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Volume 48, Number 1, July10 2023

The main goal of this paper is to study vibration of damaged core laminated sectorial plates with Functionally graded (FG) face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular sector plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions.

Key Words
2-D differential quadrature method; damaged isotropic core; Eshelby-Mori-Tanaka scheme; Halpin-Tsai equation; laminated sectorial plates; three-dimensional theory of elasticity

Liyuan Zhao and Rui Yang: School of Civil Engineering and Architecture, XinXiang University, He nan 453003, China

Man Wang: Zhengzhou University of Science and Technology, He nan, 450064, China

Meng Zhao:Zaha Hadid Limited, London England, EC1R 0BQ

Zenghao Song:Henan Hangjian Anticorrosion Installation Engineering limited Cooperation, He nan 453400, China

N. Bohlooli:School of Civil Engineering, Urmia University, Urmia, Iran

Due to high application of concrete structures in construction industry, however, the quality improvement is essential. One of the new ways for this purpose is adding the nanoparticles to the concrete. In this work, vibration analysis of concrete beams reinforced by graphene oxide (GO) nanoparticles based on mathematical model has been investigated. For the accuracy of the presented model, the experimental study is done for comparing the compressive strength. Since the nanoparticles can not be solved in water without any specific process, at the first, GO nanoparticles should be dispersed in water by using shaker, magnetic striker, ultrasonic devices and finally mechanical mixer. For modelling of the strucuture, sinusoidal shear deformation beam theory (SSDBT) is utilized. Mori-Tanak model model is utilized for obtaining the effective properties of the beam including agglomeration influences. Utilizing the energy method and Hamilton'sprincipal, the motion equations are calculated. The frequency of the concrete beam is obtanied by analytical method. Three samples with 0.02% GO nanoparticles are built and its compressive strength is compared which shows a good accuracy with maximum 1.29% difference with mathematical model and other papers. The aim of this work from the theoretical study is investigating the effects of nanoparticles volume percentage and agglomeration, length and thickness of the beam on the frequency of the structure. The results show that the with enhancing the GO nanoparticles, the frequency is increased. For example, with enhancing the volume percent of GO nanoparticles from zero to 0.08%, the compressive strength is increased 48.91%. and 46.83%, respectively for two cases of with and without agglomeration.

Key Words
analytical method; concrete beam; experimental; GO nanoparticles; vibration

Chencheng Song and Junfeng Shi:College of Civil Engineering, Architecture and Environment, Hubei University of Technology, Wuhan 430070, Hubei, China

Ibrahim Albaijan: 2Mechanical Engineering Department, College of Engineering at Al Kharj, Prince Sattam Bin Abdulaziz University,
Al Kharj 11942, Saudi Arabia

Elhosiny Ali:Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha, Saudi Arabia

Amir Behshad:Faculty of Technology and Mining, Yasouj University, Choram 75761-59836, Iran

Under the long-term effect of corrosive environment, many cold-formed steel (CFS) structures have serious corrosion problems. Corrosion leads to the change of surface morphology and the loss of section thickness, which results in the change of instability mode and failure mechanism of CFS structure. This paper mainly investigates the elastic local buckling behavior of corroded CFS columns. The surface morphology scanning test was carried out for eight CFS columns accelerated corrosion by the outdoor periodic spray test. The thin shell finite element (FE) eigen-buckling analysis was also carried out to reveal the influence of corrosion surface characteristics, corrosion depth, corrosion location and corrosion area on the elastic local buckling behaviour of the plates with four simply supported edges. The accuracy of the proposed formulas for calculating the elastic local buckling stress of the corroded plates and columns was assessed through extensive parameter studies. The results indicated that for the plates considering corrosion surface characteristics, the maximum deformation area of local buckling was located at the plates with the minimum average section area. For the plates with localized corrosion, the main buckling shape of the plates changed from one half-wave to two half-wave with the increase in corrosion area length. The elastic local buckling stress decreased gradually with the increase in corrosion area width and length. In addition, the elastic local buckling stress decreased slowly when corrosion area thickness was relatively large, and then tends to accelerate with the reduction in corrosion area thickness. The distance from the corrosion area to the transverse and longitudinal centerline of the plate had little effect on the elastic local buckling stress. Finally, the calculation formula of the elastic local buckling stress of the corroded plates and CFS columns was proposed.

Key Words
cold-formed steel columns, corrosion, elastic local buckling, finite element analysis, surface morphology

Nie Biao, Hu WeiCheng and Chen HuaPeng:School of Transportation Engineering, East China Jiaotong University, Jiangxi, China

Xu Shanhua and Li AnBang: School of Civil Engineering, Xi'an University of Architecture & Technology, Xi'an, China

Zhang ZongXing:Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering,
China University of Mining & Technology, Xuzhou, China

The impacts of waste tire rubber (WTR) on the bending conduct of reinforced concrete beams (RCBs) are investigated in visualization of experimental tests and 3D finite element model (FEM) using both ANSYS and SAP2000. Several WTR rates are used in total 4 various full scale RCBs to observe the impact of WTR rate on the rupture and bending conduct of RCBs. For this purpose, the volumetric ratios (Vf) of WTR were chosen to change to 0%, 2.5%, 5% and 7.5% in the whole concrete. In relation to experimental test consequences, bending and rupture behaviors of the RCBs are observed. The best performance among the beams was observed in the beams with 2.5% WTR. Furthermore, as stated by test consequences, it is noticed that while WTR rate in the RCBs is improved, max. bending in the RCBs rises. For test consequences, it is clearly recognized as WTR rate in the RCB mixture is improved from 0% to 2.5%, deformation value in the RCB remarkably rises from 3.89 cm to 7.69 cm. This consequence is markedly recognized that WTR rates have a favorable result on deformation values in the RCBs. Furthermore, experimental tests are compared to 3D FEM consequences via using ANSYS software. In the ANSYS, special element types are formed and nonlinear multilinear misses plasticity material model and bilinear misses plasticity material model are chosen for concrete and compression and tension elements. As a consequence, it is noticed that each WTR rates in the RCBs mixture have dissimilar bending and rupture impacts on the RCBs. Then, to observe the impacts of WTR rate on the constructions under near-fault ground motions, a reinforced-concrete building was modelled via using SAP2000 software using 3-D model of the construction to complete nonlinear static analysis. Beam, column, steel haunch elements are modeled as nonlinear frame elements. Consequently, the seismic impacts of WTR rate on the lateral motions of each floor are obviously investigated particularly. Considering reduction in weight of structure and capacity of the members with using waste tire rubber, 2.5% of WTR resulted in the best performance while the construction is subjected to near fault earthquakes. Moreover, it is noticeably recognized that WTR rate has opposing influences on the seismic displacement behavior of the RC constructions.

Key Words
bending behavior, finite element analysis, rupture conduct, reinforced concrete beam, waste tire rubber, earthquake

Memduh Karalar:Department of Civil Engineering, Zonguldak Bulent Ecevit, 71450, K

Corrosion of the headed studs shear connectors is an important factor in the reduction of the durability and mechanical properties of the steel-concrete composite structure. In order to study the effect of stud corrosion on the mechanical properties in the negative moment region of steel-concrete composite beams, the corrosion of stud was carried out by accelerating corrosion method with constant current. Static monotonic loading was adopted to evaluate the cracking load, interface slip, mid-span deflection, and ultimate bearing capacity of four composite beams with varying corrosion rates of headed studs. The effect of stud corrosion on the stiffness of the composite beam's hogging moment zone during normal service stage was thoroughly examined. The results indicate that the cracking load decreased by 50% as the corrosion rate of headed studs increase to 10%. Meanwhile, due to the increase of interface slip and mid-span deflection, the bending stiffness dropped significantly with the same load. In comparison to uncorroded specimens, the secant stiffness of specimens with 0.5 times ultimate load was reduced by 25.9%. However, corrosion of shear studs had no obvious effect on ultimate bending capacity. Based on the experimental results and the theory of steel-concrete interface slip, a method was developed to calculate the bending stiffness in the negative bending moment region of composite beams during normal service stage while taking corrosion of headed studs into account. The validity of the calculation method was demonstrated by data analysis.

Key Words
durability; mechanical performance; negative bending moment region; steel-concrete composite beam; stiffness; studs corrosion

Yulin Zhan:1)Department of bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China
2)Institute of Civil Engineering Materials, Southwest Jiaotong University, Chengdu 610031, China

Wenfeng Huang and Shuoshuo Zhao:Department of bridge Engineering, Southwest Jiaotong University, Chengdu 610031, China

Junhu Shao:School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China

Dong Shen:Wenzhou Qidu Bridge North Branch Bridge Construction Co., Ltd, Wenzhou, Zhejiang 325052, China

Guoqiang Jin:Bridge Science Research Institute Ltd., China Zhongtie Major Bridge Engineering Group, Wuhan, Hubei 430034, China

This paper presents a novel implicit level set method for topology optimization of functionally graded (FG) structures with pre-existing discontinuities (pre-cracks) using radial basis functions (RBF). The mathematical formulation of the optimization problem is developed by incorporating RBF-based nodal densities as design variables and minimizing compliance as the objective function. To accurately capture crack-tip behavior, crack-tip enrichment functions are introduced, and an eXtended Finite Element Method (X-FEM) is employed for analyzing the mechanical response of FG structures with strong discontinuities. The enforcement of boundary conditions is achieved using the Hamilton-Jacobi method. The study provides detailed mathematical expressions for topology optimization of systems with defects using FG materials. Numerical examples are presented to demonstrate the efficiency and reliability of the proposed methodology.

Key Words
smooth boundary; topology optimization; functionally graded material; strong discontinuity; Radial basis function

Thanh T. Banha Luu G. Nam and Dongkyu Lee:Department of Architectural Engineering, Sejong University, Seoul 05006, Republic of Korea

This study investigates the eccentric performance of concrete-filled steel tubular (CFST) stub columns strengthened with steel tube and sandwiched concrete (STSC) jackets. It was revealed that the STSC jacketing method effectively weakened the cracking of concrete in CFST columns on the convex side and the crash on the concave side. Substantial increases in the eccentric bearing capacities were demonstrated after strengthening. A numerical study was further conducted. The decrease in diameter-to-thickness ratio and increase in strength of outer tube contributed to increase in peak load of all components, whereas the increase in sandwiched concrete strength resulted in load increase on itself and had negligible effects on other components. The parametric study showed the effect of inner concrete strength on columns'bearing capacity was magnified after strengthening, whereas that of inner tube thickness was reduced. Within the parameters investigated, high-strength concrete and high-strength steel can be applied without the concern of early abrupt failure of inner low-strength concrete or steel tube.

Key Words
concrete-filled steel tubular columns, eccentric performance, parametric analysis, steel tube and sandwiched concrete jacket

Weijie Li:1)School of Mechanics and Civil Engineering, China University of Mining & Technology-Beijing, Beijing City, 100083, PR China
2)School of Civil Engineering, Wuhan University, Wuhan City,430072, PR China

Yiyan Lu, Yue Huang and Shan Li:School of Civil Engineering, Wuhan University, Wuhan City,430072, PR China

The caving property of top coal is a key factor to the success of top coal caving mining. The influence law of cyclic loading and unloading of hydraulic support on top coal caving is of great significance to improve the recovery rate of top coal. The similar simulation methods were used to study the dynamic evolution of the top coal cracks under the multi-cycle action of the support, and the parameters of top coal cracks were analyzed quantitatively in this paper. The results show that the top coal cracks can be divided into horizontal cracks and vertical cracks under the cyclic loading and unloading of the support. With the increase of the times of the support cycles loading and unloading, the load on the support decreases, the fractal dimension of the cracks increases, the number and total length of the top coal cracks increases, and the top coal caving is getting better. With the increase of the times of multi-cycle loading and unloading, the fractal dimension, total crack length and crack rate of top coal show a trend of rapid increase first and then increase slowly. Both the total length of the top coal cracks and the crack rate basically show linear growth with the change of the fractal dimension. The top coal caving can be well improved and the coal resource recovery rate increased through the multi-cycle loading and unloading.

Key Words
cracks parameters, cyclic loading and unloading, hydraulic support, quantitative analysis, top coal

Huayong Lv:1)School of Architecture and Engineering, Shangqiu Normal University, Shangqiu 476000, China
2)Coal Industry Engineering Research Center of Top-coal Caving Mining, Beijing 100083, China

Fei Liu:College of Emergency Management, Nanjing Tech University, Nanjing 211816, China

Xu Gao:Railway Engineering Research Institute, China Academy of Railway Sciences Corporation Limited, Beijing 100081, China

Tao Zhou:Railway Engineering Research Institute, China Academy of Railway Sciences Corporation Limited, Beijing 100081, China

Xiang Yuan:School of Architecture and Engineering, Shangqiu Normal University, Shangqiu 476000, China

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