Moment-rotation model of single-web angle connections

Kong, Zhengyi,Kim, Seung-Eock Pergamon Press 2017 International journal of mechanical sciences Vol.126 No.-

<P>The objective of this study is to develop a more accurate model to predict moment-rotation model for single-web angle connections. As the characteristics of connections affect the distribution of inner force and displacement of structure, the effects of connections must be incorporated in the analysis of the structural system. The developed finite element models using ABAQUS software are verified by comparison with previous experiments conducted by others. Several parameters, such as the material properties of angle, length of angle, gage distance, thickness of angle, and number of bolts are investigated in this study. Two different types of moment-rotation relationship, TYPE I and TYPE II, corresponding to different failure modes were established. In TYPE I, the connection angle fails by yielding. In TYPE II, the bolt fails by shear or the bolt hole of connection angle is torn. Failure mode factor was proposed to distinguish them. A simpler inverse hyperbolic sine function model for TYPE I and a hyperbolic tangent function model for TYPE II were developed. These two hyperbolic function models agree well with the various test results.</P>

Numerical estimation of the initial stiffness and ultimate moment capacity of single-web angle connections

Kong, Zhengyi,Kim, Seung-Eock Elsevier 2016 Journal of constructional steel research Vol.121 No.-

<P><B>Abstract</B></P> <P>Single-web angle connections bolted to the beam web and the column flange are studied to investigate the effect of the thickness, length, and material properties of the angles, number of bolts, and gage distances of the fasteners on their moment–rotation behavior. ABAQUS software is used to analyze the nonlinear behavior of a single-web angle connection. Identical geometric and material properties with Lipson's test are utilized to verify the finite element models. A simpler and more accurate equation for the initial stiffness is suggested, and good agreement between the proposed model and Lipson's test data is demonstrated. The type of collapse mechanisms for single-web connection is established. The ultimate moment capacity modified from Kishi and Chen's equation is also proposed, and it agrees well with Lipson's test data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simpler and more accurate equation for the initial stiffness is suggested. </LI> <LI> The type of collapse mechanism is established. </LI> <LI> The effective length ratio of the angle is proposed. The ultimate moment capacity modified from Kishi and Chen's equation is proposed. </LI> </UL> </P>

Numerical Estimation for Initial Stiffness and Ultimate Moment of Top-Seat Angle Connections without Web Angle

Kong, Zhengyi,Kim, Seung-Eock American Society of Civil Engineers 2017 Journal of structural engineering Vol.143 No.10

<P>This paper develops new models predicting the initial stiffness and ultimate moment of top-seat angle connections without web angle (TSACs). The TSACs, bolted to the beam flange and the column flange, are studied to investigate the effect of the material properties of the angle, gauge distance, angle thickness, angle length, rows of bolts, depth of beam, bolt diameter, and thickness of column flange in their moment-rotation behavior. The finite-element method is used to analyze the nonlinear behavior of TSACs. Identical geometric and material properties with previous experiments by others are utilized to verify finite-element models. A more accurate equation for the initial stiffness is suggested, and good agreement between the proposed model and the various test data is shown. The type of collapse mechanisms for TSACs is established. The ultimate moment capacity modified from Kishi and Chen's equation also is proposed, and it agrees well with the various test data. (C) 2017 American Society of Civil Engineers.</P>

Experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete column subjected to eccentric compression

Yu, Feng,Kong, Zhengyi,Li, Deguang,Vu, Quang-Viet Techno-Press 2020 Advances in concrete construction Vol.10 No.2

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

Behavior of composite CFST beam-concrete column joints

Seung-Eock Kim,Ji-Hun Choi,Thai-Hoan Pham,Viet-Hung Truong,Zhengyi Kong,Nguyen-Thê Duong,Quang-Viet Vu 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.1

This paper introduces a new composite joint, which is the composite CFST beam- concrete column joint, and it is more convenient for transportation and erection than conventionally welded joints. The main components of this joint include steel H-beams welded with CFST beams, reinforced concrete columns, and reinforced concrete slabs. The steel H-beams and CFST beams are connected with a concrete slab using shear connectors to ensure composite action between them. An experimental investigation was conducted to evaluate the proposed composite joint performance. A three-dimensional (3D) finite element (FE) model was developed and analyzed for this joint using the ABAQUS/explicit. The FE model accuracy was validated by comparing its results with the relevant test results. Additionally, the parameters that consisted of the steel box beam thickness, concrete compressive strength, steel yield strength, and reinforcement ratio in the concrete slab were considered to investigate their influence on the proposed joint performance.

Study on Bond-Slip Behaviors of Self-Stressing Steel Slag Concrete-Filled Steel Tube

Feng Yu,Taiyao Chen,Kang Niu,Shilong Wang,Zhengyi Kong,Yuan Fang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.11

The bond-slip behaviors of self-stressing steel slag concrete filled steel tubes (SSSSCFST) are investigated by carrying out the push-out tests. The influence of thickness to diameter ratio, confining parameter and expansion ratio of steel slag concrete (SSC) on bond-slip performance are analyzed. Investigations of the failure modes of each specimen indicate that the shear failure of the bond interface dominates the failure of the specimen. Further, three stages of the load-slip relationship curve of bond slip was observed, i.e., the loading stage, descending section and constant load section. In the loading section, with the increase in thickness to diameter ratio or confining parameter, the interface bonding force of specimen improves firstly and then decreases. Besides, the interfacial bond strength increases with enhancement of the expansion ratio. In the descending section, the interfacial bonding force raises with improvement of diameter-thickness ratio, while decreases as the confining parameter and expansion ratio increase. Moreover, the influence of considered parameters on the ultimate interface bond load is analyzed. Finally, a theoretical model for the bond-slip behaviors of SSSSCFST is proposed by accounting for the non-uniform distribution of interface bond strength. It indicates that the theoretical model can well capture the main features that are exhibited during the whole process of push-out test.

Comparison of machine learning algorithms for regression and classification of ultimate load-carrying capacity of steel frames

Seung-Eock Kim,Quang-Viet Vu,George Papazafeiropoulos,Zhengyi Kong,Viet-Hung Truong 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.2

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.

Hepatitis C Virus Non-structural Protein NS4B Can Modulate an Unfolded Protein Response

Zheng Yi,Gao Bo,Ye Li,Kong Lingbao,Jing Wei,Yang Xiaojun,Wu Zhenghui,Ye Linbai The Microbiological Society of Korea 2005 The journal of microbiology Vol.43 No.6

Viral infection causes stress to the endoplasmic reticulum (ER). The response to endoplasmic reticulum stress, known as the unfolded protein response (UPR), is designed to eliminate misfolded proteins and allow the cell to recover. The role of hepatitis C virus (HCV) non-structural protein NS4B, a component of the HCV replicons that induce UPR, is incompletely understood. We demonstrate that HCV NS4B could induce activating transcription factor (ATF6) and inositol-requiring enzyme 1 (IRE1), to favor the HCV subreplicon and HCV viral replication. HCV NS4B activated the IRE1 pathway, as indicated by splicing of X box-binding protein (Xbp-1) mRNA. However, transcriptional activation of the XBP-1 target gene, EDEM (ER degradation-enhancing $\alpha-mannosidase-like$ protein, a protein degradation factor), was inhibited. These results imply that NS4B might induce UPR through ATF6 and IRE1-XBP1 pathways, but might also modify the outcome to benefit HCV or HCV subreplicon replication.