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CONTENTS
Volume 37, Number 2, October25 2020
 

Abstract
Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25 and 45 were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.

Key Words
composite beam; bending-torsion combination; nonlinear finite element; restrained torsion and distortion effects; shear lag effect

Address
Li Zhu, Guan Y. Zhao and Xuan Li: School of Civil Engineering, Beijing Jiaotong University, Beijing, China
Jia J. Wang: Department of Civil and Environmental Engineering, University of Huston, Huston, USA
Xue J. Huo: China Railway Major Bridge Reconnaissance & Design Institute Co.,Ltd, Wuhan, China

Abstract
In this research work, the analytical rotating vibration for functionally graded shell with ring supports are restricted to some volume fraction laws based on Rayleigh-Ritz technique. The frequencies of functionally grade cylindrical shells have been investigated for the distribution of material composition of material with two kinds of material. Stability of a cylindrical shell depends highly on these aspects of material with ring supports. The frequency behavior is investigated with fraction laws versus circumferential wave number, length-to-radius and height-to-radius ratios. The frequencies are higher for higher values of circumferential wave number. The frequency first increases and gain maximum value with the increase of circumferential wave mode. Moreover, the effect of angular speed is also investigated. It is examined that the backward and forward frequencies increases and decreases on increasing the ratio of height- and length-to-radius ratios.

Key Words
material composition; wave number; fabrication; cylindrical shell

Address
Mohamed A. Khadimallah: Prince Sattam Bin Abdulaziz University, College of Engineering, Civil Engineering Department, BP 655, Al-Kharj, 11942, Saudi Arabia;
Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Muzamal Hussain and Muhammad Nawaz Naeem: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Khaled Mohamed Khedher: Department of Civil Engineering, College of Engineering,
King Khalid University, Abha 61421, Saudi Arabia;
Department of Civil Engineering, High Institute of Technological Studies, Mrezgua University Campus, Nabeul 8000, Tunisia
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea



Abstract
This paper aims to probabilistically evaluate performance of two types of I beam to box column (IBBC) connection. With the objective of considering the variability of seismic loading demand, statistical features of the inter-story drift ratio corresponding to the second, fifth and eleventh story of a 12-story steel special moment resisting frames are extracted through incremental dynamic analysis at global collapse state. Variability of geometrical variables and material strength are also taken into account. All of these random variables are exported as inputs to a probabilistic finite element model which simulates the connection. At the end, cumulative distribution functions of local seismic demand for each component of each connection are provided using histogram sampling. Through a parametric study on probabilistic local seismic demand, the influence of some geometrical random variables on the performance of IBBC connections is demonstrated. Furthermore, the probabilistic study revealed that IBBC connection with widened flange has a better performance than the un-widened flange. Also, a design procedure is proposed for WF connections to achieve a same connection performance in different stories.

Key Words
IBBC connection; IDA; finite element reliability method; probabilistic local seismic demand

Address
Mohammad Taherinasab and Ali A. Aghakouchak: Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran

Abstract
In this article, for the first time, the seismic behavior of elliptic-braced moment resisting frame (ELBRF) is assessed through a laboratory program and numerical analyses of FEM specifically focused on the development of global- and local-type failure mechanisms. The ELBRF as a new lateral braced system, when installed in the middle bay of the frames in the facade of a building, not only causes no problem to the opening space of the facade, but also improves the structural behavior. Quantitative and qualitative investigations were pursued to find out how elliptic braces would affect the failure mechanism of ELBRF structures exposed to seismic action as a nonlinear process. To this aim, an experimental test of a 1/2 scale single-story single-bay ELBRF specimen under cyclic quasi-static loading was run and the results were compared with those for X-bracing, knee-bracing, K-bracing, and diamond-bracing systems in a story base model. Nonlinear FEM analyses were carried out to evaluate failure mechanism, yield order of components, distribution of plasticity, degradation of structural nonlinear stiffness, distribution of internal forces, and energy dissipation capacity. The test results indicated that the yield of elliptic braces would delay the failure mode of adjacent elliptic columns and thus, help tolerate a significant nonlinear deformation to the point of ultimate failure. Symmetrical behavior, high energy absorption, appropriate stiffness, and high ductility in comparison with the conventional systems are some of the advantages of the proposed system.

Key Words
elliptic-braced moment resisting frame; Failure mechanism; energy dissipation capacity; ductility; nonlinear analysis

Address
Habib Ghasemi Jouneghani and Abbas Haghollahi: Department of Civil Engineering, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
S. Bahram Beheshti-Aval: Department of Civil Engineering, Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran

Abstract
In this paper, the efficiency of five Machine Learning (ML) methods consisting of Deep Learning (DL), Support Vector Machine (SVM), Random Forest (RF), Decision Tree (DT), and Gradient Tree Booting (GTB) for regression and classification of the Ultimate Load Factor (ULF) of nonlinear inelastic steel frames is compared. For this purpose, a two-story, a six-story, and a twenty-story space frame are considered. An advanced nonlinear inelastic analysis is carried out for the steel frames to generate datasets for the training of the considered ML methods. In each dataset, the input variables are the geometric features of W-sections and the output variable is the ULF of the frame. The comparison between the five ML methods is made in terms of the mean-squared-error (MSE) for the regression models and the accuracy for the classification models, respectively. Moreover, the ULF distribution curve is calculated for each frame and the strength failure probability is estimated. It is found that the GTB method has the best efficiency in both regression and classification of ULF regardless of the number of training samples and the space frames considered.

Key Words
gradient boosting; random forest; deep learning; support vector machine; nonlinear inelastic; steel frame

Address
Seung-Eock Kim: Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 05006, South Korea
Quang-Viet Vu: Faculty of Civil Engineering, Vietnam Maritime University, 484 Lach Tray Street, Haiphong city, Vietnam
George Papazafeiropoulos: Department of Structural Engineering, National Technical University of Athens, Zografou, Athens 15780, Greece
Zhengyi Kong: School of Civil Engineering and Architecture, Anhui University of Technology, Ma'anshan 243032, China
Viet-Hung Truong: Faculty of Civil Engineering, Thuyloi University, 175 Tay Son, Dong Da, Hanoi, Vietnam

Abstract
To explore the feasibility of eliminating the longitudinal rebars and stirrups by using ultra-high-performance fiber reinforcement concrete (UHPFRC) in concrete encased steel composite stub column, compressive behavior of UHPFRC encased steel stub column has been experimentally investigated. Effect of concrete types (normal strength concrete, high strength concrete and UHPFRC), fiber fractions, and transverse reinforcement ratio on failure mode, ductility behavior and axial compressive resistance of composite columns have been quantified through axial compression tests. The experimental results show that concrete encased composite columns with NSC and HSC exhibit concrete crushing and spalling failure, respectively, while composite columns using UHPFRC exhibit concrete spitting and no concrete spalling is observed after failure. The incorporation of steel fiber as micro reinforcement significantly improves the concrete toughness, restrains the crack propagation and thus avoids the concrete spalling. No evidence of local buckling of rebars or yielding of stirrups has been detected in composite columns using UHPFRC. Steel fibers improve the bond strength between the concrete and, rebars and core shaped steel which contribute to the improvement of confining pressure on concrete. Three prediction models in Eurocode 4, AISC 360 and JGJ 138 and a proposed toughness index (T.I.) are employed to evaluate the compressive resistance and post peak ductility of the composite columns. It is found that all these three models predict close the compressive resistance of UHPFRC encased composite columns with/without the transverse reinforcement. UHPFRC encased composite columns can achieve a comparable level of ductility with the reinforced concrete (RC) columns using normal strength concrete. In terms of compressive resistance behavior, the feasibility of UHPFRC encased steel composite stub columns with lesser longitudinal reinforcement and stirrups has been verified in this study.

Key Words
concrete encased column; ultra-high-performance fiber reinforcement concrete (UHPFRC); steel-concrete composite; axial compression

Address
Zhenyu Huang: Guangdong Provincial Key Laboratory of Durability of Marine Civil Engineering,
Shenzhen University, Shenzhen 518060, China;
College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China;
Key Laboratory of Impact and Safety Engineering, Ministry of Education, Ningbo University, Ningbo 315211, Zhejiang, China
Xinxiong Huang: Guangdong Provincial Key Laboratory of Durability of Marine Civil Engineering,
Shenzhen University, Shenzhen 518060, China;
College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China;
Guangzhou Expressway Co., Ltd, Guangzhou Communications Investment Group Co., Ltd, Guangzhou 510288, China
Weiwen Li: Guangdong Provincial Key Laboratory of Durability of Marine Civil Engineering,
Shenzhen University, Shenzhen 518060, China;
College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China;
Jiasheng Zhang: CCFED the Fifth Construction & Engineering Co., Ltd, Shenzhen 518000, China


Abstract
In this paper, dynamic buckling of a smart sandwich nanotube is studied. The nanostructure is composed of a carbon-nanotube with inner and outer surfaces coated with ZnO piezoelectric layers, which play the role of sensor and actuator. Nanotube is under magnetic field and ZnO layers are under electric field. The nanostructure is located in a viscoelastic environment, which is assumed to obey Visco-Pasternak model. Non-local piezo-elasticity theory is used to consider the small-scale effect, and Kelvin model is used to describe the structural damping effects. Surface stresses are taken into account based on Gurtin-Murdoch theory. Hamilton principle in conjunction with zigzag shear-deformation theory is used to obtain the governing equations. The governing equations are then solved using the differential quadrature method, to determine dynamic stability region of the nanostructure. To validate the analysis, the results for simpler case studies are compared with others reported in the literature. Then, the effect of various parameters such as small-scale, surface stresses, Visco-Pasternak environment and electric and magnetic fields on the dynamic stability region is investigated. The results show that considering the surface stresses leads to an increase in the excitation frequency and the dynamic stability region happens at higher frequencies.

Key Words
smart sandwich nanotube; dynamic buckling; viscoelastic; surface stresses; zigzag theory

Address
Ahmad Farokhian: Mechanical Engineering group, Pardis College, Isfahan University of Technology, Isfahan 84156-83111, I.R. Iran
Mehdi Salmani-Tehrani: Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111, I.R. Iran

Abstract
Vibration response in a sandwich plate with a nanocompiste core covered by magnetic layer is presented. The core is armed by functionalyy graded-carbon nanotubes (FG-CNTs) where the Mori-Tanaka law is utilized assuming agglomeration effects. The structure plate is located on elastic medium simulated by Pasternak model. The governing equations are derived based on Mindlin theory and Hamilton' s principle. Utilizing diffrential quadrature method (DQM), the frequency of the structure is calculated and the effects of magnetic layer, volume percent and agglomeration of CNTs, elastic medium and geometrical parameters of structure are shown on the frequency of system. Results indicate that with considering magnetic layer, the frequency of structure is increased.

Key Words
magnetic layer; nanocomposite plate; vibration; DQM; FG-CNT

Address
Yan Cao: School of Mechatronic Engineering, Xi'an Technological University, Xi'an, 710021 China
Farayi Musharavati:Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, P.O. Box 2713, Doha, Qatar
Shahrizan Baharom: Department of Civil Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM,
43600, Bangi, Selangor, Malaysia
Pouyan Talebizadehsardari: Metamaterials for Mechanical, Biomechanical and Multiphysical Applications Research Group, Ton Duc Thang University,
Ho Chi Minh City, Vietnam;
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
Tamer A. Sebaey: Engineering Management Department, College of Engineering, Prince Sultan University, Riyadh, Saudi Arabia;
Mechanical Design and Production Department, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Sharkia, Egypt
Arameh Eyvazian: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
Faculty of Electrical – Electronic Engineering, Duy Tan University, Da Nang 550000, Vietnam
Azlan Mohd Zain: UTM Big Data Centre, Universiti Teknologi Malaysia 81310 Johor Malaysia





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