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CONTENTS
Volume 25, Number 4, October 2023
 

Abstract
The use of displacement-dependent rotational friction dampers (RFD) as fuses or interchangeable elements in the moment-resisting frames (MRF) is one of the newest methods for improving seismic performance. In the present study, the performance of rotational friction dampers in MRF has been investigated. Evaluation of MRF with and without RFD models was performed using the finite element method by ABAQUS. For validation, an MRF and MRF with rotational friction dampers were modeled that had been experimentally tested and reported in previous experimental research and a good agreement was observed. The behavior of these dampers in frames of 3-, 6-, and 9-story was studied by modeling the damper directly. Nonlinear time history dynamic analysis was used. It was observed that by increasing the number of stories in the buildings, rotational friction dampers should be used to perform properly against earthquakes. The installation of rotational friction dampers in steel moment-resisting frames shows that the drift ratio between the floors is reduced and the seismic performance of these frames is improved.

Key Words
fuses; numerical method; performance level; rotational friction dampers (RFD); steel moment-resisting frames (MRF); time history analysis

Address
Ali Banazadeh and Ahmad Maleki: Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Mohammad Ali Lotfollahi Yaghin: Department of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract
Bingöl, a city in eastern Türkiye, is located at a very close distance to the Karliova Region which is a junction point of the North Anatolian Fault Zone and Eastern Anatolian Fault Zone. By bilateral step over of North Anatolian Fault Zone and Eastern Anatolian Fault Zone each other there occurred NorthWest-SouthEast extended right-lateral and NorthEast-SouthWest extended left-lateral fault zones. In this paper, a typical school building located in Bingöl Çeltiksuyu was selected as the case study. Information on the school building and Bingöl Earthquake (2003) have been given in the paper. This study aimed to determine the fragility curves of the school building according to HAZUS 2022, Turkish Seismic Codes 1998, 2007 and 2018. These codes have been introduced in terms of damage limits. Incremental dynamic analysis is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Fragility analysis is commonly using to estimate the damage probability of buildings. Incremental Dynamic Analysis have performed, and 1295 Incremental Dynamic Analysis output was evaluated to obtain fragility curves. 20 different ground motion records have been selected with magnitudes between 5.6M and 7.6M. Scaling factors of these ground motions were selected between 0.1g and 2g. Comparison has been made between HAZUS 2022 and Turkish Seismic Codes 1998, 2007 and 2018 in terms of damage states and how they affected fragility curves. TSC 1998 has more conservative strictions along with TSC 2018 than TSC2007 and HAZUS moderate and extensive damage limits.

Key Words
Bingöl 2003 earthquake; fragility curves; school building

Address
Department of Civil Engineering, Dicle University, Diyarbakir 21100, Türkiye

Abstract
Various methods for determining the damping ratio have been proposed by scholars both domestically and abroad. However, no comparative analysis of different determination methods has been seen yet. In this study, typical sand (Fujian standard sand) and cohesive soils were selected as experimental objects, and undrained strain-controlled dynamic triaxial tests were conducted. The differences between existing damping ratio determination methods were theoretically compared and analyzed. The results showed that the hysteresis curve of cohesive soils had better symmetry and more closely conformed to the definition of equivalent linear viscoelasticity. For non-cohesive soils, the differences in damping ratio determined by six methods were significant. The differences decreased with increasing confining pressure and relative density, but increased gradually with increasing shear strain, especially at high shear strains, where the maximum relative error reached 200%. For cohesive soils, the differences in damping ratio determined by six methods were relatively small, with a maximum relative error of about 50%. Moreover, they were less affected by effective confining pressure and had the same changing trend under different effective confining pressures. The damping ratio determination method has a large effect on the seismic response of soils distributed by non-cohesive soils, with a maximum relative error of about 15% for the PGA and up to about 30% for the Sa. However, for soil layers distributed by cohesive soils, the damping ratio determination method has less influence on the seismic response. Therefore, it is necessary to adopt a unified damping ratio determination method for non-cohesive soils, which can effectively avoid artificial errors caused by different determination methods.

Key Words
clay soil; cyclic triaxial tests; damping ratio; hysteresis curve; sandy soil; soil dynamics

Address
1) Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China
2) Institute of Geotechnical Engineering, Hebei University, Baoding, China

Abstract
This study investigates a rocking seismic isolation (RSI) system as a seismic protection measure against narrowband ground-motions generated by earthquakes. Structures supported over RSIs are considered capable of reducing the lateral demands and damage of the main structural system through lifting and rocking. This lifting and rocking during earthquake activity is provided by free-standing columns. A single-degree-of-freedom (SDOF) system supported on a RSI system is subjected to narrow-band seismic motions and its response is compared to an analog system without RSI. The comparison is then extended to reinforced concrete linear frames with and without RSI; three-bay frames with 11 and 17 storeys are considered. It is found that the RSI systems significantly reduce acceleration and displacement demands in the main structural frames, more noticeably if the first structural mode dominates the response and for ratios of the predominant frequency of the ground motion to the predominant frequency of the main frame near one. It is also found that the RSI system is more effective in reducing lateral accelerations and displacements of the main structure when the aspect ratio, b⁄h, and size, R, of the free-standing columns decrease, although the rocking stability of the RSI system is also reduced.

Key Words
displacement demand and acceleration demand; Mexico City; narrow-band earthquake loading; rocking seismic isolation system; structures

Address
Miguel A. Jaimes: Instituto de Ingeniería, UNAM, Av. Universidad, No. 3000, CP 04510, Del. Coyoacán, Ciudad de México, México
Salatiel Trejo and Valentín Juárez: Facultad de Ingeniería, UNAM, No. 3000, CP 04510, Del. Coyoacán, Ciudad de México, México
Adrián D. García-Soto: Departamento de Ingeniería Civil, Universidad de Guanajuato, Guanajuato, Guanajuato, México

Abstract
This paper presents experimental and numerical studies of seismic performance on reinforced concrete (RC) wide beam (WB) joints. Two RC-WB joint specimens and one conventional RC joint specimen were fabricated using the reinforcing details of longitudinal reinforcing bars in a beam as a variable, and quasi-static cyclic loading tests were performed. The results were used to compare and analyze the load-drift ratio relationship, failure mode, and seismic performance of the specimens quantitatively. In addition, a finite element (FE) analysis of the RC-WB joint was conducted, and the rationality of the FE model was validated by comparing it with the test results. Based on the FE model, a parametric study was conducted, where the ratio of longitudinal reinforcing bars placed on the outer and inner parts of the joint (pex⁄pin) was a key variable. The results showed that, in the RC-WB joint, an increase of pex⁄pin leads to more severe damage to concrete, which reduces the seismic performance of the RC-WB joints.

Key Words
exterior joint; quasi-static cyclic loading test; reinforced concrete; seismic performance; wide beam

Address
Jae Hyun Kim and Sun-Jin Han: Department of Architectural Engineering, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea
Seung-Ho Choi: Department of Fire and Disaster Prevention Engineering, University of Seoul, 163 Siripdae-ro, Dongdaemun-gu, Seoul 02504, Korea
Hoseong Jeong and 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
Jae-Yeon Lee: Department of Architecture, Mokwon University, 88 Doanbuk-ro, Seo-gu, Daejeon 35349, Korea

Abstract
The conventional method of structural seismic design was based on increasing structural capacity, which usually didn't reduce earthquake seismic effects. By changing the philosophy of structure design, technologies such as passive seismic control have been used in structures. So far, a large number of seismic isolation systems have been introduced to dissipate earthquake energy that is applied to a structure. These systems act against earthquakes rather than increasing the strength and capacity of the structure. In the present paper, a suspended column called a "pendulum column" is investigated, and a new idea has been considered to improve the performance of the pendulum column isolator by changing the gravity effect by adding a spring under the isolator system. The behavior of the studied isolator system has been researched. Then the isolator system was investigated under different earthquakes and compared with a common pendulum column isolator. The results show that changing the gravity effect has an effective role in the response of the system by reducing the system stiffness. Equations for the system showed that even in a special state, complete isolation is possible. Finally, the tested model verified the theory.

Key Words
damping; earthquake; effective gravity; isolator; pendulum column

Address
Department of Structural engineering, University of Tabriz, 29 Bahman Boulevard, Tabriz, I.R. of Iran

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