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CONTENTS
Volume 79, Number 5, September10 2021
 


Abstract
In this paper, a closed-form solution for interfacial stresses in reinforced concrete damaged cantilever beam strengthened by bonded composite plate including the effect of the adherent shear deformations, the creep and shrinkage effect is presented. In such plated beams, tensile forces develop in the bonded plate, and these have to be transferred to the original beam via interfacial shear stresses. Consequently, debonding failure may occur at the plate ends due to a combination of high shear interfacial stress. The analysis is based on the deformation compatibility approach where the shear stress is assumed to be invariant across the adhesive layer thickness. In this study, the adherend shear deformations are taken into account by assuming a parabolic shear stress through the thickness of both the concrete beam and the bonded plate. The influence of creep and shrinkage effect relative to the time of the casting, and the time of the loading of the RC damaged cantilever beams is taken into account. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions.

Key Words
composite plate; creep; interfacial stresses; RC beam; shear lag effect; shrinkage; strengthening

Address
Hassaine Daouadji Tahar, Rabahi Abderezak and Benferhat Rabia: Civil Engineering Department, University of Tiaret, Algeria; Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria

Abstract
The paper presents innovative approaches for the simulation of fatigue crack growth (FCG) in metallic compact tension (CT) specimens using finite element (FE) analysis and analytical solution. FE analysis is performed in ABAQUS using the extended finite element method (XFEM) coupled with the direct cyclic low-cycle fatigue (LCF) approach. Novel methods are developed for the computation of the numerical crack growth by processing the analysis outputs. The numerical modelling is validated by considering past experimental data. The analytical solution for the fatigue life evaluation is formally reviewed, and novel fatigue damage descriptors are defined. The influence of the main sample/testing features on numerical and analytical fatigue life is extensively assessed by a parametric study. The discrepancy between the numerical and analytical estimations of the fatigue life of the components is investigated and correlated to the features of the testing/modelling. A statistical-based correction factor is finally proposed in order to enhance the analytical solution.

Key Words
ABAQUS; fatigue crack growth; fatigue life; FE analysis; low-cycle fatigue; XFEM

Address
Danilo D'Angela: Department of Structures for Engineering and Architecture, University of Naples Federico II, Via Claudio 21, 80125 Napoli, Italy
Marianna Ercolino: School of Engineering, University of Greenwich, Central Avenue, Chatham ME4 4TB, United Kingdom

Abstract
Several studies discuss how climate change influences precipitation, temperature, and wind loads. The wind loads, in particular, are a great concern in structural design, as their dynamic forces directly affect structural safety. In Brazilian codes, the wind loads are based on an isopleth map, created in 1977. The experimental data was collected on few weather stations (between 1950 and 1974) and treated statistically before being plotted. In view of this, a new assessment of the Brazilian code is necessary to evaluate the impact of climate change in the wind speeds and to develop a more thorough method, since a greater number of isopleths are more favorable for designing with safety. In this study, new data was collected from a greater number of weather stations, and a new approach to select and process wind-related data was proposed. The new method combined the maximum likelihood estimation with Gumbel distribution. The new method also adopted Kriging interpolation to georeference the wind speeds according to each station. The main advantage was to consider the extreme wind speed as a regionalized variable. After validating the results, a new isopleth map was created with updated data and greater precision. Finally, it could be seen a significant increase in the speed of extreme winds in the Brazilian territory. This confirmed the existing global trend discussed in the literature.

Key Words
climate change; extreme wind; isopleth map; statistical treatments; wind load

Address
Lindemberg O. Almeida: Department of Civil Engineering, University of Fortaleza, 1321 Washington Soares, Fortaleza, Ceara 60811-905, Brazil
Maryangela G. Lima: Department of Civil Engineering, Aeronautics Institute of Technology, 50 Marechal Eduardo Gomes, Sao Jose dos Campos, Sao Paulo 12228-615, Brazil
Ian C.A. Esteves, Guilherme S. Munhoz, Ronaldo A. Medeiros-Junior: Department of Civil Construction, Federal University of Parana, 100 Cel., Francisco H. dos Santos, Curitiba, Parana 81530-000, Brazil

Abstract
In order to predict the shear strength of corroded reinforced concrete column (CRCC) accurately and efficiently, both theoretical and practical models for shear strength of the CRCC were established through theoretical derivation and experimental validation. The deterioration mechanism for shear strength of the CRCC due to the steel reinforcement corrosion was explored first based on the shear mechanism analysis of the truss-arch model. Then a theoretical model for shear strength of the CRCC was developed by taking into account the influences of steel reinforcement corrosion on the effective yield strength of transverse reinforcement, the effective cross-sectional area of both corroded transverse and longitudinal reinforcements as well as the effective concrete shear area. Meanwhile, three practical models to evaluate the shear strength of the CRCC were proposed based on 54 sets of experimental data by determining the approximate values of three important parameters, including the contribution coefficient of shear strength for concrete, the ratio of shear stiffness between the truss model and the arch model, as well as the tangent value of the critical crack angle. Finally, the accuracy and applicability of both theoretical and practical models for shear strength of the CRCC were validated by comparing with five existing empirical shear strength models.

Key Words
corrosion; practical model; reinforced concrete column; shear strength; theoretical model; truss-arch model

Address
Bo Yu: School of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China; Key Laboratory of Engineering Disaster Prevention and Structural Safety of China Ministry of Education, China; Guangxi Key Laboratory of Disaster Prevention and Engineering Safety, Nanning 530004, China
Zihao Ding: School of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China; School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Shengbin Liu: School of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China; Nanjing Municipal Design and Research Institute Co., Ltd, Nanjing 210008, China
Bing Li: School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore

Abstract
Six specimens of prefabricated high-strength concrete columns with confining overlapping stirrups were tested under cyclic lateral loads, and a finite element analysis was performed using ABAQUS to investigate the seismic behavior of the columns. The influences of the axial compression ratio, stirrup diameter and stirrup spacing were considered. Comparative analyses indicate that the numerical simulation outcomes agree well with the experimental results, including the hysteretic curves, peak loads and failure modes. With an increase in the axial compression ratio, the ultimate load bearing capacity of the specimen increases, ductility worsens, strength descending part of the shear-displacement skeleton curves steepens, and energy dissipation capacity increases slightly. When the stirrup spacing decreases or the stirrup diameter increases, the ultimate load bearing capacity, ductility and energy dissipation capacity of the specimens increase. The effect of the axial compression ratio on the shear capacity of the test specimens is much more pronounced than that of the stirrup ratio. With an increase in the stirrup diameter, the initial stiffness of the specimen decreases, and stiffness deterioration during the late stages of loading cycles slows down. However, changing the spacing of the stirrups has little effect on the stiffness of the specimens.

Key Words
finite element analysis; overlapping stirrups; prefabricated concrete columns; quasi-static experiment; seismic behavior

Address
Juju Bai and Shengcai Li: School of Civil Engineering, Huaqiao University, Xiamen 361021, China

Abstract
The present paper investigates the frequencies based on the radial vibrations of a non-homogeneous elastic cylinder using different boundary conditions (BCs) under the rotating, non-homogeneity, and magnetic field effects. Three different BCs, the free, mixed, and fixed, are implemented. The solution is related to using the eigenvalues based on the radial vibrations frequencies for different boundary conditions in harmonic vibrations. The numeric outcomes are demonstrated graphically for each case-the comparison of the results in the nonappearance and variation of the non-homogeneity, rotating effects, and magnetic field. The obtained outcomes specify the rotating, non-homogeneity, and magnetic field effects.

Key Words
initial stress; magnetic field; non-homogeneous; rotation; vibrations

Address
K.S. Al-Basyouni: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
S.R. Mahmoud: GRC Department, Faculty of Applied Studies, King Abdulaziz University, Jeddah 21589, Saudi Arabia

Abstract
Subterranean floors are treated as the rigid lateral support in the current practice for the basement wall design. The structural performance of the basement wall will be influenced by the floor openings, which are inevitable to satisfy building functional requirements. An analytical model for the basement wall being presented is able to analyze the effect of such opening quantitatively. The magnitude of the horizontal support stiffness is determined based on deformation analysis of the diaphragm opening area. Idealized models of the basement wall are continuous beams with various degrees of indeterminacy. The force method is used to deduce the functions for internal forces acting towards the basement wall. The proposed analytical model is verified with results derived by finite element analyses through consideration of various factors, including various numbers of stories, combinations of beam-slab sections, and percentages of floor opening dimensions. The maximum deviations on critical design sections for all prototype basement structures are less than 15.99%. Comparisons with conventional rigid support models are also performed, providing an estimation of the effect of the opening on the mechanical behavior of the basement wall.

Key Words
basement wall; finite element model; floor with openings; force method; horizontal support stiffness

Address
Yongjun Lin, Xianzhao Zhang, Kaiqi Liu and Wenqiang Xu: Department of Building Engineering, School of Civil Engineering, Southwest Jiaotong University, 111 North 1st Section of Second Ring Road, Chengdu 610031, China

Abstract
The frequency-based method is the most commonly used method for measuring cable tension. However, the calculation formulas for the conventional frequency-based method are generally based on the ideally hinged or fixed boundary conditions without a comprehensive consideration of the inclination angle, sag-extensibility, and flexural stiffness of cables, leading to a significant error in cable tension identification. This study aimed to propose a frequency-based method of cable tension identification considering the complex boundary conditions at the two ends of cables using the particle swarm optimization (PSO) algorithm. First, the refined stay cable model was established considering the inclination angle, flexural stiffness, and sag-extensibility, as well as the rotational constraint stiffness and lateral support stiffness for the unknown boundaries of cables. The vibration mode equation of the stay cable model was discretized and solved using the finite difference method. Then, a multiparameter identification method based on the PSO algorithm was proposed. This method was able to identify the tension, flexural stiffness, axial stiffness, boundary rotational constraint stiffness, and boundary lateral support stiffness according to the measured multiorder frequencies in a synchronous manner. The feasibility and accuracy of this method were validated through numerical cases. Finally, the proposed approach was applied to the tension identification of the anchor span strands of a suspension bridge (Jindong Bridge) in China. The results of cable tension identification using the proposed method and the existing methods discussed in previous studies were compared with the on-site pressure ring measurement results. The comparison showed that the proposed approach had a high accuracy in cable tension identification. Moreover, the synchronous identification of the flexural stiffness, axial stiffness, boundary rotational constraint stiffness, and boundary lateral support stiffness was highly beneficial in improving the results of cable tension identification.

Key Words
boundary constraint stiffness; cable tension; finite difference method; frequency-based method; multiparameter identification; particle swarm optimization algorithm

Address
Wen-ming Zhang, Zhi-wei Wang, Dan-dian Feng and Zhao Liu: The Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 211189, China

Abstract
Many SMA-based dampers were presented and they can show both energy dissipating capability and self-centring property. This paper aims to a self-centring damper composed by two groups of pre-tensioned SMA wires and two precompressed springs. The three-dimensional solid finite element models of the damper are constructed at ANSYS Workbench environment, and the Auricchio's model is used to simulate the superelastic behaviour of the SMA wires. To simulate the damper assembly process, the models of two springs are compressed and certain pre-tensions are imposed to the SMA wires. The initial stresses for the core components are figured out and imposed to the un-deformed damper. Then, the cyclic loads are imposed to the damper models and the mechanical behaviour of the damper is simulated. The numerical simulation results are compared with the theoretical analysis results based on the Brinson model of the SMA material. For a 1 m long damper with a 5 mm stroke in the case study, both the numerical and theoretical results show that a 35 kN reaction force is offered by the damper. The force-displacement curves of the damper model are flag-shaped, indicating the moderated energy dissipating capacity and full self-centring capability of the damper.

Key Words
damper; energy dissipating; finite element analysis; shape memory alloys; superelastic effect

Address
Hongwei Ma and Yuhong Ling: State Key Laboratory of Subtropical Architecture Science, South China University of Technology, Guangzhou, 510640, China

Abstract
The aim of this paper is to study the effects of linear viscoelastic behavior on dynamic buckling response of imperfect composite laminated plates subjected to in-plane dynamic loads by implementing semi-analytical finite strip method (FSM). The semi-analytical FSM converges with a comparatively small number of strips and correspondingly small number of degrees of freedom. Thus, it is usually implemented more easily and faster than many other computational methods. The governing equations are derived by using classical laminated plate theory (CLPT) and the behavior of plate is assumed to be geometrically nonlinear through Von-Karman assumptions. The Newmark's implicit time integration method in conjunction with the Newton-Raphson iteration are employed to solve the nonlinear governing equation. A Kelvin-Voigt viscoelastic model is considered, and the effects of viscosity coefficient, thickness of the layers of the composite plate and boundary conditions on the nonlinear dynamic buckling response are discussed. In order to justify the accuracy of the results, some of them are verified against those available in other sources. It is also shown that the nonlinear dynamic buckling response of an imperfect viscoelastic composite laminated plate is significantly different from the elastic one by considering different viscosity coefficients.

Key Words
dynamic buckling; finite strip method; Kelvin-Voigt model; linear viscoelastic

Address
Mehran Mohammad Hossein Pour and Hamid Reza Ovesy: Aerospace Engineering Department and Center of Excellence in Computational Aerospace Engineering, Amirkabir University of Technology, Hafez Avenue, Tehran, Iran


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