Flexural buckling and design of press-braked rectangular hollow section steel long columns

Numerical modelling and fire design of stainless steel hollow section columns

With the growing demand for rectangular and square hollow steel sections in the last few decades, the cold roll forming process has become a widely acknowledged manufacturing method. However, the residual stress generated during the roll forming process is one of the primary concerns on roll‐formed products. One of the leading sources of residual stress is the severe plastic deformation that sheet metal experiences. It is well‐known that residual stress significantly affects the product's service life. In this regard, several researchers have conducted numerical and experimental investigations of residual stress distributions on roll‐formed steel sections. However, most of the studies found in the literature have been confined to the measurement of residual surface stresses. On the other hand, experimental studies conducted on fatigue and load‐carrying capacity of hollow structural steels have shown that there is indeed a simple relation between the through‐thickness residual stress distributions and mechanical properties of structures. Thus, this article employed a proper numerical modeling procedure using LS‐DYNA's finite element code to explore through‐thickness residual stress distributions generated during the roll forming process of rectangular and square hollow steel sections from different material grades. Moreover, a small‐scale parametric study was conducted to explore the effects of the partial heating roll forming method on through‐the‐thickness residual stress distributions.

Local–flexural interactive buckling of S690 high strength steel slender welded I-section columns: Testing, modelling and design

Fatigue improvements of cracked rectangular hollow section steel beams strengthened with CFRP plates

Based on the energy method, this article presents a theoretical study on the elastic local buckling of steel plates in rectangular concrete-filled steel tubular columns with binding bars subjected to eccentric compression. The formulas for elastic local buckling strength of the steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars are derived, assuming that the loaded edges are clamped and the unloaded edges of the steel plate are elastically restrained against rotation. Then, the experimental results are compared with these formulas, which exhibits good agreement. Subsequently, the formulas are used to study the elastic local buckling behavior of steel plates in rectangular concrete-filled steel tubular columns with binding bars under eccentric compression. It is found that the local buckling stress of steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars is significantly influenced by the stress gradient coefficient, width-to-thickness ratio, and the longitudinal spacing of binding bars. With the decrease of width–thickness ratios or the longitudinal spacing of binding bars or with the increase of the stress gradient coefficient, the local buckling stress increases. Furthermore, the influence of the longitudinal spacing of binding bar is more significant than the stress gradient coefficients. Finally, appropriate limitation for depth-to-thickness ratios ( D/ t), width-to-thickness ratios ( B/ t), and binding bar longitudinal spacing at various stress gradient coefficients ( α0) corresponding to different cross-sectional aspect ratios ( D/ B) are suggested for the design of rectangular concrete-filled steel tubular columns with binding bars under eccentric compression.

Experimental and numerical investigations of S700 high strength steel tubular section stub columns after exposure to elevated temperatures

In Standard CAN/CSA S16.1-M89, the contribution of the concrete to the flexural capacity of concrete-filled hollow structural sections is acknowledged as an alternative approach, but no method of assessing it is given. Preliminary studies had indicated that the concrete increased the ultimate moment capacity, the initial flexural stiffness, and the ductility, and delayed local buckling of the steel, thus enhancing the behaviour considerably. A series of four flexural tests on rectangular and square cold-formed hollow structural steel sections and twelve on concrete-filled sections were undertaken to assess the general behaviour of these composite sections. The test specimens were selected to examine the effects of different ratios of depth to width and therefore of the proportions of steel and concrete in compression, and of different values of shear span to depth as related to the transfer of forces from one to the other when no direct means is provided for this transfer. The tests showed that the ultimate flexural strength of the concrete-filled sections is increased by about 10–30% over that of the bare steel sections, depending on the relative proportions of steel and concrete. The stiffness is also enhanced. In all cases, slip between the steel and concrete was not detrimental, even though shear-span-to-depth ratios as low as 1 were tested. Models are developed to predict the flexural strength of the composite section. Fully plastic stress blocks with the concrete at its maximum strength are used. The models are in excellent agreement with the test results. Key words: composite beams, concrete-filled, flexural behaviour, hollow structural sections.

Tests on high-strength rectangular concrete-filled steel hollow section stub columns

Connecting a W‐shape beam to a hollow steel section (HSS) column using conventional bolts is difficult due to a lack of access inside the hollow section column to tighten the nut. Field welding the connection remains the common practice. The objective of this work is to propose a bolted moment connection for rectangular hollow steel columns using high‐strength blind bolts, and to evaluate such a connection in terms of its performance and its failure modes. An experimental program was conducted involving beam‐to‐column specimens subjected to beam tip monotonic loading. Moment‐rotation relationships of the tested connections were obtained while the response of the connection and its elements was investigated. Results show promising performance of such a connection type in terms of its stiffness, moment capacity, and ductility. Comparison is made with a similar connection using ordinary high‐strength A325 bolts. For the blind bolted connection, it was found that column flange thickness is a critical element that may govern the failure mode.

This paper investigates the flexural buckling behaviour and design of stainless steel circular, elliptical, square and rectangular hollow section (CHS, EHS, SHS and RHS) columns at elevated temperatures through numerical modelling. Shell finite element models are utilised to perform numerical parametric studies whereby benchmark structural performance data are generated. A large number of cold‐formed and hot‐rolled austenitic, duplex and ferritic stainless steel CHS, EHS, SHS and RHS columns at elevated temperatures are taken into account, considering various cross‐section and member slendernesses. Since the fire design provisions provided in the European fire design standard EN 1993‐1‐2 for stainless steel columns are largely based on those originally developed for carbon steel columns, they typically lead to rather inaccurate ultimate resistance predictions for stainless steel columns at elevated temperatures. To address this, in the present study, a new flexural buckling design method for stainless steel hollow section columns at elevated temperatures is put forward. The accuracy, safety and reliability of the proposed design method and the provisions in EN 1993‐1‐2 are assessed. It is observed that the proposed fire design method leads to more accurate, safe‐sided and reliable flexural buckling resistance predictions for stainless steel hollow section columns at elevated temperatures relative to the provisions in EN 1993‐1‐2.

The present construction industry requirement is more economical and speedy building the use of Light Gauge steel column infill with concrete that satisfies the excellent strength and improves ductility. Among the various infill materials, Nano SiO2 concrete is gaining attention in the composite column. The present work aims to investigate the comparative structural behavior of different Light gauge steel columns subjected to concentric loading. Light gauge steel rectangular hollow columns, plain and Nano SiO2 Concrete In-filled light gauge steel rectangular columns were considered for this research. The light gauge steel column dimension used for the experimental investigation is 80 mm × 40 mm size with 1.5 m length and 1.2 mm thickness. The ratio of width to thickness considered for the study is 66.67. Three different rectangular columns structural behavior such as load vs. axial shortening, deflection, strain characterization, and failure modes were studied from the experimental results under linear and non-linear stages. Further, the strength capacity obtained from the experiments is compared with theoretical strength derived from codes such as EC4, ACI, and BS5400. Results showed that a nano SiO2 in-filled concrete column enhances both strength and ductility, under axial load. The buckling resistance of nano SiO2 concrete in-filled steel columns was 4% higher than the plain concrete in-filled steel columns. The strength of plain concrete in-filled steel columns was 2.2 times more than the hollow steel column.

Buckling analysis of high strength stainless steel stiffened and unstiffened slender hollow section columns

Experimental and theoretical studies have been carried out to predict the fire resistance of rectangular hollow steel columns filled with bar-reinforced concrete. A mathematical model to calculate the temperatures, deformation and the fire resistance of the columns is presented. Calculated results are compared with those measured. The results indicate that the model is capable of predicting the fire resistance of rectangular hollow steel columns, filled with bar-reinforced concrete, with an accuracy that is adequate for practical purposes.

Design of cold-formed steel oval hollow section columns

Experimental and numerical investigations of S960 ultra-high strength steel slender welded I-section columns failing by local–flexural interactive buckling