Abstract
This article examines the in-plane and out-of-plane bending vibration analysis of Laminated Composite Curved Beams (LCCB) under various boundary conditions. A new mathematical model is proposed, enabling the calculation of in-plane and out-of-plane bending vibration characteristics for beams with arbitrary layups. To derive the governing equations, Poisson's effect along with the coupling effects between extension, bending, and torsional deformations are incorporated, which play a crucial role in the vibrational characteristics, particularly for angle-ply and general layups. Analytical and finite element solutions are presented to obtain the responses, validated through comparison with results obtained from 3D software ANSYS, showing excellent agreement. Finally, the influence of different parameters on the vibrational characteristics of the LCCB is investigated in detail.
Key Words
analytical solution; arbitrary layups; finite element solution; free vibrations; laminated composite curved
beam
Address
Ramazan-Ali Jafari-Talookolaei: School of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
Saman Sadripour: School of Mechanical Engineering, Babol Noshirvani University of Technology, Babol, Iran
Hamidreza Ghandvar: Department of Mechanical Engineering, Faculty of Engineering, New Uzbekistan University, Movarounnahr Street 1, Mirzo Ulugbek District, Tashkent, Uzbekistan
Elyorjon Jumaev: University of Business and Science, 1 Gavhar Street, Chilanzar District, Tashkent 100185, Uzbekistan
Orifjon Mikhliev: FIE UzLITI Engineering LLC, 129B Amir Temur Street, Tashkent 100099, Uzbekistan
Abstract
In this study, axisymmetric models to predict the ultimate strength of circular concrete-filled double-skin steel tube
(CFDST) short columns containing Normal Concrete (NC), High-Performance Concrete (HPC), or Ultra-High-Performance
Concrete (UHPC) under axial compression are developed. A simplified concrete material model is proposed for these
axisymmetric models, offering more convenience compared to the previous axisymmetric model, which was validated only for NC, HPC, and concrete-filled steel tube (CFST) columns. The reliability and accuracy of the new model are verified using experimental data. This study demonstrates that the combination of the axisymmetric model and the simplified concrete model significantly reduces computational time while maintaining acceptable accuracy. The proposed method can generate extensive numerical databases for structural optimization or machine learning-based strength prediction. The reduced computational effort of axisymmetric models, compared to 3D models, allows for a comprehensive parametric study of axial load-displacement curves in circular CFDST short columns, exploring various influencing factors. Additionally, the study evaluates established design codes, including Eurocode 4 (EC4), American Concrete Institute (ACI), and American Institute of Steel Construction (AISC), along with analytical models from the literature, thereby enhancing the understanding of circular CFDST short columns under compression.
Key Words
ABAQUS; axisymmetric model; CFDST; concrete; constitutive model
Address
Tuan-Dung Pham: School of Engineering, University of Aberdeen, King's College, Aberdeen, AB24 3UE, UK
Van-Minh Ngo: Faculty of Civil Engineering, University of Transport and Communications, 03 Cau Giay Street, Hanoi, Vietnam
Thai-Hoan Pham: Faculty of Building and Industrial Construction, Hanoi University of Civil Engineering, Hanoi, Vietnam
George Papazafeiropoulos: Department of Structural Engineering, School of Civil Engineering, National Technical University of Athens, Zografou, Athens 15780, Greece
Zhengyi Kong: Institute for Sustainable Built Environment, Heriot-Watt University, Edinburgh, UK
Quang-Viet Vu: Laboratory for Computational Civil Engineering, Institute for Computational Science and Artificial Intelligence, Van Lang University, Ho Chi Minh City, Vietnam; Faculty of Civil Engineering, School of Technology, Van Lang University, Ho Chi Minh City, Vietnam
Abstract
Exploring the nonlinear transient response of structures under external loads holds significant importance. Functionally graded materials (FGMs) and annular plates play a critical role in aerospace, defense, and other fields, but research on the nonlinear transient response of rotating FGM annular plates under explosive loading in hygro-thermal environments remains unexplored. First, in this paper, we formulate the viscoelastic foundation model using the Visco-Pasternak foundation theory. Subsequently, by integrating the first-order shear deformation theory (FSDT) and incorporating initial geometric imperfections, we derive the displacement field expressions. Thereafter, we establish the stress-strain relationship and present the constitutive equations. Finally, we obtain the governing equations through Hamilton's principle and solve them using the Galerkin method. In the numerical analysis section, the effects of geometric parameters, initial geometric defects, foundation stiffness, temperature, humidity coefficient, load amplitude, and load duration are systematically investigated.
Abstract
This paper focuses on investigating the axial bearing capacity of Reinforced Recycled Aggregate Concrete (RRAC)
Filled Square Steel Tube (RRACFSST) short columns. The research takes into account the double constraints of square steel tubes and steel cages, conducting a nonlinear simulation study on RRACFSST. The compressive bearing capacity of square steel pipe in nonlinear simulation is determined. The axial bearing capacity of RRACFSST short columns is analyzed using the limit analysis method and the Ferrule theory. A formula is proposed to calculate the axial bearing capacity of RRACFSST short columns, considering factors such as the width to thickness ratio of the steel tube, recycled coarse aggregate replacement rate, reinforcement ratio, and constrained effect coefficient. These influencing factors are also analyzed. The formula's accuracy and applicability are verified by comparing it with literature experimental values and finite element simulation values based on theoretical derivation. The research findings provide a theoretical basis for designing the axial compression bearing capacity of square steel tube RRAC short columns. Additionally, the study proposes a novel steel pipe-constrained RAC system, combining steel with RAC to enhance ductility, compressive strength, and seismic resistance, offering significant social and economic
benefits.
Address
Changjiang Liu: School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510006, China; Research Center of Complex Steel Structure Engineering Technology, Guangzhou University, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology, Guangzhou 510006, China
Yaojun Deng: School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510006, China
Jian Liu: School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510006, China; Research Center of Complex Steel Structure Engineering Technology, Guangzhou University, Guangzhou 510006, China
Chiyu Luo: Guangdong Architectural Design and Research Institute Co., LTD, Guangzhou 510010, China
Qigong Xu: Guangdong Jianke Architectural Design Institute Co., LTD, Guangzhou 510599, China
Guangen Zhou: Southeast Space Frame Group Co., LTD, Hangzhou, 311209, China
Wei Xiong: Guangzhou Design Institute Group Co., LTD, Guangzhou 510620, China
Hua Dong: China Construction Third Engineering Bureau Co., LTD, Wuhan 430064, China
Abstract
The assessment of existing bridges constitutes a serious challenge for the researchers since their safety evaluation is a complex task due to several sources of uncertainty affecting the knowledge process. In particular, a high level of uncertainties may arise in the case of prestressing systems requiring special investigation strategies and experimental technologies. The paper aims to investigate how the knowledge uncertainties influence the safety assessment of existing post-tensioned bridges using the semi-probabilistic approach. Uncertainties related to the knowledge process are described considering the number of tests, the confidence level assumed for the estimation of the problem parameters, and the measurement errors of in-situ tests. Results concerning a typical post-tensioned bridge are reported and the variability of the outcomes is discussed and compared with a reference case of "perfect knowledge". The main results of the study confirm the general robustness of the semi-probabilistic Eurocodes safety format and provide an overview of dispersion due to different choices regarding the number of tests and confidence level. The measurement errors may lead to significant underestimation of the computed structural capacity with respect to the reference one, up to -40% of the reference case considering standard confidence levels.
Key Words
existing post tensioned concrete bridges; knowledge uncertainties; Monte-Carlo simulation; safety format; semi-probabilistic approach
Address
Alberto Poeta, Fabio Micozzi, Laura Gioiella and Andrea Dall'Asta: SAAD School of Architecture and Design, University of Camerino, Viale della Rimembranza 63100, Ascoli Piceno, Italy
Abstract
Waste fire clay (WFC) was selected for use in this research study as a substitute for fine aggregate (FA) and cement in certain amounts. For this purpose, the amounts of FA and cement in the mixture were replaced with WFC (10%, 20%, 30%, 40% and 50%), while the effect of temperature on strength was also investigated. Regarding the temperature impact, variations of 24oC, 300oC, 600oC, and 900oC were taken into consideration. As a consequence of these alterations, the concrete mixture's flexural strength (FS), splitting tensile strength (STS), and compression strength (CS) were measured and assessed. Consequently, the investigations conducted on the test samples revealed that the CSs rose by up to 30% due to the substitution of WFC in the combination with FA. The rise rates are 11.11%, 16.31%, 19.03%, and 5.79%, respectively. The final mixture ratio of 50% exhibited a consistent reduction of 13.34% relative to the reference sample (34.57 MPa). When cement was added to the mixture in place of WFC, the CSs steadily dropped in comparison to the reference sample (34.57 MPa). The relative decrease rates are 6.74%, 13.65%, 30.14%, 42.26%, and 62.08%. The strength of the combination was shown to decrease with rising temperature values for both FA change and cement change. It was determined that the ultimate strength of concrete was achieved by a 30% substitution of WFC with FA, and a 20% substitution of WFC with cement. Comparative FE-SEM analyses were conducted on concrete that was substituted with FA and cement. FE-SEM analysis showed that increasing chamotte content resulted in denser microstructures with gel-like and acicular crystalline phases formed. The EDX results confirmed the presence of Si, Al and Ca as the main elements, indicating the co-existence of binding phases of the C-S-H and C-A-S-H type.
Key Words
cement; elevated temperature; fine aggregate; fire clay; SEM; waste
Address
Yasin Onuralp Özkiliç: Department of Civil Engineering, Faculty of Engineering, Necmettin Erbakan University, Konya, Turkey; Department of Technical Sciences, Western Caspian University, Baku, 1001, Azerbaijan
Memduh Karalar: Department of Civil Engineering, Faculty of Engineering, Zonguldak Bulent Ecevit University, Zonguldak 67100, Turkey
Ali İhsan Çelik: Department of Construction, Tomarza Mustafa Akincioglu Vocational School, Kayseri University, Kayseri, 38940, Turkey
Essam Althaqafi: Civil Engineering Department, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia
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