Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

In a seismic design of embedded foundations, the vertical Subgrade Reaction (SR) acting on a foundation bottom surface and the Rotational Resistance Moment (RRM) generated by the SR are calculated using an SR Modulus (SRM). The SRM and RRM depend on both ground rigidity and Foundation Width (FW). However, the SRM and RRM calculation methods adopted in design codes might not properly consider their FW dependency. In this study, SRM and RRM evaluation methods for embedded foundations subjected to a seismic load were examined by conducting a two-dimensional finite element analysis under the condition where ground rigidity and FW were changed considering the nonlinearity of the ground. The results show that when the seismic load is large and the nonlinearity of the ground appears, the SR distribution is different from the assumption in the design code. The FW dependency of the SRM was lower than the assumption of the design code. Furthermore, methods to calculate the SRM and RRM in accordance with the FW and ground rigidity are proposed.

A Study of Haptic Effects in Endovascular Interventions

During an endovascular intervention, interventionists rely on their sense of touch to perform the procedures correctly. However, there is a paucity of literature regarding the intricacies of the haptic component of the interventions. The objectives of this study were to capture the types and magnitude of haptic effects during real-life interventions from subject matter experts. The study consisted of an online questionnaire and a force measurement experiment to help determine the force types and magnitude. Participants were interventionists with significant procedural experience. The data recorded from the online questionnaire and the experimental study was analysed using descriptive statistics and hypothesis testing techniques. Participants identified four different types of haptic effects: translational resistance, rotational resistance, bump effect and heart beat pressure effect. The characteristics of each effect, such as factor of occurrence and direction, were established and they were compared against each other. Translational resistance was recognised as the strongest, followed by rotational resistance, bump effect and heart beat pressure. In the force measurement experiment, the forces involved in the generation of translational resistance were found to be in the range 0-0.5 N in healthy vessels, 0.5 – 1.5 N in tortuous/narrowed vessels and 1.5 – 2 N in calcified or occluded vessels. Measurements for the bump effect provided less conclusive results due to its subtle nature, although current findings suggest forces between 0.1 – 0.2 N. Overall, the study was successful in expanding current knowledge of haptic effects in endovascular interventions, highlighting the existence of a variety of effects and their characteristics.

Effect of Different Surface Designs on the Rotational Resistance and Stability of Orthodontic Miniscrews: A Three-Dimensional Finite Element Study

High orthodontic forces and various directions of applied forces can be associated with loosening of the screw anchorage in the bone. Screw designs have been modified to increase the stability of the miniscrews. This research evaluates the influence of three-designs on the stability of orthodontic miniscrews. A conventionally cylinder-type miniscrew design (Bio-Action screw, Jin-Biomed co., Bucheon, Korea) was set as a control, and three conditions were studied based on modifications of this control design. Condition-1 has narrowed threads in the upper part of the screw; Condition-2 has a notch at the middle part; and Condition-3 has the combination of Condition-1 and Condition-2. The moment required to unwind the miniscrew to five degrees is tested, and the moment generated at the cortical bone and the trabecular bone were calculated with finite element analysis. Compared to the control, all three conditions showed a higher moment required to unwind the miniscrew and a higher moment generated at the cortical bone. At the trabecular bone, condition-2 and -3 showed higher moment than the control, and condition-1 showed similar moment to the control. Condition-3 required a higher overall moment to unwind the miniscrew. These findings validate the design modifications used to increase the rotational resistance.

An Experimental Study on the Way Bottom Widening of Pier Foundations Affects Seismic Resistance

The resistance of a pier to horizontal loads, like seismic loads, is due to the flexural rigidity of its foundations and the horizontal subgrade reaction. In the event of a massive earthquake, the latter becomes very small because of the softening of the ground, while the structure may experience a large inertial force and lateral spreading pressure. Therefore, structures with high seismic resistance are required in areas with high seismicity. When a wide caisson is used as a pier foundation, a rotational resistance moment caused by the vertical subgrade reaction acting on the foundation bottom can be expected. Although this rotational resistance moment increases if the foundation is widened, in design practice the subgrade reaction coefficient is evaluated as being low under such circumstances. Therefore, even if the foundation is widened, the rotational resistance moment does not increase greatly. Rotational resistance commensurate with the increased construction cost due to foundation widening cannot be expected. In the present study, horizontal loading experiments were performed at one pier with a normal foundation and at one with widened at the bottom foundation, and the way that the widening affected the seismic performance was examined. The results show that compared with the normal foundation, the bottom-widened one experienced far less displacement and offered higher earthquake resistance.

The methodology of testing rotational resistances of the rollers under the operation load

One of the components that affects the energy consumption of belt conveyors is the rotational resistance of the rollers. In real conditions, the roller is subjected to loads not only radial but also axial, resulting from its cooperation with the belt and the way of installation on the conveyor. Knowledge of these resistances is important not only in the design of conveyors, but also in the improvement and search for new structural solutions of the rollers. The article presents an innovative stand dedicated to the study of rotational resistance of the rollers under operating load, its research capabilities and the results of preliminary tests.

A regression model for prediction of idler rotational resistance on belt conveyor

This paper presents a regression model for prediction of idler rotational resistance on belt conveyor. The advantage of the regression model is that it is created according to the real experimental measurement. Besides, the predicted model corresponds with real operational parameters, such as radial force, rotational speed and measurements, conducted via using a laboratory test facility; several criteria have been used to verify the presented regression model. Finally, by analyzing the regression model combined with influence of radical force and rotational resistance on idler rotational resistance, this paper presents an operable control ideal to achieve energy-saving.