriate characteristics, describing relationship between bending moment applied to the joint and joint rotation. Characteristics of such type, specified for fire conditions, depend on steel temperature, in the current work, the authors propose a practical approach to develop such characteristics, based on the knowledge of analogous characteristic prepared for persistent design situation. The developed technique does not require to generalize the classical component method to the case of fire, which may be difficult in practical situations. The proposed computational algorithm has been tested on an example of a typical beam-to-column joint.展开更多
文摘In this study, the static stability of the grasp of a single planar object is analyzed using the potential energy method. In previous papers, we considered cases in which individual fingers were replaced by a multidimensional translational spring model, in which each finger is constructed with prismatic joints. Human hands and the most developed mechanical hands are constructed with revolute joints. In this paper, the effects of fingertip rotation and a revolute joint spring model are investigated. A grasp stiffness matrix is analytically derived by considering not only frictional rolling contact but also frictionless sliding contact. The difl＇erence between the frictional stiffness matrix and the frictionless one is analytically obtained. The effect of local curvature at contact points is analytically derived. The grasp displacement directions affected by the change in curvature and the contact condition are also obtained. The derived stiffness matrix of the revolute joint model is compared with that of the prismatic joint model, and then the stiffness relation is clarified. The gravity effect of the object is also considered. The effectiveness of our method is demonstrated through numerical examples. The stability is evaluated by the eigenvalues of the grasp stiffness matrix, and the grasp displacement direction is obtained by the corresponding eigenvectors. The effect of joint angle is also discussed.
文摘The beam-to-column semirigid connection in a steel frame structure is represented by a zero-length rotational spring at the end of the beam element. The beam-to-column semirigid connection behavior is represented by its moment-rotation relationship. Several traditional mathematical models have been proposed to fit the moment-rotation curves from the experimental database,but they may be more reliable within certain ranges. In this paper, the intellectualized analytical model is proposed in the semirigid connections for top and seat angles with double web angles using the feed-forward back-propagation artificial neural network （BP-ANN） technique. the intellectualized analytical model from experimental results based on BP-ANN is more reliable and it is a better choice to the moment-rotation curves for beam-to-column semirigid connection. The results are found to provide effectiveness to the experimental response that is satisfactory for use in steel structural engineering design.
文摘Analytical models used to describe behaviour of steel frame loadbearing structures in fully developed fire usually do not allow for reduced joint stiffness due to increased member temperature. Joints previously designed as nominally rigid tend to become flexible in fire situation, with degree of flexibility increasing during fire development. Reliable analysis of this phenomenon and its influence on the redistribution of internal forces result in the need for developing appropriate characteristics, describing relationship between bending moment applied to the joint and joint rotation. Characteristics of such type, specified for fire conditions, depend on steel temperature, in the current work, the authors propose a practical approach to develop such characteristics, based on the knowledge of analogous characteristic prepared for persistent design situation. The developed technique does not require to generalize the classical component method to the case of fire, which may be difficult in practical situations. The proposed computational algorithm has been tested on an example of a typical beam-to-column joint.
