Stable modal identification for civil structures based on a stochastic subspace algorithm with appropriate selection of time lag parameter

Wu, Wen-Hwa,Wang, Sheng-Wei,Chen, Chien-Chou,Lai, Gwolong Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.4

Based on the alternative stabilization diagram by varying the time lag parameter in the stochastic subspace identification analysis, this study aims to investigate the measurements from several cases of civil structures for extending the applicability of a recently noticed criterion to ensure stable identification results. Such a criterion demands the time lag parameter to be no less than a critical threshold determined by the ratio of the sampling rate to the fundamental system frequency and is firstly validated for its applications with single measurements from stay cables, bridge decks, and buildings. As for multiple measurements, it is found that the predicted threshold works well for the cases of stay cables and buildings, but makes an evident overestimation for the case of bridge decks. This discrepancy is further explained by the fact that the deck vibrations are induced by multiple excitations independently coming from the passing traffic. The cable vibration signals covering the sensor locations close to both the deck and pylon ends of a cable-stayed bridge provide convincing evidences to testify this important discovery.

Mode identifiability of a cable-stayed bridge under different excitation conditions assessed with an improved algorithm based on stochastic subspace identification

Wen-Hwa Wu,Sheng-Wei Wang,Chien-Chou Chen,Gwolong Lai 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.3

Deficient modes that cannot be always identified from different sets of measurement data may exist in the application of operational modal analysis such as the stochastic subspace identification techniques in large-scale civil structures. Based on a recent work using the long-term ambient vibration measurements from an instrumented cable-stayed bridge under different wind excitation conditions, a benchmark problem is launched by taking the same bridge as a test bed to further intensify the exploration of mode identifiability. For systematically assessing this benchmark problem, a recently developed SSI algorithm based on an alternative stabilization diagram and a hierarchical sifting process is extended and applied in this research to investigate several sets of known and blind monitoring data. The evaluation of delicately selected cases clearly distinguishes the effect of traffic excitation on the identifiability of the targeted deficient mode from the effect of wind excitation. An additional upper limit for the vertical acceleration amplitude at deck, mainly induced by the passing traffic, is subsequently suggested to supplement the previously determined lower limit for the wind speed. Careful inspection on the shape vector of the deficient mode under different excitation conditions leads to the postulation that this mode is actually induced by the motion of the central tower. The analysis incorporating the tower measurements solidly verifies this postulation by yielding the prevailing components at the tower locations in the extended mode shape vector. Moreover, it is also confirmed that this mode can be stably identified under all the circumstances with the addition of tower measurements. An important lesson learned from this discovery is that the problem of mode identifiability usually comes from the lack of proper measurements at the right locations.

A novel recursive stochastic subspace identification algorithm with its application in long-term structural health monitoring of office buildings

Wen-Hwa Wu,Jhe-Wei Jhou,Chien-Chou Chen,Gwolong Lai 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.4

This study develops a novel recursive algorithm to significantly enhance the computation efficiency of a recently proposed stochastic subspace identification (SSI) methodology based on an alternative stabilization diagram. Exemplified by the measurements taken from the two investigated office buildings, it is first demonstrated that merely one sixth of computation time and one fifth of computer memory are required with the new recursive algorithm. Such a progress would enable the realization of on-line and almost real-time monitoring for these two steel framed structures. This recursive SSI algorithm is further applied to analyze 20 months of monitoring data and comprehensively assess the environmental effects. It is certified that the root-mean-square (RMS) response can be utilized as an excellent index to represent most of the environmental effects and its variation strongly correlates with that of the modal frequency. More detailed examination by comparing the monthly correlation coefficient discloses that larger variations in modal frequency induced by greater RMS responses would typically lead to a higher correlation.

Assessment of environmental effects in scour monitoring of a cable-stayed bridge simply based on pier vibration measurements

Wu, Wen-Hwa,Chen, Chien-Chou,Shi, Wei-Sheng,Huang, Chun-Ming Techno-Press 2017 Smart Structures and Systems, An International Jou Vol.20 No.2

A recent work by the authors has demonstrated the feasibility of scour evaluation for Kao-Ping-Hsi Cable-Stayed Bridge simply based on ambient vibration measurements. To further attain the goal of scour monitoring, a key challenge comes from the interference of several environmental factors that may also significantly alter the pier frequencies without the change of scour depth. Consequently, this study attempts to investigate the variation in certain modal frequencies of this bridge induced by several environmental factors. Four sets of pier vibration measurements were taken either during the season of plum rains, under regular summer days without rain, or in a period of typhoon. These signals are analyzed with the stochastic subspace identification and empirical mode decomposition techniques. The variations of the identified modal frequencies are then compared with those of the corresponding traffic load, air temperature, and water level. Comparison of the analyzed results elucidates that both the traffic load and the environmental temperature are negatively correlated with the bridge frequencies. However, the traffic load is clearly a more dominant factor to alternate the identified bridge deck frequency than the environmental temperature. The pier modes are also influenced by the passing traffic on the bridge deck, even though with a weaker correlation. In addition, the variation of air temperature follows a similar tendency as that of the passing traffic, but its effect on changing the bridge frequencies is obviously not as significant. As for the effect from the alternation of water level, it is observed that the frequency baselines of the pier modes may positively correlate with the water level during the seasons of plum rains and typhoon.

Association of AXIN1 With Parkinson’s Disease in a Taiwanese Population

Hwa-Shin Fang,Chih-Ying Chao,Chun-Chieh Wang,Wen-Lang Fan,Po-Jung Huang,Hon-Chung Fung,Yih-Ru Wu 대한파킨슨병및이상운동질환학회 2022 Journal Of Movement Disorders Vol.15 No.1

A meta-analysis of locus-based genome-wide association studies recently identified a relationship between AXIN1 and Parkinson’s disease (PD). Few studies of Asian populations, however, have reported such a genetic association. The influences of rs13337493, rs758033, and rs2361988, three PD-associated genetic variants of AXIN1, were investigated in the present study because AXIN1 is related to Wnt/β-catenin signaling.

A Pilot Plant Study of Aerobic and Anaerobic Selectors to Control Bulking in An Activated Sludge to Treat PET Wastewater

( Wen Yuang Tzou,Chang Fan Chion,You Ching Liu,Hann Song Wu,Ren Yang Horng,Ching Hwa Chen,Hsin Shao,Huey Song You,Sheng Shung Cheng ) 한국물환경학회 1997 제6차 국제수질보전학회 아시아 태평양지역 학술회의 Vol.1 No.-

A Systemic Review and Experts’ Consensus for Long-acting Injectable Antipsychotics in Bipolar Disorder

Yuan-Hwa Chou,Po-Chung Chu,Szu-Wei Wu,Jen-Chin Lee,Yi-Hsuan Lee,I-Wen Sun,Chen-Lin Chang,Chien-Liang Huang,I-Chao Liu,Chia-Fen Tsai,Yung-Chieh Yen 대한정신약물학회 2015 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.13 No.2

Bipolar disorder (BD) is a major psychiatric disorder that is easily misdiagnosed. Patient adherence to a treatment regimen is of utmost importance for successful outcomes in BD. Several trials of antipsychotics suggested that depot antipsychotics, including long-acting first- and second-generation agents, are effective in preventing non-adherence, partial adherence, and in reducing relapse in BD. Various long-acting injectable (LAI) antipsychotics are available, including fluphenazine decanoate, haloperidol decanoate, olanzapine pamoate, risperidone microspheres, paliperidone palmitate, and aripiprazole monohydrate. Due to the increasing number of BD patients receiving LAI antipsychotics, treatment guidelines have been developed. However, the clinical applicability of LAI antipsychotics remains a global cause for concern, particularly in Asian countries. Expert physicians from Taiwan participated in a consensus meeting, which was held to review key areas based on both current literature and clinical practice. The purpose of this meeting was to generate a practical and implementable set of recommendations for LAI antipsychotic use to treat BD; target patient groups, dosage, administration, and adverse effects were considered. Experts recommended using LAI antipsychotics in patients with schizophrenia, rapid cycling BD, BD I, and bipolar-type schizoaffective disorder. LAI antipsychotic use was recommended in BD patients with the following characteristics: multiple episodes and low adherence; seldom yet serious episodes; low adherence potential per a physician’s clinical judgment; preference for injectable agents over oral agents; and multiple oral agent users still experiencing residual symptoms.

Determination of stay cable force based on effective vibration length accurately estimated from multiple measurements

Chen, Chien-Chou,Wu, Wen-Hwa,Huang, Chin-Hui,Lai, Gwolong Techno-Press 2013 Smart Structures and Systems, An International Jou Vol.11 No.4

Due to its easy operation and wide applicability, the ambient vibration method is commonly adopted to determine the cable force by first identifying the cable frequencies from the vibration signals. With given vibration length and flexural rigidity, an analytical or empirical formula is then used with these cable frequencies to calculate the cable force. It is, however, usually difficult to decide the two required parameters, especially the vibration length due to uncertain boundary constraints. To tackle this problem, a new concept of combining the modal frequencies and mode shape ratios is fully explored in this study for developing an accurate method merely based on ambient vibration measurements. A simply supported beam model with an axial tension is adopted and the effective vibration length of cable is then independently determined based on the mode shape ratios identified from the synchronized measurements. With the effective vibration length obtained and the identified modal frequencies, the cable force and flexural rigidity can then be solved using simple linear regression techniques. The feasibility and accuracy of the proposed method is extensively verified with demonstrative numerical examples and actual applications to different cable-stayed bridges. Furthermore, several important issues in engineering practice such as the number of sensors and selection of modes are also thoroughly investigated.

Damage detection of a cable-stayed bridge based on the variation of stay cable forces eliminating environmental temperature effects

Chien-Chou Chen,Wen-Hwa Wu,Chun-Yan Liu,Gwolong Lai 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.6

This study aims to establish an effective methodology for the detection of instant damages occurred in cable-stayed bridges with the measurements of cable vibration and structural temperatures. A transfer coefficient for the daily temperature variation and another for the long-term temperature variation are firstly determined to eliminate the environmental temperature effects from the cable force variation. Several thresholds corresponding to different levels of exceedance probability are then obtained to decide four upper criteria and four lower criteria for damage detection. With these criteria, the monitoring data for three stay cables of Ai-Lan Bridge are analyzed and compared to verify the proposed damage detection methodology. The simulated results to consider various damage scenarios unambiguously indicate that the damages with cable force changes larger than +-1.5% can be detected within 12 hours. Even though not exhaustively reflecting the environmental temperature effects on the cable force variation, both the effective temperature and the air temperature can be considered as valid indices to eliminate these effects at high and low monitoring costs.

Determination of stay cable force based on effective vibration length accurately estimated from multiple measurements

Chien-Chou Chen,Wen-Hwa Wu,Chin-Hui Huang,Gwolong Lai 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.11 No.4

Due to its easy operation and wide applicability, the ambient vibration method is commonly adopted to determine the cable force by first identifying the cable frequencies from the vibration signals. With given vibration length and flexural rigidity, an analytical or empirical formula is then used with these cable frequencies to calculate the cable force. It is, however, usually difficult to decide the two required parameters, especially the vibration length due to uncertain boundary constraints. To tackle this problem, a new concept of combining the modal frequencies and mode shape ratios is fully explored in this study for developing an accurate method merely based on ambient vibration measurements. A simply supported beam model with an axial tension is adopted and the effective vibration length of cable is then independently determined based on the mode shape ratios identified from the synchronized measurements. With the effective vibration length obtained and the identified modal frequencies, the cable force and flexural rigidity can then be solved using simple linear regression techniques. The feasibility and accuracy of the proposed method is extensively verified with demonstrative numerical examples and actual applications to different cable-stayed bridges. Furthermore, several important issues in engineering practice such as the number of sensors and selection of modes are also thoroughly investigated.