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CONTENTS
Volume 83, Number 1, July10 2022
 


Abstract
The static design approach in the current code implies that the inherent torsional moment represents the state of zero inertial torsional moments at the center of mass (CM). However, both experimental and analytical results prove the existence of a large amount of the inertial torsional moment at the CM. Also, the definition of eccentricity by engineers, which is referred to as the resistance eccentricity, is defined as the distance between the center of mass and the center of resistance, which is conceptually different from the static eccentricity in the current codes, defined as the arm length about the center of rotation. The difference in the definitions of eccentricity should be made clear to avoid confusion about the torsion design. This study proposed prediction equations as a function of resistance eccentricity based on a resistance eccentricity model with advantages of (1) the recognition of the existence of torsional moment at the CM, (2) the avoidance of the confusion by using resistance eccentricity instead of the design eccentricity, and (3) a clear relationship of applied inertial forces at the CM and resisting forces. These predictions are compared with the seismic responses obtained from time-history analyses of a five-story building structure under moderate and severe earthquakes. Then, the trend of the resistance eccentricity corresponding to the maximum edge drift is investigated for elastic and inelastic responses. The comparison given in this study shows that these prediction equations can serve as a useful reference for the prediction in both the elastic and the inelastic ranges.

Key Words
accidental eccentricity; asymmetric structures; reinforced concrete building structure; resistance eccentricity; seismic design; torsion

Address
Ruth A. Abegaz: Renewable Energy Research Institute, Kunsan National University, Gunsan, 54150, Republic of Korea
In-Ho Kim: Department of Civil Engineering, Kunsan National University, Gunsan, 54150, Republic of Korea
Han Seon Lee: School of Civil, Environmental, and Architectural Engineering, Korea University, Seoul, 02841, Republic of Korea

Abstract
The angle steel frame confined concrete columns (ASFCs) are an emerging form of hybrid columns, which comprise an inner angle steel frame and a concrete column. The inner angle steel frame can provide axial bearing capacity and well confining effect for composite columns. This paper presents the experimental and theoretical studies on the seismic behaviour of ASFCs. The experimental study of the 6 test specimens is presented, based on the previous study of the authors. The theoretical study includes two parts. One part establishes the section analysis model, and it uses to analyze section axial force-momentcurvature. Another part establishes the section moment-curvature hysteresis model. The test and analysis results show that the axial compression ratio and the assembling of steel slabs influence the local buckling of the angle steel. The three factors (axial compression ratio, content of angle steel and confining effect) have important effects on the seismic behaviour of ASFCs. And the theoretical model can provide reasonably accurate predictions and apply in section analysis of ASFCs.

Key Words
ASFCs; experimental study; section analysis model; section moment-curvature hysteresis model; seismic performance; theoretical study

Address
Chong Rong: State Key Laboratory of Green Building in Western China of Xian University of Architecture & Technology, Xi'an 710055, China; College of Civil Engineering, Xi'an University of Architecture & Technology, Xi

Abstract
A nonlinear gas-spring tuned mass damper is proposed to mitigate the seismic responses of the multi-degree-offreedom (MDOF) structure, in which the nine-story benchmark model is selected as the controlled object. The nonlinear mechanical properties of the gas-spring are investigated through theoretical analysis and experiments, and the damper's control parameters are designed. The control performance and damping mechanism of the proposed damper attached to the MDOF structure are systematically studied, and its reliability is also explored by parameter sensitivity analysis. The results illustrate that the nonlinear gas-spring TMD can transfer the primary structure's vibration energy from the lower to the higher modes, and consume energy through its own relative movement. The proposed damper has excellent "Reconciling Control Performance", which not only has a comparable control effect as the linear TMD, but also has certain advantages in working stroke. Furthermore, the control parameters of the gas-spring TMD can be determined according to the external excitation amplitude and the gas-spring's initial volume.

Key Words
damping mechanism; gas-spring tuned mass damper; MDOF structure; nonlinear energy sink; passive control; tuned mass damper

Address
Kunjie Rong: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China
Zheng Lu: Department of Disaster Mitigation for Structures, Tongji University, Shanghai, 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, 200092, China

Abstract
The need to account for accidental torsion in seismic design is no longer debatable, however, the seismic codes' requirement for accidental eccentricity has recently faced criticism. In order to get as close to real conditions as possible, this study investigated the impact of accidental torsion in symmetric RC multistory buildings caused by one of its many sources, the torsional earthquake component, and compared the results to those obtained by using the accidental eccentricity recommended by the codes (shifting the center of mass). To cover a wide range of frequencies and site conditions, two types of torsion seismic components were used: a recorded torsion accelerogram and five others generated using translation accelerograms. The main parameters that govern seismic responses, such as the number of stories (to account for the influence of all modes of vibration) and the frequency ratio (u) variation, were studied in terms of inter-story drift and displacement responses, as well as torsional moment. The results show that the eccentricity ratio of 5% required by most codes for accidental torsion should be reexamined and that it is prudent for computer analysis to use the static moment approach to implement the accidental eccentricity while waiting for new seismic code recommendations on the subject.

Key Words
accidental eccentricity; accidental torsion; earthquake engineering; symmetric reinforced concrete buildings; torsional ground motion

Address
Abderrahmane Ouazir: Department of Civil Engineering, College of Engineering, University of Ha'il, Hail, Saudi Arabia
Asma Hadjadj: Department of Interior Designl Engineering, College of Engineering, University of Ha'il, Hail, Saudi Arabia
Hatem Gasmi: Department of Civil Engineering, College of Engineering, University of Ha'il, Hail, Saudi Arabia; LR14ES03 Laboratoire d'Ingénierie Géotechnique, Ecole Nationale d'Ingénieurs de Tunis, Université de Tunis El Manar, 1002 Tunis, Tunisia
Hatem Karoui: LR14ES03 Laboratoire d'Ingénierie Géotechnique, Ecole Nationale d'Ingénieurs de Tunis, Université de Tunis El Manar, 1002 Tunis, Tunisia

Abstract
The main objective of the present research was investigating the effects of a floating wave barrier installed in front of an offshore jacket structure on the wave height, base shear, and overturning moment. A jacket model with the height of 4.55 m was fabricated and tested in the 402 m-long wave flume of NIMALA marine laboratory. The jacket was tested at the water depth of 4 m subjected to the random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20 cm, 23 cm, and 28 cm. Two different cross sections with the same area were selected for the wave barrier: square and rhombus. Results showed that the average decrease in the jacket's base shear due to the presence of a floating wave barrier with square and rhombus cross section was 24.67% and 34.29%, respectively. The use of wave barriers with square and rhombus cross sections also resulted in 19.78% and 33.11% decrease in the jacket's overturning moment, respectively. Hence, it can be concluded that a floating wave barrier can significantly reduce the base shear and overturning moment in an offshore jacket structure; and a rhombus cross section is more effective than an equivalent square section.

Key Words
floating wave barrier; jacket structure; NIMALA wave flume; overturning moment; random waves

Address
Arash Dalili Osgouei: Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Ramin Vafaei Poursorkhabi: Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran
Hamed Hosseini: Department of Civil Engineering, Dolatabad Branch, Islamic Azad University, Isfahan, Dolatabad, Iran
Diyar N. Qader: Department of Civil Engineering, College of Engineering, Cihan University-Erbil, Erbil, Kurdistan Region, Iraq
Ahmad Maleki: Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Hamid Ahmadi: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract
In this study, frictionless continuous and discontinuous contact problems of a magneto-electro-elastic layer in the presence of the body force were discussed. The layer was indented by a rigid cylindrical insulating punch and supported by a rigid substrate without bond. Applying the Fourier integral transform technique, the general expressions of the problem were derived in the presence of body force. Thanks to the boundary conditions, the singular integral equations were obtained for both the continuous and the discontinuous contact cases. Gauss–Chebyshev integration formulas were used to transform the singular integral equations into a set of nonlinear equations. Contact width under the punch, initial separation distance, critical load, separation regions and contact stress under the punch and between the layer, and substrate were given as a result.

Key Words
body force; contact problem; continuous and discontinuous contact problem; Fourier integral transform; magneto-electro-elastic materials; singular integral equation

Address
İsa Çömez: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Türkiye
Pembe Merve Karabulut: Department of Civil Engineering, Cank

Abstract
In this paper, the impact of a vernacular pozzolanic kaolinite mine on concrete alkali-silica reaction and strength has been evaluated. For making the samples, kaolinite powder with various levels has been used in the quality specification test of aggregates based on the ASTM C1260 standard in order to investigate the effect of kaolinite particles on reducing the reaction of the mortar bars. The compressive strength, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) experiments have been performed on concrete specimens. The obtained results show that addition of kaolinite powder to concrete will cause a pozzolanic reaction and decrease the permeability of concrete samples comparing to the reference concrete specimen. Further, various machine learning methods have been used to predict ASR-induced expansion per different amounts of kaolinite. In the process of modeling methods, optimal method is considered to have the lowest mean square error (MSE) simultaneous to having the highest correlation coefficient (R). Therefore, to evaluate the efficiency of the proposed model, the results of the support vector machine (SVM) method were compared with the decision tree method, regression analysis and neural network algorithm. The results of comparison of forecasting tools showed that support vector machines have outperformed the results of other methods. Therefore, the support vector machine method can be mentioned as an effective approach to predict ASR-induced expansion.

Key Words
alkali-silica reaction (asr); kaolinite powder; machine learning; support vector machine

Address
Moein Aflatoonian and Ramin Tabatabaei Mirhosseini: Department of Civil Engineering, Faculty of Engineering, Islamic Azad University, Kerman Branch, Kerman, Iran

Abstract
Real-time hybrid simulation (RTHS) was applied to investigate the train-bridge interaction of a high-speed railway system, where the railway bridge was selected as the numerical substructure, and the train was physically tested. The interaction between the two substructures was reproduced by a servo-hydraulic shaking table. To accurately reproduce the high-frequency interaction responses ranging from 10-25Hz using the hydraulic shaking table with an inherent delay of 6-50ms, an adaptive time series (ATS) compensation algorithm combined with the linear quadratic Gaussian (LQG) was proposed and implemented in the RTHS. Testing cases considering different train speeds, track irregularities, bridge girder cross-sections, and track settlements featuring a wide range of frequency contents were conducted. The performance of the proposed ATS+LQG delay compensation method was compared to the ATS method and RTHS without any compensation in terms of residual time delays and root mean square errors between commands and responses. The effectiveness of the ATS+LQG method to compensate time delay in RTHS with high-frequency responses was demonstrated and the proposed ATS+LQG method outperformed the ATS method in yielding more accurate responses with less residual time delays.

Key Words
ATS+LQG; high-frequency signals; RTHS; time delay compensation; train-bridge coupling system

Address
Hui M. Zhou: Engineering Seismic Research Center of Guangzhou University, 230 Waihuan west Road, Guangzhou, 510006, China; Institute of Engineering Mechanics, China Earthquake Administration, 29 Xuefu Road, Nangang District, Harbin, 150080, China
Bo Zhang: Institute of Engineering Mechanics, China Earthquake Administration, 29 Xuefu Road, Nangang District, Harbin, 150080, China
Xiao Y. Shao: Western Michigan University, 1903 W Michigan Ave.,Kalamazoo, MI, 49008, USA
Ying P. Tian: Institute of Engineering Mechanics, China Earthquake Administration, 29 Xuefu Road, Nangang District, Harbin, 150080, China
Wei Guo: Central South University, 932 Lushan South Road, Yuelu District, Changsha, 410075, China
Quan Gu: Xiamen University, 422 Siming South Road, Siming District, Xiamen, 361005, China
Tao Wang: Institute of Engineering Mechanics, China Earthquake Administration, 29 Xuefu Road, Nangang District, Harbin, 150080, China

Abstract
Twelve push-out test specimens were conducted with various parameters to study the static and fatigue performance of a new through-bolt shear connector transferring the shear forces of interface between prefabricated hybrid fiber reinforced concrete (HFRC) slabs and steel girders. It was found that the fibers could improve the fatigue life, capacity and initial stiffness of through-bolt shear connector. While the bolt-hole clearance reduced, the initial stiffness, capacity and slippage of through-bolt shear connector increased. After the steel-concrete interface properties were improved, the initial stiffness increased, and the capacity and slippage reduced. Base on the test results, the equation of the load-slip curve and capacity of through-bolt shear connector with prefabricated HFRC slab were obtained by the regression of test results, and the allowable range of shear force under fatigue load was recommended, which could provide the reference in the design of through-bolt shear connector with prefabricated HFRC slabs.

Key Words
capacity; fatigue life; HFRC; load-slip curve; through-bolt shear connector

Address
Yuliang He, Jie Zhuang, Lipu Hu: College of Civil Engineering, Shaoxing University, Shaoxing 312000, China
Fuyou Li: Hua Hui Group, Shaoxing, 312000, China
Ying Yang: College of Civil Engineering, Shaoxing University, Shaoxing 312000, China
Yi-qiang Xiang: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China

Abstract
The stability of cable-stayed bridges is an important factor considered during design. In recent years, the novel spatial diamond-shaped bridge pylon has shown its advantages in various aspects, including the static response and the stability performance with the development of cable-stayed bridge towards long-span and heavy-load. Based on the energy approach, this paper presents a practical calculation method of the completed state stability of a cable-stayed bridge with two spatial diamond-shaped pylons. In the analysis, the possible transverse buckling of the girder, the top pylon column, and the mid pylon columns are considered simultaneously. The total potential energy of the spatial diamond-shaped pylon cable-stayed bridge is calculated. And based on the principle of stationary potential energy, the transverse buckling coefficients and corresponding buckling modes are obtained. Furthermore, an example is calculated using the design parameters of the Changtai Yangtze River Bridge, a 1176 m cable-stayed bridge under construction in China, to verify the effectiveness and accuracy of the proposed method in practical engineering. The critical loads and the buckling modes derived by the proposed method are in good agreement with the results of the finite element method. Finally, cable-stayed bridges varying pylon and girder stiffness ratios and pylon geometric dimensions are calculated to discuss the applicability and advantages of the proposed method. And a further discussion on the degrees of the polynomial functions when assuming buckling modes are presented.

Key Words
buckling analysis; cable-stayed bridge; energy approach; spatial diamond-shaped pylon

Address
Xing Zheng, Qiao Huang: School of Transportation, Southeast University, 2 Southeast University Road, Jiangning District, Nanjing, Jiangsu Province, China
Qing-gang Zheng: China Railway Major Bridge Reconnaissance & Design Institute Co. Ltd., 8 Boxue Road, Economic and Technological Development Zone, Wuhan, Hubei Province, China
Zhen Li: Jiangsu Province Transportation Engineering Construction Bureau, 69 Shigu Road, Qinhuai District, Nanjing, Jiangsu Province, China


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