Abstract
The present study conducts a thorough analysis of thermal vibrations in functionally graded porous nanocomposite
beams within a thermal setting. Investigating the temperature-dependent material properties of these beams, which continuously vary across their thickness in accordance with a power-law function, a finite element approach is developed. This approach utilizes a nonlocal strain gradient theory and accounts for a linear temperature rise. The analysis employs four different patterns of porosity distribution to characterize the functionally graded porous materials. A novel two-variable shear deformation beam
nonlocal strain gradient theory, based on trigonometric functions, is introduced to examine the combined effects of nonlocal stress and strain gradient on these beams. The derived governing equations are solved through a 3-nodes beam element. A comprehensive parametric study delves into the influence of structural parameters, such as thickness ratio, beam length, nonlocal scale parameter, and strain gradient parameter. Furthermore, the study explores the impact of thermal effects, porosity distribution forms, and material distribution profiles on the free vibration of temperature-dependent FG nanobeams. The results reveal the substantial influence of these effects on the vibration behavior of functionally graded nanobeams under thermal
conditions. This research presents a finite element approach to examine the thermo-mechanical behavior of nonlocal
temperature-dependent FG nanobeams, filling the gap where analytical results are unavailable.
Key Words
buckling; finite element method; functionally graded materials; nonlocal strain gradient theory; porous
nanobeams; thermal effect; variational formulation
Address
Tarek Merzouki: LISV, University of Versailles Saint-Quentin, 10-12 avenue de l
Abstract
recent years, an increasing number of experimental studies have shown that the practical application of mature
active control systems requires consideration of robustness criteria in the design process, including the reduction of tracking errors, operational resistance to external disturbances, and measurement noise, as well as robustness and stability. Good uncertainty prediction is thus proposed to solve problems caused by poor parameter selection and to remove the effects of dynamic coupling between degrees of freedom (DOF) in nonlinear systems. To overcome the stability problem, this study develops an advanced adaptive predictive fuzzy controller, which not only solves the programming problem of determining system stability but also uses the law of linear matrix inequality (LMI) to modify the fuzzy problem. The following parameters are used to manipulate the fuzzy controller of the robotic system to improve its control performance. The simulations for system
uncertainty in the controller design emphasized the use of acceleration feedback for practical reasons. The simulation results also show that the proposed H controller has excellent performance and reliability, and the effectiveness of the LMI-based method is also recognized. Therefore, this dynamic control method is suitable for seismic protection of civil buildings. The objectives of this document are access to adequate, safe, and affordable housing and basic services, promotion of inclusive and sustainable urbanization, implementation of sustainable disaster-resilient construction, sustainable planning, and sustainable management of human settlements. Simulation results of linear and non-linear structures demonstrate the ability of this method to identify structures and their changes due to damage. Therefore, with the continuous development of artificial intelligence and fuzzy theory, it seems that this goal will be achieved in the near future.
Key Words
artificial intelligence; evolved grey; fuzzy neural network LMI control; improved optimal control performance; linearization method; resilient and sustainable infrastructures
Address
Z.Y. Chen, Yahui Meng, Ruei-Yuan Wang: School of Science, Guangdong University of Petrochem Technology, Maoming City, Kuan-Du Avenue, No. 139, 525000, PR China
Timothy Chen: School of Science, Guangdong University of Petrochem Technology, Maoming City, Kuan-Du Avenue, No. 139, 525000, PR China; Division of Engineering and Applied Science, Caltech, CA 91125, USA
Abstract
The prediction of VIV amplitude is essential for the design and fatigue life estimation of steel tubes in tubular transmission towers. Limited to costly and time-consuming traditional experimental and computational fluid dynamics (CFD) methods, a machine learning (ML)-based method is proposed to efficiently predict the VIV amplitude of steel tubes in transmission towers. Firstly, by introducing the first-order mode shape to the two-dimensional CFD method, a simplified response analysis method (SRAM) is presented to calculate the VIV amplitude of steel tubes in transmission towers, which enables to build a dataset for training ML models. Then, by taking mass ratio M*, damping ratio o, and reduced velocity U* as the input variables, a Kriging-based prediction method (KPM) is further proposed to estimate the VIV amplitude of steel tubes in transmission towers by combining the SRAM with the Kriging-based ML model. Finally, the feasibility and effectiveness of the proposed methods are demonstrated by using three full-scale steel tubes with C-shaped, Cross-shaped, and Flange-plate joints, respectively. The results show that the SRAM can reasonably calculate the VIV amplitude, in which the relative errors of VIV maximum amplitude in three examples are less than 6%. Meanwhile, the KPM can well predict the VIV amplitude of steel tubes in transmission towers within the studied range of M*, o and U*. Particularly, the KPM presents an excellent capability in estimating the VIV maximum amplitude by using the reduced damping parameter SG.
Address
Jiahong Li: School of Civil Engineering, Chongqing University, Chongqing, China
Tao Wang: School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China; Chongqing Research Institute of Harbin Institute of Technology, Harbin Institute of Technology, Chongqing, China
Zhengliang Li: School of Civil Engineering, Chongqing University, Chongqing, China
Abstract
In recent years, China's high-speed railway (HSR) line continues to expand into seismically active regions. Analyzing the features of earthquake rail irregularity is crucial in this situation. This study first established and experimentally validated a finite element (FE) model of bridge-track. The FE model was then combined with earthquake record database to generate the earthquake rail irregularity library. The sample library was used to construct a model of desired earthquake rail irregularity based on signal processing (SFT) and hypothesis principle. Finally, the effects of random pier height and random span number on desired irregularity were analyzed. Herein, an equivalent method of calculating earthquake rail irregularities for random structures was proposed. The results of this study show that the amplitude of desired irregularity is found to increase with increasing pier height. When calculating the desired irregularity of a structure with unequal pier heights, the structure can be regarded as that with equal pier heights (taking the largest pier height). For a structure with the span number large than 9, its desired irregularity can be considered equal to that of a 9-span structure. For the structures with both random pier heights and random span number, their desired irregularities are obtained by equivalent calculations for pier height and span number, respectively.
Key Words
earthquake rail irregularity; high-speed railway; post-earthquake operation; random earthquake; structural randomization
Address
Jian Yu: School of Civil Engineering, Central South University, Changsha 410075, China
Lizhong Jiang, Wangbao Zhou: School of Civil Engineering, Central South University, Changsha 410075, China; National Engineering Laboratory for High-Speed Railway Construction, Changsha 410075, China
Abstract
Poorly designed reinforced concrete (RC) columns of actual moment-resisting frame (MRF) buildings can undergo Axial Compression Ratios (ACR) so high as their demand exceeds their capacity, even for serviceability gravity load combinations, this lack commonly leads to insufficient seismic strength. Nonetheless, many seismic design codes do not specify limits for ACR. The main contribution of this research is to investigate the need to limit the ACR in seismic design. For this purpose, three prototype 6 and 11-story RC MRF buildings are analyzed in this paper, these buildings have columns undergoing excessive ACR, according to the limits prescribed by standards. To better that situation, three types of alterations are performed: retrofitting the abovementioned overloaded columns by steel jacketing, increasing the concrete strength, and reducing the number of stories. Several finite element analyses are conducted using the well-known software SAP2000 and the results are used for further calculations. Code-type and pushover analyses are performed on the original and retrofitted buildings, the suitability of the other modified buildings is checked by code-type analyses only. The obtained results suggest that ACR is a rather reliable indicator of the final building strength, hence, apparently, limiting the ACR in the standards (for early stages of design) might avoid unnecessary verifications.
Address
Sergio Villar-Salinas: Civil and Environmental Engineering Department, Universidad Tecnológica de Bolívar, Campus Tecnológico km 1 Vía Turbaco, 130011, Cartagena de Indias, Colombia
Sebastián Pacheco: Engineering/Research Department, PCEM SAS, Diag. 31 # 54-215, Santa Lucía, cc. Ronda Real of. 507,
130006, Cartagena de Indias, Colombia
Julián Carrillo: Department of Civil Engineering, Universidad Militar Nueva Granada, Carrera 11 No. 101-80, Edificio F, Piso 2, 49300, Bogotá D.C., Colombia
Francisco López-Almansa: Department of Architecture Technology, Universitat Politècnica de Catalunya-BarcelonaTech (UPC), 08028, Barcelona, Spain
Abstract
Fiber Reinforced Polymer (FRP) bars have now been widely adopted as an alternative to traditional steel reinforcements in infrastructure and civil industries worldwide due variety of merits. This paper presents a numerical methodology to investigate FRP bar-reinforced beam-column joint behavior under quasi-static loading. The proposed numerical model is validated with test results considering load-deflection behavior, damage pattern at beam-column joint, and strain variation in reinforcements, wherein the results are in agreement. The numerical model is subsequently employed for parametric investigation to enhance the end-span beam-column joint performance using different joint reinforcement systems. To reduce the manufacturing issue of bend in the FRP bar, the headed FRP bar is employed in a beam-column joint, and performance was investigated at different column axial loads. Headed bar-reinforced beam-column joints show better performance as compared to beam-column joints having an L-bar in terms of concrete damage, load-carrying capacity, and joint shear strength. The applicability and efficiency of FRP bars at different story heights have also been investigated with varying column axial loads.
Key Words
Beam-Column Joint; End Span Joint; FE analysis; GFRP bar; headed bar; RC structure
Address
Md. Muslim Ansari and Ajay Chourasia: Structural Engineering, CSIR- Central Building Research Institute, Roorkee, 247667, India
Abstract
This paper suggests an analytical approach to investigate the free vibration and stability of functionally graded (FG) beams with both perfect and imperfect characteristics using a quasi-3D higher-order shear deformation theory (HSDT) with
stretching effect. The study specifically focuses on FG beams resting on variable elastic foundations. In contrast to other shear deformation theories, this particular theory employs only four unknown functions instead of five. Moreover, this theory satisfies the boundary conditions of zero tension on the beam surfaces and facilitates hyperbolic distributions of transverse shear stresses without the necessity of shear correction factors. The elastic medium in consideration assumes the presence of two parameters,
specifically Winkler-Pasternak foundations. The Winkler parameter exhibits variable variations in the longitudinal direction, including linear, parabolic, sinusoidal, cosine, exponential, and uniform, while the Pasternak parameter remains constant. The effective material characteristics of the functionally graded (FG) beam are assumed to follow a straightforward power-law distribution along the thickness direction. Additionally, the investigation of porosity includes the consideration of four different types of porosity distribution patterns, allowing for a comprehensive examination of its influence on the behavior of the beam. Using the virtual work principle, equations of motion are derived and solved analytically using Navier's method for simply supported FG beams. The accuracy is verified through comparisons with literature results. Parametric studies explore the impact of different parameters on free vibration and buckling behavior, demonstrating the theory's correctness and simplicity.
Abstract
This paper presents a significant contribution to aided design by conducting an analytical examination of geometric
links with the aim of establishing criteria for assessing an analogy measure of the extrinsic geometric and kinematic
characteristics of the Variable Compression Ratio (VCR) engine with a Geared Mechanism (GBCM) in comparison to the
existing Fixed Compression Ratio (FCR) engine with a Standard-Reciprocating Crankshaft configuration. Employing a
mechanical approach grounded in projective computational methods, a parametric study has been conducted to analyze the kinematic behavior and geometric transformations of the moving links. The findings indicate that in order to ensure equivalent extrinsic behavior and maintain consistent input-output performance between both engine types, precise adjustments of intrinsic geometric parameters are necessary. Specifically, for a VCR configuration compared to an FCR configuration, regardless of compression ratio and gearwheel radius, for the same crankshaft ratios and stroke lengths, it is imperative to halve lengths of connecting rods, and crank radius. These insights underscore the importance of meticulous parameter adjustment in achieving comparable performance across different engine configurations, offering valuable implications for design optimization.
Address
Amir Sakhraoui: National Engineers School of Tunis, Department of Mechanical Engineering, LR-11-ES19 Applied Mechanics and Engineering Laboratory (LR-MAI), University of Tunis El Manar, Tunisia,1002, Tunis
Fayza Ayari: National Higher School of Engineers of Tunis (ENSIT), University of Tunis, 99/UR/11-46, 1002, Tunisia
Maroua Saggar: Mechanical Laboratory of Sousse, Private Central Polytechnic School of Tunis, Centrale University, Tunis, Tunisia
Rachid Nasri: National Engineers School of Tunis, Department of Mechanical Engineering, LR-11-ES19 Applied Mechanics and Engineering Laboratory (LR-MAI), University of Tunis El Manar, Tunisia,1002, Tunis
