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CONTENTS
Volume 41, Number 1, October10 2021
 

Abstract
This paper proposes a NSTS (new steel tube slab) structure by connecting the longitudinal steel tubes with small steel tubes in transverse, in order to decrease the construction difficulty and improve the bearing capacity of existing NTR (new tubular roof) or STS (steel tube slab) structures. Experimental study on the bending performance and influences of following parameters are carried out: the connection type of the steel tube, the diameter and eccentricity of the small steel tube, and the thickness of the bottom steel plate. The results show that the NSTS members present progressive ductile flexural failure under concentrated load. The connection type has important effect on the mechanical behavior, and the bolts fixed T-shaped plate (B+T) connection method, which provides much higher bending stiffness, is proved to be the most reliable connection type. The increase of small steel tube diameter enhances the bending performance as expected, which also confirms the effectiveness of the B+T connection, while the tube eccentricity presents little impact on the bearing capacity. The bottom steel plate significantly improves the bearing capacity and stiffness and reduces the mid-span deflection. Furthermore, the bending capacity calculation method is proposed and the calculated values show good agreement with the test results. Also, the effect rules of the diameter-thickness ratio of the small tube, the length-diameter ratio of the member and the thickness variety of the bottom steel plate on the bending capacity of NSTS members are further investigated based on the proposed theoretical method.

Key Words
bearing capacity; bending performance; connection type; new steel tube slab structure; steel tube connection;

Address
Xue Li, Lianguang Wang, Bailing Chen and Yaosheng Zhang: College of Resources and Civil Engineering, Northeastern University, Shenyang China

Abstract
A new self-centering slotted friction device (SC-SFD) is introduced for seismic retrofit and upgrading of beam-column joints. The device can be used for existing or new structures. A framework utilizing a performance-based seismic design procedure combined with a genetic algorithm (GA) optimization is used to obtain the optimum design variables of the device. A 5-story building and one-story industrial structure are used as case studies. The effectiveness of the proposed retrofit is assessed through conducting non-linear time-history response analysis (NLTHA), incremental dynamic analysis (IDA), fragility analysis, and seismic life cycle cost (LCC) evaluation. The obtained results demonstrate that the proposed retrofit is effective in reducing the maximum inter-story drift ratio (MIDR) significantly and in eliminating the residual drift. Additional engineering demand parameters, such as the floor acceleration and the base shear have been investigated to prove the superiority of the proposed retrofit technique compared to the fully rigid joint alternative. A finite element method (FEM) is used to ensure that concrete stresses after retrofit are within the acceptable limits. The retrofitted models show high energy dissipating potential compared to the bare cases. The IDA and fragility analyses show significant improvement in the retrofitted structures in terms of the median collapse capacity and seismic fragility. The probabilities of exceeding different limit states and the LCC of the retrofitted structures have been reduced significantly compared to the bare cases. Based on these findings, the proposed retrofit is recommended for similar structures to improve their resilience against earthquakes and to reduce the total seismic LCC.

Key Words
fragility analysis; incremental dynamic analysis; LCC; seismic retrofit; self-centering

Address
Mohamed Noureldin, Shabir Ahmed and Jinkoo Kim: Department of Civil and Architectural Engineering, Sungkyunkwan University, Suwon, Korea

Abstract
The current investigation presents hygro-thermo-mechanical analysis of simply supported anti-symmetric composite plates by using an original computational four unknown's quasi-3D inverse tangent hyperbolic theory. The developed formulations take into account the thickness stretching effect and contain indeterminate integral variables to reduce the number of unknowns. The present model ensures the transverse shear stresses nullity at the top and the bottom surfaces without using any shear correction factor. The governing equations are determined with the help of virtual work principle. The analytical solution of the hygro-thermo-mechanical analysis is derived via Navier's procedure. The accuracy and efficiency of current model is checked by comparing the results with others models found in the literature. Several numerical results are presented in graphs form to show the effects of the aspect, geometry and modulus ratio on the stress and transverse displacement of the simply supported anti-symmetric composite plates.

Key Words
composite plate; hygro-thermo-mechanical analysis; quasi-3D HSDT; virtual work principle

Address
Anfel Ameri and Kouider Halim Benrahou: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelkader Fekrar: Department of Civil Engineering, Faculty of Technology, University of Sidi Bel Abbes, Algeria
Fouad Bourada: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Département des Sciences et de la Technologie, université de Tissemsilt, BP 38004 Ben Hamouda, Algérie
Mahmoud M. Selim: Department of Mathematics, Al-Aflaj College of Science and Humanities,
Prince Sattam bin Abdulaziz University, Al-Aflaj 710-11912, Saudi Arabia
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran,
Eastern Province, Saudi Arabia
Muzamal Hussai: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

Abstract
Prefabricated steel-concrete composite structure has the advantages of large bearing capacity, reliable connection, and good durability, which is of great significance to the development of building industrialization. In this paper, a finite element model (FEM) of the modular prefabricated SRC column-steel beam composite joint is established and verified its accuracy through ABAQUS. The effects of various parameter variables on the hysteresis curve, skeleton curve, ductility, energy consumption, and performance deterioration are investigated. The results show that as the axial compression ratio increases, the joint bearing capacity first increases and then decreases, the strength and stiffness have relatively stable degradation characteristics. However, the hysteresis curve has a certain "pinch" phenomenon, which reduces the energy consumption performance. Different column end bolts margin and apertures have little effect on the bearing capacity, strength and stiffness degradation performance, but affect energy consumption and ductility. The width-to-thickness ratio of the square steel tube has a greater impact on the bearing capacity, energy consumption and ductility, and has less impact on the strength and stiffness degradation performance. As the thickness of the joint cover plate increases, the bearing capacity, energy consumption and initial stiffness of the joint gradually increase, the ductility first increases and then decreases.

Key Words
beam-to-column joints; FEM analysis; parametric analysis; prefabricated composite structure; reciprocating loading;

Address
Cheng Long Wu, Jian Cheng Kan, Qi Hui Wang, Ji Ming Liu and Zun Qiang Li: Department of Civil Engineering, Qingdao University of Technology, Qingdao, Shandong 266033, China

Abstract
Several methods derived for use on traditional concrete curved box girders (CBGs) are used in design practice. However, these typically consider only one elastic modulus and one shear modulus, and consequently cannot be applied directly to CBGs with corrugated steel webs (CSWs) due to the large shear deformations and small longitudinal stiffness of CSWs, while these shear deformations are small and usually ignored for common concrete webs. In this paper, firstly, the flexure-torsion governing differential equations considering the shear deformations and the accordion effect of CSWs, and the distortion governing differential equation considering the accordion effect of CSWs are derived for CBGs with CSWs. A practical method which can solve the deflections, torsional angles, distortional angles, stresses and internal forces of simple and continuous CBGs with intermediate diaphragms is proposed. Secondly, the results of a series of tests performed on three CBGs with CSWs, published test results, as well as finite element analysis results and theoretical results of straight box girders (SBGs) with CSWs are used to verify the correctness of the analytical method. The agreement between analytical, experimental and numerical results is good. Finally, a parametric analysis is conducted and the results show that: (a) the influence of shear deformations of CSWs on the deflections of CBGs with CSWs increases with increasing curvature radius R. For SBGs with CSWs, the deflections may increase by 30% when considering shear deformations. For CBGs with CSWs, the deflection increase ranges between 8% and 30% for concentrated loads depending on the curvature radius. (b) the distortional shear stress, which is small and typically neglected for CBGs with concrete webs, may be as big as, or larger than the flexural shear stress, and must be considered. The restrained torsional shear stress, which is also small and typically neglected for CBGs with concrete webs, can reach 9% of the flexural shear stress, and also must be considered.

Key Words
corrugated steel webs; curved box girders; distortional property; experimental work; finite element analysis; flexural property; torsional property

Address
Sumei Liu: School of Architectural Engineering, Jinling Institute of Technology, Nanjing, 211169, China;
School of Civil Engineering, Southeast University, Nanjing, 211189, China;
Department of Structural Engineering and Building Materials, Faculty of Engineering and Architecture,
Ghent University, Ghent, 9000, Belgium
Wouter De Corte: Department of Structural Engineering and Building Materials, Faculty of Engineering and Architecture,
Ghent University, Ghent, 9000, Belgium
Hanshan Ding: School of Civil Engineering, Southeast University, Nanjing, 211189, China
Luc Taerwe: Department of Structural Engineering and Building Materials, Faculty of Engineering and Architecture,
Ghent University, Ghent, 9000, Belgium;
College of Civil Engineering, Tongji University, Shanghai, 200092, China

Abstract
In this paper, a three-dimensional finite element model (FEM) was established to study the performance of sliding resistance on the diagonal bracing joints of prefabricated steel frame (PSF) connected with self-tapping screw. In addition, the load-displacement curves of the joints were well verified by the test results, and a parametric study was conducted using the validated models to investigate the effect of steel grade, thickness of the tapped plate, the margin of bolt hole, the end and the central distance of bolt hole. The results showed that with the increase of steel grade, thickness of the tapped plate and the distance of the bolt holes, the anti-slide stiffness and the ultimate bearing capacity of the joint were significantly improved. It was recommended that steel grade should be Q345, Q390 or above. It was advisable to take the thickness of the tapped plate at 0.7d0 ~ 1.0d0, take the margin of bolt hole at 1.2d0 ~1.6d0, the central and the end distance of bolt hole should be greater than 2.0d0 and 1.2d0, respectively. The results could provide reference for engineering design.

Key Words
diagonal bracing joint; parametric analysis; prefabricated steel frame; self-tapping screw; tapped plate

Address
Zhenhua Xu, Guoliang Bai, Biao Liu, Jiarui Li and Yifan Yang: College of Civil Engineering, Xi

Abstract
This study aims to investigate the structural performance of glass fiber reinforced polymer (GFRP) reinforced recycled aggregate concrete (RAC) columns (GFRAC columns) under different loading conditions. The structural performance of GFRAC columns is compared with steel rebars reinforced recycled aggregate concrete columns (STRAC columns). Eighteen samples with geometric measurements of 250 mm and 1150 mm for diameter and height, correspondingly, were fabricated including nine samples with GFRP rebars and hoops and nine samples with steel rebars and hoops. The results depicted that the average axial load-carrying capacity of GFRAC columns was 7.8% lesser than that of STRAC columns. The GFRAC columns presented larger deformation capacity indices. Both GFRAC and STRAC columns depicted similar damage behavior and portrayed substantial lessening in the axial load-carrying capacity because of the eccentric loadings. An analytical model for calculating the axial load-carrying capacity of GFRAC columns was proposed based on a large experimental database of GFRP reinforced samples. A close correlation was detected between the testing outcomes and the theoretical estimates for GFRAC columns, which solidly substantiates the accuracy of the proposed model.

Key Words
axial load-carrying capacity; deformation capacity; eccentricity; GFRP bars; recycled aggregate concrete; theoretical model

Address
Liaqat Ali: College of Civil Engineering & Architecture, Zhejiang University, Hangzhou 310058, China
Mohamed Hechmi El Ouni and Nabil Ben Kahla: Department of Civil Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61411, Kingdom of Saudi Arabia;
Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, La Marsa, Tunis 2078, Tunisia
Ali Raza1: Department of Civil Engineering, University of Engineering and Technology, Taxila, 47050, Pakistan


Abstract
The steel-reinforced concrete-filled steel tubular column (SRCFT) is a new form of composite columns. Before widely accepted in engineering practice, its fire behaviour shall be fully understood. Four representative circular SRCFT stub columns were built and tested to failure under ISO fire herein. The tests explored the effect of reinforced steel, the internal or external heating condition and load ratios. The experimental results indicated that the inserted section steel significantly improved the fire resistance of circular SRCFT columns. The non-uniform fire condition did not produce a detrimental effect on the fire response of the specimen. The numerical model was developed and validated against the experimental results. Then a parametric study was present to evaluate the effect of load level, eccentricity and heating conditions. A comparison was made to check the accuracy of a widely accepted design method. The comparison indicated the design method was generally 36% conservative for axially loaded condition and 25% un-conservative for eccentrically loaded condition.

Key Words
experiments; fire resistance; non-uniform fire; numerical modelling; steel-reinforced CFT columns

Address
Fan-Qin Meng: Department of Civil Engineering, Shanghai Normal University, Shanghai, China
Department of Civil and Environmental Engineering, The University of Auckland, Auckland, New Zealand
Mei-Chun Zhu: Department of Civil Engineering, Shanghai Normal University, Shanghai, China
G. Charles Clifton and James B.P. Lim: Department of Civil and Environmental Engineering, The University of Auckland, Auckland, New Zealand
Kingsley U. Ukanwa: Structural Engineer, Aurecon Auckland, New Zealand


Abstract
Shear lag is one of the governing phenomena considered in the design of flanged flexural members. The effect of the location of load on shear lag is not well understood yet. This paper presents a study to understand the shear lag behavior in the concrete slab of bonded steel-concrete composite flexural members, conducted with the help of a developed three-dimensional finite element model. The effect of the location of load on shear lag behavior is studied with the help of twelve loading arrangements at the service and the ultimate loads. Three effective widths based on different design criteria are used to understand the effect of the location of load on effective width. These effective widths are effective width for deflection at the service load, effective width for maximum stress at the service load, and effective width for bending moment capacity at the ultimate load. The shear lag behavior is found to be significantly affected by the location of the load. Increase in scaled eccentricity causes shear lag to vary from positive to negative.

Key Words
bonded; composite beams; composite flexural members; effective width; FE analysis; negative shear lag; shear lag

Address
Ankit Bhardwaj: Department of Civil Engineering, Government Engineering College Bharatpur, Bharatpur - 321303, India;
Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India
Ashok K. Nagpal and Vasant Matsagar: Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India
Sandeep Chaudhary: Department of Civil Engineering, Indian Institute of Technology Indore, Simrol, Indore - 453552, India



Abstract
The curved composite box-girders (CBGs) with corrugated steel webs (CSWs) have been used widely in bridges due to their great advantages and the demand of the road alignment, but the curvature makes both the static and dynamic behaviors more complex. To research the free vibration performance of the curved CBGs with CSWs, 5 simply-supported test girders were designed with the span-to-radius ratio (n=L/R), the number of the cells of the box section, and the number of the diaphragms as parameters. The natural frequencies and mode shapes were measured in the experiment. The experimental results were compared with the numerical results using ANSYS software, and a satisfying agreement was obtained. The parametric analysis shows that for the curved CBG with CSWs, the vertical mode shapes are combined flexural and torsion, and the contribution of the torsional effects to the mode shapes and frequencies improve with the increase of n, which leads to a decrease in the vertical and lateral frequencies and increase in the torsional frequency. The corrugated angle of the steel web has little effect on the natural frequencies of the curved CBGs with CSWs. Increasing the thickness of the steel web and the number of the diaphragms can improve the torsional rigidity of the curved CBG with CSWs effectively; while the deck width has a great contribution on the lateral rigidity.

Key Words
corrugated steel web; curved composite girder; experimental research; free vibration; numerical analysis

Address
Yunsheng Li and Yanling Zhang: Department of Civil Engineering, Shijiazhuang Tiedao University, 17 Northeast, Second Inner Ring, Shijiazhuang, Hebei, China;
Key laboratory of Roads and Railway Engineering Safety Control of Ministry of Education,
Shijiazhuang Tiedao University, Shijiazhuang 050043, China
Qingnian Dai: State Key Laboratory for Health and Safety of Bridge Structures, Wuhan 430034, China
Chaoxing Liu: China Railway Bridge & Tunnel Technology Co., Ltd., Nanjing 210000, China



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