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For today's railways, the continuous welded rail, which enhances driving dynamics and comfort for passengers, is often the construction method of choice. However, bridges and viaducts, which can be seen as singularities in the railway substructure, still pose a few unsolved problems; the bridge structure deforms under the impacts of thermal variation, creep, shrinkage, train passage and braking. The track-bridge interaction is an important parameter in railway bridge design. Measurement campaigns and research projects have been performed to investigate the interaction process and learn how to predict longitudinal forces in the rail and the concrete slab track. For the construction of long bridges on high-speed railway lines, new computational tools, monitoring systems and enhanced verification methods for tolerable rail stresses on bridges had to be developed. In order to take the modified stiffness conditions and recent findings on rail resistance into account, the verification schemes and safety concepts based on monitoring data have to be revised and performancebased methods need to be developed. The target of this article is to present monitoring-and reliability-based assessment methods for the concrete structure-rail interaction using monitoring and non-linear analysis techniques.

Percutaneous needle-based intervention is a technique used in minimally invasive surgical procedures such as brachytherapy, thermal ablation, and biopsy. Targeting accuracy in these procedures is a defining factor for success. Active needle steering introduces the potential to increase the targeting accuracy in such procedures to improve the clinical outcome. In this work, a novel 3D steerable active flexible needle with shape memory alloy actuators was developed. Active needle actuation response to a variety of actuation scenarios was analyzed to develop a kinematic model. Shape memory alloy actuators were characterized in terms of their actuation strain, electrical resistance, and required electrical power to design a self-sensing electrical resistance feedback control system for position tracking control of the active needle. The control system performance was initially tested in position tracking control of a single shape memory alloy actuator and then was implemented on multiple interacting shape memory alloy actuators to manipulate the 3D steerable active needle along a reference path. The electrical resistance feedback control of the multiple interacting shape memory alloy actuators enabled the active needle to reach target points in a planar workspace of about 20 mm. Results demonstrated shape memory alloys as promising alternatives for traditional actuators used in surgical instruments with enhanced design, characterization, and control capabilities.

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