On methods for extending a single footfall trace into a continuous force curve for floor vibration serviceability analysis

Jun Chen,Yixin Peng,Ting Ye 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.2

An experimentally measured single footfall trace (SFT) from a walking subject needs to be extended into a continuous force curve, which can then be used as load for floor vibration serviceability assessment, or on which further analysis like discrete Fourier transform can be conducted. This paper investigates the accuracy, applicability and parametrical sensitivity of four extension methods, Methods I to IV, which extends the SFT into a continuous time history by the walking step rate, stride time, double support proportion and the double support time, respectively. Performance of the four methods was assessed by comparing their results with the experimentally obtained reference footfall traces in the time and frequency domain, and by comparing the vibrational response of a concrete slab subjected to the extended traces to that of reference traces. The effect of the extension parameter on each method was also explored through parametrical analysis. This study finds that, in general, Method I and II perform better than Method III and IV, and all of the four methods are sensitive to their extension parameter. When reliable information of walking rate or gait period is available in the test, Methods I or II is a better choice. Otherwise, Method III, with the suggested extension parameter of double support time proportion, is recommended.

Sampling-based Event-triggered and Self-triggered Control for Linear Systems

Jun Chen,Yuan Fan,Chengxiao Zhang,Cheng Song 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.3

This work considers the event-triggered and self-triggered control for linear systems with periodic sampling schemes. An event-triggered control using sampled states is proposed. The asymptotic stability of the closedloop system is guaranteed by a condition in terms of a linear matrix inequality. Moreover, a self-triggered control with sampling is presented and the next control task release time is predicted based on the current sampled data. It is noted that by introducing the periodic sampling scheme, Zeno behaviors can be naturally avoided in both of the algorithms. Finally, simulation results are provided to illustrate the theoretical effectiveness.

Experimental validation of smartphones for measuring human-induced loads

Jun Chen,Huan Tan,Ziye Pan 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.3

The rapid technology developments in smartphones have created a significant opportunity for their use in structural live load measurements. This paper presents extensive experiments conducted in two stages to investigate this opportunity. Shaking table tests were carried out in the first stage using selected popular smartphones to measure the sinusoidal waves of various frequencies, the sinusoidal sweeping, and earthquake waves. Comparison between smartphone measurements and real inputs showed that the smartphones used in this study gave reliable measurements for harmonic waves in both time and frequency domains. For complex waves, smartphone measurements should be used with caution. In the second stage, three-dimensional motion capture technology was employed to explore the capacity of smartphones for measuring the movement of individuals in walking, bouncing and jumping activities. In these tests, reflective markers were attached to the test subject. The markers\' trajectories were recorded by the motion capture system and were taken as references. The smartphone measurements agreed well with the references when the phone was properly fixed. Encouraged by these experimental validation results, smartphones were attached to moving participants of this study. The phones measured the acceleration near the center-of-mass of his or her body. The human-induced loads were then reconstructed by the acceleration measurements in conjunction with a biomechanical model. Satisfactory agreement between the reconstructed forces and that measured by a force plate was observed in several instances, clearly demonstrating the capability of smartphones to accurately assist in obtaining human-induced load measurements.

Structural live load surveys by deep learning

Jun Chen,Yang Li 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.2

The design of safe and economical structures depends on the reliable live load from load survey. Live load surveys are traditionally conducted by randomly selecting rooms and weighing each item on-site, a method that has problems of low efficiency, high cost, and long cycle time. This paper proposes a deep learning-based method combined with Internet big data to perform live load surveys. The proposed survey method utilizes multi-source heterogeneous data, such as images, voice, and product identification, to obtain the live load without weighing each item through object detection, web crawler, and speech recognition. The indoor objects and face detection models are first developed based on fine-tuning the YOLOv3 algorithm to detect target objects and obtain the number of people in a room, respectively. Each detection model is evaluated using the independent testing set. Then web crawler frameworks with keyword and image retrieval are established to extract the weight information of detected objects from Internet big data. The live load in a room is derived by combining the weight and number of items and people. To verify the feasibility of the proposed survey method, a live load survey is carried out for a meeting room. The results show that, compared with the traditional method of sampling and weighing, the proposed method could perform efficient and convenient live load surveys and represents a new load research paradigm.

An Efcient New Hybrid ICA‑PSO Approach for Solving Large Scale Non‑convex Multi Area Economic Dispatch Problems

Jun Chen,Hashem Imani Marrani 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

Multi-area economic dispatch (MAED) is one of the vital problems in economic operation of interconnected power systems. This paper proposes a novel hybrid approach based on combined imperialist competitive algorithm (ICA) and particle swarm optimization (PSO) methods in order to determine the feasible optimal solution of the non-convex economic dispatch (ED) problem considering valve loading efects. In the proposed algorithm we have defned new type of countries in ICA algorithm, namely independent countries. These types of countries improve their position using a PSO based search strategy. The proposed method benefts from the advantage of the both algorithms. The proposed hybrid approach based on ICA-PSO is applied on diferent test systems and compared with most of the recent methodologies. Also, a large scale multi-area economic dispatch (MAED) problem is solved using the proposed hybrid approach to minimize total fuel cost in all areas while satisfying power balance constraints, generating limits and tie-line capacity constraints. The results show the efectiveness of the proposed approach and prove that ICA-PSO is applicable for solving the power system economic load dispatch problem, especially in large scale power systems.

Analysis of Characteristics of Swirling Spray of the Ammonium Dinitramide (ADN)-Based Green Monopropellant

Jun Chen,Guoxiu Li,Tao Zhang 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.4

Ammonium dinitramide (ADN) based green propellant is a promising alternative propellant for future space propulsion. Atomization of thruster plays an important role in the entire operation process. This paper describes the effect of swirl injection regarding tangential hole geometric parameter on the atomization characteristics of ADN-based green monopropellant. The experimental apparatus was prepared using a high-speed camera equipped with a macro lens and a Malvern laser particle size analyzer, and an injection device was designed. Characteristics features including particle-size distribution, spray cone, and breakup length of tangential hole number were recorded, and the effect of key parameters on spray processes was evaluated. The results show that the designed swirl injector completely achieved the atomization characteristics. With the increase in tangential hole number, the flow resistance increased, thus significantly affecting the atomization performance. The corresponding average particle size decreased. Moreover, a very large or small tangential hole number clearly affected the breakup length, spray cone angle, and average particle size. The optimum tangential hole diameter was 0.9 mm. The results are beneficial for the improvement of design structure of swirl nozzle based on ADN-based green monopropellant.

On Extraction of Time-varying Mean Wind Speed from Wind Record Based on Stationarity Index

Jun Chen,Min Wu 한국기상학회 2012 Asia-Pacific Journal of Atmospheric Sciences Vol.48 No.3

We have proposed in a previous study a non-stationary wind model to represent the typhoon record as a summation of a time-varying mean wind speed (TVM) and a stationary turbulence. This note further suggests a quantitative scheme, rather than the previous qualitative method, to find the best TVM for any given wind record. Trial TVMs are first extracted from the wind record by a data-processing technique named empirical mode decomposition. For each TVM, its corresponding turbulent component is computed by removing the TVM from the original wind record, and the degree of stationarity of the turbulence component is checked. The best TVM is taken as the one that leads to the maximum degree of stationarity. The degree of stationarity of turbulence is quantified by two indicators: β the ratio of horizontal wind variability and wind speed; and γ the ratio of friction velocity at different Reynolds averaging periods. The applicability of the suggested scheme is validated with 550 typhoon and 3300 monsoon records of 10 minute duration and at different measurement heights. Threshold values for the two stationary indicators β and γ are determined using field measurements and their sensitivities to the Reynolds averaging periods are discussed. Observations in this study demonstrate that the suggested scheme is proper for finding the TVM of a wind record. For a stationarity quantification of 10 minute duration record, the γindicator with 30 second Reynolds averaging period is recommended. We have proposed in a previous study a non-stationary wind model to represent the typhoon record as a summation of a time-varying mean wind speed (TVM) and a stationary turbulence. This note further suggests a quantitative scheme, rather than the previous qualitative method, to find the best TVM for any given wind record. Trial TVMs are first extracted from the wind record by a data-processing technique named empirical mode decomposition. For each TVM, its corresponding turbulent component is computed by removing the TVM from the original wind record, and the degree of stationarity of the turbulence component is checked. The best TVM is taken as the one that leads to the maximum degree of stationarity. The degree of stationarity of turbulence is quantified by two indicators: β the ratio of horizontal wind variability and wind speed; and γ the ratio of friction velocity at different Reynolds averaging periods. The applicability of the suggested scheme is validated with 550 typhoon and 3300 monsoon records of 10 minute duration and at different measurement heights. Threshold values for the two stationary indicators β and γ are determined using field measurements and their sensitivities to the Reynolds averaging periods are discussed. Observations in this study demonstrate that the suggested scheme is proper for finding the TVM of a wind record. For a stationarity quantification of 10 minute duration record, the γindicator with 30 second Reynolds averaging period is recommended.

DATCN: Deep Attention fused Temporal Convolution Network for the prediction of monitoring indicators in the tunnel

Junchen Ye,Bowen Du,Zhixin Zhang,Xuyan Tan,Wentao Li,Weizhong Chen 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.6

The prediction of structural mechanical behaviors is vital important to early perceive the abnormal conditions and avoid the occurrence of disasters. Especially for underground engineering, complex geological conditions make the structure more prone to disasters. Aiming at solving the problems existing in previous studies, such as incomplete consideration factors and can only predict the continuous performance, the deep attention fused temporal convolution network (DATCN) is proposed in this paper to predict the spatial mechanical behaviors of structure, which integrates both the temporal effect and spatial effect and realize the cross-time prediction. The temporal convolution network (TCN) and self-attention mechanism are employed to learn the temporal correlation of each monitoring point and the spatial correlation among different points, respectively. Then, the predicted result obtained from DATCN is compared with that obtained from some classical baselines, including SVR, LR, MLP, and RNNs. Also, the parameters involved in DATCN are discussed to optimize the prediction ability. The prediction result demonstrates that the proposed DATCN model outperforms the state-of-the-art baselines. The prediction accuracy of DATCN model after 24 hours reaches 90 percent. Also, the performance in last 14 hours plays a domain role to predict the short-term behaviors of the structure. As a study case, the proposed model is applied in an underwater shield tunnel to predict the stress variation of concrete segments in space.

A Comparative Study of LCCL-S/P/LCL/LCCL Topologies in Inductive Power Transfer Systems

Junchen Xie(사준신),Seung-Jin Jo(조승진),Chang-Su Shin(신창수),Dong-Hee Kim(김동희) 전력전자학회 2021 전력전자학술대회 논문집 Vol.2021 No.7

Analysis on the Dynamic Responses of an Overlapped Circular Shield Tunnel under the Different Vibration Loads

Qixiang Yan,Junchen Zhang,Wenyu Chen,Chaofan Yao,Wenbo Yang,Hang Chen,Xirui Liu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.10

At present, there are many studies on the dynamic response of overlapped tunnels, but most of them are through numerical simulation. Very few has been conducted by the experimental model research and frequency domain analysis. Combined with the model test and the numerical simulation, the dynamic response of the tunnel lining structure under the action of different train speeds and different tunnel clear distances are investigated, which can remedy the deficiencies in the relevant fields and verify the accuracy of numerical simulation results. The results show that as the train speed increases, the amplitude of the energy spectra of the vibration loads decrease significantly. The tunnel response at the sidewalls is smaller than that at the tunnel crown and at the invert in the lower tunnel. As the net distance increases, the amplitudes of the acceleration frequency spectrum and the energy spectra of the lower tunnel decrease, but with a diminishing rate. The dynamic coefficients of circumferential of the upper tunnel under a train load are larger than those in the longitudinal direction in the invert.