Translational Acceleration Research Articles

Second-order inertial forces and torques on a sphere in a viscous steady linear flow

We compute the full set of second-order inertial corrections to the instantaneous force and torque acting on a small spherical rigid particle moving unsteadily in a general steady linear flow. This is achieved by using matched asymptotic expansions and formulating the problem in a coordinate system co-moving with the background flow. Effects of unsteadiness and fluid-velocity gradients are assumed to be small, but to dominate in the far field over those of the velocity difference between the body and fluid, making the results essentially relevant to weakly positively or negatively buoyant particles. The outer solution (which at first order is responsible for the Basset–Boussinesq history force at short time and for shear-induced forces such as the Saffman lift force at long time) is expressed via a flow-dependent tensorial kernel. The second-order inner solution brings a number of different contributions to the force and torque. Some are proportional to the relative translational or angular acceleration between the particle and fluid, while others take the form of products of the rotation/strain rate of the background flow and the relative translational or angular velocity between the particle and fluid. Adding the outer and inner contributions, the known added-mass force or the spin-induced lift force are recovered, and new effects involving the velocity gradients of the background flow are revealed. The resulting force and torque equations provide a rational extension of the classical Basset–Boussinesq–Oseen equation incorporating all first- and second-order fluid inertia effects resulting from both unsteadiness and velocity gradients of the carrying flow.

Sloshing of a cylindrical tank with pipes under extreme translational excitation

We investigate the dynamic characteristics of sloshing load in a large-scale upright cylindrical tank with numerous internal pipes for targeting nuclear reactors in ocean. Experiments involving extreme excitations are conducted by varying the acceleration of harmonic translation. The spatial distribution of pressure on the tank wall and pipes is analyzed, using statistical approaches. Notably, the root mean square of the harmonically oscillating pressure near the bottom of the tank wall exceeds that of the irregular peak pressure near the free surface of the water. The largest magnitude of the harmonic pressure near the tank bottom appears at positions along the excitation axis. However, the peak pressure near the water level can be stronger at positions perpendicular to the excitation axis. While the spectral power of pressure on the tank bottom along the excitation axis is primarily affected by the excitation frequency, the effect of the excitation frequency diminishes near the free surface. Pressure distribution on the internal pipes is also examined. The maximum pressure difference between two diametrically opposite points of a pipe depends on the location of the pipe, which is relatively large for pipes close to the tank wall and aligned with the excitation axis.

An investigation of the effect of brain atrophy on brain injury in multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system (CNS) that affects the brain and spinal cord. It is estimated that the average prevalence of MS is 35.9 cases per 100,000 and a total of 2.8 million people worldwide have MS. Brain atrophy is usually seen in the early stages of MS, and its progress is faster than healthy people. The present study was a numerical study that uses the Fluid–structure interaction (FSI) model to investigate the effect of brain atrophy on brain injury in MS. Firstly, a healthy model was constructed from MRI images and validated by experimental data. Then three models with different degrees of brain atrophy, which showed the rate of brain atrophy in different years in MS patients, were developed to model the brain atrophy in MS. The models were subjected to two different types of impact conditions. Type I, which only produced a translational motion and the HIC value of 744, was applied to each model. Type II produced both translational and rotational motion. In this type of impact, the experimental kinematics, with peaks of 450 g for the translational acceleration and 26.2 krad/s2 for the rotational acceleration, were applied to the nodes that located in the center of gravity of the head models and the results were extracted from each one. According to the results of impact type I, the pressure of the frontal lobe of the brain is 149,647 Pa in the health model and 137,690 Pa in the model with severe atrophy.

Head injury criteria assessment using head kinematics from crash tests and accident reconstructions

Objective The aim of this study was to assess head injury criteria based on their correlation to brain strain in a Finite Element (FE) head model (the KTH Royal Institute of Technology model), by simulation of head kinematics data from frontal and side crash tests with Anthropomorphic Test Devices (ATDs), and from Human Body Model (HBM) accident reconstructions. Methods Six Degrees of Freedom (DoF) head kinematic data was extracted from 221 crash tests, consisting of frontal impacts with the THOR-50M ATD, near-side and far-side impacts with the WorldSID-50M ATD, and from 19 FE HBM accident reconstructions. The head injury criteria HIC15, HIP, BrIC, UBrIC, DAMAGE and CIBIC were calculated, and FE head model simulations were conducted using the six DoF kinematics data. The 100th, 99th, and 95th percentile Maximum Principal Strains (MPS) of the brain were extracted and linear regression models with respect to the injury criteria were created. The injury criteria were then evaluated based on the coefficient of determination, R2, and the Normalized Root Mean Square Error (NRMSE) of each regression model. Results For all the data sets combined and for the WorldSID far-side data, CIBIC had the best goodness of fit, with R2 of 0.76 and 0.85. For frontal impacts with THOR and the combined ATD data set, DAMAGE had highest R2, 0.83 and 0.78, respectively. Injury criteria including translational accelerations were ranked lower, and BrIC were among the three lowest ranked for most data sets evaluated. UBrIC generally ranked after DAMAGE and CIBIC with respect to the goodness of fit but had the lowest NRMSE for all data sets. Conclusions The two mass-spring-damper brain surrogate model criteria, DAMAGE and CIBIC, were best in capturing the head model MPS response for both the THOR and WorldSID data sets. BrIC had lower correlation to the head model MPS and performed marginally better than the linear acceleration only criteria for all the data sets combined. This study supports the suitability of DAMAGE and CIBIC as brain injury criteria to be used with THOR-50M and WorldSID-50M in vehicle crash test conditions, as they outperform BrIC.

Field Measurement on Translational and Torsional Wind-Induced Response of a High-Rise Building during Typhoon Khanun

Full measurements for the wind field atop a 32-storey building (supported by four huge columns) and for the dynamic responses of different floors were conducted on 15 October 2017 to obtain the translational and torsional responses of the high-rise building during the Typhoon Khanun. The time histories of the torsional angular acceleration responses on the 24th and 32nd floors of the high-rise building were obtained using RA013 rotational accelerometer, and those of the translational acceleration responses on the 6th, 12th, 18th, 24th, 30th and 32nd floors along axial direction were recorded by the translational accelerometer. The variation rules of the translational and torsional acceleration responses with floor height and mean wind speed were disclosed, and the response ratios between the torsional and translational acceleration were analyzed when basic time intervals were 10 min. Based on the target probability method, the value range of the acceleration peak factor with different target reliability under Typhoon Khanun was proposed. The results show that the translational and torsional acceleration peak values and root mean squares are the power functions of mean wind speed. The values of acceleration peak factors are recommended to be 3.0 and 5.0 if target reliabilities are determined as 99.38% and 100%, respectively. Research on torsional response measurements can accumulate valuable scientific data and lay solid foundations for the subsequent studies on the torsional wind-resistant design of high-rise buildings.

DESIGNING OF OPTIMAL MOTION CONTROLS FOR FINITE RIGIDITY OBJECTS WITH MINIMUM ENERGY INTENSITY

An algorithm for equivalent replacement of a reversionally constructed optimal control with another control is used, provided that the energies are equal to achieve the goal of motion. It is shown that with an increase in the degree of the polynomial approximating the translational acceleration, not only does the energy decrease for the practical implementation of an equivalent control of the «acceleration-deceleration» type, but also (at a given frequency of free oscillations of a moving elastic object) a decrease in the time to reach absolute quiescence is not excluded (as a sum of translational and relative motion).

Head responses subjected to frontal translational acceleration loads

It is important to understand the relationship between impact accelerations and head responses to improve the protection of head against impact loads. This study aims to parametrically investigate the effects of different frontal translational acceleration loading configurations on head responses using a finite element head model. A series of translational accelerations defined by loading curve shape, impact duration and peak magnitude is applied to a head model to simulate different head impact accidents. The effects of loading configurations on the brain tissue-level responses, including intracranial pressure (ICP), von Mises stress (σv) and maximum principal strain (εp), were studied, and the correlations between head injury criterion (HIC) and tissue-level predictors were analysed. It is found that the head responses increase with the increase of peak magnitudes and the acceleration loading curve shape has significant influences on head responses. The largest head responses were observed for the equivalent square shape (ESS) acceleration case. Both the σv and εp responses increase with the increase of impact durations; however, the impact durations do not affect the ICP responses. Based on the thresholds for tissue-level injury predictors, it is found that both ICP-induced and εp-induced head injuries may occur whereas the σv-induced head injury is less likely to occur under translational acceleration loading conditions. For translational acceleration loading, good correlation can be found between HIC and the εp responses; however, the HIC show a significant difference with the ICP responses for the head injury prediction. To improve the accuracy of head injury prediction with considering different injury mechanisms, ICP responses should be considered when HIC and εp responses are applied in head injury analyses.

Back-Transition Control With Large Deceleration for a Dual Propulsion VTOL UAV Based on Its Maneuverability

This letter analyzes the maneuverability of a fixed-wing hybrid Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV), and proposes a control strategy for back-transitions from fixed-wing mode to rotary-wing mode based on it. Longitudinal aerodynamic forces and moment are modeled to derive a dynamic model of the UAV, and the translational and rotational accelerations that can be generated for the UAV are examined based on the model. To achieve a back-transition with the largest deceleration while maintaining level flight, we search for the best choice of pitch angle and thrust forces for each forward speed by numerical optimization. Flight experiments demonstrate that it is possible to perform a horizontal back-transition while generating a large deceleration with the chosen pitch angles.

Oblique impact responses of Hybrid III and a new headform with more biofidelic coefficient of friction and moments of inertia.

New oblique impact methods for evaluating head injury mitigation effects of helmets are emerging, which mandate measuring both translational and rotational kinematics of the headform. These methods need headforms with biofidelic mass, moments of inertia (MoIs), and coefficient of friction (CoF). To fulfill this need, working group 11 of the European standardization head protection committee (CEN/TC158) has been working on the development of a new headform with realistic MoIs and CoF, based on recent biomechanics research on the human head. In this study, we used a version of this headform (Cellbond) to test a motorcycle helmet under the oblique impact at 8 m/s at five different locations. We also used the Hybrid III headform, which is commonly used in the helmet oblique impact. We tested whether there is a difference between the predictions of the headforms in terms of injury metrics based on head kinematics, including peak translational and rotational acceleration, peak rotational velocity, and BrIC (brain injury criterion). We also used the Imperial College finite element model of the human head to predict the strain and strain rate across the brain and tested whether there is a difference between the headforms in terms of the predicted strain and strain rate. We found that the Cellbond headform produced similar or higher peak translational accelerations depending on the impact location (−3.2% in the front-side impact to 24.3% in the rear impact). The Cellbond headform, however, produced significantly lower peak rotational acceleration (−41.8% in a rear impact to −62.7% in a side impact), peak rotational velocity (−29.5% in a side impact to −47.6% in a rear impact), and BrIC (−29% in a rear-side impact to −45.3% in a rear impact). The 90th percentile values of the maximum brain strain and strain rate were also significantly lower using this headform. Our results suggest that MoIs and CoF have significant effects on headform rotational kinematics, and consequently brain deformation, during the helmeted oblique impact. Future helmet standards and rating methods should use headforms with realistic MoIs and CoF (e.g., the Cellbond headform) to ensure more accurate representation of the head in laboratory impact tests.

An Analytic Solution to the Inverse Dynamics of an Energy Harvesting Tethered Kite

Abstract This paper solves the inverse dynamics of a tethered kite analytically. Specifically, the paper presents a procedure for determining the angle of attack, induced roll angle, and tether tension magnitude needed to achieve a desired combination of translational kite position, velocity, and acceleration. The focus of the paper is on energy harvesting kites. However, the underlying approach is applicable to other kite systems, such as kites for propulsion (e.g., SkySails, Hamburg, Germany). Solving inverse kite dynamics analytically is valuable for trajectory optimization, online state estimation, and the analysis of fundamental limitations on kite maneuvers. Previous work in the literature presents several models of kite dynamics, with varying degrees of fidelity and complexity. However, the nonlinearity of these models often makes them difficult to use for optimization, estimation, and control. The paper shows that, under reasonable assumptions, inverse kite dynamics can be solved in terms of the roots of a fourth-order polynomial function of angle of attack. This function has a geometric interpretation, providing insight into the multiplicity of resulting solutions. Moreover, for special cases including a kite with noncambered wings, these solutions can be computed analytically. A simulation validates the success of the proposed approach in computing inverse kite dynamics for a cross-current trajectory.

Experimental investigation of inertial fibres and disks in a turbulent boundary layer

We study experimentally the behaviour of negatively buoyant disks and fibres in a turbulent boundary layer. The regime is relevant to the transport of natural sediment or plastic particles in water, with density ratio $\rho _p/\rho _f \sim O(1)$ , major axis lengths $D_p^+ \sim 50$ , friction Stokes numbers $\mbox { {St}}^+ \sim O(10)$ and friction Reynolds number $\mbox { {Re}}_\tau = 620$ . The translational and rotational motion, as well as concentration and dispersion, are compared with those of spheres of similar inertia. Disks and fibres both oversample high-speed fluid near the wall, in agreement with particle-resolved numerical simulations. Fibres tend to orient mostly in the streamwise direction while disks maintain their symmetry axis quasi-normal to the wall. This alignment is more stable for disks than for fibres: the latter undergo strong tumbling near the wall in response to the mean shear and turbulent fluid velocity fluctuations, whereas the former wobble about their preferential wall-normal orientation. The translational and rotational accelerations indicate that, despite the nominal relaxation times being similar, the disks are slower than the fibres in responding to wall turbulence. For both, wall contact causes strong and intermittent tumbling. The concentration profiles follow Rouse–Prandtl theory over a limited portion of the boundary layer, deviating near the wall and in the outer region. This is largely due to the non-uniform settling velocity, which decreases steeply approaching the wall for all particle types. This is, in turn, a consequence of the reduced particle diffusivity, which closely matches the profile of the eddy viscosity.

Characterization of lift force and torque in prolate ellipsoid suspensions

The paper derives correlations for lift force and fluid torques acting on stationary prolate ellipsoid suspensions of aspect ratio (AR) 2.5, 5, and 10 subjected to uniform flow. Particle Resolved Simulations (PRS) are conducted on a suspension of infinite extent in two directions for Reynolds number 10 ≤ Re ≤ 200 and solid fractions (φ) between 0.1 ≤ φ ≤ 0.3.The suspension-mean lift-to-drag ratio varies between 7% to 14% at Re=10 which increases to 14% ~ 22% at Re=200. The torque-induced tip rotational acceleration can reach 38% ~ 85% of drag-induced translational acceleration at Re = 200. Single particle lift force and torque correlations of (Fröhlich et al., 2020) are modified and adapted to predict current angular-mean lift and torque data. The resulting lift correlation captures the PRS data within an average deviation below 7%. Torque exhibits a somewhat more complex dependency at AR = 10 than the assumed sinθ ∙ cosθ variation but nevertheless the correlations predict angular-mean values with mean relative deviations of 16.6% at AR = 10.

Wind Turbine Rotor aerodynamic imbalance detection using CNN

This paper investigates the use of convolutional neural networks (CNN) to automatically detect aerodynamic imbalances in horizontal axis wind turbines (WTs). The database is assembled with low-frequency acquisition rates, similar to those obtained using supervisory control and data acquisition (SCADA) systems. The methodology considers imbalances caused by pitch errors only, which might occur due to installation faults or pitch control errors. The measured raw data is initially processed using traditional statistical techniques. Next, the Gramian Angular Field (GAF) method is used to transform the statistical data into images, and then, a CNN is trained to identify aerodynamic rotor imbalance. The proposed methodology is evaluated under numerical simulations of a 1.5 MW wind turbine, and the accuracy and feasibility of the method are demonstrated. The paper demonstrates that it is possible to detect an aerodynamic imbalance in wind turbine rotors from statistics descriptors of nacelle IMU translational accelerations and wind speeds, considering a sampling frequency of above 0.05 Hz, and using an artificial intelligence technique.

The Protective Performance of Modern Motorcycle Helmets Under Oblique Impacts

Motorcyclists are at high risk of head injuries, including skull fractures, focal brain injuries, intracranial bleeding and diffuse brain injuries. New helmet technologies have been developed to mitigate head injuries in motorcycle collisions, but there is limited information on their performance under commonly occurring oblique impacts. We used an oblique impact method to assess the performance of seven modern motorcycle helmets at five impact locations. Four helmets were fitted with rotational management technologies: a low friction layer (MIPS), three-layer liner system (Flex) and dampers-connected liner system (ODS). Helmets were dropped onto a 45° anvil at 8 m/s at five locations. We determined peak translational and rotational accelerations (PTA and PRA), peak rotational velocity (PRV) and brain injury criteria (BrIC). In addition, we used a human head finite element model to predict strain distribution across the brain and in corpus callosum and sulci. We found that the impact location affected the injury metrics and brain strain, but this effect was not consistent. The rear impact produced lowest PTAs but highest PRAs. This impact produced highest strain in corpus callosum. The front impact produced the highest PRV and BrIC. The side impact produced the lowest PRV, BrIC and strain across the brain, sulci and corpus callosum. Among helmet technologies, MIPS reduced all injury metrics and brain strain compared with conventional helmets. Flex however was effective in reducing PRA only and ODS was not effective in reducing any injury metrics in comparison with conventional helmets. This study shows the importance of using different impact locations and injury metrics when assessing head protection effects of helmets. It also provides new data on the performance of modern motorcycle helmets. These results can help with improving helmet design and standard and rating test methods.

Auto-Tuning parameters of motion cueing algorithms for high performance driving simulator based on Kuka Robocoaster.

Driving simulators have been utilized to test and evaluate products and services for a long time. Their complexity and price range from extremely simple low-cost simulators with a fixed base to very complex high-end and pricey six-degree-of-freedom simulators with the XY table. The recent novel technique that uses an industrial robot - KUKA Robocoaster - as an interactive motion simulator platform, allowing for a highly flexible workspace as well as significantly lower prices due to mass production of the fundamental mechanics. In the constrained workspace of driving simulators, motion cueing algorithms (MCAs) are commonly employed to merge the tilt gravity and translational acceleration components for simulating the linear acceleration in the real vehicle. However, there is a few MCAs developed for the motion platform, almost MCAs were implemented for the standard six-degree-of-freedom simulators in the Cartesian coordinate. The classical MCA in the cylindrical coordinate (ClCy) MCA was first developed for the novel motion platform to take advantage of enormous rotational motion to simulate lateral acceleration while compensating for the bothersome longitudinal acceleration (due to centrifugal acceleration appearing in the rotational motion) with a proper pitch tilted angle. The process of tuning MCAs for the novel motion platform is time-consuming due to both trial and error method and the disturbing motion cues generated by rotational motion, thus it needs the involvement of experts. Although there are several auto-tuning approaches for classical, optimal, and model-predictive control MCA based on fuzzy control theory or genetic optimization method, the methods were purely applied for Cartersian coordinate without taking the bothersome longitudinal acceleration into account. Therefore, this paper firstly presents the process of integrating MCAs in the novel motion platform utilizing rotational motion for simulating lateral acceleration. For the case, besides the ClCy algorithm, the classical algorithm developed for the standart six-degree-of-freedom simulators was a sample implementation due to its popular and familiar characteristics. Secondly, the proposal of the use of the mean-variance mapping optimization (MVMO) for auto-tuning parameters of the two algorithms for reducing both rotational false cues in roll and pitch channel, and longitudinal acceleration as well as washout effect. The simulation results prove that 1) The classical and other MCAs can be applied in the novel motion platform with the proposed motion conversion; 2) both algorithms with auto-tuned parameters have high performance in exploiting effectively the workspace of the motion platform, producing no false cues of angular velocity, conpensating the disturbed longitudinal acceleration, and pulling the motion platform to the initial position after the simulation task; 3) The auto-tuning method is so transparent that can manipulates the specific simulated quantities according to the tuning goals.

LiDAR-Stabilised GNSS-IMU Platform Pose Tracking.

The requirement to estimate the six degree-of-freedom pose of a moving platform frequently arises in automation applications. It is common to estimate platform pose by the fusion of global navigation satellite systems (GNSS) measurements and translational acceleration and rotational rate measurements from an inertial measurement unit (IMU). This paper considers a specific situation where two GNSS receivers and one IMU are used and gives the full formulation of a Kalman filter-based estimator to do this. A limitation in using this sensor set is the difficulty of obtaining accurate estimates of the degree of freedom corresponding to rotation about the line passing through the two GNSS receiver antenna centres. The GNSS-aided IMU formulation is extended to incorporate LiDAR measurements in both known and unknown environments to stabilise this degree of freedom. The performance of the pose estimator is established by comparing expected LiDAR range measurements with actual range measurements. Distributions of the terrain point-to-model error are shown to improve from mean error to when the GNSS-aided IMU estimator is augmented with LiDAR measurements. This precision is marginally degraded to when the pose estimator is operated in an a prior unknown environment.

Cavitation nucleation and its ductile-to-brittle shape transition in soft gels under translational mechanical impact

Cavitation bubbles in the human body, when subjected to impact, are being increasingly considered as a possible brain injury mechanism. However, the onset of cavitation and its complex dynamics in biological materials remain unclear. Our experimental results using soft gels as a tissue simulant show that the critical acceleration (acr) at cavitation nucleation monotonically increases with increasing stiffness of gelatin A/B, while acr for agarose and agar initially increases but is followed by a plateau or even decrease after stiffness reach to ∼100 kPa. Our image analyses of cavitation bubbles and theoretical work reveal that the observed trends in acr are directly linked to how bubbles grow in each gel. Gelatin A/B, regardless of their stiffness, form a localized damaged zone (tens of nanometers) at the gel-bubble interface during bubble growth. In contrary, the damaged zone in agar/agarose becomes significantly larger (> 100 times) with increasing shear modulus, which triggers the transition from formation of a small, damaged zone to activation of crack propagation. Statement of SignificanceWe have studied cavitation nucleation and bubble growth in four different types of soft gels (i.e., tissue simulants) under translational impact. The critical linear acceleration for cavitation nucleation has been measured in the simulants by utilizing a recently developed method that mimics acceleration profiles of typical head blunt events. Each gel type exhibits significantly different trends in the critical acceleration and bubble shape (e.g., A gel-specific sphere-to-saucer transition) with increasing gel stiffness. Our theoretical framework, based on the concepts of a damaged zone and crack propagation in each gel, explains underlying mechanisms of the experimental observations. Our in-depth studies shed light on potential links between traumatic brain injuries and cavitation bubbles induced by translational acceleration, the overlooked mechanism in the literature.

A study of the efficiency of the magnetic compass correction system

In sailing conditions under the rolling, dynamic compass errors may appear due to the influence of the redistributed magnetic masses of the ship, as well as of centripetal and tangential accelerations. The influence of these errors can be compensated by introducing a correction system into the measuring circuit of the compass, which uses one gyroscopic angular rate sensor. The correction method is based on the use of a gyroscopic angular rate sensor with a vertical axis of sensitivity in the circuit. The generated signal is the difference between the output reading of the magnetic compass and the integrated signal of the angular rate sensor, which is insensitive to the action of translational acceleration and redistributed magnetic masses during the ship’s heel. The resulting difference will contain the compass error from the rolling effect, further compensated for in the compass output signal. The choice of the parameters of the dynamic links of the circuit for the implementation of the correction system and the study of its operation was carried out by simulation method using the proposed analytical expression for the error of the magnetic compass from the rolling effect. Comparison of the simulation results with the results of experimental studies of the compass was carried out using a specialized stand that simulates the yaw of a ship and allows one to change the value of the vector of the Earth’s magnetic field, when exposed to the magnetic system of the compass. Experimental studies of the compass showed that the pitching error correction coefficient is in the range 0.16-0.48 (average value is 0.35), when the object’s angular oscillation periods change from 6 to 28 s, which characterizes the degree of pitching suppression, and when modeling, the average value of the coefficient is 0.21. The underestimation of the correction factor in modeling is due to the lack of taking into account the dynamic properties of the compass rose and depends on the ratio of the periods of natural oscillations of the compass and the periods of disturbing influences. The results confirmed the high efficiency of the considered compass correction system and the required quality of the developed specialized stand for evaluating its work. The results of the study can be used in the development of modern magnetic compasses to ensure high accuracy of directional guidance through the use of the proposed correction system.

Auto-Tuning Parameters of the Offline Optimal Motion Cueing Algorithm with Mean-Variance Mapping Optimization

A motion cueing algorithm (MCA) not only maintains the simulator within its physical limits but also generates such movements of the driving simulator that the necessary motion cues of drivers on the realistic vehicle are equivalently reproduced. The offline optimal MCA focuses on finding the best combination of the translational acceleration and tilt angles of the motion platform to maintain drivers’ motion perception. However, the best combination depends on the MCA’s parameters, tuned mainly by trial and error with experts in the loop. Moreover, for different amplitude input signals, the parameters are accordingly modified. This manual tuning procedure is so time-consuming that the generic optimization, named Mean-Variance mapping optimization, was proposed to search the suitable parameters for the optimal algorithm. This tuning method uses the specific cost function of constraint conditions such as workspace limits, avoiding false cues, and improving motion fidelity to achieve the best parameters for optimal MCA with the particular input signals.

Full-Scale Measurements of Translational and Torsional Dynamics Characteristics of a High-Rise Building during Typhoon Sarika.

The field measurement of wind-induced response is of great significance to the wind resistance design of high-rise buildings, in particular torsional responses measured from high-rise buildings under typhoons. The measured high-rise building, with a height of 108 m, has 32 stories and is supported by giant trusses with four massive columns. Acceleration responses along translational and torsional directions were monitored synchronously and continuously during the passage of Typhoon Sarika on 18 October 2016. The wind speed and wind direction at the height of 115 m, the translational accelerations on a total of six floors and the angular accelerations on a total of four floors were recorded. The time and frequency domain characteristics of translational acceleration and torsional angular accelerations were analyzed. The amplitude-dependent translational and torsional modal frequencies of the measured building were identified by NExT-ERA, SSI, and RDT methods. The full-scale study is expected to provide useful information on the wind-resistant design of high-rise buildings in typhoon-prone regions.