Abstract
This study proposes a Domain Knowledge Enhanced Neural Network model based on the Integrated
Multidimensional Feature Selection (IMFS-DKNN) method, aimed to accurately predict the bearing capacity of
Concrete-Filled Steel Tube (CFST) members. The model integrates domain knowledge to conduct a comprehensive
analysis of the mechanical behavior of CFST columns, identify critical parameters that influence bearing capacity, and
construct corresponding features. Subsequently, the Integrated Multidimensional Feature Selection (IMFS) method is
applied to select features with high representativeness and generalizability, ensuring the stability and quality of the
model's inputs. Domain knowledge constraints are incorporated into the loss function to capture monotonic
relationships and approximate dependencies between input parameters and outputs, thereby enhancing both
interpretability and predictive accuracy. Ablation studies are conducted to iteratively optimize the model architecture,
thereby improving performance. The model is validated using a dataset comprising 2,621 circular CFST specimens
under axial compression, demonstrating a substantial improvement in prediction accuracy, with a Mean Absolute
Percentage Error (MAPE) reduction exceeding 30% compared to the best existing model AIJ Furthermore, a Genetic
Algorithm-based SHAP (GA-SHAP) method and strength index analysis are employed for detailed parameter
evaluation. The study also introduces the Relative SHAP Contribution Difference (RSCD) metric to quantify feature
interaction effects, providing scientific design guidance for the design of circular CFST members under axial loading.
Address
Dian Wang: School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, PR China
Qiankun Wang: 1)School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, PR China
2)Sanya Science and Education Innovation Park of Wuhan University of Technology, Sanya 572000, PR China
Gen Kondo: Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA
Shuo Bai:School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, PR China
Yihao Zhang: Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA
Abstract
Previous studies have demonstrated that Modified Clothoide (MCL) shape composite dowels have
excellent mechanical and fatigue performance, highlighting their strong potential for application in composite bridge
structures. However, current studies have primarily focused on the connectors themselves, while systematic
investigations into the cross-sectional flexural behavior are still lacking. In this study, based on an actual engineering
project, a 20 m full-scale simply supported composite beam was designed and tested under four-point bending. The
flexural performance of the composite beam was systematically examined by analyzing experimental phenomena,
failure modes, and characteristic curves, such as load–deflection and load–slip curves. Then, a refined three
dimensional finite element model was established to further analyze its flexural behavior. Results demonstrated that
the composite beam exhibited excellent flexural capacity. During loading, the strain distribution in the pure bending
section consistently satisfied the plane-section assumption, albeit with a pronounced shear-lag effect in the concrete
flange. At the stage of failure, significant deformation occurred at the mid-span of the beam, accompanied by
multiple microcracks, and no obvious slippage occurred at the shear connector interface in the bending–shear zone,
which indicated that the MCL-shaped composite dowels effectively transferred shear forces at the steel–concrete
interface and ensured coordinated behavior. This study can provide crucial experimental and theoretical support for
the design of composite beams with MCL-shaped composite dowels.
Key Words
composite beam; finite element analysis; flexural performance; full-scale test; MCL-shaped
composite dowel
Address
Ming-Guang Wei:1)Tongji University, Shanghai 200092, China
2)Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., Shanghai 200092, China
Wen-Hui Zhang:Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China
Yang Jiang:Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., Shanghai 200092, China
Ding-Hao Yu: Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China
Jian-Nan Lin: Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China
Qing-Tian Su: Tongji University, Shanghai 200092, China
Abstract
The influence of aftershocks following a strong mainshock on the seismic performance of structures cannot
be neglected, whereas most existing studies on the seismic performance of bridge-track systems (BTS) have focused
primarily on the mainshock. To investigate the seismic performance of BTS under mainshock-aftershock sequences,
a seven-span BTS finite element model was developed in OpenSEES. A total of 187 recorded mainshock-aftershock
ground motions were selected from the PEER database to conduct nonlinear time-history analyses. Based on multiple
evaluation criteria, the optimal intensity measure (𝐼𝑀) for constructing fragility curves under mainshock-aftershock
sequences were identified, and the differences between component-level fragility curves under mainshock and
aftershock actions were analyzed. A system-level fragility assessment framework was established using the t-Copula
function combined with the Monte Carlo simulation, accounting for correlations among components, and the
differences between system-level and component-level fragilities were compared. In addition, the Birnbaum
importance index was employed to quantify the contribution of individual components to the system failure probability.
The results indicate that the acceleration-based measure 𝑆𝑎(𝑇1,𝜉) enables a reasonable construction of fragility
curves for both components and the overall system under mainshock-aftershock sequences. Considering aftershock
effects, the 𝐼𝑀 corresponding to the peak failure probability is lower, and the failure probability of robust components
increases significantly. As the damage level rises, the system's failure-controlling mechanism gradually shifts from
vulnerable to robust components, and the influence of a single component on the overall seismic performance becomes increasingly limited. This study provides insights for the seismic design of high-speed railway bridges.
Address
Hongyu Jia:1)State Key Laboratory of Bridge Intelligent and Green Construction,
Southwest Jiaotong University, Chengdu, 611756, Sichuan, China
2)School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Yikun Zhai:School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Chong Wang:Tianjin Municipal Engineering Design & Research Institute Co. Ltd., Tianjin, 300392, China
Yingxin Hui:School of Civil and Water Resources Engineering, Ningxia University, Yinchuan, 750021, China
Shixiong Zheng:1)State Key Laboratory of Bridge Intelligent and Green Construction, Southwest Jiaotong University, Chengdu, 611756, Sichuan, China
2)School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Abstract
In steel concrete composite beam systems, shear connectors are essential components that ensure the
effective interaction between the tensile strength of the steel section and the compressive strength of the concrete. In
conventional applications, these connectors are typically welded to the beam flange. However, while this approach is
suitable for hot-rolled steel sections, it causes damage concentration in the beam flange rather than in the connector
itself when applied to cold-formed steel (CFS) beams with thin walls. In this study, an innovative shear connector
system was developed where the connection element is attached to the web of the CFS beam instead of the flange,
and its performance was experimentally investigated. The proposed connector was partially isolated from the
concrete, allowing it to deform freely under applied loads. As part of the experimental program, full-scale specimens
fabricated from CFS sigma profiles were tested under push-out and bending conditions. The results were compared
with commonly used bolted shear connector systems. The push-out test results showed that all damage was
concentrated in the proposed shear connector, with no observable damage or deformation in the CFS beam. The
bending test results demonstrated that the proposed connector contributed positively to the flexural capacity of the
CFS–concrete composite beam system.
Address
Fatih Cebir:Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Türkiye
Hussien A. Soalih:Department of Civil Engineering, School of Civil and Hydraulic Engineering, Institute
of Technology, University of Gondar, Gondar, Ethiopia
Serhat Demir:Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Türkiye
Abstract
This study investigates the axial behavior of square geopolymer recycled aggregate concrete columns
reinforced with fiber-reinforced polymer (FRP) bars. The use of recycled aggregates improves sustainability but
reduces strength and durability, while FRP bars offer corrosion resistance. However, conventional FRP hoops provide
limited confinement in square columns, especially at corners. To address this limitation, a novel combined FRP
helix–hoop confinement system is proposed, where internal FRP helix bars and external prismatic FRP hoops
provide double confinement to the concrete core. Nine full-scale columns with dimensions of 300 x 300 x 1200 mm
were tested under axial compression. All columns were cast using geopolymer concrete with 100% recycled coarse
aggregates. The main parameters were helix pitch (50-150 mm), FRP tie diameter (9.5 and 12.7 mm), confinement
configuration, and longitudinal bar type. Reducing the helix pitch from 150 mm to 50 mm increased the maximum
axial load by 27% and significantly improved post-peak stability. Increasing the FRP tie diameter enhanced peak load
by about 8% and doubled the axial strain at 85% post-peak load. Columns with combined helix confinement
achieved ductility coefficients up to 13.82, compared to 5.63 for single-hoop confinement. The concrete strength
enhancement factor reached 1.36 for dense helix confinement. A new analytical model considering double
confinement zones was developed and predicted the test results with a maximum error below 6%. The results show
that combined FRP helix-hoop confinement effectively improves strength, ductility, and deformation capacity of
recycled aggregate geopolymer concrete columns.
Address
Khaled Mohamed Elhadi:1)Department of Civil Engineering, College of Engineering, King Khalid University, Abha, 61421, Saudi Arabia
2)Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia
Nejib Ghazouani:Mining Research Center, Northern Border University, Arar, 73213, Saudi Arabia
Umara Nasir:Department of Civil Engineering, University of Engineering and Technology Taxila, 47050, Pakistan
Abstract
To investigate the seismic performance of cross-shaped concrete-filled steel tubular (CFST) columns,
cyclic loading tests were conducted on five 1/2-scaled specimens. Key indicators, including failure mode, load
displacement curves, energy dissipation capacity, and stiffness degradation, were analyzed. The damage evolution, as
well as the proportions of energy dissipation-induced damage and plastic deformation-induced damage, were
evaluated based on the Park-Ang damage model. The results indicate that all specimens undergo base local buckling
failure, accompanied by fracture of steel tubes and welds, as well as concrete crushing. The hysteretic curves are
plump, demonstrating excellent energy dissipation capacity with equivalent viscous damping coefficients ranging
from 0.255 to 0.386. The bearing capacity increases with the axial compression ratio, while the post-peak load
decreases more steeply. Stiffness and bearing capacity are gradually enhanced as the depth-to-width ratio increases.
The damage evolution of cross-shaped CFST columns is more dependent on cumulative energy dissipation under
cyclic loading than on plastic deformation development. An increase in the axial compression ratio or depth-to-width
ratio results in an overall increase in cumulative energy dissipation damage and a reduction in plastic deformation
damage.
Address
Yan Yang:1)School of Civil Engineering, Tianjin University, Tianjin, 300350, China
2)College of Civil Engineering and Architecture, Huanghuai University, Zhumadian 463000, China
Jian Xie: School of Civil Engineering, Tianjin University, Tianjin, 300350, China
Hechao Li: College of Civil Engineering and Architecture, Huanghuai University, Zhumadian 463000, China
Meng Zhan: College of Civil Engineering and Architecture, Huanghuai University, Zhumadian 463000, China
Jianyang Xue: College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Tao Li: College of Civil Engineering and Architecture, Huanghuai University, Zhumadian 463000, China
Li Shang: College of Energy Engineering, Huanghuai University, Zhumadian 463000, China
Abstract
In this study, we investigate the dynamic modal behavior of the recently developed layered shell finite
element with interface slips. The formulation for the layered shell element with interface slips, allowing for modal
analysis is derived. We focus on the eigenfrequencies corresponding to the low-frequency eigenmodes of the layered
shell element with interface slips. For comparison, 3D solid element models are also used. The layered shell element
with interface slips enables simple modeling regardless of the connection stiffness or the number of layers and uses a
reduced number of degrees of freedom (DOFs), which improves the efficiency of the modal analysis. Several
numerical cases are used to demonstrate the accuracy of the layered shell element. The layered shell element shows
potential for predicting the dynamic responses of emerging multi-layered structures with adhesive-bonded composite
layers.
Key Words
adhesive-bonded composite layer; dynamic modal behavior; eigenfrequencies; finite element
analysis; interface slips; layered composite shell element
Address
Sungbo Lee: Gen-IV Reactor Technology Development Division, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon, Republic of Korea
Seunghwan Park: Next-generation Research reactor Design Division, Korea Atomic Energy Research Institute,
111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon, Republic of Korea
Abstract
PHC pipe piles, commonly used as supports in offshore and coastal photovoltaic projects, are designed as
cantilevers extending 3-5 m above water to withstand waves. However, water entering the hollow sections can freeze
and expand, causing cracks in the cantilevered sections. This cracking reduces the structural performance of the piles
and threatens the safety of the PV system, highlighting the necessity for effective strengthening. This study
investigates the mechanical performance loss of cracked PHC pipe piles and the behavior after CFRP strengthening.
Full-scale static tests—axial compression, four-point bending, and shear—were carried out on intact, cracked, and
CFRP-strengthened specimens. During the tests, strain gauges measured sectional strain, while load-displacement
responses were recorded to assess key mechanical parameters. The results indicate that cracking reduced the axial,
bending, and shear capacities of PHC pipe piles by about 28.2%, 4.8%, and 12.3%, respectively. CFRP strengthening
increased these capacities by approximately 26.4%, 14%, and 16.9%, respectively, with the flexural and shear
capacities even exceeding those of the intact piles. The findings of this study provide a design reference for the repair
and strengthening of cracked PHC piles and offer guidance for the rehabilitation of piles damaged by other causes.
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