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CONTENTS
Volume 99, Number 5, September10 2026
 

Abstract
This study experimentally investigates the effects of cement-sand plaster layers and unfired brick dimensions on the structural behavior of two-span reinforced concrete frames with masonry infill walls under monotonic lateral loading. Four two-span RC frame specimens were designed and tested using a 2x2x2 experimental matrix, including two unfired brick sizes, 40x80x180 mm and 80x80x180 mm, with and without a 10 mm-thick B5 cement-sand plaster layer. The specimens K2 and K3 were unplastered, while K4 and K5 were plastered. The test results show that the plaster layer significantly influenced crack development, deformation distribution, and lateral load capacity. For the specimens built with 40x80x180 mm bricks, the ultimate lateral load increased from 110 kN in K2 to 140 kN in K4, corresponding to an increase of approximately 27.3%. For the specimens built with 80x80x180 mm bricks, the ultimate lateral load increased from 110 kN in K3 to 130 kN in K5, corresponding to an increase of approximately 18.2%. Brick dimensions affected the first cracking load and crack pattern; however, no increase in ultimate lateral capacity was observed between the two unplastered specimens, since both K2 and K3 failed at 110 kN. The findings indicate that cement-sand plaster contributes to improved crack control and lateral response of twospan RC frames with unfired brick infill walls under monotonic lateral loading.

Key Words
brick dimension; crack propagation; masonry infill; monotonic lateral loading; plaster layer; reinforced concrete frame; unfired brick

Address
T.Q.K. Lam: Faculty of Civil Engineering, Mien Tay Construction University, Vinh Long, Vietnam
Van-Bang Bui: Faculty of Civil Engineering, Hau Giang Community College, Can Tho, Vietnam

Abstract
This study introduces an innovative inverted T-shaped straddle monorail (ITSM) system to optimize the structural configuration of conventional straddle-type monorail systems. The proposed ITSM system achieves three critical improvements: (1) elimination of stabilizing wheels through enhanced lateral span design of riding wheels; (2) implementation of an inverted T-shaped steel-concrete composite track beam that reduces the overall structural height while maintaining operational stability; (3) simplification of wheel-rail contact relationship to enhance the structural performance. A dynamic model of the system is developed using D'Alembert's principle, and dynamic responses are analyzed through co-simulation with MATLAB and ANSYS. The results show that when the train runs at full load at a speed of 80 km/h on a three-span simply supported bridge, the lateral and vertical accelerations of the train meet the safety requirements specified in the code. The ITSM system achieves a running quality and riding comfort level of "Good" and "Noticeable", similar to the conventional straddle monorail system. Further optimization analysis of the track beam indicated that an outer steel plate thickness of approximately 14 mm and an inner steel plate thickness of 10 mm ensure both structural strength and economic efficiency whereas web spacing of approximately 1.2 m, coupled with the riding wheels span, can balance structural safety with vibration control. With outstanding dynamic performance, structural efficiency, and comfort, the ITSM system would be a viable alternative to conventional straddle-type monorail systems.

Key Words
co-simulation; dynamic modeling; inverted t-shaped straddle monorail; structural optimization; vehicle-bridge interaction

Address
Junyu Xiao: School of Civil and Transportation Engineering, Guangzhou University, Guangzhou, 510000, P.R. China
Yanliang Du: School of Civil and Transportation Engineering, Guangzhou University, Guangzhou, 510000, P.R. China
Guoqing Wang: Hebei Transportation Investment Group Company Limited, Shijiazhuang, 050000, P.R. China
Jiang Yi: School of Civil and Transportation Engineering, Guangzhou University, Guangzhou, 510000, P.R. China

Abstract
To improve the mechanical performance of lattice structures, various lattice structures have been systematically explored using Deep Neural Networks (DNNs), Variational Auto-Encoder (VAE), and Bayesian optimization to achieve superior mechanical properties tailored to specific targets. In this study, cubic-symmetry lattice structures were generated within a 27-node unit cell by applying 120o rotational symmetry about the diagonal axes. During the structure search, the lattice structures were reconstructed from the latent space using a decoder in the VAE, efficiently navigating the enormous design space of the structures. Then, Bayesian optimization was employed to identify the optimal structures that satisfied the target properties. To train and test the mechanical property prediction model, Finite Element Analysis (FEA) was performed by controlling the applied strain to compute the elastic constants Cij and porosity o of the lattice structures. Finally, the generated structures were compared with the prediction from the Gibson-Ashby model. This study can contribute to the development of high-performance lattice structures for various engineering applications.

Key Words
bayesian optimization; deep neural network; elastic constants; lattice structure; machine learning; porosity; variational auto-encoder

Address
Seungjin Kim: Department of Mechanical Engineering, Yonsei University, Seoul 03722, Republic of Korea
Yongwoo Kim: Department of Mechanical Engineering, Yonsei University, Seoul 03722, Republic of Korea
Donggeun Park: Department of Mechanical Engineering, KAIST, Daejeon 34141, Republic of Korea
Sang Joon Lee: Department of Mechanical Engineering, Yonsei University, Seoul 03722, Republic of Korea
Sangryun Lee: Department of Mechanical and Biomedical Engineering, Ewha Womans University, Seoul 03760, Republic of Korea
Keonwook Kang: Department of Mechanical Engineering, Yonsei University, Seoul 03722, Republic of Korea

Abstract
Steel-UHPC composite beams, where ultra-high-performance concrete (UHPC) replaces normal concrete (NC) in the slab and is combined with a steel girder, provide advantages including reduced self-weight, large-span applicability, and enhanced crack resistance and durability. To investigate differences in long-term performance between steel-UHPC and steel-NC composite beams, this study establishes a finite element framework considering geometric configuration and mechanical characteristics of composite beams, with emphasis on steel-UHPC systems. The NC/UHPC slab is modeled using Euler-Bernoulli beam theory, while the steel girder is described using Timoshenko beam theory to capture shear deformation. Interlayer slip caused by partial interaction between slab and girder is included. Based on elastic mechanics, governing differential equations are derived, and a novel composite beam element is formulated using the direct stiffness method. An age-dependent linear viscoelastic model is adopted to account for shrinkage and creep of the NC/UHPC slab. By integrating the proposed element with the time-dependent constitutive model, a new finite element method for long-term analysis of composite beams is developed. Results indicate that within commonly used span-to-depth ratios and interfacial shear stiffness ranges, the proposed method provides higher accuracy than the double-layer Euler-Bernoulli beam method and higher efficiency than the double-layer Timoshenko beam method. The long-term variation of steel-NC composite beams lies between those of steel-UHPC beams under hygrothermal curing and normal-temperature moist curing. For normal-temperature moist curing, UHPC shrinkage dominates long-term behavior, with a coupled shrinkage-creep effect observed. These findings provide reference for long-term design of steel-concrete composite beams.

Key Words
a novel element model; composite beams; interface slip; long-term performance; ultra-high performance concrete (UHPC)

Address
Jian-ping Tan, Ji-hua Luo, Lu-yi Liang: School of Civil and Environmental Engineering, Changsha University of Science & Technology, Changsha, Hunan, 410114, China
Ji-hua Deng: School of Civil and Environmental Engineering, Changsha University of Science & Technology, Changsha, Hunan, 410114, China; Ministry of Education Key Laboratory of Safety Control of Bridge Engineering, Changsha University of Science & Technology, Changsha, Hunan, 410114, China

Abstract
Traditionally, the planning and design of road infrastructure projects relied on conventional methods that often lacked the ability to simulate complex, real-world conditions. However, with recent technological advancements, the InfraWorks tool, integrated into Building Information Modeling (BIM), has become essential for visualizing and analyzing road projects in a realistic, dynamic, and data-rich environment. This integrated approach enhances early-stage decision-making by enabling engineers and planners to model terrain, hydrology, and infrastructure constraints more effectively. The process begins with the generation and evaluation of several route alternatives, which are compared based on a set of technical, environmental, and economic criteria in order to determine the most appropriate alignment. The main objective of this study is to identify and replace the most floodprone road segment among those connecting the city of Sidi Belattar to National Road 90, located on the left bank of the Chellif River in Algeria an area known for recurring seasonal flooding. To address this challenge, two multicriteria decision-making (MCDM) methods VIKOR and TOPSIS are applied to assess and rank the proposed alternatives. These complementary approaches, VIKOR and TOPSIS, enable a systematic and objective comparison of variants. The results show a high degree of consistency between the two methods, both identifying the first alternative as the most suitable solution to replace the vulnerable section of the existing route. In conclusion, this integrated approach represents a significant advancement through the use of InfraWorks and MCDM techniques, offering an innovative and effective methodology for optimizing road infrastructure planning and design from the earliest project stages.

Key Words
BIM; InfraWorks; MCDM; road; TOPSIS; VIKOR

Address
Manal Ikram Hadjar, Mohamed Zaoui, Tahar Kadri: Materials and Construction Processes Laboratory (LMPC), University Abdelhamid Ibn Badis, Mostaganem, Algeria; Department of Civil Engineering, Faculty of Science and Technology, University Abdelhamid Ibn Badis, Mostaganem, Algeria
Lazreg Hadji: Department of Civil Engineering, University of Tiaret, Tiaret, Algeria
Mohamed Bensoula: Department of Civil Engineering, Faculty of Science and Technology, University Abdelhamid Ibn Badis,
Mostaganem, Algeria

Abstract
This study presents a comprehensive parametric investigation into the optimal design, performance, and cost-efficiency of hybrid seismic isolation systems, specifically lead-rubber bearings (LRBs) and fluid viscous dampers (FVDs), for retrofitting highway bridges exposed to diverse seismicity levels (SLs) and site soil classes (SCs). A fully automated and holistic optimization framework is developed, combining synthetic ground motions consistent with site-specific target spectra and a metaheuristic optimization technique to minimize the cost of seismic protection devices while satisfying stringent displacement and strength constraints. The results demonstrate feasible seismic device solutions across most SCs and SLs, except for the weakest soft soil under high seismic demands, where displacement and shear constraints were exceeded by up to 87%, indicating that hybrid isolation alone may not guarantee acceptable structural performance. Sensitivity analysis highlights that increasing the lead-core diameter effectively reduces isolator displacement and enhances damping up to an optimal point, after which further enlargement offers no additional benefits and can diminish damping performance. Furthermore, rock-type SCs require longer optimal bridge periods whereas softer soils cause larger pier displacements, making pier deformation a key seismic design constraint at high seismicity. These outcomes underscore the essential interplay between soil conditions and seismic intensity, highlighting the need for additional structural strengthening in soft soils subjected to strong ground motions. Finally, LRBs constitute the largest portion of hybrid seismic device costs, increasing by at least fivefold from hard rock to soft soil conditions under high seismicity, whereas damper costs increased approximately threefold.

Key Words
fluid viscous damper; lead-rubber bearing; seismic isolation; seismicity; structural design optimization

Address
Ali I. Karakas: Department of Civil Engineering, Karadeniz Technical University, Trabzon, 61080, Türkiye

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