Multi-axial real-time hybrid simulation framework for testing nonlinear structure systems with multiple boundary interfaces

Hybrid simulation is a widely accepted laboratory testing approach that partitions a proposed structure into numerical and physical substructures, for a space- and cost-effective testing method. Structural elements that are expected to remain in the linear elastic range are usually modeled numerically, while computationally intractable nonlinear elements are tested physically. The loads and conditions at the boundaries between the numerical and physical substructures are imposed by servo-hydraulic actuators, with the responses measured by load cells and displacement transducers. Traditionally, these actuators impose boundary condition displacements at slow speeds, while damping and inertial components for the physical specimen are numerically calculated. This slow application of the boundary conditions neglects the rate-dependent behavior of the physical specimen. Real-time hybrid simulation (RTHS) is an alternative to slow speed hybrid simulation approach, where the responses of the numerical substructure are calculated and imposed on the physical substructure at real-world natural hazard excitation speeds. Damping, inertia, and rate-dependent material effects are incorporated in the physical substructure as a result of real-time testing. For a general substructure, the boundary interface has six degrees-of-freedom (DOF); therefore, an actuation system that can apply multi-axial loads is required. In these experiments, the boundary conditions at the interface between the physical and numerical substructures are imposed by two or more actuators. Significant dynamic coupling can be present between the actuators in such setups. Kinematic transformations are required for the operation of each actuator to achieve desired boundary conditions. Furthermore, each actuator possesses inherent dynamics that need appropriate compensation to ensure an accurate and stable operation. Most existing RTHS applications to date have involved the substructuring of the reference structures into numerical and physical components at a single interface with a one-DOF boundary condition and force imposed and measured. Multi-DOF boundary conditions have been explored in a few applications; however a general six-DOF stable implementation has never been achieved. A major research gap in the RTHS domain is the development of a multi-axial RTHS framework capable of handling six DOF boundary conditions and forces, as well as the presence of multiple physical specimens and numerical-to-physical interfaces. In this dissertation, a multi-axial real-time hybrid simulation (maRTHS) framework is developed for realistic nonlinear dynamic assessment of structures under natural hazard excitation. The framework is comprised of numerical and physical substructures, actuator-dynamics compensation, and kinematic transformations between Cartesian and actuator/transducer coordinates. The numerical substructure is compiled on a real-time embedded system, comprised of a microcontroller setup, with onboard memory and processing, that computes the response of finite element models of the structural system, which are then communicated with the hardware setup via the input-output peripherals. The physical substructure is composed of a multi-actuator boundary condition box, loadcells, displacement transducers, and one or more physical specimens. The proposed compensation is a model-based strategy based on the linearized identified models of individual actuators. The concepts of the model-based compensation approach are first validated in a shake table study, and then applied to single and multi-axis RTHS developments. The capabilities of the proposed maRTHS framework are demonstrated via the multi-axial load and boundary condition boxes (LBCBs) at the University of Illinois Urbana-Champaign, via two illustrative examples. First, the maRTHS algorithm including the decoupled controller, and kinematic transformation processes are validated. In this study, a moment frame structure is partitioned into numerical beam-column finite element model, and a physical column with an LBCB boundary condition. This experiment is comprised of six DOFs and excitation is only applied in the plane of the moment frame. Next, the maRTHS framework is subjected to a more sophisticated testing environment involving a multi-span curved bridge structure. In this second example, two LBCBs are utilized for testing of two physical piers, and excitation is applied bi-directionally. Results from the illustrative examples are verified against numerical simulations. The results demonstrate the accuracy and promising nature of the proposed state-of-the-art framework for maRTHS for nonlinear dynamic testing of structural systems using multiple boundary points

Multi-axial Real-time Hybrid Simulation Framework for Testing Nonlinear Structural Systems with Multiple Boundary Interfaces

Hybrid simulation is a widely accepted laboratory testing approach that partitions a proposed structure into numerical and physical substructures, for a space- and cost-effective testing method. Structural elements that are expected to remain in the linear elastic range are usually modeled numerically, while computationally intractable nonlinear elements are tested physically. The loads and conditions at the boundaries between the numerical and physical substructures are imposed by servo-hydraulic actuators, with the responses measured by loadcells and displacement transducers. Traditionally, these actuators impose boundary condition displacements at slow speeds, while damping and inertial components for the physical specimen are numerically calculated. This slow application of the boundary conditions neglects rate-dependent behavior of the physical specimen. Real-time hybrid simulation (RTHS) is an alternative to slow speed hybrid simulation approach, where the responses of numerical substructure are calculated and imposed on the physical substructure at real world natural hazard excitation speeds. Damping, inertia, and rate-dependent material effects are incorporated in the physical substructure as a result of real-time testing. For a general substructure, the boundary interface has six degrees-of-freedom (DOF); therefore, an actuation system that can apply multi-axial loads is required. In these experiments, the boundary conditions at the interface between the physical and numerical substructures are imposed by two or more actuators. Significant dynamic coupling can be present between the actuators in such setups. Kinematic transformations are required for operation of each actuator to achieve desired boundary conditions. Furthermore, each actuator possesses inherent dynamics that needs appropriate compensation to ensure an accurate and stable operation. Most existing RTHS applications to date have involved the substructuring of the reference structures into numerical and physical components at a single interface with a one-DOF boundary condition and force imposed and measured. Multi-DOF boundary conditions have been explored in a few applications, however a general six-DOF stable implementation has never been achieved. A major research gap in the RTHS domain is the development of a multi-axial RTHS framework capable of handling six DOF boundary conditions and forces, as well as presence of multiple physical specimens and numerical-to-physical interfaces. In this dissertation, a multi-axial real-time hybrid simulation (maRTHS) framework is developed for realistic nonlinear dynamic assessment of structures under natural hazard excitation. The framework is comprised of numerical and physical substructures, actuator-dynamics compensation, and kinematic transformations between Cartesian and actuator/transducer coordinates. The numerical substructure is compiled on a real-time embedded system, comprised of a microcontroller setup, with onboard memory and processing, that computes the response of finite element models of the structural system, which are then communicated with the hardware setup via the input-output peripherals. The physical substructure is composed of a multi-actuator boundary condition box, loadcells, displacement transducers, and one or more physical specimens. The proposed compensation is a model-based strategy based on the linearized identified models of individual actuators. The concepts of the model-based compensation approach are first validated in a shake table study, and then applied to single and multi-axis RTHS developments. The capabilities of the proposed maRTHS framework are demonstrated via the multi-axial load and boundary condition boxes (LBCBs) at the University of Illinois Urbana-Champaign, via two illustrative examples. First, the maRTHS algorithm including the decoupled controller, and kinematic transformation processes are validated. In this study, a moment frame structure is partitioned into numerical beam-column finite element model, and a physical column with an LBCB boundary condition. This experiment is comprised of six DOFs and excitation is only applied in the plane of the moment frame. Next, the maRTHS framework is subjected to a more sophisticated testing environment involving a multi-span curved bridge structure. In this second example, two LBCBs are utilized for testing of two physical piers, and excitation is applied bi-directionally. Results from the illustrative examples are verified against numerical simulations. The results demonstrate the accuracy and promising nature of the proposed state-of-the-art framework for maRTHS for nonlinear dynamic testing of structural systems using multiple boundary points.Ope

Development of a Geometric Extraction Framework as Part of a Pilot Digital Twin Framework for Open-Deck Rail Bridges

69A3551847102Open-deck railway bridges require expensive and customized timber sleepers. When these sleepers are due for replacement, a manual process for geometry measurement is necessary which can be time consuming, inaccurate, and expensive. In addition, significant downtime is required for the safety of the inspectors that measure and assess the conditions of open-deck bridges. In this report, an alternative approach is proposed for geometry extraction of timber sleepers using unmanned aerial vehicle (UAV) inspections and use of artificial intelligence. First, a photogrammetric procedure for development of three-dimensional (3D) bridge models from UAV-based images is provided. Next, a deep learning-based algorithm for segmentation of 3D bridge model into recognizable components is described. Finally, a geometric primitive fitting algorithm is outlined for identifying the geometry of individual components. The aim for this development with 3D scans and automation is to reduce the maintenance and sleeper replacement procedure costs and challenges for open-deck bridges

Development and Validation of a Framework for Smart Wireless Strain and Acceleration Sensing

Civil infrastructure worldwide is subject to factors such as aging and deterioration. Structural health monitoring (SHM) can be used to assess the impact of these processes on structural performance. SHM demands have evolved from routine monitoring to real-time and autonomous assessment. One of the frontiers in achieving effective SHM systems has been the use of wireless smart sensors (WSSs), which are attractive compared to wired sensors, due to their flexibility of use, lower costs, and ease of long-term deployment. Most WSSs use accelerometers to collect global dynamic vibration data. However, obtaining local behaviors in a structure using measurands such as strain may also be desirable. While wireless strain sensors have previously been developed by some researchers, there is still a need for a high sensitivity wireless strain sensor that fully meets the general demands for monitoring large-scale civil infrastructure. In this paper, a framework for synchronized wireless high-fidelity acceleration and strain sensing, which is commonly termed multimetric sensing in the literature, is proposed. The framework is implemented on the Xnode, a next-generation wireless smart sensor platform, and integrates with the strain sensor for strain acquisition. An application of the multimetric sensing framework is illustrated for total displacement estimation. Finally, the potential of the proposed framework integrated with vision-based measurement systems for multi-point displacement estimation with camera-motion compensation is demonstrated. The proposed approach is verified experimentally, showing the potential of the developed framework for various SHM applications

Evaluation of postoperative analgesic effects of gabapentin and ketorolac after Orthognathic surgeries

Background: Pain control after orthognathic surgeries due to severity of pain and limitations of opioids use in these patients are particular importance. The aim of this study was to evaluate the effect of oral gabapentin and intramuscular ketorolac in combination with intravenous acetaminophen for pain control after this surgery. Methods: This study was a randomized clinical trial (RCT) on 75 patients (18-60 years old American Society of Anesthesiologists (ASA) physical status classification system, I, II) that undergo orthognathic surgery in Sina University Hospital, Tehran University of Medical Sciences, Tehran, Iran from June 2013 to August 2014. The patients were randomly divided in 3 groups. All of groups received 1 gr (intravenous acetaminophen) 30 minutes before the end of surgery. The control group (n= 25) received placebo. The second group (n= 25) received 30 mg ketorolac intramuscular after induction of anesthesia and the third group (n= 25) received 600 mg Gabapentin orally 30 minute before the induction of anesthesia. The pain severity score assessed by visual analogue scale (VAS), the level of sedation assessed by Ramsey scale, opioid requirement, nausea and vomiting was recorded in the post-anesthesia care unit (PACU) at 1, 3, 6, 12 and 24 hours after surgery. For rescue pain management intravenous morphine was administered. Results: Seventy-five patients were enrolled in this study. Use of Ketorolac and gabapentin declines the pain intensity, level of agitation and morphine requirement in the recovery room and early hours in the ward (P= 0.011). The 24-hour opioid consumption, nausea and vomiting was significantly higher in control group compared with the both intervention groups (15&plusmn;1.4 vs. 5&plusmn;0.5 mg) (P< 0.05) retrospectively. Mean arterial pressure and heart rate changes was significantly lower in ketorolac and gabapentin groups compare to control group in recovery room (P< 0.05). Conclusion: The result of this study suggest that ketorolac as well as gabapentin can decline the pain intensity and opioid requirement with less nausea and vomiting and good hemodynamic control after orthognathic surgery