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Volume 40, Number 5, September10 2021

This paper investigated tensile behaviours of S30408 at the Arctic low temperatures (T) of -80~20C. A cooling chamber equipped with liquid nitrogen gas was adopted to rebuild the Arctic low-temperature environment. Standard tension tests were performed on 48 coupons with different thickness at different T values of -80, -60, -30, and 20C. Test results revealed the ductile failure mode of stainless steel S30408 even at -80C. The tensile stress-strain (o-e) curves of S30408 at ambient temperatures exhibited a long strain hardening plateau. Meanwhile, the low-temperature tensile o-e curves of S30408 were different from those at ambient temperatures, which exhibited a second hardening stage with a larger slope than the first hardening. The decreasing T generally increased the elastic modulus, yield and ultimate strength, but reduced the ductility of S30408. Decreasing the T from 20 to -80 reduced the ductility of S30408 by about 28%, but improved the elastic modulus, yield and ultimate strength by about 20%, 22%, and 75%, respectively. This paper also adopted the best subset regression analysis method to develop empirical formulae on estimating influences of T on mechanical properties of S30408. Validations of the predictions by these empirical formulae against the test results in the literature proved their accuracies.

Key Words
Arctic structures; cold region; low temperature; mechanical properties; stainless steel; stress-strain curve; tensile test

Jia-Bao Yan and Yun-Biao Luo: Key Laboratory of Coast Civil Structure Safety of Ministry of Education, Tianjin University, Tianjin 300350, China;
School of Civil Engineering, Tianjin University, Tianjin 300350, China
Zhicheng Lin and Yanbo Li: School of Civil Engineering, Tianjin University, Tianjin 300350, China
Peng Xie: School of Marine Engineering and Technology, Sun Yat-Sen University, Zhuhai, Guangdong 519082, China

Circular economy is an economic system aimed at minimizing wastes and making the most of the current resources. This regenerative approach contrasts with the traditional linear economy, which has been adopted by the construction industry. Developing new construction technologies for sustainable built environment is a top priority for the construction industry throughout the world. Much of the environmental impact from the construction industry is associated with the consumption of resources and generation of waste. The construction industry in Europe consumes over 70,000 million tonnes of materials each year and generates over 250 million tonnes of waste. Composite flooring formed by connecting the concrete slabs to the supporting steel beams has been widely used for many years and is well established as one of the most efficient floor systems in multi-storey steel frame building structures. However, shear connectors are welded through the steel decking to the steel beams and cast into the concrete; this made deconstruction and reuse of these components almost impossible. A new composite flooring system which allows for the reuse of the steel beams and composite floor slabs is developed and tested to assess its potential and suitability for reuse. This paper presents the results of a series of full-scale beam tests and demonstrates the reusability of this new form of composite flooring systems. Simplified hand calculations are also provided and compared against beam tests.

Key Words
circular economy; demountable shear connectors; design for deconstruction; design to Eurocodes, composite beam tests; reusable composite floor system

Dennis Lam, Jie Yang, Xianghe Dai, Therese Sheehan and Kan Zhou: Department of Civil and Structural Engineering, Faculty of Engineering and Informatics, University of Bradford, Bradford, United Kingdom
Yong Wang: Department of Mechanical, Aerospace & Civil Engineering, University of Manchester, United Kingdom

In this study, the vibration serviceability of a composite steel-bar truss slab with steel girder system considering the human-structure interaction was investigated systematically through the on-site testing. Impulse excitations (heel-drop and jumping) and steady-state motions (walking and running) were performed to capture the primary vibration parameters (natural frequency, model shape, and damping ratio) and the distribution of peak accelerations. The composite floor possesses a low frequency of approximately 7.90 Hz and the damping ratio of ≈ 2.10%. The walking and running excitations by one person (single excitations) were considered to evaluate the vibration serviceability of the composite floor. The measured accelerations show a satisfactory vibration perceptibility. For design convenience and safety, a crest factor B rp (the ratio of peak acceleration to root-mean-square acceleration induced from an excitation) is proposed. Comparisons of the modal parameters determined from the tests (walking, running, heel-drop, and jumping) reveal there is an interaction exists between the human excitation and the composite floor. This interaction effect reduces the damping ratio of the composite floor.

Key Words
composite floor; composite steel-bar truss slab; human-structure interaction; steel girder; vibration serviceability

Liang Cao: Key Laboratory for Damage Diagnosis of Engineering Structures of Hunan Province, Hunan University, Changsha, China
Yongchao Tan: School of Civil Engineering, Central South University, Changsha 410075, China
Jiang Li: School of Civil Engineering, Chongqing University, Chongqing 400045, China

In this study, an H-section steel beam with circular holes in a web wrapped with ceramsite concrete (SBWCC) was studied. Static load-bearing capacity tests and finite element analysis were performed on two groups of specimens with different sections. The H-section steel and wrapped ceramsite concrete were well bonded. The load-bearing capacity of the SBWCC was 10% larger than that of the pure H-section steel beam without holes in the web, except for its dead weight. The stiffness of the SBWCC was slightly larger than that of the pure H-section steel beam without holes. The wrapped ceramsite concrete avoided the elastic local instability of the steel beam flange and web. Based on the finite element model verified by experiments, the influences of hole diameter, hole spacing, and U-shaped stirrups on the flexural capacity of the specimens were analyzed. The formulas for the load-bearing capacities and short-term stiffness of the SBWCC were proposed and verified by tests and finite element analysis.

Key Words
ceramsite concrete; flexural performance test; load-bearing capacity; short-term stiffness; steel beam wrapped with concrete

Xuechun Liu and Ailin Zhang: Beijing Engineering Research Center of High-Rise and Large-Span Pre-stressed Steel Structures,
Beijing University of Technology, Beijing, 100124, PR China;
Beijing Key Laboratory of Earthquake Engineering and Structural Retrofit, Beijing University of Technology, Beijing, 100124, PR China
Kun Meng and Tao Zhu: Beijing Engineering Research Center of High-Rise and Large-Span Pre-stressed Steel Structures,
Beijing University of Technology, Beijing, 100124, PR China
Cheng Yu: Construction Engineering Technology Department of Engineering Technology, University of North Texas, Denton, TX 76207, USA

The mechanical and thermal buckling analysis of laminated composite plates is presented in this document. Different theories of thick plates taking into account the parabolic distribution of transverse shear stresses and satisfying the condition of zero shear stresses on the top and bottom surfaces without using shear correction factor are presented and a comparison between the results obtained by these theories is also illustrated. The high order nonlinear stress-displacement relation of the plates was taken into consideration. The principle of potential energy is used to obtain the equations of equilibrium. The closed-form solutions of symmetric and antisymmetric cross-ply are obtained using Navier solution. Using math software Maple, the temperatures and the critical loads of buckling are determined. Finally, a parametric study of the influence of the various parameters such as: mode of buckling, the geometrical ratios a / b and a / h, Young's modulus, Coefficient of thermal expansion, loading type, the orientation of the fibers and the number of layers on the critical buckling temperature and the critical buckling charge is shown and discussed. Numerical results indicate that deformation due to transverse shear has a significant effect on both mechanical and thermal behavior of buckling of laminated simply supported plates.

Key Words
buckling; critical load; critical temperature; laminated composite plates

Fatima Zohra Kettaf: Département de Génie Mécanique, Faculté de Génie Mécanique,
Université des Sciences et de la Technologie d'Oran Mohamed-Boudiaf, Algérie;
Laboratoire des Matériaux et Systèmes Réactifs, Université de Sidi Bel Abbes, Faculté de Technologie,
BP 89 Cité Ben M'hidi 22000 Sidi Bel Abbes, Algérie
Mohamed Beguediab: Laboratoire des Matériaux et Systèmes Réactifs, Université de Sidi Bel Abbes, Faculté de Technologie,
BP 89 Cité Ben M'hidi 22000 Sidi Bel Abbes, Algérie
Soumia Benguediab: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of SidiBel Abbes, Algeria;
Université Dr Tahar Moulay, Faculté de Technologie, Département de Génie Civil et Hydraulique,
BP 138 Cité En-Nasr 20000 Saida, 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, Faculty of Technology, Civil Engineering Department, University of SidiBel Abbes, 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 Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan

This paper aims to propose a simplified method for predicting ultimate strength and ductility behavior of locally corroded steel box-section bridge piers. Firstly, the accuracy of the proposed 3-D elastoplastic finite element model for the steel piers subjected to a constant vertical load and cyclic lateral loading is verified by comparing the analytical results with test results. Then, a series of parametric study is carried out to investigate the effect of corrosion height ratio and corrosion thickness ratio of steel plates on the ultimate strength and ductility behavior of these piers. Finally, by establishing 2-D beam-column element models and comparing the calculation results with those of the 3-D models, correction coefficients for the ductility ratio and ultimate strength of 2-D beam-column element model under local corrosion are proposed. The research results indicate that there exists a most unfavorable corrosion height which makes the ductility ratio of steel piers the smallest. The ultimate strength of the steel piers will not have a distinct degradation when the corrosion height becomes larger than 0.5Ld. The correction coefficient formula for ductility ratio with respect to different aspect ratio of steel piers, and the linear relationship between correction strength coefficient and the corrosion thickness ratio are proposed. Correction coefficients for 2-D beam-column element model under the most unfavorable corrosion height are proven to have a rational accuracy, which provides a fast and simplified method to evaluate the ultimate strength and ductility behavior of such steel piers under local corrosion.

Key Words
correction coefficient; ductility behavior; local corrosion; stiffened steel box-section bridge piers; ultimate strength

Shengbin Gao: College of Civil Engineering, Shanghai Normal University, Shanghai, China
Yi Pang: Department of Civil Engineering, School of Naval Architecture, Ocean and Civil Engineering,
Shanghai Jiao Tong University, Shanghai, China
Hanbin Ge: Department of Civil Engineering, Meijo University, Nagoya, Japan

In this paper, stress analysis of a multi-walled hollow cylinder made from a functionally graded material (POLYMER) sandwiched between two piezoelectric layers is investigated. This system is subjected to internal and external pressure, a distributed temperature field due to steady state heat conduction with convective boundary condition, and a constant potential difference imposed on piezoelectric layers between its inner and outer surfaces or combination of these loadings. All mechanical and thermal properties except for the Poisson's ratio of Polymer layer are assumed to be power functions of the radial position. Using equilibrium equations, stress-strain relations and electromechanical coupling of piezoelectric layer, the constitutive differential equation in term of radial displacement is obtained. Considering electro-mechanical boundary conditions, this differential equation is analytically solved. The electro-thermo-mechanical stresses, electric potential and radial displacement distributions in three layers are obtained.

Key Words
electric potential; polymer; sandwiched cylinder; stress analysis

Yuhua Zhou: Advanced Manufacturing and Modern Equipment Institute, Jiangsu University, Zhenjiang 212000, Jiangsu, China
Mohamed Amine Khadimallah: Prince Sattam Bin Abdulaziz University, College of Engineering, Civil Engineering Department, Al-Kharj, 16273, Saudi Arabia;
Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Seyedmahmoodreza allahyari: Department of Mechanical Engineering, Dariun Branch, Islamic Azad University, Dariun, Iran
Amir behshad: Faculty of Industry and Mining, Yasouj University, Yasouj, Iran

This paper presents the parametric study on the strength and behaviour of CFS closed built-up battened columns. The CFS closed built-up battened column consists of two lipped channels placed face-to-face with a uniform spacing of battens. Finite element models are validated with the results of the test specimens available in the thesis of the first author. The parametric study on 176 cold-formed steel built-up column sections is extended by using the validated finite element modeling covering a wide range of global column slenderness, plate slenderness and yield stress. The numerical results from the parametric study are compared with the design strengths calculated by the European specifications (EN1993-1-3:2006) and AISI Specifications (AISI S100:2016). The comparison of parametric results with the design strength predictions has indicated the design guidelines of the specifications need improvement. The design strength predictions of the specifications are also assessed by conducting the reliability analysis. Therefore, the exiting design rules are modified to improve the accuracy of the design strength predictions for the CFS closed built-up battened columns subjected to the axial compression. Furthermore, the reliability of the proposed methods is confirmed by means of reliability analysis.

Key Words
axial strength; batten; built-up columns; channel sections; cold-formed steel; finite element analysis

S. Vijayanand: Department of Civil Engineering, Kongu Engineering College, Perundurai, Tamilnadu, India
M. Anbarasu: Department of Civil Engineering, Government College of Engineering, Salem, Tamilnadu, India

Load distribution has a great influence on the mechanical properties of composite pre-tightened multi-tooth connection. To obtain the load distribution mechanism of composite pre-tightened multi-tooth joints, the multi-tooth joints were studied by experimental and theoretical methods. First, an experimental study was conducted on three-tooth specimens with different tooth depths and tooth lengths, and the failure mode, bearing capacity and load distribution mechanism of the specimens were obtained. Then, based on the nonlinear constitutive of interlaminar shear, an analytical model for load distribution of composite pre-tightened multi-tooth joint was proposed to research the multi-tooth load distribution mechanism. Finally, the theoretical and experimental results were compared. The research showed: (1) The theoretical results of the multi-tooth load distribution ratio were in good agreement with that of the experimental results, the maximum error between the theoretical value and the experimental value of the three-tooth joint was 17.44%, and the minimum error was only 2.35%; (2) The load distribution ratio of composite pre-tightened multi-tooth was uneven, for three-tooth joints, the values of load distribution ratio from large to small were: the first tooth, the third tooth and the second tooth.; (3) Multi-tooth load distribution ratio changed with the change of external load. The change of load distribution ratio was obvious in the early stage of loading, and tended to be gentle in the later stage of loading.

Key Words
composite pre-tightened multi-tooth joint; load distribution ratio; shear nonlinearity

Yifeng Gao and Zhiqin Zhao: College of Field Engineering, Army Engineering University of PLA, Nanjing 210007, China
Fei Li and Lin Shi: Department of civil engineering, Chongqing Jiaotong University, Chongqing 401331, China
Qilin Zhao: College of Mechanical and Power Engineering, Nanjing University of Technology, Nanjing 211816, China
Jiangang Gao: Uint 32184 of PLA, Beijing 100072, China

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless steel unlipped channels as compression members are becoming popular. The advantages of using stainless steel as structural members are corrosion resistance and durability, compared with carbon steel. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (AS/NZS) standards for built-up carbon steel sections describes a modified slenderness approach, to consider the spacing of the intermediate fasteners. The AISI and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element (FE) analyses have been reported in the literature for such back-to-back cold-formed stainless steel unlipped channel section columns. This paper presents a numerical investigation on the behavior of back-to-back built-up cold-formed stainless steel unlipped channel section columns. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404, were considered. The effects of screw spacing on the axial strength of such built-up unlipped channels were investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines of carbon steel built-up sections in accordance with the AISI and AS/NZS. In total, 647 FE models were analyzed. From the results of the parametric study, it was found that the AISI and AS/NZS are conservative by around 14 to 20% for all three grades of stainless steel built-up unlipped channel section columns failed through global buckling. However, the AISI and AS/NZS carbon steel design rules can be un-conservative by around 8 to 13%, when they are used to calculate the axial capacity of those stainless steel built-up unlipped channels which are failed in local buckling.

Key Words
axial strength; back-to-back sections; built-up sections; cold-formed stainless steel; finite element analysis; screw spacing; unlipped channels

Krishanu Roy,Zhiyuan Fang and James B.P. Lim: Department of Civil and Environmental Engineering, The University of Auckland, Auckland, New Zealand
Hieng Ho Lau: Faculty of Engineering, Computing and Science, Swinburne University of Technology, Sarawak Campus, Kuching, Sarawak, Malaysia
Abdeliazim Mustafa Mohamed Ahmed: Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Saudi Arabia

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