Frontiers of Structural and Civil Engineering

ISSN 2095-2430 (Print)
ISSN 2095-2449 (Online)
CN 10-1023/X
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Impact analysis of compressor rotor blades of an aircraft engine
Y B SUDHIR SASTRY, B G KIROS, F HAILU, P R BUDARAPU
Front. Struct. Civ. Eng.    2019, 13 (3): 505-514.   https://doi.org/10.1007/s11709-018-0493-3
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Frequent failures due to foreign particle impacts are observed in compressor blades of the interceptor fighter MIG-23 aircraft engines in the Ethiopian air force, supplied by the Dejen Aviation Industry. In this paper, we made an attempt to identify the causes of failure and hence recommend the suitable materials to withstand the foreign particle impacts. Modal and stress analysis of one of the recently failed MIG-23 gas turbine compressor blades made up of the following Aluminum based alloys: 6061-T6, 7075-T6, and 2024-T4, has been performed, apart from the impact analysis of the rotor blades hit by a granite stone. The numerical results are correlated to the practical observations. Based on the modal, stress and impact analysis and the material properties of the three considered alloys, alloy 7075-T6 has been recommended as the blade material.

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Seismic fragility assessment of revised MRT buildings considering typical construction changes
Rakesh DUMARU, Hugo RODRIGUES, Humberto VARUM
Front. Struct. Civ. Eng.    2020, 14 (1): 241-266.   https://doi.org/10.1007/s11709-019-0560-4
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The present study investigates the vulnerability assessment of the prototype revised Mandatory Rule of Thumb (MRT) buildings initially designed and detailed for three storeys bare frame building; later modified through variable number of storeys (three, four, and five) and different arrangement of infill walls (bare frame, soft-storey, irregular infilled, and fully infilled). The application of infill walls increases the fundamental frequencies, stiffness, and maximum strength capacity, but reduces the deformation capability than the bare frame building. The vulnerability was also reduced through infill walls, where the probability of exceeding partial-collapse and collapse damage reduced by 80% and 50%, respectively. Furthermore, the increased in storeys (three to five) also increases the failure probability, such that partial-collapse and collapse for fully infilled increases by almost 55% and 80%, respectively. All obtained results and discussions concluded that the structural sections and details assigned for MRT building is not sufficient if considered as bare frame and soft-storey. And increase in number of storeys causes building highly vulnerable although the infill walls were considered.

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Implementation aspects of a phase-field approach for brittle fracture
G. D. HUYNH, X. ZHUANG, H. NGUYEN-XUAN
Front. Struct. Civ. Eng.    2019, 13 (2): 417-428.   https://doi.org/10.1007/s11709-018-0477-3
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This paper provides a comprehensive overview of a phase-field model of fracture in solid mechanics setting. We start reviewing the potential energy governing the whole process of fracture including crack initiation, branching or merging. Then, a discretization of system of equation is derived, in which the key aspect is that for the correctness of fracture phenomena, a split into tensile and compressive terms of the strain energy is performed, which allows crack to occur in tension, not in compression. For numerical analysis, standard finite element shape functions are used for both primary fields including displacements and phase field. A staggered scheme which solves the two fields of the problem separately is utilized for solution step and illustrated with a segment of Python code.

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A FEniCS implementation of the phase field method for quasi-static brittle fracture
HIRSHIKESH, Sundararajan NATARAJAN, Ratna Kumar ANNABATTULA
Front. Struct. Civ. Eng.    2019, 13 (2): 380-396.   https://doi.org/10.1007/s11709-018-0471-9
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In the recent years, the phase field method for simulating fracture problems has received considerable attention. This is due to the salient features of the method: 1) it can be incorporated into any conventional finite element software; 2) has a scalar damage variable is used to represent the discontinuous surface implicitly and 3) the crack initiation and subsequent propagation and branching are treated with less complexity. Within this framework, the linear momentum equations are coupled with the diffusion type equation, which describes the evolution of the damage variable. The coupled nonlinear system of partial differential equations are solved in a ‘staggered’ approach. The present work discusses the implementation of the phase field method for brittle fracture within the open-source finite element software, FEniCS. The FEniCS provides a framework for the automated solutions of the partial differential equations. The details of the implementation which forms the core of the analysis are presented. The implementation is validated by solving a few benchmark problems and comparing the results with the open literature.

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Technological development and engineering applications of novel steel-concrete composite structures
Jianguo NIE, Jiaji WANG, Shuangke GOU, Yaoyu ZHU, Jiansheng FAN
Front. Struct. Civ. Eng.    2019, 13 (1): 1-14.   https://doi.org/10.1007/s11709-019-0514-x
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In view of China’s development trend of green building and building industrialization, based on the emerging requirements of the structural engineering community, the development and proposition of novel resource-saving high-performance steel-concrete composite structural systems with adequate safety and durability has become a kernel development trend in structural engineering. This paper provides a state of the art review of China’s cutting-edge research and technologies in steel-concrete composite structures in recent years, including the building engineering, the bridge engineering and the special engineering. This paper summarizes the technical principles and applications of the long-span bi-directional composite structures, the long-span composite transfer structures, the comprehensive crack control technique based on uplift-restricted and slip-permitted (URSP) connectors, the steel plate concrete composite (SPCC) strengthen technique, and the innovative composite joints. By improving and revising traditional structure types, the comprehensive superiority of steel-concrete composite structures is well elicited. The research results also indicate that the high-performance steel-concrete composite structures have a promising popularizing prospect in the future.

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Peridynamics versus XFEM: a comparative study for quasi-static crack problems
Jinhai ZHAO, Hesheng TANG, Songtao XUE
Front. Struct. Civ. Eng.    2018, 12 (4): 548-557.   https://doi.org/10.1007/s11709-017-0434-6
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Peridynamics (PD) is a nonlocal continuum theory based on integro-differential equations without spatial derivatives. The fracture criterion is implicitly incorporated in the PD theory and fracture is a natural outcome of the simulation. However, capturing of complex mixed-mode crack patterns has been proven to be difficult with PD. On the other hand, the extended finite element method (XFEM) is one of the most popular methods for fracture which allows crack propagation with minimal remeshing. It requires a fracture criterion which is independent of the underlying discretization though a certain refinement is needed in order to obtain suitable results. This article presents a comparative study between XFEM and PD. Therefore, two examples are studied. The first example is crack propagation in a double notched specimen under uniaxial tension with different crack spacings in loading direction. The second example is the specimens with two center cracks. The results show that PD as well as XFEM are well suited to capture this type of behaviour.

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Independent cover meshless particle method for complex geotechnical engineering
Jianqiu WU, Yongchang CAI
Front. Struct. Civ. Eng.    2018, 12 (4): 515-526.   https://doi.org/10.1007/s11709-017-0428-4
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A new Independent Cover Meshless Particle (ICMP) method is proposed for the analysis of complex geotechnical engineering. In the ICMP method, the independent rectangular cover regardless of the shape of the analysis model is employed as the influence domain of each discrete node, the general polynomial is employed as the meshless interpolation function of the independent nodal cover, and the Cartesian Transformation Method (CTM) is used for the numerical integration of the nodal covers cut by material interfaces, joints, cracks and faults. The present method has a simple formulation and a low computational cost, and is easy for the numerical analysis and modeling of complex geotechnical engineering. Several typical numerical examples are presented to demonstrate the accuracy and robustness of the proposed method.

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Frontier of continuous structural health monitoring system for short & medium span bridges and condition assessment
Ayaho MIYAMOTO, Risto KIVILUOMA, Akito YABE
Front. Struct. Civ. Eng.    2019, 13 (3): 569-604.   https://doi.org/10.1007/s11709-018-0498-y
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It is becoming an important social problem to make maintenance and rehabilitation of existing short and medium span(10-20 m) bridges because there are a huge amount of short and medium span bridges in service in the world. The kernel of such bridge management is to develop a method of safety(condition) assessment on items which include remaining life and load carrying capacity. Bridge health monitoring using information technology and sensors is capable of providing more accurate knowledge of bridge performance than traditional strategies. The aim of this paper is to introduce a state-of-the-art on not only a rational bridge health monitoring system incorporating with the information and communication technologies for lifetime management of existing short and medium span bridges but also a continuous data collecting system designed for bridge health monitoring of mainly short and medium span bridges. In this paper, although there are some useful monitoring methods for short and medium span bridges based on the qualitative or quantitative information, mainly two advanced structural health monitoring systems are described to review and analyse the potential of utilizing the long term health monitoring in safety assessment and management issues for short and medium span bridge. The first is a special designed mobile in-situ loading device(vehicle) for short and medium span road bridges to assess the structural safety(performance) and derive optimal strategies for maintenance using reliability based method. The second is a long term health monitoring method by using the public buses as part of a public transit system (called bus monitoring system) to be applied mainly to short and medium span bridges, along with safety indices, namely, “characteristic deflection” which is relatively free from the influence of dynamic disturbances due to such factors as the roughness of the road surface, and a structural anomaly parameter.

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Static analysis of corrugated panels using homogenization models and a cell-based smoothed mindlin plate element (CS-MIN3)
Nhan NGUYEN-MINH, Nha TRAN-VAN, Thang BUI-XUAN, Trung NGUYEN-THOI
Front. Struct. Civ. Eng.    2019, 13 (2): 251-272.   https://doi.org/10.1007/s11709-017-0456-0
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Homogenization is a promising approach to capture the behavior of complex structures like corrugated panels. It enables us to replace high-cost shell models with stiffness-equivalent orthotropic plate alternatives. Many homogenization models for corrugated panels of different shapes have been proposed. However, there is a lack of investigations for verifying their accuracy and reliability. In addition, in the recent trend of development of smoothed finite element methods, the cell-based smoothed three-node Mindlin plate element (CS-MIN3) based on the first-order shear deformation theory (FSDT) has been proposed and successfully applied to many analyses of plate and shell structures. Thus, this paper further extends the CS-MIN3 by integrating itself with homogenization models to give homogenization methods. In these methods, the equivalent extensional, bending, and transverse shear stiffness components which constitute the equivalent orthotropic plate models are represented in explicit analytical expressions. Using the results of ANSYS and ABAQUS shell simulations as references, some numerical examples are conducted to verify the accuracy and reliability of the homogenization methods for static analyses of trapezoidally and sinusoidally corrugated panels.

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A three-dimensional two-level gradient smoothing meshfree method for rainfall induced landslide simulations
Dongdong WANG, Jiarui WANG, Junchao WU, Junjun DENG, Ming SUN
Front. Struct. Civ. Eng.    2019, 13 (2): 337-352.   https://doi.org/10.1007/s11709-018-0467-5
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A three-dimensional two-level gradient smoothing meshfree method is presented for rainfall induced landslide simulations. The two-level gradient smoothing for meshfree shape function is elaborated in the three-dimensional Lagrangian setting with detailed implementation procedure. It is shown that due to the successive gradient smoothing operation without the requirement of derivative computation in the present formulation, the two-level smoothed gradient of meshfree shape function is capable of achieving a given influence domain more efficiently than the standard gradient of meshfree shape function. Subsequently, the two-level smoothed gradient of meshfree shape function is employed to discretize the weak form of coupled rainfall seepage and soil motion equations in a nodal integration format, as provides an efficient three-dimensional regularized meshfree formulation for large deformation rainfall induced landslide simulations. The exponential damage and pressure dependent plasticity relationships are utilized to describe the failure evolution in landslides. The plastic response of soil is characterized by the true effective stress measure, which is updated according to the rotationally neutralized objective integration algorithm. The effectiveness of the present three-dimensional two-level gradient smoothing meshfree method is demonstrated through numerical examples.

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Computational methods for fracture in rock: a review and recent advances
Ali JENABIDEHKORDI
Front. Struct. Civ. Eng.    2019, 13 (2): 273-287.   https://doi.org/10.1007/s11709-018-0459-5
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We present an overview of the most popular state-of-the-art computational methods available for modelling fracture in rock. The summarized numerical methods can be classified into three categories: Continuum Based Methods, Discrete Crack Approaches, and Block-Based Methods. We will not only provide an extensive review of those methods which can be found elsewhere but particularly address their potential in modelling fracture in rock mechanics and geotechnical engineering. In this context, we will discuss their key applications, assumptions, and limitations. Furthermore, we also address ‘general’ difficulties that may arise for simulating fracture in rock and fractured rock. This review will conclude with some final remarks and future challenges.

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Fused structures for safer and more economical constructions
Yu-Fei WU, Ying-Wu ZHOU, Biao HU, Xiaoxu HUANG, Scott SMITH
Front. Struct. Civ. Eng.    2020, 14 (1): 1-9.   https://doi.org/10.1007/s11709-019-0541-7
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Safety margin and construction costs are two conflicting goals for a structure. By providing a fuse in a structure that is triggered at a certain level of over-loading, further increase of loading is prohibited and failure of the structure is changed to a safer mode. As overloading is controlled and a safer failure mode is enforced, a fused structure requires a smaller safety factor thus leading to more economical construction without compromising safety. The use of a fuse will also facilitate safer use of advanced construction materials such as fiber-reinforced polymer (FRP) composites. In this case, a fuse can transfer the sudden and dangerous failure mode associated with brittle FRP debonding or rupture to a safe and ductile failure mode at the fuse location. This paper introduces a new type of fused structure as well as an associated design philosophy and approach, in addition to examples of engineering applications.

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The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired solutions
Gui-Rong Liu
Front. Struct. Civ. Eng.    2019, 13 (2): 456-477.   https://doi.org/10.1007/s11709-019-0519-5
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The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

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Three-scale stochastic homogenization of elastic recycled aggregate concrete based on nano-indentation digital images
Chen WANG, Yuching WU, Jianzhuang XIAO
Front. Struct. Civ. Eng.    2018, 12 (4): 461-473.   https://doi.org/10.1007/s11709-017-0441-7
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In this paper, three-scale stochastic elastic finite element analyses are made for recycled aggregate concrete (RAC) based on nano-indentation digital images. The elastic property of RAC contains uncertainties across scales. It has both theoretical and practical values to model and predict its mechanical performance. Based on homogenization theory, effective stochastic elastic moduli of RAC at three different scales are obtained using moving window technique, nano-indentation digital images, and Monte-Carlo method. It involves the generation of a large number of random realizations of microstructure geometry based on different volume fraction of the inclusions and other parameters. The mean value, coefficient of variation and probability distribution of the effective elastic moduli are computed considering the material multiscale structure. The microscopic randomness is taken into account, and correlations of RAC among five phases are investigated. The effective elastic properties are used to obtain the global behavior of a composite structure. It is indicated that the response variability can be considerably affected by replacement percentage of recycled aggregates.

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A new fracture criterion for peridynamic and dual-horizon peridynamics
Jinhai ZHAO, Hesheng TANG, Songtao XUE
Front. Struct. Civ. Eng.    2018, 12 (4): 629-641.   https://doi.org/10.1007/s11709-017-0447-1
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A new fracture criterion based on the crack opening displacement for peridynamic (PD) and dual-horizon peridynamics (DH-PD) is proposed. When the relative deformation of the PD bond between the particles reaches the critical crack tip opening displacement of the fracture mechanics, we assume that the bond force vanishes. A new damage rule similar to the local damage rule in conventional PD is introduced to simulate fracture. The new formulation is developed for a linear elastic solid though the extension to nonlinear materials is straightforward. The performance of the new fracture criterion is demonstrated by four examples, i.e. a bilateral crack problem, double parallel crack, monoclinic crack and the double inclined crack. The results are compared to experimental data and the results obtained by other computational methods.

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Effect of calcium lactate on compressive strength and self-healing of cracks in microbial concrete
Kunamineni VIJAY, Meena MURMU
Front. Struct. Civ. Eng.    2019, 13 (3): 515-525.   https://doi.org/10.1007/s11709-018-0494-2
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This paper presents the effect on compressive strength and self-healing capability of bacterial concrete with the addition of calcium lactate. Compared to normal concrete, bacterial concrete possesses higher durability and engineering concrete properties. The production of calcium carbonate in bacterial concrete is limited to the calcium content in cement. Hence calcium lactate is externally added to be an additional source of calcium in the concrete. The influence of this addition on compressive strength, self-healing capability of cracks is highlighted in this study. The bacterium used in the study is bacillus subtilis and was added to both spore powder form and culture form to the concrete. Bacillus subtilis spore powder of 2 million cfu/g concentration with 0.5% cement was mixed to concrete. Calcium lactates with concentrations of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of cement, was added to the concrete mixes to test the effect on properties of concrete. In other samples, cultured bacillus subtilis with a concentration of 1×105 cells/mL was mixed with concrete, to study the effect of bacteria in the cultured form on the properties of concrete. Cubes of 100 mm×100 mm×100 mm were used for the study. These cubes were tested after a curing period of 7, 14, and 28 d. A maximum of 12% increase in compressive strength was observed with the addition of 0.5% of calcium lactate in concrete. Scanning electron microscope and energy dispersive X-ray spectroscopy examination showed the formation of ettringite in pores; calcium silicate hydrates and calcite which made the concrete denser. A statistical technique was applied to analyze the experimental data of the compressive strengths of cementations materials. Response surface methodology was adopted for optimizing the experimental data. The regression equation was yielded by the application of response surface methodology relating response variables to input parameters. This method aids in predicting the experimental results accurately with an acceptable range of error. Findings of this investigation indicated the influence of added calcium lactate in bio-concrete which is quite impressive for improving the compressive strength and self-healing properties of concrete.

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Non linear modeling of three-dimensional reinforced and fiber concrete structures
Fatiha IGUETOULENE, Youcef BOUAFIA, Mohand Said KACHI
Front. Struct. Civ. Eng.    2018, 12 (4): 439-453.   https://doi.org/10.1007/s11709-017-0433-7
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Under the effect of the ascending loading, the behavior of reinforced concrete structures is rather non linear. Research in industry and science aims to extend forward the use of non-linear calculation of fiber concrete for structural parts such as columns, veils and pious, as the fiber concrete is more ductile behavior then the classical concrete behavior. The formulation of the element has been established for modeling the nonlinear behavior of elastic structures in three dimensions, based on the displacement method. For the behavior of concrete and fiber concrete compressive and tensile strength (stress-strain) the uniaxial formulation is used. For steel bi-linear relationship is used. The approach is based on the discretization of the cross section trapezoidal tables. Forming the stiffness matrix of the section, the integral of the surface is calculated as the sum of the integrals on each of the cutting trapezoids. To integrate on the trapeze we have adopted the type of Simpson integration scheme.

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Free vibration analysis of laminated FG-CNT reinforced composite beams using finite element method
T. VO-DUY, V. HO-HUU, T. NGUYEN-THOI
Front. Struct. Civ. Eng.    2019, 13 (2): 324-336.   https://doi.org/10.1007/s11709-018-0466-6
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In the present study, the free vibration of laminated functionally graded carbon nanotube reinforced composite beams is analyzed. The laminated beam is made of perfectly bonded carbon nanotubes reinforced composite (CNTRC) layers. In each layer, single-walled carbon nanotubes are assumed to be uniformly distributed (UD) or functionally graded (FG) distributed along the thickness direction. Effective material properties of the two-phase composites, a mixture of carbon nanotubes (CNTs) and an isotropic polymer, are calculated using the extended rule of mixture. The first-order shear deformation theory is used to formulate a governing equation for predicting free vibration of laminated functionally graded carbon nanotubes reinforced composite (FG-CNTRC) beams. The governing equation is solved by the finite element method with various boundary conditions. Several numerical tests are performed to investigate the influence of the CNTs volume fractions, CNTs distributions, CNTs orientation angles, boundary conditions, length-to-thickness ratios and the numbers of layers on the frequencies of the laminated FG-CNTRC beams. Moreover, a laminated composite beam combined by various distribution types of CNTs is also studied.

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Global sensitivity analysis of certain and uncertain factors for a circular tunnel under seismic action
Nazim Abdul NARIMAN, Raja Rizwan HUSSAIN, Ilham Ibrahim MOHAMMAD, Peyman KARAMPOUR
Front. Struct. Civ. Eng.    2019, 13 (6): 1289-1300.   https://doi.org/10.1007/s11709-019-0548-0
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There are many certain and uncertain design factors which have unrevealed rational effects on the generation of tensile damage and the stability of the circular tunnels during seismic actions. In this research paper, we have dedicated three certain and four uncertain design factors to quantify their rational effects using numerical simulations and the Sobol’s sensitivity indices. Main effects and interaction effects between the design factors have been determined supporting on variance-based global sensitivity analysis. The results detected that the concrete modulus of elasticity for the tunnel lining has the greatest effect on the tensile damage generation in the tunnel lining during the seismic action. In the other direction, the interactions between the concrete density and both of concrete modulus of elasticity and tunnel diameter have appreciable effects on the tensile damage. Furthermore, the tunnel diameter has the deciding effect on the stability of the tunnel structure. While the interaction between the tunnel diameter and concrete density has appreciable effect on the stability process. It is worthy to mention that Sobol’s sensitivity indices manifested strong efficiency in detecting the roles of each design factor in cooperation with the numerical simulations explaining the responses of the circular tunnel during seismic actions.

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Evaluating the material strength from fracture angle under uniaxial loading
Jitang FAN
Front. Struct. Civ. Eng.    2019, 13 (2): 288-293.   https://doi.org/10.1007/s11709-018-0480-8
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The most common experimental methods of measuring material strength are the uniaxial compressive and tensile tests. Generally, shearing fracture model occurs in both the tests. Compressive strength is higher than tensile strength for a material. Shearing fracture angle is smaller than 45° under uniaxial compression and greater than 45° under uniaxial tension. In this work, a unified relation of material strength under uniaxial compression and tension is developed by correlating the shearing fracture angle in theory. This constitutive relation is quantitatively illustrated by a function for analyzing the material strength from shear fracture angle. A computational simulation is conducted to validate this theoretical function. It is full of interest to give a scientific illustration for designing the high-strength materials and engineering structures.

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Dynamic failure analysis of concrete dams under air blast using coupled Euler-Lagrange finite element method
Farhoud KALATEH
Front. Struct. Civ. Eng.    2019, 13 (1): 15-37.   https://doi.org/10.1007/s11709-018-0465-7
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In this study, the air blast response of the concrete dams including dam-reservoir interaction and acoustic cavitation in the reservoir is investigated. The finite element (FE) developed code are used to build three-dimensional (3D) finite element models of concrete dams. A fully coupled Euler-Lagrange formulation has been adopted herein. A previous developed model including the strain rate effects is employed to model the concrete material behavior subjected to blast loading. In addition, a one-fluid cavitating model is employed for the simulation of acoustic cavitation in the fluid domain. A parametric study is conducted to evaluate the effects of the air blast loading on the response of concrete dam systems. Hence, the analyses are performed for different heights of dam and different values of the charge distance from the charge center. Numerical results revealed that 1) concrete arch dams are more vulnerable to air blast loading than concrete gravity dams; 2) reservoir has mitigation effect on the response of concrete dams; 3) acoustic cavitation intensify crest displacement of concrete dams.

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Electronic and mechanical responses of two-dimensional HfS2, HfSe2, ZrS2, and ZrSe2 from first-principles
Mohammad SALAVATI
Front. Struct. Civ. Eng.    2019, 13 (2): 486-494.   https://doi.org/10.1007/s11709-018-0491-5
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During the last decade, numerous high-quality two-dimensional (2D) materials with semiconducting electronic character have been synthesized. Recent experimental study (Sci. Adv. 2017;3: e1700481) nevertheless confirmed that 2D ZrSe2 and HfSe2 are among the best candidates to replace the silicon in nanoelectronics owing to their moderate band-gap. We accordingly conducted first-principles calculations to explore the mechanical and electronic responses of not only ZrSe2 and HfSe2, but also ZrS2 and HfS2 in their single-layer and free-standing form. We particularly studied the possibility of engineering of the electronic properties of these attractive 2D materials using the biaxial or uniaxial tensile loadings. The comprehensive insight provided concerning the intrinsic properties of HfS2, HfSe2, ZrS2, and ZrSe2 can be useful for their future applications in nanodevices.

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Predicting the response of continuous RC deep beams under varying levels of differential settlement
M. Z. Naser, R. A. Hawileh
Front. Struct. Civ. Eng.    2019, 13 (3): 686-700.   https://doi.org/10.1007/s11709-018-0506-2
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This paper investigates the effect of differential support settlement on shear strength and behavior of continuous reinforced concrete (RC) deep beams. A total of twenty three-dimensional nonlinear finite element models were developed taking into account various constitutive laws for concrete material in compression (crushing) and tension (cracking), steel plasticity (i.e., yielding and strain hardening), bond-slip at the concrete and steel reinforcement interface as well as unique behavior of spring-like support elements. These models are first validated by comparing numerical predictions in terms of load-deflection response, crack propagation, reaction distribution, and failure mode against that of measured experimental data reported in literature. Once the developed models were successfully validated, a parametric study was designed and performed. This parametric study examined number of critical parameters such as ratio and spacing of the longitudinal and vertical reinforcement, compressive and tensile strength of concrete, as well as degree (stiffness) and location of support stiffness to induce varying levels of differential settlement. This study also aims at presenting a numerical approach using finite element simulation, supplemented with coherent assumptions, such that engineers, practitioners, and researchers can carry out simple, but yet effective and realistic analysis of RC structural members undergoing differential settlements due to variety of load actions.

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A modified pulse charging method for lithium-ion batteries by considering stress evolution, charging time and capacity utilization
Yanfei ZHAO, Bo LU, Yicheng SONG, Junqian ZHANG
Front. Struct. Civ. Eng.    2019, 13 (2): 294-302.   https://doi.org/10.1007/s11709-018-0460-z
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The stress evolution, total charging time and capacity utilization of pulse charging (PC) method are investigated in this paper. It is found that compared to the conventional constant current (CC) charging method, the PC method can accelerate the charging process but will inevitably cause an increase in stress and a decrease in capacity. The charging speed for PC method can be estimated by the mean current. By introducing stress control, a modified PC method called the PCCC method, which starts with a PC operation followed by a CC operation, is proposed. The PCCC method not only can accelerate charging process but also can avoid the stress raising and capacity loss occurring in the PC method. Furthermore, the optimal pulsed current density and switch time in the PCCC method is also discussed.

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Uncertainty quantification of stability and damage detection parameters of coupled hydrodynamic-ground motion in concrete gravity dams
Nazim Abdul NARIMAN, Tom LAHMER, Peyman KARAMPOUR
Front. Struct. Civ. Eng.    2019, 13 (2): 303-323.   https://doi.org/10.1007/s11709-018-0462-x
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In this paper, models of the global system of the Koyna dam have been created using ABAQUS software considering the dam-reservoir-foundation interaction. Non coupled models and the coupled models were compared regarding the horizontal displacement of the dam crest and the differential settlement of the dam base in clay foundation. Meta models were constructed and uncertainty quantification process was adopted by the support of Sobol’s sensitivity indices considering five uncertain parameters by exploiting Box-Behnken experimental method. The non coupled models results determined overestimated predicted stability and damage detection in the dam. The rational effects of the reservoir height were very sensitive in the variation of the horizontal displacement of the dam crest with a small interaction effect with the beta viscous damping coefficient of the clay foundation. The modulus of elasticity of the clay foundation was the decisive parameter regarding the variation of the differential settlement of the dam base. The XFEM approach has been used for damage detection in relation with both minimum and maximum values of each uncertain parameter. Finally the effects of clay and rock foundations were determined regarding the resistance against the propagation of cracks in the dam, where the rock foundation was the best.

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Dynamic crack propagation in plates weakened by inclined cracks: an investigation based on peridynamics
A. SHAFIEI
Front. Struct. Civ. Eng.    2018, 12 (4): 527-535.   https://doi.org/10.1007/s11709-018-0450-1
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Peridynamics is a theory in solid mechanics that uses integral equations instead of partial differential equations as governing equations. It can be applied to fracture problems in contrast to the approach of fracture mechanics. In this paper by using peridynamics, the crack path for inclined crack under dynamic loading were investigated. The peridynamics solution for this problem represents the main features of dynamic crack propagation such as crack bifurcation. The problem is solved for various angles and different stress values. In addition, the influence of geometry on inclined crack growth is studied. The results are compared with molecular dynamic solutions that seem to show reasonable agreement in branching position and time.

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Analysis on running safety of train on the bridge considering sudden change of wind load caused by wind barriers
Tian ZHANG, He XIA, Weiwei GUO
Front. Struct. Civ. Eng.    2018, 12 (4): 558-567.   https://doi.org/10.1007/s11709-017-0455-1
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The calculation formulae for change of wind load acting on the car-body are derived when a train moves into or out of the wind barrier structure, the dynamic analysis model of wind-vehicle-bridge system with wind barrier is established, and the influence of sudden change of wind load on the running safety of the train is analyzed. For a 10-span simply-supported U-shaped girder bridge with 100 m long double-side 3.5 m barrier, the response and the running safety indices of the train are calculated. The results are compared with those of the case with wind barrier on the whole bridge. It is shown that the sudden change of wind load caused by wind barrier has significant influence on the lateral acceleration of the car-body, but no distinct on the vertical acceleration. The running safety indices of train vehicle with sectional wind barriers are worse than those with full wind barriers, and the difference increases rapidly with wind velocity.

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Evaluation of seismic reliability of gravity dam-reservoir-inhomogeneous foundation coupled system
Hamid Taghavi GANJI, Mohammad ALEMBAGHERI, Mohammad Houshmand KHANEGHAHI
Front. Struct. Civ. Eng.    2019, 13 (3): 701-715.   https://doi.org/10.1007/s11709-018-0507-1
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The seismic performance of gravity dam-reservoir-foundation coupled system is investigated utilizing probabilistic approach. In this research, the uncertainties associated with modeling parameters are incorporated in nonlinear response history simulations to realistically quantify their effects on the seismic performance of the system. The methodology is applied to Pine Flat gravity dam and the foundation is considered to be inhomogeneous assuming a constant spatial geometry but with various rock material properties. The sources of uncertainty are taken into account in the reliability analysis using Latin Hypercube Sampling procedure. The effects of the deconvolution process, number of samples, and foundation inhomogeneity are investigated.

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The role of geometrical features in the architectural- structural interaction: Some case studies of the Iranian ancient architecture
Maryam ZANDIYEHVAKILI, Isa HOJAT, Mehdi MAHMUDI
Front. Struct. Civ. Eng.    2019, 13 (3): 716-724.   https://doi.org/10.1007/s11709-018-0508-0
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This research aims to enhance the interaction between a structure and its architectural form. Having a qualitative approach, the present work discovers some successfully used geometrical features of the Iranian ancient architecture in terms of the architectural-structural interaction. We define four qualitative criteria for this assessment, i.e., construction-ability, cost effectiveness, participation of the structure in fulfillment of the visual, and functional-semantic needs of the architectural form. For this purpose, two case studies including the Jamé Mosque of Isfahan and the Soltaniyeh building are investigated. The outcomes of this research help designers to not only design efficient structures by adapting non-load bearing elements with the general form of the structure, but also meet concepts such as the unity or perfectionism in the structure.

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Molecular dynamics investigation of mechanical properties of single-layer phagraphene
Ali Hossein Nezhad SHIRAZI
Front. Struct. Civ. Eng.    2019, 13 (2): 495-503.   https://doi.org/10.1007/s11709-018-0492-4
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Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the influence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

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