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CONTENTS
Volume 28, Number 3, March 2025
 

Abstract
The present study considers a vertical irregularity generated by varying the angle of the slope of the ground surface. The influence of variation in the angle of the slope on the seismic response of structures has been investigated. The angles of the slope of the ground are taken as 0o, 15o, 30o and 45o respectively. Multistoreyed regular frames of six-storeys, eight-storeys, and ten-storeys are modified by introducing irregularities through a variable slope angle to generate a total of 12 configurations. A numerical procedure has been employed to estimate the responses of the structures under earthquake loading conditions. The analysis of the structures has been performed using the response spectrum method and the nonlinear time history method. The behaviors of the structures are evaluated in terms of the natural periods, drift ratio, and base shear. Fragility curves are plotted to investigate the vulnerability of structures with different slopes. The irregularities are found to influence the behavior of the structures considerably. The results obtained illustrate the criticality associated with the variation of the slope angle on the seismic response of the structure and would serve as an aid in designing irregular structures without compromising performance.

Key Words
nonlinear time history method; response spectrum method; seismic response; sloping ground surface; vertically irregular structures

Address
Sumit Kumar: Department of Civil Engineering, Government Engineering College, Palamu, Jharkhand, 822118, India
Uttam Kumar: Department of Civil Engineering, Birsa Institute of Technology Sindri, Jharkhand, 828123, India
Sekhar Chandra Dutta and Pranoy Debnath: Department of Civil Engineering, Indian Institute of Technology (ISM) Dhanbad, Jharkhand, 826004, India

Abstract
With a focus on the dynamic characteristics of the ground motion recorded in Kahramanmaraş, Türkiye, this study provides an overview of the historical seismicity of the Eastern Anatolian Fault Zone (EAFZ) as well as the characteristics of the Pazarcik and Elbistan earthquakes (Mw=7.7 and Mw=7.6) that resulted in property loss and casualties on February 6, 2023. Analyzing the ground motion and local site effects for the earthquake region has been the subject of extensive research in the past. Ground Motion Prediction Equations (GMPEs) are one of the evaluation techniques utilised in the literature. Previous research employing this approach and other techniques suggested that the earthquake region's geotechnical and seismological conditions are complicated, particularly in Hatay City. In this study, to further investigate the ground motions, six GMPEs, which were previously proposed for the USA, Europe and the Middle East, are adopted. The findings of this study are integrated with those from previous research for comprehensive assessments. This study shows that the PGA of the Kahramanmaraş earthquakes cannot be fully predicted using GMPEs, which use epicentral distance (Repi) in the equation. As a result, further research into rupture distance (Rrup) or Joyner-Boore distance (Rjb)-based equations is necessary. Also, the complexity of the region (i.e., irregularities present in alluvial deposits) and the high PGA values could be responsible for such a result. This study emphasizes the region's need to have more sophisticated GMPEs in the future.

Key Words
2023 Türkiye earthquakes; epicentral distance; ground motion prediction equations; the seismicity of EAFZ

Address
Adnan Kiral and Zeliha Tonyali: Department of Civil Engineering, Faculty of Engineering and Architecture, Recep Tayyip Erdogan University, Rize, 53100, Türkiye
Mustafa Ergun: Department of Civil Engineering, Faculty of Engineering, Bayburt University, Bayburt, 69000, Türkiye

Abstract
The study investigates the potential of a magnetorheological (MR) damper on a structure subjected to dynamic load following an in-depth analysis. This investigation aims to provide a feasible solution for vibration control of structures with MR dampers without the facility of a compatible control system. The study proposes the efficiency of a control mechanism of a horizontally placed MR damper on a frame without a build in controller. A hysteretic Bingham model of an MR damper is considered to show a linear relationship between current, voltage and damper restoring force. The experiments were conducted on a six degree of freedom shake table. Sinusoidal loads of different amplitudes were induced in both directions of the frame. Numerical simulations are carried out which supported the experimental observations effectively. The hysteretic model shows the robustness of the damper at various voltages and frequencies. The damper is optimum when placed at the top floor of the frame. The horizontal orientation of the damper is able to provide a steady decline in the vibration responses with the rise in its voltage for various amplitudes of applied loads in both directions of the frame. MR Damper is adeptly able to alleviate structural vibrations cardinally without the requirement of a compatible control system.

Key Words
hysteretic Bingham model; interstorey drift; MR damper; semi-active damper; shake table; state space model

Address
Payel Chaudhuri: Civil Engineering Department, Vignan's Foundation for Science, Technology & Research -522213, India
Damodar Maity and D. K. Maiti: Department of Civil Engineering, Indian Institute of Technology, Kharagapur -721302, India

Abstract
This study investigates vertical irregularities in structures with column discontinuities, a topic rarely examined in existing literature. The critical importance of this issue was highlighted by the Kahramanmaraş earthquakes, which exceeded expected maximum acceleration values in both horizontal and vertical components. In response, 80 Nonlinear Time History Analyses (NLTHAs) were conducted using acceleration records for ZD-type soil, considering near-fault effects (Mw>=7.0). Scenarios were analyzed both with and without vertical acceleration to assess the behavior of regular and irregular structures under design-level (DD2) and maximum-level (DD1) earthquakes. The results indicate significant changes in axial load-carrying capacity, especially in irregular structures, due to vertical accelerations. Notably, while using average responses from multiple earthquake records is a common practice, this approach may overlook critical structural vulnerabilities. Peak responses revealed that columns might be insufficiently designed if only average values are considered. Therefore, the study emphasizes the necessity of evaluating the variability in structural responses across different seismic scenarios rather than relying solely on average earthquake effects. This comprehensive approach ensures more accurate assessments of structural resilience, particularly for irregular structures subject to near-fault influences.

Key Words
column discontinuity; near fault; nonlinear analysis; vertical ground motion; vertical irregularity

Address
Department of Civil Engineering, Karabük University, 78050 Karabük, Turkey

Abstract
The present paper deals with the assessment of the structural behavior of conventionally designed reinforced concrete columns subjected to combined horizontal-vertical seismic excitation. The term "conventionally designed" designates structural members designed against the horizontal seismic component only. Apart from estimating critical response quantities, the paper identifies which specific design criteria are affected and which code requirements could be violated due to the vertical excitation action. For this purpose, a common reinforced concrete frame with four stories is designed in accordance with Eurocodes which permit to omit the vertical component. Subsequently, the seismic response of the columns for combined horizontal-vertical seismic excitation is evaluated by means of time-history analysis applying three recorded accelerograms. The whole investigation indicates that conventional columns detailed according to the current code provisions might violate fundamental design criteria in case of seismic excitation along horizontal and vertical directions concurrently. The main cause of this phenomenon is the normalized axial force fluctuation.

Key Words
non-linear behavior; planar frames; reinforced concrete columns; seismic design; time-history analysis; vertical ground motion

Address
Department of Civil Engineering, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Macedonia, Greece

Abstract
Rocking isolation is an effective method for reducing structural damage during earthquakes and aligns with a seismic design approach that aims to minimize damage to bridges. The seismic responses of rocking structures are significantly influenced by the soil-structure interaction and the soil characteristics. In this research, a shaking table test was conducted on a single-pier rigid-frame bridge model with an uplifting footing, considering soil-structure interaction. This test was used to validate a finite element model (FEM) developed using ABAQUS software. Subsequently, the seismic responses of the rigid-frame bridge with a pile foundation capable of rocking at the pier base were analyzed in detail. Four soil types, including silt, silt clay, sand, and clay, were examined, and two foundation types were considered: a fixed pile foundation and a rocking pile foundation. The results indicate that uplifting the footing can reduce the deck's acceleration and the pier's bending moment, while increasing the bridge's displacement, compared to a bridge with a fixed pile foundation.

Key Words
footing uplift; rigid frame bridge; rocking isolation; seismic response; soil-structure interaction

Address
Yang Lv, Jian Yang and Peixin Liu: Tianjin Key Laboratory of Civil Structure Protection and Reinforcement, Tianjin Chengjian University, Tianjin 300384, China
Fangfang Li: 1) Tianjin Key Laboratory of Civil Structure Protection and Reinforcement, Tianjin Chengjian University, Tianjin 300384, China, 2) School of Civil Engineering, Tianjin University, Tianjin 300072, China

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