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CONTENTS
Volume 31, Number 4, October 2026
 

Abstract
A conventional pile-deck structure is a prefabricated structural system composed of precast reinforced concrete decks and prestressed high-strength pipe piles connected through rigid joints. Owing to its advantages of high component standardization, rapid construction, and efficient land use, this type of structure has become an important alternative for highway widening projects under stringent land-use constraints. However, conventional pile-deck structures generally adopt monolithic rigid connections, through which the inertial force of the deck is mainly transferred to the pile foundation via the pile head during earthquakes, often resulting in stress concentration in the piles and an increased risk of structural damage. To address this issue, this study proposes a novel seismic resistant system incorporating prestressed tendons through pile-deck connections. Finite element models of the structures are established in OpenSees to conduct nonlinear dynamic time-history analyses and seismic fragility assessment. The results indicate that the prestressed tendons can effectively share the deck inertial force and significantly reduce the curvature demands of both above- and under-ground pile segments. Compared with the prototype structure, the peak pile curvature and peak deck displacement of the proposed structure are reduced by 45.2% and 48.0%, respectively. The probabilities of the structural damage are also significantly decreased by incorporating the prestressed tendon connection.

Key Words
prestressed tendon connection; road pile-deck structure; seismic fragility analysis; seismic performance

Address
College of Civil Engineering, Hefei University of Technology, Hefei, China

Abstract
Soft-story reinforced concrete (RC) buildings in Mexico City lakebed sites are vulnerable to narrow-band amplification and long shaking durations, which may trigger quasi-resonant response. This paper presents a seismic risk assessment of 4- and 8-story weak first-story RC frames equipped with Pressurized Sand Dampers (PSDs) and subjected to narrow-band ground motions. PSD behavior is modeled with a three-parameter Bouc-Wen formulation. Device intensity is defined by the ratio of peak damper force to tributary floor weight, Q/mg, so that device strength is expressed relative to the weight associated with the story where the damper is installed. The adopted values are Q/mg=0.15 and 0.30 for the 4-story frame, and Q/mg=0.50 and 0.70 for the 8-story frame, corresponding to lower and higher PSD cases, respectively. Two evaluations are conducted: (1) a direct record-to-record comparison using 12 site-compatible synthetic motions for a 250-year Life Safety target, plus one real record, all additionally scaled to a 20-year target, to compare median interstory drift ratio (IDR) and normalized story shear (V/W); and (2) a probabilistic risk assessment combining site-specific hazard with motion families representing subduction and intraslab sources. Performance is quantified through drift exceedance rates and summarized as mean return periods. At an IDR threshold of 1.5%, PSDs increase the mean return period from 36 to 42-48 years in the 4-story frame and from 33 to 43-47 years in the 8-story frame. These results indicate that PSDs provide meaningful reductions in drift exceedance frequency under narrow-band excitation. In addition, PSD performance is benchmarked against conventional commercial devices, including Buckling-Restrained Braces (BRBs) and Viscous Dampers (VDs). Although their effectiveness remains lower than that of conventional devices, results highlight the potential of PSDs as a supplemental damping alternative and identify current limitations relative to established retrofit technologies.

Key Words
buckling-restrained braces; Mexico City lakebed; pressurized sand damper; probabilistic performance assessment; reinforced concrete frames with weak first-story; seismic risk assessment; viscous dampers

Address
Institute of Engineering, National Autonomous University of Mexico (UNAM), Mexico City, Mexico

Abstract
This study develops a nonlinear finite-element framework in OpenSees to investigate the influence of concrete confinement models on the seismic-progressive collapse behaviour of reinforced concrete (RC) moment-resisting frames subjected to earthquake excitation and sudden column removal. Five widely used confinement formulations, namely the Unconfined, Mander et al., Attard & Setunge, Samani & Attard, and Cusson & Paultre models, are implemented within a unified fiber-based modelling framework incorporating geometric nonlinearity and large-deformation effects. The framework is validated against experimental benchmark studies and subsequently applied to a ten-story RC frame. The results show that the influence of confinement is limited during the early stages of response but becomes increasingly important as deformation demands increase following column removal. While all confinement models produce similar global responses during seismic excitation, noticeable differences are observed in beam deformation, axial-force development, and post-removal force redistribution. The results indicate that the primary influence of confinement is associated with axial-force transfer and large-deformation mechanisms rather than with flexural or shear demand. Beam axial force and vertical deflection exhibit the highest sensitivity to the adopted confinement formulation, whereas global response measures such as roof displacement remain comparatively insensitive. The findings demonstrate that the selection of a confinement model can influence the predicted post-removal response, force redistribution, and robustness assessment of RC frames. The proposed framework provides a practical tool for evaluating confinement effects under combined seismic and progressive-collapse loading conditions and contributes to a better understanding of the role of confined concrete in robustness-oriented structural assessment.

Key Words
catenary action; concrete confinement; large deformation behavior; nonlinear dynamic analysis; OpenSees; progressive collapse; RC structures

Address
1) Institute of Research and Development, Duy Tan University, Da Nang, 550000, Vietnam; 2) Faculty of Civil Engineering, Duy Tan University, Da Nang, 550000, Vietnam

Abstract
This study investigates the influence of deformation-control components (DCCs) on seismic response uncertainty in stochastic frame structures. Five-, ten-, and fifteen-story moment-resisting frames equipped with pin-supported walls (PWs) were designed in accordance with seismic design codes. Stochastic finite element (FE) models incorporating structural randomness were established using Latin Hypercube Sampling (LHS). Stochastic static pushover analyses and nonlinear time-history analyses were conducted to evaluate the propagation of parameter uncertainty into load-bearing and deformation responses. Incremental dynamic analysis (IDA) was further employed to examine the impact of structural randomness on seismic fragility. A parametric investigation was conducted to establish the relationship between PW stiffness and deformation uncertainty. Results demonstrate that uncertainty in seismic response increases significantly after structural yielding. The introduction of PWs effectively reduces deformation-related uncertainty without markedly affecting uncertainty in load-bearing response. Although structural randomness increases seismic fragility, PWs can mitigate this effect. Compared with deterministic designs, stochastic frames require higher PW stiffness; accordingly, a probabilistic stiffness demand model incorporating structural randomness is proposed. The influence of structural randomness on deformation uncertainty is smaller than that caused by ground motion randomness. The proposed framework provides a probabilistic basis for improving seismic reliability through the design of deformation-control components and offers insights into the reliability-based design of such systems.

Key Words
deformation-control components; frame-pin-supported wall structure; incremental dynamic analysis; nonlinear time-history analysis; pushover analysis; seismic response uncertainty; stochastic finite element model

Address
Chunyang Zhu, Jingyu Hou, Li Sun, Chuang Li: Department of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China
Chunwei Zhang: Multidisciplinary Center for Infrastructure Engineering, Shenyang University of Technology, Shenyang 110870, China

Abstract
This article proposes an adaptation of macro-element model for infilled masonry reinforced concrete (RC) frame structures with tapered beam-column joints. To improve this approach, a geometry adjustment, a recalibration of the stress distribution using correction factors and non-linear spring properties were implemented. These adjustments provide better representation and a more realistic simulation of stiffness and confinement effects. Numerical validation performed based on cyclic test results, shows a significant improvement of tapered beam-column joints in seismic performance. Lateral resistance and stiffness were increased compared with bare frames. Tapered joints increase the effective diagonal strut width which promote uniform crack propagation and contribute to more ductile failure mechanisms. This model shows good agreement with experimental results and serves as an effective tool for optimizing design and retrofit in seismic areas for masonry infilled reinforced concrete structures.

Key Words
diagonal strut; macro element ; masonry infilled reinforced concrete frame structure; tapered joints

Address
Department of Civil Engineering, Centre National de Recherche Appliquée en Génie Parasismique CGS, 01 Rue Kaddour RAHIM, BP 252, Hussein Dey, Algiers, Algeria

Abstract
An extra-high voltage (EHV) substation is a complex system composed of various types of interconnected electrical equipment. As a critical node in the power grid, damage to such a substation during an earthquake can cause large-scale power outages and hinder post-earthquake rescue efforts. However, previous research has predominantly focused on the seismic performance of low-voltage substations, while studies addressing EHV substations employing 3/2-connection remain limited. To assess the seismic fragility and risk of EHV substations, this study proposes a bottom-up analysis method. At the equipment level, a multidimensional seismic fragility analysis method based on the maximum entropy principle is introduced to account for multidimensional correlations among key vulnerable parameters and the uncertainty of seismic excitations. The EHV substation is divided into nine subsystems, and the network topology of each subsystem is established according to the connection scheme. By integrating equipment fragility surfaces with fault-tree analysis, the probabilities of different post-earthquake functional-loss states are determined, and the seismic fragility of the entire substation is obtained considering the series-parallel relationships among the subsystems. For three representative types of equipment, the relative differences in extensive-damage probability between the maximum entropy and lognormal models are 12.42%, 22.35%, and 45.14% at PGA=0.40 g and Sa(T1)=0.80 g. At the station level, incorporating Sa(T1) in addition to PGA increases the cross-validated ROC AUC from 0.715-0.722 to 0.901-0.955 and reduces the Brier score by 36.4%-60.4%. Finally, the system fragility surface is integrated with the bivariate seismic hazard to evaluate the probabilistic risk of functional loss over different design reference periods. The proposed framework provides a quantitative basis for topology-informed seismic fragility assessment and risk-informed seismic design of 3/2-connected EHV substations.

Key Words
3/2-connection; EHV substation system; fault tree analysis; multidimensional correlation; probabilistic seismic risk; seismic fragility

Address
Economic and Technological Research Institute, State Grid Jibei Electric Power Co., Ltd., No. 1 Building, Xianglong Tower Compound, No. 311 Guang

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