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CONTENTS
Volume 21, Number 6, December 2021
 


Abstract
The rocking foundation is effective for reducing structural seismic demand and avoiding overdesign of the foundation. It is crucial to evaluate the performance of rocking foundations because they cause plastic hinging in the soil. In this study, to derive optimized ground motion intensity measures (IMs) for rocking foundations, the efficiency of IMs correlated with engineering demand parameters (EDPs) was estimated through the coefficient determination using a physical modeling database for rocking shallow foundations. Foundation deformations, the structural horizontal drift ratio, and contribution in drift from foundation rotation and sliding were selected as crucial EDPs for the evaluation of rocking foundation systems. Among 15 different IMs, the peak ground velocity exhibited the most efficient parameters correlated with the EDPs, and it was discovered to be an efficient ground motion IM for predicting the seismic performance of rocking foundations. For vector regression, which uses two IMs to present the EDPs, the IMs indicating time features improved the efficiency of the regression curves, but the correlation was poor when these are used independently. Moreover, the ratio of the column-hinging base shear coefficient to the rocking base shear coefficient showed obvious trends for the accurate assessment of the seismic performance of rocking foundation-structure systems.

Key Words
controlling rocking parameter; database of rocking shallow foundation; dynamic centrifuge test; ground motion intensity measures; rocking foundation; soil-foundation-structure interaction

Address
Kil-Wan Ko: Department of Civil and Environmental Engineering, University of California, Berkeley, 760 Davis Hall, Berkeley, California, CA 94720, U.S.A.

Jeong-Gon Ha: Advanced Structures and Seismic Safety Research Divison, Korea Atomic Energy Research Institute,
111 Daedeok-Daero 989 beon-gil, Yuseong-gu, Daejeon 305-701, Republic of Korea

Abstract
In this research, a neural network (NN) method was developed, which combines H-infinity and fuzzy control for the purpose of stabilization and stability analysis of nonlinear systems. The H-infinity criterion is derived from the Lyapunov fuzzy method, and it is defined as a fuzzy combination of quadratic Lyapunov functions. Based on the stability criterion, the nonlinear system is guaranteed to be stable, so it is transformed to be a linear matrix inequality (LMI) problem. Since the demo active vibration control system to the tuning of the algorithm sequence developed a controller in a manner, it could effectively improve the control performance, by reducing the wind's excitation configuration in response to increase in the cost efficiency, and the control actuator.

Key Words
fuzzy Lyapunov method; tall building, fuzzy control; tuned mass damper

Address
Z.Y. Chen: Guangdong University of Petrochem Technology, School of Science, Maoming 525000, PR China

Ruei-Yuan Wang: Guangdong University of Petrochem Technology, School of Science, Maoming 525000, PR China

Rong Jiang: Guangdong University of Petrochem Technology, School of Science, Maoming 525000, PR China

Timothy Chen: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, U.S.A.

Abstract
The modified-ECOMAC approach to monitor and investigate health of structure in marine platforms was evaluated in this research. The material properties of structure were defined based on the real platform located in Persian Gulf. The nonlinear time-history analyses were undertaken using the marine natural waves. The modified- ECOMAC approach was designed to act as the solution of the best sensor placement according to structural dynamic behavior of structure. This novel method uses nonlinear time-history analysis results as an exact seismic response despite the common COMAC algorithms utilize the eigenvalue responses. The processes of modified-ECOMAC criteria were designed and developed by author of this paper as a toolbox of Matlab. The Results show that utilizing an efficient ECOMAC method in SHM process leads to detecting the critical weak points of sensitive marine platforms to make better decision about them. The statistical results indicate that considering modified ECOMAC based on seismic waves analysis has an acceptable accuracy on identify the sensor location. The average of statistical comparison of COMAC and ECOMAC via modal and integrated analysis, had a high MAE of 0.052 and RSME of 0.057 and small R2 of 0.504, so there is significant difference between them.

Key Words
COMAC; ECOMAC; offshore platform; OSP

Address
Hamidreza Vosoughifar: Department of Civil Engineering, Islamic Azad University, Tehran South Branch, 1777613651, Tehran, Iran
Department of Civil and Environment Engineering, Hawaii University at Mano, Hawaii, 96822, USA

Ali Yaghoubi: Department of Civil Engineering, Islamic Azad University, Tehran South Branch, 1777613651, Tehran, Iran

Milad Khorani: Department of Civil Engineering, Islamic Azad University, Tehran South Branch, 1777613651, Tehran, Iran

Pooya Biranvand: Department of Civil Engineering, Islamic Azad University, Tehran South Branch, 1777613651, Tehran, Iran

Seyedehzeinab Hosseininejad:Department of Civil Engineering, Islamic Azad University, Tehran South Branch, 1777613651, Tehran, Iran

Abstract
The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

Key Words
accelerogram; Arias Intensity; dynamics; Newmark

Address
Aleksandra Korzec: Institute of Hydro-Engineering, Polish Academy of Sciences, ul. Kościerska 7, 80-328 Gdańsk, Poland

Robert Jankowski: Faculty of Civil and Environmental Engineering, Gdańsk University of Technology, ul. Narutowicza 11/12, 80-233 Gdańsk, Poland

Abstract
Non-seismically designed eccentric reinforced concrete beam-column joints were extensively used in existing reinforced concrete frame buildings, which were found to be vulnerable to seismic action in many incidences. To provide a fundamental understanding of the seismic performance and failure mechanism of the joints, three 2/3-scale exterior beam-column joints with non-seismically designed details were cast and tested under reversed cyclic loads simulating earthquake excitation. In this investigation, particular emphasis was given on the effects of the eccentricity between the centerlines of the beam and the column. It is shown that the eccentricity had significant effects on the damage characteristics, shear strength, and displacement ductility of the specimens. In addition, shear deformation and the strain of joint hoops were found to concentrate on the eccentric face of the joint. The results demonstrated that the specimen with an eccentricity of 1/4 column width failed in a brittle manner with premature joint shear failure, while the other specimens with less or no eccentricity failed in a ductile manner with joint shear failure after beam flexural yielding. Test results are compared with those predicted by three seismic design codes and two non-seismic design codes. In general, the codes do not accurately predict the shear strength of the eccentric joints with non-seismic details.

Key Words
beam-column joint; design codes; eccentricity; seismic behavior; shear strength

Address
Ying Liu: Faculty of Science and Technology, Technological and Higher Education Institute of Hong Kong, Hong Kong, China

Simon H.F. Wong: Faculty of Science and Technology, Technological and Higher Education Institute of Hong Kong, Hong Kong, China

Hexin Zhang: School of Engineering and The Built Environment, Edinburgh Napier University Edinburgh, City of Edinburgh, UK

J.S. Kuang: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, China

Pokman Lee: Faculty of Science and Technology, Technological and Higher Education Institute of Hong Kong, Hong Kong, China

Winghei Kwong: Faculty of Science and Technology, Technological and Higher Education Institute of Hong Kong, Hong Kong, China

Abstract
Fragility curves are being more significant as a useful tool for evaluating the relationship between the earthquake intensity measure and the effects of the engineering demand parameter on the buildings. In this paper, the effect of different site conditions on the vulnerability of the structures was examined through the fragility curves taking into account different strength capacities of the precast columns. Thus, typical existing single-story precast RC industrial buildings which were built in Turkey after the year 2000 were examined. The fragility curves for the three typical existing industrial structures were derived from an analytical approach by performing non-linear dynamic analyses considering three different soil conditions. The Park and Ang damage index was used in order to determine the damage level of the members. The spectral acceleration (Sa) was used as the ground motion parameter in the fragility curves. The results indicate that the fragility curves were derived for the structures vary depending on the site conditions. The damage probability of exceedance values increased from stiff site to soft site for any Sa value. This difference increases in long period in examined buildings. In addition, earthquake demand values were calculated by considering the buildings and site conditions, and the effect of the site class on the building damage was evaluated by considering the Mean Damage Ratio parameter (MDR). Achieving fragility curves and MDR curves as a function of spectral acceleration enables a quick and practical risk assessment in existing buildings.

Key Words
damage index; incremental dynamic analysis; mean damage ratio; seismic vulnerability

Address
Ali Yesilyurt: Department of Civil Engineering, Gebze Technical University, 41400 Gebze, Kocaeli, Turkey

Abdullah C. Zulfikar: Department of Civil Engineering, Gebze Technical University, 41400 Gebze, Kocaeli, Turkey

Cuneyt Tuzun: Department of Civil Engineering, Gebze Technical University, 41400 Gebze, Kocaeli, Turkey

Abstract
Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. In this study, a new type of digging well foundation with prefabricated roots was proposed to reduce earthquake damage of these bridges. Quasi-static tests were conducted to investigate the failure mechanism of the root digging well foundation, and then to analyze seismic behaviors of the new type well foundation. The testing results indicated that these prefabricated roots could effectively limit the rotation and uplift of the digging well foundation and increase the lateral bearing capacity of the digging well foundation. The elastic critical load and ultimate load can be increased by 69% and 36% if prefabricated roots were added in the digging well foundation. The prefabricated roots drived more soil around the foundation to participate in working, the stiffness of the bridge pier with root digging well foundation was improved. Moreover, the root participation could improve the energy dissipation capacity of soil-foundation-pier interaction system. The conclusions obtained in this paper had important guiding significance for the popularization and application of the digging well foundation with prefabricated roots in earthquake-prone zones.

Key Words
digging well foundation; experimental study; prefabricated root; railway bridge; seismic behavior

Address
Yi Wang: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Xingchong Chen: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Xiyin Zhang: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Mingbo Ding: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Jianqiang Gao: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Jinhua Lu: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Yongliang Zhang: School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China

Abstract
In this study, cyclic loading tests were conducted on the precast concrete (PC) wide beam (WB)-column joints. Two beam-column joint specimens were fabricated with the arrangement and anchorage details of the reinforcing bars penetrating the beam and column as variables. Through a cyclic loading test, the lateral load-story drift ratio responses, seismic performance characteristics (e.g., ductility, overstrength factor), energy dissipation, strength and stiffness degradations of each specimen were compared and analyzed based on the various indices and the current structural codes (ACI 318-19 and ACI 374.1-05 report). In addition, the shear lag effect was confirmed through the gauge values of the PC beam, and the differences in seismic performance between the specimens were identified on that basis.

Key Words
beam-column joints; precast concrete; seismic performance; shear lag effect; wide beam

Address
Jae Hyun Kim: Department of Architectural Engineering, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea

Beom Soo Jang: Department of Structural Design, Dream Structural Engineering Co., 10 Dongtandae-ro 21-gil, Hwaseong-si, Gyeonggi-do 18471, Korea

Seung-Ho Choi: Department of Architectural Engineering, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea

Yoon Jung Lee: Department of Architectural Engineering and the Smart City Interdisciplinary Major Program, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea

Ho Seong Jeong: Department of Architectural Engineering and the Smart City Interdisciplinary Major Program, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea

Kang Su Kim: Department of Architectural Engineering and the Smart City Interdisciplinary Major Program, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea


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