Abstract
In order to investigate the seismic performance of regionally confined concrete circular column with trapezoid
stirrups (TRCCC) under high axial compression ratio, the confinement mechanism of regionally confined concrete was
analyzed. Three regionally confined concrete circular columns with trapezoid stirrups were designed, and low cyclic loading
tests were conducted at three different axial compression ratios (0.9, 1.1, 1.25) to study the failure mode, hysteresis curve,
skeleton curve, deformation capacity, stiffness degradation and energy dissipation capacity of the specimens. The results indicate
that the form of regional confinement concrete provides more uniform confinement to the normal confinement, and the
confinement efficiency at the edges is 1.4 times that of normal confined concrete. The ductility coefficients of the specimens
were all greater than 3 under high axial compression ratios, and the stiffness and horizontal bearing capacity increased with the
increase of axial compression ratio. Therefore, it is recommended that the code of design specifications can appropriately relax
the axial compression ratio limit for TRCCC. Finally, the spacing between stirrups of TRCCC was analyzed using ABAQUS
software. The results showed that as the spacing between the stirrups decreased, the cracking load and peak load of TRCCC
increased continuously, but the rate of increase decreases.
Key Words
regionally confined concrete column; trapezoid stirrup; seismic performance; low cyclic loading tests; finite
element analyses; axial compression ratio
Address
Longfei Meng and Hao Su:School of Civil Engineering, Xi'an University of Architecture and Technology, No.13, Yanta Road, Beilin District, Xi'an, China
Yanhua Ye and Haojiang Li:School of Civil Engineering, Nanjing Tech University, No.30 Puzhu South Road, Pukou District, Nanjing, China
Abstract
This work aims to explore the static behaviour of a tapered functionally graded porous plate (FGPP) with even and
uneven porosity distributions resting on two parametric elastic foundations. The plate under investigation is subjected to bisinusoidal loading and the edges of the plate are exposed to different combinations of edge restrictions. In order to examin the
static behaviour, bending factors (BF) related to bending and normal stresses have been evaluated using classical plate theory. To
achieve this, the governing equations have been derived employing the energy concept. And to solve it, the Rayleigh-Ritz
method with an algebraic function has been utilised; it is simple, precise, and computationally intensive. After convergence and
validation analyses, new findings are made available. The BF of the plate have been exhaustively examined to explain the
influence of aspect ratios, material property index, porosity factor, taper factor, and Winkler and Pasternak stiffness. It is
observed that the BF of an elastically supported FGPP are influenced by the index of material propery and the aspect ratio.
Findings also indicate that the impact of porosity is more when it is spread evenly, as opposed to when it is unevenly distributed.
Further, the deformed plate's structure is significantly influenced by the different thickness variations. Examination of bending
characteristics of FGPP having different new cases of thickness variations with different types of porosity distribution under
fifteen different mixed edge constraints is the prime novality of this work. Results presented are reliable enough to be taken into
account for future studies.
Address
Rajat Jain and Mohammad Sikandar Azam:Department of Mechanical Engineering, Indian Institute of Technology (ISM) Dhanbad, Jharkhand-826004, India
Abstract
In the construction industry, composite structures have revolutionized traditional design principles, opening
innovative possibilities. The Concrete Encased - Concrete Filled Steel Tubular (CE-CFST) column stands out as a distinctive
composite structure, offering structural stability and resilience for various engineering applications. Comprising Reinforced
Concrete (RC) and Concrete Filled Steel Tubular (CFST) components, CE-CFST columns are valued for their inherent
properties, including ductility and rigidity, CE-CFST is commonly used in the construction of bridges, high-rise buildings, and
more. This article aims to provide a concise overview of the evolutionary development of CE-CFST columns and their
performance in structural applications. Through a comprehensive review, the study delves into the behaviour of CE-CFST
columns under different scenarios. It examines the influences of key parameters such as size, infills, cross section, failure causes,
and design codes on the performance of CE-CFST columns, highlighting their enhanced functionality and future potential.
Moreover, the review meticulously examines previous applications of CE-CFST columns, offering insights into their practical
implementation.
Abstract
Given the increased interest in enhancing structural sustainability, the current study sought to apply multiobjective
optimization to a footbridge with a steel-concrete composite I-girder structure. It was considered as objectives minimizing the
cost for building the structure, the environmental impact assessed by CO2 emissions, and the vertical accelerations created by
human-induced vibrations, with the goal of ensuring pedestrian comfort. Spans ranging from 15 to 25 meters were investigated.
The resistance of the slab's concrete, the thickness of the slab, the dimensions of the welded steel I-profile, and the composite
beam interaction degree were all evaluated as design variables. The optimization problem was handled using the Multiobjective
Harmony Search (MOHS) metaheuristic algorithm. The optimization results were used to generate a Pareto front for each span,
allowing us to assess the correlations between different objectives. By evaluating the values of design variables in relation to
different levels of pedestrian comfort, it was identified optimal values that can be employed as a starting point in predimensioning of the type of structure analyzed. Based on the findings analysis, it is possible to highlight the relationship between
the structure's cost and CO2 emission objectives, indicating that cost-effective solutions are also environmentally efficient.
Pedestrian comfort improvement is especially feasible in smaller spans and from a medium to a maximum level of comfort, but
it becomes expensive for larger spans or for increasing comfort from minimum to medium level.
Address
Fernando L. Tres Junior, Guilherme F. Medeiros and Moacir Kripka:Graduate Program in Civil and Environmental Engineering, University of Passo Fundo, BR 285 Km 292.7, Passo Fundo 99052-900, Brazil
Abstract
The utilization of geopolymer recycled aggregate concrete (GRAC) as the infilled core of the concrete-filled steel
tubular (CFST) columns provides superior economic and environmental benefits. However, limited research exists within the
field of geopolymer recycled aggregate concrete considered a green and sustainable material, in addition to the limitation of the
design guidelines to predict the behavior of such an innovative new material combination. Moreover, the behavior of highstrength concrete is different from the normal-strength one, especially when there is another material of high-strength properties,
such as the steel tube. This paper aims to investigate the behavior of the axially loaded square high-strength GRACFST columns
through the nonlinear finite element analysis (NLFEA). A total of thirty-two specimens were simulated using
ABAQUS/Standard software with three main variables: recycled aggregate replacement ratio (0, 30, and 50) %, width-tothickness ratios (52.0, 32.0, 23.4, and 18.7), and length-to-width ratio (3, 5, 9, and 12). During the analysis, the response in terms
of the axial load versus the longitudinal strain was recorded and plotted. In addition, various mechanical properties were
calculated and analyzed. In view of the results, it has been demonstrated that the mechanical properties of high-strength
GRACFST columns such as ultimate load-bearing capacity, compressive stiffness, energy absorption capacity, and ductility
increase with the increase of the steel tube thickness owing to the improvement of the confinement effect of the steel tube. In
contrast, the incorporation of the recycled aggregate adversely affected the mentioned properties except the ductility, while the
increase of the recycled aggregate replacement ratio improved the column's ductility. Moreover, it has been found that the
increase in the length-to-width ratio significantly reduced both the failure strain and the energy absorption capacity. Finally, the
obtained NLFEA results of the ultimate load-bearing capacity were compared with the corresponding predicted capacities by
numerous codes. It has been concluded that AISC, ACI, and EC give conservative predictions for the ultimate load-bearing
capacity since the confinement effect was not considered by these codes.
Key Words
CFST column; geopolymer concrete; high-strength; NLFEA; recycled aggregate
Address
Rajai Z. Al-Rousan and Haneen M. Sawalha:Department of Civil Engineering, Faculty of Engineering, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan
Abstract
This paper presents a novel technique that combines machine learning (ML) with moth-flame optimization (MFO)
methods to predict the axial compressive strength (ACS) of concrete filled double skin steel tubes (CFDST) columns. The
proposed model is trained and tested with a dataset containing 125 tests of the CFDST column subjected to compressive loading.
Five ML models, including extreme gradient boosting (XGBoost), gradient tree boosting (GBT), categorical gradient boosting
(CAT), support vector machines (SVM), and decision tree (DT) algorithms, are utilized in this work. The MFO algorithm is
applied to find optimal hyperparameters of these ML models and to determine the most effective model in predicting the ACS of
CFDST columns. Predictive results given by some performance metrics reveal that the MFO-CAT model provides superior
accuracy compared to other considered models. The accuracy of the MFO-CAT model is validated by comparing its predictive
results with existing design codes and formulae. Moreover, the significance and contribution of each feature in the dataset are
examined by employing the SHapley Additive exPlanations (SHAP) method. A comprehensive uncertainty quantification on
probabilistic characteristics of the ACS of CFDST columns is conducted for the first time to examine the models' responses to
variations of input variables in the stochastic environments. Finally, a web-based application is developed to predict ACS of the
CFDST column, enabling rapid practical utilization without requesting any programing or machine learning expertise.
Address
Quang-Viet Vu:1)Laboratory for Computational Civil Engineering, Institute for Computational Science and Artificial Intelligence,
Van Lang University, Ho Chi Minh City, Vietnam
2)Center of Excellence in Applied Mechanics and Structures, Department of Civil Engineering,
Chulalongkorn University, Bangkok 10330, Thailand
Dai-Nhan Le:Faculty of Building and Industrial Construction, Hanoi University of Civil Engineering, Hanoi, Vietnam
Thai-Hoan Pham:Faculty of Building and Industrial Construction, Hanoi University of Civil Engineering, Hanoi, Vietnam
Wei Gao:Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering,
The University of New South Wales, Sydney, NSW, 2052, Australia
Sawekchai Tangaramvong:Center of Excellence in Applied Mechanics and Structures, Department of Civil Engineering,
Chulalongkorn University, Bangkok 10330, Thailand
Abstract
In this paper, the dynamic flexural stiffness of concrete-filled steel tubular (CFST) members is investigated based on
vibration modal testing and a Bayesian model updating procedure. To reflect the actual service states of CFST members, a 3-
stage modal testing procedure is developed for 6 circular CFST beam-columns, in which the modal parameters of the specimens
under varying axial load levels are extracted. In the model updating procedure, a Timoshenko beam element model is first
established, in which the influence of shear deformation and rotational inertia are incorporated. Subsequently, a 2-round
Bayesian model updating strategy is proposed to calculate the dynamic flexural stiffness of the specimens, which could
effectively consider the influence of physical constraints in the updating process and achieve reasonably well results. Analysis of
the updating results shows that with the increase of the axial load level, degradation of the flexural stiffness is significantly
influenced by the load eccentricity. It shows that the cracking of the core concrete is the primary reason for the flexural stiffness
degradation of CFST beam-columns. Finally, based on comparison with equations proposed by several design standards, the
calculation methods for the dynamic flexural stiffness of CFST members is recommended.
Key Words
Bayesian model updating; Concrete-filled steel tubular (CFST) members, dynamic flexural stiffness,
Timoshenko beam element model; vibration
Address
Shang-Jun Chen and Chuan-Chuan Hou:School of Transportation Science and Engineering, Beihang University, Beijing, 100191, P.R. China
Abstract
Damage detection in structures using the change of modal parameters (modal shapes and natural frequencies) has
achieved satisfactory results. However, as modal shapes and natural frequencies alone may not provide enough information to
accurately detect damages. Therefore, a hybrid singular value decomposition and deep belief network approach is developed to
effectively identify damages in aluminum plate structures. Firstly, damage locations are determined using singular value
decomposition (SVD) to reveal the singularities of measured displacement modal shapes. Secondly, using experimental modal
analysis (EMA) to measure the natural frequencies of damaged aluminum plates as inputs, deep belief network (DBN) is
employed to search damage severities from the damage evaluation database, which are calculated using finite element method
(FEM). Both simulations and experimental investigations are performed to evaluate the performance of the presented hybrid
method. Several damage cases in a simply supported aluminum plate show that the presented method is effective to identify
multiple damages in aluminum plates with reasonable precision.
Key Words
aluminum plate; damage detection method; deep belief network; finite element method; singular value
decomposition
Address
Jinshang Sun, Qizhe Lin, Hu Jiang and Jiawei Xiang:College of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou, 325035, P.R. China
