Dissipative Knee Bracing for Seismic Strengthening of Steel Frames

This study investigates the effectiveness of dissipative knee bracing as seismic performance improvement strategy for steel frames. A simplified model of a knee element is used for global analyses of frames in order to accurately simulate the bending and shear behaviour observed in laboratory tests reported in literature. The seismic response of a five-storey steel frame incorporating dissipative knee elements is investigated. Nonlinear static analyses are performed to estimate the deformation capacity of the frame and to assess the sequence of yielding in the members. Nonlinear dynamic analyses with different seismic intensity levels are carried out to compare the seismic behaviour of the steel frame in the unprotected and protected configurations. The results of the numerical investigations show that the use of knee elements has the potential to improve the seismic performance of steel frames.

Synthesis of a Knee Joint Endoprosthesis is Based on Pure Rolling

One of the major contributing factors to the life of knee endoprostheses is wear resulting from sliding of the mating surfaces. Although this is not considered the primary cause for failure of the prosthesis, the importance of reducing wear becomes more pronounced with the increase of life expectancy of the patients. Sliding mechanisms are subjected to wear significantly more than rolling mechanisms. It was therefore suggested to develop a prosthetic knee joint in which the mating surfaces will roll one on top of the other. For this purpose an experimental study was carried out aimed at the investigation of the natural knee centrodes. Rolling of the natural centrodes on each other is bound to retain the natural kinematics of the knee elements and that of the soft tissues. Since the natural centrodes were found mechanically inadequate for reproduction, synthetic surfaces were postulated and examined. The various surfaces were subjected to kinematic optimization and the optimal surfaces from structural and kinematic reproduction aspects were selected. Finally, a conceptual configuration of the joint is suggested taking into account the necessary constraints for the performance of the rolling function.