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CONTENTS
Volume 26, Number 3, March 2024
 

Abstract
Aiming at studying the plastic hinge (PH) evolution regularities and failure mode of rocking wall moment frame (RWMF) structure in earthquakes, the whole-working history analysis of seismic performance state of RWMF structure based on co-operation performance and PH evolution was carried out. Building upon the theoretical analysis of the elastic internal forces and deformations of RWMF structures, nonlinear finite element analysis (FEA) methods were employed to perform both Pushover analysis and seismic response time history analysis under different seismic coefficients (delta). The relationships among PH occurrence ratios (Rph), inter-story drifts and delta were established. Based on the plotted curve of the seismic performance states, evaluation limits for the Rph and inter-story drifts were provided for different performance states of RWMF structures. The results indicate that the Rph of RWMF structures exhibits a nonlinear evolution trend of "fast at first, then slow" with the increasing of delta. The general pattern is characterized by the initial development of beam hinges in the middle stories, followed by the development towards the top and bottom stories until the beam hinges are fully formed. Subsequently, the development of column hinges shifts from the bottom and top stories towards the middle stories of the structure, ultimately leading to the loss of seismic lateral capacity with a failure mode of partial beam yield, demonstrating a global yielding pattern. Moreover, the limits for the Rph and inter-story drifts effectively evaluate the five different performance states of RWMF structures.

Key Words
co-operation performance; failure mode; plastic hinge (PH) evolution; plastic hinge occurrence ratios (Rph); rocking wall moment frame (RWMF) structures; seismic performance state

Address
Xing Su and Shi Yan: School of Civil Engineering, Shenyang Jianzhu University, 25 Hunnan M. Road, Hunnan District, China
Tao Wang: Qingdao Country Garden Bolin Real Estate Co., Ltd., Yunzhu Apartment, Nanning Road, Shibei District, China
Yuefeng Gao: Yantai Zhifu District Comprehensive Administrative Law Enforcement Bureau, 40 Airport Road, Zhifu District, China

Abstract
A comprehensive probabilistic seismic hazard analysis was carried out in Istanbul to examine the seismotectonic features of the region. The results showed that earthquakes can trigger one another, resulting in the grouping of earthquakes in both time and space. The hazard analysis utilized the Poisson model and a conventional integration technique to generate the hazard curve, which shows the likelihood of ground motion surpassing specific values over a given period. Additionally, the study evaluated the impact of seismic hazard on the structural integrity of an existing masonry tower by simulating its seismic response under different ground motion intensities. The study's results emphasize the importance of considering the seismotectonic characteristics of an area when assessing seismic hazard and the structural performance of buildings in seismicprone regions.

Key Words
discrete element modeling; probabilistic approach; seismic hazard; seismic risk analysis

Address
Civil Engineering Department, Yeditepe University, İstanbul, Turkey

Abstract
Beam-column joints in the frame structure are at high risk of brittle shear failure which would lead to significant residual deformation and even the collapse of the structure during an earthquake. In order to improve the damage issue and enhance the recoverability of the beam-column joints, a sector lead rubber damper (SLRD) has been developed. The SLRD can increase the bearing capacity and energy dissipation capacity, and also demonstrating recoverability of seismic performance following cyclic loading. In this paper, the hysteretic behavior of SLRD was experimentally investigated in terms of the regular hysteretic behavior, large deformation behavior and fatigue behavior. Furthermore, a parametric analysis was performed to study the influence of the primary design parameters on the hysteretic behavior of SLRD. The results show that SLRD resist the exerted loading through the shear capacity of both rubber parts coupled with the lead cores in the pre-yielding stage of lead cores. In the post-yielding phase, it is only the rubber parts of the SLRD that provide the shear capacity while the lead cores primarily dissipate the energy through shear deformation. The SLRD possesses a robust capacity for large deformation and can sustain hysteretic behavior when subjected to a loading rotation angle of 1/7 (equivalent to 200% shear strain of the rubber component). Furthermore, it demonstrates excellent fatigue resistance, with a degradation of critical behavior indices by no more than 15% in comparison to initial values even after 30 cycles. As for the designing practice of SLRD, it is recommended to adopt the double lead core scheme, along with a rubber material having the lowest possible shear modulus while meeting the desired bearing capacity and a thickness ratio of 0.4 to 0.5 for the thin steel plate.

Key Words
haunch brace; hysteretic behavior; large deformation; parametric analysis; sector lead rubber damper

Address
Xin Xu, Yun Zhou, Zhang Yan Chen and Song Wang: School of Civil Engineering, Guangzhou University, Waihuan Xi Road 230, Panyu District, Guangzhou, China
Ke Jiang: Department of Civil and Natural Resources Engineering, University of Canterbury, Christchurch, New Zealand

Abstract
This study examines damping modification factors (DMFs) of elastic input energy spectra corresponding to a set of 116 earthquake ground motions. Mean input energy per mass spectra and mean DMFs are presented for both considered ground motion components. Damping ratios of 3%, 5%, 10%, 20%, and 30% are used and the 5% damping ratio is considered the benchmark for DMF computations. The geometric mean DMFs of the two horizontal components of each ground motion are computed and coefficients of variation are presented graphically. The results show that the input energy spectra-based DMFs exhibit a dependence on the damping ratio at very short periods and they tend to be nearly constant for larger periods. In addition, mean DMF variation is obtained graphically for also the damping ratio, and mathematical functions are fitted as a result of statistical analyses. A strong correlation between the computed DMFs and the ones from predicted equations is observed.

Key Words
damping modification factor; damping ratio; earthquake ground motion; elastic input energy spectra; singledegree- of-freedom-system

Address
Onur Merter: Department of Civil Engineering, Izmir University of Economics, 35330, Balcova, Izmir, Turkey
Taner Ucar: Department of Architecture, Dokuz Eylul University, 35390, Buca, Izmir, Turkey

Abstract
This paper studied the subgrade spring stiffness and its influencing factors in the seismic deformation method of circular tunnel. Numerical calculations are performed for 3 influencing factors: stratum stiffness, tunnel diameter and burial depth. The results show that the stratum stiffness and tunnel diameter have great influence on the subgrade spring stiffness. The subgrade spring stiffness increases linearly with stratum stiffness increasement, and decreases with the tunnel diameter increasement. When the burial depth ratio (burial depth/tunnel diameter) exceeds to 5, the subgrade spring stiffness has little sensitivity to the burial depth. Then, a proposed formula of subgrade spring stiffness for the seismic deformation method of circular tunnel is proposed. Meanwhile, the internal force results of the seismic deformation method are larger than that of the dynamic time history method, but the internal force distributions of the two methods are consistent, that is, the structure exhibits elliptical deformation with the largest internal force at the conjugate 45o position of the circular tunnel. Therefore, the seismic deformation method based on the proposed formula can effectively reflect the deformation and internal force characteristics of the tunnel and has good applicability in engineering practice.

Key Words
circular tunnel; seismic deformation method; sensitive factor analysis; subgrade spring stiffness

Address
Xiangyu Guo: College of Civil Engineering, Huaqiao University, Xiamen 361021, Fujian, China
Liangjie Wang: POWERCHINA Chengdu Engineering Corporation Limited, Chengdu 611130, Sichuan, China
Jun Wang and Junji An: Sichuan Highway Planning, Survey, Design and Research Institute Ltd, Chengdu 610041, Sichuan, China

Abstract
A new layered shear continuum model box was developed to address the dynamic response issues of buried oil and gas pipelines under multi-point excitation. Vibration table tests were conducted to investigate the seismic response of buried pipelines and the surrounding soil under longitudinal multi-point excitation. A nonlinear model of the pipeline-soil interaction was established using ABAQUS finite element software for simulation and analysis. The seismic response characteristics of the pipeline and soil under longitudinal multi-point excitation were clarified through vibration table tests and simulation. The results showed good consistency between the simulation and tests. The acceleration of the soil and pipeline exhibited amplification effects at loading levels of 0.1 g and 0.2 g, which significantly reduced at loading levels of 0.4 g and 0.62 g. The peak acceleration increased with increasing loading levels, and the peak frequency was in the low-frequency range of 0 Hz to 10 Hz. The amplitude in the frequency range of 10 Hz to 50 Hz showed a significant decreasing trend. The displacement peak curve of the soil increased with the loading level, and the nonlinearity of the soil resulted in a slower growth rate of displacement. The strain curve of the pipeline exhibited a parabolic shape, with the strain in the middle of the pipeline about 3 to 3.5 times larger than that on both sides. This study provides an effective theoretical basis and test basis for improving the seismic resistance of buried oil and gas pipelines.

Key Words
buried piping; longitudinal multi-point excitation; numerical simulation; seismic response; vibration table test

Address
Jianbo Dai: School of Civil Engineering, Xi'an Shiyou University, Xi'an 710065, China
Zewen Zhao, Jing Ma, Zhaocheng Wang and Xiangxiang Ma: School of Mechanical Engineering, Xi'an Shiyou University, Xi'an 710065, China

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