Experimental study on the flexural response of UHPC beams encased high-strength section steel

In order to obtain high bearing capacity and good ductility simultaneously, a structural column with hybrid normal and high strength steel (HNHSS) welded box section has been developed. Residual stress is an important factor that can influence the behaviour of a structural member in steel structures. Accordingly, the magnitudes and distributions of residual stresses in HNHSS welded box sections were investigated experimentally using the sectioning method. In this study, the following four box sections were tested: one normal strength steel (NSS) section, one high strength steel (HSS) section, and two HNHSS sections. Based on the experimental data from previous studies and the test results of this study, the effects of the width-to-thickness ratio of plate, yield strength of plate, and the plate thickness of the residual stresses of welded box sections were investigated in detail. A unified residual stress model for NSS, HSS and HNHSS welded box sections was proposed, and the corresponding simplified prediction equations for the maximum tensile residual stress ratio (σrt/fy) and average compressive residual stress ratio (σrc/fy) in the model were quantitatively established. The predicted magnitudes and distributions of residual stresses for four tested sections in this study by using the proposed residual stress model were compared with the experimental results, and the feasibility of this proposed model was shown to be in good agreement.

Mechanical properties of very high strength steel at elevated temperatures

For cyclically loaded structures, fatigue design becomes one of the important design criteria. The state of art shows that with modification of the conventional structural design methodology, the use of very high strength steels may have a positive effect on fatigue strength of welded connections. However, there is little known about the repair of fatigue cracks in welded connections made of very high strength steels. In this study, the fatigue strength of the repaired base material and repaired fatigue damaged V-shape welded connections made of very high strength steels is investigated. This thesis consists of four parts. In Part I, the emphasis was put on the effects of the material imperfections on the fatigue strength of materials and this part consists of an extensive literature study and a microscopic examination of the fracture surfaces of the base material of very high strength steels. Part II presents a literature survey on the fatigue crack repair methods and the results of the experimental programme of the current study. The experimental programme comprises fatigue tests on the repaired base material and repaired V-shape welded connections made of very high strength steels. The V-shape welded specimens were made of rolled and cast steel plates. In Part III, fatigue strength prediction models were evaluated and a comparison was made between the fatigue strength curves from the prediction models and the fatigue strength curves of the test results. In the last part, conclusions and recommendations from the study are presented. The analysis of test results revealed that the fatigue strength of fatigue damaged V-shape welded connections made of very high strength steels can be recovered by an appropriate repair procedure.

- An experimental study was performed for thin-walled recta ngular concrete-filled tubular (CFT) columns. The present study mainly focused on evaluation of the axial load-carrying capacity of concrete-filled tubular columns using high-strength steel and slender section. The test parameters were width-to-thickness ratio, concrete strength, steel yield strength, and the use of stiffeners. Five specimens were tested under monotonic axial loading. Although elastic local buckling occurred in the slender- section specimens with high-strength steel, the specimens exhibited considerable post-buckling reserve. The test results also satisfied the predictions of a current design code. The specimens strengthened with vertical stiffeners exhibited improved strength and ductility when compared with the un-stiffened specimens. Keywords - Rectangular CFT column, High-strength steel, Slender section, Concentric axial loading, StiffenerNote.-Discussion open until October 31, 2015. This manuscript for this paper was submitted for review and possible publication on May 18, 2014; revised October 25, 2014; approved on February 5, 2015.Copyright ⓒ 2015 by Korean Society of Steel Construction

Strength enhancement of high strength steel beams by engineered cementitious composites encasement

Experimental study on fracture toughness of quenched and tempered and TMCP high strength steels

Post-fire performance of very high strength steel S960

Experimental and numerical study on the behavior of axially compressed high strength steel columns with H-section

Experimental study on high-strength Q460 steel extended end-plate connections at elevated temperatures

Experimental study on local buckling of high-strength Q960 steel columns at elevated temperatures

This article presents a new form of fibre-reinforced polymer-concrete-steel hybrid columns and demonstrates some of its expected advantages using results from an experimental study. These columns consist of a concrete-filled fibre-reinforced polymer tube that is internally reinforced with a high-strength steel tube and are referred to as hybrid double-tube concrete columns. The three components in hybrid double-tube concrete columns (i.e. the external fibre-reinforced polymer tube, the concrete infill and the internal high-strength steel tube) are combined in an optimal manner to deliver excellent short- and long-term performance. The experimental study included axial compression tests on eight hybrid double-tube concrete columns with a glass fibre–reinforced polymer external tube covering different glass fibre–reinforced polymer tube thicknesses and diameters as well as different high-strength steel tube diameters. The experimental results show that in hybrid double-tube concrete columns, the concrete is well confined by both the fibre-reinforced polymer tube and the high-strength steel tube, and the buckling of the high-strength steel tube is suppressed so that its high material strength can be effectively utilized, leading to excellent column performance. Due to the high yield stress of high-strength steel, the hoop stress developed to confine the core concrete is much higher than can be derived from a normal-strength steel tube, giving the use of high-strength steel in double-tube concrete columns an additional advantage.

In this paper, high-strength steels (yield strength greater than 900MPa) paired with nylon sliders were tested on static friction coefficient. The test samples are in disc- shaped friction pair structure. A specific axial load is applied to the friction pair to produce a certain degree of axial pressure. The test equipment selects friction material testing machine. With the initial establishment of a nylon - high- strength steel friction performance test database, and systematic in-depth analysis of the influence mechanism of the inter-material friction performance by load, material and lubrication method. The friction coefficient decreases when the stress increases. The friction coefficient of PAM toughened nylon and POM reinforced nylon with high strength steel shows small changes along with the stress changes, while the friction coefficient of MC nylon with high strength steel shows larger changes along with the stress changes. Providing accurate data support for optimal design of the friction pair structure and material selection as well as the force calculation of friction pairs in contact with hazardous areas.

Experimental study on seismic behaviour of cover-plate joints in high strength steel frames

This paper presents the experimental studies of the flexural behavior of steel-concrete composite beams. Herein, steel-concrete composite beams were constructed with a welded steel I section beam and concrete slab with different material strength. Four simply supported composite beams subjected to two-point concentrated loads were tested and compared to investigate the effect of high strength engineering materials on the overall flexural response, including failure modes, load deflection behavior, strain response and interface slip. The experimental results show that the moment capacity of composite beams has been improved effectively when high-strength steel and concrete are used. Comparisons of the ultimate flexural strength of beams tested are then made with the calculated results according to the methods specified in guideline Eurocode 4. The ultimate flexural strength based on current codes may be slightly unconservative for predicating the moment capacity of composite beams with high-strength steel or concrete.

Buckling behaviour of high-strength retrofitted steel sections manufactured through post heat-treatment processes