Seismic Resilience Study of Steel Concentrically Braced Frame Structure with Dual Viscous and Metallic Hysteretic Damper

Steel concentrically braced frames（CBF）are popular seismic resistant structural systems widely used all over the world due to their high elastic stiffness and moderate ductility for many decades. However, conventional CBFs are subject to soft-story damage pattern which may lead to collapse caused by overly large drift concentrated in one story in strong earthquakes; measures to enhance the seismic resilience of CBFs is thus desirable. This study looks into quantifying the seismic resilience of CBFs with and without dual-action damping devices by following the newly released 2018 ed. FEMA P58 procedure. The dual-action damping device includes a viscous damper and metallic hysteretic dampers which are activated at different timing: viscous damper always active and effective in controlling story drift during small and moderate earthquakes, while metallic hysteretic dampers are activated only when the story drift exceeds a pre-specified value during strong earthquakes. A six-story steel CBF and a three-story steel CBF buildings designed by SAC Steel Project research (1999) are adopted as prototype building to demonstrate the effectiveness of dual-action damping device in enhancing the seismic resilience of CBFs. Nonlinear static analyses as well as nonlinear time-history analysis are performed to obtain the Engineering Demand Perimeters (EDP) required for seismic resilience evaluation. Collapse Fragility is developed based on incremental dynamic analysis (IDA) by SPO2IDA Tool. The distribution function of Decision Variables (DV), including Repair cost, Repair time, Casualties etc., is obtained through Monte-Carlo simulation of prior nonlinear time-history analysis EDP by Performance Assessment Calculation Tool (PACT). It is found from this study that the Collapse Risk and the Potential Loss of the prototype structure with dampers have been significantly reduced, suggesting the dual-action damping device provides a beneficial alternative for enhancing the seismic resilience of CBFs

Brine utilisation for cooling and salt production in wind-driven seawater greenhouses:Design and modelling

Brine disposal is a major challenge facing the desalination industry. Discharged brines pollute the oceans and aquifers. Here is it proposed to reduce the volume of brines by means of evaporative coolers in seawater greenhouses, thus enabling the cultivation of high-value crops and production of sea salt. Unlike in typical greenhouses, only natural wind is used for ventilation, without electric fans. We present a model to predict the water evaporation, salt production, internal temperature and humidity according to ambient conditions. Predictions are presented for three case studies: (a) the Horn of Africa (Berbera) where a seawater desalination plant will be coupled to salt production; (b) Iran (Ahwaz) for management of hypersaline water from the Gotvand dam; (c) Gujarat (Ahmedabad) where natural seawater is fed to the cooling process, enhancing salt production in solar salt works. Water evaporation per face area of evaporator pad is predicted in the range 33 to 83 m3/m2·yr, and salt production up to 5.8 tonnes/m2·yr. Temperature is lowest close to the evaporator pad, increasing downwind, such that the cooling effect mostly dissipates within 15 m of the cooling pad. Depending on location, peak temperatures reduce by 8–16 °C at the hottest time of year

A Haptic Surface Robot Interface for Large-Format Touchscreen Displays

This thesis presents the design for a novel haptic interface for large-format touchscreens. Techniques such as electrovibration, ultrasonic vibration, and external braked devices have been developed by other researchers to deliver haptic feedback to touchscreen users. However, these methods do not address the need for spatial constraints that only restrict user motion in the direction of the constraint. This technology gap contributes to the lack of haptic technology available for touchscreen-based upper-limb rehabilitation, despite the prevalent use of haptics in other forms of robotic rehabilitation. The goal of this thesis is to display kinesthetic haptic constraints to the touchscreen user in the form of boundaries and paths, which assist or challenge the user in interacting with the touchscreen. The presented prototype accomplishes this by steering a single wheel in contact with the display while remaining driven by the user. It employs a novel embedded force sensor, which it uses to measure the interaction force between the user and the touchscreen. The haptic response of the device is controlled using this force data to characterize user intent. The prototype can operate in a simulated free mode as well as simulate rigid and compliant obstacles and path constraints. A data architecture has been created to allow the prototype to be used as a peripheral add-on device which reacts to haptic environments created and modified on the touchscreen. The long-term goal of this work is to create a haptic system that enables a touchscreen-based rehabilitation platform for people with upper limb impairments

Dynamic modelling and simulation of a cable-driven parallel robot for rehabilitation applications

The aim of this work, in collaboration with the ROAR Lab of the Columbia University in the city of New York, is to build a simulation model of a new cable-driven parallel robot for rehabilitation applications, being able to compute the effort given by the patient while the system is working on him/her. The model was built on a multi-body dynamic software called Adams, which is able to simulate the behavior of the mechanism. Some theoretical issues about cable-driven parallel robots will be described, in order to familiarize with the application and introduce the state of the art of the topic. General foundations, dealing with kinematics, statics, dynamics will be detailed and a short introduction to control will be given. In the second chapter, a brief overview of the state of the art regarding rehabilitation cable-driven robotics will be outlined, first dealing with general applications possible to be found in literature, and then introducing the Columbia University work about this particular topic, with several examples and cutting edge devices. The third chapter is about the design description of the Stand Trainer, a 8-cable-driven parallel robot used for rehabilitation. Its mechanical system is introduced, while dealing especially with the issue of computing the cable tensions and the way it can be done in terms of sensors positioning. A new way of tension measurement will be explained. It will take the place of the previous one, bringing several advantages to the system. The last chapter deals with the dynamic simulations on Adams. After having introduced all the simplifications regarding three different models, an accurate description of them will be given and their comparison with the real device will be outlined. The post-process activity will be carried out explaining and discussing the final results. Finally, different points for future developments will be discussed, showing the novelty of this approach for rehabilitative treatments and applications

Using an Ultrasonic Transducer to Produce Tactile Rendering on a Touchscreen

International audienceFriction reduction based tactile devices use an ultrasonic vibration to create an overpressure between a user's fingertip and the vibrating surface. This phenomenon is called "the squeeze film effect". This is an emerging technology to produce a haptic feedback on the touchscreen of handheld electronic devices. In this paper, we present the technology and the main technological issues to be improved

Target-specific multiphysics modeling for thermal medicine applications

Dissertation to obtain the degree of Doctor of Philosophy in Biomedical EngineeringThis thesis addresses thermal medicine applications on murine bladder hyperthermia and brain temperature monitoring. The two main objectives are interconnected by the key physics in thermal medicine: heat transfer. The first goal is to develop an analytical solution to characterize the heat transfer in a multi-layer perfused tissue. This analytical solution accounts for important thermoregulation mechanisms and is essential to understand the fundamentals underlying the physical and biological processes associated with heat transfer in living tissues. The second objective is the development of target-specific models that are too complex to be solved by analytical methods. Thus, the software for image segmentation and model simulation is based on numerical methods and is used to optimize non-invasive microwave antennas for specific targets. Two examples are explored using antennas in the passive mode (probe) and active mode (applicator). The passive antenna consists of a microwave radiometric sensor developed for rapid non-invasive feedback of critically important brain temperature. Its design parameters are optimized using a power-based algorithm. To demonstrate performance of the device, we build a realistic model of the human head with separate temperaturecontrolled brain and scalp regions. The sensor is able to track brain temperature with 0.4 °C accuracy in a 4.5 hour long experiment where brain temperature is varied in a 37 °C, 27 °C and 37 °C cycle. In the second study, a microwave applicator with an integrated cooling system is used to develop a new electro-thermo-fluid (multiphysics) model for murine bladder hyperthermia studies. The therapy procedure uses a temperature-based optimization algorithm to maintain the bladder at a desired therapeutic level while sparing remaining tissues from dangerous temperatures. This model shows that temperature dependent biological properties and the effects of anesthesia must be accounted to capture the absolute and transient temperature fields within murine tissues. The good agreement between simulation and experimental results demonstrates that this multiphysics model can be used to predict internal temperatures during murine hyperthermia studies