Performance of structures and infrastructure facilities during an EF4 Tornado in Yancheng

Tianyou Tao,Hao Wang,Chengyuan Yao,Zhongqin Zou,Zidong Xu 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.2

Heavy damages to properties with attendant losses were frequently caused by tornadoes in recent years. This natural hazard is one of the most destructive wind events that must be fully studied and well understood in order to keep the safety of structures and infrastructure facilities. On June 23, 2016, a severe tornado, which is an Enhanced Fujita (EF) 4 storm, occurred in the rim of a coastal city named as Yancheng in China. Numerous low-rise buildings as well as facilities (e.g., transmission towers) were destroyed or damaged. In this paper, damages to structures and infrastructure facilities by the severe tornado are reviewed. The collapses of residential buildings, industrial structures and other infrastructure facilities are described. With an overview of the damages, various possible mechanisms of the collapse are then discussed and utilized to reveal the initiation of the damage to various facilities. It is hoped that this paper can provide a concise but comprehensive reference for the researchers and engineers to help understand the tornado effects on structures and expose the vulnerabilities that need to be improved in current wind-resistant design practices.

Stationary and non-stationary buffeting analyses of a long-span bridge under typhoon winds

Tianyou Tao,Hao Wang,Peng Shi,Hang Li 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.5

The buffeting response is a vital consideration for long-span bridges in typhoon-prone areas. In the conventional analysis, the turbulence and structural vibrations are assumed as stationary processes, which are, however, inconsistent with the non-stationary features observed in typhoon winds. This poses a question on how the stationary assumption would affect the evaluation of buffeting responses under non-stationary wind actions in nature. To figure out this problem, this paper presents a comparative study on buffeting responses of a long-span cable-stayed bridge based on stationary and non-stationary perspectives. The stationary and non-stationary buffeting analysis frameworks are firstly reviewed. Then, a modal analysis of the example bridge, Sutong Cable-stayed Bridge (SCB), is conducted, and stationary and non-stationary spectral models are derived based on measured typhoon winds. On this condition, the buffeting responses of SCB are finally analyzed by following stationary and non-stationary approaches. Although the stationary results are almost identical with the non-stationary results in the mean sense, the root-mean-square value of buffeting responses are underestimated by the stationary assumption as the time-varying features existing in the spectra of turbulence are neglected. The analytical results highlights a transition from stationarity to non-stationarity in the buffeting analysis of long-span bridges.

Stationary and nonstationary analysis on the wind characteristics of a tropical storm

Tianyou Tao,Hao Wang,Aiqun Li 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.6

Nonstationary features existing in tropical storms have been frequently captured in recent field measurements, and the applicability of the stationary theory to the analysis of wind characteristics needs to be discussed. In this study, a tropical storm called Nakri measured at Taizhou Bridge site based on structural health monitoring (SHM) system in 2014 is analyzed to give a comparison of the stationary and nonstationary characteristics. The stationarity of the wind records in the view of mean and variance is first evaluated with the run test method. Then the wind data are respectively analyzed with the traditional stationary model and the wavelet-based nonstationary model. The obtained wind characteristics such as the mean wind velocity, turbulence intensity, turbulence integral scale and power spectral density (PSD) are compared accordingly. Also, the stationary and nonstationary PSDs are fitted to present the turbulence energy distribution in frequency domain, among which a modulating function is included in the nonstationary PSD to revise the non-monotonicity. The modulated nonstationary PSD can be utilized to unconditionally simulate the turbulence presented by the nonstationary wind model. The results of this study recommend a transition from stationarity to nonstationarity in the analysis of wind characteristics, and further in the accurate prediction of wind-induced vibrations for engineering structures.

Performance of structures and infrastructure facilities during an EF4 Tornado in Yancheng

Tao, Tianyou,Wang, Hao,Yao, Chengyuan,Zou, Zhongqin,Xu, Zidong Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.2

Heavy damages to properties with attendant losses were frequently caused by tornadoes in recent years. This natural hazard is one of the most destructive wind events that must be fully studied and well understood in order to keep the safety of structures and infrastructure facilities. On June 23, 2016, a severe tornado, which is an Enhanced Fujita (EF) 4 storm, occurred in the rim of a coastal city named as Yancheng in China. Numerous low-rise buildings as well as facilities (e.g., transmission towers) were destroyed or damaged. In this paper, damages to structures and infrastructure facilities by the severe tornado are reviewed. The collapses of residential buildings, industrial structures and other infrastructure facilities are described. With an overview of the damages, various possible mechanisms of the collapse are then discussed and utilized to reveal the initiation of the damage to various facilities. It is hoped that this paper can provide a concise but comprehensive reference for the researchers and engineers to help understand the tornado effects on structures and expose the vulnerabilities that need to be improved in current wind-resistant design practices.

문제은행간 비동등성이 능력모수 추정치에 미치는 영향

반재천,Tianyou Wang,Qing Yi,Deborah J. Harris 한국교육평가학회 2003 교육평가연구 Vol.16 No.2

이 연구는 비동형 문제은행(nonparallel item pools)이 개인의 능력모수 추정과 각 내용영역별 사용된 문항의 수에 미치는 영향을 파악하는데 그 목적이 있었다. 두 세트의 다섯 개 문제은행이 측정학적 속성(b-모수 추정치의 평균)과 내용영역별 문항의 비율이 다르도록 scocking과 Swanson(1996)의 가중편차모델(Weighted deiation model: WDM)을 이용하여 구성하였다 한 세트의 다섯 개 문제은행은 문항수가 240개였고, 다른 세트의 다섯 문제은행은 문항수가 480개였다. 이렇게 구성된 문제은행을 이용하여 시뮬레이션을 통한 컴푸터적용검사(Computerized adaptivetesting; CAT)를 실시하였다. 능력모수추정을 위해 최대우도법을 사용하였고, 검사길이는 30문항이었다. 문항의 개별 노출빈도(item exposure)를 통제하였고, 모의인에게 시행되는 검사가 내용영역별로 균형을 맞추도록 WDM을 이용하여 통제하였다, 전체적으로 보았을 때 하 ·상위능력집단에서 문제은행간 비동등성이 능력모수 추정에 중간능력집단에 비해 상대적으로 영향이 컸다. 그러나 그런 차이가 실제적으로 의미있는 차이인지는 보고되는 점수척도로 변환해서 판단하여야 한다. 문제은행의 내용영역별 문항의 비율이 다를 때 각 개인에게 시행된 문항들의 영역별 비율에 차이가 있었다. 문항의 사용빈도를 통제함에도 상대적으로 문항이 많은 영역에서 보다 많은 문항들이 시행되었다. 따라서 각 검사프로그램마다 적절한 문항선정을 위한 알고리듬을 사용하여서 시뮬레이션을 통해 영역별 문항사용빈도를 통제하는 것이 바람직하다. This study focused on the effects of nonparallel item pools on examinees' ability estimates and on the number of administered items in each content category. Two sets of five nonparallel multiple item pools were constructed to be moderately different in the psychometric characteristic (i.e., mean of the b-parameters) and the percentages of items per content category through Stocking and Swanson (1996)'s weighted deviation model (WDM). One set of five nonparallel item pools had 240 items and the Other set of five pools had 480 items. CAT simulations were performed based on the assembled item pools. The MLE procedure was used for scoring, and the test length was 30 items. Item exposure control was imposed. Stocking and Swanson (993)'s WDM was used for the item selection to balance the content categories. Overall, the results indicated that the precision of ability estimates was more affected at low and high ability levels than at the middle level of ability by the moderate change of the psychometric characteristic across item pools. However, the meaningfulness of the differences should be determined based on the reported score scale. The nonparallel pools in terms of proportion of items per content category had an effect on the number of items administered in each content category.

Wind power spectra for coastal area of East Jiangsu Province based on SHMS

Hao Wang,Tianyou Tao,Teng Wu 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2

A wind velocity power spectrum (WVPS) with high fidelity is extremely important for accurate prediction of structural buffeting response. WVPS heavily depends on the geographical locations, local terrains and topographies. Hence, field measurement of wind characteristics may be the unique way to obtain the accurate WVPS for a specific region. In this paper, a systematic analysis and discussions of existing WVPSs were performed. Six recorded strong wind data from the structural health monitoring systems (SHMS) of Runyang Suspension Bridge (RSB) and Sutong Cable-stayed Bridge (SCB) in Jiangsu Province of China were selected for analysis. The measured and pre-processed wind velocity data was first transformed from time domain to frequency domain to obtain the measured spectrum. The spectrum for each strong wind was then fitted using the nonlinear least square method and compared with both the fitted spectrum from statistical analysis and the recommended spectrum in specifications. The modified Kaimal spectrum was proved to be the "best" choice for the coastal area of East Jiangsu Province. Finally, a suitable WVPS formula fit for the coastal area of East Jiangsu Province was presented based on the modified Kaimal spectrum. Results in this study provide a more accurate and reliable WVPS for wind-resistant design of engineering structures in the coastal area of East Jiangsu Province.

Joint distribution of wind speed and direction in the context of field measurement

Hao Wang,Tianyou Tao,Teng Wu,Jianxiao Mao,Aiqun Li 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.5

The joint distribution of wind speed and wind direction at a bridge site is vital to the estimation of the basic wind speed, and hence to the wind-induced vibration analysis of long-span bridges. Instead of the conventional way relying on the weather stations, this study proposed an alternate approach to obtain the original records of wind speed and the corresponding directions based on field measurement supported by the Structural Health Monitoring System (SHMS). Specifically, SHMS of Sutong Cable-stayed Bridge (SCB) is utilized to study the basic wind speed with directional information. Four anemometers are installed in the SHMS of SCB: upstream and downstream of the main deck center, top of the north and south tower respectively. Using the recorded wind data from SHMS, the joint distribution of wind speed and direction is investigated based on statistical methods, and then the basic wind speeds in 10-year and 100-year recurrence intervals at these four key positions are calculated. Analytical results verify the reliability of the recorded wind data from SHMS, and indicate that the joint probability model for the extreme wind speed at SCB site fits well with the Weibull model. It is shown that the calculated basic wind speed is reduced by considering the influence of wind direction. Compared to the design basic wind speed in the Specification of China, basic wind speed considering the influence of direction or not is much smaller, indicating a high safety coefficient in the design of SCB. The results obtained in this study can provide not only references for further wind-resistance research of SCB, but also improve the understanding of the safety coefficient for wind-resistance design of other engineering structures in the similar area.

Structural health monitoring system for Sutong Cable-stayed Bridge

Hao Wang,Tianyou Tao,Aiqun Li,Yufeng Zhang 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.2

Structural Health Monitoring System (SHMS) works as an efficient platform for monitoring the health status and performance deterioration of engineering structures during long-term service periods. The objective of its installation is to provide reasonable suggestions for structural maintenance and management, and therefore ensure the structural safety based on the information extracted from the real-time measured data. In this paper, the SHMS implemented on a world-famous kilometer-level cable-stayed bridge, named as Sutong Cable-stayed Bridge (SCB), is introduced in detail. The composition and core functions of the SHMS on SCB are elaborately presented. The system consists of four main subsystems including sensory subsystem, data acquisition and transmission subsystem, data management and control subsystem and structural health evaluation subsystem. All of the four parts are decomposed to separately describe their own constitutions and connected to illustrate the systematic functions. Accordingly, the main techniques and strategies adopted in the SHMS establishment are presented and some extension researches based on structural health monitoring are discussed. The introduction of the SHMS on SCB is expected to provide references for the establishment of SHMSs on long-span bridges with similar features as well as the implementation of potential researches based on structural health monitoring.

Wind power spectra for coastal area of East Jiangsu Province based on SHMS

Wang, Hao,Tao, Tianyou,Wu, Teng Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2

A wind velocity power spectrum (WVPS) with high fidelity is extremely important for accurate prediction of structural buffeting response. WVPS heavily depends on the geographical locations, local terrains and topographies. Hence, field measurement of wind characteristics may be the unique way to obtain the accurate WVPS for a specific region. In this paper, a systematic analysis and discussions of existing WVPSs were performed. Six recorded strong wind data from the structural health monitoring systems (SHMS) of Runyang Suspension Bridge (RSB) and Sutong Cable-stayed Bridge (SCB) in Jiangsu Province of China were selected for analysis. The measured and pre-processed wind velocity data was first transformed from time domain to frequency domain to obtain the measured spectrum. The spectrum for each strong wind was then fitted using the nonlinear least square method and compared with both the fitted spectrum from statistical analysis and the recommended spectrum in specifications. The modified Kaimal spectrum was proved to be the "best" choice for the coastal area of East Jiangsu Province. Finally, a suitable WVPS formula fit for the coastal area of East Jiangsu Province was presented based on the modified Kaimal spectrum. Results in this study provide a more accurate and reliable WVPS for wind-resistant design of engineering structures in the coastal area of East Jiangsu Province.

Joint distribution of wind speed and direction in the context of field measurement

Wang, Hao,Tao, Tianyou,Wu, Teng,Mao, Jianxiao,Li, Aiqun Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.5

The joint distribution of wind speed and wind direction at a bridge site is vital to the estimation of the basic wind speed, and hence to the wind-induced vibration analysis of long-span bridges. Instead of the conventional way relying on the weather stations, this study proposed an alternate approach to obtain the original records of wind speed and the corresponding directions based on field measurement supported by the Structural Health Monitoring System (SHMS). Specifically, SHMS of Sutong Cable-stayed Bridge (SCB) is utilized to study the basic wind speed with directional information. Four anemometers are installed in the SHMS of SCB: upstream and downstream of the main deck center, top of the north and south tower respectively. Using the recorded wind data from SHMS, the joint distribution of wind speed and direction is investigated based on statistical methods, and then the basic wind speeds in 10-year and 100-year recurrence intervals at these four key positions are calculated. Analytical results verify the reliability of the recorded wind data from SHMS, and indicate that the joint probability model for the extreme wind speed at SCB site fits well with the Weibull model. It is shown that the calculated basic wind speed is reduced by considering the influence of wind direction. Compared to the design basic wind speed in the Specification of China, basic wind speed considering the influence of direction or not is much smaller, indicating a high safety coefficient in the design of SCB. The results obtained in this study can provide not only references for further wind-resistance research of SCB, but also improve the understanding of the safety coefficient for wind-resistance design of other engineering structures in the similar area.