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CONTENTS
Volume 53, Number 3, November 10 2024
 


Abstract
Corrugated steel plates have attracted wide attention based on their superior shear buckling capacity. The shear buckling performance of steel or composite I-girders can be significantly improved by replacing the plane webs with corrugated steel webs. However, the differences in shear buckling evolution processes between plane steel webs and corrugated steel webs are rarely revealed in detail. Besides, the conventional analytical models are conservative in that the shear buckling capacity of composite I-girders with corrugated steel webs only considers the shear contribution of corrugated steel webs and ignores the concrete flange. For such insufficient research points mentioned above, this study reveals the shear buckling evolution processes of steel webs in detail by testing two composite I-girders, which possess corrugated steel webs and plane steel webs, respectively. The experimental results highlight the superiorities of the shear buckling of corrugated steel webs compared with plane steel webs. Based on the verified finite element models, the effects of initial imperfection modes, initial imperfection amplitudes, connection degrees, and steel flange-to-web thickness ratios on the shear buckling of composite I-girders with corrugated steel webs are comprehensively investigated. Afterward, considering the shear capacity of the concrete flange and the influence of initial imperfections, connection degrees, and steel flange-to-web thickness ratios, the improved analytical model with reasonable efficiency is proposed to estimate the shear buckling resistance of composite I-girders with corrugated steel webs.

Key Words
analytical model; composite I-girders; corrugated steel webs; finite element analysis; shear buckling

Address
Zijian Bi and Guotao Yang:School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Abstract
The reinforcement technology for rib-to-deck weld cracks in orthotropic steel deck should be both efficient and lightweight, particularly for multi-crack reinforcement within a single compartment, to avoid adding excessive weight that could affect the structural stress. In this paper, a lightweight reinforcement technology using ribbed angle steel was proposed. By conducting tests and numerical simulations, the reinforcement effect of ribbed angle steel for rib-to-deck weld cracks was analyzed, with a focus on the influence of stiffener thickness, spacing, and arrangement on the reinforcement effect. Reasonable parameters were then suggested. The effectiveness of the proposed technology and parameters was demonstrated through a real bridge simulation. The results show that ribbed angle steel, compared to angle steel, offers effective reinforcement while being lighter in weight. The failure behaviour of ribbed angle steel is consistent with that of plain angle steel, and the quality of adhesive layer construction should be strictly controlled during actual implementation. Increasing the thickness of the stiffeners can enhance the reinforcement effect, while increasing the spacing between stiffeners can reduce the reinforcement effect. When using ribbed angle steel with 4 mm thick angle steel, 6 mm thick stiffeners, and 20 mm stiffener spacing to reinforce cracks, the reinforcement effect is superior to that of 10 mm plain angle steel.

Key Words
crack reinforcement technology; orthotropic steel deck; parameter analysis; rib-to-deck weld crack; ribbed angle steel

Address
Yuqiang Gao, Zhongqiu Fu, Xuekun Cao and Bohai Ji:College of Civil and Transportation Engineering, Hohai University, No. 1 Xikang Road, Nanjing, China

Abstract
This research concentrates on the exploration of the free vibration of a multi-walled carbon nanotube (MWCNT)- reinforced semi-ellipsoidal composite dome. A glass fiber-reinforced composite laminated dome without and with MWCNT reinforcement is considered for numerical analysis. Free vibration analysis is carried out numerically using ANSYS to determine the natural frequencies and mode shapes at various boundary conditions. In addition, the efficiency of the numerical analysis has been proven by conducting an experimental examination on a prototype dome with and without MWCNT reinforcement and comparing the results with those obtained numerically and experimentally. Parametric studies such as the influence of MWCNT wt.%, the aspect ratio of the dome, slenderness ratio of the dome, etc., with and without MWCNT reinforcement is performed to determine the dynamic behaviour. It was noted that clamped end conditions of the hybrid composite domes provide the highest natural frequencies among the numerous end conditions considered. Also, the hybrid composite dome with 1.5 wt.% CNT reinforcement yields the highest natural frequencies at all the end conditions, beyond which the amalgamation of CNT content decreases the natural frequencies of the structures. Furthermore, composite dome "S1" with 0° orientation and "S4" with 45° orientation yields the highest and the lowest natural frequencies.

Key Words
aspect ratio; multi-walled carbon nanotube; semi-ellipsoidal composite dome; stacking sequences

Address
Hariharan Elangovan:School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India – 63201

Surekha Gnanasekar:School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India – 63201

Venugopal Barathan:Enercon Wind Energy Pvt Ltd, Bangalore, India

Senthamizh Selvan Samuel:School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India – 632014

Mutra Rajasekhara Reddy:School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India – 632014

Vasudevan Rajamohan:School of Mechanical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India – 632014

Abstract
Biochar, as a lightweight aggregate, can be partially incorporated into concrete to exert filling and internal curing effects, thereby improving the mechanical properties of biochar concrete to some degree, and becoming a potential carbon capture and storage technology. However, due to the inherently high porosity of biochar's microstructure, biochar concrete confronts with certain challenges such as low strength, poor corrosion resistance, instability and etc. Thereby, the FRP tube is proposed to enhance the biochar concrete in this study, then FRP confined biochar concrete is formed. The axial compressive test for FRP confined biochar concrete column specimens, with various parameters including FRP tube thickness, the volume content and water absorption rate of biochar, was performed. The axial load-strain curves, transverse strain versus axial strain responses, ultimate stress, ultimate strain, development of transverse strain, and etc. of specimens were emphatically analyzed. The results showed that under the same biochar volume content and water absorption, the ultimate compressive strength of FRP confined biochar concrete specimens increased by 490.4% to 563.3% compared to unconfined counterparts. With increasing volume content of biochar in biochar concrete, the ultimate strength of confined specimens decreased while the ultimate strain increased. Besides, an increase in water absorption rate of biochar led to an increase in the ultimate strength of confined specimens but a decrease in the ultimate strain. Additionally, an increase in the layers of FRP tube improved the secondary stiffness of confined specimens. The transverse strain-axial strain curve exhibited no obvious transition point between the elastic segment and the linear segment, indicating good synergy between FRP tubes and biochar concrete. Finally, some existing FRP confined concrete ultimate strength and ultimate strain models were used to evaluate the ultimate strength and ultimate strain of FRP confined biochar concrete.

Key Words
biochar concrete; FRP; ultimate strain; ultimate stress; water absorption

Address
Jin-Ben Gu:1)College of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China
2)State Key Laboratory of Green Building, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China

Yu-Han Chen:College of Civil Engineering, Xi

Abstract
This article investigates the effect of porosity on the buckling and postbuckling characteristics of sandwich toroidal shell segments (TSSs) with graphene origami (GOri)-enabled auxetic core and porous functionally graded carbon nanotubes (FG-CNT)-reinforced face sheets. The TSSs are subjected to combined axial compression and radial pressure and supported by an elastic foundation. The auxetic property of the core layer can be effectively tuned by the content and folding degree of GOri, and the material characteristics are estimated using genetic programming (GP)-assisted micromechanical models. CNTs are embedded within a polymer matrix by uniform or FG distribution (UD, FG-X, and FG-O) throughout the shell thickness, and three distinct porosity distribution patterns are considered for the face sheets: uniform, symmetric, and asymmetric. The nonlinear equilibrium equations of the longitudinally shallow shells are formulated using the von Karman-Donnel shell theory in conjunction with Stein and McElman approximations while considering the Winkler-Pasternak type elastic foundation to simulate the interaction between the shell and elastic foundation. A three-term solution for deflection under simply supported boundary conditions is employed, with the Galerkin method utilized to derive the nonlinear load-deflection relation. The effectiveness of the proposed approach is confirmed through comparative analysis with existing literature, demonstrating good agreement with theoretical results. Extensive parametric studies are subsequently carried out to thoroughly investigate the impacts of various parameters such as the porosity coefficients and distribution patterns, load-proportional parameters, presence of an elastic foundation, and geometric properties on the buckling and postbuckling performance of TSSs under combined mechanical loads.

Key Words
buckling and postbuckling; carbon nanotube-reinforced composite; combined mechanical loads; graphene origami-enabled auxetic metamaterial core; porosity; toroidal shell segment

Address
Farzad Ebrahimi:Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

Mohammadhossein Goudarzfallahi:Mechanical Engineering Department, Science and Research branch, Islamic Azad University, Tehran, Iran

Ali Alinia Ziazi:Mechanical Engineering Department, Science and Research branch, Islamic Azad University, Tehran, Iran

Abstract
Machine-learning techniques have significantly advanced in structural design, offering efficient, precise, and dominance over conventional methods. FRP bars, with favorable physical attributes, are extensively used as alternative reinforcement in various structural members. Shear modeling in these members gains importance due to the brittle nature of shear failure, leading to conservative shear strength estimates in current codes. Numerous design parameters, such as crosssection dimensions, shear span to effective depth ratio, concrete compressive strength, and axial stiffness of FRP bars, influence shear strength. Consequently, efficiently estimating the shear capacity of these members using traditional mathematical approaches is exceptionally challenging. This study aims to develop and assess the effectiveness of Artificial Neural Networks (ANNs) - Multilayer Perceptron (MPNN) and General Regression (GRNN) - and Support Vector Machine (SVM) with Radial Bias Function (RBF) techniques in predicting concrete shear capacity of FRP-reinforced members without stirrups. Models' findings, along with various code provisions, compared with shear testing outcomes of 555 specimens, revealed GRNN, SVM, and MPNN consecutively outperformed existing code formulas in performance, efficiency, and precision. The parametric study showed that GRNN accurately delineates the interaction of design variables on shearstrength, with a greater potential to forecast variable behavior despite its complexity and sensitivity.

Key Words
artificial neural networks; code shear provisions; concrete shear strength; FRP-reinforced beams; support vector machine

Address
Mohamed A. El Zareef:1)Civil Engineering Dept., College of Engineering and Architecture, Umm Al-Qura University, Makkah, Saudi Arabia
2)Structural Engineering Department, Faculty of Engineering, Mansoura University, Mansoura, Dakahlia 35516, Egypt

Mohamed Ghalla:Civil Engineering Department, Faculty of Engineering, Kafrelsheikh University, Kafrelsheikh, Egypt

Jong Wan Hu:1)Department of Civil and Environmental Engineering, Incheon National University, Incheon 22012, South Korea
2)Incheon Disaster Prevention Research Center, Incheon National University, Incheon 22012, South Korea

Ahmed M. Elbisy:Civil Engineering Dept., Faculty of Engineering and Material Sciences, German University in Cairo (GUC), Cairo 11835, Egypt

Abstract
The prefabricated eccentrically braced frames (PEBFs) are a novel structural system that incorporates semi-rigid connections into eccentrically braced frames (EBFs). This innovation significantly improves construction efficiency and facilitates the replacement of damaged members after an earthquake, reducing maintenance costs and time. This study tested the failure mechanism and feasibility of post-earthquake replacement of this type of structure under low cyclic-reversed loading test on single-story plane specimens. The results indicate that the structural system has great energy dissipation and bearing capacity. The failure mechanism of PEBFs occurs at the connection of the end plate of the link, with no evident buckling deformations or cracks in other components, thus achieving the original design objective of concentrating plastic deformation or damage in the removable component. The experimental verification of the feasibility of replacing the link after an earthquake shows that the structural system can still maintain excellent seismic behaviour. Successively, the ultimate load-bearing capacity formula for PEBFs, and the relationship between the plastic rotation angle of the link and inter-story drift were established and validated by the test. Finally, a validated 3-D finite element model was established, and the parameter analysis was conducted to further explore the factors affecting the seismic behaviour of PEBFs.

Key Words
eccentrically braced frames; failure mechanism; removable link; seismic behaviour; semi-rigid connection

Address
Chongyang Ye:School of Civil Engineering, Xi'an University of Architecture & Technology, Xi'an, Shaanxi 710055, P.R. China

Jianyang Xue:1)School of Civil Engineering, Xi'an University of Architecture & Technology, Xi'an, Shaanxi 710055, P.R. China
2)Key Lab of Structural Engineering and Earthquake Resistance, Ministry of Education (XAUAT), Xi'an, Shaanxi 710055, P.R. China

Xinwu Wang:Key Lab of Structural Engineering and Earthquake Resistance, Ministry of Education (XAUAT), Xi'an, Shaanxi 710055, P.R. China

Xin Bu:Henan International Joint Laboratory of New Civil Engineering Structure, Luoyang Institute of Science and Technology, Luoyang, Henan 471000, P.R. China

Abstract
The pulsating fluid transported inside the pipe conveying fluid and external forced excitation can significantly affect its vibration behavior. Currently, research on pipe conveying fluid is mostly focused on forced resonance and parametric resonance, and there is no research on the combined resonance of graphene platelets reinforced metal foams (GPLRMF) pipe. To make up for this deficiency, this paper delves into the issue of combination resonance in GPLRMF fluid conveying pipe under multiple sources of excitation. Based on Euler-Bernoulli beam theory, the control equation of the system is derived and then discretized. Subsequently, the oscillation response is solved using the method of variable amplitude (MVA). The accuracy of this research is confirmed by comparing it with existing literature. The results indicate that the response curve under combination resonance exhibits a complex mechanism. Depending on various influencing factors such as damping, phase angle and outside incentive, the response curve of the pipe displays stable/unstable solutions, jumps, hysteresis and other phenomena. Additionally, temperature load, fluctuating velocity and material properties can also exert diverse impacts on the bifurcation curve.

Key Words
chaotic dynamics; combination resonance; fluid conveying pipe; nonlinear vibration; pulsating fluid

Address
Yu-Jie He and Gui-Lin She:College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China


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