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CONTENTS
Volume 71, Number 6, September25 2019
 

Abstract
Main cable configurations under final dead load and in the unloaded state and critical construction parameters (e.g. unstrained cable length, unstrained hanger lengths, and pre-offsets for tower saddles and splay saddles) are the core considerations in the design and construction control of a suspension bridge. For the purpose of accurate calculations, it is necessary to take into account the effects of cable strands over the anchor spans, arc-shaped saddle top, and tower top pre-uplift. In this paper, a method for calculating the cable configuration under final dead load over a main span, two side spans, and two anchor spans, coordinates of tangent points, and unstrained cable length are firstly developed using conditions for mechanical equilibrium and geometric relationships. Hanger tensile forces and unstrained hanger lengths are calculated by iteratively solving the equations governing hanger tensile forces and the cable configuration, which gives careful consideration to the effect of hanger weight. Next, equations for calculating the cable configuration in the unloaded state and pre-offsets of saddles are derived from the cable configuration under final dead load and the conditions for unstrained cable length to be conserved. The equations for the main span, two side spans and two anchor spans are then solved simultaneously. In the proposed methods, coupled nonlinear equations are solved by turning them into an unconstrained optimization problem, making the procedure simplified. The feasibility and validity of the proposed methods are demonstrated through a numerical example.

Key Words
suspension bridge; cable shape; unstrained length; hanger tension; saddle; pre-offset

Address
The Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing, China

Abstract
The paper focuses on bending analysis of the functionally graded (FG) plates with arbitrary shapes and boundary conditions. The material property of FG plates is modelled by using the power law distribution. Based on the first order shear deformation plate theory (FSDT), the governing equations as well as boundary conditions are formulated and obtained by using the principle of virtual work. The coupled Boundary Element-Radial Basis Function (BE-RBF) method is established to solve the complex FG plates. The proposed methodology is developed by applying the concept of the analog equation method (AEM). According to the AEM, the original governing differential equations are replaced by three Poisson equations with fictitious sources under the same boundary conditions. Then, the fictitious sources are established by the application of a technique based on the boundary element method and approximated by using the radial basis functions. The solution of the actual problem is attained from the known integral representations of the potential problem. Therefore, the kernels of the boundary integral equations are conveniently evaluated and readily determined, so that the complex FG plates can be easily computed. The reliability of the proposed method is evaluated by comparing the present results with those from analytical solutions. The effects of the power index, the length to thickness ratio and the modulus ratio on the bending responses are investigated. Finally, many interesting features and results obtained from the analysis of the FG plates with arbitrary shapes and boundary conditions are demonstrated.

Key Words
functionally graded plate; boundary element method; analog equation method

Address
Monchai Panyatong: Department of Civil and Environmental Engineering, Faculty of Engineering, Rajamangala University of Technology Lanna,
Chiang Rai, 57120, Thailand
Boonme Chinnaboon and Somchai Chucheepsakul: Department of Civil Engineering, Faculty of Engineering, King Mongkut

Abstract
A new seismic design methodology was proposed for precast concrete diaphragms. This methodology adopts seismic design factors applied on top of current diaphragm design forces. These factors are aimed to produce diaphragm design strengths aligned with different seismic performance targets. These factors were established through extensive parametric studies. These studies used a simple evaluation structure with a single-bay rectangular diaphragm. The simple evaluation structure is suitable for establishment of the design factors over comprehensive structural geometry and design parameters. However, the application of the design factors to prototype structures with realistic layouts requires further verification and investigation. This paper presents diaphragm design of several precast concrete parking structures using the new design methodology and verification of the design factor through nonlinear dynamic time history analyses. The seismic behavior and performance of the diaphragm were investigated for the precast concrete parking structures. It was found that the design factor established for the new design methodology is applicable to the realistic precast concrete parking structures.

Key Words
precast concrete diaphragms; parking structures; nonlinear time history analysis; seismic design

Address
Dichuan Zhang: School of Engineering and Digital Science, Narzarbayev University
Robert Fleischman: Department of Civil Engineering and Engineering Mechanics, University of Arizona

Abstract
The numerical thermal frequency responses of the skew sandwich shell panels structure are investigated via a higher-order polynomial shear deformation theory including the thickness stretching effect. A customized MATLAB code is developed using the current mathematical model for the computational purpose. The finite element solution accuracy and consistency have been checked via solving different kinds of numerical benchmark examples taken from the literature. After confirming the standardization of the model, it is further extended to show the effect of different important geometrical parameters such as span-to-thickness ratios, aspect ratios, curvature ratios, core-to-face thickness ratios, skew angles, and support conditions on the frequencies of the sandwich composite flat/curved panel structure under elevated temperature environment.

Key Words
frequency; FEM; HSDT; skew angle; sandwich; curved panel

Address
Department of Mechanical Engineering, National Institute of Technology Rourkela, Rourkela-769008, Odisha, India

Abstract
We in this article study nonlinear thermal buckling of bi-directional functionally graded beams in the theoretical frameworks of nonlocal strain graded theory. To begin with, it is assumed that the effective material properties of beams vary continuously in both the thickness and width directions. Then, we utilize a higher-order shear deformation theory that includes a physical neutral surface to derive the size-dependent governing equations combining with the Hamilton\'s principle and the von Kármán geometric nonlinearity. It should be pointed out that the established model, containing a nonlocal parameter and a strain gradient length scale parameter, can availably account for both the influence of nonlocal elastic stress field and the influence of strain gradient stress field. Subsequently, via using a easier group of initial asymptotic solutions, the corresponding analytical solution of thermal buckling of beams is obtained with the help of perturbation method. Finally, a parametric study is carried out in detail after validating the present analysis, especially for the effects of a nonlocal parameter, a strain gradient length scale parameter and the ratio of the two on the critical thermal buckling temperature of beams.

Key Words
Bi-directional FGMs; Nonlocal strain gradient theory; Nonlinear thermal buckling

Address
Yang Gao, Wan-shen Xiao: State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, 410082, China
Haiping Zhu: School of Computing, Engineering and Mathematics, Western Sydney University, Locked, Bag 1797, Penrith, NSW 2751, Australia

Abstract
The reinforced concrete (RC) structures usually suffer large residual displacements under strong motions. The large residual displacements may substantially reduce the anti-seismic capacity of structures during the aftershock and increase the difficulty and cost of structural repair after an earthquake. To reduce the adverse residual displacement, several self-centering energy dissipation braces (SCEBs) have been proposed to be installed to the RC structures. To investigate the seismic responses of the RC structures with SCEBs under the earthquake excitation, an extended Bouc-Wen model with degradation and self-centering effects is developed in this study. The extended model realized by MATLAB/Simulink program is able to capture the hysteretic characteristics of the RC structures with SCEBs, such as the energy dissipation and the degradation, especially the self-centering effect. The predicted hysteretic behavior of the RC structures with SCEBs based on the extended model, which used the unscented Kalman filter (UKF) for parameter identification, is compared with the experimental results. Comparison results show that the predicted hysteretic curves can be in good agreement with the experimental results. The nonlinear dynamic analyses using the extended model are then carried out to explore the seismic performance of the RC structures with SCEBs. The analysis results demonstrate that the SCEB can effectively reduce the residual displacements of the RC structures, but slightly increase the acceleration.

Key Words
Bouc-Wen model; self-centering energy dissipation brace; RC structure: seismic response analysis; self-centering effect

Address
Huihui Dong, Qiang Han and Xiuli Du: Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China
Huihui Dong: Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Department of Civil Engineering, Tsinghua University, Beijing 100084, China

Abstract
The reinforced concrete lining of hydraulic pressure tunnels tends to crack under high inner water pressure (IWP), which results in the inner water exosmosis along cracks and involves typical hydro-mechanical interaction. This study aims at the development, validation and application of an indirect-coupled method to simulate the lining cracking process. Based on the concrete damage plasticity (CDP) model, the utility routine GETVRM and the user subroutine USDFLD in the finite element code ABAQUS is employed to calculate and adjust the secondary hydraulic conductivity according to the material damage and the plastic volume strain. The friction-contact method (FCM) is introduced to track the lining-rock interface behavior. Compared with the traditional node-shared method (NSM) model, the FCM model is more feasible to simulate the lining cracking process. The number of cracks and the reinforcement stress can be significantly reduced, which matches well with the observed results in engineering practices. Moreover, the damage evolution of reinforced concrete lining can be effectively slowed down. This numerical method provides an insight into the cracking process of reinforced concrete lining in hydraulic pressure tunnels.

Key Words
hydraulic pressure tunnel; reinforced concrete lining; hydro-mechanical interaction; crack; indirect-coupled method; friction-contact method

Address
He-Gao Wu, Li Zhou, Kai Su: State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, 430072 Wuhan, China
Ya-Feng Zhou: Changjiang Institute of Survey, Planning, Design and Research, 430010 Wuhan, China
Xi-Yu Wen: Changjiang Geotechnical Engineering Corporation, 430010 Wuhan, China

Abstract
In the paper the dynamics of the oscillating moving load acting in the interior of the hollow cylinder surrounded with elastic medium is studied within the scope of the exact field equations of 3D elastodynamics. It is assumed that the oscillating load act on the certain arc of the internal circle of the cylinder\'s cross section and this load moves with constant velocity along the cylinder\'s axis. The corresponding 3D dynamic problem is solved by employing moving coordinate system, the exponential Fourier transform and the presentation these transforms with the Fourier series. The expressions of the transforms are determined analytically, however their originals are found numerically. Under the investigations carried out in the paper the main attention is focused on the so-called \"gyroscopic effect\", according to which, the influence of the vibration frequency on the values of the critical velocity and interface stresses are determined. Numerical results illustrated this effect are presented and discussed. In particular, it is established how the non-axisymmetricity of the problem acts on the influence of the load oscillation on its critical velocity and on the interface stresses.

Key Words
oscillating-moving load, 3D non-axisymmetric dynamic stress state, critical velocity, hollow cylinder, elastic medium, interface stresses, Fourier series

Address
Surkay D. Akbarov: 1Yildiz Technical University, Faculty of Mechanical Engineering, Department of Mechanical Engineering,
Yildiz Campus, 3349, Besiktas, Istanbul-Turkey
2Institute of Mathematics and Mechanics of National Academy of Sciences of Azerbaijan, 37041, Baku, Azerbaijan
Mahir A. Mehdiyev: Azerbaijan State Economic University, Department of Mathematics, Baku, Azerbaijan

Abstract
This article deals with the application of reliability analysis for determining the safety of simply supported beam under the uniformly distributed load. The uncertainties of the existing methods were taken into account and hence reliability analysis has been adopted. To accomplish this aim, Generalized Regression Neural Network (GRNN), Extreme Learning Machine (ELM) and Gaussian Process Regression (GPR) models are developed. Reliability analysis is the probabilistic style to determine the possibility of failure free operation of a structure. The application of probabilistic mathematics into the quantitative aspects of a structure and improve the qualitative aspects of a structure. In order to construct the GRNN, ELM and GPR models, the dataset contains Modulus of Elasticity (E), Load intensity (w) and performance function () in which E and w are inputs and  is the output. The achievement of the developed models was weighed by various statistical parameters; one among the most primitive parameter is Coefficient of Determination (R2) which has 0.998 for training and 0.989 for testing. The GRNN outperforms the other ELM and GPR models. Other different statistical computations have been carried out, which speaks out the errors and prediction performance in order to justify the capability of the developed models.

Key Words
beam; deflection; ELM; GPR; GRNN; prediction

Address
Jagan J:1School of Civil Engineering, Galgotias University, Greater Noida, Uttar Pradesh-201 308, India
Pijush Samui: Department of Civil Engineering, National Institute of Technology Patna, Patna, Bihar, India
Dookie Kim: Department of Civil Engineering, Kunsan National University, Kunsan, Jeonbuk, South Korea

Abstract
Lamb wave technology is a promising technology in the field of structural health monitoring and can be applied in the detection and monitoring of defects in plate structures. Based on the reconstruction algorithm for the probabilistic inspection of damage (RAPID), a Lamb-based detection and evaluation method of through-thickness rectangular notches in metal plates was proposed in this study. The influences of through-thickness rectangular notch length and the angle between sensing path and notch length direction on signals were further explored through simulations and experiments. Then a damage index calculation method which focuses on both phase and amplitude difference between detected signals and baseline signals was proposed. Based on the damage index difference between two vertically crossed sensing paths which pass through the notch in a sensor network, the notch direction identification method was proposed. In addition, the notch length was determined based on the damage index distribution along sensing paths. The experimental results showed that the image reconstructed with the proposed method could reflect the information for the evaluation of notches.

Key Words
lamb waves; through-thickness rectangular notch; piezoelectric transducers; reconstruction algorithm for the probabilistic inspection of damage

Address
Na Zhao, Bin Wu, Xiucheng Liu: College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing, China
Keqin Ding, Yanan Hu: China Special Equipment Inspection and Research Institute, Beijing, China
Mahmoud Bayat: Department of Civil and Environmental Engineering, University of Pittsburgh, 3700 O\'Hara Street, 729 Benedum Hall, Pittsburgh, PA 15261, USA


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