Abstract
In order to establish a dynamic model test method of bridge pylons subjected to ocean waves, the similarity method of hydroelastic model test for bridge pylons were analyzed systematically, and a model design and production method was proposed. Using this method, a dynamic test model of a bridge pylon was made, and then a free vibration test on the model structure and a dynamic response test of the model structure under wave actions were conducted in a wave flume. The results of the free vibration test show that the primary natural frequencies of the structure by the model test are close to the design frequencies of the prototype structure, indicating that the dynamic characteristics of the bridge pylon are well simulated by the model structure. The results of the dynamic response test show that wave induced base shear forces and motion responses on the model structure are consistent with the numerical results of the prototype structure. The model test results confirm that the
proposed model test design method is feasible and applicable. It has application and reference significances for model testing studies of such marine bridge structures.
Key Words
bridge pylon; dynamic model test; model design; similarity method; wave action
Address
Chengxun Wei, Songze Yu, Wenjing Wang: School of Civil Engineering, Guangxi University of Science and Technology, 268 Donghuan-ro, Liuzhou City, Guangxi Province, China
Jiang Du: Offshore Wind Design & Research Department, Beijing Goldwind Science & Creation Windpower Equipment Co.,
19 Kangding Street, Beijing Economic and Technological Development Zone, Beijing, China
Abstract
Broad studies have addressed the issue of structural element damage identification, however, rubber bearing, as a key
component of load transmission between the superstructure and substructure, is essential to the operational safety of a bridge, which should be paid more attention to its health condition. However, regarding the limitations of the traditional bearing damage detection methods as well as few studies have been conducted on this topic, in this paper, inspired by the model updating-based structural damage identification, a two-stage bearing damage identification method has been proposed. In the first stage, we deduce a novel bearing damage localization indicator, called element relative MSE, to accurately determine the bearing damage
location. In the second one, the prior knowledge of bearing damage localization is combined with sailfish optimization (SFO) to perform the bearing damage estimation. In order to validate the feasibility, a numerical example of a 5-span continuous beam is introduced, also the noise robustness has been investigated. Meanwhile, the effectiveness and engineering applicability are further verified based on an experimental simply supported beam and actual engineering of the I-40 Bridge. The obtained results are good, which indicate that the proposed method is not only suitable for simple structures but also can accurately locate the
bearing damage site and identify its severity for complex structure. To summarize, the proposed method provides a good
guideline for the issue of bridge bearing detection, which could be used to reduce the difficulty of the traditional bearing failure detection approach, further saving labor costs and economic expenses.
Key Words
bearing damage detection index; bridge bearing damage identification; element relative modal strain energy;
sailfish optimization; structural heath monitoring
Address
Minshui Huang, Chang Sun, Chunyan Xiang, Zihao Wan, Jianfeng Gu: School of Civil Engineering and Architecture, Wuhan Institute of Technology, Wuhan 430073, China; Hubei Provincial Engineering Research Center for Green Civil Engineering Materials and Structures, Wuhan, 430073, China
Zhongzheng Ling: Tongji Architectural Design (Group) Co., Ltd., Shanghai 200092, China
Yongzhi Lei: Centre for Infrastructural Monitoring and Protection, School of Civil and Mechanical Engineering, Curtin University, Kent Street, Bentley, WA 6102, Australia
Abstract
This article presents an analytical approach to explore the bending behaviour of of two-dimensional (2D) functionally
graded (FG) nanobeams based on a two-variable higher-order shear deformation theory and nonlocal strain gradient theory. The kinematic relations are proposed according to novel trigonometric functions. The material gradation and material properties are varied along the longitudinal and the transversal directions. The equilibrium equations are obtained by using the virtual work principle and solved by applying Navier's technique. A comparative evaluation of results against predictions from literature demonstrates the accuracy of the proposed analytical model. Moreover, a detailed parametric analysis checks for the sensitivity
of the bending and stresses response of (2D) FG nanobeams to nonlocal length scale, strain gradient microstructure scale,
material distribution and geometry.
Key Words
2D FG beams; deflections and stresses; higher order nonlocal strain gradient theory; navier's solution
Address
Aicha Bessaim. Mohammed Sid Ahmed Houari: Laboratoire d
Abstract
This study examines the two-level behavior of the toggle brace damper within a steel frame having a yielding pipe damper and rotational friction damper. The proposed system has two kinds of fuse for energy dissipation in two stages. In this mechanism, rotational friction damper rather than hinged connection is used in toggle brace system, connected to a pipe damper with a limited gap. In order to create a gap, bolted connection with the slotted hole is used, such that first a specific movement of the rotational friction damper solely is engaged but with an increase in movement, the yielding damper is also involved. The performance of the system is such that at the beginning of loading the rotational friction damper, as the first fuse, absorbs energy and with increasing the input load and further movement of the frame, yielding damper as the second fuse, along with rotational friction damper would dissipate the input energy. The models created by ABAQUS are subjected to cyclic and seismic loading. Considering the results obtained, the flexibility of the hybrid two-level system is more comparable to the conventional toggle brace damper. Moreover, this system sustains longer lateral displacements. The energy dissipation of these two systems is modeled in multi-story frames in SAP2000 software and their performance is analyzed using time-history analysis. According to the results, permanent relocations of the roof in the two-level system, in comparison with toggle brace damper system in 2, 5, and 8-story building frames, in average, decrease by 15, 55, and 37% respectively. This amount in a 5-story building frame under the earthquakes with one-third scale decreases by 64%.
Key Words
energy dissipation; passive control; rotational friction damper; toggle brace; two-level control system; yielding pipe damper
Address
Ata Abdollahpour: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran
Seyed Mehdi Zahrai: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran; Department of Civil Engineering, Faculty of Engineering, University of Ottawa, Canada
Abstract
In practical engineering such as aerial refueling pipes, the boundary of the fluid-conveying pipe is difficult to be
completely immovable. Pipes under movable and immovable boundaries are controlled by different dominant nonlinear factors, where the boundary mobility will affect the nonlinear dynamic characteristics, which should be focused on for adopting different strategies for vibration suppression and control. The nonlinear dynamic instability characteristics of functionally graded fluidconveying
pipes lying on a viscoelastic foundation under movable and immovable boundary conditions are systematically studied for the first time. Nonlinear factors involving nonlinear inertia and nonlinear curvature for pipes with a movable
boundary as well as tensile hardening and nonlinear curvature for pipes with an immovable boundary are comprehensively considered during the derivation of the governing equations of the principal parametric resonance. The stability boundary and amplitude-frequency bifurcation diagrams are obtained by employing the two-step perturbation- incremental harmonic balance method (TSP-IHBM). Results show that the movability of the boundary of the pipe has a great influence on the vibration amplitude, bifurcation topology, and the physical meanings of the stability boundary due to different dominant nonlinear factors. This research has guidance significance for nonlinear dynamic design of fluid-conveying pipe with avoiding in the instability regions.
Address
Zhoumi Wang: School of Aeronautics Science and Engineering, Beihang University, Beijing 100191, China
Yiru Ren: State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, Hunan 410082, China
Qingchun Meng: School of Aeronautics Science and Engineering, Beihang University, Beijing 100191, China
Abstract
This study investigates the free vibration and buckling analyses of isotropic curved plate structures fixed at all ends. The Kirchhoff-Love Plate Theory (KLPT) and Finite Element Method (FEM) are employed to model the curved structure. In order to perform the finite element analysis, a four-node quadrilateral element with 5 degrees of freedom (DOF) at each node is utilized. Additionally, the drilling effect (oz) is considered as minimal to satisfy the DOF of the structure. Lagrange's equation of motion is used in order to obtain the first ten natural frequencies and the critical buckling values of the structure. The effects of various radii of curvatures and aspect ratio on the natural frequency and critical buckling load values for the single-bay and twobay curved frames are investigated within this scope. A computer code based on finite element analysis is developed to perform free vibration and buckling analysis of curved plate frames. The natural frequency and critical buckling load values of the present study are compared with ANSYS R18.2 results. It has been concluded that the results of the present study are in good agreement with ANSYS results for different radii of curvatures and aspect ratio values of both single-bay and two-bay structures.
Key Words
buckling; curved plate frame; finite element method; free vibration; multi-bay plates
Address
Oguzhan Das: Department of Aeronautics Sciences, Air NCO Higher Vocational School, National Defence University, 35415, Izmir, Turkey; The Graduate School of Natural and Applied Sciences, Dokuz Eylül University, Tinaztepe Campus, Buca, Izmir, 35390, Turkey
Hasan Ozturk: Department of Mechanical Engineering, Dokuz Eylül University, Tinaztepe Campus, Buca, Izmir, 35390, Turkey
Can Gonenli: Department of Machine Drawing and Construction, Ege University, 35100, Izmir, Turkey
Abstract
Long-termly used in water supply, an underground concrete pipe is easily subjected to the coupled action of pressure loading and flowing water, which can cause the chemo-mechanical damage of the pipe, resulting in its premature failure and lifetime reduction. Based on the leaching characteristics and damage mechanism of concrete pipe, this paper proposes a coupled chemo-mechanical damage and failure model of underground concrete pipe for water supply, including a calcium leaching model, mechanical damage equation and a failure criterion. By using the model, a numerical simulation is performed to analyze the failure process of underground concrete pipe, such as the time-varying calcium concentration in concrete, the thickness variation of pipe wall, the evolution of chemo-mechanical damage, the distribution of concrete stress on the pipe and the lifetime of the pipe. Results show that, the failure of the pipe is a coupled chemo-mechanical damage process companied with calcium leaching. During its damage and failure, the concentrations of calcium phase in concrete decrease obviously with the time, and it can cause an increase in the chemo-mechanical damage of the pipe, while the leaching and abrasion induced by flowing water can lead to the boundary movement and wall thickness reduction of the pipe, and it results in the stress redistribution on the pipe section, a premature failure and lifetime reduction of the pipe.
Address
Xiang-nan Li, Xiao-bao Zuo, Yu-xiao Zou: Department of Civil Engineering, Nanjing University of Science & Technology, Nanjing 210094, China
Yu-juan Tang: School of Civil Engineering, Yangzhou Polytechnic College, Yangzhou 225009, China
