Abstract
This paper formulates a new integral shear deformation shell theory to investigate the free vibration response of carbon nanotube (CNT) reinforced structures with only four independent variables, unlike existing shell theories, which invariably and implicitly induce a host of unknowns. This approach guarantees traction-free boundary conditions without shear correction factors, using a non-polynomial hyperbolic warping function for transverse shear deformation and stress. By introducing undetermined integral terms, it will be possible to derive the motion equations with a low order of differentiation, which can facilitate a closed-form solution in conjunction with Navier's procedure. The mechanical properties of the CNT reinforcements are modeled to vary smoothly and gradually through the thickness coordinate, exhibiting different distribution patterns. A comparison study is performed to prove the efficacy of the formulated shell theory via obtained results from existing literature. Further numerical investigations are current and comprehensive in detailing the effects of CNT distribution patterns, volume fractions, and geometrical configurations on the fundamental frequencies of CNT-reinforced nanocomposite shells present here. The current shell theory is assumed to serve as a potent conceptual framework for designing reinforced structures and assessing their mechanical behavior.
Key Words
advanced reinforced nanocomposites; carbon nanotubes; free vibration; higher order shear deformation shell theory; indeterminate integral terms
Address
Mohammed Houssem Eddine Guerine: Artificial Intelligence Laboratory for Mechanical and Civil Structures, and Soil, Institute of Technology, University Center of Naama, BP 66, 45000 Naama, Algeria
Zakaria Belabed: Artificial Intelligence Laboratory for Mechanical and Civil Structures, and Soil, Institute of Technology, University Center of Naama, BP 66, 45000 Naama, Algeria; Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Department of Civil and Environmental Engineering, Lebanese American University, 309 Bassil Building, Byblos, Lebanon; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Sherain M.Y. Mohamed: Department of Mathematics, College of Science and Humanities, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
Saad Althobaiti: Department of Sciences and Technology, Ranyah University Collage, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia
Mahmoud M. Selim: Department of Mathematics, College of Science and Humanities, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
Abstract
After the mainshock, whether the train can be allowed to pass the bridges plays an important role in ensuring the transport of supplies and rescue works for example, in the "12 May" earthquake in China, after evaluation, the bridge was still used for transportation in rescue at a very slow speed, engineers usually evaluate whether the train can pass the bridge safely based on the experience, lacks sufficient calculation basis and does not fully consider the risk caused by aftershocks. To address this issue, this paper comprehensively considers the randomness of track irregularity, the randomness of aftershock intensity and other multiple random sources in train-bridge interaction system (TBIS). The sensitivity of train to various random parameters after earthquake is analyzed from the perspective of probability, the most sensitive random variable in this paper is PGA of aftershocks, both for bridge and trailer car, With the increase of epicentral distance, the sensitivity of PGA will decrease, and correspondingly, for trailer car, the sensitivity of other random variables will increase, research in this paper provides a basis for the subsequent random analysis of post-earthquake driving safety.
Key Words
aftershocks; rail irregularity; randomness of aftershock intensity; residual deformation; sensitivity
Address
Jincheng Tan, Xiang Liu, Han Zhao, Lizhong Jiang, Peidong Guo, Wangbao Zhou: School of Civil Engineering, Central South University, Changsha, 410075, China
Manman Chen: Department of Civil Engineering, Guangxi Polytechnic of Construction, Nanning, 530007, Guangxi, China
Ping Xiang: School of Civil Engineering, Central South University, Changsha, 410075, China; School of Civil and Architectural Engineering, Taishan University, Taian 271000, Shandong, China
Abstract
Bridge deterioration shows the change of bridge condition during its operation, and predicting bridge deterioration is
important for implementing predictive protection and planning future maintenance. However, in practical application, the raw inspection data of bridges are not continuous, which has a greater impact on the accuracy of the prediction results. Therefore, two kinds of bridge deterioration models are established in this paper: one is based on the traditional regression theory, combined
with the distribution fitting theory to preprocess the data, which solves the problem of irregular distribution and incomplete quantity of raw data. Secondly, based on the theory of Long Short-Term Memory (LSTM) Recurrent Neural Network (RNN), the network is trained using the raw inspection data, which can realize the prediction of the future deterioration of bridges through the historical data. And the inspection data of 60 prestressed concrete box girder bridges in Xiamen, China are used as an example for validation and comparative analysis, and the results show that both deterioration models can predict the deterioration of prestressed concrete box girder bridges. The regression model shows that the bridge deteriorates gradually, while
the LSTM-RNN model shows that the bridge keeps great condition during the first 5 years and degrades rapidly from 5 years to 15 years. Based on the current inspection database, the LSTM-RNN model performs better than the regression model because it has smaller prediction error. With the continuous improvement of the database, the results of this study can be extended to other bridge types or other degradation factors can be introduced to improve the accuracy and usefulness of the deterioration model.
Address
Gao Jing, Zhang Yao: School of Architecture and Civil Engineering, Xiamen University, China
Lin Ruiying: Xiamen Road and Bridge Engineering Investment Development Co. LTD, China
Abstract
In recent decades, the majority of studies have concentrated on the utilization of Steel Square Hollow Section (SHS) columns, with minimal attention given to reinforcing columns exhibiting inherent defects. This study addresses this gap by introducing initial vertical and horizontal defects at three distinct locations (top, middle, and bottom) and employing Carbon-FRP for reinforcement. The research investigates the dimensional and positional impacts of these defects on the axial behavior of SHS columns. A total of 29 samples, comprising 17 with defects, 11 strengthened, and 1 defect-free control, underwent examination. The study employed ABAQUS modeling and conducted experimental testing. Results revealed that defects located at different positions significantly diminished the load-bearing capacity and initial performance of the steel columns. Axial loading induced local buckling and lateral rupture, particularly at the defect side, in short columns. Notably, horizontal (across the column's height) defects in the middle led to the most substantial reduction in strength and load-bearing capacity. The axial compressive failure increased with the length-to-width ratio of the defect. Moreover, the application of four carbon fiber layers to strengthen the steel columns resulted in increased Energy Dissipation
and a delayed onset of local buckling in the face of axial ruptures.
Key Words
CFRP; defect; square hollow section; steel column; strengthening
Address
Omid Yousefi: Department of Civil Engineering, Nikshahr Branch, Islamic Azad University, Nikshahr, Iran
Amin Shabani Ammari: Faculty of Marine Engineering, Chabahar Maritime University, Shahid Rigi Ave, Chabahar, Iran
Abstract
Improving the blast resistance of structural establishments has become an imperative engineering commitment to prevent property damage and fatalities in terrorist incidents. This study investigates the effects of blast mass and stand-off distance on CFRP skin concrete core sandwich bunkers of varying thicknesses using ABAQUS/Explicit software with CONWEP functionality. The considered parameters include TNT masses of 1, 10, and 25 kg and stand-off distances of 0.1, 1, 2, and 2.5 meters on structures with 200, 250, and 500 mm core thicknesses. The study finds that there exists a declining response corresponding to the blasting mass reduction coupled with increases in the stand-off distance and core thickness. The 500 mm thick bunker sustains less damage compared to those with 200 mm and 250 mm core thicknesses. The sandwich configuration remains structurally advantageous vs. those without skins. The sandwich bunker with a 500 mm thick concrete core gives the best performance against the 10 kg TNT blast load with a 1 m standoff distance exhibiting a 22.8% reduction in damage vs. that without skins. Mathematical expressions are then formulated for predicting maximum von Mises stress, principal stress, and displacement of sandwich bunkers as functions of TNT masses, stand-off distances, and core thicknesses.
Key Words
blast resistance; CFRP skin; composite; concrete; CONWEP; finite elements analysis; sandwich bunker
Address
Mahmudul Hasan: Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia
Ahmad B.H. Kueh: Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia; UNIMAS Water Centre (UWC), Faculty of Engineering, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia
Abstract
In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and
low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.
Key Words
dynamic behavior; energy dissipation performance; filled thin-walled tubes; impact loading; porous metal
Address
Kunlong Tian, Chao Zhao, Yi Zhou, Xiong Peng, Qunyu Yang: School of Civil Engineering, Hunan University of Science and Technology, Taoyuan Road, Yuhu District, Xiangtan, China
Xingu Zhong: Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control, Taoyuan Road, Yuhu District, Xiangtan, China
Abstract
In recent years, the focus on vibration analysis of multilayer smart structures has attracted considerable attention in many engineering applications. In this work, vibration analysis of a three-layer microporous beam with a core amplified by a composite material reinforced with graphene platelets and two piezoelectric thin films is discussed. It is assumed that piezoelectric layers with a thickness of 0.01 core are very thin and the properties of the matrix and reinforcement vary in the thickness directions. The governing equations of motion are obtained using an energy approach and the method of numerical differential quadrature to solve them. The results of this work are compared to other research and there is good agreement between them. The influences of the volumetric weight fraction of graphene wafers, different graphene platelets distributions, porosity distribution, mass scale parameters and thin ratio of graphene platelets take into account the natural dimensionless frequencies of the micro-beam. The results of this study show that the symmetric distribution of graphene platelets based on the symmetric porosity distribution has a great influence on the natural frequencies without basic dimension of the micro-beam, while the shape ratios of graphene platelets do not have a significant influence on natural frequency changes.
Abstract
The smoothed particle hydrodynamics (SPH) method is a numerical technique used in dynamic analysis to simulate
the fluid-like behavior of materials under extreme conditions, such as those encountered in explosions or high velocity impacts. In SPH, fluid or solid materials are discretized into particles. These particles interact with each other based on certain smoothing kernels, allowing the simulation of fluid flows and predict the response of solid materials to shock waves, like deformation, cracking or failure. One of the main advantages of SPH is its ability to simulate these phenomena without a fixed grid, making it
particularly suitable for analyzing complex geometries. In this study, the structural damage to a masonry arch bridge subjected to blast loading was investigated. A high-fidelity micro-model was created and the explosives were modeled using the SPH approach. The Johnson-Holmquist II damage model and the Mohr-Coulomb material model were considered to evaluate the masonry and backfill properties. Consistent with the principles of the JH-II model, the authors developed a VUMAT code. The explosive charges (50 kg, 168 kg, 425 kg and 1000 kg) were placed in close proximity to the deck and pier of a bridge. The results showed that the 50 kg charges, which could have been placed near the pier by a terrorist, had only a limited effect on the piers. Instead, this charge caused a vertical displacement of the deck due to the confinement effect. Conversely, a 1000 kg TNT charge placed 100 cm above the deck caused significant damage to the bridge.
Key Words
blast load; damage; masonry bridge; numerical simulation; SPH
Address
Amin Bagherzadeh Azar: Institute of Earthquake Engineering and Disaster Management, Istanbul Technical University, ITU Ayazaga Campus, 34469 Maslak, Istanbul, Turkey
Ali Sari: Faculty of Civil Engineering, Istanbul Technical University, ITU Ayazaga Campus, 34469 Maslak, Istanbul, Turkey
