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CONTENTS
Volume 25, Number 5, December10 2017
 

Abstract
Cable-supported ribbed beam composite slab structure (CBS) is proposed in this study. As a new cable-supported structure, it has many merits such as long span availability and cost-saving. Inspired by the previous research on cable-supported structures, the fabrication and construction process are developed. Pre-stress design method based on static equilibrium analysis is presented. In the algorithm, the iteration convergence can be accelerated and the calculation result can be kept in an acceptable precision by setting a rational threshold value. The accuracy of this method is also verified by experimental study on a 1:5 scaled model. Further, important parameters affecting the mechanical features of the CBS are discussed. The results indicate that the increases of sag-span ratio, depth of the ribbed beam and cable diameter can improve the mechanical behavior of the CBS by some extent, but the influence of strut sections on mechanical behavior of the CBS is negligible.

Key Words
cable-supported ribbed beam composite slab; spatial structure; pre-stress; fabrication; mechanical features; sag-span ratio

Address
W.T. Qiao: School of Civil Engineering, Shi Jiazhuang Tiedao University, 17 North 2nd Ring Road, Shi Jiazhuang, Hebei, China
D. Wang: TRC Engineers, Inc, 8550 United Plaza Blvd., Suite 502, Baton Rouge, LA, United States
M.S. Zhao: School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore


Abstract
Box sections are symmetrical sections and they have high moment of inertia in both directions, therefore they are good members in tall building structures. For the rigid connection in structures with box column continuity plates are used on level of beam flanges in column. Assembly of the continuity plates is a difficult and unreliable work due to lack of weld or high welding and cutting in the fourth side of column in panel zone, so the use of experimental stiffeners have been considered by researchers. This paper presented an experimental investigation on connection in box columns. The proposed connection has been investigated in four cases which contain connection without internal and external stiffeners(C-0-00), connection with continuity plates(C-I-CP), connection with external vase shape stiffener (C-E-VP) and connection with surrounding plates(C-E-SP). The results show that the connections with vase plates and surrounding plates can respectively increase the ultimate strength of the connection up to 366% and 518% than the connection without stiffeners, in case connection with the continuity plates this parameter increases about 39%. In addition, the proposed C-E-VP and C-E-SP connection provide a rigid and safe connection to acquire rigidity of 95% and 98% respectively. But C-I-CP connection is classified as semi-rigid connections.

Key Words
box column; rigid connection; continuity plate; vase external stiffener; surrounding external stiffener

Address
Omid Rezaifar: Department of Civil Engineering and Research Institute of Novin Technologies, Semnan University, Iran
Mohammad Nazari: Structure Engineering, Faculty of Civil Engineering, Semnan University, Iran
Majid Gholhaki: Department of Civil Engineering, Semnan University, Iran

Abstract
The tubed steel reinforced concrete (SRC) column is a composite column in which the outer steel tube is mainly used to provide confinement on the core concrete. This paper presents experimental and analytical studies on the behavior of circular tubed SRC (TSRC) columns subjected to axial compression. Eight circular TSRC columns were tested to investigate the effects of length-to-diameter ratio (L/D) of the specimens, diameter-to-thickness ratio (D/t) of the steel tubes, and use of stud shear connectors on the steel sections. Elastic-plastic analysis on the steel tubes was used to investigate the mechanism of confinement on the core concrete. The test results indicated that the tube confinement increased the strength and deformation capacity for both short and slender columns, and the effects on strength were more pronounced for short columns. A nonlinear finite element (FE) model was developed using ABAQUS, in which the nonlinear material behavior and initial geometric imperfection were included. Good agreement was achieved between the predicted results using the FE model and the test results. The test and FE results were compared with the predicted strengths calculated by Eurocode 4 and the AISC Standard. Based on the analytical results, a new design method for this composite column was proposed.

Key Words
circular TSRC; axial compression; stability strength; finite element analysis; column curve; design method

Address
Biao Yan: Department of Engineering Mechanics, School of Civil Engineering and Mechanics, Lanzhou University,
No.222, Tianshui Road(south), Chengguan Dstrict, Lanzhou 730000, China
Jiepeng Liu and Xuhong Zhou: Department of Civil Engineering, School of Civil Engineering, Chongqing University,No.174, Shazheng Street, Shapingba District, Chongqing 400044, China



Abstract
Moment-thrust-curvatures (M-P- curves) are fundamental quantities for detailed descriptions of basic properties such as stiffness and strength of a section under axial loads required for accurate computation of the deformations of reinforced concrete or composite columns. Currently, the finite-element-based methods adopting small fibers for analyzing a section are commonly used for generating the M-P- curves and they require large amounts of computational time and effort. Further, the conventional numerical procedure using the force-control method might encounter divergence problems under high compression or tension. Therefore, this paper proposes a divergence-free approach, combining the use of the displacement-control and the Quasi-Newton scheme in the incremental-iterative procedure, for generating the M-P-curves of arbitrary sections. An efficient method for computing the strength from concrete components is employed, where the stress integration is executed by layer-based algorithms. For easy modeling of residual stress, cross sections of structural steel components are meshed into fibers for strength resultants. The numerical procedure is elaborated in detail with flowcharts. Finally, extensive validating examples from previously published research are given for verifying the accuracy of the proposed method.

Key Words
composite; steel; section; numerical; concrete; moment-curvature analysis

Address
Liang Chen, Si-Wei Liuand Siu-Lai Chan: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China


Abstract
The grid structure with bolt-sphere joints is widely adopted by industrial plants with suspending crane. The alternating reciprocating action of the suspending crane will cause fatigue problems of the grid structure with bolt-sphere joints with respect to the rod, the cone, the sealing plate, the bolt ball and the high strength bolt; while the fatigue of the high strength bolt is the key issue of fatigue failure. Based on efficient and smooth loading equipment with the AMSLER fatigue testing machine, this paper conducted a constant amplitude fatigue test on 18 M20 and 14 M30 high strength bolts with 40Cr material, and obtained 19 valid failure points, 9 unspoiled points with more than 2 million cycles, and 4 abnormal failure points. In addition, it established the constant amplitude fatigue design method, and analyzed the stress concentration and the fatigue fracture of high strength bolts. It can be explained that the geometrical stress concentration of high-strength bolt caused by spiral burr is severe.

Key Words
fatigue test; grid structure; bolt sphere joint; high strength bolt connection; suspending crane

Address
Xu Yang and Honggang Lei: College of Architecture and Civil Engineering, Taiyuan University of Technology, 79 West Yingze Street, Taiyuan, Shanxi, People

Abstract
The dynamic instability of truncated conical shells subjected to dynamic axial load within first order shear deformation theory (FSDT) is examined. The conical shell is made from functionally graded (FG) orthotropic material. In the formulation of problem a dynamic version of Donnell\'s shell theory is used. The equations are converted to a Mathieu-Hill type differential equation employing Galerkin\'s method. The boundaries of main instability zones are found applying the method proposed by Bolotin. To verify these results, the results of other studies in the literature were compared. The influences of material gradient, orthotropy, as well as changing the geometric dimensions on the borders of the main areas of the instability are investigated.

Key Words
material gradient; orthotropic material; conical shells; dynamic instability; main instability zones; FSDT

Address
Abdullah H. Sofiyev: Department of Civil Engineering, Faculty of Engineering, Suleyman Demirel University, Isparta, Turkey
Zihni Zerin and Ferruh Turan: Department of Civil Engineering, Faculty of Engineering, Ondokuz Mayis University, Samsun, Turkey
Bilender P. Allahverdiev: Department of Mathematics, Faculty of Arts and Sciences, Suleyman Demirel University, Isparta, Turkey
David Hui: Department of Mechanical Engineering, University of New Orleans, New Orleans, Louisiana, USA
Hakan Erdem: Department of Civil Engineering, Faculty of Engineering, Omer Halisdemir University, Nigde, Turkey



Abstract
Carbon Fiber Reinforced Polymer (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been done on steel beams and steel columns. No independent study, to the researcher\' s knowledge, has studied the effect of CFRP strengthening on steel beam-columns, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel beam-columns. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel beam-columns, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine the ultimate load of SHS steel beam-columns, ten specimens, eight of which were strengthened with the different coverage length and with one and two CFRP layers, with two types of section (Type A and B) were analyzed. ANSYS was used to analyze the SHS steel beam-columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel beam-columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel beam-columns.

Key Words
steel beam-columns; CFRP; strengthening; ultimate load; FE-Method

Address
Amir Hamzeh Keykha: Department of Civil Engineering, Zahedan Branch, Islamic Azad University, Zahedan, Iran

Abstract
This experimental research presents the seismic performance of steel reinforced high-strength concrete (SRHC) short columns. Eleven SRHC column specimens were tested under simulated earthquake loading conditions, including six short column specimens and five normal column specimens. The parameters studied included the axial load level, stirrup details and shear span ratio. The failure modes, critical region length, energy dissipation capacity and deformation capacity, stiffness and strength degradation and shear displacement of SRHC short columns were analyzed in detail. The effects of the parameters on seismic performance were discussed. The test results showed that SRHC short columns exhibited shear-flexure failure characteristics. The critical region length of SRHC short columns could be taken as the whole column height, regardless of axial load level. In comparison to SRHC normal columns, SRHC short columns had weaker energy dissipation capacity and deformation capacity, and experienced faster stiffness degradation and strength degradation. The decrease in energy dissipation and deformation capacity due to the decreasing shear span ratio was more serious when the axial load level was higher. However, SRHC short columns confined by multiple stirrups might possess good seismic behavior with enough deformation capacity (ultimate drift ratio

Key Words
steel reinforced concrete; high-strength concrete; composite column; short column; seismic performance; shear span ratio

Address
Weiqing Zhu: School of Highway, Chang\' an University, Xi\'an710064, P.R. China
Jinqing Jia: Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian116024, P.R. China
Junguang Zhang: Bureau of Traffic Construction Engineering Quality Supervision of Inner Mongolia Autonomous Region, Hohhot 010010, P.R. China

Abstract
In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity (Mu) and moment demand (Md) to plastic moment capacity (Mp) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.

Key Words
progressive collapse; nonlinear static analysis; dynamic increase factor; alternate load path; residual strength

Address
Javad Mashhadia and Hamed Saffari: Department of Civil Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, 22 Bahman Blvd. P.O. Box 76175-133, Kerman, Iran


Abstract
This paper presents a novel approach that describes the first-order (linear elastic) partial interaction analysis of members formed by multi-components based on the Generalised Beam Theory (GBT). The novelty relies on its ability to accurately model the partial interaction between the different components forming the cross-section in both longitudinal and transverse directions as well as to consider the cross-sectional deformability. The GBT deformations modes, that consist of the conventional, extensional and shear modes, are determined from the dynamic analyses of the cross-section represented by a planar frame. The partial interaction is specified at each connection interface between two adjacent elements by means of a shear deformable spring distributed along the length of the member. The ease of use of the model is outlined by an application performed on a multi-component member subjected to an eccentric load. The values calculated with an ABAQUS finite element model are used to validate the proposed method. The results of the numerical applications outline the influence of specifying different rigidities for the interface shear connection and in using different order of polynomials for the shape functions specified in the finite element cross-section analysis.

Key Words
generalised beam theory; partial interaction; steel-concrete members; thin-walled members

Address
Alberto Ferrarotti: School of Civil Engineering, The University of Sydney, Sydney NSW 2006, Australia;
DICCA, Università degli Studi di Genova, Via Montallegro 1 – 16145 Genova, Italy
Gianluca Ranzi: School of Civil Engineering, The University of Sydney, Sydney NSW 2006, Australia
Gerard Taig: ARUP, Sydney NSW 2000, Australia
Giuseppe Piccardo: DICCA, Università degli Studi di Genova, Via Montallegro 1 – 16145 Genova, Italy


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