A new approach to structural stainless steel design

Imperial Users onl

Deformation based design of steel and composite structural elements

[EN] Steel and composite structures are traditionally designed through strength based calculations. An alternative approach is to consider deformation capacity. Deformation based design enables a more accurate allowance to be made for the spread of plasticity and allows strain hardening to be considered in a systematic manner. Importantly, the level of deformation required by the structure at ultimate limit state to reach the required design capacity can also be assessed. In composite construction, deformation based design enables a more rigorous assessment to be made of the development of strength in the structural system taking due account of the compatibility between the constituent materials. In this paper, recent developments to the deformation based continuous strength method for steel and composite design are described. Comparisons of capacities obtained from experiments and numerical simulations with those predicted using the continuous strength method are presented and discussed. Recommendations for future work on this topic are also set out.Gardner, L.; Yun, X. (2018). Deformation based design of steel and composite structural elements. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 67-74. https://doi.org/10.4995/ASCCS2018.2018.7242OCS677

An investigation of the deformation and stresses in a cylindrical shell supported by a stiffener ring

The general bending theory equations for cylindrical shells were employed to determine the displacements and stresses due to gravity forces in cylindrical shells with the displacements at the shell support being specified

Numerical study of concrete-filled austenitic stainless steel CHS stub columns with high-strength steel inner tubes

[EN] A numerical modelling programme simulating the structural behaviour of concrete-filled double skin tubular (CFDST) stub columns with stainless steel outer tubes and high strength steel inner tubes is presented in this paper. The numerical model, which was developed using the finite element package ABAQUS, was initially validated against existing experimental results considering ultimate load, load-deflection histories and failure modes, with good agreement observed. Upon validation of the FE model, an extensive parametric study was undertaken whereby the cross-section slendernesses of the outer and inner tubes, the strength of the inner tube and the concrete grades were varied. These generated results together with the experimental data were then employed to assess the suitability of the design provisions of the European Standard EN 1994-1-1 and American Specification for concrete-filled tubes. Modifications to these design rules are also proposed, and a reduction factor (η) is suggested to account for the effective compressive strength in high strength concrete.Wang, F.; Young, B.; Gardner, L. (2018). Numerical study of concrete-filled austenitic stainless steel CHS stub columns with high-strength steel inner tubes. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 343-350. https://doi.org/10.4995/ASCCS2018.2018.8273OCS34335

The Continuous Strength Method

Many of the principal concepts that underpin current metallic structural design codes were developed on the basis of bilinear (elastic, perfectly-plastic) material behaviour; such material behaviour lends itself to the concept of section classification. The continuous strength method represents an alternative treatment to crosssection classification, which is based on a continuous relationship between slenderness and (inelastic) local buckling and a rational exploitation of strain hardening. The development and application of the continuous strength method to structural steel design is described herein. Materials that exhibit a high degree of nonlinearity and strain hardening, such as aluminium, stainless steel and some high-strength steels, fit less appropriately into the framework of cross-section classification, and generally benefit to a greater extent from the continuous strength method. The method provides better agreement with test results in comparison to existing design codes, and offers increases in member resistance and a reduction in scatter of the prediction. An additional benefit of the proposed approach is that cross-section deformation capacity is explicitly determined in the calculations, thus enabling a more sophisticated and informed assessment of ductility supply and demand. Further developments to the method are under way

Analysis of concrete-filled stainless steel tubular columns under combined fire and loading

[EN] In fire scenarios, concrete-filled stainless steel tubular (CFSST) columns undergo initial loading at ambient temperature, loading during the heating phase as the fire develops, loading during the cooling phase as the fire dies out and continual loading after the fire. CFSST columns may fail some points during this process under combined fire and loading. In this paper, the failure modes and corresponding working mechanism of CFSST columns subjected to an entire loading and fire history are investigated. Sequentially coupled thermal-stress analyses in ABAQUS are employed to establish the temperature field and structural response of the CFSST column. To improve the precision of the finite element (FE) model, the influence of moisture on the thermal conductivity and specific heat of concrete during both the heating and cooling phases is considered using subroutines. Existing fire and post-fire test data of CFSST columns are used to validate the FE models. Comparisons between predicted and test results confirm that the accuracy of the FE models is acceptable; the FE models are then extended to simulate a typical CFSST column subjected to the entire loading and fire history. The behaviour of the CFSST column is explained by analysis of the temperature distribution, load versus axial deformation curves and failure response.The research reported in the paper is part of the Project 51308539 supported by the National Natural Science Foundation of China. The financial support is highly appreciated.Tan, Q.; Gardner, L.; Han, L.; Song, D. (2018). Analysis of concrete-filled stainless steel tubular columns under combined fire and loading. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 825-833. https://doi.org/10.4995/ASCCS2018.2018.7206OCS82583

Saving Lives: a Collection of Poems

Englis

Member stability of stainless steel welded I-section beam-columns

A comprehensive experimental and numerical study is presented into the behaviour of stainless steel welded I-section beams-columns. Twenty test specimens were fabricated from grade 304 (EN 1.4301) austenitic and grade 2205 (EN 1.4406) duplex stainless steel plates – ten were tested under major axis bending plus compression and ten under minor axis bending plus compression. Material tensile coupon tests and geometric imperfection measurements were also conducted. Numerical models were developed, calibrated against the test results and subsequently employed in parametric studies considering a wider range of specimen geometries. Based on the obtained test and numerical results, the accuracy and reliability of existing design rules given in EN 1993-1-4 and AISC DG 27, as well as recent proposals, were assessed

Flexural Buckling of Hot-Finished High-Strength Steel SHS and RHS Columns

An experimental and numerical study of the flexural buckling behavior of hot-finished high-strength steel (HSS) square and rectangular hollow section (SHS and RHS, respectively) columns is described in this paper. A total of 30 hot-finished S460 and S690 hollow section column specimens have been tested in compression with pin-ended boundary conditions. Finite element (FE) models have been developed to replicate the experiments and employed in a subsequent parametric study considering a range of member geometries. Based on the test and FE results, the applicability of the current column design curves in European, North American, Chinese and Australian structural steel design standards to hot-finished HSS SHS and RHS columns has been verified by means of reliability analyses

Testing, numerical simulation and design of prestressed high strength steel arched trusses

The structural behaviour of prestressed high strength steel arched trusses is studied in this paper through experimentation and numerical modelling. Four 11 m span prestressed arched trusses fabricated from S460 hot finished square hollow section members were loaded vertically to failure. Three of the tested trusses were prestressed to different levels by means of a 7-wire strand cable housed within the bottom chord, while the fourth truss contained no cable and served as a control specimen. Each truss was loaded at five points coinciding with joint locations along its span, and the recorded load-deformation responses at each loading point are presented. Inclusion and prestressing of the cable was shown to delay yielding of the bottom chord and enhance the load carrying capacity of the trusses, which ultimately failed by either in-plane or out-of-plane buckling of the top chord. For the tested trusses, around 40% increases in structural resistance were achieved through the addition of the cable, though the self-weight was increased by only approximately 3%. In parallel with the experimental programme, a finite element model was developed and validated against the test results. Upon successful replication of the experimentally observed structural response of the trusses, parametric studies were conducted to investigate the effect of key parameters such as prestress level, material grade and the top chord cross-section on the overall structural response. Based on both the experimental and numerical results, design recommendations in the form of simple design checks to be performed for such systems are provided