Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as...

acc
 
CONTENTS
Volume 21, Number 1, January 2026
 

Abstract
This study performed a comparative probabilistic fragility analysis of an integral abutment bridge (IAB) in liquefied and non-liquefied soil, evaluating its seismic vulnerability to near-fault and far-fault ground motions (GMs) sources. Utilizing the OpenSees platform, incorporated p-y springs with PyLiq1 material to model the effects of soil liquefaction. A threedimensional IAB model with a single span was developed, focusing on the susceptibility of the bridge's piles and abutments to ground vibrations. The analysis involved constructing a probabilistic seismic demand model through nonlinear time history analysis, utilizing 200 scaled earthquake sets. Fragility curves were employed to calculate the conditional probability of specific structural demands exceeding the structural capacity, with peak ground acceleration as a key parameter. The analysis results of fragility curves revealed that liquefaction had a dual impact on the seismic response of the IAB piles and abutment damage states. Liquefaction around the piles increased the probability of pile damage from slight to collapse and increased the potential for abutment collapse, while less susceptibility to abutment damage ranged from slight to extensive compared to non-liquefied soil. When considering near-fault GM in non-liquefied soil, the IAB abutment damage states increased by 2% compared to farfault GM, while the IAB pile damage states under near-fault GM in liquefied soil decreased by 2%.

Key Words
damage states; fragility curve; liquefied soil; near-fault and far-fault

Address
(1) Qiuhong Zhao, Abdul Hakim Hotak, Kui Gui, Bashir Ahmad Rasheedy:
School of Civil Engineering, Tianjin University, Tianjin, 300350, China;
(2) Qiuhong Zhao:
Tianjin Key Laboratory of Civil Structure Protection and Reinforcement, Tianjin Chengjian University, Tianjin, 300192, China;
(3) Abdul Hakim Hotak, Mohammad Nasir Wahdat:
Department of Civil Engineering, Faculty of Engineering, Laghman University, Mehtarlam 270101, Afghanistan.

Abstract
In the study, the problem of discontinuous contact in two layers, one of which is functionally graded is solved using the theory of elasticity. In this problem functionally graded (FG) layer resting on homogeneous layer and loaded with two different rigid flat blocks. In addition, homogeneous layer is resting on a rigid plane. Frictions on all surfaces are neglected. The heights of the FG layer and the homogeneous layer are h1 and h2, respectively. When solving the problem, displacement and stress equations are substituted in the boundary conditions. Then the problem is demained to singular integral equations. Wherein unknown functions are the contact stresses under the two rigid flat blocks and the slope of the separation. These singular integral equations are solved numerically using the Gauss-Chebyshev integration formulas. The analyzes were performed for different inhomogeneity parameter (βh1), shear modulus ratio (μ2/μ-h1). distance between the rigid blocks ((a3-a2)/h1) and density parameter (γh1). Consequently, the stress distributions and starting and ending points of the separation area between the FG layer and homogeneous layer are determined for several dimensionless quantities.

Key Words
discontinuous contact problem; functionally graded layer; rigid plane; separation; theory of elasticity

Address
(1) Yusuf Kaya:
Department of Civil Engineering, Gumuhane University, Gumushane 29100, Turkey;
(2) Alper Polat:
Department of Civil Engineering, Munzur University, Tunceli 62000, Turkey;
(3) Talat Şűkrű Őzşahin:
Department of Civil Engineering, Karadeniz Technical University, Trabzon 61080, Turkey;
(4) Pınar Bora:
Department of Civil Engineering, Sivas Cumhuriyet University, Sivas 58140, Turkey.

Abstract
Lightweight high-strength concrete engineering structures have low dead weight and high seismic performance, but the brittleness is greater than that of traditional concrete. The inherent brittleness is bound to pose significant challenges for engineering applications. Based on the strategy of developing and improving the toughness of lightweight aggregate high-strength concrete, and unleashing the full potential of lightweight high-strength concrete in safer and more reliable structural applications, the study used ceramic particles as lightweight aggregates, mixed with basalt fibers and cellulose fibers to produce hybrid nature fiber reinforced lightweight high-strength concrete. By four-point flexural and fatigue tests, the flexural toughness and fatigue characteristics of the single/mixed nature fiber reinforced lightweight high-strength concrete under different stress levels were studied. And the fatigue life performance rules under different stress ratios were revealed, and the fatigue life equations were established with the two-parameters S-N(stress level-fatigue life) curve, considering the failure probability. The results show that under different stress levels, the fatigue life of all samples follows the two-parameter Weibull distribution probability model. The improvement of fatigue life of lightweight high-strength concrete with mixed fiber is better than that with single fiber, with the longest stable development duration and fatigue life. The fatigue strain evolution process of lightweight high-strength concrete with different fiber conforms to the development law of the third-order strain curve. The established fatigue life equation can be used to predict the flexural fatigue performance of fiber reinforced lightweight high-strength concrete under different stress levels. The improvement of fatigue toughness and service life has transformed lightweight high-strength concrete from "high strength but brittle" to "high strength and durability" and is expected to become an ideal material in earthquake engineering that combines lightweight, seismic performance, and sustainability.

Key Words
fatigue life; flexural fatigue behavior; hybrid fiber; lightweight high-strength concrete; nature fiber; stress level; structural performance enhancement; sustainable construction materials

Address
School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.

Abstract
The synergetic effect of steel fibers, polypropylene fibers and the hybrid effect of steel-polypropylene fibers of various concrete mixes on mechanical properties and flexural toughness was investigated. The mechanical properties include compressive strength, split tensile strength, flexural strength and modulus of elasticity. Total 16 mixes containing various concrete mixes (normal concrete of grade M35, Steel fibers – 0.5%, 1.0%, 1.5%, Polypropylene fibers (PPF) – 0.1%, 0.2%, 0.3%, hybrid fibers – each volume fraction, steel: PPF – 25%:75%, 50%:50%, 75%:25%) were cast and evaluated the mechanical properties and flexural toughness. Flexural strength, flexural toughness and indices were evaluated by using the load-deflection diagram of various concrete mixes by using the guidelines prescribed in various Codes of practices, namely, (i) ASTM C 1018 (ii) ASTM C 1609 (iii) JSCE (iv) ASTM C 1399 (v) Chinese National Standards CECS13. It was primarily observed that a concrete mix containing a fibre combination of 75% steel fibers + 25% Polypropylene fibers yielded superior mechanical properties and flexural toughness. Post peak behaviour of flexural specimens containing combination of 75% steel Fibers + 25% Polypropylene fibers found to be more ductile compared to other combinations. A method has been proposed based on the crack initiation load and percentage of peak load to determine the reserve flexural strength. Further, microstructural analysis has been carried out for the samples of plain concrete, concrete with steel fibers and concrete with hybrid fibers. It was primarily inferred from microstructural studies that due to enhanced bond between the synergy effect of steel and PPF, superior mechanical and flexural toughness were obtained.

Key Words
flexural toughness; hybrid fibre reinforced concrete; mechanical properties; microstructural investigation; polypropylene fibers; residual strength factor; steel fibers

Address
(1) B.S. Shruthi, T. Palanisamy:
Department of Civil Engineering, National Institute of Technology, Surathkal, 575014, Karnataka, India;
(2) B.S. Shruthi:
Department of Civil Engineering, Nitte Meenakshi Institute of Technology (NMIT), Nitte (Deemed to be University), Bengaluru Campus, 560064, Karnataka, India.

Abstract
In major projects such as wind turbine bearing platforms, temperature-induced stress cracking of massive reinforced concrete foundations poses a core hazard to the safe service of structures, and traditional analysis methods struggle to accurately quantify the regulatory effect of reinforcing bars on temperature and stress fields. This paper proposes a method for calculating the effective thermal conductivity tensor of reinforced concrete considering the heat conduction effect of rebars from the perspective of isothermal flow rate. Additionally, a method is introduced to calculate the equivalent mechanical parameters considering reinforcement bars deformation. Based on these equivalent parameter calculation methods, combined with finite element simulation, an accurate assessment of the thermodynamic performance evolution of mass reinforced concrete is conducted. By comparing the finite element simulation results obtained from detailed modeling methods and those obtained from equivalent parameter methods, the effectiveness of this approach in predicting temperature and stress field changes in reinforced concrete is demonstrated. Real-time monitoring of temperature changes in 15 wind turbine bearing platform foundations reveals the temperature development pattern and cracking risk of foundation concrete. Furthermore, based on design drawings, this paper reconstructs the three-dimensional structure of reinforcement bars in foundation and couples it with the solid model of foundation concrete using the aforementioned equivalent method for a quantitative analysis of the impact of rebars on foundation concrete temperature and stress fields. Simulation results show that under the influence of rebars, the heat exchange rate of foundation increases, and the maximum temperature rise of local concrete can be reduced by over 8°C. Moreover, the maximum tensile stresses on the surface and inside of the concrete are reduced by 0 to 0.82 MPa and 0 to 1.89 MPa, respectively, thereby reducing the risk of cracking.

Key Words
equivalent method; heat conduction; steel bars; thermal stress; wind power foundation

Address
(1) Ni Tan, Guoxing Zhang:
State Key Laboratory of Water Cycle and Water Security, China Institute of Water Resources and Hydropower Research, Beijing 100038, China;
(2) Jianqiang Xiang, Xingzheng Zhou:
China Three Gorges Renewables (Group) Co., Ltd., Beijing 101199, China.

Abstract
This study experimentally evaluated the bond performance of precast bridge-deck joints made with ultrahigh-performance concrete (UHPC) and aimed to improve the structural efficiency and constructability by addressing the limitations of existing design codes. Traditional connection methods, such as the loop splice method, reduce the constructability and structural efficiency. The applicability of UHPC as an alternative filling material was examined to shorten the splice length while securing structural performance. Fourteen splice specimens were fabricated with varying compressive strengths (80 MPa, 100 MPa, and 120 MPa) and splice lengths (8db, 10db, and 15db, where db is the bar diameter), and splice tests were conducted using a four-point loading method. The test results confirmed that the high compressive strength and fiber reinforcement effect of UHPC secured sufficient structural performance and crack control even at short splice lengths, whereas the existing design codes such as Eurocode 2, Korean Highway Bridge Design Code, ACI318, and Structural Design Guideline for Fiber-Reinforced SUPER Concrete revealed limitations in sufficiently reflecting the UHPC characteristics. To solve these problems, machine learning techniques were applied, and new bond strength and development-length prediction models employing random forest and SHAP for factor analysis and symbolic regression (PySR) were proposed. The proposed models achieved high prediction accuracy, demonstrating their potential for optimizing the bond performance of UHPC structures to ensure structural safety and improving the design efficiency of precast construction methods.

Key Words
bond performance; design codes; machine learning; precast; UHPC

Address
(1) Ho-Bi Kang, Dong-kyu Lim, Myoung-Sung Choi:
Department of Civil Environmental Engineering, Dankook University, 152, Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do 16890, Republic of Korea;
(2) Young-Jin Kim:
Korea Concrete Institute (KCI), 22, Teheran-ro 7-gil, Gangnam-gu, Seoul 06130, Republic of Korea.

Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2026 Techno-Press ALL RIGHTS RESERVED.
P.O. Box 33, Yuseong, Daejeon 34186 Korea.
General Inquiries: info@techno-press.com / Journal Administration: admin@techno-press.com