This paper investigated tensile behaviours of S30408 at the Arctic low temperatures (T) of -80~20℃. 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 20℃. Test results revealed the ductile failure mode of stainless steel S30408 even at -80℃. The tensile stress-strain (𝜎-𝜀) curves of S30408 at ambient temperatures exhibited a long strain hardening plateau. Meanwhile, the low-temperature tensile 𝜎-𝜀 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.

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.

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 𝛽_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.

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.

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.

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 0.5L_d. 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.

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.

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.

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.

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.