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Volume 36, Number 5, September10 2020

The load-slip relationship of the shear connection is an important parameter in design and analysis of composite structures. In this paper, a load-slip curve prediction method of the shear connection based on the artificial neural networks (ANNs) is proposed. The factors which are significantly related to the structural and deformation performance of the connection are selected, and the shear stiffness of shear connections and the transverse coordinate slip value of the load-slip curve are taken as the input parameters of the network. Load values corresponding to the slip values are used as the output parameter. A two-layer hidden layer network with 15 nodes and 10 nodes is designed. The test data of two different forms of shear connections, the stud shear connection and the perforated shear connection with flange heads, are collected from the previous literatures, and the data of six specimens are selected as the two prediction data sets, while the data of other specimens are used to train the neural networks. Two trained networks are used to predict the load-slip curves of their corresponding prediction data sets, and the ratio method is used to study the proximity between the prediction loads and the test loads. Results show that the load-slip curves predicted by the networks agree well with the test curves.

Key Words
load-slip curve; artificial neural networks; shear stiffness; stud shear connection; perforated shear connection with flange heads

Kai Guo: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China;
College of Architecture and Civil Engineering, Beijing University of Technology, Beijinng 100124, China
Guotao Yang: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China

Double skin composite walls are increasingly popular and have been applied to many safety-related facilities. They come from the concept of composite slabs. Conventional connectors such as shear studs and binding bars were used in previous studies to act as the internal mechanical connectors to lock the external steel faceplates to the concrete core. However, the restraint effects of these connectors were sometimes not strong enough. In this research, a recently proposed unique type of steel truss was employed along the wall height to enhance the composite action between the two materials. Concrete-filled tube columns were used as the boundary elements. Due to the existence of boundary columns, the restraints of steel faceplates to the concrete differ significantly for the walls with different widths. Therefore, there is a need to explore the effect of height-to-width ratio on the structural behavior of the wall. In the test program, three specimens were designed with the height of 3000 mm, the thickness of 150 mm, and different widths, to simulate the real walls in practice. Axial compression was applied by two actuators on the tested walls. The axial behavior of the walls was evaluated based on the analysis of test results. The influences of height-to-width ratio on structural performance were evaluated. Finally, discussion was made on code-based design.

Key Words
height-to-width ratio; composite wall; compressive loading; structural behavior; double skin

Ying Qin, Xin Yan and Gan-Ping Shu: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering,
Southeast University, Nanjing, China
Guan-Gen Zhou: Zhejiang Southeast Space Frame Group Company Limited, Hangzhou, China

The behavior variation of concrete dam is investigated, based on a new method for analyzing the data model of concrete dam in service process for the limitation of wavelet transform for solving concrete dam service process model. The study takes into account the time and position of behavior change during the process of concrete dam service. There is no dependence on the effect quantity for overcoming the shortcomings of the traditional identification method. The panel data model is firstly proposed for analyzing the behavior change of composite concrete dam. The change-point theory is used to identify whether the behavior of concrete dams changes during service. The phase space reconstruction technique is used to reconstruct the phase plane of the trend effect component. The time dimension method is used to solve the construction of multi-transformation model of composite panel data. An existing 76.3-m-high dam is used to investigate some key issues on the behavior change. Emphasis is placed on conversion time and location for three time periods consistent with the practical analysis report for evaluating the validity of the analysis method of the behavior variation of concrete dams presented in this paper.

Key Words
panel; concrete dam; behavior variation; data model; conversion time and location

Hao Gu: College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China;
College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China;
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China;
National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing 210098, China
Meng Yang, Chongshi Gu and Huaizhi Su:College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China;
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China;
National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing 210098, China
Wenhan Cao: College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
Xiaofei Huang: Library of Hohai University, Nanjing 210098, China

A finite element analysis (FEA) model is established to investigate the concrete-encased concrete-filled steel tubular (CFST) column to reinforced concrete (RC) beam joints under cyclic loading. The feasibility of the FEA model is verified by a set of test results, consisting of the failure modes, the exposed view of connections, the crack distributions and development, and the hysteretic relationships. The full-range analysis is conducted to investigate the stress and strain development process in the composite joint by using this FEA model. The internal force distributions of different components, as well as the deformation distributions, are analyzed under different failure modes. The proposed connections are investigated under dimensional and material parameters, and the proper constructional details of the connections are recommended. Parameters of the beam-column joints, including material strength, confinement factor, reinforcement ratio, diameter of steel tube to sectional width ratio, beam to column linear bending stiffness ratio and beam shear span ratio are evaluated. Furthermore, the key parameters affecting the failure modes and the corresponding parameters ranges are proposed in this paper.

Key Words
joint; seismic performance; concrete-encased CFST column; reinforced concrete(RC) beam; finite element analysis (FEA); full-range analysis

Dan-Yang Ma and Lin-Hai Han: Department of Civil Engineering, Tsinghua University, Beijing, 100084, P.R. China
Xiao-Ling Zhao: Department of Civil and Environmental Engineering, The University of New South Wales (UNSW), Sydney, NSW 2052, Australia
Wei-Biao Yang: Beijing Institute of Architectural Design, Beijing 100045, P.R. China

Steel-concrete composite structures have been extensively used in building, bridges, and other civil engineering infrastructure. Shear stud connectors between steel and concrete are essential in composite members to guarantee the effectiveness of their behavior in terms of strength and deformability. This study focuses on investigating the shear stiffness of headed studs embedded in several types of concrete with wide range of compressive strength, and their effects on the elastic behavior of steel-concrete composite girders were evaluated. Firstly, totally 206 monotonic push-out tests from the literature were reviewed to investigate the shear stiffness of headed studs embedded in various types of concrete (NC, HPC, UHPC etc.). Shear stiffness of studs is defined as the secant stiffness of the load-slip curve at 0.5Vu, and a formulation for predicting defined shear stiffness in elastic state was proposed, indicating that the stud diameter and the elastic modulus of steel and concrete are the main factors. And the shear stiffness predicted by the new formula agree well with test results for studs with a diameter ranging from 10 to 30 mm in the concrete with compressive strength ranging from 22.0 to 200.0MPa. Then, the effects of shear stiffness on the elastic behaviors of composite girders with different sizes and under different loading conditions were analyzed, the equations for calculating the stress and deformation of simply supported composite girders considering the influence of connection

Key Words
composite girder; headed studs; shear stiffness; elastic behaviors; push-out test

Jun He: School of Civil Engineering, Changsha University of Science and Technology, Hunan, China;
Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh, UK
Zhaofei Lin: Country Garden, Guangdong, China
Yuqing Liu:Department of Bridge Engineering, Tongji University, Shanghai, China
Xiaoqing Xu: School of Civil Engineering, Chongqing University, Chongqing, China
Haohui Xin: School of Human Settlements and Civil Engineering, Xi\'an Jiaotong University, Xi\'an, China
Faculty of Geoscience and Engineering, Delft University of Technology, The Netherlands
Sihao Wang: Department of Bridge Engineering, Tongji University, Shanghai, China

The behavior of composite steel-concrete beams depends on the transmission of forces between two parts: the concrete slab and the steel I-beam. The shear connector is responsible for the interaction between these two parts. Recently, an alternative shear connector, called Truss Type connector, has been developed; it aligns efficient structural behavior, fast construction and implementation, and low cost when compared to conventional connectors applied in composite structures. However, there is still a lack of full understanding of the mechanical behavior of the Truss Type connector, due to its novelty. Thus, this study aims to analyze the influence of variation of geometric and physical parameters on the shear resistance of the Truss Type connector. In order to investigate those parameters, a non-linear finite element model, able to simulate push-out tests of Truss Type connectors, was specifically developed and validated with experimental results. A thorough parametric study, varying the height, the angle between rods, the diameter, and the concrete strength, was conducted to evaluate the shear resistance of the Truss Type connector. In addition, an equation to predict the resistance of the original Truss Type shear connector was proposed.

Key Words
composite structures; truss type connector; finite element modeling; push-out test

Jerfson M. Lima, Luciano M. Bezerra, Ramon S.Y.R.C. Silva and Wallison C.S. Barbosa: Department of Civil and Environmental Engineering, University of Brasília, Brazil
Jorge Bonilla: Department of Applied Mathematics, University of Ciego de Ávila, Cuba

In recent years, the composite columns have been widely used in the structures. These columns are mainly used to construct the structures with a large span and high floor height. Concrete filled tubes (CFTs) are a type of composite column, which are popular nowadays due to their numerous benefits. The purpose of this study is to investigate such frames at elevated temperatures. The method used in this research is based on section 2.2 of Eurocode 4. First, for the verification purpose, a comparison was made between the experimental results and the numerical model of the concrete filled tube. Then a composite frame was analyzed under fire temperature with different parameters. The results showed that the failure time decreased with increasing the friction of different models. Moreover, investigation of the concrete moisture content revealed that an increase in the concrete moisture content from 3% to 10% led to extended failure time for different models. For instance, in the second frame model, the failure time has increased up to 8%.

Key Words
composite sections; concrete filled tube (CFT); frame; fire resistance; FEM modeling; nonlinear analysis

Mahdi Shariati: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
Mohammad Grayeli: Mazandaran University of Science and Technology, Babol, Iran
Ali Shariati:Division of Computational Mathematics and Engineering, Institute for Computational Science,
Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam;
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam
Morteza Naghipour: Civil Engineering Faculty, Babol Noshirvani University of Technology, Babol, Iran

The present manuscript focuses on the flow and heat transfer of the dusty fluid along exponentially stretching cylinder. Enormous attempts are made for fluid flow along cylinder but the study of fluid behavior along exponentially stretching cylinder is discussed lately. Using appropriate transformations, the governing partial differential equations are converted to non-dimensional ordinary differential equations. The transformed equations are solved numerically using Shooting technique with Runge-Kutta method. The influence of the physical parameters on the velocity and temperature profiles as well as the skin fraction coefficient and the local Nusselt number are examined in detail. The essential observations are as the fluid velocity decreases but temperature grows with rise in particle interaction parameter, and both the fluid velocity and temperature fall with increase in mass concentration parameter, Reynold number, Particle interaction parameter for temperature and the Prandtl number.

Key Words
dusty fluid; stretching cylinder; exponential stretching; shooting method; numerical solution

Waheed Iqbal, Muhammad N. Naeem and Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Mudassar Jalil: Department of Mathematics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, 44000 Islamabad, Pakistan
Mohamed A. Khadimallah: Prince Sattam Bin Abdulaziz University, College of Engineering, Civil Engineering Department, BP 655, Al-Kharj, 11942, Saudi Arabia
Hamdi Ayed: Department of Civil Engineering, College of Engineering, King Khalid University, Abha, Kingdom of Saudi Arabia;
Higher Institute of Transport and Logistics of Sousse, University Sousse, Tunisia
Souhail Mohamed Bouzgarrou: Department of Civil Engineering, Faculty of Engineering, Jazan University, Kingdom of Saudi Arabia
S.R. Mahmoud: GRC Department, Faculty of Applied studies, King Abdulaziz University, Jeddah, Saudi Arabia
E. Ghandourah: Department of Nuclear Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia
Muhammad Taj: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Abdelouahed Tounsi: Department of Technology Civil Engineering, Materials and Hydrology Laboratory, University of Sidi Bel Abbes, Algeria;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia

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